P oceedings 2018, 2, 1472; doi:10.3390/p oceedings2231472 www.mdpi.com/jou nal/p oceedings
P oceedings
Ne Ze o Ene gy o Indus ial and Comme cial
Mic og ids: App oaches and Challenges †
Filipe Bandei as 1, Má io Gomes 2,*, Paulo Coelho 2 and José Fe nandes 1
1 Ins i u o Poli écnico de Toma (IPT), 2300-313 Toma , Po ugal; [email p o ec ed] (F.B.);
[email p o ec ed] (J.F.)
2 Ci2—Sma Ci ies Resea ch Cen e —IPT, 2300-313 Toma , Po ugal; [email p o ec ed]
* Co espondence: [email p o ec ed]
† P esen ed a he 2nd In e na ional Resea ch Con e ence on Sus ainable Ene gy, Enginee ing, Ma e ials and
En i onmen (IRCSEEME), Mie es, Spain, 25–27 July 2018.
Published: 2 No embe 2018
Abs ac : This pape add esses he concep o ne ze o ene gy and ne me e ing in e icien buildings
in o de o assis in he s udy and de elopmen o u u e mic og ids o buildings wi h annual ze o
ene gy consump ion. The e a e se e al de ini ions o ze o ene gy buildings a ailable in he
li e a u e wi h a dis inc se o p ojec goals and in e es s, bu his wo k is ocused on he de ini ion
ha accoun s o ene gy losses by con e ing each ene gy ype o sou ce ene gy. Finally, a case
s udy is p esen ed o e alua e whe he ou dis inc all-elec ic buildings can achie e annual ze o
ene gy by deploying on-si e enewable sou ces wi hin hei si e bounda y.
Keywo ds: ne ze o ene gy; ne me e ing; enewable ene gy; e icien buildings; mic og ids
1. In oduc ion
The building sec o is a majo con ibu o o he global ene gy consump ion and ca bon
emissions [1]. Minimizing he ene gy consump ion and ca bon oo p in o indus ial, comme cial
and esiden ial buildings has become essen ial o mee en i onmen al aims and educe he use o
ossil uels o powe gene a ion. Needless o say, his can be achie ed h ough ene gy e iciency and
on-si e enewable sou ces o a oid impo ed ene gy om con en ional ene gy sou ces. The
in eg a ion o mic og ids (MG) also plays an impo an ole in he building sec o and cons i u es a
g ea oppo uni y owa ds achie ing ze o ene gy in e icien buildings. Besides being an impo an
asse o help mi iga e he en i onmen al impac om he use o ossil uels, MGs also signi ican ly
inc ease he eliabili y and quali y o he powe supplied o he loads wi hou dis u bances and
in e up ions. Di e en app oaches o ne ze o ene gy ha e been desc ibed in he li e a u e.
Howe e , a common unde s anding o ze o ene gy buildings (ZEB) is s ill lacking [2].
2. Ze o ene gy Buildings
Acco ding o [3], a ZEB is an ene gy e icien building whe e, on a sou ce ene gy basis, he ac ual
annual deli e ed ene gy is less han o equal o he on-si e enewable expo ed ene gy. In o he
wo ds, a ZEB aims o educe he use o non- enewable ene gy in he building sec o by implemen ing
ene gy e iciency measu es and p oducing enough enewable ene gy o mee o exceed i s annual
ene gy consump ion. The si e bounda y can be la ge han he building oo p in and i is he only
a ea a ailable o deploy enewable ene gy sou ces (RES) o on-si e ene gy p oduc ion [4]. The e a e
se e al de ini ions o ne ZEBs in he li e a u e ha a e s ongly dependen on he p ojec goals.
These de ini ions ake in o accoun di e en in e es s and goals es ablished by he building owne s
such as he amoun o ene gy accoun ed o a he sou ce o a he si e, as well as ene gy cos s and
P oceedings 2018, 2, 1472 2 o 5
en i onmen al conce ns associa ed wi h he use o ossil uels. Based on hese in e es s, a building
can be de ined as si e ZEB, sou ce ZEB, cos ZEB and emissions ZEB [4]. Each app oach o de ine
ZEBs is summa ized in Table 1. MGs p o ide he abili y o sa ely in eg a e RES and dis ibu ed
gene a ion (DG) uni s in o he building sec o , enabling con ol and coo dina ion o he a ailable
esou ces, and hus allowing building owne s o co ec ly manage hei ene gy consump ion and
inc ease o e all building e iciency. This can be pa icula ly impo an in cos ZEBs, since MGs can
also con ibu e o a signi ican educ ion in ene gy cos s.
