1
ISBN: 1646-8929
IET Wo king Pape s Se ies
No. WPS04/2016
Manuel Baumann
(e-mail: manu[email p o ec ed])
An onio Moniz
(e-mail: [email p o ec ed]l.p )
Ma cel Weil
(e-mail: ma cel[email p o ec ed])
Ene gy s o age sys ems in he u u e Ge man
elec ici y sys em: A o esigh app oach
IET/CICS.NOVA
Inno a ion and Technology S udies pole a FCT-UNL
Cen o In e disciplina de Ciências Sociais
Faculdade de Ciências e Tecnologia
Uni e sidade No a de Lisboa
Mon e de Capa ica
Po ugal
2
Ene gy s o age sys ems in he u u e Ge man elec ici y sys em:
A o esigh app oach
Manuel Baumann 1, 2, An onio Moniz 1, 2, Ma cel Weil 2, 3
1 CICS.NOVA-FCT, Uni e sidade NOVA de Lisboa (Po ugal)
2 ITAS, Ins i u e o Technology Assessmen and Sys ems Analysis, Ka ls uhe (Ge many)
3 HIU, Helmhol z-Ins i u e o Elec ochemical Ene gy S o age, Ulm (Ge many)
Con ac : Manuel.baumann@ki .edu
Abs ac :
Ge many has ambi ious a ge s o p oduce 35 % o he needed elec ici y om Renewables mainly
based on wind and sola powe by 2020 and o e 80 % by 2050 wi hin he so called “Ene giewende”.
Ene gy s o age is seen as a po en ial op ion o assu e he sa e RES sys em in eg a ion o achie e
hese goals. The e is a high unce ain y and he esul ing public discou se abou he u u e demand
and he mos sui able ype o s o age echnology is d i ing u he de elopmen o hese
echnologies. A li e a u e e iew o 9 s udies and 10 expe in e iews a e ca ied ou in line o a
o esigh exe cise on o ackle hese unce ain ies. The es ima ions o e iewed s udies a e based
models wi h a ma ke pe spec i e on ene gy s o age demand. Mos model-based scena ios a e buil
on op down logics, whe e p ocesses a lowe le els ( echnology, mic o-economic sphe e) a e
de e mined by dominan mac o dynamics. Di e en echnologies a e only conside ed pa ially o in
an agg ega ed way. The e iewed s udies showed ha he e is a high po en ial s o age on e e y ime
scale s a ing om he yea 2030 o 2040. Analysed po en ials a y depending on RES di usion and
excess a e assump ions be ween 0 o 44 GW. Re iewed s udies s ongly in eg a e sha ed isions
abou sys em de elopmen s and o mal analyses and p o ide impo an and aluable in o ma ion
abou po en ial u u e implica ions. Bu hey only pa ially accoun , due o p ac ical easons, wide
bene i s, s akeholde opinions and con inuous changes. They accoun also discon inui ies in he
echnological inno a ion p ocess o ene gy s o age. S akeholde in e iews p o ided addi ional and
help ul insigh s o he li e a u e e iew. The s akeholde s amed al e na i e po en ial u u e
de elopmen s ha could in luence he ma ke success and need o ene gy s o age un il 2050. Mos
impo an ac o s named whe e policy measu es, new ma ke models and decen aliza ion o he
ene gy sys em. As in li e a u e he e is a big unce ain y among expe s abou he igh s o age
echnology and i ene gy s o age is in gene al he bes op ion among o he measu es as g id
ein o cemen , lexible demand and lexible powe plan s. I emains impossible o p o ide
sugges ions ega ding he de elopmen o single s o age echnologies.
Keywo ds: Elec ici y sys em; ene gy s o age; echnology assessmen
JEL codes: O33, Q42, Q55
3
Resumo
A Alemanha em me as ambiciosas pa a p oduzi 35% da ene gia necessá ia a pa i de ene gias
eno á eis baseado-se p incipalmen e em ene gia eólica e sola a é 2020 e mais de 80% em 2050 no
âmbi o do chamado "Ene giewende". O a mazenamen o de ene gia é is o como uma opção
po encial pa a ga an i a in eg ação segu a do sis ema de on es de ene gias eno á eis (FER) pa a
alcança es es obje i os. Há um al o g au de ince eza e o discu so público dela esul an e sob e a
p ocu a u u a, e sob e o ipo mais adequado de ecnologia de a mazenamen o, impulsionam o
desen ol imen o des as ecnologias. Uma e isão da li e a u a de 9 es udos e 10 en e is as com
especialis as o am ealizadas em linha com um exe cício de p ospe i a pa a esol e es as
ince ezas. As es ima i as de es udos e is os são modelos baseados numa pe spe i a de me cado
sob e a p ocu a de a mazenamen o de ene gia. A maio pa e dos cená ios baseados em modelos
em lógicas de cons ução de cima pa a baixo, onde os p ocessos em ní eis mais baixos ( ecnologia,
es e a mic o-económico) são de e minados pelas mac o-dinâmicas dominan es. Di e en es
ecnologias são conside adas apenas pa cialmen e ou de o ma ag egada. Os es udos e is os
mos a am que há um al o po encial de a mazenamen o em cada escala de empo a pa i do ano de
2030 a 2040. Os po enciais analisados a iam em unção da di usão de FER e de axas de excesso de
p emissas en e 0 e 44 GW. Os es udos in eg am isões pa ilhadas sob e a e olução do sis ema e
análises o mais e o necem in o mações impo an es e aliosas sob e possí eis implicações u u as.
