Technology-Agnostic Assessment of Wave Energy System Capabilities



Ci a ion: Ruiz-Minguela, P.; Blanco,
J.M.; Na a, V.; Je ey, H.
Technology-Agnos ic Assessmen o
Wa e Ene gy Sys em Capabili ies.
Ene gies 2022,15, 2624. h ps://
doi.o g/10.3390/en15072624
Academic Edi o : Ma co To esi
Recei ed: 17 Ma ch 2022
Accep ed: 30 Ma ch 2022
Published: 3 Ap il 2022
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ene gies
A icle
Technology-Agnos ic Assessmen o Wa e Ene gy
Sys em Capabili ies
Pablo Ruiz-Minguela 1,2,* , Jesus M. Blanco 1,2 , Vincenzo Na a 1,3 and Hen y Je ey 4
1TECNALIA, Basque Resea ch and Technology Alliance (BRTA), As ondo Bidea, Edi icio 700, 48160 De io,
Spain; [email p o ec ed] (J.M.B.); [email p o ec ed] (V.N.)
2School o Enginee ing, Uni e si y o he Basque Coun y, Plaza Ingenie o To es Que edo, 1,
48013 Bilbao, Spain
3Basque Cen e o Applied Ma hema ics (BCAM), Alameda de Maza edo 14, 48009 Bilbao, Spain
4Ins i u e o Ene gy Sys ems, School o Enginee ing, The Uni e si y o Edinbu gh, Edinbu gh EH9 3JG, UK;
hen y.je [email p o ec ed]
*Co espondence: jpablo. [email p o ec ed]
Abs ac :
De eloping new wa e ene gy echnologies is isky, cos ly and ime-consuming. The la ge
di e si y o concep s, componen s and e alua ion c i e ia c ea es a as design space o po en ially
easible solu ions. This pape aims o in oduce a no el me hodology o he holis ic assessmen
o wa e ene gy capabili ies in a ious ma ke applica ions based on sound Sys ems Enginee ing
me hods. The me hodology p o ides a consis en hie a chy o pe o mance me ics ele an o he
gi en sys em o e e ence, design ac i i y and de elopmen s age unde conside a ion as a means
o sc u inise wa e ene gy equi emen s. Full aceabili y o sys em equi emen s and pe o mance
me ics is hen acili a ed by mul i-c i e ia decision ools and agg ega ion logic, espec i ely. The
quali a i e assessmen in he case s udies has esul ed in e y di e en ankings o Sys em D i e s and
S akeholde s o he wo ma ke applica ions conside ed. Howe e , he S akeholde Requi emen s
and Func ional Requi emen s p esen a small a ia ion in he weigh s o he wo applica ion ma ke s
which esul s in a quan i a i e assessmen wi h e y simila Global Me i . Finally, he pe o mance
benchma k using he Comme cial A ac i eness and Technical Achie abili y concep s enables a mo e
objec i e compa ison in he u ili y-scale and emo e gene a ion ma ke s and a way o concen a e
inno a ion e o s be o e p oceeding o he nex de elopmen s age.
Keywo ds:
comme cial a ac i eness; design domains; d i e s; me ics; equi emen s; s akeholde s;
sys ems enginee ing; echnical achie abili y; echnology-agnos ic
1. In oduc ion
Wa e ene gy has a ac ed he in e es o many in en o s o mo e han wo cen u ies.
Since he i s eco ded pa en in 1799 [
1
], enginee s ha e s uggled o un a el he key
equi emen s o wa e ene gy echnologies. Howe e , i was no un il he ea ly 1970s
ha he ma hema ical o mula ion o wa e ene gy in e ac ion allowed us o unde s and
he cap u e e iciency o ma ine de ices [
2
]. The i s a emp o de i e a pe o mance
assessmen o wa e ene gy echnologies was p oposed by Nielsen [
3
]. Sugges ions included
a ios such as he Cap u e Wid h, Ene gy o Volume o Mass, Powe Take-O E iciency,
Capaci y Fac o and Capi al Cos o Ene gy. The Eu opean p ojec EQUIMAR [
4
] added
o he assessmen igu es o hese me ics such as he Ope a ing Cos , A ailabili y Fac o
and LCOE. Ini ial wo k om Webe [
5
] on he Technology Pe o mance Le els (TPL) has
been con inued in he US o e ol e and endo se he TPL design philosophy, assessmen
c i e ia and me hods [
6
]. Mo e ecen ly, IEA-OES has p omo ed an in e na ional e alua ion
and guidance amewo k o ocean ene gy echnologies based on he concep o s aged
de elopmen [
7
]. S ages a e loosely ela ed o he Technology Readiness Le el (TRL) scale,
Ene gies 2022,15, 2624. h ps://doi.o g/10.3390/en15072624 h ps://www.mdpi.com/jou nal/ene gies
Ene gies 2022,15, 2624 2 o 30
and a each s age-ga e, an e alua ion o he ele an me ics is ca ied ou . The i s -o -i s-
kind implemen a ion o his amewo k has been p oduced in he DTOceanPlus sui e o
design ools o ocean ene gy sys ems [8].
Clea ly, pe o mance equi emen s a e mo ing om he me e e alua ion o he ene gy
p oduc ion and cos s o a mo e comp ehensi e assessmen . Equally, he e alua ion is
e ol ing om he analysis o he basic wa e ene gy subsys ems in ol ed in he powe
con e sion o comple e wa e ene gy a ms including mul iple de ices, he balance o
plan o ins alla ion and main enance ac i i ies. Discou agingly, mos o he no el wa e
ene gy concep s a e s ill ocusing hei e o s on he op imisa ion o powe cap u e, lea ing
ou o he ini ial design conside a ions o o he essen ial pe o mance equi emen s and
subsys ems ha la e become expensi e “add-ons” [
9
]. In ac , expe ience in e y di e se
enginee ing sec o s has shown ha he ea ly s ages o echnology de elopmen a e c ucial
o mee cos and pe o mance expec a ions [
10
] since enginee ing p oblems a e buil a he
concep s age.
The de elopmen o a compe i i e wa e ene gy echnology is a long endea ou aced
wi h many challenges. The inc eased complexi y o he assessmen s coupled wi h he la ge
di e si y o concep s calls o comp ehensi e de elopmen and e alua ion me hods. Hence,
echnology de elope s a e encou aged o mo e o an in eg a ed sys ems app oach [
9
]. In
ha espec , Sys ems Enginee ing (SE) p o ides a sui able amewo k o allow p og ess
owa ds a success ul wa e ene gy echnology [11].
SE is a holis ic, op-down app oach o unde s anding s akeholde needs, explo ing
oppo uni ies, documen ing equi emen s and assessing al e na i es while conside ing he
whole p oblem [
12
]. SE me hods ha e been success ully applied in many indus ial sec o s
(e.g., au omo i e, ae ospace o oil and gas among o he s) o de elop inno a i e p oduc s
mee ing e y di e se and demanding s akeholde needs. Reg e ably, he applica ion o SE
o wa e ene gy has been much limi ed and agmen ed so a [13].
A ho ough and sys ema ic design p ocess should p o ide enginee s wi h e ec i e
means o o ganising in o ma ion on sys em equi emen s and disc imina ing i om he
in o ma ion associa ed wi h design solu ions [
14
]. Sys em equi emen s should be speci ied
a di e en le els o de ail (o hie a chy) and be ully aceable h oughou he design
p ocess [
15
]. Mo eo e , since he sa is ac ion o equi emen s is he d i ing o ce behind
SE, e alua ion and decision making mus ely on he use o well-de ined and a icula ed
me ics. Finally, he sys ema ic assessmen should be lexible and adap able o changing
ma ke condi ions and s akeholde expec a ions, as hey de ine he ela i e impo ance o
indi idual equi emen s and he e o e he solu ion space.
This pape aims o in oduce a no el echnology-agnos ic me hodology o he holis ic
assessmen o wa e ene gy capabili ies o a ious ma ke applica ions. Each o hese
capabili ies has been cha ac e ised by a unc ion and i s le el o pe o mance, ollowing
he app oach in [
16
]. The co e con ibu ion o his me hodology is o p o ide a consis en
hie a chy o pe o mance me ics ele an o he sys em o e e ence, design ac i i y and
de elopmen s age unde conside a ion as a means o sc u inise wa e ene gy equi e-
men s. Full aceabili y o sys em equi emen s and pe o mance me ics is hen acili a ed
by mul i-c i e ia decision ools and agg ega ion logic, espec i ely. Finally, cus omisa-
ion o assessmen c i e ia h esholds o he ma ke -speci ic condi ions enables a obus
benchma king o di e en wa e ene gy echnology op ions as well as he iden i ica ion o
ou s anding echnical challenges, as will be explained in Sec ion 2.3.
Two new concep s, comme cial a ac i eness and echnical achie abili y, a e in o-
duced and illus a ed h ough case s udies. Assuming he p ima y p oduc o wa e ene gy
is likely o be elec ici y gene a ion [
17
], he case s udies ocus on he u ili y-scale gene a ion
and powe ing emo e communi ies’ ma ke s. Hence, his no el app oach con ibu es o
o e coming he limi a ions o pu e quali a i e o quan i a i e e alua ing me hods as well
as allows acking he educ ion in echnical isks along he a ious de elopmen s ages by
means o he pe o mance a io alues.
Ene gies 2022,15, 2624 3 o 30
The ou line o his a icle is as ollows. Sec ion 2in oduces he me hodology and
main SE me hods and ools used o he assessmen o wa e ene gy capabili ies. Sec ion 3
desc ibes he speci ic implemen a ion o his no el me hodology in he en i onmen al,
s akeholde and unc ional domains. Fu he mo e, he esul s o wo di e en ma ke
applica ions o wa e ene gy echnologies a e p esen ed and discussed in Sec ion 4, be o e
d awing he conclusions in Sec ion 5. Finally, he p io i isa ion o he di e en domain
a ibu es o he case s udies along wi h hei espec i e in e ac ions is included in he
Appendix A.
2. Ma e ials and Me hods
The p oposed e alua ion app oach consis s o sys em analysis, a quali a i e assess-
men and a pe o mance benchma k (i.e., quan i a i e assessmen ) as shown in Figu e 1.
This me hod me ges he enginee ing design and alida ion ac i i ies oge he wi h mul i-
c i e ia decision-making and benchma king. Hence, i enables a comp ehensi e e alua ion
o wa e ene gy echnologies a a ious de elopmen s ages. I is impo an o highligh he
inhe en lexibili y o he p oposed me hod. Fo ins ance, he e alua ion app oach can be
expanded by adding mo e g anula i y, i.e., ine le els o de ails, as he echnology ma u es,
o he design ocus (i.e., sys em o e e ence) shi s om he a m and de ice o subsys em
le els.
