A icle
The Use o he Pho o ol aic Sys em in Combina ion
Wi h a The mal Ene gy S o age o Hea ing and
The moelec ic Cooling
Jan Sko ajsa * and Ma in Zalesak
Facul y o Applied In o ma ics, Tomas Ba a Uni e si y in Zlin, Names i T.G.Masa yka 5555, 760 01 Zlin,
Czech Republic; [email p o ec ed]
*Co espondence: [email p o ec ed]
Recei ed: 11 July 2018; Accep ed: 25 Sep embe 2018; Published: 28 Sep embe 2018


Abs ac :
The a icle is ocused on he esea ch o he usage o mode n accumula ion echnology.
The p oposed sys em is able o imp o e he he mal com o o building in e io s. Tha ex depic s
he echnology, which uses a pho o ol aics and o he enewable ene gy sou ces o ac i e hea ing
and cooling. The bases o he p esen ed echnology a e he phase change ma e ial and he mal
ene gy s o ages. So, i passi ely imp o es he he mal capaci y o he cons uc ions o he buildings.
Mo eo e , he e is a possibili y o use i o ac i e hea ing and cooling. The echnology con ains
he moelec ic assemblies, so, he e is a e y in e es ing possibili y o s o e he mal ene gy wi h
use o enewable ene gy sou ces (such as pho o ol aic sys em) and he moelec ic coole s side by
side. In he manusc ip , he e a e shown measu emen s and esul s o he ac i e ope a ing modes
o p oposed echnology. I was ound he echnology is able o wo k in ac i e hea ing and cooling
modes. I wo ks qui e well in ac i e hea ing mode. On he o he hand, he moelec ic cooling mode
had a p oblem wi h o e hea ing. In he end, he p oblem was sol ed and he cooling mode wo ks.
The measu emen s and esul s a e desc ibed in he ex .
Keywo ds:
PCM; he moelec ic cooling; enewable ene gy sou ces; pho o ol aic; he mal ene gy s o age
1. In oduc ion
The consump ion o ene gy by he building sys ems such as hea ing, en ila ion and cooling
sys ems (HVAC) a e s ill ising wi h he ongoing inc ease in demand o he mal com o [
1
].
Nowadays, he emissions and ene gy demand a e being dec eased by he use o he enewable
ene gy sou ces. O hose sou ces, sola , wind, o geo he mal ene gy and hea pumps, a e sui able
o buildings. These echnologies, howe e , a e no capable o dealing wi h an insu icien he mal
s o age capaci y o he s uc u es. A p esen , he p e e ence is o a pa ame e o su icien he mal
insula ion, bu ha does no add ess he accumula ion o he he mal ene gy. The buildings, which
a e mos p oblema ic, a e hose cons uc ed om ligh weigh ma e ials, such as wood o ligh weigh
conc e es. In hese, ou side hea load a ia ions du ing he day may cause inapp op ia e luc ua ions
o he ai empe a u e inside he buildings. The p oblem wi h ligh weigh s uc u es is ha hey
a e unable o s o e a su icien amoun o he mal ene gy ha limi s hei abili y o main ain s able
condi ions o he indoo en i onmen . As a consequence, he he mal com o is a ec ed. The mal
ene gy s o age add esses his p oblem. An op imal way o dec easing he consump ion o ossil
ene gy wi h inc easing he mal com o a he same ime is he use o elemen s o he mal ene gy
s o ages in combina ion wi h enewable ene gy sou ces, e.g. pho o ol aic sys em in combina ion wi h
he moelec ic coole s.