Mas, elas ep esen am apenas pa cialmen e, de ido a azões p á icas e bene ícios mais amplos, as
opiniões das pa es in e essadas e mudanças con ínuas. Rep esen am ambém as descon inuidades
no p ocesso de ino ação ecnológica do a mazenamen o de ene gia. As en e is as com os
in e essados, o nece am in o mações adicionais e ú eis à e isão da li e a u a. As pa es
in e essadas nes a ques ão enquad a am desen ol imen os u u os po enciais al e na i os que
pode iam in luencia o sucesso de me cado e a necessidade de a mazenamen o de ene gia a é 2050.
Os a o es mais impo an es nomeados o am as medidas de polí ica, os no os modelos de me cado
e a descen alização do sis ema de ene gia. Como na li e a u a há uma g ande ince eza en e os
especialis as sob e a melho ecnologia de a mazenamen o e sob e se o a mazenamen o de ene gia
é, em ge al, a melho opção en e ou as medidas como e o ço da ede, a p ocu a lexí el e cen ais
lexí eis de p odução. É, no en an o, impossí el o nece suges ões sob e o desen ol imen o de
ecnologias de a mazenamen o indi iduais.
Pala as-cha e: Sis ema de ele icidade; a mazenamen o de ene gia; a aliação de ene gia
4
Con en
1 In oduc ion ..................................................................................................................................... 5
2 Me hodology: Used Fo esigh me hods .......................................................................................... 6
3 Li e a u e e iew abou u u e ene gy scena ios and s o age ....................................................... 8
3.1 Ene gy S o age Technology o e iew ..................................................................................... 9
3.2 Scena ios o Renewables and ene gy s o age sys ems ......................................................... 10
3.3 The need o scena io building o ene gy s o age demand ................................................. 11
3.4 Scena ios o sho o mid- e m s o age demand ................................................................. 13
3.5 Scena ios o long- e m s o age demand.............................................................................. 15
3.6 Resul s o he Li e a u e e iew ............................................................................................ 16
4 Visions abou he powe sys em and ene gy s o age ................................................................... 18
4.1 S akeholde in ol emen : Semi-s uc u ed in e iews ......................................................... 18
4.2 S akeholde expec a ions on he u u e ene gy sys em ....................................................... 19
4.3 Expec a ions on u u e ene gy s o age di usion .................................................................. 20
4.4 Resul s o he semi-s uc u ed in e iews ............................................................................ 22
5 Conclusion and discussion ............................................................................................................. 23
6 Re e ences ..................................................................................................................................... 24
5
1 In oduc ion
Sca ci y o uels, changes in en i onmen al policy and in socie y inc eased he in e es in gene a ing
elec ic ene gy om enewable ene gy sou ces (RES) o a sus ainable ene gy supply in he u u e [1].
This is also he case o Ge many which has ambi ious a ge s o p oduce 35 % o he needed
elec ici y om RES by 2020 and o e 80 % by 2050 wi hin he so called “Ene giewende” (ene gy
ansi ion) [2]. The main p oblem o RES as sola and wind ene gy, which ep esen a main pilla o
his ansi ion, is ha hey canno supply cons an powe ou pu . This can lead o empo a y capaci y
p oblems ega ding he high amoun o luc ua ing ene gy sou ces esul ing in e alia in an inc eased
demand o backup echnologies as ene gy s o age, demand side esponse and o he echnologies o
assu e elec ici y sys em sa e y [3]. Especially ene gy s o age is an op ion ha is highly discussed in
he public. Elec ic Ene gy S o age is a p ocess o con e ing elec ical ene gy in o a o m ha can be
s o ed and la e be con e ed back o elec ical ene gy when needed [4]. I ep esen s an enabling
echnology which imp o es he emaining elec ici y sys em, consis en o RES, g id in as uc u e,
esiden ial powe gene a ion, powe plan s and egula ion. Vice e sa i is dependen on o he
ene gy sys em de elopmen s (ma ke s de elopmen , RES-sha e, policies e c.) as well dynamics and
do no ep esen a sepa a ely iden i iable dominan sys em [5]. The u u e demand on ene gy
s o age echnologies is hus cha ac e ized by a high magni ude o unce ain ies. This has mo i a ed
he c ea ion o nume ous a ia ions o enewable ene gy sou ce and s o age pene a ion scena ios
as [6], [7], [8], [9]. This makes i di icul o d aw a obus pic u e o he demand scena ios o his
echnology wi hin he Ge man Ene giewende un il 2050.
The aim o his wo k is o sys ema ically analyse which de elopmen s and op ions o ac ion a e
a ailable o ene gy s o age nowadays and o de e mine o wha u u e ou comes his de elopmen s
can lead. This is ealized by he use and combina ion o di e en o esigh me hods, namely a
li e a u e e iew and semi-s uc u ed in e iews.

