Citation: Schöne, N.; Heinz, B.
Semi-Systematic Literature Review
on the Contribution of Hydrogen to
Universal Access to Energy in the
Rationale of Sustainable
Development Goal Target 7.1.
Energies 2023,16, 1658. https://
doi.org/10.3390/en16041658
Academic Editor: Muhammad Aziz
Received: 12 January 2023
Revised: 31 January 2023
Accepted: 2 February 2023
Published: 7 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
energies
Review
Semi-Systematic Literature Review on the Contribution of
Hydrogen to Universal Access to Energy in the Rationale of
Sustainable Development Goal Target 7.1
Nikolas Schöne 1,* and Boris Heinz 1,2
1Department of Community Energy and Adaptation to Climate Change, Technische Universität Berlin,
Ackerstr. 76, 13355 Berlin, Germany
2Hudara gGmbH, Rollbergstr. 26, 12053 Berlin, Germany
*Correspondence: [email protected]
Abstract:
As part of the United Nations’ (UN) Sustainable Development Goal 7 (SDG7), SDG target
7.1 recognizes universal electrification and the provision of clean cooking fuel as two fundamental
challenges for global society. Faltering progress toward SDG target 7.1 calls for innovative technolo-
gies to stimulate advancements. Hydrogen has been proposed as a versatile energy carrier to be
applied in both pillars of SDG target 7.1: electrification and clean cooking. This paper conducts a
semi-systematic literature review to provide the status quo of research on the application of hydrogen
in the rationale of SDG 7.1, covering the technical integration pathways, as well as the key economic,
environmental, and social aspects of its use. We identify decisive factors for the future development
of hydrogen use in the rationale of SDG target 7.1 and, by complementing our analysis with insights
from the related literature, propose future avenues of research. The literature on electrification
proposes that hydrogen can serve as a backup power supply in rural off-grid communities. While
common electrification efforts aim to supply appliances that use lower amounts of electricity, a
hydrogen-based power supply can satisfy appliances with higher power demands including electric
cook stoves, while simultaneously supporting clean cooking efforts. Alternatively, with the exclusive
aim of stimulating clean cooking, hydrogen is proposed to be used as a clean cooking fuel via direct
combustion in distribution and utilization infrastructures analogous to Liquid Petroleum Gas (LPG).
While expected economic and technical developments are seen as likely to render hydrogen technolo-
gies economically competitive with conventional fossil fuels in the future, the potential of renewably
produced hydrogen usage to reduce climate-change impacts and point-of-use emissions is already
evident today. Social benefits are likely when meeting essential safety standards, as a hydrogen-based
power supply offers service on a high tier that might overachieve SDG 7.1 ambitions, while hydrogen
cooking via combustion fits into the existing social habits of LPG users. However, the literature lacks
clear evidence on the social impact of hydrogen usage. Impact assessments of demonstration projects
are required to fill this research gap.
Keywords:
Sustainable Development Goal 7; electrification; clean cooking; hydrogen; semi-systematic
review
1. Introduction
1.1. Framework and Concept
The United Nation’s (UN) Sustainable Development Goals (SDGs) provide clear
guidance to global society on pressing challenges for sustainable development until 2030.
Energy is recognized as one distinct challenge in SDG 7. However, SDG 7 is mutually
interlinked with many other SDGs and is a crucial factor to success in other dimensions
of development [
1
]. In fact, the rudimentary access to energy is indispensable for any
kind of human development, including economic and social development [
2
]. Accordingly,
the very first and fundamental target of SDG 7, called SDG 7.1, is to ensure universal
Energies 2023,16, 1658. https://doi.org/10.3390/en16041658 https://www.mdpi.com/journal/energies
Energies 2023,16, 1658 2 of 42
access to affordable, reliable, and modern energy services for everyone [
3
]. To define the
goal of “energy,” two dedicated indicators are introduced to measure progress within the
target. SDG indicator 7.1.1 (SDG 7.1.1) determines the proportion of the population (%)
with a minimum access to electricity of 100 kWh per year on a household level [
4
]. The
complementary indicator SDG indicator 7.1.2 (SDG 7.1.2) assesses the proportion of the
population (%) that primarily relies on clean fuels and technology for cooking, heating, and
lighting [
5
]. By referencing a minimum amount of energy, these indicators set the lowest
standard that must be met by the end of the SDG period in 2030.
However, in 2022, the required pace of the annual progression in electrification and
provision with clean cooking fuels in order to achieve the SDG 7.1 target of universal
access to energy by 2030 has not been met. In 2020, 733 million people lacked access to
electricity [
6
]. The pace of annual growth toward access eventually slowed down from 0.8
percentage points in 2010–2018 to 0.5 percentage points in 2018–2020. This faltering progress
is mainly explained by the complexity of reaching the remaining unserved populations,
who are mostly located in rural regions, and the potential impacts of COVID-19 [
6
]. In
parallel, recent improvements in universal access to clean cooking have been outpaced by
population growth, particularly in sub-Saharan Africa (SSA). On a global scale, 2.5 billion
people lacked access to clean cooking in 2022 [
7
]. In many regions, this progress has
stagnated for years.
In the face of these significant challenges in the time remaining to achieve the SDGs,
new and disruptive technologies could provide the impetus needed to overcome these
hurdles [
8
]. Hydrogen-based technologies are one example of innovative technologies that
have recently polarized the discussion [
9
]. Hydrogen is a multi-usable energy carrier with
various proven possible applications. Hydrogen in its pure form is used as a substance
in industrial production processes, for instance as a chemical reduction agent in steel and
other metal industries [
10
], or as a base substance for fertilizer production [
9
,
11
]. However,
in energy applications, hydrogen is proposed to be applied in power supply, heating, and
mobility [9], of which the first two apply to the challenges of SDG 7.1 [12].
As a concept, the process of enabling a power supply based on hydrogen is called
power-to-hydrogen-to-power (P2H2P). In P2H2P electricity, which, to meet global cli-
mate change mitigation targets must necessarily generated by renewable electricity, is
used to split water in its components hydrogen and oxygen. This concept—called water
electrolysis—has been known for over a century [
11
]. Several electrolyzer (EL) technologies
have been developed to a commercial scale. Table 1summarizes the main characteristics
of the most prominent electrolyzer technologies, including alkaline electrolysis (AEL),
anion exchange membrane electrolysis (AEMEL), polymer membrane electrolysis (PEMEL),
and solid-oxide electrolysis (SOEL). A comprehensive review of recent advances in water
electrolysis is given in [13].
Table 1.
Technical characteristics and selected parameters of AEL, AEMEL, PEMEL, and SOEL
technology according to the recent literature [
13
]. If not specifically indicated, the values indicate
representative values in line with [13].
Parameter Unit AEL AEMEL PEMEL SOEL
Electrolyte / 10–30% KOH
Quaternary ammonia
polysulfide or dilute caustic
solution [14]
Perfluoro sulfonic acid
Ionic conductor consisting
of ZrO2doped with 8 mol
% Y2O3[14]
Anode reaction [13] / 2OH−→1
2O2+ H2O + 2e−4OH−→2H2O+O2+ 4e−H2O→1
2O2+ 2H++ 2e−H2O + 2e−→H2+ O2−
Cathode reaction [13] / 2H2O + 2e−→H2+ 2OH−4H2O + 4e−→2H2+ 4OH−2H++ 2e−→H2O2−→1
2O2+ 2e−
Operating temperature ◦C 70–90 40–60 50–80 700–900
Operating pressure bar <30 <35 <70 <10
Catalyst material [15] / Ni-coated perforated
stainless steel
High surface area nickel or
NiFeCo alloys
Platinum groups/Iridium
oxide Perovskite-type/Ni/YSZ
Efficiency 1(System,
LHV) % 51–60 70–75 46–60 76–81
Energies 2023,16, 1658 3 of 42
Table 1. Cont.
Parameter Unit AEL AEMEL PEMEL SOEL
Start-up time
(cold 2/warm) /1–2 h
1–5 min
<20 min
<<20 min
5–10 min
<10 s
Hours
15 min
Minimum part load % 20 5 0–5 /
CAPEX USD/kW 500–1000 / 700–1400 <2000
1
Notably, system efficiency of PEMEL is known to be a non-linear function of the power input. Included
values may refer to the efficiency reference power depending on the source consulted.
2
Defined below 50
◦
C
temperature.
Produced hydrogen can be stored in many ways, including liquefied hydrogen, cryo-
genic hydrogen, hydrogen bound in metal hydrides, and hydrogen in gaseous form [
16
].
Compressed gaseous hydrogen storage is the most popular storage form today because
of low processing requirements and costs [
16
]. In gaseous form, stored hydrogen can
be re-electrified by a fuel cell (FC) in the opposite reaction to water electrolysis. Table 2
provides an overview of selected parameters of commercially available FC technologies.
Akinyele et al. summarize the status quo of FCs and describe the system integration in
complex energy systems for remote power systems [
17
]. Arsalis et al. present a recent
update on the integration of regenerative FCs in microgrid systems [18].
Table 2.
Technical characteristics and selected parameters of AFC, PAFC, PEMFC, and SOFC technol-
ogy according to the recent literature [
9
,
17
,
19
]. Abbreviations: AFC = alkaline fuel cell; PAFC = phos-
phoric acid fuel cell; PEMFC = polymer electrolyte membrane fuel cell; SOFC = solid oxide fuel cell.
If not specifically indicated, the values indicate representative values in line with [9,17,19].
Parameter Unit AFC PAFC PEMFC SOFC
Electrolyte [18] / 10–30% KOH solution in a
matrix
Liquid phosphoric acid
soaked in a matrix
Solid organic polymer
Perfluoro sulfonic acid Yttria stabilized zirconia
Anode reaction [16] / H2+ 2OH−→2H2O + 2e−H2→2H++ 2e−H2→2H++ 2e−H2+ O2−→H2O + 2e−
Cathode reaction [16] / 0.5O2+ H2O + 2e−→2OH−0.5O2+ 2H++ 2e−→H2O 0.5O2+ 2H++ 2e−→H2O 0.5O2+ 2e−→O2−
Operating temperature ◦C 60–120 150–220 50–100 800–1,000
Efficiency (System,
LHV) % 45–60 40–55 45–65 35–40
CAPEX USD/kW 700–1800 4000–5000 1400–4000 1500–8000
P2H2P has been established in the power sector for different purposes. These include
flexible power generation, long-term and large-scale energy storage, uninterrupted power
supply schemes, as well as backup and off-grid power supplies [
20
]. In the latter application,
P2H2P poses an alternative to predominantly diesel-based electricity supplies in off-grid
areas. Historically, P2H2P in such settings was used to supply backup power to critical
infrastructure, especially mobile telecommunication stations. In such crucial and sensitive-
to-black-out infrastructure, the high costs of P2H2P are justifiable by the high reliability
of the power supply and the long-term storability of hydrogen [
21
]. However, with
declining costs, residential applications are becoming increasingly relevant for P2H2P. Pilot
projects of the last decades have proven P2H2P’s ability to serve power to residential
and village loads in Norway, Japan, Sweden, Germany, Switzerland, the USA, and the
UK [
21
]. Reflecting on the success of such projects, researchers have proposed P2H2P use
for domestic electrification in countries with low electrification rates as well [12].
More recently, the utilization of hydrogen in residential applications for heating
and cooking purposes has been suggested [
20
]. While the use of waste-heat released by
FCs might serve for low-temperature heating, a substitution of natural gas and methane
and direct combustion of hydrogen is discussed for heating and cooking purposes [
20
].
Especially in Europe and Japan, countries that rely on imports of fossil fuels for residential
heating, the replacement of natural gas with hydrogen is proposed and investigated.
While in such settings a well-developed infrastructure, i.e., central import hubs, pipelines,
and standardized equipment, exists, valid arguments speak in favor of a transfer of the
discussion to less-developed settings. The possible analogy to draw to the replacement
of natural gas in well-developed infrastructures is the replacement of liquid petroleum
Energies 2023,16, 1658 4 of 42
gas (LPG) in less-developed infrastructures; LPG is already established and foreseen to
become even more widely used as a cooking fuel in countries lagging behind in access to
clean cooking. Reflecting on the much lower emissions of pollutants during combustion
compared to conventional fuels, along with recent success stories of LPG, many African
governments are promoting LPG as a clean cooking fuel for the next decade [
6
]. However,
as LPG is still an exhaustible and fossil fuel, it is only seen as a transitional fuel to use until
a renewable alternative is available [
22
]. Since hydrogen has very similar physical and
chemical properties to LPG, it seems logical to discuss hydrogen produced from renewable
energies as a future substitute for LPG.
1.2. Previous Literature
Reflecting on the properties and potential utilization, the application of hydrogen in
energy services in the rationale of SDG 7.1 was proposed in the previous literature. AbouSe-
ada and Hatem [
23
] review the prospects of green hydrogen-production potential and
usage in Africa. The authors present a status quo of initiatives, technologies, and policies.
