sus ainabili y
A icle
No el Use o G een Hyd ogen Fuel Cell-Based Combined Hea
and Powe Sys ems o Reduce P ima y Ene gy In ake and
G eenhouse Emissions in he Building Sec o
Jo di Renau 1,*, Víc o Ga cía1, Luis Domenech 1, Ped o Ve dejo 1, An onio Real 1, Albe o Giménez 1,
Fe nando Sánchez 1, An onio Lozano 2and Félix Ba e as 2


Ci a ion: Renau, J.; Ga cía, V.;
Domenech, L.; Ve dejo, P.; Real, A.;
Giménez, A.; Sánchez, F.; Lozano, A.;
Ba e as, F. No el Use o G een
Hyd ogen Fuel Cell-Based Combined
Hea and Powe Sys ems o Reduce
P ima y Ene gy In ake and
G eenhouse Emissions in he
Building Sec o . Sus ainabili y 2021,
13, 1776. h ps://doi.o g/10.3390/
su13041776
Academic Edi o : And ás Rei h
Recei ed: 30 Decembe 2020
Accep ed: 2 Feb ua y 2021
Published: 7 Feb ua y 2021
Publishe ’s No e: MDPI s ays neu al
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ia ions.
Copy igh : © 2021 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
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dis ibu ed unde he e ms and
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A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
1Technical School o Design, A chi ec u e and Enginee ing (ESET), Ca denal He e a CEU
Uni e si y (UCHCEU)—CEU Uni e si ies, C/San Ba olomé55, 46115 Al a a del Pa ia ca, Valencia, Spain;
[email p o ec ed] (V.G.); [email p o ec ed] (L.D.); [email p o ec ed] (P.V.);
[email p o ec ed] (A.R.); [email p o ec ed] (A.G.); [email p o ec ed] (F.S.)
2LIFTEC, CSIC-Uni e si y o Za agoza, C/Ma ía de Luna 10, 50018 Za agoza, Spain; [email p o ec ed] (A.L.);
[email p o ec ed] (F.B.)
*Co espondence: jo di. [email p o ec ed]
Abs ac :
Achie ing Eu opean clima e neu ali y by 2050 equi es u he e o s no only om he
indus y and socie y, bu also om policymake s. The use o high-e ficiency cogene a ion acili ies
will help o educe bo h p ima y ene gy consump ion and CO
2
emissions because o he inc ease in
o e all e ficiency. Fuel cell-based cogene a ion echnologies a e ele an solu ions o hese poin s o
small- and mic oscale uni s. In his esea ch, an inno a i e and new uel cell-based cogene a ion
plan is s udied, and i s pe o mance is compa ed wi h o he cogene a ion echnologies o e alua e
he po en ial educ ion deg ee in ene gy consump ion and CO
2
emissions. Fou ene gy consump ion
p ofile da ase s ha e been gene a ed om eal consump ion da a o di e en dwellings loca ed in
he Medi e anean coas o Spain o pe o m nume ical simula ions in di e en ene gy scena ios
acco ding o he uel used in he cogene a ion. Resul s show ha he uel cell-based cogene a ion
sys ems educe p ima y ene gy consump ion and CO
2
emissions in buildings, o a deg ee ha
depends on he hea - o-powe a io o he consume . P ima y ene gy consump ion a ies om
40% o 90% o he o iginal p ima y ene gy consump ion, when hyd ogen is p oduced om na u al
gas e o ming p ocess, and om 5% o 40% o he o iginal p ima y ene gy consump ion i he
cogene a ion is ueled wi h hyd ogen ob ained om enewable ene gy sou ces. Simila educ ion
deg ees a e achie ed in CO2emissions.
Keywo ds: hyd ogen; PEM uel cells; cogene a ion; building sus ainabili y; ene gy sa ing
1. In oduc ion
Eu ope aims o achie e clima e neu ali y by 2050, which means ne -ze o g eenhouse
gas emissions. En i e socie y and economic sec o s mus join his ask o each he final
objec i e, om indus y o mobili y, building, ag icul u e, e c. Building sec o in Eu ope
consumed 40% o he final ene gy in 2018, wi h jus household being 26% o he final
ene gy, simila o he indus y sec o [
1
]. Acco ding o he Spanish “Ins i u o pa a la
Di e sificación y Aho o de la Ene gía (IDAE)” epo [
2
], space hea ing and sani a y ho
wa e a e esponsible o 58% o 75% o he final ene gy consump ion in fla s and single-
amily houses in Spain, espec i ely. Single- amily houses accoun o he bigges ene gy
sha e supplied om enewable ene gy, which is close o 40% in he Medi e anean a ea.
Howe e , his is no enough o mee he 2050 EU objec i e, because 47% o he ene gy
supply s ill comes om ossil uels. The Ene gy Pe o mance o Buildings Di ec i e (EPBD)
(2010/31/EU) [
3
] is he legisla i e amewo k “ o achie e a high ene gy e ficiency and
deca bonize building s ock by 2050”. EPBD s a es ha om 31 Decembe 2020 all new
edifica ions mus be nea ly ze o-ene gy buildings (nZEB). These a e “buildings wi h a
Sus ainabili y 2021,13, 1776. h ps://doi.o g/10.3390/su13041776 h ps://www.mdpi.com/jou nal/sus ainabili y
Sus ainabili y 2021,13, 1776 2o 19
e y high ene gy pe o mance and he low amoun o ene gy ha hese buildings equi e
comes mos ly om enewable sou ces”. P ima y ene gy consump ion analysis is how
he EPBD e alua es he building ene gy e ficiency due o he a ie y o ene gy sou ces
ha a e used. “The concep o p ima y ene gy a emp s o p o ide a simple me ic o all
o ms o ene gy ha a e supplied o, ansmi ed h ough, a defined bounda y” [
4
]. The
EPBD lea es he membe s a es o de e mine he me hodology o calcula e he p ima y
ene gy ac o and CO
2
emissions o each end-use ene gy sou ce depending on he ene gy
supply g id ci cums ances. Imp o ing ene gy e ficiency and he sha e o enewable sou ces