6
2 Me hodology: Used Fo esigh me hods
Fo esigh app oaches a e a discussion objec among academic esea che s, indus ialis s,
consul an s, policy-make s and o he s. The e a e a ound 5.000 academic a icles a ailable in google
schola , while google egis e s o e 90,000 hi s. Fo esigh ep esen s an explici ecogni ion ha
choices nowadays c ea e he u u e and ha he e is li le poin in making de e minis ic p edic ions
in sphe es whe e social and poli ical p ocesses exe cise majo in luences [10]. Coa es [11] o e s an
ea ly de ini ion o o esigh as ollows:
“..a p ocess by which one comes o a ulle unde s anding o he o ces shaping he long- e m u u e
which should be aken in o accoun in policy o mula ion, planning and decision-making..”
The discussions abou o esigh in academia a e cen e ed abou p ocesses, gene a ions, challenges,
classi ica ions and a ious ypes o p ac ices and me hods. The e is a la ge knowledgebase o
amewo ks, me hods and expe iences based on he use o wide sp ead o examples [12] [13]. A se
o some ypical me hods used o o esigh is gi en in able 1. I is impo an o men ion he e ha
o esigh should no be seen as a pu ely se o me hods. I is a he a p ocess wi h he aim o be e
unde s anding o possible de elopmen s and he o ces ha shape hem [10].
Table 1: O e iew o Fo esigh me hods
Quali a i e
Quan i a i e
Semi-quan i a i e
Me hods p o iding meaning o e en
and pe cep ions. Such in e p e a ions
end o be based on subjec i i y o
c ea i i y o en di icul o co obo a e
(e.g. b ains o ming, in e iews)
Me hods measu ing a iables and
apply s a is ical analyses, using o
gene a ing (hope ully) eliable and
alid da a (e.g. economic indica o s)
Me hods which apply ma hema ical
p inciples o quan i y subjec i i y,
a ional judgemen s and iewpoin s o
expe s and commen a o s (i.e.
weigh ing opinions)
1. Backcas ing
2. B ains o ming
3. Ci izens panels
4. Con e ences/Wo kshops
5. Essays/Scena io w i ing
6. Expe panels
7. In e iews
8. Li e a u e e iew
9. Mo phological analysis
10. Scena ios/scena io WS
11. Su eys
12. O he s (SWOT, e c.)
13. Benchma king
14. Indica o s
15. Bibliome ics
16. Modelling
17. Pa en analysis
18. T end ex apola ion
19. Impac analysis
20. C oss-impac analysis
21. Delphi
22. Mul i-c i e ia analysis
23. Polling
24. Quan i a i e scena ios
25. Roadmapping
26. S akeholde analysis
Table based on based on Poppe [12]
The me hods wi hin o esigh a e o en selec ed by a mul i- ac o p ocess which is domina ed by
in ui ion, insigh , impulsi eness and some imes i esponsibili y and inexpe ience o p ac i ione s and
o ganize s. Addi ionally he choice o a me hod is also a ques ion o domain, R&D Con ex , e i o ial
7
scale, ime ho izon, sponso ship and a ge g oup [13]. Fo his wo k li e a u e e iew and in e iews
a e seen as adequa e me hods o ca y ou a o esigh analyses on ene gy s o age echnologies in
ame o he Ge man Ene gy u n o e .
8
3 Li e a u e e iew abou u u e ene gy scena ios and s o age
The li e a u e e iew is based on e-known s udies abou ene gy s o age in Ge many conduc ed in
ame o [14], [15]. In o al 9 la ge s udies ha e been e iewed and compa ed. Aim o he e iew was
o d aw a pic u e o u u e ene gy s o age demand un il 2050. Thus main a iables, scena ios and
model s uc u es we e b ie ly analyzed and summa ized, o dilu e he esul ing demand on ene gy
s o age echnologies in Ge many and o iden i y he main in luence pa ame e s ha s ee hei
de elopmen .
The named sou ces ange om 2010 o 2015 and a e a ailable o he public. The s udies a e in all
cases enowned sou ces om p i a e and esea ch ins i u ions in Ge many as e.g. he F aunho e
ins i u e. A b ie o e iew o he 9 s udies is gi en in able 2.
Table 2: O e iew abou e iewed li e a u e in he ield o ene gy s o age wi hin he Ge man Ene gy u n-o e
Au ho s
Ti le
Yea
Aim o he s udy
M. S e ne e .
Al
Ene giespeiche - Beda , Technologien, In eg a ion
2014
O e iew abou ene gy s o age echnologies and
ela ed scena ios om li e a u e
UBA / DLR
Lang is szena ien und S a egien ü den Ausbau
de E neue ba en Ene gien in Deu schland bei
Be ücksich igung de En wicklung in Eu opa und
global
2011
P o ides scena ios o enewable ene gy capaci y
de elopmen . illus a e he associa ed s uc u al
changes as well as demand o lexibili y op ions
Ago a
Ene giewende
S omspeiche in de Ene giewende - Un e suchung
zum Beda an neuen S omspeiche n in
Deu schland ü den E zeugungsausgleich,
Sys emdiens - leis ungen und im Ve eilne z21
2014
P o ide o e iew o po en ial ene gy s o age
demand scena ios, p oblems and po en ials as well
as echno-economic p ope ies o s o age
echnologies
SRU
Wege zu 100% e neue ba en S om e so gung:
Sonde gu ach en
2011
Illus a e he s uc u al changes o a 100 % RES
based ene gy sys ems wi h ela ed s o age demand
F. Genoese
Modellges ü z e Beda s- und
Wi scha lichkei sanalyse on Ene giespeiche n zu
In eg a ion e neue ba e Ene gien in Deu schland
2013
Analyze he echno-economic impac s o luc ua ing
elec ici y gene a ion on he Ge man powe g id
un il 2030 and he esul ing demand o ene gy
s o age echnologies
W.-P. Schill e
al
S omspeiche : eine wich ige Op ion ü die
Ene giewende
2015
Analyze long e m need o ene gy s o age
echnologies and compe i ion o o he echnologies
W.P. Schill
In eg a ion on Wind- und Sola ene gie:
Flexibles S omsys em e inge
Übe schüsse
2013
Analyze po en ial su pluses o enewable ene gy
gene a ion in ela ion o demand and ind op ions o
use hese
Aue and J.