Ene gies 2022, 15, x FOR PEER REVIEW 3 o 30
The ou line o his a icle is as ollows. Sec ion 2 in oduces he me hodology and
main SE me hods and ools used o he assessmen o wa e ene gy capabili ies. Sec ion 3
desc ibes he speci ic implemen a ion o his no el me hodology in he en i onmen al,
s akeholde and unc ional domains. Fu he mo e, he esul s o wo di e en ma ke
applica ions o wa e ene gy echnologies a e p esen ed and discussed in Sec ion 4, be o e
d awing he conclusions in Sec ion 5. Finally, he p io i isa ion o he di e en domain
a ibu es o he case s udies along wi h hei espec i e in e ac ions is included in he
Appendix A.
2. Ma e ials and Me hods
The p oposed e alua ion app oach consis s o sys em analysis, a quali a i e assess-
men and a pe o mance benchma k (i.e., quan i a i e assessmen ) as shown in Figu e 1.
This me hod me ges he enginee ing design and alida ion ac i i ies oge he wi h mul i-
c i e ia decision-making and benchma king. Hence, i enables a comp ehensi e e alua-
ion o wa e ene gy echnologies a a ious de elopmen s ages. I is impo an o high-
ligh he inhe en lexibili y o he p oposed me hod. Fo ins ance, he e alua ion ap-
p oach can be expanded by adding mo e g anula i y, i.e., ine le els o de ails, as he
echnology ma u es, o he design ocus (i.e., sys em o e e ence) shi s om he a m and
de ice o subsys em le els.
Figu e 1. P oposed assessmen app oach.
The ollowing sub-sec ions desc ibe he h ee componen s o he sys ema ic design
app oach o wa e ene gy echnologies. Fu he mo e, he quali a i e assessmen and pe -
o mance benchma k a e illus a ed h ough a se o case s udies comp ising wo di e en
ma ke applica ions o wa e ene gy echnologies and six hypo he ical echnology op ions.
2.1. Sys em Analysis: Requi emen s, Me ics and Sys em o Re e ence
Despi e he ela i ely sho his o y o SE, hei p ac i ione s ha e p oduced a weal h
o me hods and ools ha se e di e en pu poses. As a as sys em analysis is conce ned,
i is wo h men ioning he Axioma ic Design echnique [18], which s uc u es he wo ld
o design in sepa a e domains. The concep o design domains is e y e ec i e o o ganise
he design p ocess by in oducing bo de lines be ween a ious ypes o design ac i i ies
o he de elopmen o wa e ene gy echnologies. Thus, he wa e ene gy p oblem is ep-
esen ed di e en ly depending on he co esponding design domain. An associa ed
model is a ached o each design domain aiming o cap u e domain-speci ic in o ma ion.
Di e en domain models can be used o ep esen he wa e ene gy sys em depend-
ing on he le el o abs ac ion and deg ee o de ail [19]. A ull desc ip ion o he domain
amewo ks p oposed by a ious au ho s can be ound in [13]. Cu en ly, he e is a lack
o consensus on he de ini ion o he domains ha a e common o all enginee ing p ojec s.
Howe e , exis ing amewo ks o en limi hei use o a maximum o h ee o ou do-
mains.
The p oposed assessmen me hod will map he en i onmen al, s akeholde and unc-
ional domains (see Figu e 2). The ansi ion om le o he igh illus a es he enginee ’s
Figu e 1. P oposed assessmen app oach.
The ollowing sub-sec ions desc ibe he h ee componen s o he sys ema ic design
app oach o wa e ene gy echnologies. Fu he mo e, he quali a i e assessmen and
pe o mance benchma k a e illus a ed h ough a se o case s udies comp ising wo
di e en ma ke applica ions o wa e ene gy echnologies and six hypo he ical echnology
op ions.
2.1. Sys em Analysis: Requi emen s, Me ics and Sys em o Re e ence
Despi e he ela i ely sho his o y o SE, hei p ac i ione s ha e p oduced a weal h
o me hods and ools ha se e di e en pu poses. As a as sys em analysis is conce ned,
i is wo h men ioning he Axioma ic Design echnique [
18
], which s uc u es he wo ld o
design in sepa a e domains. The concep o design domains is e y e ec i e o o ganise
he design p ocess by in oducing bo de lines be ween a ious ypes o design ac i i ies
o he de elopmen o wa e ene gy echnologies. Thus, he wa e ene gy p oblem is
ep esen ed di e en ly depending on he co esponding design domain. An associa ed
model is a ached o each design domain aiming o cap u e domain-speci ic in o ma ion.
Di e en domain models can be used o ep esen he wa e ene gy sys em depending
on he le el o abs ac ion and deg ee o de ail [
19
]. A ull desc ip ion o he domain
amewo ks p oposed by a ious au ho s can be ound in [
13
]. Cu en ly, he e is a lack o
consensus on he de ini ion o he domains ha a e common o all enginee ing p ojec s.
Howe e , exis ing amewo ks o en limi hei use o a maximum o h ee o ou domains.
The p oposed assessmen me hod will map he en i onmen al, s akeholde and unc-
ional domains (see Figu e 2). The ansi ion om le o he igh illus a es he enginee ’s
syn hesis ac i i y o achie e an e ec i e design ha sa is ies he equi emen s. The op-
posi e way e eals he enginee ’s analysis ac i i y suppo ing e i ica ion and alida ion.
Ene gies 2022,15, 2624 4 o 30
Al hough shown in he g aph o he sake o comple eness, he physical domain is ou
o he scope o his pape since i aims o p oduce a echnology-agnos ic assessmen o
wa e ene gy sys em capabili ies and no a speci ic physical embodimen o se o Technical
Requi emen s (TR).
Ene gies 2022, 15, x FOR PEER REVIEW 4 o 30
syn hesis ac i i y o achie e an e ec i e design ha sa is ies he equi emen s. The oppo-
si e way e eals he enginee ’s analysis ac i i y suppo ing e i ica ion and alida ion.
Al hough shown in he g aph o he sake o comple eness, he physical domain is ou o
he scope o his pape since i aims o p oduce a echnology-agnos ic assessmen o wa e
ene gy sys em capabili ies and no a speci ic physical embodimen o se o Technical Re-
qui emen s (TR).
Figu e 2. Domains o he design wo ld (adap ed om [13]).
The en i onmen al domain deals wi h he ex e nal ac o s ha impac he wa e en-
e gy sys em. This domain is de ined by Sys em D i e s (SD) and hei in e ac ions [20].
SD encompass he poli ical, economic, social, echnical, legal and en i onmen al ac o s
ha limi , acili a e o shape he design solu ion. The s akeholde domain de ines he de-
sign p oblem in he cus ome ’s language, which is s ill gene al, ambiguous and highly
unmeasu able [21]. I is ep esen ed by he S akeholde Requi emen s (SR), which a e a
se o desi able cha ac e is ics ha he inal solu ion should sa is y. Finally, he unc ional
domain aims o p oduce a comple e, unambiguous and echnology-agnos ic de ini ion o
he design p oblem space [22]. Func ions desc ibe he pu poses o he wa e ene gy sys em
and Func ional Requi emen s (FR) and speci y wha he sys em mus do in o de o
achie e he SR [20].
Once he c i ical sys em p ope ies a e es ablished in he o m o wa e ene gy sys em
equi emen s, e alua ion c i e ia a e assigned o o e a c edible means by which o assess
a ious design op ions. Me ics linked o he uppe sys em a ibu es (i.e., SR) a e usually
e e ed o as Measu es o E ec i eness (MOE). They a e educed in numbe since he
lowe le el e alua ion me ics a e successi ely de i ed om hem [23]. Measu es o Pe -
o mance (MOP) a e used o gauge he FR o a design solu ion, whils Technical Pe o -
mance Measu es (TPM) a e used o demons a e success ul deli e y o he TR. MOP a e
echnology-agnos ic, and aceabili y should be main ained bo h h oughou he decom-
posi ion p ocess and wi h ega d o he highe -le el MOE. This hie a chy o e alua ion
c i e ia ensu es a holis ic assessmen ha cap u es di e en le els o de ail and g anula -
i y in he me ics. I is wo h no ing ha he concep o design domains coupled wi h his
undamen al hie a chy o e alua ion c i e ia is also consis en wi h he basic design p o-
cesses in he V-model [24], a well-known SE app oach.
Since any wa e ene gy sys em can be successi ely decomposed in o smalle en i ies,
he syn hesis and analysis ac i i ies can be u he expanded by epea ing he domain
mapping p ocess o each subsys em, assembly o componen . Rega dless o he sys em
scope unde conside a ion, i is essen ial o iden i y he en i ies ha in e ac wi h i ia he
sys em’s ex e nal in e aces (i.e., Ex e nal Sys ems) and he wide en i onmen whe e he
sys em is placed (i.e., Con ex ). The Ex e nal Sys ems and he Con ex play a key ole in
es ablishing u he sys em equi emen s [25,26]. Figu e 3 depic s he di e en in e ac-
ions among he Sys em, Ex e nal Sys ems and Con ex .
Figu e 2. Domains o he design wo ld (adap ed om [13]).
The en i onmen al domain deals wi h he ex e nal ac o s ha impac he wa e
ene gy sys em. This domain is de ined by Sys em D i e s (SD) and hei in e ac ions [
20
].
SD encompass he poli ical, economic, social, echnical, legal and en i onmen al ac o s
ha limi , acili a e o shape he design solu ion. The s akeholde domain de ines he
design p oblem in he cus ome ’s language, which is s ill gene al, ambiguous and highly
unmeasu able [
21
]. I is ep esen ed by he S akeholde Requi emen s (SR), which a e a
se o desi able cha ac e is ics ha he inal solu ion should sa is y. Finally, he unc ional
domain aims o p oduce a comple e, unambiguous and echnology-agnos ic de ini ion o
he design p oblem space [
22
]. Func ions desc ibe he pu poses o he wa e ene gy sys em
and Func ional Requi emen s (FR) and speci y wha he sys em mus do in o de o achie e
he SR [20].
Once he c i ical sys em p ope ies a e es ablished in he o m o wa e ene gy sys-
em equi emen s, e alua ion c i e ia a e assigned o o e a c edible means by which o
assess a ious design op ions. Me ics linked o he uppe sys em a ibu es (i.e., SR) a e
usually e e ed o as Measu es o E ec i eness (MOE). They a e educed in numbe since
he lowe le el e alua ion me ics a e successi ely de i ed om hem [
23
]. Measu es
o Pe o mance (MOP) a e used o gauge he FR o a design solu ion, whils Technical
Pe o mance Measu es (TPM) a e used o demons a e success ul deli e y o he TR. MOP
a e echnology-agnos ic, and aceabili y should be main ained bo h h oughou he de-
composi ion p ocess and wi h ega d o he highe -le el MOE. This hie a chy o e alua ion
c i e ia ensu es a holis ic assessmen ha cap u es di e en le els o de ail and g anula i y
in he me ics. I is wo h no ing ha he concep o design domains coupled wi h his un-
damen al hie a chy o e alua ion c i e ia is also consis en wi h he basic design p ocesses
in he V-model [24], a well-known SE app oach.