However, the authors focus on large-scale applications, i.e., in the chemical industry and
the steel and iron industry. The applications of hydrogen in off-grid electrification and
on-grid use for stabilization of instable power grids are proposed vaguely [
12
]. Mukelabai
et al. reflect on how and what role hydrogen can play in the African energy landscape. The
authors essentially point to exporting green hydrogen (that is, produced from renewable
energy) to propel Africa
´
s economy, and the use of hydrogen to produce fertilizer at a large
scale to meet the food demands of Africa
´
s fast-growing population. Grid-load balanc-
ing is proposed as an application in the power sector, while the potential use as a clean
cooking fuel is seen to require the development of business, social, and techno-economic
models [
24
]. The authors follow their previous research and conduct a political, economic,
social, legal, and environmental (PESTLE) analysis to evaluate the deciding factors in the
adoption of hydrogen in Africa. One critical factor to consider would be the electrification
of the population without access to electricity, which should be a priority before producing
hydrogen for export. Further, the authors point to the tremendous air pollution caused
by and harm to the health of users who rely on traditional fuels for cooking. Therefore,
the authors call hydrogen technology developers to consider the purpose of clean cooking.
Interestingly, the authors find countries with a lack of clean access to electricity and cooking
to be in a better position to attract hydrogen technology developers than better situated
countries. This statement is justified in referring to the common thought of the hydrogen
economy being an egg and chicken problem; thus, satisfying local market needs first might
be a strong foundation to further expand the hydrogen technology market in a country [
25
].
While the aforementioned papers only broadly propose hydrogen for electrification and
clean cooking purposes in Africa but do not provide details as to its application, Maestre
et al. implicitly showcase examples of how a hydrogen-based power supply could improve
electrification efforts in a review of stationary applications of renewable hydrogen-based
power systems [
13
]. The extensive review includes a comprehensive overview and com-
parison of techno-economic analysis of off-grid power supply systems, comparing key
technical and economic figures. However, including a wide geographic scope, the paper
does not specifically address challenges occurring in the SDG 7.1 rationale. Further, the
paper does not include the application of hydrogen for clean cooking purposes.
1.3. Ambition and Contribution to Research
The review of the previous literature shows an absence of an organized analysis and
concise presentation of how hydrogen may be applied in the rationale of SDG 7.1. This
paper aims to close this gap by detecting relevant research contributions on hydrogen
applications for electrification and clean cooking purposes. Guided by the principles of a
semi-systematic literature review, this paper presents evidence from previous research and
identifies applied methodologies, research foci, and proposed energy-system architectures.
Relevant publications are synthetized and discussed to identify their relevance for future
Energies 2023,16, 1658 5 of 42
work. We supplement identified topics with context-related discussions from state-of-the-
art literature. The specific research questions of this paper are:
•
What are the predominantly proposed technical integration pathways of hydrogen for
electrification and clean cooking and respective energy-system topologies?
•What are the current challenges impairing studies on the use of hydrogen in electrifi-
cation or clean cooking?
•What are potential chances for the market entry of hydrogen in the Global South?
•
What are the lessons learned and the way forward for studies of hydrogen application
in contributing to SDG 7.1?
•
Which research methods have been used in the field, and did they change over time?
The findings of this review will be useful to researchers, policymakers and regulators,
NGOs, international organizations, and many other stakeholders involved in SDG 7.1. We
propose a research agenda to accelerate and streamline future work in the field.
The outline of this paper reads as follows: Section 2describes the methodology
applied during our review. Section 3presents quantitative results of a meta-analysis, before
qualitatively analyzing and discussing significant contributions in technical, economic,
environmental, and social aspects. We discuss the findings in Section 4.
2. Materials and Methods
Figure 1illustrates the workflow applied in our paper. To guide our analysis, we adopt
the principles of a semi-systematic literature review. The semi-systemic literature review
is a proven concept to apply when aiming to share an overview of a thematic area, while
including both quantitative and qualitative research articles [
26
]. The concept is useful
when being confronted with heterogenous studies that are differentially conceptualized
and developed by various groups of researchers within diverse disciplines, and a full
systematic review process is not foreseen [
27
]. It differs from a systematic review, which
aims to identify empirical evidence that reflects specified inclusion criteria to answer
a specific research question—often but not always using a statistical meta-analysis to
identify patterns that appear in different studies on the same topic [
27
]. While, in order
to assess the quality of findings from different studies, qualitative systematic reviews
have been developed [
28
], semi-systematic reviews are useful to capture all potentially
relevant research traditions that have implications for the studied topic and to synthesize
these using meta-narratives instead of by measuring effect size [
26
]. Semi-systematic
reviews include research articles with more broad research questions as well, which are
useful in identifying themes in the literature and developing a research agenda [
27
]. To
define a transparent and replicable review, we apply the Search, Appraisal, Synthesis,
and Analysis (SASA) methodology, which guides and gives protocols for the review. The
SASA methodology guarantees methodological accuracy, systematization, exhaustiveness,
and reproducibility [
27
]. To further improve the quality of our work, we lean on the
guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses
(PRISMA) evidence-based minimum set of items for reporting in systematic reviews and
meta-analyses [
29
]. A flowchart summarizing the PRISMA key figures of our search is
included in the Appendix A(Figure A1). In the following, we will describe the most
important decisions made for each working step of SASA.
Energies 2023,16, 1658 6 of 42
Energies 2023, 16, x FOR PEER REVIEW 6 of 38
Figure 1. Workflow applied in the present paper, including Search–Appraisal–Synthesis–Analysis
approach.
2.1. Search
To initialize the search for relevant papers in a structured manner, we screened two
internationally recognized databases according to predefined search strings. The selected
databases were the ScienceDirect [30] and the Multidisciplinary Digital Publishing Insti-
tute (MDPI) databases (https://www.mdpi.com). ScienceDirect is an online collection of
published scientific research operated by the publisher Elsevier, and it is an online aca-
demic citation index at the same time. The MDPI database is a collection of 290 diverse,
peer-reviewed, open-access journals operated by MDPI. We screened a wide body of re-
lated work to establish a set of search strings to be applied to the automatic filter in each
of the databases. The search strings consisted of the word “hydrogen” and the keywords
“Sustainable Development Goal 7,” “Global South,” “developing countries,” “electrifica-
tion,” “clean cooking.” “cooking,” “off-grid,” “off grid,” “mini-grid,” “minigrid,” and
“rural.” In ScienceDirect, the combination of the search strings was entered in the ad-
vanced search field “title, abstract, keywords.” In the MDPI database, the search strings
were applied to the general search field. No further filters were applied (such as “subject”)
to avoid missing relevant work. The search was conducted in the time span between 6
July 2022 and 30 October 2022. All articles included in the search were published in peer-
reviewed journals by no later than June 2022 (31 June 2022). The databank search initial-
ized the review process, which continued with “snowballing” as described in Section 2.2.
2.2. Appraisal
During the appraisal stage, we selected studies eligible for our review by applying a
set of inclusion/exclusion criteria to the articles:
1. Search string: Papers were only considered when including the predefined keywords
as a whole or at least in combination in title, keywords, or abstract.
Figure 1.
Workflow applied in the present paper, including Search–Appraisal–Synthesis–Analysis
approach.
2.1. Search
To initialize the search for relevant papers in a structured manner, we screened two
internationally recognized databases according to predefined search strings. The selected
databases were the ScienceDirect [
30
] and the Multidisciplinary Digital Publishing Institute
(MDPI) databases (https://www.mdpi.com). ScienceDirect is an online collection of pub-
lished scientific research operated by the publisher Elsevier, and it is an online academic
citation index at the same time. The MDPI database is a collection of 290 diverse, peer-
reviewed, open-access journals operated by MDPI. We screened a wide body of related
work to establish a set of search strings to be applied to the automatic filter in each of the
databases. The search strings consisted of the word “hydrogen” and the keywords “Sus-
tainable Development Goal 7,” “Global South,” “developing countries,” “electrification,”
“clean cooking.” “cooking,” “off-grid,” “off grid,” “mini-grid,” “minigrid,” and “rural.” In
ScienceDirect, the combination of the search strings was entered in the advanced search
field “title, abstract, keywords.” In the MDPI database, the search strings were applied to
the general search field. No further filters were applied (such as “subject”) to avoid missing
relevant work. The search was conducted in the time span between 6 July 2022 and 30
October 2022. All articles included in the search were published in peer-reviewed journals
by no later than June 2022 (31 June 2022). The databank search initialized the review
process, which continued with “snowballing” as described in Section 2.2.
Energies 2023,16, 1658 7 of 42
2.2. Appraisal
During the appraisal stage, we selected studies eligible for our review by applying a
set of inclusion/exclusion criteria to the articles:
1.
Search string: Papers were only considered when including the predefined keywords
as a whole or at least in combination in title, keywords, or abstract.
2.
Type of paper: Only original research papers were considered. This essentially
excluded reviews, patent analyses, book chapters, and proceedings.
3. Language: Only papers written in English were considered.
4.
Year: To limit the scope of the databank search, we filtered for papers published (print
version) from the beginning of the SDG period in 2015 until July 2022 (31 June 2022).
5.
Geopolitical scope: Given the hotspots of deficit in SDG 7.1.1 and SDG 7.1.2 identified
by the most recent SDG 7 progress report [
6
], we only consider papers essentially
focusing on countries in the Global South. Notably, the term Global South is more
than a geographical denotation of a geographical region. The terminus rather focuses
on geopolitical relations of power, therefore essentially excluding regions in Europe
and North America, but broadly including the regions of Latin America, Asia, Africa,
and Oceania [
31
]. We relied on the United Nations’ Finance Center for South–South
Cooperation
´
s list of countries accounting for the Global South [
32
]. As of 2022, the
list comprises 78 countries (including China).
6.
Rationale: Articles included in our review had to be in alignment with the rationale
of SDG 7.1.1 or SDG 7.1.2. This implies that the articles present work that directly
contributes to increasing the share of people having access to electricity or clean
cooking, respectively, on a household level. Notably, this excludes applications
providing energy services to buildings or infrastructure, which that do not primarily
serve as housing for people. Examples are telecommunication stations [
33
], public
buildings [
34
], or hospitals [
35
]. Articles proposing an alternative energy supply to an
existing, reliable, and clean status quo, such as modernization of energy services for
urban buildings [
36
], were excluded. Further, mobility applications do not meet the
rationale of SDG 7.1.
7.
Specificity: Our review only includes articles that specifically address the utilization
of hydrogen at the end-use. This excludes work that focuses on the production of
hydrogen but insufficiently describes the foreseen utilization (e.g., [
37
]), and work
introducing hydrogen as a broad concept only (i.e., the concept of a “hydrogen
economy” such as in [38]).
8.
Renewable hydrogen: SDG 7.1.1 does not specify the source of electricity supply to
increase the share of the population with access to electricity. McCollum et al. [
1
]
thereby detected negative correlations between targets and indicators of SDG 7, e.g.,
when electrification is enhanced via diesel generators (DGs). However, to not harm
other targets of the SDGs, especially SDG 7.2 (increase the share of renewables), we
only considered renewable hydrogen as eligible for our review. We further only
considered the utilization of hydrogen in its pure form, but not hydrogen-rich fuels
such as biomethane.
Papers meeting the criteria 1–4 were considered for abstract reading. If not excluded at
this stage, the main body of the papers was studied to check for consistency with criteria 5–
8. We documented the first occurring exclusion criterion only. For example, a paper entitled
“Comparative assessment of zero emission electric and hydrogen buses in Australia” [
39
]
was excluded for violating criterion 7 (rationale), even though it obviously as well violates
the exclusion criterion 5 (Geopolitical scope).
Following the data bank search, we applied backward snowballing to detect more
relevant literature. During snowballing, we consulted the reference sections of selected
papers and searched in the citations for potentially eligible work [
40
]. Therefore, we
screened the references according to our previously defined basic criteria. However, we
excluded criterion 4 (year), as this was initially defined to limit the scope of the data bank
search only.
Energies 2023,16, 1658 8 of 42
2.3. Synthesis
The synthesis step consisted of both extraction and classification of relevant data from
selected papers to derive knowledge and conclusions. Documentation and categorization
were performed in Microsoft Excel. The general information (variables of interest) of the
articles includes year of publication, journal, geographical location of the research institute
of the corresponding author, analysis method, software used, sustainability dimension
covered, hydrogen application, description of energy system, and country or region where
the study was conducted.
We distinguished seven discrete methods for categorization, while a single paper may
combine several of these methods:
•
Geospatial information system (GIS) model: Formalized representation of a real system
that attempts to emulate combined processes of acquiring and using energy to satisfy
the energy demands of a given area over an extended period of time [41].
•
Life-cycle assessment (LCA): Assessment of the environmental impact (e.g., damages
to human health, ecosystems, or resources) through all the life-cycle stages of an
energy system or energy technology [42].
•
Experiment: The setup of a physical experiment, i.e., manipulation of variables to
establish cause-and-effect relationships.
•
Optimization model: A mathematical attempt to determine the maximum or minimum
value of a complex objective function that serves as a definite recommendation for the
energy system.
•
Simulation model: A mathematical attempt to determine an energy system
´
s response
to different inputs, while—in contrast to optimization—not defining a clear recom-
mendation.
•
Multi-criteria decision analysis (MCDA): MCDA is an operational evaluation and
decision-support approach comparing the performance of various energy system or
energy technology options along multiple criteria. In contrast to the multi-objective
optimization included in the method category “optimization model,” the MCDA
method may include qualitative aspects, such as risks, available human resources, or
political drivers [42].
•
Rigorous analysis: A procedure or test following a strict methodology but not included
in the above-mentioned methods.
Regarding the dimensions of sustainability covered by a paper we distinguished in
four dimensions:
•
Technical dimension: This dimension encompasses all the technical characteristics that
describe or evaluate a system, its use of resources, and its ability to meet the intended
final uses [43,44].
•
Environmental dimension: This dimension includes environmental impacts on the
local or aggregated level. We further include effects on human health in this dimen-
sion [45].