Keil
Mode ne S omspeiche Un e zich ba e Baus eine
de Ene giewende
2012
Analysis o impac o enewable ene gy gene a ion
on g id and esul ing ma ke po en ial o ene gy
s o age echnologies
Pape e al.
Ene gieziel 2050:
100% S om aus e neue ba en Quellen
2010
Analyse measu es o achie e a g eenhouse gas
emission educ ion o 80 o 95 % in Ge many in a
economic iable way
Table based on [5], [7], [8], [9], [16], [17], [18], [19], [20]
All men ioned s udies don´ ha e he aim o p edic ing he u u e, hey a he c ea e a con ex in
which po en ial de elopmen pa hs can be isualised and discussed [5]. Mos impo an ly hey allow
i o iden i y o a ce ain deg ee po en ial consequences o di e en ansi ions pa hs o he ene gy
sys em o ene gy s o age espec i ely.
9
3.1 Ene gy S o age Technology o e iew
Ene gy s o age echnologies can gene ally be di ided in o; 1) mechanical: Pumped Hyd o-Elec ic
(PHS), Comp essed Ai Ene gy Sys ems (CAES), Flywheels; 2) elec ical; Supe Conduc ing Magne
Ene gy S o age; 3) he mal: hea s o age in ca e n o ocks, mol en sal ; 4) elec o-chemical sys ems:
ba e y sys ems and hyd ogen [21] [22]. S o age echnologies make i possible o inc ease sys em
eliabili y and lexibili y by decoupling demand and supply o elec ici y in a ime dimension. I has o
be men ioned ha ene gy s o age is seen as one po en ial balancing op ion among o he echnical
al e na i es as combined cycle gas u bines (CCGT), g id ein o cemen measu es (new AC o DC
ansmission lines), demand side managemen , Powe o X (e.g. o p oduce na u al gas o hyd ogen)
o gene a ion managemen o enewables wi hin he Ge man “Ene giewende”. Table 3 gi es a b ie
o e iew o he main cha ac e is ics o di e en s o age echnologies.
All s o age echnologies can be ca ego ized in ce ain applica ion ields in espec o hei ypical size
and s o age ime which a e namely: sho e m s o age om milliseconds o hou s, mid- e m s o age
up o 8 hou s and long – e m s o age including se e al days up o weeks [23]. These applica ion
possibili ies ha e di e en cos and echnologic ole ances, which highly a ec he applicabili y o
di e en s o age op ions.
Table 3: O e iew o 25% qua iles, median and 75% qua iles o di e en balancing op ions
Technology
E iciency
G a ime ic
ene gy
densi y
G a ime ic
powe
densi y
Cycles
Li e ime
In es men
cos
Commen
[%]
[Wh/kg]
[W/kg]
10^3
[a]
[€/kWh]
All
Vanadium
edox low
66-75-85
8.7-10-21
1-1.6-2.1
9-10-13.3
6.3-15-20
129-458-860
Cos is dependen on
applica ion
Li-Ion
( a ious)1
81-91-98
84-115-145
253-640-
1,300
0.73-2-8
7.5-15-20
453-745-
1,227
Mos common used
ba e y ype
Lead Acid2
63-76-90
23-33-37
3-27-53
0.3-1.6-
1.8
10-18-20
179-230-320
Mos ly used o ups
High
empe a u e
( a ious)3
75-86-90
120-148-158
113-160-196
2.8-3.6-
5.9
10-14-17.5
172-295-440
NaS and NaNiCl, he
la e is seen as sa e
and be e
Ni-based4
60-81-85
58-57-46
140-186-477
0.8-1.6-
2.5
7.1-12-13
290-1,200-
2,300
NiCd and NiMH old
gene a ion ba e ies
Pumped
hyd o
s o age
65-75-85
0.5-1-1.5
10-16-50
30-40-60
46-500
Dependen on geology
CAES
54-70-88
3.8-5-6
-
6-12-20
20-35-40
3-40-300
Dependen on geology
CCGT
54-60-63
-
-
-
20-30-40
680-900
[€/kW]
Al e na i e o s o age
Supe Caps
90-95-97.5
5.2-8.7-21.7
1.450-3,500-
1,0000
21-50-
100
10-15-20
570-1,463-
6,800
Ve y expensi e, only
iable o sho e m
applica ions
Table based on S enzel e al. [24] and Baumann e al. [25]