Since any wa e ene gy sys em can be successi ely decomposed in o smalle en i ies,
he syn hesis and analysis ac i i ies can be u he expanded by epea ing he domain
mapping p ocess o each subsys em, assembly o componen . Rega dless o he sys em
scope unde conside a ion, i is essen ial o iden i y he en i ies ha in e ac wi h i ia he
sys em’s ex e nal in e aces (i.e., Ex e nal Sys ems) and he wide en i onmen whe e he
sys em is placed (i.e., Con ex ). The Ex e nal Sys ems and he Con ex play a key ole in
es ablishing u he sys em equi emen s [
25
,
26
]. Figu e 3depic s he di e en in e ac ions
among he Sys em, Ex e nal Sys ems and Con ex .
As he Ex e nal Sys ems and Con ex a e de ined in ela ion o he Sys em, i is neces-
sa y o clea ly delimi he scope o he wa e ene gy sys em. Mos commonly, echnology
de elope s iden i y he sys em o e e ence wi h hei Wa e Ene gy Con e e (WEC),
whe eas supplie s conside i o be one o i s main cons i uen s, such as he Powe Take-O
Ene gies 2022,15, 2624 5 o 30
(PTO) o he moo ing sys em. The au ho s o his pape belie e i is mo e app op ia e
and unbiased o designa e he wa e ene gy a m as he baseline sys em o he global
assessmen o echnologies since his is he inal p oduc ha can mee he ma ke need
o sus ainable, a o dable, and secu e ene gy. Mo eo e , his de ini ion is ully consis en
wi h he sys em analysis conduc ed by Baba i e al. o wa e ene gy [
27
]. Howe e , his
app oach can be equally applied o o he sys ems o e e ence such as he WEC, PTO o
moo ing sys em.
Ene gies 2022, 15, x FOR PEER REVIEW 5 o 30
Figu e 3. Sys em, Ex e nal Sys ems and Con ex (adap ed om [25]).
As he Ex e nal Sys ems and Con ex a e de ined in ela ion o he Sys em, i is nec-
essa y o clea ly delimi he scope o he wa e ene gy sys em. Mos commonly, echnology
de elope s iden i y he sys em o e e ence wi h hei Wa e Ene gy Con e e (WEC),
whe eas supplie s conside i o be one o i s main cons i uen s, such as he Powe Take-
O (PTO) o he moo ing sys em. The au ho s o his pape belie e i is mo e app op ia e
and unbiased o designa e he wa e ene gy a m as he baseline sys em o he global
assessmen o echnologies since his is he inal p oduc ha can mee he ma ke need
o sus ainable, a o dable, and secu e ene gy. Mo eo e , his de ini ion is ully consis en
wi h he sys em analysis conduc ed by Baba i e al. o wa e ene gy [27]. Howe e , his
app oach can be equally applied o o he sys ems o e e ence such as he WEC, PTO o
moo ing sys em.
2.2. Quali a i e Assessmen : AHP, QFD and LSP
Complex enginee ing p oblems o en equi e a se o in e dependen and compe ing
c i e ia. The Analy ic Hie a chy P ocess (AHP) is a use ul ool ha p o ides a sys ema ic
app oach o suppo mul i-c i e ia decision making. De eloped by Saa y in 1980 [28], AHP
assis s in cap u ing bo h subjec i e and objec i e aspec s o an enginee ing p oblem by
b eaking down decisions in o a se ies o pai wise compa isons and combining hem in o
a single scale. Fu he mo e, AHP includes an e ec i e echnique o check he consis ency
o he e alua ion, hence educing he bias in he inal decision. Since i s eme gence, i has
become one o he mo e widely used mul i-c i e ia analysis me hods.
AHP is o malised in ou main s eps. I s a s by decomposing he decision p oblem
in o a hie a chy o sub-p oblems. Decision c i e ia a e placed in an nxn squa ed ma ix
and wo c i e ia a e compa ed a each ime o de e mine which one is mo e impo an .
Whene e he c i e ia in ows a e mo e impo an han he ones in columns, he 9-poin
g ada ion scale [28] shown in Table 1 is used o quan i y he compa ison, aij. O he wise,
he ecip ocal alue is assigned, aji = 1/aij.
Table 1. G ada ion scale o pai wise compa isons [28].
Impo ance De ini ion Explana ion
1 Equal Fac o s con ibu e equally o he objec i e
3 Mode a e One ac o is sligh ly a ou ed o e ano he
5 S ong One ac o is s ongly a ou ed o e ano he
7 Ve y s ong E idence exis s o a ac o dominance
9 Ex emely s ong Highes possible alidi y o a ac o
2, 4, 6, 8 In e media e alues Fo a comp omise be ween he abo e alues
Based on each c i e ia p io i y, he o e all anking is de eloped by no malising he
judgemen ma ix. The ela i e impo ance, wi, is calcula ed as ollows:
Figu e 3. Sys em, Ex e nal Sys ems and Con ex (adap ed om [25]).
2.2. Quali a i e Assessmen : AHP, QFD and LSP
Complex enginee ing p oblems o en equi e a se o in e dependen and compe ing
c i e ia. The Analy ic Hie a chy P ocess (AHP) is a use ul ool ha p o ides a sys ema ic
app oach o suppo mul i-c i e ia decision making. De eloped by Saa y in 1980 [
28
], AHP
assis s in cap u ing bo h subjec i e and objec i e aspec s o an enginee ing p oblem by
b eaking down decisions in o a se ies o pai wise compa isons and combining hem in o a
single scale. Fu he mo e, AHP includes an e ec i e echnique o check he consis ency
o he e alua ion, hence educing he bias in he inal decision. Since i s eme gence, i has
become one o he mo e widely used mul i-c i e ia analysis me hods.
AHP is o malised in ou main s eps. I s a s by decomposing he decision p oblem
in o a hie a chy o sub-p oblems. Decision c i e ia a e placed in an nxn squa ed ma ix
and wo c i e ia a e compa ed a each ime o de e mine which one is mo e impo an .
Whene e he c i e ia in ows a e mo e impo an han he ones in columns, he 9-poin
g ada ion scale [
28
] shown in Table 1is used o quan i y he compa ison, a
ij
. O he wise,
he ecip ocal alue is assigned, aji =1/aij.
Table 1. G ada ion scale o pai wise compa isons [28].
Impo ance De ini ion Explana ion
1 Equal Fac o s con ibu e equally o he objec i e
3 Mode a e One ac o is sligh ly a ou ed o e ano he
5 S ong One ac o is s ongly a ou ed o e ano he
7 Ve y s ong E idence exis s o a ac o dominance
9 Ex emely s ong Highes possible alidi y o a ac o
2, 4, 6, 8 In e media e alues Fo a comp omise be ween he abo e alues
Based on each c i e ia p io i y, he o e all anking is de eloped by no malising he
judgemen ma ix. The ela i e impo ance, wi, is calcula ed as ollows:
a0
ij =aij
∑n
i=1aij
,i=1, 2, . . . , n;j=1, 2, . . . , n(1)
wi=∑n
j=1a0
ij
n,i=1, 2, . . . , n(2)

Ene gies 2022,15, 2624 6 o 30
Finally, he deg ee o consis ency among he pai wise compa isons is measu ed by
compu ing he Consis ency Index and Consis ency Ra io [
28
]. Acco ding o his, a Consis-
ency Ra io below 0.1 is deemed sa is ac o y.
Un il now, AHP has been only applied in wa e ene gy o ank echnology op ions
wi h ega d o echno-economic c i e ia (e.g., ene gy cap u e, cos , eliabili y, en i onmen al
iendliness, adap abili y) in a single s ep [
29
]. To limi he subjec i i y o and dependence
on expe judgemen s, AHP will be used in he en i onmen al domain o p io i ise Sys em
D i e s (SD) a he ou se o his no el me hodology (please see Appendix A). Fo he
es o he c oss-domain assessmen s, ano he ma ix-based me hod will be used, namely
Quali y Func ion Deploymen (QFD).
QFD [
30
] is ano he well-known design ool de eloped in Japan by he end o he
1960s, being i s documen ed a he Kobe shipya ds o Mi subishi Hea y Indus ies in
1972. I is used o ansla e he Voice o he Cus ome (VoC) in o sys em equi emen s
employing a se ies o ma ices called he House o Quali y (HoQ). Sys em equi emen s
ini ially consis ed o jus cus ome needs and echnical equi emen s, bu hey can equally
be unc ions, design pa ame e s o c i ical p ocess a iables. Fu he mo e, QFD ma ices
can be linked in a wa e all manne o ensu e he ull aceabili y o he equi emen s.
QFD is o malised in 6 main s eps:
1.
To de e mine he inpu equi emen s and ela i e impo ance a ings. In he p oposed
me hodology, AHP is adop ed o he p io i isa ion o ini ial ac o s, ha is, Sys em
D i e s (SD).
2.
To benchma k how he inpu equi emen s a e cu en ly sa is ied. This s ep c ea es
an awa eness o wha al eady exis s and acili a es assigning a ge alues o hese
equi emen s.
3.
To gene a e ou pu equi emen s, which a e he es a emen o he design p oblem in
he co esponding domain. The Func ional Analysis and Sys em Technique (FAST)
can be used o he iden i ica ion o he ou pu equi emen s [31].
4.
The ela ionship ma ix is used o ela e he inpu and ou pu equi emen s. This
way he p io i ies o he inpu equi emen s can be ansla ed in o he ela i e im-
po ance a ings o ou pu equi emen s (S ep 6). In o de o do so, he ela ionships
adi ionally exp essed in quali a i e symbols (e.g.,

s ong,
#
medium,
4
weak)
a e con e ed in o nume ical coe icien s (e.g., 9-3-1).
5.
The co ela ion ma ix is added o highligh in e ela ionships be ween ou pu e-
qui emen s. Posi i e ela ionships ep esen suppo ing equi emen s, whils nega i e
linkages help iden i y con lic s and ade-o s. Quali a i e symbols (e.g., +,
−
) o
nume ical a ings (e.g., 1, −1) a e used o desc ibe hese ela ionships.
6.
To de e mine ela i e impo ance a ings o he ou pu equi emen s. The absolu e
le el o impo ance o he ou pu equi emen , w
j
, is ob ained by summing he ela i e
impo ance o he inpu equi emen s, d
i
, mul iplied by he quan i ied nume ical
coe icien s, ij. The ela i e impo ance a ing, w0
j, is hen compu ed as:
wj=
n
∑
i=1
di· ij,i=1, 2, . . . , n;j=1, 2, . . . , m(3)
w0
j=wj
∑m
j=1wj
(4)
whe e nand ma e he numbe o inpu and ou pu equi emen s, espec i ely.
To de e mine he ela i e impo ance a ings, some au ho s ha e p oposed no mali-
sa ion models ha also include he co ela ion ma ix. Chen’s app oach [
32
] is aimed o
o e come he limi a ions o o he models ha p oduce un easonable esul s. In his me hod,
he nume ical coe icien s, ij, a e no malised acco ding o he ollowing equa ion:
Ene gies 2022,15, 2624 7 o 30
0
ij =∑m
k=1ckj ij
∑m
j=1∑m
k=1ckj ij
,c∈[1, −1](5)
whe e ckj a e he numbe a ings o he co ela ion ma ix.