a e also main a ge s o he Spanish Go e nmen , as hey a e eflec ed in he In eg a ed
Na ional Ene gy and Clima e Plan 2021–2030 [
5
]. Acco ding o his plan, high-e ficiency
enewable cogene a ion acili ies a e going o be pa o he comp ehensi e s a egy o
ene gy e ficiency in ci ies.
2. Backg ound
Cogene a ion, also known as combined hea and powe sys em (CHP), shows he
abili y o dec ease p ima y ene gy consump ion and educe g eenhouse gas emissions due
o he inc ease in building ene gy e ficiency [
6
,
7
]. The mal ene gy demand can be supplied
by a hea e o a boile , bu he use o he CHP echnology could p o ide he same he mal
ene gy consump ion and a ac ion o he whole elec ical demand depending on he CHP
echnology used. CHP echnologies mus be easily scalable o low powe a ios o make
hem sui able o esiden ial applica ions. CHP sys ems o buildings can be classified
depending on he a ed he mal powe as mic o- (1–5 kW) and small-scale (
≤
50 kW)
uni s [
8
]. Because CHP sys ems p oduce he ene gy a he poin o use, hey can be e e ed
as decen alized ene gy sou ces [
9
]. This ad an age o decen alized gene a ion includes
an imp o ed ene gy e ficiency, which means an op imized uel u iliza ion ha esul s in
dec eased CO
2
emissions and p ima y ene gy consump ion and a educ ion in he na ional
ansmission losses, ha accoun o 2%–11% o he losses in he Eu opean ansmission
ne wo k [
10
]. Howe e , benefi s o he dis ibu ed gene a ion a e only achie able i
he e is a p ope ene gy managemen be ween gene a ion and consump ion [
10
]. P ope
managemen would equi e o an ene gy s o age sys em. Elec ical ene gy s o age (EES)
imp o es he sel -consump ion a io o small CHP uni s [
11
] and he mal ene gy s o age
(TES) elimina es sys em o e size and also op imizes he use o p oduced ene gy [
12
]. All
he CHP uni s conside ed in his pape will in eg a e bo h EES and TES sys ems.
Figu e 1shows he di e en CHP echnologies sui able o be ins alled in a esiden ial
building [
13
]. The zones ha e been delimi ed using he echnical pa ame e s ob ained
om he “Cogen Challenge P ojec ” documen [
14
], whe e mic o-scale and small-scale
cogene a ion echnologies a e analyzed. Each echnology is ep esen ed as a colo ed
uzzy a ea, delimi ed by ou s aigh lines, wo hick solid lines and wo do ed ones.
The mal/elec ical e ficiency is indica ed in he e ical axis and he mal/elec ical a ed
powe in he ho izon al one. The ep esen ed su ace co e s he powe ange o he
applicabili y in buildings, om single- amily houses o blocks o apa men s. The figu e
can be ead as ollows. Solid lines ep esen wo possible CHP configu a ions in each
echnology. The igh -side solid line o each a ea indica es he mos common o ypical
“small-scale” uni o he echnology and he le -side one co esponds o he smalles CHP
uni possible as indica ed in [
14
]. Solid lines can be unde s ood as an ope a ing poin
o he eal CHP uni , whe e he uppe ex eme o he line is o he CHP uni he mal
cha ac e is ic and he lowe one co esponds o he elec ical one.
Sus ainabili y 2021,13, 1776 3o 19
Figu e 1. Compa ison o he echnical pa ame e s in di e en gas- ueled combined hea and powe echnologies.
Fo example, he solid line o he igh side in he blue a ea means he “ ypical small-
scale gas u bine CHP uni ” as s a ed in [
14
], which means a a ed elec ical powe o
250 kW and a ound 330 kW o i s a ed he mal powe . The co esponding con e sion
e ficiencies, a ound 30% and 40% o he elec ical and he mal ene gies espec i ely, a e
ead in he e ical axis. On he le side o he same uzzy a ea, he elec ical and he mal
a ed powe o he smalles gas u bine CHP uni analyzed a e 30 kW (26%) and 50 kW
(47%), espec i ely. Bo h uni s a e connec ed wi h he do ed lines ha c ea e he uzzy
a ea, which can be conside ed as an ope a ional cha o he echnology in he small-scale
use. In o he wo ds, his a ea can be unde s ood as he ope a ing ange o each echnology.
Acco ding o Figu e 1 he ollowing conclusions can be ex ac ed:
•
S i ling CHP echnology is sui able o any kind o uel. I s pe o mance is simila
o ha o a boile due o i s high he mal ene gy con e sion e ficiency wi h he
addi ional benefi o he elec ical p oduc ion ha can compensa e some o he building
in akes. Ne e heless, he hea - o-powe (H P) a io, which is an impo an selec ion
pa ame e [
15
], is oo high o esiden ial uses meaning ha he ene gy p oduc ion is
unbalanced wi h espec o he he mal ene gy demand. S i ling echnology is included
in Figu e 1cha due o i s scien ific in e es , bu i is no going o be conside ed in he
p esen analysis.
•
Gas u bine and in e nal combus ion engine (Gas ICE) a e ma u e echnologies ha
can be scaled om small o la ge sizes. Bo h can consume na u al gas, which is a
uel widely a ailable in he esiden ial building sec o , bu i s consump ion should be
minimized due o en i onmen al cons ain s. The use o pu e hyd ogen in o ICEs and
u bines has se e al echnical p oblems ha is now unde esea ch and s ill need o be
imp o ed [16]. In his pape bo h op ions a e going o be analyzed.
•
Fuel cell-based CHP (FC-CHP) is he mos p omising echnology due o i s balanced
hea - o-powe a io, be e adap ed o he esiden ial building ene gy p ofiles, which