Table 1. De ini ion app oaches o ZEBs.
Easie o Implemen Easie o Achie e Equa es Fuel Types Con e sion Fac o s
Si e ZEB 1 ✓ ✗ ✗ ✗
Sou ce ZEB 2 ✗ ✓ ✓ ✓
Cos ZEB 3 ✓ ✗ ✓ ✗
Emission ZEB 4 ✗ ✓ ✓ ✓
1 P oduces a leas as much annual ene gy as i uses, when accoun ed o a he si e. 2. P oduces a
leas as much annual ene gy as i uses, when accoun ed o a he sou ce. 3. Cos paid o he expo ed
annual ene gy is a leas equal o he cos paid o he impo ed ene gy. 4. P oduces a leas as much
annual ene gy om emission- ee enewable sou ces as i uses om o he sou ces.
3. Ne Me e ing
Ne me e ing is a billing sys em ha consis s o a bi-di ec ional me e , enabling cus ome s o be
c edi ed o he excess elec ici y hey eed in o he u ili y g id [5]. This allows he cus ome o ake
ad an age o he c edi s gained and impo elec ici y om he u ili y g id du ing pe iods when local
gene a ion is a a minimum [6]. Ne me e ing policies a y by egion and coun y, which may deno e
how much he c edi s a e wo h. Cos ZEBs equi e a ne me e ing ag eemen ha allows he
cus ome s o be c edi ed a a oided gene a ion a es. E en hough MGs a e well sui ed o ne
me e ing, hey a e o en excluded om mos policies because only a single cus ome is eligible o
ne me e ing and MGs usually in ol e mul iple cus ome s [7]. Howe e in he USA, Pennsyl ania
allows ne me e ing in enewable ins alla ions up o 5 MW o MGs and Connec icu applies i ual
ne me e ing ha allows each municipal cus ome o hos up o 5 non-municipal accoun s in c i ical
acili ies connec ed o a MG. Vi ual ne me e ing is a sligh ly di e en a ia ion in which he excess
elec ici y c edi s a e applied o he u ili y accoun , allowing gene a ion in one loca ion o o se
elec ici y cos s a ano he loca ion [8]. This o e comes p oblems ega ding DG sys ems in buildings
wi h mul iple occupan s [9]. Since MGs can also in eg a e non- enewable sou ces, ne me e ing is
only applied in MGs con aining exclusi ely RES and clean gene a o s.
4. Ene gy Balance
The ene gy balance is de e mined om he balance be ween deli e ed and expo ed on-si e
enewable ene gy o be ween load and gene a ion. The demand is he sum o all deli e ed ene gy o
he building and he supply is he sum o all expo ed ene gy, bo h can be de e mined by summing
each ene gy ype mul iplied by he espec i e sou ce ene gy con e sion ac o . This akes in o
accoun he ene gy losses since he ex ac ion o p ima y uels. Buildings can be de ined as ZEB i
hei annual ene gy balance is less han o equal o ze o ( ≤0) [3], gi en by (1):
 =
 −
 =∑, ×
,

󰆄
󰆈
󰆈
󰆈
󰆈
󰆅
󰆈
󰆈
󰆈
󰆈
󰆆


−∑, ×
,

󰆄
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

, (1)
whe e , and , a e he deli e ed ene gy and expo ed on-si e enewable ene gy o an
ene gy ype , espec i ely. And , and , a e he sou ce ene gy con e sion ac o o he
deli e ed and expo ed ene gy ype , espec i ely.