1 Summa y o LFP, NCA, NMC, LTO, LMC wi hou pe iphe ies (in e e , balance o plan e c.)
2 Summa y o VRLA and Flooded Lead acid ba e ies (in e e , balance o plan e c.)
3 Summa y on NaS and NaNiCl ba e ies (in e e , balance o plan e c.)
4 Summa y o NiCd and NiMH (in e e , balance o plan e c.)
16
Figu e 5: Po en ial demand o ins alled long- e m s o age capaci ies (>days h pe day) un il 2050; B) Po en ial ene gy
s o age demand (4 o 10 h pe day) un il 2050 including powe and capaci y, Sou ce: own igu e Sou ce: own based on [5],
[7], [8], [16], [17], [18]
3.6 Resul s o he Li e a u e e iew
The need o balancing op ions is highly dependen on he u he de elopmen o RES capaci ies in
Ge many. I has been shown ha Wind and PV a e he mos impo an ene gy sou ce in he u u e
wi h con ibu ions o o e 70 % on o e all elec ici y gene a ion in 2050. The sys em in eg a ion o
hese echnologies is challenging due o hei in e mi en na u e and cos s uc u e. T ansmission
g id ope a o s will ace s onge powe amps and highe amoun s o o ecas e o s in ace o a
dec easing numbe o lexible powe plan s. A he same ime ma ke condi ions a e highly a ec ed
by RES. The e is hus a s ong consensus wi hin li e a u e ha ene gy s o age echnologies on
di e en ime scales and sizes will be equi ed in he u u e. The ake-o o hese echnologies is
conside ed o be a e 2035, be o e his ime only low capaci ies a e equi ed (up o 3 GW).
Es ima ions o 2050 show a b oad pic u e o equi ed balancing capaci ies o abou 0 o 35 GW o
sho e m (up o 4 hou s) and 0 o 38 GW o mid- e m (o e 8 hou s) s o age ou o a ma ke

17
pe spec i e. Es ima ion in he ield o long e m s o age show e en highe a ia ions o 0 up o
44 GW un il 2050. I has been shown ha equi ed capaci y o long ime ho izons can be up o 10,2
TWh.
The p esen ed s udies a e hea ily dependen on da a (e.g. quan i a i e inpu s as ene gy, aw
ma e ials, ancilla y, physical o equi ed ope a ion condi ions, li e ime, main enance, cos e c.) and
e y ime complex. The a ailabili y o da a and he possibili y o quan i ying hem a e wo c i ical
aspec s. Mos assessmen s s a wi h ex apola ions o a ailable da a in o he u u e by he
de elopmen o scena ios (e.g. combina ion o lea ning cu es, economies o scale, linea upscaling
wi h da a om ma u e compa able sys ems e c.). Such scena ios ha e o be de eloped ca e ully and
ha e o deal wi h high unce ain y o da a and o hei o en poo a ailabili y. Addi ionally he
complexi y and dependency on angible ac o s and unce ain y a sys em analys ’s imagina ion migh
cause echnology o p oceed along a ce ain ajec o y (in he way a ocke ollows a ajec o y as
soon as i has been launched), based on a dominan socio- echnical egime (ma ke s uc u es,
echnology e c.) se ing as a base o modelling and esul p esen a ion. An example he e o e migh
be no ions abou wha he “ma ke ” (end use s) wan s and how new echnology migh be used (and
hus modelled wi hin i s use phase) 15. Bu , ma ke demand does no a icula e i sel in a
unambiguous and quan i a i e way [39]. The a icula ion o ex apola ions and “dynamics as usual” is
hus p oblema ic as ma ke s e ol e.
15 All he analyzed ene gy ma ke s udies can be named he e as he e a e based on he me i o de model,
including he ypical way o ma gin cos calcula ion nowadays
18
4 Visions abou he powe sys em and ene gy s o age
The mo i a ion o conduc in e iews in his esea ch was o ob ain a deepe insigh in o
s akeholde ´s expec a ions and isions hey ha e o he u u e use on ene gy s o age sys ems
beyond hose communica ed in he e iewed s udies. Semi-s uc u ed in e iews a e explo ed o
p o ide su icien s uc u e as well as lexibili y o ackle his ask.
4.1 S akeholde in ol emen : Semi-s uc u ed in e iews
The in e iews we e conduc ed in ame o a p e- es phase o a online su ey in he ame o a PhD
p ojec on ene gy s o age [14]. The named su ey was ini ially dis ibu ed wi h indi idual mails o 22
expe s om he a ea o ene gy s o age and powe sys ems. The i s con ac b ie ly in oduced he
opic o he su ey and po en ial in e iew. The mail s essed ha he aim is o ge a c i ical eedback
on he su ey as well as o ga he gene al expec a ions abou ene gy s o age. Candida es we e also
asked i hey a e willing o pa icipa e on ollow-up in e iews. In o al 13 ex e nal expe s esponded
p o iding a ious commen s and hough s on he opic. F om hese 10 candida es we e willing o
pa icipa e in an in e iew. An o e iew o he pa icipan s and way o in e iew is gi en in able 5.
Table 5: O e iew o in e iew ac o s
S akeholde
index
Company/O ganiza ion
P o ession
Commen
P 1 RE
P i a e Resea ch Ins i u e
Head o Ene gy depa men
Via elephone, ~40 minu es, no es
P 2 U
U ili y company
Head o depa men
Via elephone, ~50 minu es, no es
P 3 RES
RES Sys emin eg a o
Senio ope a ion se ices
Via elephone, ~115 minu es, no es
P4 U
U ili y company
Senio consul an
Via elephone, ~40 minu es, no es
P 5 U
U ili y company
Head o ene gy s o age p ojec
de elopmen
Via elephone, ~50 minu es, no es
P 6 Reg.