In wa e ene gy, QFD has been applied o assess he po en ial o wa e ene gy in-
no a ions de ined by i s unc ions, wi hou any no malisa ion and in a single s ep [
33
].
The QFD ool wi h Chen no malisa ion will be used o link SD o S akeholde s (SH) and
assign impo ance a ings o wa e ene gy equi emen s in he di e en domains (please
see Appendix A).
Las ly, he agg ega ion concep is a common ea u e o mul i-c i e ia analysis me hods.
E en hough ools such as AHP o QFD can be used o de i e weigh ings o he a ious
e alua ion c i e ia, combining he lowe -le el e alua ion c i e ia in o an agg ega ed sco e
is no a simple ask. The TPL me hodology [
6
] in oduces ou deg ees o lexibili y o
ca y ou his agg ega ion in o highe -le el me ics. The Logical Sco ing o P e e ence
(LSP) me hod p oposed by Dujmo ic [
34
] is used he e o cap u e he unde lying unc ional
ela ionships and add mo e g anula i y o he agg ega ion s ep by allowing he de ini ion
o he deg ee o simul anei y o he equi emen s being combined om o al disjunc ion o
ull conjunc ion [35].
Conjunc ion in LSP means ha he ou pu u ili y is p edominan ly a ec ed by he
alue o he smalles inpu , calling o simul aneous high inpu alues. The geome ic
and ha monic means, espec i ely, a e examples o con en ional ope a o s ha p o ide
inc easing le els o simul anei y. Con e sely, disjunc ion means ha he ou pu u ili y
allows he eplaceabili y o low- alue inpu s. The squa e mean is an example o pa ial
eplaceabili y. Neu ali y, ha is, he pe ec balance be ween conjunc ion and disjunc ion, is
deno ed in LSP by he weigh ed a i hme ic mean. When combining manda o y and op ional
inpu s o su icien and op ional inpu s, conjunc i e o disjunc i e pa ial abso p ion a e
used, espec i ely. The in ensi y o he simul anei y o eplaceabili y can be con inuously
adjus ed by selec ing di e en ope a o s.
Following his app oach, he e alua ion c i e ia can be agg ega ed sequen ially in o
highe hie a chical le els accoun ing o he deg ee o simul anei y o he di e en a ibu es
un il he inal o e a ching me i is ob ained. The o e all sui abili y can be in e p e ed as
he quali a i e deg ee o sa is ac ion o all speci ied equi emen s. This sui abili y, s
0
, is
compu ed om he nex le el o e alua ion c i e ia, si, as ollows:
s0= n
∑
i=1
wi·sd
i!1
d
;
n
∑
i=1
i=1, i=1, 2, . . . , n(6)
whe e nis he numbe o e alua ion c i e ia, w
n
a e hei weigh ings, and dis a coe icien
ha depends on he deg ee o simul anei y. Values o d ange om
−∞
o pu e conjunc ion
o +
∞
o pu e disjunc ion. Addi ional alues a e p o ided in [
34
] o o he al e na i es o
pa ial conjunc ion and disjunc ion.
2.3. Pe o mance Benchma k: Comme cial A ac i eness and Technical Achie abili y
To p o ide a quan i a i e assessmen , sys em pe o mance needs o be measu ed
agains a speci ied e e ence. QFD conside s a pa icula s ep o benchma k how he sys em
equi emen s a e cu en ly sa is ied. Awa eness o bes p ac ices in wa e ene gy helps
o assign accep able, achie able and desi able anges o sys em equi emen s such as
in [
36
] o he cap u e wid h. These a ge alues enable benchma king o he ela i e
pe o mance o wa e ene gy echnologies in a quan i a i e manne . E alua ion c i e ia
a ge s di ide echnology pe o mance in o wo sepa a e egions. The e is he egion
o accep able pe o mance whe e he echnology ei he mee s o exceeds he speci ied
e e ence o he co esponding me ic. By con as , unaccep able pe o mance pops up
Ene gies 2022,15, 2624 8 o 30
when he echnology alls sho wi h ega d o his e e ence alue [
37
]. Any wa e ene gy
de elope aims o each he accep able pe o mance egion o all manda o y me ics.
No wi hs anding he me ic unde conside a ion, e alua ion c i e ia can p esen wo
di e en pe o mance beha iou s. Whe eas some me ics in he e alua ion hie a chy mus
dec ease o mee he es ablished a ge , o he me ics display an inc easing pe o mance
pa e n. Le us de ine he Pe o mance Ra io (PR) o o e come his opposing beha iou .
Fo me ics ha exhibi dec easing pe o mance (i.e., lowe is be e ), he PR
i
is calcula ed
as ollows:
PRi=Ti
Mi
(7)
whe e T
i
and M
i
a e he a ge and measu ed pe o mance alues, espec i ely, o he
e alua ion c i e ia i. Typical examples o his ca ego y o me ics a e he Le elized Cos o
Ene gy (LCOE) and he Mean Time o Repai (MTTR).
Al e na i ely, o me ics ha show an inc easing pe o mance pa e n (i.e., highe is
be e ), he PR
i
is calcula ed e e sing his quo ien , which accoun s o he pe cen age ha
he measu ed pe o mance exceeds he a ge alue.
PRi=Mi
Ti
(8)
Some examples o his ca ego y o me ics a e he Capaci y Fac o (CF), A ailabili y
Fac o (AF) and he Mean Time Be ween Failu es (MTBF).
The ou come o pe o mance benchma king o a wa e ene gy concep gi es an es i-
ma ion o how close o a he echnology is o achie ing i s p e iously es ablished echnical
goals. A PR
i≥
1 will mean ha he wa e ene gy echnology is in he accep able pe o -
mance egion o he e alua ion c i e ia i. Con e sely, a PR
i
< 1 deno es an unaccep able
pe o mance o his e alua ion c i e ia. Technologies ha ha e all manda o y equi emen s
in he accep able pe o mance egion can be benchma ked in e ms o hei comme cial
a ac i eness. O he wise, he echnical achie abili y should be in es iga ed.
Comme cial A ac i eness (CA) is a b oad concep ha can encompass a ious aspec s
anging om economic p o i abili y o s akeholde accep abili y and size o he ma ke
oppo uni y. In he ield o wa e ene gy, CA has been de ined as he a io o he a ge
LCOE alue o he calcula ed one o he explo a ion o concep s beyond he exis ing
echnologies [
38
]. No e ha his a io i s pe ec ly wi hin he gene ic PR de ini ion om
Equa ion (7), bu in his case applied o he Le elized Cos o Ene gy, a common high-le el
a o dabili y me ic. The assessmen o CA is also men ioned in he In e na ional E alua ion
F amewo k o Ocean Ene gy Technologies [
7
], his ime comp ising bo h he cos o ene gy
and sus ainabili y aspec s such as en i onmen al and social accep ance. The guideline,
howe e , does no p o ide any me ic o sus ainabili y.
To ake in o conside a ion he quali a i e aspec s beyond me e a o dabili y, he p o-
posed me hod will de ine CA as he p oduc o he Global Me i (GM), de i ed om he
quali a i e assessmen , and he PR o he cos o ene gy when PR
≥
1. This de ini ion has
he ad an age o enabling an objec i e compa ison o wa e ene gy echnologies in a i-
ous ma ke s p esen ing dissimila ene gy p ices and esponding o di e en s akeholde
demands and p io i ies.
I PR ≥1 CA =GM∗PR; else CA =0 (9)
Fo wa e ene gy echnologies ha a e unable o mee one o mo e o he manda o y
equi emen s and he e o e echnological imp o emen s a e needed, he Technical Achie -
abili y (TA) concep is in oduced. I o e s a measu e o he echnology de elopmen isk,
ime o e o o mee he a ge pe o mance. This concep is pa icula ly use ul when
guiding echnologies wi h long de elopmen imes such as wa e ene gy. TA has been
o mula ed in [
38
] o me ics o powe pe o mance and subsys em cos . Imp o emen
ac o s and lea ning a es a e used o assess he deg ee o e o needed. Addi ionally, he
Ene gies 2022,15, 2624 9 o 30
e e se LCOE enginee ing me hod [
13
] was p oposed o explo e he limi s o he echnical
pa ame e s o wa e ene gy echnologies. Basically, his is a unidimensional analysis in
which all pa ial e alua ion c i e ia a e ixed, and he cos educ ion is in es iga ed o
achie e a PR = 1.
This me hod p oposes an al e na i e bu mo e comp ehensi e de ini ion ha can be
used o assess wa e ene gy pe o mance a any hie a chical le el. This TA de ini ion has
been adap ed om [
39
], whe e i is used o suppo decisions o new de ence echnologies
h ough hei de elopmen li ecycle based on pe o mance assessmen . The TA combines
he PR and Deg ee o Di icul y (DD) in he ollowing manne :
TA =PR
1+(1−PR)∗DD (10)
The DD p o ides an e ec i e measu e o he p obabili y o isk, whils (1
−
PR), he
unme pe o mance is a measu e o he se e i y o impo ance o isk. Table 2p esen s he
DD le els and hei co esponding nume ical alues. The isk le els a e based on [
39
] bu
he assigned nume ical alues ha e been esized o a 9-poin scale o consis ency wi h he
p e ious anking me hods. The lowe bound (0) indica es ha he e is no isk in mee ing
he equi emen and success is he e o e gua an eed. Al e na i ely, he uppe bound (9)
means ha i is impossible o mee he equi emen . In e media e le els deno e di e en
deg ees o di icul y. DD measu es he lea ning a e ha needs o happen o achie e a
PR = 1.
Table 2. Technical Di icul y (adap ed om [39]).
Le el Deg ee o Di icul y (DD) Value
1 Ve y low unce ain y (ce ain easibili y) 0
2 Mode a e unce ain y 1
3 High unce ain y 3
4 Ve y high unce ain y ( undamen al b eak h ough) 9
Figu e 4shows ou achie abili y cu es o di e en DD le els. Fo ins ance, he
TA o one echnology wi h e y low unce ain y and PR = 0.6 (poin a) is analogous
o a echnology wi h a PR = 0.94 (poin c) and e y high unce ain y, which equi es a
undamen al b eak h ough. Simila ly, a echnology wi h e y high unce ain y bu he
same PR = 0.6 (poin b) will see i s TA se e ely dec ease o 0.13.
Ene gies 2022, 15, x FOR PEER REVIEW 10 o 30
Figu e 4. Technical Achie abili y.