•
Economic dimension: The economic dimension covers any economic assessment on
the individual, system, or aggregated level.
•
Social dimension: This dimension covers the impact on, or interaction with, people,
including societal structures and ethical aspects.
A dimension is seen as included when aspects of it are explicitly mentioned in the text
and not only as an underlying facet.
2.4. Analysis
Our analysis includes both quantitative and qualitative evaluation. For quantitative
analysis, records identified, and associated variables of interest (see Section 2.3) were
processed in Microsoft Excel. The data was aggregated and visualized in the same software.
Qualitative evaluation included the study and analysis of the identified papers. We focused
on the research questions, methods applied, results answering the research aim, and
Energies 2023,16, 1658 9 of 42
suggestions for future work. We compared papers within each application of SDG 7.1 to
assess the relative contribution of a paper to the general status of research in the respective
field of research.
3. Results and Discussion
In this section, we present the results from our literature review on hydrogen applica-
tions in the rationale of SDG 7.1. We show quantitative results of the variables of interest
defined in Section 3, qualitatively assess relevant contributions, and discuss their im-
pact. Relevant findings are supplemented with additional background and state-of-the-art
contextual discussions.
We identified a total of 27 papers (out of 850 records screened) as eligible for our review
during the data bank search. Another 11 papers were identified during snowballing of
relevant work. According to our review, hydrogen is considered for both electrification and
clean cooking purposes. Twenty-six studies focused on the application of power supply,
while four studies explicitly conducted research on hydrogen as a cooking fuel. Seven
studies included aspects of both; see Figure A2a of the Appendix A.
We observe an increasing trend in the number of yearly publications in the rationale
of SDG 7.1.1 from 2018 (n = 2) to 2021 (n = 11); see Figure A2b of the Appendix A. The
technical (n = 34) and economic (n = 31) dimensions have been investigated most extensively
by far, applying optimization and simulation (see Figure A3b of the Appendix A). In
contrast, the environmental dimension is included in 14 studies. Social investigations
are underrepresented, with three studies considering social aspects. Of those papers
investigating hydrogen-based cooking, only a single study reflected on social aspects to
consider (see Section 3.4). Figure A4 of Appendix Avisualizes the geographic distribution
of the case-study locations.
3.1. Technical Integration in Energy Systems
Theoretical studies in the run-up to field studies are a useful tool to analyze optimal
integration pathways of technologies and determine useful energy-system topologies.
Such techno-economic feasibility studies commonly apply mathematical optimization
and simulation to define optimal solutions and system configurations in dependency of
variables and levers involved. The variables and levers may include:
•
Setting specific variables: Load demand; seasonality influences towards load and supply.
•
Economic parameters: Project parameters including weighted average cost of capi-
tal (WACC), investment costs, operation and maintenance costs, replacement costs,
fuel costs.
•
Availability of resources: Grid availability for interconnection, availability of renew-
able energy sources, availability of fossil fuels.
•
System configuration: Technology availability, control algorithm, technology configuration.
•Environmental constraints: Renewable energy share, maximum emissions.
•Technical constraints: Loss of power supply probability, energy shortage, energy excess.
Only a few of the screened papers proposed and assessed large-scale hydrogen pro-
duction on the regional level combined with transport to rural areas, as summarized in
Table 6. Examples are found for the countries of Nepal [
46
], Nigeria [
47
], Ecuador [
48
],
and Iran [
49
]. However, the majority of all screened papers (90%) proposed hydrogen
production and application in smaller-sized, off-grid systems. We therefore define three
popular energy-system topologies including hydrogen for SDG 7.1 focused applications:
(A.a). Off-grid power supply to appliances with lower electrical needs (typically lightbulb,
fan, TV, radio, phone charger [
50
]); (A.b) Off-grid power supply to electrical appliances
including electric cooking, and (B) Separate off-grid power supply and hydrogen cooking
via combustion. Figure 2illustrates the respective energy-system topologies.
Energies 2023,16, 1658 10 of 42
Energies 2023, 16, x FOR PEER REVIEW 10 of 38
including electric cooking, and (B) Separate off-grid power supply and hydrogen cooking
via combustion. Figure 2 illustrates the respective energy-system topologies.
(A)
(B)
Figure 2. (A) Hydrogen integration in an off-grid renewable energy system for electrification of (a)
lower appliances, and (b) additional electric cooking; and (B) Separate off-grid power supply and
hydrogen cooking via combustion. Notably, the figures neglect the type of current supplied to the
loads. Historically, alternating current (AC) loads are more common, however, efficient direct
current (DC) loads are becoming more popular. While a DC supply and load is directly compatible
with the EL and FC respectively, an AC/DC and DC/AC power converter is required when
integrating with AC systems.
(A)
Off-grid power supply:
The extension of the national grid was a significant driver of increased electrification
in many countries during the last years [6]. However, for remote and sparsely populated
regions, grid extension may not be a financially viable solution [51]. In such settings, off-
grid hybrid renewable energy systems, combining multiple renewable generation assets
and storage, are proposed as an environmentally sound alternative to the fossil
counterpart of decentralized diesel generators (DGs). Integrated with such electricity
systems, hydrogen can serve as an energy storage and backup power supply system to
balance the intermittent renewable power generation technologies. The versatility of
hydrogen makes it appropriate to be coupled with batteries or supercapacitors. While the
latter two may serve for short-term storage, hydrogen may buffer for long-term storage.
Figure 2.
(
A
) Hydrogen integration in an off-grid renewable energy system for electrification of (
a
)
lower appliances, and (
b
) additional electric cooking; and (
B
) Separate off-grid power supply and
hydrogen cooking via combustion. Notably, the figures neglect the type of current supplied to the
loads. Historically, alternating current (AC) loads are more common, however, efficient direct current
(DC) loads are becoming more popular. While a DC supply and load is directly compatible with the
EL and FC respectively, an AC/DC and DC/AC power converter is required when integrating with
AC systems.
(A)
Off-grid power supply:
The extension of the national grid was a significant driver of increased electrification
in many countries during the last years [
6
]. However, for remote and sparsely populated
regions, grid extension may not be a financially viable solution [
51
]. In such settings,
off-grid hybrid renewable energy systems, combining multiple renewable generation
assets and storage, are proposed as an environmentally sound alternative to the fossil
counterpart of decentralized diesel generators (DGs). Integrated with such electricity
systems, hydrogen can serve as an energy storage and backup power supply system
to balance the intermittent renewable power generation technologies. The versatility of
hydrogen makes it appropriate to be coupled with batteries or supercapacitors. While the
latter two may serve for short-term storage, hydrogen may buffer for long-term storage. As
the size of the FC is independent from the capacity of hydrogen energy storage, high-power
Energies 2023,16, 1658 11 of 42
devices can potentially be served without increasing the costs of storage. This eventually
allows for even-power electric cooking appliances, thereby simultaneously stimulating
electrification and clean cooking efforts. Table 5comprises the identified studies proposing
hydrogen usage for off-grid electrification of lower appliances (energy system-topology
A.a) and additional electric cooking [energy-system topology A.b)]). It must be well-noted
that some studies reporting an aggregated demand profile may also include electric cooking
without our knowledge. The systems reported in the studies reviewed are mostly designed
and optimized for small villages and loads. In our analysis, we find a median of peak
demand in the case studies of 13 kW (average 40 kW); see Figure 3.
Energies 2023, 16, x FOR PEER REVIEW 11 of 38
As the size of the FC is independent from the capacity of hydrogen energy storage, high-
power devices can potentially be served without increasing the costs of storage. This
eventually allows for even-power electric cooking appliances, thereby simultaneously
stimulating electrification and clean cooking efforts. Table 5 comprises the identified
studies proposing hydrogen usage for off-grid electrification of lower appliances (energy
system-topology A.a) and additional electric cooking [energy-system topology A.b)]). It
must be well-noted that some studies reporting an aggregated demand profile may also
include electric cooking without our knowledge. The systems reported in the studies
reviewed are mostly designed and optimized for small villages and loads. In our analysis,
we find a median of peak demand in the case studies of 13 kW (average 40 kW); see Figure
3.
Figure 3. Peak demand and average daily electricity consumption in off-grid systems.
The median of the average daily electricity consumption is 84 kWh (average 408
kWh). However, in the few studies that explicitly report electric cooking to be included in
the demand profile [52–54], average per capita peak demand and per capita electricity
demand are substantially higher compared to the overall median of the larger sample
group (60% and 1160% positive deviation respectively).
Most techno-economic feasibility studies analyzed propose photovoltaic (PV) as the
primary electricity source to power water electrolysis, with a median of 40 kW, followed
by wind turbines (WTs) (median 16 kW). The median optimal sizes of common backup
DGs are 8 kW and 166 Ah, in the case of battery storage. While the studies reveal a
competition between the DG and the hydrogen system—i.e., usually only one of the two
backup systems is included in the optimal system design—the battery storage and
hydrogen system are commonly combined. This is because the hydrogen system serves
the same operational niche as DGs, which is to buffer for long-term energy storage, while
the battery fills short-term storage demand. Thus, battery storage and hydrogen storage
are complementary but not competitive in energy-system operation. Median sizes of the
hydrogen systems are reported as 10 kW FC, 14 kW EL, and 15 kg hydrogen storage.
Notably, all studies reviewed except one propose PEMFC and PEMEL technologies,
justified by technical advantages against competitive technologies (including dynamic
behavior and efficiency). Cross-checking this proposition with actual current market
Figure 3. Peak demand and average daily electricity consumption in off-grid systems.
The median of the average daily electricity consumption is 84 kWh (average 408 kWh).
However, in the few studies that explicitly report electric cooking to be included in the
demand profile [
52
–
54
], average per capita peak demand and per capita electricity demand
are substantially higher compared to the overall median of the larger sample group (60%
and 1160% positive deviation respectively).
Most techno-economic feasibility studies analyzed propose photovoltaic (PV) as the
primary electricity source to power water electrolysis, with a median of 40 kW, followed by
wind turbines (WTs) (median 16 kW). The median optimal sizes of common backup DGs
are 8 kW and 166 Ah, in the case of battery storage. While the studies reveal a competition
between the DG and the hydrogen system—i.e., usually only one of the two backup systems
is included in the optimal system design—the battery storage and hydrogen system are
commonly combined. This is because the hydrogen system serves the same operational
niche as DGs, which is to buffer for long-term energy storage, while the battery fills short-
term storage demand. Thus, battery storage and hydrogen storage are complementary but
not competitive in energy-system operation. Median sizes of the hydrogen systems are
reported as 10 kW FC, 14 kW EL, and 15 kg hydrogen storage.
Notably, all studies reviewed except one propose PEMFC and PEMEL technologies,
justified by technical advantages against competitive technologies (including dynamic
behavior and efficiency). Cross-checking this proposition with actual current market
shares shows that PEMFCs indeed record the most sales today (manufacturing capacities
for PEMFCs exceeded 1100 MW in 2020, which at that time was more than ten times
Energies 2023,16, 1658 12 of 42
higher than the manufacturing capacities of competitive technologies [
9
]). However, the
predominant suggestion of PEMEL in the literature may be surprising, considering the
current market status in EL technologies. Here, AEL is the most mature EL technology with
currently the lowest investment costs and largest application [
13
]. However, stagnation in
efficiency improvement and cost reductions, as well as limitations in dynamic behavior
might have motivated the search for alternatives at the expense of increased costs due to
lower maturity [55].
The studies [
52
–
54
] explicitly include electric cooking in the assumed electric demand
profile, simultaneously addressing electrification and clean cooking. Today, electric cooking
in off-grid systems is not popular due to the high-power requirements of electric stoves that
can usually only be satisfied by the electrical grid. However, recent advances in stove design
(e.g., electric pressure cookers) and increased energy efficiency may facilitate the increased
application of electric cooking in off-grid systems [
56
]. The studies reviewed suggest
hydrogen systems to be a suitable alternative to grid extension to satisfy such loads. This is
due to their high reliability and power output, which offer a grid-like electricity supply [
52
].
Due to the decoupling of energy storage in hydrogen tanks and power supply via FC,
hydrogen systems—in contrast to battery storage—can be flexibly designed for higher
power demands without necessarily increasing costly energy storage. Such application of
FCs, facilitating electric cooking in off-grid systems, may offer significant opportunities
to accelerate access to clean cooking. By mutually linking the cooking system to the
electricity supply system and sharing assets, energy efficiency and economic synergies
could be unlocked. Furthermore, from an institutional perspective, the complexity of
the stakeholders involved might be reduced. Stakeholders seeking clean cooking may
co-use the infrastructure and arrangements established in the electrification sector. For
example, minigrid operators that, at the moment, can rely on clear regulations assuring clear
financial planning in the long-term in many African countries could become responsible
for the rollout of clean cooking projects via electric cooking, avoiding the time-intensive
development of similar structures for clean cooking agents.
(B)
Separate power supply and hydrogen cooking via combustion
Table 7summarizes studies reviewed that propose the use of hydrogen for cooking via
combustion, in separated infrastructures to the electricity supply system. Young et al. [
57
]
and Topriska et al. [
58
] propose hydrogen cooking fuel production systems for rural villages
separate from the electricity infrastructure (note that Figure 2B suggests at least to share the
primary electricity generation assets). While the renewable power generation systems serve
electricity to the village and simultaneously feed an electrolyzer in [
57
], Ref. [
58
] considers a
standalone PV system dedicated to produce hydrogen via a PEMEL. In contrast to utilizing
electricity supplied by FCs for cooking purposes, the direct combustion of hydrogen for
cooking and heating purposes is suggested.