a e mo e elec ici y demanding [
17
]. Fuel cell p esen s he highes elec ical con e sion
e ficiency. Fuel cells a e easily scaled om ew wa s o kilowa s o hund eds o
Sus ainabili y 2021,13, 1776 4o 19
kilowa s keeping a cons an ene gy con e sion e ficiency when hey a e ueled om
pu e hyd ogen [
18
–
21
]. When his pu e hyd ogen comes om a g een p oduc ion
p ocess, he ene gy ob ained can also be conside ed as g een o ca bon- ee.
FC-CHP a e classified as a unc ion o he uel cell echnology used in he powe
uni . The mos common echnologies in comme cial uni s a e based on polyme exchange
memb ane uel cells (PEMFC), The mos success ul examples o hese sys ems can be ound
in Japan and Eu ope [
22
,
23
]. PEMFC can be classified in o low- (up o 80
◦
C) and high-
empe a u e ( om 120
◦
C o 180
◦
C) de ices. They only di e in he wo king empe a u e
equi ed by he polyme used as solid elec oly e memb ane. Low- empe a u e PEM uel
cell-based CHP sys ems a e he mos common. In his pape bo h PEM echnologies a e
conside ed, paying special a en ion o a high- empe a u e PEM uel cell-based mic o-
CHP sys em specifically concei ed in he amewo k o he MICAPEM p ojec ha is
been in eg a ed in o an exis en nea ly-ze o ene gy house, de eloped and buil o he
in e na ional Sola Deca hlon 2012 con es [
24
,
25
]. The use o high- empe a u e PEMFC is
p omising due o he imp o ed chemical kine ics in he elec odes, be e ole ance o CO
impu i ies in he uel, simplifica ion o he wa e managemen because i is p oduced in
apo phase and simple and compac hea eco e y sys em because o he highe en halpy
o he he mal ene gy [
26
,
27
]. A majo i y o he significan s udies in he li e a u e in ol ing
a high- empe a u e PEM uel cell-based CHP sys em a e heo e ical wo ks [
28
–
31
] Only
one epo on es s in an expe imen al acili y has been ound [32].
The objec i e o his esea ch pape is o expose, using nume ical simula ions, how uel
cell-based CHP sys ems can d i e a po en ial educ ion o p ima y ene gy consump ion
and CO
2
emissions in he building sec o . Nume ical simula ions a e pe o med using
p elimina y esul s om he cha ac e iza ion o he high- empe a u e PEM uel cell p o o-
ype buil and es ed o be ins alled in a demons a i e scale CHP acili y. Once ins alled,
he CHP echnology will be e alua ed and a no el oil-based e ige a ion sys em o HT-
PEMFC will also be es ed, as explained in Sec ion 3.3. In he same p ojec amewo k, a
hyd ogen elec olyze in eg a ed wi h he sola sys em is also being ins alled o link wi h
he g een hyd ogen sou ce equi emen objec i e.
3. Me hods and Ma e ials
Nume ical simula ions we e pe o med using he elec ical and gas ene gy consump-
ions om ou eal dwellings in he eas coas (Medi e anean a ea) o Spain. Wea he
in his egion can be classified as a “Csa clima e” wi h ho , d y summe s and cool, we
win e s, acco ding o Köppen clima e in e na ional classifica ion [33].
Using he in o ma ion om ac ual ene gy in oices, ou daily consump ion da ase s
ha e been c ea ed. Fou 10-apa men building consump ion p ofiles we e de e mined con-
side ing simul aneously ac o s om he single dwelling da ase s. The selec ed dwellings
a e desc ibed as ollows:
•
Id 1: 140 m
2
wo-s o y e aced house, ou inhabi an s. The gas consume s a e he
boile , used o hea ing and on-demand sani a y ho wa e , and he ki chen cook op.
•
Id 2: 75 m
2
fla , ou inhabi an s. Na u al gas is consumed only in he on-demand
wa e hea e . Elec ical induc ion cook op.
•
Id 3: 90 m
2
fla , ou inhabi an s. Gas-powe ed boile o hea ing and ho wa e
p oduc ion. Elec ical induc ion cook op.
•
Id 4: 90 m
2
fla , h ee inhabi an s. Na u al gas-powe ed on-demand wa e hea e .
Elec ical cook op and indi idual elec ical oil hea e s in each bed oom.
Da a ob ained om he gas and elec ical u ili y in oices a e one-mon h agg ega ed in-
o ma ion ha mus be s a is ically ea ed o c ea e he use ul da ase s o simula e he daily
ene gy demand o he use s. The nume ical ea men has consis ed o no mal andomized
daily ene gy consump ion es ima ion using he daily seasonal a e age consump ion alues
and i s seasonal da a s anda d de ia ion (Figu e 2). This p ocess was applied o bo h
ene gy in oices (elec ici y and gas), aking he billing da e in o accoun o co ec he
consump ion da a o he di e en ene gy supplie s.
Sus ainabili y 2021,13, 1776 5o 19
Mon hly in oice
Consump ion pe day
Yea da ase . Mon hly
agg ega ed
Seasonal a e age
consump ion and de ia ion
S a is ical
Randomiza ion
Da ase
Figu e 2.
S a is ical analysis om he annual ene gy in oices o andomize a daily ene gy consump-
ion da ase o each building using seasonal alues (a e age and s anda d de ia ion).
The esul s o he ea men o he nume ical da a can be obse ed in Figu e 3, whe e
he e ical axis is he daily elec ical consump ion and he ho izon al one ep esen s
he daily he mal ene gy one. Da ke do s a e he daily consump ion calcula ed om
he u ili y in oices and he “x” ma ke s a e he andomized alues ob ained om he
nume ical ea men .
Figu e 3.
Resul o he nume ical ea men o he u ili y in oices o c ea e an ene gy consump ion da ase o each dwelling.