3. De elopmen o he Sys ema ic Design App oach
3.1. Analysis o he O e a ching Con ex
3.1.1. Wa e Ene gy D i e s
The en i onmen al domain ecognises ha he wa e ene gy sys em exis s wi hin a
con ex in which mul iple ex e nal d i e s in luence i s concep ion, planning, and ope a-
ion. These Sys em D i e s (SD) a e an essen ial pa o he con ex and a e igh ly con-
nec ed o he in ended ma ke applica ion. Two ele an ma ke applica ions o wa e en-
e gy echnologies ha e been selec ed o illus a e his no el me hodology, assuming ha
he main p oduc o wa e ene gy is expec ed o be powe p oduc ion [17] such as:
 Ma ke 1: U ili y-scale gene a ion.
 Ma ke 2: Powe ing emo e communi ies.
A de ailed cha ac e isa ion o hese wo ma ke s is p esen ed in [26] and summa ised
in Table 3.
Table 3. Ma ke cha ac e is ics [26].
Ma ke Cha ac e is ics
U ili y-scale gene a ion
A ac i e bu also e y compe i i e.
WEC design is mainly d i en by his ma ke .
Inc easing demand o enewable elec ici y.
Legal obliga ions o mee deca bonisa ion a ge s.
Remo e communi y
gene a ion
A na owe span o compe i ion (some imes jus one op ion—diesel).
Low ene gy secu i y and quali y.
Consume s a e ulne able o p ice luc ua ion and high ene gy cos s.
Simpli ied ma ke and egula o y condi ions.
An analysis o wa e ene gy d i e s using PESTLE [40] is also p esen ed in [26]. Table
4 summa ises he SD o wa e ene gy g ouped pe ca ego y.
Table 4. Sys em D i e s o wa e ene gy [26].
Id Ca ego y Wa e Ene gy D i e s
SD1 Poli ical Fa ou able policies (e.g., ene gy secu i y, inance, job c ea ion)
Ma ke suppo mechanisms
Figu e 4. Technical Achie abili y.
Ene gies 2022,15, 2624 16 o 30
Ene gies 2022, 15, x FOR PEER REVIEW 17 o 30
Figu e 9. FAST diag am o he wa e ene gy sys em.
I is wo hwhile men ioning ha he TPL assessmen me hod [6] also p o ides an
analysis o equi emen s including a ious le els o unc ions. The op-le el unc ions a e
di ec ly linked o he SR and he sys em mission. The nex b eakdown le el compa es wi h
he FR, whe eas he lowe le els should be ela ed o he TR. The unc ional ee is no
de eloped o he same dep h in all i s b anches which makes i di icul o apply he design
domains me hod. Mo eo e , he combina ion o indi idual weigh ings is no aced in he
a ious domains bu is assigned h ough expe judgemen .
Figu e 9. FAST diag am o he wa e ene gy sys em.
I is wo hwhile men ioning ha he TPL assessmen me hod [
6
] also p o ides an
analysis o equi emen s including a ious le els o unc ions. The op-le el unc ions a e
di ec ly linked o he SR and he sys em mission. The nex b eakdown le el compa es wi h
he FR, whe eas he lowe le els should be ela ed o he TR. The unc ional ee is no
de eloped o he same dep h in all i s b anches which makes i di icul o apply he design
domains me hod. Mo eo e , he combina ion o indi idual weigh ings is no aced in he
a ious domains bu is assigned h ough expe judgemen .

Ene gies 2022,15, 2624 17 o 30
3.2.2. Func ional Requi emen s (FR) and Me ics
The FAST diag am has been used o iden i y he FR. Measu es o Pe o mance (MOPs)
a e used o speci ically gauge he capabili ies o a design solu ion. They a e assigned o
each equi emen o enable he echnology-agnos ic assessmen o wa e ene gy al e na i es
in an objec i ised manne . The wa e ene gy sys em has 10 main FR as shown in Table 9.
Table 9. Func ional Requi emen s and Me ics.
Id Func ional Requi emen s Measu es o Pe o mance (MOP)
FR1 Cap u e ene gy om wa es No malised Cap u e Wid h (Cwn) [50]
FR2 T ans o m in o use ul ene gy T ans o ma ion E iciency (η ) [7]
FR3 Deli e ene gy o poin o consump ion Deli e y E iciency (ηd) [51]
FR4 Maximise o al up ime Reliabili y (MTBF = 1/λ1) [7]
FR5 Minimise o al down ime Main ainabili y (MTTR = 1/µ2) [7]
FR6 Manu ac u e by indus ial p ocesses Manu ac u abili y (MANEX) [7]
FR7 Ins all/ e ie e by se ice essels Ins allabili y (INSTEX) [7]
FR8 Main ain by se ice essels Repai abili y (REPEX) [7]
FR9 Su i e he ha sh en i onmen Su i abili y (SURV) [7]
FR10 A oid isks o ecep o s En i onmen al Impac Sco e (EIS) [52]
1λ= ailu e a e, 2µ= epai a e.
Once again, QFD has been used o p io i ise FR in he p oposed me hod. Since SR a e
only coupled o a educed numbe o FR (1 o 3 max), he ela i e impo ance a ings o
FR ha e been di ec ly es ablished om li e a u e analysis. The same impo ance a ing
scale shown in Table 5is used o de i e SR–SH ela ionships. The esul s a e p esen ed in
Sec ion 4and u he comple ed in he Appendix A.
Figu e 10 p esen s he agg ega ion logic o he di e en MOP. The weigh s abo e each
a ow, w
i
, ep esen he ela i e impo ance a ings o he FR. Con e ing wa e ene gy
in o consumable powe (SR1) equi es cap u ing, ans o ming, and deli e ing he ene gy.
These unc ions ha e hei own e iciency a ings and a e combined using he weigh ed
geome ic mean (G). Ope a ing when needed (SR2) en ails maximising he o al up ime and
minimising he o al down ime. These a ios a e combined in o he sys em a ailabili y ac o
employing he ha monic mean (H) which calls o a highe deg ee o simul anei y. Reducing
up on cos s (SR3) in ol es manu ac u ing and ins alla ion. The neu al a i hme ic mean
(A) is used in his case as he di e en cos cen es can be compensa ed. Reducing annual
cos s has no been spli in o di e en unc ions and he epai abili y is ma ched o he
ope a ional cos s. Finally, p e en ing business isks equi e su i ing he ha sh ocean
en i onmen and a oiding isks o ecep o s. The Quasi-Conjunc ion (QC) ope a o is
employed o penalise a low u ili y alue o each indi idual unc ional equi emen .
Ene gies 2022, 15, x FOR PEER REVIEW 18 o 30
3.2.2. Func ional Requi emen s (FR) and Me ics
The FAST diag am has been used o iden i y he FR. Measu es o Pe o mance
(MOPs) a e used o speci ically gauge he capabili ies o a design solu ion. They a e as-
signed o each equi emen o enable he echnology-agnos ic assessmen o wa e ene gy
al e na i es in an objec i ised manne . The wa e ene gy sys em has 10 main FR as shown
in Table 9.
Table 9. Func ional Requi emen s and Me ics.
Id Func ional Requi emen s Measu es o Pe o mance (MOP)
FR1 Cap u e ene gy om wa es No malised Cap u e Wid h (Cwn) [50]
FR2 T ans o m in o use ul ene gy T ans o ma ion E iciency (η ) [7]
FR3 Deli e ene gy o poin o consump ion Deli e y E iciency (ηd) [51]
FR4 Maximise o al up ime Reliabili y (MTBF = 1/λ 1) [7]
FR5 Minimise o al down ime Main ainabili y (MTTR = 1/μ 2) [7]
FR6 Manu ac u e by indus ial p ocesses Manu ac u abili y (MANEX) [7]
FR7 Ins all/ e ie e by se ice essels Ins allabili y (INSTEX) [7]
FR8 Main ain by se ice essels Repai abili y (REPEX) [7]
FR9 Su i e he ha sh en i onmen Su i abili y (SURV) [7]
FR10
A oid isks o ecep o s En i onmen al Impac Sco e (EIS) [52]
1 λ = ailu e a e, 2 μ = epai a e.
Once again, QFD has been used o p io i ise FR in he p oposed me hod. Since SR a e
only coupled o a educed numbe o FR (1 o 3 max), he ela i e impo ance a ings o
FR ha e been di ec ly es ablished om li e a u e analysis. The same impo ance a ing
scale shown in Table 5 is used o de i e SR–SH ela ionships. The esul s a e p esen ed in
Sec ion 4 and u he comple ed in he Appendix A.
Figu e 10 p esen s he agg ega ion logic o he di e en MOP. The weigh s abo e
each a ow, wi, ep esen he ela i e impo ance a ings o he FR. Con e ing wa e en-
e gy in o consumable powe (SR1) equi es cap u ing, ans o ming, and deli e ing he
ene gy. These unc ions ha e hei own e iciency a ings and a e combined using he
weigh ed geome ic mean (G). Ope a ing when needed (SR2) en ails maximising he o al
up ime and minimising he o al down ime. These a ios a e combined in o he sys em
a ailabili y ac o employing he ha monic mean (H) which calls o a highe deg ee o
simul anei y. Reducing up on cos s (SR3) in ol es manu ac u ing and ins alla ion. The
neu al a i hme ic mean (A) is used in his case as he di e en cos cen es can be com-
pensa ed. Reducing annual cos s has no been spli in o di e en unc ions and he epai -
abili y is ma ched o he ope a ional cos s. Finally, p e en ing business isks equi e su -
i ing he ha sh ocean en i onmen and a oiding isks o ecep o s. The Quasi-Conjunc-
ion (QC) ope a o is employed o penalise a low u ili y alue o each indi idual unc-
ional equi emen .
Figu e 10. Agg ega ion o MOP.
Figu e 10. Agg ega ion o MOP.
As men ioned be o e, he eade should bea in mind ha he u ili y assigned o each
MOP migh di e om he alues es ima ed wi h nume ical me hods, since he agg ega ion
Ene gies 2022,15, 2624 18 o 30
logic also accoun s o he ela i e impo ance exp essed by he s akeholde s, he unde lying
deg ee o simul anei y and he lexibili y allowed o he a ious equi emen s.
4. Resul s and Discussion
4.1. Quali a i e Assessmen
Acco ding o he su ey esul s in [
26
], he anking o wa e ene gy d i e s conside -
ably di e s be ween he wo applica ion ma ke s. U ili y-scale is a e y compe i i e ma ke
and mainly mo i a ed by Economic and Poli ical ac o s, whe eas he emo e communi y
gene a ion ma ke is d i en by Social ac o s. The applica ion o AHP p o ides mo e
g anula i y o compa e his ou come. The weigh s esul ing om pai wise compa isons
a e eliable since he Consis ency Ra io yields a sa is ac o y alue below 0.1 in bo h cases.
As we can see in Figu e 11, he Economic, Poli ical and Technological ac o s a e e y
impo an d i e s in he u ili y-scale gene a ion, accoun ing o almos 85% o he o al
a ings. Howe e , in emo e communi ies, mo e d i e s come in o play. Economic, Poli ical
and Technological ac o s a e s ill impo an , bu he Social ac o s domina e. Al oge he ,
hey accoun o 92% o he o al a ings. I is somehow su p ising ha he Legal and En i-
onmen al ac o s a e conside ed o ha e mino impo ance o bo h ma ke s, and ha also
he Social ac o s sco e las in he u ili y-scale ma ke when i is he majo mo i a ion o a
emo e communi y ma ke . I can be in e ed om hese esul s ha i wa e echnology is
p o en o wo k, he legal and pe mi ing side will e en ually ollow.