The physical and chemical properties of hydrogen allow for conventional combustion
in oxygen-fuel mixing burners. In fact, hydrogen has very similar properties to popularly
known cooking fuels, such as LPG or methane. Table 3presents selected key characteristics
of hydrogen, propane, and methane as reference gases. Key characteristics and advantages
of hydrogen against its fossil counterparts are:
•The higher hydrogen-air flame temperature allows for quick and flexible heating.
•The high diffusion coefficient is a great safety advantage.
•
Hydrogen can be ignited within a wide flammability range with low ignition energy
required.
•
Hydrogen has a high (gravimetric) energy density, offering great potential for storage
and transport.
Energies 2023,16, 1658 13 of 42
Table 3.
Selected properties of hydrogen, propane, and methane. As the main compound of LPG and
natural gas, the properties of propane and methane approximate LPG and natural gas properties,
respectively.
Property Unit Hydrogen (H2) Propane (C3H8) Methane (CH4)
Molecular weight u 2.01594 [59] 44.1 16.4
Gravimetric energy content MJ/kg 120 [60] 46.4 [60] 50 [60]
Higher heating value (HHV) MJ/Nm3
(MJ/l Propane) 12.75 [61] 26.5 [62] 39.82 [61]
Flammability range (Equivalence ratio) 0.1 ∼7.1 [60] 0.51 ∼2.5 [60] 0.5 ∼1.7 [60]
Max. laminar burning velocity m/s 2.91 [60] 0.43 [60] 0.37 [60]
Adiabatic flame temperature in air ◦C 2.110 [60] 2.000 [60] 1.950 [60]
Diffusion coefficient in air Cm2/s 0.61 [59] 0.1318 0.221
Minimum auto ignition temperature ◦C 520 [60] 450 [60] 630 [60]
Pointing to the similarities of hydrogen and LPG (>95% propane), Young et al. [
57
] and
Topriska et al. [
58
] propose decentralized hydrogen production, and a distribution model
and utilization of pure hydrogen similar to LPG (notably, Grovéet al. propose the same for
hydrogen-based dimethyl ether [
63
]). Hydrogen is proposed to be produced via small-scale
decentralized water electrolysis and supplied to households in portable containers, refilled
on a monthly basis. In the households, the hydrogen is burned in hydrogen stoves or
modified LPG burners [
58
]. With this, the downstream process of hydrogen cooking is in
fact analogous to established LPG cooking schemes.
Therefore, it is an obvious question to explore the actual co-usage of LPG infrastruc-
tures and search for synergies. In fact, a reasonable integration pathway of hydrogen as a
cooking fuel could be via existing LPG distribution channels, i.e., in regions in which LPG
is already popularly used as cooking fuel [
57
]. Hydrogen could either replace the LPG, or,
as a bridge solution, be blended with LPG, reducing emissions. To our best knowledge, no
studies explore the technical possibility to use relevant LPG technologies with hydrogen.
However, the findings from studies on gas blends in other settings might be transferable.
Makaryan et al. [
64
] conducted a review on studies investigating the opportunities and
challenges of blending hydrogen in European natural gas infrastructures. The authors
differentiate individual assets of the energy infrastructure. Material corrosion, safety issues,
and volumetric energy density are the main restriction factors to hydrogen admixture to
the natural gas grid. For such energy infrastructure assets relevant to the case considered
in this paper, i.e., meters, (compressed natural gas) storage tanks, house installs, and home
gas burners/stoves, the authors summarize sensitivity thresholds as cited in Table 4:
Table 4.
Sensitivity of selected natural gas infrastructure assets to hydrogen admixture as reported in [
64
].
Asset H2Blending
Uncritical Adjustment Needed Further Research
Required
Meters <30% 30%–70% >70%
CNG storage tank <30% 30%–50% >50%
House installs <30% 30%–50% >50%
Home gas
burner/stove <10% 10%–50% >50%
As a critical end-use appliance for domestic use, De Vries et al. [
61
] further detail
the analysis of impact the of hydrogen mixing on cookstove appliances. According to the
authors, the Wobbe index (indicator of the interchangeability of fuel gases), probability
of a flashback, and fuel-air ratio of the burner are decisive for the maximum fraction of
hydrogen possible to mix to a reference gas without requiring any modifications. While the
Wobbe index is a matter of thermal comfort, the flashback probability is a severe security
risk. A flashback occurs when the burning velocity in the primary flame front exceeds the
Energies 2023,16, 1658 14 of 42
velocity of the unburned mixture leaving the burner exit to such an extent that the flame will
propagate upstream into the burner, “flashing back” into the appliance [
65
]. A flashback
can cause damage to the burner or flame extinction, which, in the absence of a flame safety
device, can result in spillage of the combustible mixture. As hydrogen increases the laminar
burning velocity of a potential blend (Table 3), it increases the probability of flashbacks. De
Vries et al. find that higher Wobbe index gases can take more hydrogen before harming
safety concerns. For a gas with a high Wobbe index according to the European Union
natural gas standards (14.7 kWh/m
3≤
WNG
≤
16 kWh/m
3
), a 20% admix of hydrogen
is found to be the maximum threshold [
61
]. As LPG has an even higher Wobbe index
than such natural gas (20.3 kWh/m
3≤
WNG
≤
24 kWh/m
3
), we conclude that we may
conservatively adopt the 20% admixture threshold but propose a dedicated investigation
on hydrogen–LPG admixtures for future work. However, with this, the option to blend
hydrogen with LPG is only possible up to a limited amount of hydrogen. Modifications to
the LPG burner as shown in [66] are required to enable increased hydrogen amounts.
3.2. Economic Prospective
Hydrogen integration in off-grid energy systems for electrification remains an eco-
nomic challenge. This circumstance has been reported for off-grid systems in developed
economies [
21
] but might be even more critical in settings in the Global South with lower
purchasing power of users. The capital expenditure (CAPEX) of hydrogen components is
high, compared to other energy-system components. Figure 4comprises the CAPEX
of prominent components as reported in the reviewed literature. With a median of
3000 USD/kW and 1,500 USD/kW the fuel cell and electrolyzer respectively are the most
expensive energy-system assets. Notably, the fossil-based DG has the lowest CAPEX, with
a median of 510 USD/kW.
Energies 2023, 16, x FOR PEER REVIEW 14 of 38
exceeds the velocity of the unburned mixture leaving the burner exit to such an extent that
the flame will propagate upstream into the burner, “flashing back” into the appliance [65].
A flashback can cause damage to the burner or flame extinction, which, in the absence of
a flame safety device, can result in spillage of the combustible mixture. As hydrogen
increases the laminar burning velocity of a potential blend (Table 3), it increases the
probability of flashbacks. De Vries et al. find that higher Wobbe index gases can take more
hydrogen before harming safety concerns. For a gas with a high Wobbe index according
to the European Union natural gas standards (14.7 kWh/m
3
≤ WNG ≤ 16 kWh/m
3
), a 20%
admix of hydrogen is found to be the maximum threshold [61]. As LPG has an even higher
Wobbe index than such natural gas (20.3 kWh/m
3
≤ WNG ≤ 24 kWh/m
3
), we conclude that
we may conservatively adopt the 20% admixture threshold but propose a dedicated
investigation on hydrogen–LPG admixtures for future work. However, with this, the
option to blend hydrogen with LPG is only possible up to a limited amount of hydrogen.
Modifications to the LPG burner as shown in [66] are required to enable increased
hydrogen amounts.
3.2. Economic Prospective
Hydrogen integration in off-grid energy systems for electrification remains an
economic challenge. This circumstance has been reported for off-grid systems in
developed economies [21] but might be even more critical in settings in the Global South
with lower purchasing power of users. The capital expenditure (CAPEX) of hydrogen
components is high, compared to other energy-system components. Figure 4 comprises
the CAPEX of prominent components as reported in the reviewed literature. With a
median of 3000 USD/kW and 1,500 USD/kW the fuel cell and electrolyzer respectively are
the most expensive energy-system assets. Notably, the fossil-based DG has the lowest
CAPEX, with a median of 510 USD/kW.
Figure 4. CAPEX of main components and LCOE reported in the literature. Abbreviations: PV =
photovoltaic; HKT = hydrokinetic turbine; WT = wind turbine; DG = diesel generator; FC = fuel
cell; EL = electrolyzer; BAT = battery; H
2
storage = hydrogen storage.
However, the Levelized Costs of Electricity (LCOE) of systems including renewable
energy and hydrogen backup reported in the techno-economic studies reviewed (median
0.355 USD/kWh) are in a similar range as conventional renewable off-grid systems in
comparable settings [67,68]. We must further note that with advancing technology and
Figure 4.
CAPEX of main components and LCOE reported in the literature. Abbreviations: PV = pho-
tovoltaic; HKT = hydrokinetic turbine; WT = wind turbine; DG = diesel generator; FC = fuel cell;
EL = electrolyzer; BAT = battery; H2storage = hydrogen storage.
However, the Levelized Costs of Electricity (LCOE) of systems including renewable
energy and hydrogen backup reported in the techno-economic studies reviewed (median
Energies 2023,16, 1658 15 of 42
0.355 USD/kWh) are in a similar range as conventional renewable off-grid systems in
comparable settings [
67
,
68
]. We must further note that with advancing technology and
market maturity, the CAPEX of hydrogen components is likely to drop. For example,
the International Renewable Energy Agency (IRENA) proposes a decline in EL CAPEX
by 40% until 2030, and by >80% by 2050 (notably for large-scale systems) [
15
]. Maestre
et al. propose the substitution of expensive noble metal–based catalysts by non-Platinum
Group Metals (PGM) materials to reduce the system costs [
21
]. In addition, efficiency
improvements of both ELs and FCs are foreseen with increasing commercialization [
69
].
As the efficiency of the EL and FC influences both the investment costs—as impacting the
required installed power—and operating costs—determining the required energy input—
additional economic benefits can be expected when increasing efficiency. A potential
decline of EL and FC CAPEX would have a great impact on the economic competitiveness
of hydrogen in off-grid energy systems. [
54
,
70
–
72
] include a sensitivity analysis on FC
and EL CAPEX. Each study’s results show a steep decline in the hydrogen-based system
costs when assuming a relative reduction of EL and FC CAPEX compared to the initial
assumptions. [
52
,
72
] additionally show the impact of hydrogen storage costs on the system
results, which show less impact.
In contrast to high CAPEX, operational expenditures (OPEX) of hydrogen systems
are low [66]. The fossil counterpart of the DG, in contrast, is characterized by low CAPEX
but substantially high OPEX. Refs. [
71
,
73
,
74
] show the economic advantages of low OPEX
of hydrogen-based systems over the lifetime of a project [
71
], for example, shows that a
potential increase in diesel fuel costs of 2 USD/L to 3 USD/L leads to the hydrogen-based
system being economically advantageous against the DG in a case study of a village in
the Gulf of Guinea. Sensitivity analysis in [
74
] show the diesel fuel price to be the most
influential parameter on the economic competitiveness of hydrogen-based power supply
against a DG.
Hydrogen technologies offer the potential to harness economic benefits of sector-
coupling. An innovative approach to further decrease the costs of hydrogen systems is
presented by Baldinelli et al. [
75
]. The authors propose the integration of a reversible solid
oxide cell (rSOC) in a PV-hybrid energy storage minigrid. Aside from fulfilling the purpose
of electricity generation, the rSOC can be used in seawater desalination, as desalted water
is released as a byproduct during reconversion of hydrogen to electricity (desalinated
water co-production is on average 0.28 L/kWh
SOFC
). The authors demonstrate the proof-
of-concept on a single cell in an experimental setup, before simulating the operation of
a minigrid on an archetypal community in sub-Saharan Africa, optimizing energy and
environmental objectives [
75
]. The authors propose to include the cross-sectoral integration
(water desalination) as economic value. Therefore, water co-production is monetized in the
study. By this method, the LCOE can be reduced by approximately. 25% under today
´
s
conditions. As the amount of water desalinated is inherently coupled to the amount of
electricity generated by the rSOC, greater impact is seen in scenarios of higher per capita
electricity consumption.
However, the economic competitivity of hydrogen in clean cooking applications is even
more challenging than in power supply. Conventional cooking fuels, especially firewood
and charcoal, are inexpensive in many Global South countries. A standalone energy system
dedicated to decentralized hydrogen generation and use as cooking fuel is not economically
competitive with such traditional fuels [
66
]. Therefore, Topriska et al. [
66
] propose upfront
subsidies to finance such system solutions. However, the authors remember the failure of
historic aid-giving interventions in cooking projects. Previous solar cooking projects have
shown that distributing technologies to the very poor for free may jeopardize the uptake
of the technologies. Solar cooker projects in the past targeted extreme energy poverty.
The persons of concern, however, have associated such aids with social discrimination,
which in turn created criticism and reluctance in the uptake by the local communities [
76
].
Solution uptake by the market is therefore preferred. However, suitable business models
to enable a market uptake of hydrogen cooking must be explored to achieve economic
Energies 2023,16, 1658 16 of 42
competitiveness with traditional fuels. While the studies reviewed considered the separate
energy system for electricity supply and hydrogen cooking fuel production [
66
,
77
], the
integration of both should be explored. Increasing the cost effectiveness by triggering
synergies in the shared assets (i.e., PV, converter) is likely. Further, when considering
cooking fuel production as a byproduct of an electricity supply system analogous to water
as a byproduct reported in [
75
], economic benefits could be achieved. Generally, the average
revenue per use, a prominent economic performance indicator in off-grid systems, linearly
correlates with increasing system utilization [
68
]. Harnessing excess electricity generated
by renewable energies to produce hydrogen cooking fuel via water electrolysis could
hence improve the economic system performance of the electricity supply system [
68
].