Appl. Sci. 2018,8, 1750; doi:10.3390/app8101750 www.mdpi.com/jou nal/applsci
Appl. Sci. 2018,8, 1750 2 o 15
1.1. The mal Ene gy S o age
The mal ene gy s o age (TES) is a empo a y cap u e o he mal ene gy in he o m o ho o
cold subs ances o la e u ilisa ion [
2
]. The s o ed he mal ene gy may be used o hea ing o cooling
applica ions. So, TES is use ul o add essing he misma ch be ween he supply and demand o
ene gy [
3
]. The p inciple o TES is based on a empe a u e di e ence (sensible TES) o change o phase
(la en TES). The ini ial s a e is a solid s a e when he hea is added, he solid subs ance is hea ing
up (sensible hea ), a e ha , a solid- o-liquid phase change ollows (la en hea ). When he hea is
s ill added, a liquid is hea ing up (sensible hea ) and hen, a liquid- o- apou phase change occu s
(la en hea ) and a e ha , sensible hea ing o he apou occu s (sensible hea ) [
4
]. As can be seen,
wo o ms o hea a e ecognized: sensible hea and la en hea . The p inciple o sensible hea s o age
is based on he ma e ial’s change o hea capaci y and empe a u e du ing he p ocess o cha ging
and discha ging [
5
]. In case o he sensible hea , he speci ic hea capaci y is he p ima y pa ame e .
I de e mines he amoun o ene gy needed o change he empe a u e o 1 kg o he subs ance by 1 K.
The amoun o sensible hea ene gy can be calcula ed by Equa ion (1).
Q=m·ZT
Ti
cpdT, (1)
whe e
mmass (kg),
Tiini ial empe a u e (K),
T inal empe a u e (K),
cpspeci ic hea capaci y (J kg−1K−1).
La en hea s o age is elian on he s o age ma e ial abso bing o eleasing hea as i unde goes a
solid o solid, solid o liquid o liquid o gas phase change o ice e sa [
5
]. Du ing he phase change,
he subs ance empe a u e is cons an . E en so, i sabili y o s o ing and eleasing a la ge amoun o
he mal ene gy. So, his is he eason why la en hea s o age is a mos e icien me hod o s o ing
he mal ene gy [
6
]. The quan i y o la en hea is de i ed om he di e ence in en halpy o he wo
ele an s a es.
The mal ene gy s o age ealised by phase change ma e ials (PCMs) exploi s especially la en
hea [
7
]. PCM can be packaged in specialised con aine s (panels, ubes, and plas ic bags), o i can be
con ained in o dina y building elemen s (ceiling and wallboa ds), o encapsula ed as sel -con ained
elemen s [8].
The amoun o ene gy is gi en by he en halpy di e ence du ing he phase change, acco ding o
he ollowing Equa ion (2).
∆Q=m·∆h, (2)
whe e
∆hen halpy di e ence (J·kg−1).
Figu e 1shows he p inciple o he mal ene gy s o age in he o m o la en and sensible hea in
he PCMs.
1.2. Phase Change Ma e ial
Ma e ials o be used o phase-change TES should ha e phase-change empe a u e in he p ac ical
ange o applica ion and hey mus ha e a high la en hea o usion and a high he mal conduc i i y.
PCMs should also ha e desi able en i onmen al p ope ies o dec ease he en i onmen al impac
o he sys ems du ing hei li ecycle [
9
]. Di e en ma e ials conside ed as po en ial PCMs include
hyd a ed sal s, pa a in waxes, a y acids, he eu ec ics o o ganic and non-o ganic compounds, e c.
PCMs can be di ided in o h ee main g oups—based on he empe a u e anges o e which he TES
phase-change occu s: low empe a u e (phase-change empe a u es below 15
◦
C), mid empe a u e
Appl. Sci. 2018,8, 1750 3 o 15
( he mos popula — om 15 o 90
◦
C) and high empe a u e PCMs (abo e 90
◦
C) [
10
,
11
]. In ou case,
PCMs a e classi ied as o ganic, ino ganic and eu ec ic.
Figu e 1. La en and sensible hea , empe a u e ange o he phase change [7].
O ganic PCMs include a wide selec ion o o ganic ma e ials such as a y acids, es e s, alcohols and
glycols. The p incipal ad an ages a e hei chemical and he mal s abili y, and high la en hea o usion.