Regula ion agency
Expe o he depa men o RES and ene gy
e iciency
Via elephone, ~90 minu es, no es
P 7 Au o
Au omo i e
Vice head o p ojec managemen
Via elephone, ~80 minu es, no es
P 8 ES
Ene gy s o age business
P ojec managemen
Via elephone, ~90 minu es, no es
P 9 Ac
R&D Uni e si y
P incipal in es iga o ene gy s o age
esea ch
Pe sonal, ~80 minu es, no es
P10ConPol
Ene gy Policy consul ing
Consul an & P o esso @ Uni .
Via Telephone ~20 min, no es
The in e iews we e conduc ed mos ly ia elephone due o he la ge physical dis ance o he
candida es. Only one pe sonal in e iew was conduc ed wi h a pa icipan wo king in he same ci y.
Each in e iew had du a ion be ween 30 o 100 minu es and was conduc ed one o one. As
men ioned be o e candida es we e amilia wi h he o e a ching ques ions o he in e iew as hey
we e p o ided in ad ance h ough he su ey. The ques ions we e no ollowed s ic ly, bu hey
p o ided a s uc u e o he indi idual de elopmen o each in e iew. I was a anged ha he
ma e ial will be used in an anonymized o m wi hou di ec quo a ion.
19
Hand no es we e conduc ed wi h he ul e io mo i e o a oid gua ded esponses and maybe sel -
consciousness as in he case o eco dings [5]. None o he pa icipan s e used his p ocedu e. No es
we e ansc ip di ec ly a e he inqui y and included only he mos impo an poin s o he
in e iews. This phase has led o u he al e a ions o he su ey and o e ed aluable addi ional
quali a i e in o ma ion abou he ques ions aised.
4.2 S akeholde expec a ions on he u u e ene gy sys em
Mos o he pa icipan s belie e in a success o he ene gy u n o e [P5U, P3RES, P9AC, P1RE].
Though he e a e doub s abou he magni ude o RES sha es and conce ns abou missing s a egies
o achie e hem on a policy and egula ion le el. The issue o egula ion was o en connec ed o he
Ge man Renewable Ene gy Ac (Gese z zu Fö de ung e neue ba e Ene gien –EEG). The EEG is
conside ed as a key in he ansi ion, in he sense ha i should a ibu e a highe deg ee o pe sonal
esponsibili y o RES asse owne s. Especially egula ion o esiden ial s o age16 and he obliga ion o
(mo e) di ec ma ke ing o RES17 [P5U] we e named as c ucial aspec s.
Pa icipan P10ConPol s a ed ha he ma ke impac s o RES a e well unde s ood. Mos s udies in
he las 5 yea s go in line abou he e ec s o RES on wholesale ma ke s. This can be alida ed
h ough he conduc ed li e a u e e iew which showed ha a lo o s udies a e a ailable. In his
con ex some ac o s claimed ha a ailable ene gy models don´ accoun changes in ma ke design
and wide echnology use and may sys ema ically unde es ima e s o age echnologies. S akeholde
P5U claimed ha ma ke models ha e a sho alidi y due o he ac ha i is unclea i ma ke
clea ing p ices and ma gin cos s will be calcula ed he same way in 2030. In e iew esul s ha e led
o he imp ession ha pa icipan s ag ee ha RES impac s on sys em sa e y a e o a ce ain deg ee
sys ema ically unde es ima ed. P oblems named in his con ex whe e high dispa ch cos s and g id
conges ions. This is on he one hand based on he logics o applied ene gy models ha use a “coppe
pla e” g id app oach and don´ conside his e ec s [P10ConPol]. Fu he mo e sho e m
luc ua ions a e also no p ope ly conside ed as mos ly hou ly ime s eps a e used in mos modeling
app oaches [P5U]. On he o he hand RES g ow h was unde es ima ed in he las 5 yea s.
T ansmission g id ope a o s did no an icipa e he amoun o g id conges ions and dispa ch cos s
ela ed o he sys em in eg a ion o wind and PV [P10ConPol].
Li e a u e poin s ou ha u u e ene gy sys ems will be highly decen alized [5], [8] o e ing new
po en ials o ene gy s o age, especially ba e y sys ems [41], [8]. The nex ques ion hus aimed o
ind ou o how s ongly ac o s ag ee ha he ene gy sys em will be s ongly decen alized. The e
was a s ong consensus in a o o his s a emen among he in e iewees P9Ac, P3RES, P4U.
In e iewee P5U exp essed his app o al as ollows:
… he u u e sys em will become mo e small sized […] wi h a highe deg ee o indi idual
esponsibili y18 […] and mo e bene i s on a local le el […] end use s ha e o be in eg a ed in a
s onge way […] only his and no egula ion i sel enables he in eg a ion o balancing measu es as
ba e ies, demand side managemen and o he s..”
16 See e.g. §§ 118 Abs.6 and 60 Abs. o he 3 EEG – egula ions o esiden ial s o age
17 This is al eady obliga o y o all new RES gene a ion uni s >500 kW s a ing om Janua y 1s 2016 [40]
18 In he con ex o local ene gy consump ion and egula ion
20
I has o be men ioned ha his change is seen un il 2050. Some pa icipan s belie ed ha he e will
be a balance o cen al mul i MW and small mul i kW powe plan s un il he 2030ies. La ge
in es men s in he ield o GW uni s a e old o s ongly dec ease in he u u e [P6Reg] and
[P10ConPol].