Further, operational benefits may be unlocked when co-utilizing energy infrastructures. An
economic assessment of the effects of combining electricity and hydrogen cooking services
is suggested for future work.
Especially for costly cooking fuels, the purchase modalities are a crucial factor that
influence the affordability of the fuel for the end-user. While historically, gaseous fuels
traded in standardized containers, including LPG, confronted the user with high unit costs,
recent developments allow for incremental payments, as established for fuelwood and
charcoal. As the hydrogen cooking system proposed by Topriska et al. [
66
] builds on a
similar (in parts identical) infrastructure as LPG cooking, we assume the same payment
methods to be adoptable for hydrogen cooking.
One example of a recent success story in clean cooking is the rollout of LPG in Kenya.
In Kenya, LPG is a fundamental pillar to reach national targets in clean cooking [
78
]. The
Kenyan government is targeting an expansion of LPG use from 20% of the population in
2016 to 35% by 2030 [
79
]. However, cash-based models, requiring upfront payments for
stoves and fuel, are still the most popular business model for LPG (98%) [
22
]. The high
upfront investments pose a significant barrier to low-income households [
80
]. Therefore,
innovative business models including pay-as-you-go and layaway models evidently reduce
this barrier [
80
]. The pay-as-you-go business model allows the user to buy fuel in small
portions and to the extent they can afford. The providers supply the user with branded
LPG cylinders and a monitoring system, remotely controlling a valve. Consumers only pay
for the valve and monitoring system as an upfront investment and can make prepayments
for the gas via mobile money. The valve only releases as much gas as is paid for before
shutting down via the smart monitoring system. Thus, a user can decide to purchase small
units of gas [
80
,
81
]. Enabling such incremental payments has triggered the large uptake of
LPG as a cooking fuel in Kenya [80].
3.3. Environmental Performance
Today, approximately 95% of global hydrogen is produced from hydrocarbons (48%
methane reforming, 30% oil reforming, 18% coal gasification) [
9
]. The production of
hydrogen from hydrocarbons releases significant amounts of CO
2
. Production methods
based on renewable energy sources, avoiding CO
2
emissions, are promoted by governments
around the globe [11].
An environmental assessment of renewable a hydrogen-based power supply is con-
ventionally performed by comparing the emissions occurring from the proposed hydrogen-
based power supply to the emissions occurring from the status quo of power supply.
Ayodele et al. therefore propose ecological efficiency as an indicator to evaluate the power
supply performance according to pollutants emissions by hypothetically comparing the
integrated pollutants emissions CO
2
-equivalent (CO
2
-eq.) with existing air quality stan-
dards [
82
]. Ranging from 0 to 1, the indicator quantifies the potential of a system to conduct
a desired process as a least-polluting option, i.e., the most environmentally friendly situ-
ation (in the specific case of hydrogen production via waste-based biogas and hydrogen
utilization by a PEMFC, the process yields an ecological efficiency of 94.33%) [82].
More commonly, a measure to evaluate the environmental benefit of a hydrogen-based
power supply is to estimate the amount of air pollutants avoided by displacing currently
Energies 2023,16, 1658 17 of 42
used fossil fuels (see, e.g., [
47
,
54
,
75
]). In the electrification context, diesel fuel is usually
assumed to be the benchmark. While the amount of diesel fuel replaced is calculated based
on the heating value of diesel and respective DG efficiency, international standards for
emission factors of specific fuels are cited to determine the emissions savings. For example,
the Intergovernmental Panel on Climate Change frequently publishes emission factors for
greenhouse gas inventories [
83
]. While such inventories usually include several pollutants
associated with a fuel (i.e., CO
2
, CH
4
, N
2
O), studies mostly convert all occurring emissions
to CO
2
equivalents by multiplying each emission type with its global warming poten-
tial. With this, replacing a typical DG in off-grid power supply may save approximately
270 gCO2-eq. per kWh produced [83].
While the aforementioned procedure assesses emissions at the point-of-use, Galvez
et al. [
84
] propose to include emissions (CO
2
-eq.) released over the life cycle of the compo-
nent in a case study of a small village in Cuba. The authors report specific emissions
of 0.045 kg CO
2
-eq./kWh for mono-Si PV modules, 0.88 kg CO
2
-eq./kWh for a DG,
0.011 kg CO
2
-eq./kWh for an electrolyzer, 0.02 kg CO
2
-eq./kWh for a fuel cell, and
0.028 kg CO
2
-eq./kWh for a Pb-acid battery. Multiplying the specific emissions with
an optimized system (Homer), the authors find the hydrogen-based system to outperform
even the battery storage on environmental metrics [84].
However, common EL and FC technologies use significant amounts of rare-earth
elements and noble metals as catalysts, transport layers, and bipolar plates [
15
]. When
scaling up the production of ELs and FCs, the mining of such scarce resources will require
additional efforts, and potentially increase the environmental impact. To ensure positive
environmental impacts in the future, alternatives to the current use of noble catalysts
and titanium must be explored. A promising technology might be AEMEL. AEMEL
allows the use of non-noble catalysts and titanium-free components, but instead uses high-
surface nickel or NiFeCo as catalysts and transport layers. However, at present, AEMEL
technologies must still overcome chemical and mechanical stability problems [15].
Studies on hydrogen-based cooking are motivated by developing an alternative to
harmful traditional cooking fuels [
48
,
57
,
66
]. Indoor air pollution caused by the use of
traditional fuels is the fourth most common cause of death after malnutrition, HIV/AIDS,
and lack of clean water [
85
]. Therefore, the studies reviewed propose hydrogen as a non-
polluting cooking fuel to substitute for traditional fuel woods and minimize emissions
at the point-of-use. Topriska et al. evaluate the amount of local CO
2
emissions saved by
hydrogen cooking compared to conventional cooking with fuelwood, charcoal, and LPG in
case studies in Jamaica, Ghana, and Indonesia. Depending on the fuel stacking mix of the
respective case study, hydrogen cooking could save between 8.75 and 12.8 tons of CO
2
per
household per year [66].
As discussed in Section 3.1, the blending of hydrogen in LPG could be an entry point
for hydrogen-based cooking in energy systems. We therefore discuss the potential impact
of hydrogen–LPG blends on the point-of-use emissions. We rely on practical estimations
provided by [
61
], who experimentally blended hydrogen with methane. As discussed
in Section 3.1, we can adopt the findings to hydrogen–LPG blends. The authors in [
61
]
show that the CO
2
emissions saved by substituting methane (or LPG) with hydrogen when
blending does not linearly correlate with the amount of gas substituted, given that the
use maintains a constant thermal throughput and temperature. This is due to the lower
volumetric heating value of hydrogen compared to methane and LPG. Therefore, when
increasing the level of the hydrogen mixture, more fuel use of LPG would be required.
For the case of hydrogen–methane blends, de Vries et al. show that at fractions below
∼
30% hydrogen, the CO
2
reduction is only 1/3 of the hydrogen fraction, tempering the
expected impact of hydrogen addition to natural gas on CO
2
emissions [
61
]. Even less CO
2
reduction could be expected when blending hydrogen with LPG, given the higher heating
value of LPG compared to methane. However, no CO
2
emissions occur when completely
replacing LPG.
Energies 2023,16, 1658 18 of 42
Schmidt-Rivera et al. [
77
] extend the environmental evaluation of the system proposed
by Topriska et al. in [
58
] and demonstrated in Jamaica [
86
,
87
]. The authors follow clear
guidelines as stated in the ISO 14040/44 to estimate the cradle-to-grave life-cycle envi-
ronmental impacts of hydrogen produced in a solar-powered PEMEL and used as a fuel
for domestic cooking. Hydrogen fuel is compared to other cooking fuels including LPG,
firewood, and charcoal. The authors can build on primary data of the hydrogen cooking
system deployed under the ACP Science and Technology Programme [
88
]. The results
show that the PV system dominates the environmental impacts of the hydrogen system
by far in every considered impact category. Recycling of material and PV efficiency can
significantly improve environmental performance. Compared to other fuels, the authors
find the hydrogen system to be the best option for avoiding fossil fuel depletion, climate
change, ozone depletion, and summer smog (the last, jointly with LPG). Specifically, hydro-
gen would reduce the climate-change impact to 0.04 kg CO
2
eq./MJ compared to firewood
(0.10 kg CO
2
eq./MJ) and LPG (0.57 kg CO
2
eq./MJ). Additionally, considering the point-
of-use, local health and environmental benefits can be significantly improved when using
hydrogen as cooking fuel, compared with traditional fuels. However, the hydrogen-based
cooking system is the worst option considering the depletion of metals, freshwater eutroph-
ication, and freshwater and marine ecotoxicity. As mentioned, this is mainly due to the
solar photovoltaic panels used to generate power for the electrolyzer. This highlights the
importance of the choice of the primary electricity source in the environmental evaluation
of the overall system.
3.4. Social Considerations
With the overarching aim of improving people’s quality of life, energy systems for
electrification or clean cooking must fit into the social habits of individuals and communities.
Energy technologies must ensure an equitable distribution of the benefits along the value
chain. Vice-versa, the support and desire for energy technologies by individuals and the
community is crucial for the uptake and longevity of the solution itself. Zhang et al. [
49
]
therefore propose to consider social aspects as constraints in the initial search for the
location of energy systems. Defining the optimal location for a hybrid renewable hydrogen
system in an off-grid context in Iran via GIS, the authors limit the search to buffer distances
to the villages to respect the perceived degradation of the visual aesthetics by the local
community. Furthermore, appropriate distance from religious sites, cultural heritage sites,
and other places sensitive to the population is suggested.
As any communities’ and individual
´
s values, habits, and preferences vary with
the local context, measuring the social impact of energy technologies remains challenging.
Hernández Galvez et al. propose community acceptance as a criterion to compare hydrogen
in electrification against the fossil counterpart of a diesel generator aside from CAPEX and
life-cycle emissions [
89
]. Community acceptance should measure the degree of acceptance
by the residents regarding the different technologies involved, as a factor that may affect
the sustainability of a self-sufficient energy system. However, the study does not explore
the reasons why participants had this preference.
It is known that supply reliability is one critical factor to ensure high acceptance for
energy technologies [
90
]. Robert et al. show a vicious cycle of power supply reliability and
the willingness to pay for electricity. The authors observed that with decreasing reliability
of supply, people tended to either invest in their own power supply systems or refuse to
pay their electricity bills, decreasing the revenue of the system operator. Confronted with
less revenue, the operator could not sustain sufficient maintenance of the assets, which
caused asset failure and further decreased the reliability of the power supply system [
90
].
The versatility of hydrogen in this context might ensure a required high reliability of
power supply. Firstly, the production techniques of hydrogen are flexible, ensuring a
high reliability of the primary power source. Electricity for water electrolysis can be
served from any renewable energy source, unlocking the potential of any renewable source
available in the local context. In addition, other production techniques could diversify
Energies 2023,16, 1658 19 of 42
the hydrogen supply. In Nigeria, for example, hydrogen produced from biogases using
food waste is proposed [
82
]. Secondly, the storability of hydrogen guarantees a high
availability of power supply when integrating hydrogen energy storage. Thirdly, sizing the
FC independently from the storage capacity allows to flexibly adjust to required capacities.
With this, hydrogen-based technologies are suitable for higher power supply [
9
,
52
], and
higher quality of energy access provision. Referring to the Multi-Tier framework defined by
the Energy Sector Management Assistance Program (ESMAP) to measure energy access on
seven distinct attributes [
91
], a hydrogen-based power supply is capable to provide access
beyond Tier 3 (e.g., >200 W and 1 kWh per day). This ability is important when considering
future prospects of energy access. It must be noted that providing electricity access in the
context of SDG 7 foresees access to at least 100 kWh of supply per individual per year. While
this threshold may ensure an absolute minimum of energy services possible, energy services
enabling higher economic development opportunities are hardly possible. Approaching the
closing of the SDG period, discussions on follow-up targets have evolved. In the modern
energy minimum, it is postulated to extend the availability of electricity to people from
domestic purposes to other purposes of the wider economy, which include higher-powered
devices and energy availability for longer durations (Tier 3 and higher) [
92
]. Including
such upcoming future ambitions in today
´
s energy-system planning forcibly includes
highly reliable backup systems, such as hydrogen-based systems. The argumentation in
Babatunde et al. [
50
] underpins the ability of a hydrogen-based power supply to guarantee
a high reliability of supply, increasing the likelihood to be integrated into future energy
systems. Conducting an economic optimization, the authors find a PV/battery storage
system to be the least-cost system to power a residential load of a low-income household in
Nigeria. A subsequent MCDA, in contrast, suggests a PV/WT/FC/BAT system to be the
best option. Including the reliability of supply as an evaluation criterion, as the authors
advise for decision makers in the future, substantially improves the performance of the
hydrogen-based system.