They a e usually ecyclable, non-co osi e, and ha e li le o no subcooling [
1
,
12
]. Un o una ely,
hey ha e some disad an ages: lammable, non-compa ible wi h plas ic con aine s, ela i e la ge
olume change, mo e expensi e, low he mal conduc i i y, and lowe phase-change en halpy [
1
,
13
,
14
].
Ino ganic PCMs a e desc ibed as hyd a es sal s and me als. They co e a wide ange o applica ion.
The main ad an ages a e highe en halpy pe olume, highe he mal conduc i i y, non- lammable,
and lowe olume change. Howe e , hey ha e he disad an ages o phase seg ega ion, co osion,
lack o he mal s abili y and subcooling [9,12].
The eu ec ic PCMs a e a combina ion o chemical compounds o elemen s ha ha e a single
chemical composi ion and ha solidi y a a lowe empe a u e han any o he composi ion ob ained
om he same componen s [
15
]. Due o hei highe densi y and s abili y in hei liquid s a e, hey ha e
been used widely as ionic liquids in high empe a u e sensible he mal s o age sys ems ( he monuclea
ene gy, concen a ed sola he mal powe ) [16].
Theo e ically, mos ma e ials can be conside ed as PCMs. On he o he hand, only some o
hem can be used o e ec i e and p edic able ene gy s o age. Figu e 2shows some o he many
ma e ials sui able o TES. Depending on he applica ion, he PCMs should be selec ed based on hei
phase-change empe a u e, should ha e a la ge la en hea , should mel cong uen ly wi h minimum
subcooling, and should be chemically s able, inexpensi e, non oxic, and nonco osi e [15]. The mos
commonly used PCMs in buildings a e pa a in and sal hyd a es [17,18].
Figu e 2. Classes o he phase change ma e ials and hei common pa ame e s [19].
As p e iously men ioned PCMs can be inco po a ed in o building s uc u es. I con ibu e o
lowe ene gy demand by s o ing he mal ene gy in he o m o hea o cold [
20
]. Se e al con igu a ions
Appl. Sci. 2018,8, 1750 4 o 15
ha e been p oposed in he las wo decades in o de o inco po a e PCM in o cons uc ion ma e ials.
T adi ionally, as one o he bes op ion is aken applica ion o he PCM in he en elope o he oom
because o i s la ge a ea [
21
]. Some o he ecen esea ch show some imp o emen s and speci ic use
o he PCM in he buildings and also hei ad an ages and disad an ages [
22
,
23
]. The e iciency is
no dependen only on he loca ion o he PCM, bu also on hei speci ic pa ame e s, such as mel ing
empe a u e ange. Fo example, one o he esea ch shows ha he highes alue o ene gy exi ing
om he indoo en i onmen is ensu ed by PCM wi h a mel ing empe a u e equal o 20 ◦C [24].
In eg a ion o he PCMs in o he building’s ene gy sys em can inc ease e iciency o he sys ems.
These ac i e sys ems use o he ai low as o ced con ec ion o inc ease amoun o ene gy ob ained
om s o age ma e ials [
25
]. In common applica ions, PCMs se e as a ese oi o excess he mal
ene gy o u u e u ilisa ion. One o he expe imen al ene gy sys ems wi h in eg a ed PCMs and
combina ion wi h enewable ene gy sou ces is p esen ed in his a icle.
1.3. The moelec ic Cooling Sys em
The moelec ic coole s (TEC) a e solid-s a e hea pumps based on he Pel ie e ec . I enables
con e ing elec ical ene gy in o a empe a u e g adien . In comme cial ypes, TECs a e composed o
many o n- ype and p- ype semiconduc o junc ions. When a di ec cu en powe sou ce is connec ed,
he elec ical cu en lows om he n- ype elemen o he p- ype elemen , and he moelec ic cooling
e ec occu s. When he elec ons pass om a lowe ene gy le el elemen (p- ype) o a high ene gy
le el elemen (n- ype) he empe a u e o he cold junc ion dec eases. A he same ime, he elec ons
ca y he abso bed hea o he ho junc ion. This hea is ans e ed o he hea sink, while he elec ons
e u n o a lowe ene gy le el in he p- ype semiconduc o ( he Pel ie e ec ) [26].