Ene gies 2022, 15, x FOR PEER REVIEW 19 o 30
As men ioned be o e, he eade should bea in mind ha he u ili y assigned o each
MOP migh di e om he alues es ima ed wi h nume ical me hods, since he agg ega-
ion logic also accoun s o he ela i e impo ance exp essed by he s akeholde s, he un-
de lying deg ee o simul anei y and he lexibili y allowed o he a ious equi emen s.
4. Resul s and Discussion
4.1. Quali a i e Assessmen
Acco ding o he su ey esul s in [26], he anking o wa e ene gy d i e s conside -
ably di e s be ween he wo applica ion ma ke s. U ili y-scale is a e y compe i i e ma -
ke and mainly mo i a ed by Economic and Poli ical ac o s, whe eas he emo e commu-
ni y gene a ion ma ke is d i en by Social ac o s. The applica ion o AHP p o ides mo e
g anula i y o compa e his ou come. The weigh s esul ing om pai wise compa isons
a e eliable since he Consis ency Ra io yields a sa is ac o y alue below 0.1 in bo h cases.
As we can see in Figu e 11, he Economic, Poli ical and Technological ac o s a e e y
impo an d i e s in he u ili y-scale gene a ion, accoun ing o almos 85% o he o al
a ings. Howe e , in emo e communi ies, mo e d i e s come in o play. Economic, Poli -
ical and Technological ac o s a e s ill impo an , bu he Social ac o s domina e. Al o-
ge he , hey accoun o 92% o he o al a ings. I is somehow su p ising ha he Legal
and En i onmen al ac o s a e conside ed o ha e mino impo ance o bo h ma ke s,
and ha also he Social ac o s sco e las in he u ili y-scale ma ke when i is he majo
mo i a ion o a emo e communi y ma ke . I can be in e ed om hese esul s ha i
wa e echnology is p o en o wo k, he legal and pe mi ing side will e en ually ollow.
Figu e 11. Rela i e impo ance o SD o he applica ion ma ke .
Addi ionally, he applica ion o QFD p o ides u he insigh in o he conclusions
ob ained in [26]. I con i ms ha he de elopmen o wa e ene gy echnologies will be
p ima ily in luenced by he needs o he Owne (19%) o u ili y-scale gene a ion and he
Go e nmen (17%) o emo e communi y p ojec s. Addi ionally, i was concluded ha
he Owne , Lende s, EPCI con ac o and O&M p o ide a e sligh ly mo e in luen ial in
he u ili y-scale applica ion. This beha iou is e e sed o he Regula o s, P essu e
g oups and Consume s in he emo e communi y gene a ion.
F om Figu e 12 i can be concluded ha he Go e nmen has he same impo ance
o bo h ma ke s. Ac ually, i is he second- anked SH o he u ili y-scale ma ke . On he
o he hand, he Owne sco es second (15.5%) a e he Go e nmen o he emo e com-
muni y gene a ion. Bo h he Owne and Go e nmen play a undamen al ole in bo h
ma ke s. The ela i e weigh s o he di e en s akeholde g oups o each ma ke will
Figu e 11. Rela i e impo ance o SD o he applica ion ma ke .
Addi ionally, he applica ion o QFD p o ides u he insigh in o he conclusions
ob ained in [
26
]. I con i ms ha he de elopmen o wa e ene gy echnologies will be
p ima ily in luenced by he needs o he Owne (19%) o u ili y-scale gene a ion and he
Go e nmen (17%) o emo e communi y p ojec s. Addi ionally, i was concluded ha he
Owne , Lende s, EPCI con ac o and O&M p o ide a e sligh ly mo e in luen ial in he
u ili y-scale applica ion. This beha iou is e e sed o he Regula o s, P essu e g oups
and Consume s in he emo e communi y gene a ion.
F om Figu e 12 i can be concluded ha he Go e nmen has he same impo ance o
bo h ma ke s. Ac ually, i is he second- anked SH o he u ili y-scale ma ke . On he o he
hand, he Owne sco es second (15.5%) a e he Go e nmen o he emo e communi y
gene a ion. Bo h he Owne and Go e nmen play a undamen al ole in bo h ma ke s.
The ela i e weigh s o he di e en s akeholde g oups o each ma ke will de e mine he
global me i and inal sui abili y o wa e ene gy echnologies in he quali a i e assessmen .
Ene gies 2022,15, 2624 19 o 30
Ene gies 2022, 15, x FOR PEER REVIEW 20 o 30
de e mine he global me i and inal sui abili y o wa e ene gy echnologies in he quali-
a i e assessmen .
Figu e 12. Rela i e impo ance o SH o he applica ion ma ke .
I can be obse ed in Figu e 13 ha SR ha e a ela i ely simila impo ance o he
wo applica ion ma ke s unde conside a ion ( a iabili y below 10%). The con e sion o
wa e ene gy in o consumable powe , he con inuous ope a ion and he annual cos s e-
duc ion ha e g ea e in luence in he emo e communi y ma ke . Al e na i ely, he u ili y-
scale gene a ion ma ke pu s mo e emphasis on he p e en ion o business isks and he
educ ion in up on cos s. This quali a i e assessmen assigns weigh s abo e he a e age
impo ance a ing (20%) o wa e ene gy con e sion and isk p e en ion o bo h ma ke s.
Figu e 13. Rela i e impo ance o SR o he applica ion ma ke .
Likewise, as depic ed in Figu e 14, FR ha e ela i ely equal impo ance o he wo
applica ion ma ke s unde conside a ion ( a iabili y lowe han 9%). The unc ions con-
ibu ing o each SR ollow he same pa e n as be o e. Howe e , we can app ecia e ha
cap u ing and ans o ming wa e ene gy, minimising o al down ime and su i ing he
ha sh en i onmen a e he mos ele an equi emen s, all o hem abo e he a e age im-
po ance a ing (10%).
Figu e 12. Rela i e impo ance o SH o he applica ion ma ke .
I can be obse ed in Figu e 13 ha SR ha e a ela i ely simila impo ance o he
wo applica ion ma ke s unde conside a ion ( a iabili y below 10%). The con e sion
o wa e ene gy in o consumable powe , he con inuous ope a ion and he annual cos s
educ ion ha e g ea e in luence in he emo e communi y ma ke . Al e na i ely, he
u ili y-scale gene a ion ma ke pu s mo e emphasis on he p e en ion o business isks
and he educ ion in up on cos s. This quali a i e assessmen assigns weigh s abo e he
a e age impo ance a ing (20%) o wa e ene gy con e sion and isk p e en ion o bo h
ma ke s.
Ene gies 2022, 15, x FOR PEER REVIEW 20 o 30
de e mine he global me i and inal sui abili y o wa e ene gy echnologies in he quali-
a i e assessmen .
Figu e 12. Rela i e impo ance o SH o he applica ion ma ke .
I can be obse ed in Figu e 13 ha SR ha e a ela i ely simila impo ance o he
wo applica ion ma ke s unde conside a ion ( a iabili y below 10%). The con e sion o
wa e ene gy in o consumable powe , he con inuous ope a ion and he annual cos s e-
duc ion ha e g ea e in luence in he emo e communi y ma ke . Al e na i ely, he u ili y-
scale gene a ion ma ke pu s mo e emphasis on he p e en ion o business isks and he
educ ion in up on cos s. This quali a i e assessmen assigns weigh s abo e he a e age
impo ance a ing (20%) o wa e ene gy con e sion and isk p e en ion o bo h ma ke s.
Figu e 13. Rela i e impo ance o SR o he applica ion ma ke .
Likewise, as depic ed in Figu e 14, FR ha e ela i ely equal impo ance o he wo
applica ion ma ke s unde conside a ion ( a iabili y lowe han 9%). The unc ions con-
ibu ing o each SR ollow he same pa e n as be o e. Howe e , we can app ecia e ha
cap u ing and ans o ming wa e ene gy, minimising o al down ime and su i ing he
ha sh en i onmen a e he mos ele an equi emen s, all o hem abo e he a e age im-
po ance a ing (10%).
Figu e 13. Rela i e impo ance o SR o he applica ion ma ke .
Likewise, as depic ed in Figu e 14, FR ha e ela i ely equal impo ance o he wo
applica ion ma ke s unde conside a ion ( a iabili y lowe han 9%). The unc ions con-
ibu ing o each SR ollow he same pa e n as be o e. Howe e , we can app ecia e ha
cap u ing and ans o ming wa e ene gy, minimising o al down ime and su i ing he
ha sh en i onmen a e he mos ele an equi emen s, all o hem abo e he a e age
impo ance a ing (10%).
Ene gies 2022,15, 2624 20 o 30
Ene gies 2022, 15, x FOR PEER REVIEW 21 o 30
Figu e 14. Rela i e impo ance o FR o he applica ion ma ke .
The p oposed me hod di e s om he TPL sco ing me hodology [6] as i conside s
ha mos o he capabili ies ha e equal in luence. Fo ins ance, he same weigh s a e as-
signed o equi alen pai s o equi emen s FR6 and FR7, FR2 and FR3, and FR4 and FR5.
The aceabili y o design in o ma ion and equi emen s h ough he di e en domains
o e s a mo e objec i e way o accoun o hose di e ences wi hou assuming ei he a la
dis ibu ion o any o he a bi a y dis ibu ion o weigh s.
4.2. Pe o mance Benchma k
To compa e di e en wa e ene gy op ions, a u ili y unc ion was de ined o each
MOE. The unc ion was no malised conside ing maximum (1) and minimum (0) u ili y
alues as shown in Table 10. Wa e ene gy li e a u e was examined o assign maximum
and minimum bounds.
Table 10. S akeholde Requi emen s and U ili y.
Id MOE Min = 0 Max = 1 U ili y Func ion
SR1 Capaci y Fac o (CF) 0% 50% CF/Max
SR2 A ailabili y Fac o (AF) 75% 100% (AF-Min)/(Max-Min)
SR3 Capi al Expendi u e (CAPEX) 5 M EUR
0 M
EUR
1–CAPEX/Min
SR4 Ope a ional Expendi u e (OPEX) 0.5 M
EUR
0 M
EUR
1–OPEX/Min
SR5 Fixed Cha ge Ra e (FCR) 20% 5% 1–(FCR-Max)/(Min-Max)
Table 11 p esen s he Global Me i (GM) o he six illus a i e cases o hypo he ical
wa e ene gy echnologies p e iously de ined in Table 8. The sui abili y sco es we e cal-
cula ed using he agg ega ion logic as shown in Figu e 6 and he weigh s p esen ed in
Figu e 13 o each applica ion ma ke . Fi s , he CF and AF as well as he CAPEX and FCR
we e agg ega ed as he weigh ed geome ic mean, espec i ely. Then, he la e was com-
bined wi h he OPEX h ough he weigh ed a i hme ic mean. Finally, he esul ing alues
we e combined again using he weigh ed geome ic mean. The a o dabili y (LCOE) o
he case s udies is also shown in Table 8.