As a central community activity, cooking is sensitive to novelties and any disruptions
of the present habits. When introducing a new cooking fuel and technology, it is suggested
that a successful alternative cooking system should be easy to adopt and should not pose
disruption to the daily habits and cooking schedule of local residents that traditionally
cook with stoves [
93
]. In countries and settings in which LPG is already a widely known
and used cooking fuel, such as India, Kenya, Ghana, and South American countries,
hydrogen cooking via combustion could meet these requirements. As Topriska et al. [
66
]
and Young et al. [
57
] propose, a distribution scheme of hydrogen fuel similar to LPG using
existing distribution channels (e.g., local kiosks or last-mile delivery) could be adopted.
Furthermore, the hydrogen cookstove system meets the criteria of ease of use during
utilization, which is a combination of direct ignition, systematic heat regulation, systematic
fuel use, allowance for partial fuel refill, non-smoking clear flame/heat, and fuel level
detection [
22
]. Notably, the ease-of-use criterion is recognized as the second most important
factor affecting the choice of cooking fuel in the Kenyan population [
22
], as an example for
a sub-Saharan context.
Topriska et al. [
66
] conducted country case studies for Jamaica, Ghana, and Indonesia
to assess the potential of hydrogen-based cooking. The system is sized via numerical
modeling to supply hydrogen cooking fuel to meet the demand of 20 households. Aside
from consumption and expenditure patterns, the authors assessed the preferences and
perceptions of different traditional fuels and LPG using a survey at the household level. The
respondents indicated their willingness to switch from their current fuel to the innovative
hydrogen fuel, if cheaper and safer than the current fuel [
66
]. Especially the users relying
on firewood as a primary cooking fuel saw a potential increase in safety as a driver to
switch to hydrogen fuel [66].
Aiming to identify safety risks occurring from decentralized hydrogen systems, Og-
bonnaya et al. [
94
] assess engineering risks, failure modes, and their effects. Hydrogen
leakage from pressurized tanks is seen as a severe risk and danger to users. The authors
Energies 2023,16, 1658 20 of 42
see a moderate probability of such failure and moderate chance that the design control will
detect such failure, but potentially hazardous risks (e.g., explosion) in case of occurrence.
However, when compared to other gases, such as LPG, hydrogen presents fewer risks due
to its non-toxic characteristics and low volatility. Since hydrogen is, for instance, 57 times
lighter than gasoline vapor, it will typically rise and disperse rapidly when leaked, reducing
the risk of ignition close to the user [
11
]. Nevertheless, Topriska et al. [
66
] explicitly suggest
metal hydride hydrogen storage as an alternative to pressurized containers to reduce the
safety threats of the system. However, metal hydride containers are still under development
at the moment and not yet cost competitive [16].
4. Concluding Remarks
Achieving universal electrification and access to clean cooking until 2030 is envisaged
in SDG 7.1. However, pace in the rate of progression in both targets and potential impacts
of the COVID-19 pandemic and the crisis in Ukraine create doubt that the final target can
be reached by 2030. International organizations and governments call for innovative tech-
nologies to be developed and embedded into existing structures to accelerate electrification
and access to clean cooking. Therefore, hydrogen has been proposed as a versatile energy
carrier to stimulate electrification efforts and clean cooking fuel provision.
This extensive review provides a status quo on prominent technical integration path-
ways, economic challenges, environmental comparison, and social considerations of hydro-
gen applications in the rationale of SDG 7.1. Initializing the review with a semi-systematic
literature search and snowballing in relevant publications, this paper presents quantita-
tive metadata and a qualitative analysis of identified contributions. Relevant findings are
supplemented with contextual discussions from relevant associated research.
Theoretical techno-economic analysis has identified three dominant integration path-
ways of hydrogen in energy systems: as a backup technology in small-scale off-grid villages
to power (A a) lower electrical appliances and (A b) additional electric cooking/heating
appliances, and (B) direct utilization of hydrogen as a cooking fuel via combustion, inde-
pendent from electricity supply. The downstream infrastructure of the latter hydrogen
cooking system is analogous to established LPG cooking systems. The co-utilization of
existing LPG infrastructures is therefore a likely market entry point.
However, in both electrification and clean cooking the high initial investment costs
required for FCs and ELs pose a challenge in competing with alternative technologies and
especially fossil fuels, the latter of which are still cheap in most settings observed. The
future likely developments of declining CAPEX and increasing technology efficiencies will
significantly improve the economic performance of the hydrogen system. However, eco-
nomic competition against traditional cooking fuels especially will require the development
of cost-efficient business models. We suggest the investigation of exploitable cost-efficiency
improvements when integrating hydrogen-based cooking (via electric cooking or combus-
tion) in electricity supply systems.
When fostering the production of hydrogen from renewable sources, a hydrogen-based
energy supply can significantly improve the environmental impact compared to the status
quo of prevailing fossil fuel–based energy supplies. Hydrogen releases no carbon point-
of-use emissions in both power supply and combustion as clean cooking fuel. However,
to prospectively decrease the life-cycle emissions and extend the environmental benefits
beyond climate-change impact and point-of-use emissions only, EL and FC technologies
avoiding noble metals and rare resources must be fostered. As the production of hydrogen
via water electrolysis depends on a primary source of electricity, the choice of the primary
source significantly impacts the environmental performance of the overall system.
Studies investigating the social impact of hydrogen-based energy supplies in the
rationale of SDG 7 are underrepresented. However, arguably the potential fit to supply
sustainable, growing energy services at levels even beyond the minimum requirements
manifested in SDG 7.1 is likely according to the literature. The literature highlights the relia-
bility and availability of supply as crucial to electricity customers. The versatile production
Energies 2023,16, 1658 21 of 42
pathways and renewable resources exploitable for its production, and the storability of
hydrogen can satisfy the need for such reliable power supply. The consideration of recent
postulations to increase the standards and thresholds for electricity supply beyond the SDG
period strengthens the arguments for backup power supply technologies in general, and
hydrogen-based power supply in particular.
In the sensitive-to-changes activity of cooking, hydrogen cooking via combustion fits
for the uptake in settings where LPG, notably recognized as transitional clean cooking fuel
due to its fossil origin only, is or will become an established cooking fuel. Building on
a similar, or even the same, distribution and utilization infrastructures, the introduction
of hydrogen as a clean cooking fuel may avoid any disruptions in the user behavior in
settings with LPG predominance, while meeting crucial ease-of-use criteria. However,
safety issues are vital for the perception of users to adopt hydrogen cooking and should be
elaborated upon.
Energies 2023,16, 1658 22 of 42
Table 5. Variables of interest for the literature considering hydrogen applications for off-grid power supply to lower electrical appliances and electric cooking.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[84] 2012 Cuba
•Optimization
•Simulation
•HOMER
•HOGA
•Technical
•Economic
•Environmental
•Evaluation of a PV/WT/BAT/FC/DG
system for electrification of a rural
community in Cuba
•Multi-objective optimization for economic
and environmental objective functions
•Optimal solutions propose H2storage
instead of storage in batteries
•
Results obtained via HOMER were compared
to those obtained by means of the HOGA
model
•Community with 200 inhabitants (40
dwellings)
•Average daily load is 120 kWh, with
a peak power of 16 kW
[89] 2013 Cuba
•Optimization
•Simulation
•MCDA
•HOMER
•Technical
•Economic
•Environmental
•Social
•Techno-economic optimization of a
PV/WT/DG/FC hybrid system for a rural
community in Cuba
•MCDA conducted applying the criteria:
Capital costs, community acceptance, and
equivalent emissions in the life cycle
•When applying low weight on the capital
cost criteria, the hydrogen-based system is
preferential to a diesel-based power supply
•As in [84]
•Average daily load is 140 kWh, with
a peak power of 35 kW
•Optimal solution including
hydrogen: 15 kW PV; 50 kW WT;
30 kW DG; 10 kW FC; 15 kW EL;
10 kg H2storage
[70] 2013 Brazil
•Optimization
•Simulation •HOMER •Technical
•Economic
•Techno-economic evaluation of a
PV/FC/BAT system to supply power in an
isolated community in the Amazon region
•PV/BAT system is economically
advantageous against the FC
•Sensitivity analysis on FC and EL capital
costs, interest rates, load, and global solar
irradiation
•Average load of 23.8 kWh/d
•
Load profile according to five houses,
a community left, a school, and a
health left
•PEMEL, PEMFC (50–60% efficiency);
Aluminum pressure hydrogen tanks
[95] * 2014 Iran •Simulation
•Carrier (for
computing the
cooling and
heating load)
•Simulation: Not
mentioned
•Technical
•Economic
•Techno-economic evaluation of a WT/H2-
hybrid system in a household size for
standalone off-grid location in Iran
•Electric heating considered
•Exergy analysis of the system
•Cooling and heating load of the
building and required hot water are
calculated for four people’s
consumption
•PEMEL (GenHy1000) and fuel cell
(BCS); compressed hydrogen storage
Energies 2023,16, 1658 23 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[71] 2015 Gulf of Guinea
•Optimization
•Simulation Odyssey (CEA)
•Technical
•Economic
•Development of a power-management
strategy for a standalone PV/BAT/FC
system and size optimization
•Performances degradation of the EL and FC
has a limited impact on the economic results
•Sensitivity analyses on BAT and hydrogen
chain costs show that the PV/BAT/H2
solution is more profitable than the PV/BAT
configuration
•Sensitivity analyses on diesel cost show that
PV/BAT/H2solution becomes more
competitive than PV/DG when diesel price
moves from 2 €/L to 3 €/L
•130 kW maximum load
•PEMEL and PEMFC considered
[96] 2015 India
•Optimization
•Simulation
•HOMER
•Unspecified
software for
modeling of the
anaerobic digester
•Technical
•Economic
•Techno-economic comparison of different
Integrated Renewable Energy Systems with
multiple generation technologies for an
unelectrified rural village in West Bengal
•H2-based system decreases excess electricity
but is the most expensive option considered
•Electrical demand of the village
containing around 1000 residents;
total energy demand of
60.27 kWh/year
•PV, BG, combined heat and power
(CHP), vanadium-redox flow BAT,
water electrolysis (unspecified, 85%
efficiency), FC (unspecified), hydride
hydrogen storage
[73] 2016 Ethiopia
•Optimization
•Simulation •HOMER
•Technical
•Economic
•Environmental
•
Techno-economic optimization of hybrid and
integrated approaches of 16 different
combinations of generation mix
configurations to electrify a rural village in
Ethiopia (Mehakelegnaw Zone of the Tigray
Region)
•Sensitivity variables: Solar radiation, diesel
fuel price, BAT prices, PV prices, converter
prices have been used as sensitivity variables
•H2integration is a little more expensive than
the optimal PV/WT/HKT/BAT system
•Village with 21,450 members (3575
households)
•15,640 kWh average daily energy
consumption
Energies 2023,16, 1658 24 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[53] * 2016 Iran
•Optimization
•Simulation •HOMER
•Technical
•Economic
•Environmental
•Techno-economic feasibility study of a
PV/WT/DG/FC hybrid system for a
residential, not grid-connected household in
Teheran, Iran
•Electric cooking explicitly considered
•WT/H2/BAT hybrid system is the most
economical solution
•Average daily energy demand of
17 kWh/d with 1.5 kW peak
•Devices powered: Lighting, a color
television set, a refrigerator, an air
conditioner, a washing machine, a
water heater, an electric cooker, and
small power appliances
[97] 2017 India
•Optimization
•Simulation HOMER
•Technical
•Economic
•Techno-economic feasibility study of a
PV/FC/BAT hybrid system for Jhiriya
Kheda, a small unelectrified village located in
Huzur Tahsil
•Sensitivity analysis on the initial tank level
relative to the tank size expressed in
percentage
•Energy demand includes domestic,
agricultural, commercial, and street
lighting
•Peak load of the system is 4.7 kW
•Optimal solution: PV (5 kW),
PEMFC (4 kW), Battery, electrolyzer
(0.1–0.3 kW); pressurized hydrogen
storage
[98] 2017 Malaysia
•Optimization
•Simulation HOMER
•Technical
•Economic
•Environmental
•Techno-economic feasibility study of a
renewable hybrid system to electrify a
residential long-house in rural Malaysia
•PV/FC system is 12% more expensive than a
PV/BAT system
•Sensitivity analysis performed to assess the
impact of variation in solar irradiation and
load profile
•The average load consumption is
140.75 kWh/day, and the peak
demand is 20.85 kW and average
load is 5.81 kW
•Optimized system including
hydrogen: PV (71 kW), FC (5 kW),
EL (3 kW), BAT
[99] 2018 United Arab
Emirates
•Optimization
•Simulation Not mentioned.