The e is also a possibili y o use he mocouples e e se. Tha means, i possible o gene a e
elec ical ene gy by he empe a u e di e ence. I he he mal g adien exis s be ween he cold and ho
junc ion, a ol age (Seebeck ol age) di ec ly p opo ional o he empe a u e di e ence is gene a ed.
TEC sys ems ha e no mechanical mo ing pa s and luids, which ans e hea om he cold side
o he ho side o he modules [
27
]. TECs ha e many ad an ages such as high eliabili y, low weigh ,
and lexibili y in in eg a ion. TEC sys ems ha e been applied o he moelec ic e ige a o s [
27
,
28
],
ca sea s [
29
,
30
], elec onic cooling de ices [
31
,
32
]. I has been also used in mili a y, ae ospace,
ins umen , and indus ial p oduc s [
33
–
36
]. One o he a eas o new esea ch o he moelec ic
echnology is applying he moelec ic modules (TEM) o domes ic space cooling. TEC sys ems can
be also powe ed by a pho o ol aic (PV) wi hou he in e e . Some o he ecen esea ches ocused
on he moelec ic coole s and gene a o s (TEC and TEG) a e de ined by he combina ion o sola
ene gy and PCMs. TEG is an al e na i e choice o con e ing o sola he mal ene gy in o elec ici y.
The echnology desc ibed in his a icle can use ene gy om PV o TEC in combina ion wi h he
PCM-based TES.
2. Me hods
The p oposed accumula ion echnology is based on he PCM DuPon Ene gain. This PCM is
g ouped in o one ac i e elemen [
37
]. The PCM uses molecula encapsula ion ha o ms a highly
du able PCM and i has a useable empe a u e ange be ween 0
◦
C and 40
◦
C. The mass o he PCM
is composed o a mix u e o polye hylene and pa a in wax. When he empe a u e o he PCM
is abo e 18
◦
C, he mass begins o mel and abso bs up o 515 kJ
·
m
−2
o hea in he empe a u e
ange om 18
◦
C o 24
◦
C. This empe a u e ange co esponds o common empe a u e condi ions
inside buildings.
In he pa ag aphs below a e desc ibed he basics o he p oposesd echnology, i s possible
ope a ion modes, used he mocouples and also pho o ol aics. O he speci ic in o ma ion abou his
echnology is desc ibed in ou p e ious a icles [38–40].
Appl. Sci. 2018,8, 1750 5 o 15
2.1. Accumula ion De ice
The accumula ion de ice (see Figu e 3) was designed and made a he Facul y o Applied In o ma ics
o TBU in Zlin (CZE—Czechia). The e we e also made all measu emen s and imp o emen s.
The moni o ed oom in which he echnology is loca ed has he dimensions 7 m
×
5 m
×
2.8 m.
The oom has wo ex e io su aces: wall wi h windows and ceiling ( oo ). The o he walls and loo s
a e adjacen o o he hea ed oom. The o al design hea loss due o ansmission h ough walls and
windows, en ila ion and in il a ion is abou 41 WK
−1
. In he summe i is impo an o know he
hea gains. In ou case, he maximum hea gains du ing he day (peak gains) om he ou side a e in
he ange o 280 o 480 W om May o Sep embe . Sola window gains a e educed by ou doo blinds.
This sys em is composed o wo PCM-based accumula ion panels wi h dimensions 1.25 m
×
0.083 m
×
2.1 m. Technology is equipped wi h a liquid hea exchange and elec ic hea ing oils
inside he panels. The p oposed echnology is design as “g een echnology”. So, i can be supplied
wi h powe by any common ene gy sou ces, including enewable ene gy sou ces and use hem o
hea ing and cooling. Mo eo e , he echnology is able o use pho o ol aic sys ems in combina ion wi h
he moelec ic cooling. This abili y is no common in he PCM de ices. So, i can be one o he bigges
di e ence and ad an age o he p oposed echnology agains commonly a ailable echnologies.
Figu e 3. Accumula ion de ice and he moelec ic assembly on he igh .