Sus ainabili y 2021,13, 1776 6o 19
Elec ical and he mal da a in Figu e 3a e co ela ed alues, whe e wo main endencies
can be obse ed. Dwellings wi h gas-powe ed hea ing acili ies (Id 1 and Id 3) show a
g ea e he mal ene gy demand o hea ing seasons. This esul s in wo di e en “x-clouds”:
one ene gy demand cloud a he igh - op side o he cha (Id 1: om 30 o 50 kWh
h.
,
Id 3: om 15 o 30kWh
h.
), whe e he hea ing demand can be de ec ed; and a second cloud
below 15 kWh
h.
ha is o e lapped wi h he wo less- he mal demanding dwellings (Id 2
and Id 4). In he case o dwellings Id 2 and Id 4, he seasonal a ia ion is no o ious in he
e ical axis due o he inc ease in he elec ical ene gy demand du ing he hea ing season
caused by he use o elec ical hea e s. When he he mal demand is limi ed o ho wa e ,
he ene gy consump ion is unc ion o he numbe o inhabi an s as can be obse ed o he
daily ene gy he mal alues o Id 2 and Id 4, espec i ely. Hea - o-powe (H P) is calcula ed
as he he mal demand o e he elec ical demand. This a io is a season-dependen alue,
and no mally a yea -based calcula ion is p o ided. The esul s ob ained wi h he da ase s
so ed in dec easing o de a e 3.4 (Id 1), 2.3 (Id 3), 1.5 (Id 2) and 0.7 (Id 4).
Conside ing each dwelling da ase , ou 10-dwelling buildings we e c ea ed using a
andomized ac o o simula e a cen alized CHP. Hea - o-powe a ios o he building
da ase s a e simila in alue and o de .
3.1. Simula ion Algo i hm
Cogene a ion acili ies a e designed o supply he use ’s he mal ene gy demand and
o p o ide elec ici y as a seconda y ene gy sou ce [
15
]. Indus ial-scale CHPs use he
hea di ec ly, bu esiden ial-scale CHPs equi e a he mal ene gy s o age sys em (TES)
o manage he ene gy demand a oiding sys em o e sizing [
12
,
34
]. Because o his, wo
simplifica ions ha e been assumed o he simula ion analysis. The fi s simplifica ion is
ha he mal ene gy demand is supplied daily om a he mal ene gy bu e
(Figu e 4)
, ha
can be cha ged wi h he CHP uni and discha ged by he use wi hou any ime dependence.
The second simplifica ion is ha he elec ical ene gy is also managed using an elec ical
ene gy s o age sys em (EES) wi h he sui able capaci y o manage he daily consump ion.
EES ensu es he gene a ion–consump ion co ela ion [
24
]. Elec ical ene gy su plus is daily
expo ed o he elec ical g id.
CHP
CHP
Fuel
The mal
demand
Elec ical
demand
The mal
bu e
Elec ical
bu e