Table 11. Quali a i e assessmen o wa e ene gy op ions.
Global Me i (GM) Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
U ili y-scale 0.77 0.71 0.73 0.65 0.60 0.51
Remo e communi y 0.77 0.70 0.74 0.66 0.59 0.51
I can be no ed ha he small a ia ion in he weigh s o he wo applica ion ma ke s
esul s in e y simila global me i s in all six case s udies. This esul sugges s ha he
Figu e 14. Rela i e impo ance o FR o he applica ion ma ke .
The p oposed me hod di e s om he TPL sco ing me hodology [
6
] as i conside s
ha mos o he capabili ies ha e equal in luence. Fo ins ance, he same weigh s a e
assigned o equi alen pai s o equi emen s FR6 and FR7, FR2 and FR3, and FR4 and FR5.
The aceabili y o design in o ma ion and equi emen s h ough he di e en domains
o e s a mo e objec i e way o accoun o hose di e ences wi hou assuming ei he a la
dis ibu ion o any o he a bi a y dis ibu ion o weigh s.
4.2. Pe o mance Benchma k
To compa e di e en wa e ene gy op ions, a u ili y unc ion was de ined o each
MOE. The unc ion was no malised conside ing maximum (1) and minimum (0) u ili y
alues as shown in Table 10. Wa e ene gy li e a u e was examined o assign maximum and
minimum bounds.
Table 10. S akeholde Requi emen s and U ili y.
Id MOE Min = 0 Max = 1 U ili y Func ion
SR1 Capaci y Fac o (CF) 0% ≥50% CF/Max
SR2 A ailabili y Fac o (AF) ≤75% 100% (AF-Min)/(Max-Min)
SR3 Capi al Expendi u e (CAPEX) ≥5 M EUR 0 M EUR 1–CAPEX/Min
SR4 Ope a ional Expendi u e (OPEX) ≥0.5 M EUR 0 M EUR 1–OPEX/Min
SR5 Fixed Cha ge Ra e (FCR) ≥20% ≤5% 1–(FCR-Max)/(Min-Max)
Table 11 p esen s he Global Me i (GM) o he six illus a i e cases o hypo he ical
wa e ene gy echnologies p e iously de ined in Table 8. The sui abili y sco es we e cal-
cula ed using he agg ega ion logic as shown in Figu e 6and he weigh s p esen ed in
Figu e 13 o each applica ion ma ke . Fi s , he CF and AF as well as he CAPEX and
FCR we e agg ega ed as he weigh ed geome ic mean, espec i ely. Then, he la e was
combined wi h he OPEX h ough he weigh ed a i hme ic mean. Finally, he esul ing
alues we e combined again using he weigh ed geome ic mean. The a o dabili y (LCOE)
o he case s udies is also shown in Table 8.
Table 11. Quali a i e assessmen o wa e ene gy op ions.
Global Me i (GM) Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
U ili y-scale 0.77 0.71 0.73 0.65 0.60 0.51
Remo e communi y 0.77 0.70 0.74 0.66 0.59 0.51
Ene gies 2022,15, 2624 21 o 30
I can be no ed ha he small a ia ion in he weigh s o he wo applica ion ma ke s
esul s in e y simila global me i s in all six case s udies. This esul sugges s ha he
applica ion ma ke is less signi ican han he o e all echnology pe o mance. In gene al,
he global me i dec eases as he a o dabili y (LCOE) inc eases. Howe e , he quali a i e
assessmen p o ides a way o disambigua e be ween echnologies wi h di e en le els o
e alua ion c i e ia leading o he same LCOE. Fo ins ance, Case 3 has highe me i han
Case 2 al hough hey sha e he same cos , 100 EUR/MWh. This means ha a selec ion o a
wa e ene gy al e na i e exclusi ely based on ei he he LCOE o global me i migh yield
an unsui able decision.
P ecisely, he EU’s SET-Plan implemen a ion plan o Ocean Ene gy [
53
] es ablishes
a a ge LCOE o 100 EUR/MWh by 2035. This a ge LCOE can be used as he e e ence
p ice o ene gy o he u ili y-scale gene a ion ma ke . By con as , acco ding o he Wo ld
Bank [
54
], he a e age p ice o ene gy in 30 o he Small Island De elopmen Coun y
S a es (SIDS) anges be ween 160–330 EUR/MWh. Gi en hese high gene a ion cos s, wa e
ene gy echnologies ha a e no cu en ly a o dable in he u ili y-scale ma ke s may be
al eady cos -compe i i e in hese emo e communi ies. Le us assume 300 EUR/MWh as
he e e ence ene gy p ice o he emo e communi y ma ke o his s udy.
The h eshold alue o he LCOE di ides he echnology sui abili y in o accep able
and unaccep able egions. Table 12 p esen s he Comme cial A ac i eness (CA) esul s
o he u ili y-scale and he emo e communi y ma ke s conside ing he 100 EUR/MWh
and 300 EUR/MWh h esholds, espec i ely. Cases 1–3 ha e a combina ion o MOE ha
yields a sui able cos o ene gy o he u ili y-scale gene a ion ma ke . Howe e , Cases 4–6
can only be compa ible wi h he emo e communi y ma ke .
Table 12. Wa e ene gy a ac i eness.
U ili y-Scale
(100 EUR/MWh) Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
GM 0.77 0.71 0.73 0.65 0.60 0.51
PR 2.00 1.00 1.00 0.67 0.50 0.40
CA 1.54 0.71 0.73 0 0 0
Remo e Communi y
(300 EUR/MWh) Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
GM 0.77 0.70 0.74 0.66 0.59 0.51
PR 5.99 3.01 3.01 2.00 1.50 1.20
CA 4.60 2.11 2.24 1.32 0.89 0.62
The concep o CA no only allows selec ing he mos sui able wa e ene gy op ion
when he LCOE o he global me i a e iden ical o he same ma ke applica ion, bu also
compa ing echnologies o di e en ma ke applica ions. Fo ins ance, Case 4 o emo e
communi y gene a ion (CA = 1.32) is mo e a ac i e han Case 3 o u ili y-scale gene a ion
(CA = 0.73).
Le us ocus now on he Technical Achie abili y (TA) o a wa e ene gy echnology
op ion wi h PR < 1. This applies o Case 4 o he u ili y-scale ma ke (see Table 8). This
echnology op ion is assumed o be in he design op imisa ion s age (TRL 4). Case 2 a ings
a e aken as e e ence alues o compu e he PR (see Table 8). Fo me ics ha exhibi
dec easing pe o mance, PR is calcula ed using Equa ion (7). O he wise, Equa ion (8) is
used. When PR
≥
1, he DD is ob iously ze o as shown in Table 13. Fo unme pe o mances,
he DD le el was es ima ed. The agg ega ed DD o he highe -le el e alua ion c i e ia
was calcula ed as a weigh ed a e age o indi idual DD. The TA is hen compu ed using
Equa ion (10). The DD is mode a e o high (1.32) esul ing in a TA o 0.46. This analysis
p o ides a means o concen a e he inno a ion e o s on imp o ing hose a eas wi h he
g ea es impac on echnology pe o mance, in his pa icula case he CAPEX (0.14) and
he OPEX (0.16). The analysis can be eplica ed a a lowe hie a chical le el in he unc ional
domain o iden i y speci ic imp o emen a eas in he echnology capabili ies.

Ene gies 2022,15, 2624 22 o 30
Table 13. TA o he u ili y-scale gene a ion ma ke .
E al C i e ia Case 2 Case 4
Re e ence Ra ings PR DD TA
CF (%) 25 40 1.60 0.00 1.60
AF (%) 97 98 1.01 0.00 1.01
CAPEX (M EUR) 1.2 3 0.40 3.00 0.14
OPEX (k EUR) 92 210 0.44 3.00 0.16
FCR (%) 10 10.2 0.98 1.00 0.96
LCOE (EUR/MWh) 100 150 0.67 1.32 0.46
Assigning he DD le el o he sys em equi emen s o a wa e ene gy echnology unde
de elopmen seems a qui e subjec i e and challenging ask. Despi e he di icul ies, oo
li le ime spen in he ea ly design phases can lead o gaps in unde s anding he p oblem
equi emen s, limi ed oppo uni ies o no el concep gene a ion and was ed ime and
money de eloping a concep ha is unable o pe o m well enough o become a iable
solu ion [55].
The abili y o new echnology o mee i s pe o mance a ge s will depend on i s
ma u i y and inno a ion capabili y. As he de elopmen ad ances, he expec ed accu acy
o he es ima es will imp o e; hus, he unce ain y band will na ow. Figu e 15 p esen s
indica i e uppe (desi ed) and lowe ( h eshold) bounds o i e de elopmen s ages
de i ed om [
56
,
57
]. S age 1 e e s o concep design, S age 2 o de ailed design, S age 3 o
scaled demons a ion, S age 4 o he alida ion o a single de ice and inally S age 5 o he
alida ion o a comple e wa e ene gy a m [7].
Ene gies 2022, 15, x FOR PEER REVIEW 23 o 30
Table 13. TA o he u ili y-scale gene a ion ma ke .
E al C i e ia Case 2 Case 4
Re e ence Ra ings PR DD TA
CF (%) 25 40 1.60 0.00 1.60
AF (%) 97 98 1.01 0.00 1.01
CAPEX (M EUR) 1.2 3 0.40 3.00 0.14
OPEX (k EUR) 92 210 0.44 3.00 0.16
FCR (%) 10 10.2 0.98 1.00 0.96
LCOE (EUR/MWh) 100 150 0.67 1.32 0.46
Assigning he DD le el o he sys em equi emen s o a wa e ene gy echnology un-
de de elopmen seems a qui e subjec i e and challenging ask. Despi e he di icul ies,
oo li le ime spen in he ea ly design phases can lead o gaps in unde s anding he p ob-
lem equi emen s, limi ed oppo uni ies o no el concep gene a ion and was ed ime
and money de eloping a concep ha is unable o pe o m well enough o become a iable
solu ion [55].
The abili y o new echnology o mee i s pe o mance a ge s will depend on i s ma-
u i y and inno a ion capabili y. As he de elopmen ad ances, he expec ed accu acy o
he es ima es will imp o e; hus, he unce ain y band will na ow. Figu e 15 p esen s
indica i e uppe (desi ed) and lowe ( h eshold) bounds o i e de elopmen s ages de-
i ed om [56,57]. S age 1 e e s o concep design, S age 2 o de ailed design, S age 3 o
scaled demons a ion, S age 4 o he alida ion o a single de ice and inally S age 5 o he
alida ion o a comple e wa e ene gy a m [7].
Figu e 15. Expec ed accu acy ange pe de elopmen s age.