The echnology can be ope a ed in many di e en modes. Mode choice is dependen on he
equi emen s o pa icula expe imen s. I can wo k as a passi e o ac i e sys em. In he s anda d
passi e mode, he echnology uses he common accumula ion o he hea o cold by PCM. This mode
can dampen peaks in indoo empe a u e and keep i s able du ing he day and nigh . The echnology
in ac i e mode is capable o in luencing he indoo empe a u e by eleasing accumula ed hea o
o lowe i by using ex e nal cooling. Indi idual ac i e modes o ope a ing a e: disposing o he
accumula ed hea o hea ing up he cooled down panels; hea ing by elec ic hea ing oils o by ho
wa e ; cooling by he cold wa e o by he moelec ic coole s.
2.2. The moelec ic Coole s
As p e iously men ioned, he echnology is equipped wi h six he moelec ic assemblies o he
ype L.L.-210-24-00-00, see Figu e 4. These he moelec ic coole s o e liquid- o-liquid hea ans e .
TEC assemblies can be powe ed by he pho o ol aics o om he powe g id AC 230 V [41].

Appl. Sci. 2018,8, 1750 6 o 15
Figu e 4. TEC assembly ype L.L.-210-24-00-00.
Basic speci ica ions o he TEC modules:
- Inpu powe : 194 W,
- Cooling powe : 208 W,
- Inpu ol age/cu en : 24 V/8.1 A DC.
Fo de e mining he numbe o TEC i was necessa y o speci y he cooling capaci y o he
echnology. The a e age speci ic hea capaci y o he he mal panel is abou 11 kJ
·
kg
−1
K
−1
(16 o
27 ◦C) and i s weigh is abou 129 kg.
The cooling o he accumula ion panels akes es . 8 h. Du ing his ime, he accumula ion de ice
abso bed abou 15.6 MJ o he cold, mo e p ecisely, his amoun o hea is emo ed om he PCM.
So, he o e all pe o mance o he he mocouples mus each abou 0.55 kW. I he he mocouples
ha e 50% e iciency he equi ed (inpu ) powe o he he mocouples is abou 1.1 kW. This means i is
necessa y o use six he moelec ic assemblies o ype L.L.-210-24-00-00.
2.3. Pho o ol aic Sys em
The PV sys em is ins alled o supply he echnology and he mocouples wi h elec ic powe .
The ac i e a ea o he PV panels is 11.25 m
2
. Du ing he summe , sola adia ion ecie ed by he
pho o ol aic panels a e ages a in ensi y o 750 W m
−2
. Real ene gy e iciency o he PV was se a
10.5%. This alue was esul o measu emen in one o ou p e ious esea ches ocused on e i ica ion
o he pho o ol aic panels e ec i eness o hei economic e u n [
42
,
43
]. The eal a e age powe ou pu
is a li le bi lowe han calcula ed and measu ed consump ion o he whole echnology. Howe e ,
he pho o ol aics can p oduce mo e elec ic powe du ing a sunny day han he he moelec ic
assemblies a e capable o consuming.
3. Resul s and Discussion
Measu emen s o hea ing o PCMs ha e al eady come unde examina ion many imes.
Ou measu emen s and esul s o hea ing he p oposed echnology a e shown in ou p e ious
a icles
[38–40]
. The e o e, he c ucial objec i e o his a icle was o de e mine he beha iou o
PCM in empe a u e ange speci ic o cooling. Fo his pu pose, speci ic hea capaci y is pa ame e o
g ea impo ance. The alue o PCM used is a ound 6.8 kJ
·
kg
−1
K
−1
o empe a u es anging om
10 ◦C o 21 ◦C. The cooling powe is abou 400 W a empe a u e di e ence 12 ◦C.