 

 
Elec ical G id Back up hea e Gas
Figu e 4. Cogene a ion unc ioning block diag am o he simula ion algo i hm.
Figu e 4shows he unc ioning block diag am o he CHP sys em o he simula ion
algo i hm p og ammed in a Py hon [
35
] sc ip ha is g aphically desc ibed in Figu e 5.
The code is used o e alua e a day-by-day ene gy balance om he use da ase o each
indi idual dwelling and he 10-dwelling buildings.
Sus ainabili y 2021,13, 1776 7o 19
The mal
demand (

)
Elec ical
demand (

)
CHP he mal a ed
powe ( &
)
Es ima ed daily
ope a ion ime
()
The mal
pe o mance (

)
≥ 24 hou s < 24 hou s


%&
$$


!
%

#


%&
$$


!
%

!
%






%
!
$


$



%

#



> 0 

≤ 0

"
%



%

"
%


%

Figu e 5. Py hon sc ip code algo i hm o day- o-day ene gy analysis decision diag am.
The calcula ion p ocess s a s wi h he e alua ion o he o al ime ha he CHP
equi es o p oduce he daily he mal demand, which will depend on he a ed he mal
powe o he CHP echnology used. This ime can be calcula ed wi h he equa ion:
=QD
.
QCHP·ηQ
, (1)
whe e
QD
is he daily he mal ene gy demand,
.
QCHP
is he a ed CHP he mal powe and
ηQ
he he mal e ficiency o he ene gy con e sions equi ed o eed he demand. Ene gy
Sus ainabili y 2021,13, 1776 8o 19
con e sions a e due o he ene gy ex ac ion p ocess o he he mal ene gy om he bu e
used o ma ch he ene gy p oduc ion and demand (Figu e 4). The same e ficiency (85%) is
conside ed o all he CHP echnologies. The esul o Equa ion (1) is he ime ha he CHP
equi es o p oduce he daily he mal ene gy, whe e wo di e en si ua ions can occu . I
he o al ime calcula ed is lowe han 24 h, he CHP echnology is capable o p o ide he
en i e daily he mal demand and no back-up ene gy sys em will be equi ed. In case o a
CHP echnology ha is no sui ably sized he o al es ima ed ime can be g ea e han 24 h,
and he maximum achie able ene gy will be he ob ained om he CHP uni wo king a
he a ed powe he en i e day. In his case, i is conside ed ha he sho age o he mal
ene gy will be compensa ed by a back-up sys em, e.g., a boile , using na u al gas as uel.
The uel consump ion o p oduce he he mal ene gy wi h he CHP can be de e mined as:
Q uel =QCHP
ηQ
CHP
, (2)
whe e
QCHP
s ands o he he mal ene gy p oduced by he CHP uni , and
ηQ
CHP
is he
ene gy pe o mance o he he mal ene gy flow in he CHP sys em. The back-up en-
e gy (
Qbackup
) equals he lack o he mal ene gy because he alue comes om he boile
consump ion as can be ead in Figu e 5.
The elec ical ene gy p oduced wi h he CHP uni depends on he CHP gas consump-
ion and he elec ical e ficiency o he uni , ηW
CHP, as:
WCHP =Q uel·ηW
CHP·ηW, (3)
whe e
ηW
is addi ional elec ical e ficiency due o he ene gy con e sions. The elec ical
ene gy p oduced will be used o p o ide he daily elec ical ene gy demand (
WD
). The
elec ical ene gy balance is de e mined as:
Wbal =WCHP −WD. (4)
A ending o he sign alue epo ed om his equa ion, elec ical ene gy will be
impo ed om he g id when i is nega i e and expo ed o sold o he g id i i is posi i e.
3.2. P ima y Ene gy Fac o s
P ima y ene gy (PE) is a concep used o compa e di e en kinds o ene gy sou ces,
bu he scale used in he calcula ions is ele an [
4
,
36
]. In his esea ch, he p ima y ene gy
ac o s published by he Spanish Go e nmen in 2016 [
37
] a e used o de e mine he
building pe o mance equi ed o legaliza ion. Co esponding alues a e summa ized in
Table 1 o bo h u ili ies conside ed, namely, he na ional elec ical g id and he na u al gas
supply acili y. The PE ac o depends on he ene gy ca ie and ela es he p ima y ene gy
consumed o p o ide one kWh o he end-use , in his case he final ene gy consumed by
he esiden ial use s. PE ac o s a e also di ided in o enewable and non- enewable. As
can be obse ed in Table 1, enewable ac o s a e smalle ha non- enewable ones, bu hey
a e alues abo e ze o. This means ha a ce ain amoun o ene gy is equi ed o se e he
enewable sou ce, i.e., main enance asks.
Table 1.