4.3 Expec a ions on u u e ene gy s o age di usion
The in e iews showed ha all pa icipan s ag ee ha he e will be o a ce ain deg ee a need o
ene gy s o age in he u u e Ge man ene gy g id. The alidi y o a ailable s udies es ima ing he
need o s o age was also add essed in he in e iews in e ms o made ma ke assump ions [P5U]
and conside ed business models [P2U] and [P7Au o]. Candida es claimed ha he e al eady exis
se e al echnologies, bu ha he e is no business case a ailable making i ha d o make any obus
es ima ions. The alue o ene gy s o age canno be di ec ly alloca ed o one ac o as he e a e
se e al bene icia ies o se ices p o ided (e.g. ene gy s o age uni in combina ion wi h a wind ene gy
di ec ma ke ing leading o ansmission and Dis ibu ion upg ade de e al (T &D upg ade)). This is
p oblema ic as he in es men in o s o age is conduc ed by one pa y bu alue s eams a ec
mul iple ac o s and emain unclea . Thus s o age se ices p o ided ha e o be acco dingly ewa ded
which is no he case nowadays [P7Au o]. The in eg a ion o hese alues should gene a e a mo e
e icien sys em app oach. Especially new sys em concep s as i ual powe plan s o e comple ely
new business possibili ies o scalable ba e y s o age [P5U]. The p oblem is ha he composi ion o
hese concep s i sel is conside ed o be in hei in ancy and emain blu y.
The e was no consensus abou he amoun o kind o balancing op ions needed un il 2050 as
exp essed h ough [P1RE, P2U, P4U, P8ES]. They also s essed ha balancing does no ha e o be
co e ed by ene gy s o age as he e a e se e al o he op ions a ailable [P1RE, P2U, P4U]. S akeholde
P5U did no ag ee o he ime ame a e 2035 and hinks ha lexibiliza ion op ions will be equi ed
ea lie due o sys em sa e y issues s a ing a a RES sha e a ound 40 %19. Candida es as P4U and P1RE
ag eed ha i is in gene al di icul o make eliable p edic ions o single echnologies. P1RE poin ed
his ou as ollows:
“…no clea how much balancing equi ed [...] i is impossible o gi e obus s a emen s abou single
echnologies […] no impo an as he e will be a mix o di e en lexibiliza ion echnologies”
P4U added ha he speci ic echnology is no o in e es ou o ene gy economic pe spec i e. The
in e es is mo e nes ed in he bigge con ex wi h a gene al iew on s o age and no on single
echnologies. The in e iews showed ha he e is a lo discussion wi hin he communi y ega ding
he need o s o age on all le els [P1RE, P2U, P4U, P5U, P7Au o, P8ES]. I was also poin ed ou ha
ene gy s o age is only one o ou possible balancing echnologies which a e namely: 1) G id
ein o cemen measu es, 2) lexible demand, 3) lexible powe plan s and a he end o he line 4)
elec ic ene gy s o age. The la e is seen as oo expensi e in ela ion o he o he op ions [P8ES]
19 This would e e o he yea 2025 ega ding he analysed s udies in chap e XX
21
[P10ConPol]. One s akeholde also exp essed conce ns abou he s ong willingness o policy o
suppo ene gy s o age p ojec s due o he ac ha hey migh “be on he w ong ho se”
[P10ConPol].
In gene al all 4 named balancing op ions a e seen as impo an o a ce ain deg ee. Some measu es
a e conside ed as mo e in e media e solu ions as ansmission g id ex ension and lexible powe
plan s [P8ES]. A majo p oblem ega ding demand side esponse (DSM) a e p oblems ega ding
accep ance. The issue o accep ance is ein o ced by he low accep ance o he equi ed sma
me e s o DSM and ela ed cos s nowadays. This was especially poin ed ou o indus y ega ding
he ea o losing o a ce ain deg ee con ol o e hei p oduc ion [P7Au o]. The e is only seen a
small po en ial o DSM in he end-use ma ke s due o missing business cases and small p o i
ma gins [P6RES], [P5U]. One excep ion was men ioned by he use o wall boxes o conduc DSM wi h
elec ic ehicles [P7Au o].
The po en ial o la ge, cen alized ene gy s o age especially PHS is iewed as c i ical due o se e e
accep ance p oblems o he public agains new p ojec s and high en i onmen al legal cons ain s. A
he same ime hey a e claimed o be he only economic iable op ion a ailable nowadays acing an
inc easing cos p essu e om ma ke s [P10ConPol]. Exis ing PHS a e al eady ope a ing a he b ink o
being economic iable [P8ES]. The echnology may se e as a backbone o sys em s abili y in
combina ion wi h decen alized s o age op ions in he u u e [P10ConPol]. O he echnologies
named in he con ex o cen alized ene gy s o age we e powe o gas and hyd ogen.
G id ex ension is pe cei ed as elemen al o he success o he Ene giewende. Despi e he need o i
mos candida es a gued ha his op ion is highly unpopula wi hin popula ion [P3RES], [P7Au o],
[P5U]. This was s essed in almos all in e iews. The op ion o building new lexible powe plan s
(e.g. gas- u bine) is seen as unp oblema ic ega ding local accep ance [P6Reg]. This is su p ising as
hey also ep esen a cen alized echnology wi h a ce ain impac on landscape and ai quali y. I
was howe e s a ed ha he echnology is well known o i s sa e y and ha is ela i ely cheap in
ela ion o o he op ions.