The isk o condensa ion o wa e apou is he mos impo an ac o limi ing he use o cooling
de ices. To p e en his om happening, ensu ing ha he empe a u e o hei su ace is a leas 1 K
abo e he dew poin o he ambien ai is c ucial. Fo his pu pose, he echnology is able o moni o
he alue o he ambien empe a u e, humidi y and dew poin empe a u e. Technology is se o keep
he empe a u e o he he mal panels as low as possible bu s ill abo e he dew poin . Simul aneously,
echnology is able o compa ed ene gy gained om he PV and consumed by TEC modules (o HP)—in
case o low ene gy gains a e u ning o some TEC. O cou se, his au oma ic con ol mode can be
by-passed and he echnology can be ope a ed manually wi hou all es ic ion.
Appl. Sci. 2018,8, 1750 7 o 15
The hea ing and cooling pe o mance o he accumula ion de ice is also impo an . Fo his
pu pose, i is impo an o know he speci ic powe , which is gi en by he alue o he hea ans e
coe icien and he ac i e a ea. The a e age hea ans e coe icien is abou 6.4 Wm
−2
K
−1
and he
ac i e a ea is 5.2 m
2
. So, he speci ic hea ing/cooling powe is a ound 33.2 WK
−1
. I is, he e o e,
clea ha he cooling powe is dependen on he empe a u e di e ence be ween he su ace o he
panel and he ambien empe a u e. The highe empe a u e di e ence means highe he powe .
As p e iously men ioned, he used PCM has a empe a u e ange o phase change be ween 18
◦
C and
22
◦
C. When ac i e cooling is on, he sensible hea is emo ing as i s (abo e 22
◦
C), hen he phase
change occu s (be ween 22 ◦C and 18 ◦C) and hen he sensible hea is emo ing again (unde 18 ◦C).
The su ace o he panels can be cooled o he dew poin , bu he mos amoun o ene gy is able
o accumula e du ing he phase change. I he panel empe a u e is a ound 18
◦
C and he ambien
ai empe a u e is 25
◦
C, he cooling powe is app oxima ely 230 W. Fo example, a a empe a u e
di e ence o 15 ◦C, he cooling powe is abou 500 W.
As p e iously men ioned, he p oposed echnology is designed o be able o use he powe
p oduced by he PV. Ene gy p oduc ion co e s he consump ion o TEC modules wi h an a e age
cooling ou pu o abou 550 W. This powe is highe han he a e age cooling powe o he accumula ion
panel. Howe e , TEC modules lowe he la en hea o he PCM panel, i.e., he su ace empe a u e
does no change much, bu accumula ion panel is able o accumula e much mo e ene gy o la e
u ilisa ion. I he phase change limi alue is eached, he su ace empe a u e o he panel s a s o
dec ease apidly. The lowe empe a u e inc eases cooling ou pu , bu when he echnology is u ned
o , he empe a u e e u ns qui e as back o he phase change ange.
Du ing designing and ini ial measu emen s was disco e ed a echnical p oblem wi h o e hea ing
in cooling mode. This is desc ibed in he ollowing subsec ion. A e his, he e a e p esen ed esul s o
measu emen s wi h sol ed he p oblem ou .
3.1. Technical P oblem
As we al eady know, hea ing can be p o ided by he elec ic hea ing oils inside he panels o
by hea ing he panels by ho wa e om he ho wa e ank—hea ing by he hea pump o an elec ic
boile . The echnology has been es ed and measu ed in all hea ing modes. These measu emen s we e
success ul and he echnology was e ec i e wi hou ob ious p oblems. A e ha , es measu emen s
we e pe o med in cooling mode. As men ioned ea lie , cooling can be done by he hea pump o by
he moelec ic modules. The cooling mode wi h he hea pump was made and measu ed wi hou
any p oblems.
The e we e some di icul ies in measu ing o he he moelec ic cooling. Abo e all, cooling is
ine ec i e. Ins ead o dec easing he indoo empe a u e, i was inc easing. Measu emen o he
o iginal design o he echnology and he he moelec ic cooling mode is shown in Figu e 5below.
As can be seen, e en when he oom was cooling by he echnology, he empe a u e was g owing.