•Technical
•Economic
•Techno-economic analysis of an off-grid
hybrid solar PV/FC power system for a
residential community in a desert region in
the UAE
•Dust accumulation and temperature effects
on the PV system were analyzed
•150 houses with 4500 kWh average
daily electricity demand
•PEMFC (70% efficiency HHV);
generic EL (90% efficiency HHV);
pressurized hydrogen tank
•Optimal topology: 517 kW PV;
750 kW FC; 250 kW EL 900 kg
hydrogen tank)
Energies 2023,16, 1658 25 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[54] * 2018 Ethiopia
•Optimization
•Simulation HOMER
•Technical
•Economic
•Techno-economic feasibility study (using
HOMER) of emission-free hybrid power
system of PV/WT/FC/BAT, for a rural
village in Ethiopia called Nifasso
•The least-cost system under today´s
conditions includes PV and BAT
•Reducing the PV CAPEX by less than 10% or
reducing the FC CAPEX by 20% leads to
integration of the FC in the optimal system
topology
•Daily power demand and energy
needs for the community of 289
households are estimated by
considering basic domestic
appliances such as television (70 W),
CFLs of 11 W and 15 W for lighting,
radio/tape (5 W), VCD/DVD player
(15 W), refrigerator (70 W), “electric
mitad” (2.5 kW), cell phone (2.5 W),
and stove (1.5 kW); and public loads
including hospital, church, school,
water pumps, miller
•Least-cost system (NPV) including
hydrogen: 150 kW PV, 100 kWh BAT,
10 kW PEMFC, 40 kW PEMEL
[100] 2018 Ecuador
•Simulation
•Optimization
•Simulation of the
river energy
potential:
HEC-RAS
System Optimization:
HOMER
•Technical
•Economic
•Evaluation of an optimal location of an HKT
in a cross-section of the river
•Techno-economic study of a
PV/HKT/FC/BAT hybrid system for
electricity supply to Santay Island, Ecuador
•Island village with 235 persons in 46
houses
•
Average load of 4.18 kW with 5.6 kW
peak
•HKT/PV/FC/BAT hybrid system
•PEMFC (50% efficiency), PEMEL
(85% efficiency); compressed
hydrogen storage
•Optimal system topology (at COE
0.254$/kWh): PV (36 kW), HKT
(15 kW), FC (6 kW), EL (10 kW),
hydrogen tank (10 kg), BAT (25 kWh)
Energies 2023,16, 1658 26 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[52] * 2018 South Africa
•Optimization
•Simulation •HOMER •Technical
•Economic
•Optimization to determine the least-cost
pathway to supply energy to an off-grid
farming village
•The load profile includes lighting, cooking,
and hot-water demands
•The H2storage enables for high reliability
and grid-like electricity supply
•The off-grid system is financially beneficial
against grid extension at >4000 km distance
•Napier farming village (4214
inhabitants)
•Annual average energy requirement
of 1080.60 kWh per day at 370.08 kW
of peak load
•1026 kWp PV, 497 kW WT, 300 kW
FC, 110 kW EL, 90 kg H2tank
[74] 2019 Iran Optimization •MATLAB
•Technical
•Economic
•Environmental
•Multi-objective crow-search optimization of
PV/DG/FC system for an off-grid
community in Kerman
•Total net present costs and loss of power
supply probability are considered as decision
variables
•Integration of hydrogen energy technology
will reduce the total cost of the hybrid energy
systems
•Residential load with peak demand
of 55 kW
•PEMFC, PEMEL, pressurized
hydrogen tank
•Optimal sizes at 0% loss of power
supply probability: 443 kW PV,
30 kW DG, 7 kW FC, 26 kW EL
[101] 2019 Iran
•Optimization
•Simulation HOMER
•Technical
•Economic
•Techno-economic optimization on the
provision of electricity and hydrogen with
renewable grid-connected and off-the-grid
systems for Bandar Abbas City
•
Four types of commercially available vertical
axis WT are compared
•H2considered to replace a DG
•Annual average electricity
requirement is 13.9 kWh/day
(hourly maximum 2.12 kW)
•Annual average hydrogen
requirement is 85 kg/day (maximum
11.5 kg/h)
Energies 2023,16, 1658 27 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[102] 2019 Iran
•Optimization
•Simulation
•MCDA HOMER
•Technical
•Economic
•Techno-economic comparison of energy
systems for electrification of a rural village in
off-grid and grid-connected scenario
followed by MCDA on economic and
technical criteria
•
Grid-connected scenarios perform better than
off-grid cases
•
Adding a FC to costs by 33–37% compared to
a biogas system, but also improve system
reliability in off-grid scenarios
•Rural village with 360 people and
total average electricity demand of
361 kWh/day; 55.47 kW peak load
•Hybrid PV/WT/Biogas
(BG)/PEMEL/PEMFC renewable
energy system in off-grid and
grid-connected scenario
[103] 2019 Egypt
•Optimization
•Simulation MATLAB
•Technical
•Economic
•Techno-economic optimization of a
PV/WT/FC hybrid system to electrify a
small-scale countryside area in Egypt
•Results from firefly algorithm compared to
those obtained from the shuffled frog-leaping
algorithm and particle swarm optimization
•
FC has major impact on the system reliability
•445 houses with mean demand of
35 kW (maximum demand 92 kW)
•Village is grid-connected but with
low reliability and limited supply
•PEMEL (efficiency 90%), PEMFC
(efficiency 50%); compressed
hydrogen storage
•Optimal solution: 41 kW PV; 30 kW
FC, 64 kW EL, 182 kWh hydrogen
storage
[104] 2020
Archetype rural
community in
sub-Saharan
Africa
•Experiment
•Simulation MATLAB
•Technical
•Environmental
•Economic
•Experimental study of an rSOC for
simultaneous electricity generation and
seawater desalination
•Simulation of the rSOC integration into an
archetypal minigrid in sub-Saharan Africa
and optimization for energy and
environmental objectives
•The rSOC system shows increased energy
performance and lower emissions compared
to a PV/DG system, while producing 20–25 L
desalted water per capita each year
•Community with 410 inhabitants
and 17% electrification rate
•
Annual electricity demand per capita
of 75 kWh/y/p and average electric
power of 3.5 kW
•Best energy performance solution:
PV (39 kW), DG (5 kW), hydrogen
storage (125 kWh), rSOC (11 kW),
flywheel (58 kW)
Energies 2023,16, 1658 28 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[105] 2020 Saudi Arabia
•Optimization
•Simulation HOMER
•Technical
•Economic
•
Techno-economic feasibility study of a hybrid
PV/FC/BAT system to supply a small
community close to NEOM in Saudi Arabia
•Sensitivity analysis on PV (200 kW–280 kW)
variation of the tilt angle of the PV array and
the derating factor
•Hybrid PV/FC/BAT system is economically
advantageous against grid extension or a DG
•Small community with a daily load
demand is 500 kWh, with a peak of
35 kW
•Optimal solution: 200 kW PV array,
40 kW PEMFC (50% efficiency), 96
batteries, 50 kW converter, 110 kW
PEMEL (85% efficiency), and 50 kg
hydrogen tank
[75] 2021 Tanzania
•Simulation
•Optimization MATLAB
•Technical
•Economic
•Environmental
•
Economic impact analysis of integration of an
rSOC in a rural community for electricity
supply and simultaneous water desalination
•A novel evaluation method is proposed to
measure to what extent cross-sectoral
integration favors economic competitiveness
(LCOE decline in ~25%)
•Scenarios according to future increase in per
capita consumption show valuable economic
benefits of water desalination on the overall
system performance
•Community with 410 inhabitants
and 17% electrification rate
•
Annual electricity demand per capita
of 75 kWh/y/p and average electric
power of 3.5 kW
•Scenarios of increased per capita
consumption according to STEPS
[106] 2021 Iran Optimization MATLAB
•Technical
•Environmental
•Improved optimization algorithm (global
dynamic harmony search) of an off-grid
hybrid WT/FC energy scheme
•Case study on a remote area located in
Southern Khorasan Province, Iran
•Global dynamic harmony search algorithm
finds better fitting results than harmony
search algorithm
•Peak load of the system 7.5 kW
•Generic FC (50% efficiency), generic
EL (74% efficiency), compressed
hydrogen tank
Energies 2023,16, 1658 29 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[107] 2021 India
•Optimization
•Simulation HOMER
•Technical
•Economic
•Techno-economic feasibility assessment and
optimal sizing of PV/FC energy system
based on simulation results for the
application of off-grid electricity generation
for NE India states
•
Hydrogen-based power supply is found to be
a feasible option for NE India states
considering costs and reliability of power
supply
•Typical AC electrical load profile of
10 kWp is assumed; scaled daily
annual mean value equal to
138 kWh/d
•Optimal system design: 110–120 kW
PV array, 10–15 kW PEMFC,
30–60 kW PEMEL, 40–60 kg
compressed hydrogen tank capacity
[108] 2021 Iran
•Optimization
•Simulation •HOMER
•Technical
•Economic
•Environmental
•Techno-economic feasibility study to
investigate several hybrid renewable systems
for power supply of a remote village in Iran
•Sensitivity analysis on component costs,
changes in solar irradiation and wind speed,
fuel price and discount rate
•The hydrogen-based system increases the
system costs compared to the optimal
solution by 50% but reduce the excess
electricity significantly
•Village with 2000 inhabitants
•Maximum consumption of each
household is 13.68 kWh/day by
2.16 kW peak
•PEMFC, PEMEL
[109] 2021 Brazil Experiment / Technical
•Experimental investigation of the effects on
the performance and combustion process of a
diesel generator set operating with addition
of hydrogen in the air intake
•Proposed fuel blending scheme for isolated
diesel generators in Brazil
•Results show an increase in the engine
performance and decrease in CO2, CO, and
HC emissions proportional to the increase of
H2
•Genset: BRANCO BD-6500 CF3E (a
typical engine used in the amazon
region)
•Different fuel compositions
Energies 2023,16, 1658 30 of 42
Table 5. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[72] 2021 Tibet/China
•Optimization
(Amended
Water Strider
Algorithm)
•Simulation
MATLAB
•Technical
•Economic
•Techno-economic analysis of an off-grid
PV/FC system to provide electricity to a
remote Tibetan village
•Improved metaheuristic, Amended Water
Strider Algorithm, is applied to optimize for
the least net present value of the system and
compared to particle swarm optimization
algorithm, flower pollination optimization
algorithm and original Water Strider
Algorithm
•
Sensitivity analysis shows FC and EL costs to
have the greatest impact on the overall result
•Jiaju Tibetan Village with 140 houses
•PEMFC (85% efficiency); PEMFC;
compressed hydrogen storage
[94] 2021
Unspecified
Africa, Middle
east, Asia
Rigorous analysis MATLAB Technical
•
Analysis of failure modes, effects, and critical
analysis of failure modes of components of
an integrated PV/FC system to supply power
and thermal energy to off-grid areas in
developing countries
•Lack of solar radiation, H2leakage, failure of
photovoltaic module, leakage of oxygen have
the highest risk priorities
•Generating power with both battery and FC
may improve the overall reliability of the
system
•System including
photovoltaic-thermal (PV/T)
module, a cold-water source and
hot-water storage tank; inverter, a
PEMEL, a H2and oxygen storage
tanks, PEMFC, and a BAT and
ancillary components (pumps,
compressors, reheater, tanks)
[50] 2022 Nigeria
•Optimization
•Simulation
•MCDA HOMER
•Technical
•Economic
•Environmental
•Techno-economic optimization and MCDA
(COPRAS method) analysis of a hybrid
PV/WT/FC/BAT system to power a
residential load in Nigeria
•While a PV/BAT system is the least-cost
solution, MCDA suggests a
PV/WT/FC/BAT system
•MCDA criteria applied are total capital costs,
total net present costs, cost of energy, capacity
shortage, excess electricity, total electrical
production, NOx emission
•Residential load of a low-income
household in Nigeria
•Peak demand of 0.53 kW with
average daily electricity
consumption of 2.71 kWh
•
Optimal hydrogen-based system: PV
(2 kW), WT (0.4 kW), FC (0.4 kW), EL
(3 kW) H2tank (2 kg), BAT (800 Ah)
* Estimated demand explicitly includes electric cooking appliances.
Energies 2023,16, 1658 31 of 42
Table 6.