P ima y ene gy ac o s and CO
2
con e sion ac o es ablished by he Spanish Go e nmen
o he elec ical and na u al gas u ili ies.
P ima y Ene gy
kWhp ima y/kWhfinal
No Renewable Sou ce
P ima y Ene gy
kWhp ima y/kWhfinal
Renewable Sou ce
CO2Emission Fac o
kg CO2/kWhfinal
Na ional elec ical u ili y
1.954 0.414 0.331
Na u al gas u ili y 1.190 0.005 0.252
Sus ainabili y 2021,13, 1776 9o 19
No only he PE, bu also he CO
2
emissions will be compa ed o de e mine he benefi s
o he cogene a ion echnologies. The PE educ ions a e measu ed om he ini ial si ua ion,
and hey can be e alua ed using he equa ion:
PE =QD· PE
g+WD· PE
e, (5)
whe e
PE
s ands o he p ima y ene gy ac o (subsc ip s g and e ep esen gas and
elec ici y, espec i ely),
QD
is he o al he mal ene gy demanded and
WD
s ands o he
o al elec ical ene gy. The PE consump ion wi h he use o a CHP sys em will depend on
he echnology. A gene al case is shown in Equa ion (6):
PECHP =Q uel +Qbackup· PE
g+WImp· PE
e−WExp· PE
e, (6)
whe e expo ed ene gy (
WExp
) is conside ed as a p ima y ene gy dec emen due o i s
dec easing e ec in p ima y ene gy consump ion. When hyd ogen o any o he uel
ob ained om enewable ene gy sou ces is used, he gas e ms (
Q uel
and
Qbackup
)in
Equa ion (6) can be neglec ed. Ca bon emissions can be calcula ed using he same equa ions,
jus eplacing he p ima y ene gy ac o s wi h he CO2emission ac o ( CO2).
CO2=QD· CO2
g+WD· CO2
eand (7)
COCHP
2=Q uel +Qbackup· CO2
g+WImp· CO2
e−WExp· CO2
e. (8)
3.3. Fuel Cell S ack and I s Cooling Sys em Design
The powe uni o he CHP in he p esen esea ch consis s o a p o o ype o high-
empe a u e PEM uel cell and i s no el cooling sys em ha we e designed and de eloped
specifically o his p ojec . The 40-cells high- empe a u e PEM uel cell s ack (HT-PEMFC)
is o med by 41 JP-945 g aphi e bipola pla es 280 mm high
×
195 mm wide
×
5mm
hick manu ac u ed by Me sen, as well as wo s ainless s eel end pla es whe e all he
connec o s o he eac an gases, H
2
and O
2
/ai , a e placed. The flowfield geome y in
bo h anode and ca hode sides consis ed o s aigh pa allel channels wi h a land- o-channel
a io o 1, as ecommended by he MEA manu ac u e . The anode side was o med by
47 channels 1 mm wide, 1.5 mm deep, and a o al leng h o 210 mm, while he ca hode side
is o med by 87 channels wi h a wid h o 1 mm and a dep h o 2 mm, and a o al leng h
o 120 mm. Wi h his design, p essu e losses we e minimized o 5.87 Pa in he anode and
2.6 Pa in he ca hode, ensu ing bo h he homogenous dis ibu ion o he eac an gases
o e he elec odes and he co ec wa e managemen . Comme cial high- empe a u e
memb ane-elec ode assemblies (MEAs) G1018 Dapozol-110, manu ac u ed by Danish
Powe Sys em (DPS) wi h a ec angula ac i e a ea o 163.5 cm
2
, we e used [
38
]. The
MEAs a e o med by phospho ic acid doped PBI polyme ic memb anes, wi h a nominal
hickness o 6
50 ±50 μm
, gas di usion laye s o non-wo en ca bon pape and a pla inum
load o 1.5 mg cm
−2
in bo h elec odes. The nominal hickness o he elec odes is 250
μ
m,
including he GDL, he mic opo ous laye and he ca alys laye . To ob ain he bes esul s,
a minimum comp ession a e o 13% is ad ised, as well as a ecommended wo king
empe a u e anging om 150
◦
C o180
◦
C. Figu e 6a shows he manu ac u ed p o o ype
de eloped by he PEMFC esea ch eam om LIFTEC-CSIC in Za agoza (Spain), which
has an ample expe ise in his field [
39
,
40
]. Figu e 6b shows he elec ical and he mal
pe o mance o he HT-PEMFC s ack. The e ical axes ep esen he ol age (le axis
and ed cu e) and he powe ( igh axis and g een cu es), and he ho izon al alues a e
he cu en p oduced by he elec ochemical de ice. Solid g een line co esponds o he
elec ical powe , and he dashed g een line is he es ima ed he mal powe .
Sus ainabili y 2021,13, 1776 16 o 19
he mal CHP uni s (“gas ICE” and “gas u bine”) esul in a wo s PE educ ion o all
dwellings due o he low ope a ing ime (see Figu e 12a) and, consequen ly, he lowes