The empe a u e go o s a g owing up e y as when he cooling by TEC was u ned on. The indoo
empe a u e was abou 27.2
◦
C a he beginning o he measu emen . A e ac i e cooling by TEC,
i eached up o 30.8
◦
C. The esul was: he echnology ans e ed mo e hea o he oom han
i emo ed.
A e some ime, i has been ound ou why his p oblem occu s. A clea indica o was he
he mog aphic diagnos ics o he accumula ion de ice and all pa s o he he moelec ic modules wi h
coole s. In he he mog aphic images below, see Figu e 6, i can be seen all six he moelec ic assemblies
and hei empe a u es. The image cap u es he s a e o he de ice wi h ac i e he moelec ic cooling.
The lowes empe a u e on he su ace o he ho side is abou 20
◦
C and he highes empe a u e is
abou 45
◦
C. This g owing up he empe a u e is caused by connec ion o he liquid coole s in se ies.
In his place, i can be said, i is also a li le mis ake o design. Maybe, i could be be e o use he
pa allel connec ion. On he o he hand, i is possible o ge lowe ou ake empe a u e o chilled wa e .
Appl. Sci. 2018,8, 1750 8 o 15
Figu e 5. Technical issue wi h o e hea ing.
Figu e 6. Technical issue— he mog aphic diagnos ic.
In igu es below, see Figu e 7, i is possible o see de ails and empe a u es o bo h sides o he
coldes ( i s in he ow) and ho es assembly (las in he ow).
Figu e 7. Technical issue— he mog aphic diagnos ic—de ails.
The p oblem wi h he o e hea ing came om he was e hea o he TEC modules.
The he moelec ic modules a e i ed wi h he liquid hea exchange s on bo h sides. These a e
o he ex ac ion o cold and was e hea . The su ace o he hea exchange (coole ) on he wa m side
is e y high. The e o e, he was e hea is adia ed o he su oundings om he su ace o he coole .
The p oblem can be sol ed by addi ional insula ion o TEC modules and ho -wa e pipelines.
The p oblem has been sol ed by sepa a ing he space wi h he mocouples om he moni o ed
space. A ound he he moelec ic sys em, i was enough o build addi ional insula ion o keep he hea
in he enclosed space. Howe e , he e is s ill a ees anding cold wa e ank o abso bing he was e
hea om he he moelec ic modules. On he o he hand, he wa e ank is addi ionally cooled by
he hea pump a a minimum empe a u e o 10
◦
C. The e o e, i was no necessa y o sepa a e he
Appl. Sci. 2018,8, 1750 9 o 15
cold wa e ank om he moni o ed space. So, he inal imp o emen was addi ional ho wa e pipes
insula ion. All o he ollowing measu emen s in his a icle we e pe o med wi h his adjus men .
3.2. Measu emen
In he ollowing pa ag aphs, he e a e p esen ed measu emen s and esul s o he echnology in
di e en cooling modes.
The i s measu emen is ocused on common passi e mode— he mos common use o he PCM.
In his mode, he PCM-based panels educed he empe a u e luc ua ion and also s abilised he indoo
empe a u e du ing passage o a ew days o wa m wea he . An example o he sys em’s beha iou
can be seen in Figu e 8. This passi e mode managed o s abilise he indoo empe a u e be ween
23.2 ◦C and 24.0 ◦C when he ou doo empe a u e oscilla ed be ween 5.3 ◦C and 22.7 ◦C.
Figu e 8. Passi e mode.
Ano he expe imen s ocus is he ac i e cooling mode. The cooling cycle o he hea pump was
used in his measu emen . Resul s a e shown in Figu e 9.
Figu e 9. Ac i e cooling—hea pump.
E e y measu emen is made o wo cooling cycles. One cycle las ed wo days. Ac i e cooling was
u ned on du ing he i s day. Du ing he nex day, he panels we e le o jus accumula e hea om
he oom. The cycle was hen epea ed.
Du ing he i s cooling cycle, he ime i ook o cool down o he su ace empe a u es om
21.4
◦
C o 17.9
◦
C o he unmodi ied su ace and om 22.6
◦
C o 20.0
◦
C o he modi ied su ace