Fo ins ance, he OPEX pe o mance a io o 0.44 in Table 11 could ha e had a DD
le el 1 a concep design (S age 1) bu would inc ease o 3 in he design phase (S age 2,
TRL 4) o e en could be a ed 9 o la e s ages. The inno a ion capabili y is limi ed as he
echnology ma u es and he e o e he PR should be penalised wi h a highe DD a la e
design s ages. Con e sely, an ea ly TRL opens he oom o imp o emen s h ough inno-
a ion. The same unde lying idea is exp essed by Webe [5] in he gene ic WEC de elop-
men ajec o ies displayed o e a TRL-TPL ma ix. Fundamen al sys em changes a e only
easible and a o dable a low TRLs. Cos educ ion and imp o ed pe o mance o ma-
u e echnologies a e mainly limi ed o lea ning by doing and economies o scale.
Figu e 15. Expec ed accu acy ange pe de elopmen s age.
Fo ins ance, he OPEX pe o mance a io o 0.44 in Table 11 could ha e had a DD le el
1 a concep design (S age 1) bu would inc ease o 3 in he design phase (S age 2, TRL 4) o
e en could be a ed 9 o la e s ages. The inno a ion capabili y is limi ed as he echnology
ma u es and he e o e he PR should be penalised wi h a highe DD a la e design s ages.
Con e sely, an ea ly TRL opens he oom o imp o emen s h ough inno a ion. The same
unde lying idea is exp essed by Webe [
5
] in he gene ic WEC de elopmen ajec o ies
displayed o e a TRL-TPL ma ix. Fundamen al sys em changes a e only easible and
Ene gies 2022,15, 2624 23 o 30
a o dable a low TRLs. Cos educ ion and imp o ed pe o mance o ma u e echnologies
a e mainly limi ed o lea ning by doing and economies o scale.
As men ioned in Sec ion 2.3, he DD may also be de ined by undamen al limi s.
Table 14 p esen s he lis o FR, MOP and possible ac o s ha may es ic he inno a ion
capabili y. I can be no ed ha he undamen al limi s a e de ined ei he by a ibu es o he
sys em design o he Ex e nal Sys ems ha in e ac wi h i . Fo ins ance, he deploymen
si e de ines he wa e ene gy esou ce and he dis ance o he poin o connec ion. Simila ly,
he se ice essels a ailable dic a e he cha e cos . The echnology de elope canno
modi y he a ibu es o he Ex e nal Sys ems bu selec s hose loca ions ha a e mos
app op ia e, hus cons aining he o al add essable ma ke o he echnology.
Table 14. Deg ee o di icul y ac o s o FR.
Id MOP Fac o s
FR1 No malised Cap u e Wid h (Cwn)
Wa e ene gy esou ce a he deploymen si e
FR2 T ans o ma ion E iciency (η ) No. o ans o ma ion s eps
FR3 Deli e y E iciency (ηd) Dis ance o poin o connec ion
FR4 Reliabili y (MTBF = 1/λ) No. o componen s in se ies
FR5 Main ainabili y (MTTR = 1/µ) Time o main enance ope a ion
FR6 Manu ac u abili y (MANEX) Cos o aw ma e ials
FR7 Ins allabili y (INSTEX) Cos o essels
FR8 Repai abili y (REPEX) No. o ips
FR9 Su i abili y (SURV) Sa e y class
FR10 En i onmen al Impac Sco e (EIS) En i onmen al p essu e
O he undamen al limi s a e ela ed o he design o he wa e ene gy de ice. The
numbe o ans o ma ion s eps in he PTO, he complexi y o he p oduc wi h componen s
connec ed in se ies o he sa e y class a e examples o a ibu es in which he echnology
de elope has ull con ol. Discon inued echnologies such as “Wa eBob” o “Pelamis”,
wi h p o en componen s bu complex PTOs [
58
], should ha e had ex emely high compo-
nen eliabili y o mee app op ia e sys em eliabili y. In ac , o achie e sys em eliabili y
o 90% wi h i e componen s in se ies, he indi idual eliabili y should be 98%. The same
could be said o he PTO e iciency. The numbe o ans o ma ion s eps will es ic he
capabili y o he echnology o mee he gi en h esholds.
5. Conclusions
This pape has p esen ed a no el me hodology o he holis ic assessmen o wa e
ene gy capabili ies in a ious ma ke applica ions. I has been implemen ed in he en-
i onmen al, s akeholde and unc ional domains. In his app oach, wo ma ix-based
modelling me hods, namely AHP and QFD, a e combined in a wa e all manne o ensu e
he p ope connec i i y o weigh s and o limi he subjec i i y o and dependence on expe
judgemen s. So a , me hods based on weigh s ha e only been applied sepa a ely and in a
single s ep in wa e ene gy. Mo eo e , he combina ion wi h LSP adds mo e g anula i y o
he agg ega ion s ep han cu en me hods.
The quali a i e assessmen has esul ed in e y di e en ankings o Sys em D i e s
(SD) and S akeholde s (SH) o he wo ma ke applica ions conside ed. U ili y-scale
is mainly mo i a ed by Economic and Poli ical ac o s, whe eas he emo e communi y
gene a ion ma ke is mainly d i en by Social ac o s. The de elopmen o wa e ene gy
echnologies is p ima ily in luenced by he needs o he Owne o u ili y-scale gene a ion
and he Go e nmen o emo e communi y p ojec s. Howe e , when analysing S akeholde
Requi emen s (SR) and Func ional Requi emen s (FR), he in luence o he applica ion
ma ke in he de elopmen o wa e ene gy echnologies is g ea ly educed.
The quan i a i e assessmen suppo s he p e ious inding. The small a ia ion in
he weigh s o he wo applica ion ma ke s esul s in e y simila Global Me i (GM) in
all six case s udies. In gene al, he GM dec eases as he a o dabili y (LCOE) inc eases.
Ene gies 2022,15, 2624 24 o 30
The Comme cial Achie abili y (CA) enables compa ing echnologies o di e en ma ke
applica ions in a mo e objec i e manne . Fo ins ance, case s udy 4 is mo e a ac i e wi h
a e e ence p ice o 300 EUR/MWh han cases 2 and 3 o u ili y-scale gene a ion. The
Technical Achie abili y (TA) concep o e s a means o concen a e he inno a ion e o s
be o e p oceeding o he nex de elopmen s age.
The echnology-agnos ic e alua ion o wa e ene gy capabili ies can be used by wha -
e e s akeholde and a any s age o echnology de elopmen . Howe e , he me hod elies
upon he es ima ion o he di e en e alua ion c i e ia. To o e come his limi a ion, u u e
wo k will ex end he implemen a ion o his me hodology o he physical domain. The
unc ional alloca ion o physical ealisa ions will allow de ec ion o con lic s leading o
ade-o s which mus be add essed wi h s uc u ed inno a ion me hods such as TRIZ [
59
].
Au ho Con ibu ions:
Concep ualiza ion, P.R.-M., V.N. and J.M.B.; Me hodology, in es iga ion and
w i ing, P.R.-M.; Valida ion, e iew and edi ing, V.N., J.M.B. and H.J.; Funding acquisi ion, J.M.B. All
au ho s ha e ead and ag eed o he published e sion o he manusc ip .
Funding: This esea ch ecei ed no ex e nal unding.
In o med Consen S a emen : No applicable.
Da a A ailabili y S a emen : No applicable.
Acknowledgmen s:
The au ho s would like o hank he Basque Go e nmen h ough he esea ch
g oups IT1514-22 and GIU19-029. They a e also g a e ul o he 64 in e na ional expe s in wa e
ene gy ha olun a ily con ibu ed o he p io i isa ion exe cise o ex e nal o ces o he wo ma ke
applica ions. The knowledge gained om he analysis o esponses p o ides a solid basis o he
objec i e e alua ion o wa e ene gy echnologies.
Con lic s o In e es :
The au ho s decla e no con lic o in e es . The unde s had no ole in he design
o he s udy; in he collec ion, analyses, o in e p e a ion o da a; in he w i ing o he manusc ip , o
in he decision o publish he esul s.
Abb e ia ions
The ollowing abb e ia ions a e used in his manusc ip :
A A i hme ic mean
AF A ailabili y Fac o
AHP Analy ical Hie a chy P ocess
CA Comme cial A ac i eness
CAPEX Capi al Expendi u e
CF Capaci y Fac o
CW Cap u e Wid h
DD Deg ee o Di icul y
EIS En i onmen al Impac Sco e
EPCI Enginee ing, P ocu emen , Cons uc ion and Ins alla ion
FAST Func ional Analysis and Sys em Technique
FCR Fixed Cha ge Ra e
FR Func ional Requi emen s
G Geome ic mean
GM Global Me i
H Ha monic mean
HoQ House o Quali y
LCOE Le elized Cos o Ene gy
LSP Logic Sco ing o P e e ence
MOE Measu es o E ec i eness
MOP Measu es o Pe o mance
MR Manu ac u ing Requi emen s
Ene gies 2022,15, 2624 25 o 30
MTBF Mean Time be ween Failu es
MTTR Mean Time o Repai
O&M Ope a ion and Main enance
OPEX Ope a ional Expendi u e
PESTLE Poli ical, Economic, Social, Technological, Legal and En i onmen al
PPA Powe Pu chase Ag eemen
PR Pe o mance Ra io
PTO Powe Take-O
QC Quasi-Conjunc ion
QFD Quali y Func ion Deploymen
TA Technical Achie abili y
TPL Technology Pe o mance Le els
TPM Technical Pe o mance Measu es
TR Technical Requi emen
TRIZ Teo iya Resheniya Izob e a elskikh Zada ch ( heo y o in en i e p oblem sol ing)
TRL Technology Readiness Le els
SE Sys ems Enginee ing
SIDS Small Island De elopmen Coun y S a es
SD Sys em D i e s
SH S akeholde s
SPV Special Pu pose Vehicle
SR S akeholde Requi emen s
VoC Voice o Cus ome
WEC Wa e Ene gy Con e e
Appendix A
The p io i isa ion o he di e en domain a ibu es used in he case s udies along
wi h hei espec i e in e ac ions is included below.
Table A1. Sys em D i e s (SD) o U ili y-scale gene a ion.
Sys em D i e s
SD1 SD2 SD3 SD4 SD5 SD6
Poli ical Fac o s
Economic Fac o s
Social Fac o s
Technological Fac o s
Legal Fac o s
En i onmen al Fac o s
To al
Weigh
SD1 Poli ical ac o s 0.28 0.34 0.27 0.22 0.29 0.29 1.68 28%
SD2 Economic ac o s 0.28 0.34 0.30 0.43 0.33 0.36 2.04 34%
SD3 Social ac o s 0.04 0.04 0.03 0.03 0.02 0.02 0.18 3%
SD4 Technological ac o s 0.28 0.17 0.23 0.22 0.24 0.22 1.37 23%
SD5 Legal ac o s 0.04 0.04 0.07 0.04 0.04 0.04 0.26 4%
SD6 En i onmen al ac o s 0.07 0.07 0.10 0.07 0.08 0.07 0.46 8%