Variables of interest for the literature considering hydrogen applications for power supply with large-scale hydrogen production or large-scale power
production.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[49] 2020 Iran
•Optimization
(improved
harmony search)
•Geographical
information
system
•Optimization:
MATLAB
GIS: Not mentioned
•Technical
•Economic
•Environmental
•Social
•Improved heuristic approach of
combining improved harmony search
and geographic information system to
assess the viability of an off-grid
PV/H2system for rural electrification
in Iran
•The GIS solution respects technical,
economic, environmental, and social
parameters in defining the optimal site
•Birjand County region in Iran
with 75,000 people living in rural
areas and 185,000 in urban areas
[46] 2021 Nepal Rigorous analysis Not mentioned
•Technical
•Economic
•Evaluation of the potential of green
hydrogen production from surplus
hydropower energy and its application
in electricity regeneration in off-grid
areas in Nepal
•Complete diesel-powered thermal
plant production can be replaced by
electricity generated from hydrogen in
2022 when utilizing 60% of the surplus
electricity available
•Surplus from existing
hydropower stations (mostly
run-of-river types) as primary
electricity source
•
EL energy consumption: 50 kWh
per kg H2
•FC with 60% efficiency for
re-electrification
[47] 2021 Nigeria •Simulation •EnergyPLAN
•MATLAB
•Technical
•Economic
•Environmental
•
Evaluation of sustainable electrification
pathways for the country case study of
Nigeria
•Integration of RE technologies in the
existing non-RE energy mix
•H2production and storage can
significantly increase the share of RE in
the power mix
•National power plant mix
•Large-scale PEM considered
(0.019 kg/kWh)
Energies 2023,16, 1658 32 of 42
Table 7. Variables of interest for literature considering separate power supply and hydrogen utilization as clean cooking fuel via combustion.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[57] 2007 Bhutan •Rigorous analysis Not mentioned
•Technical
•Economic
•Techno-economic feasibility study of a
PV/H2-based energy system for
supplying power and clean cooking
fuel for two case-study villages in rural
Bhutan
•H2used as energy storage for power
supply and combustion fuel for
cooking and space heating
•The analysis suggests the technical
feasibility for both power supply and
clean cooking, while financial viability
is likely in regions far of the electricity
grid
•Electricity system as described in
Table 4
•150 households considered
•112.65 kWh/month cooking energy
requirement for an average 5 members
household; Estimated 40 Nm3
hydrogen requirement
•5 Nm3 H2/month space-heating
requirement for a catalytic space heater
•Portable hydrogen cylinder with size
providing a week’s supply
[58] 2015 Jamaica
•Experiment
•Simulation model TRYNSYS •Technical
•Laboratory experimental
measurements of a PEMEL, controls,
gas management, and metal hydride
storage
•
A semi-empirical numerical model of a
solar-powered PEMEL is developed
•
The hydrogen produced is proposed to
be used for cooking applications in a
Jamaican village
•The daily cooking demand of the
community (20 households) is
39.6 kWh (1.7 kg) hydrogen
•The proposed system consists of a
1.14 Nm3PEMEL operating at 3–13.8
bar metal hydride storage (LaNi5) and
100.8 kW PV
[48] 2016 Ecuador •Rigorous analysis Not specified •Technical
•Assessment of the
hydrogen-production potential to
substitute firewood as cooking fuel
(and mobility fuel) in rural Ecuador per
province
•Sufficient hydrogen-production
potential in 22 of 23 provinces
•Surplus of hydrogen-production
potential could be used to additionally
supply electricity vie fuel cell to 10% of
the national rural households
•Renewable energy sources considered
are large-scale PV, WT, HKT, and
geothermal power plants
•
Hydrogen production via PEMEL with
75% based on HHV of H2, and an
availability of the electrolytic plant of
95%
•Additional PEMFC for electricity
supply with average efficiency of 50%
Energies 2023,16, 1658 33 of 42
Table 7. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[66] 2016
•Ghana
•Jamaica
•Indonesia
•Simulation model TRYNSYS
•Technical
•Social
•Environmental
•Cooking demand profiles for rural
villages (20 households) in Jamaica,
Ghana, and Indonesia are evaluated
via statistical analysis
•Sizing of a hydrogen cooking supply
system via numerical modeling
•Solar hydrogen potential maps are
created for Jamaica, Ghana, and
Indonesia
•Comparing TMY and recent weather
data shows marginal effects on the
results
•Responses to a survey show great
willingness to change from current fuel
use to hydrogen fuel in the population,
if it was cheaper and safer than current
fuels
•
Central production of hydrogen via PV
supplied PEMEL
•
Ghana: 77.4 kW PV; 2
×
2 Nm
3
/h PEM;
3.35 kgH2storageJamaica: 63 kW PV;
2×2 Nm3/h PEM; 2.65 kg H2
storageIndonesia: 54 kW PV;
2×2 Nm3/h PEM; 2.7 kg H2storage
•H2in metal hydride cylinders for
distribution to households on a
monthly basis
•
Modified LPG gas stoves for hydrogen
combustion
[77] 2018 Jamaica LCA GaBi V6.110 Environmental
•Environmental LCA of a solar
hydrogen-based cooking system in
Jamaica
•Comparison to other traditional fuels
and LPG
•Hydrogen-based cooking would
mitigate climate-change impacts at the
expense of other impact categories
•LPG is still environmentally a better
option than hydrogen for most of the
impacts
•
The PV modules are by far the greatest
contribution to life-cycle emissions of
the system
•Rural village with 20 households
•PV 100.8 kWp
•Cascade high-pressure hydrogen steel
storage (13.8 bar)
•Low-pressure (3 bar) portable
hydrogen cylinders
Energies 2023,16, 1658 34 of 42
Table 7. Cont.
Source Year Study Location Methods Software Dimensions of
Sustainability Highlights System Description
[63] 2017 India
•Rigorous analysis
•Simulation Aspen Plus
•Economic
•Technical
•
Economic evaluation of DME based on
hydrogen produced via water
electrolysis as cooking fuel in rural
households
•Combustion of DME in LPG stoves
proposed
•DME blending into existing LPG
infrastructures proposed (up to 20% by
volume)
•Large-scale HKT and PEM with
electricity consumption of
49.2 kWh per kg H
2
and BOP electricity
consumption of 5.1 kWh per kg H2
•CO2capture from ethanol production
Energies 2023,16, 1658 35 of 42
Author Contributions:
Conceptualization, N.S.; methodology, N.S.; software, N.S.; formal analysis,
N.S.; investigation, N.S.; data curation, N.S.; writing—original draft preparation, N.S.; writing—
review and editing, N.S. and B.H.; visualization, N.S.; supervision, B.H.; project administration,
B.H.; funding acquisition, B.H. All authors have read and agreed to the published version of the
manuscript.
Funding:
This research was funded by the Horizon 2020 research program under the grant agreement
No. 101037428 (ENERGICA). The outcomes will feed into full reports submitted to the European
Commission and available on www.energica-h2020.eu.
Data Availability Statement: Not applicable.
Acknowledgments:
The authors express their gratitude to Raluca Dumitrescu for iterative discus-
sions, and Anne van Leeuwen, Lukas Otte, and Tim Ronan Britton for proofreading.
Conflicts of Interest: The authors declare no conflict of interest.
Nomenclature
Abbreviation
AEL Alkaline electrolysis
AFC Alkaline fuel cell
AEMEL Anion exchange membrane electrolysis
BAT Battery
BG Biogas
CAPEX Capital expenditure
CHP Combined heat and power
DG Diesel generator
EL Electrolysis
FC Fuel cell
GIS Geospatial information system
HECRAS Hydrologic Engineering Center’s River Analysis System
HKT Hydrokinetic turbine
HOGA Hybrid Optimization by Genetic Algorithms
HOMER Hybrid Optimization of Multiple Energy Resources
H2Hydrogen
LCA Life-cycle assessment
LCOE Levelized costs of electricity
MCDA Multi-criteria decision analysis
OPEX Operational expenditure
PAFC Phosphoric acid fuel cell
PV Photovoltaic
PEMEL Polymer membrane exchange electrolysis
PEMFC Polymer membrane exchange fuel cell
PGM Platinum group metals
PRISMA Preferred Reporting Items for Systematic Reviews and Meta-Analyses
P2H2P Power-to-hydrogen-to-power
rSOC Reversible solid oxide fuel cell
SASA Search, Appraisal, Synthesis, and Analysis
SDG Sustainable Development Goal
SOEL Solid oxide electrolysis
SOFC Solid oxide fuel cell
SSA Sub-Saharan Africa
WT Wind turbine
Energies 2023,16, 1658 36 of 42
Appendix A
Energies 2023, 16, x FOR PEER REVIEW 32 of 38
Appendix A
Figure A1. PRISMA 2020 flow diagram for new systematic reviews which included searches of
databases, registers, and other sources [110]. Notably, during the initial search on “Hydrogen” +
“off-grid” conducted in ScienceDirect, we cross-screened full texts to validate the methodology
and exclusion criteria. This reduced the number of records screened for abstract reading only by
approximately 50–90.
Figure A1.
PRISMA 2020 flow diagram for new systematic reviews which included searches of
databases, registers, and other sources [
110
]. Notably, during the initial search on “Hydrogen”
+ “off-grid” conducted in ScienceDirect, we cross-screened full texts to validate the methodology
and exclusion criteria. This reduced the number of records screened for abstract reading only by
approximately 50–90.
Energies 2023,16, 1658 37 of 42
Energies 2023, 16, x FOR PEER REVIEW 33 of 38
(a) (b)
Figure A2. (a) Total number of studies on SDG 7.1.1 and SDG 7.1.2, and (b) Historic trend in publi-
cations on SDG 7.1.1 and SDG 7.1.2.
(a) (b)
Figure A3. (a) Methods applied in studies on SDG 7.1.1 and SDG 7.1.2, and (b) Dimensions cov-
ered in studies on SDG 7.1.1 and SDG 7.1.2.
(a)
Figure A2.
(
a
) Total number of studies on SDG 7.1.1 and SDG 7.1.2, and (
b
) Historic trend in
publications on SDG 7.1.1 and SDG 7.1.2.
Energies 2023, 16, x FOR PEER REVIEW 33 of 38
(a) (b)
Figure A2. (a) Total number of studies on SDG 7.1.1 and SDG 7.1.2, and (b) Historic trend in publi-
cations on SDG 7.1.1 and SDG 7.1.2.
(a) (b)
Figure A3. (a) Methods applied in studies on SDG 7.1.1 and SDG 7.1.2, and (b) Dimensions cov-
ered in studies on SDG 7.1.1 and SDG 7.1.2.
(a)
Figure A3.
(
a
) Methods applied in studies on SDG 7.1.1 and SDG 7.1.2, and (
b
) Dimensions covered
in studies on SDG 7.1.1 and SDG 7.1.2.
Energies 2023, 16, x FOR PEER REVIEW 33 of 38
(a) (b)
Figure A2. (a) Total number of studies on SDG 7.1.1 and SDG 7.1.2, and (b) Historic trend in publi-
cations on SDG 7.1.1 and SDG 7.1.2.
(a) (b)
Figure A3. (a) Methods applied in studies on SDG 7.1.1 and SDG 7.1.2, and (b) Dimensions cov-
ered in studies on SDG 7.1.1 and SDG 7.1.2.
(a)
Figure A4. Cont.
Energies 2023,16, 1658 38 of 42
Energies 2023, 16, x FOR PEER REVIEW 34 of 38
(b)
Figure A4. Geographic location of the case studies in (a) hydrogen in the rationale of SDG 7.1.1.
Maximum = Iran (8), India (3), Cuba, Ecuador, Brazil, Ethiopia (2 respectively). Notably, three
studies did not specify the country; and (b) hydrogen in the rationale of SDG 7.1.2. Maximum =
Jamaica (3), Iran (2), others (1 respectively).
References
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S.; et al. Connecting the Sustainable Development Goals by Their Energy Inter-Linkages. Environ. Res. Lett. 2018, 13, 033006.
https://doi.org/10.1088/1748-9326/aaafe3.
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Inventions 2020, 5, 42. https://doi.org/10.3390/inventions5030042.
Figure A4.
Geographic location of the case studies in (
a
) hydrogen in the rationale of SDG 7.1.1.
Maximum = Iran (8), India (3), Cuba, Ecuador, Brazil, Ethiopia (2 respectively). Notably, three studies
did not specify the country; and (
b
) hydrogen in the rationale of SDG 7.1.2. Maximum = Jamaica (3),
Iran (2), others (1 respectively).
References
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McCollum, D.L.; Echeverri, L.G.; Busch, S.; Pachauri, S.; Parkinson, S.; Rogelj, J.; Krey, V.; Minx, J.C.; Nilsson, M.; Stevance,
A.-S.; et al. Connecting the Sustainable Development Goals by Their Energy Inter-Linkages. Environ. Res. Lett.
2018
,13, 033006.
[CrossRef]
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United Nations Sustainable Development Goals Knowledge Platform. Available online: https://sustainabledevelopment.un.org
(accessed on 11 July 2022).
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United Nations SDG Indicator Metadata Indicator 7.1.1. Available online: https://unstats.un.org/sdgs/metadata/ (accessed on
17 October 2022).
5.
United Nations SDG Indicator Metadata Indicator 7.1.2. Available online: https://unstats.un.org/sdgs/metadata/ (accessed on
17 October 2022).
6. IEA; IRENA; UNSD; WB; WHO. Tracking SDG7: The Energy Progress Report 2022; IEA: Washington, DC, USA, 2022.
7. International Energy Agency. Access to Electricity—SDG7: Data and Projections; IEA: Washington, DC, USA, 2022.
8. IRENA. Innovation Outlook Minigrids; IRENA: Abu Dhabi, United Arab Emirates, 2016.
9.
ESMAP; World Bank Group. Green Hydrogen in Developing Countries; The Energy Sector Management Assistance Program:
Washington, DC, USA, 2022.
10.
Roeben, F.; Schöne, N.; Bau, U. Decarbonizing Copper Production by Power-to-Hydrogen: A Technoeconomic Analysis. J. Clean.
Prod. 2021,306, 127191. [CrossRef]
11. Hydrogen Europe. Hydrogen Report 2022; Hydrogen Europe: Bruxelles, Belgium, 2022.
12.
Duran, A.; Sahinyasa, F. An Analysis of Renewable Mini-Grid Projects for Rural Electrification. Socio-Econ. Plan. Sci.
2020
,34,
106739. [CrossRef]
13.
Buttler, A.; Spliethoff, H. Current Status of Water Electrolysis for Energy Storage, Grid Balancing and Sector Coupling via
Power-to-Gas and Power-to-Liquids: A Review. Renew. Sust. Energ. Rev. 2018,82, 2440–2454. [CrossRef]
14.
Li, C.; Baek, J.B. The Promise of Hydrogen Production from Alkaline Anion Exchange Membrane Electrolyzers. Nano Energy
2021
,
87, 106162. [CrossRef]
15.
IRENA. Green Hydrogen Cost Reduction—Scaling Up Electrolysers to Meet the 1.5
◦
C Climate Goal; IRENA: Abu Dhabi, United Arab
Emirates, 2020.
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Danish Energy Agency. Technoloy Data Energy Storage; Technology descriptions and projections for long-term energy system
planning; Danish Energy Agency: København, Denmark, 2018.
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Akinyele, D.; Olabode, E.; Amole, A. Review of Fuel Cell Technologies and Applications for Sustainable Microgrid Systems.
Inventions 2020,5, 42. [CrossRef]
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Arsalis, A.; Georghiou, G.E.; Papanastasiou, P. Recent Research Progress in Hybrid Photovoltaic–Regenerative Hydrogen Fuel
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