elec ical ene gy p oduc ion (see Figu e 9a). The nega i e alue in he PE a io o uel-
cell-based CHP uni s is due o he elec ical ene gy su plus. Figu e 7a1 shows, again, an
op imal design poin in he “MICAPEM
a ed
” cha ac e is ics. Fo he 10-dwelling buildings,
he highe he powe he highe he PE educ ion due o he abili y o p o ide he ene gy
demands om a low consump ion o ca bon- ee uel o PE p oduc ion. The con a y can
be obse ed in Figu e 7a2 o he “na u al gas scena io”, whe e a g ea e uel consump ion
is penalized.
Figu e 8a1,a2 show he CO
2
educ ion esul s o he “gas- ueled scena io” o bo h
indi idual and building dwellings, espec i ely. The use o CHP in dwellings does no
ha e a ca bon emissions educ ion due o he highe gas consump ion because o he
e ficiency educ ion compa ed o he use o a boile . Ne e heless, he 10-dwelling building
simula ion shows ha CO
2
emissions a e lowe o he uel cell-based sys em due o he
elec ical gene a ion and he inc ease in global e ficiency. Simila ly, in bo h he “g een uel
scena io” and he “expec ed scena io”, he educ ion o CO
2
emission shows he same
beha io compa ed o he PE educ ion.
The size o he CHP sys em is an impo an design and a c i ical economical pa ame e .
The size o he CHP is di ec ly ela ed o he abili y o mee he ene gy demand, bu
indi ec ly ela ed o he ope a ion ime (and he economic iabili y). Figu e 11 shows he
sha e o he mal ene gy demand p oduced wi h he CHP sys em and Figu e 12 he sha e
o ope a ion hou s pe yea . The o al ope a ing ime o he smalle uni s o he “gas ICE”
and he “gas u bine” CHP uni s applied o low he mal demand consume s like a single
dwelling (Figu e 12a), makes i s use un iable (less han 5%-yea hou s). “Gas u bine”
uni s s ill a e un iable o ypical buildings in Spain (less han 20%-yea hou s). Con a y,
uel cell-based echnologies, due o hei lowe powe appea o be a be e solu ion o
CHP sys ems in he building sec o , ca. 80%-yea hou s in he bes cases. The low he mal
powe is no a handicap because uel-cell-based CHP sys ems a e ully scalable.
6. Conclusions
When he p ima y ene gy (PE) consump ion in Spanish buildings is calcula ed wi h
he o ficial ac o s summa ized in Table 1, which depend on he ene gy ca ie and i s ene gy
sou ce, i was demons a ed ha he elec ical ene gy ca ie is 1.6 imes mo e demanding
han he na u al gas om non- enewable sou ces. E en so, he e is a endency o elec i y
he consump ions because i is an ene gy ca ie ha can be mo e easily deca bonized. Some
indus ial hea ing sys ems a e elec ified due o he a ailabili y o powe ul ansmission
lines. Despi e o his, building cen alized hea ing sys ems a e no no mally elec ified
because o he limi a ions o elec ical g ids in he ci ies.
Fuel cell-based CHP sys ems a e a good solu ion o p o ide he ene gy demand o
hea ing and ho wa e in buildings, showing a dec ease in bo h PE consump ion and CO
2
emissions, e en i he hyd ogen is ob ained om na u al gas e o ming. Howe e , his
PE educ ion is di ec ly ela ed o he he mal ene gy con e sion e ficiency o he CHP
and he boile because in he bes si ua ion a 50% PE educ ion can be achie ed wi h an
ene gy p oduc ion o ca. 20% o he mal demand and ca. 50% o he elec ical demand.
When he uel cell-based CHP sys ems a e powe ed wi h ca bon- ee hyd ogen, he PE
educ ion is highe when he sys em is able o mee a big sha e o he ene gy demand, which
co esponds o a be e fi o he hea - o-powe a io be ween p oduc ion and demand. The
use o mic o-CHP uni s in eg a ed in o sma g ids can help o educe no only he he mal
and elec ical demand o he use bu also he elec ical demand om he nea by wi h he
p ope ene gy managemen .
The economic iabili y o uel cell-based CHP uni s is simila o o he echnologies
such as sola he mal sys ems ha a e p ojec ed o supply a maximum sha e o he he mal
demand, ensu ing he highe possible ope a ing ime. Based on he esul s o Figu e 12,