Modula echnologies as ba e y s o age a e seen as impo an o ce ain applica ions especially o
sho - e m applica ions as equency egula ion. Mos in e iewees doub ed ha ba e y echnology
can compe e wi h any o he gi en al e na i es due o hei bad compa able economic pe o mance.
Thus pa icipan s pe cei e hem as no ha ele an o he yea s o come [P3RES], [P8RES] and
[P10ConPol].
The alue o ba e y s o age canno be di ec ly alloca ed o one ac o as he e a e se e al
bene icia ies o se ices p o ided (e.g. ba e y s o age in combina ion wi h a wind ene gy di ec
ma ke ing leading o ansmission and Dis ibu ion upg ade de e al (T&D upg ade)). This is
p oblema ic as he in es men in o s o age is conduc ed by one pa y bu alue s eams a ec
mul iple ac o s and emain unclea . Thus s o age se ices p o ided ha e o be acco dingly ewa ded
which is no he case nowadays [P7Au o]. The in eg a ion o hese alues should gene a e a mo e
e icien sys em app oach. Especially new sys em concep s as i ual powe plan s o e comple ely
new business possibili ies o scalable ba e y s o age [P5U]. The p oblem is ha he composi ion o
hese concep s i sel is conside ed o be in hei in ancy and emain blu y.

22
4.4 Resul s o he semi-s uc u ed in e iews
S akeholde s belie e in he success o he Ene giewende, bu a e no in line o how o ge he e. The
need o balancing echnologies is highly discussed, no in he sense i hey a e equi ed bu when and
in which amoun . I can be dilu ed om he inqui y ha changes in he a chi ec u e o he ene gy
sys em owa ds a mo e decen alized sys em and lowe la ge scale in es men migh ep esen a big
oppo uni y o s o age in he mid- (2035) o long- e m (2050). The e is a high deg ee o consensus
among pa icipan s ha RES impac s a e unde -es ima ed no on ma ke le el bu on a sys em le el
a e. Majo issues in his con ex a e missing egula ions wi hin he EEG, whole-sale ma ke s uc u e
and he loss o an o e a ching s a egy o achie e he Ene giewende).
Ene gy s o age is seen as one op ion among: 1) G id ein o cemen measu es, 2) lexible demand, 3)
lexible powe plan s and a he end o he line 4) elec ic ene gy s o age in economic e ms. Op ion
1 and 3 a e seen as in e media e measu es wi h a dec easing impo ance in he u u e. Flexibili y
measu es as Demand Side managemen is seen highly c i ical due o accep ance and cos o sma
me e s. Mos s akeholde don´ see a big po en ial o cen alized la ge ene gy s o age echnologies.
The su ey a ibu es a high ele ance o modula echnologies as ba e y sys ems. In e iews ha e
shown ha hey a e seen as one o he mos expensi e echnologies wi hin he segmen o ene gy
s o age echnologies. I was concluded ha no business case a e a ailable making i ha d o make
any obus es ima ions abou single echnologies.
23
5 Conclusion and discussion
The es ima ions o e iewed s udies a e based on echno-economic linea op imiza ion models wi h
he goal o minimizing o e all sys em cos s wi h a ma ke based pe spec i e on ene gy s o age
demand. Only ew s udies conside sys em based demand o s o age on mul iple ol age le els. Mos
model based scena ios a e buil on op down logics, whe e p ocesses a lowe le els ( echnology,
mic o-economic sphe e) a e de e mined by dominan mac o dynamics (exis ing ma ke mechanisms,
business models). Di e en echnologies a e only conside ed pa ially o in an agg ega ed way. The
e iewed s udies showed ha he e can be a high po en ial s o age on e e y ime scale in gene al
s a ing om he yea 2030 o 2040. Analyzed po en ial in he s udies a y depending on assump ion
be ween 0 o 44 GW.
The s udies s ongly in eg a e sha ed isions abou sys em de elopmen s and o mal analyses and
p o ide impo an and aluable in o ma ion abou po en ial u u e implica ions. These app oaches
o en only pa ially accoun , due o p ac ical easons, wide bene i s (sys em sa e y, en i onmen al
and social impac s e c.), s akeholde opinions, sus ainabili y condi ions and con inuous changes as
well as discon inui ies in he echnological inno a ion p ocess [36] [42]. S akeholde in e iews hus
p o ided addi ional and help ul insigh s o he li e a u e e iew. S akeholde s amed po en ial
u u e scena ios ha could in luence he ma ke success and need o ene gy s o age un il 2050.
Mos impo an ac o s named whe e policy measu es and decen aliza ion o he ene gy sys em.
The e is a big unce ain y abou he igh s o age echnology and i ene gy s o age is in gene al he
bes op ion among o he measu es as g id ein o cemen , lexible demand and lexible powe plan s.
In gene al i appea s he expec a ions and isions o s akeholde s ega ding ene gy s o age s ongly
co ela e wi h he se o s udies e iewed20.
20 This unde pins ha decisions, public deba es and policies ela ed o ene gy s o age a e o en explici ly o
implici ly based on hese modeling g ounded s udies as [8], [18] and [16].
24
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