Sus ainabili y 2021,13, 1776 17 o 19
he op imal si ua ion co esponds o cen alized sys ems whe e he o al ope a ing ime is
abo e 80% o he yea -hou s and he he mal demand can be ully supplied.
Au ho Con ibu ions:
The fi s au ho , J.R., has aken lead on all he s eps o he esea ch and
w i ing p ocess. The es o au ho s ha e con ibu ed as ollow: esea ch me hodology, F.S., A.L. and
F.B.; simula ion, V.G., L.D. and A.R.; alida ion, P.V., A.G.; w i ing—o iginal d a p epa a ion, F.S.,
A.L. and F.B.; supe ision, F.S. and A.L.; w i ing— e iew and edi ing, F.S., A.L. and F.B. All au ho s
ha e ead and ag eed o he published e sion o he manusc ip .
Funding:
This esea ch was unded by he Sec e a ia o S a e o Resea ch o he Spanish Minis y
o Economy and Compe i i eness (DPI2015-69286-C3-1-R), he Spanish Minis y o Science and
Inno a ion (RTI2018-096001-B-C33), and he A agon Go e nmen (LMP246_18).
Ins i u ional Re iew Boa d S a emen : No applicable.
In o med Consen S a emen : No applicable.
Acknowledgmen s:
This wo k has been pa ially unded by he Sec e a ia o S a e o Resea ch o
he Spanish Minis y o Economy and Compe i i eness unde he p ojec MICAPEM ( e .: DPI2015-
69286-C3-1-R) and by he Spanish Minis y o Science and Inno a ion unde he p ojec DOVELAR
( e .: RTI2018-096001-B-C33). LIFTEC esea ch eam would also acknowledge he unded p o ided
by he A agon Go e nmen unde he p ojec LMP246_18.
Conflic s o In e es : The au ho s decla e no conflic o in e es .
Nomencla u e
Abb e ia ions
CHP Combined hea and powe sys em
EES Elec ical ene gy s o age sys em
EPBD Ene gy Pe o mance o Buildings Di ec i e (2010/31/EU)
H P Hea - o-powe ene gy a io
PE P ima y ene gy
PEMFC Polyme exchange memb ane uel cell
TES The mal ene gy s o age sys em
Va iables
COCHP
2CO2emissions om he combined hea and powe uni (kg)
CO2CO2emissions con e sion ac o , kg o CO2pe kWh o end-use ene gy
PE P ima y ene gy con e sion ac o , kWh o p ima y ene gy pe kWh o
end-use ene gy
.
QRa ed he mal powe o he combined hea and powe uni (kW)
Qbackup Back-up hea e ene gy flow (kWh)
QDDaily he mal ene gy demand (kWh)
Q uel Fuel ene gy flow in he combined hea and powe uni (kWh)
QCHP The mal ene gy p oduced by he combined hea and powe uni (kWh)
Es ima ed daily ope a ion ime o he combined hea and powe uni (h)
Wbal Elec ical ene gy balance (kWh)
WCHP Elec ical ene gy p oduced by he combined hea and powe uni (kWh)
WDDaily elec ical ene gy demand (kWh)
WExp Ne elec ical expo ed ene gy o he g id (kWh)
WImp Ne elec ical impo ed ene gy om he g id (kWh)
ηQThe mal e ficiency o supply he ene gy demand om he gene a ion
ηQ
CHP The mal ene gy pe o mance o he combined hea and powe uni
ηW
CHP Elec ical ene gy pe o mance o he combined hea and powe uni
ηWElec ical e ficiency o supply he demand om he gene a ion
Subsc ip s
e elec ici y
g gas
Sus ainabili y 2021,13, 1776 18 o 19
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