P oceedings 2018, 2, 1472 3 o 5
5. Case S udy
This sec ion p esen s a case s udy o ou en e p ises o e alua e whe he hese all-elec ic
indus ial and comme cial buildings can achie e annual ze o ene gy by deploying on-si e enewable
sou ces wi hin he si e bounda y. The en e p ises unde s udy include a lou mill, a qua y, an
ab asi es p oduc ion plan and a la ge hype ma ke . In o de o e alua e each building, his s udy
uses an op imiza ion algo i hm o de e mine he numbe o pho o ol aic (PV) panels and wind
u bines (WT) necessa y o achie e ze o ene gy and a he same ime minimize he implemen a ion
cos o hese ene gy sou ces. To his end, he algo i hm was de eloped using he unc ion “linp og”
in Ma lab which allows inding he op imal solu ion o a speci ic p oblem de ined by inequali y
cons ain s, equali y cons ain s and bounda ies. The objec i e unc ion o his p oblem is gi en by
(2) in Table A1 in Appendix A. The algo i hm is o ced o p io i ize he lowe cos o PV panels and
WTs, hus a oiding powe impo ed om he g id which is associa ed o a highe cos . This unc ion
is subjec ed o he inequali y cons ain s gi en by (3) and limi ed o uppe and down bounda ies
gi en by (4) in Table A1. Finally, he equali y cons ain is gi en by he ze o ene gy balance o mula
(5) also lis ed in Table A1. This allows he algo i hm o de e mine he numbe o PV panels and WTs
acco ding o he ze o ene gy balance, in which supply equals demand. The algo i hm was used o
each building wi h he loca ion da a and he echnical speci ica ions o PV panels and WTs. The
esul s in Table A1 show ha achie ing ze o ene gy in all-elec ic indus ial and comme cial
buildings is no an easy ask, especially in buildings wi h g ea powe consump ion and no wide
open a eas. Only he ab asi es manu ac u ing plan and he qua y a e able o achie e ze o ene gy,
as shown in Table A1. The annual on-si e gene a ion in hese wo en e p ises exceeds he annual
consump ion. In any case, he numbe o uni s could be signi ican ly educed by dec easing powe
consump ion, implemen ing less con en ional PV panels o by including banks o ba e ies o s o e
he excess gene a ed elec ici y. Adop ing ene gy e iciency measu es and conside ing ne me e ing
can be essen ial o achie e ne ze o ene gy. The impo ance o ne me e ing e lec s in he abili y o
each cus ome o s o e hei excess gene a ed elec ici y in he g id, so i can be used du ing a mon h
o poo sola adia ion o weak wind. This is a ou able, since i is no economically iable o s o e
elec ici y o long ime pe iods and impo an when in eg a ing non-dispa chable ene gy sou ces.
6. Conclusions
This pape b ie ly add essed he concep o ze o ene gy in buildings, ocusing on he mos
common de ini ion app oach a ailable o ZEBs. In addi ion, i also add essed he impo ance o ne
me e ing s uc u es in ZEBs and hei possible in eg a ion in o MG sys ems. The s udy ca ied ou in
his pape add essed ou dis inc en e p ises and hei abili y o achie e he s a us o ZEB. An
algo i hm was de eloped in Ma lab o e alua e whe he hese en e p ises could each annual ze o
ene gy. As expec ed, he esul s concluded ha achie ing ze o ene gy in indus ial and comme cial
buildings is no an easy ask and may no be possible wi hou implemen ing ene gy e iciency o any
means o s o ing excess ene gy gene a ed om on-si e enewable sou ces. Ne me e ing is sugges ed
o help buildings achie e annual ze o ene gy wi hou in es ing in expensi e ene gy s o age sys ems.
The subjec add essed in his pape is in despe a e need o s anda diza ion and common
unde s anding o i s concep . Mo e e o s and de elopmen s should be made owa ds he
en i onmen al impac o ene gy in ensi e buildings and enhancemen o u u e MGs.
Au ho Con ibu ions: This pape was a collabo a i e e o among all au ho s: F.B. and M.G. concei ed and
designed he ne ze o ene gy op imiza ion model; F.B. pe o med he simula ions; M.G., P.C. and J.F. analyzed
he da a; All he au ho s pa icipa ed in he discussion o he esul s; F.B. w o e he pape and he es o he
au ho s e iewed i .
Acknowledgmen s: This wo k was pa ially suppo ed by he Po uguese Founda ion o Science and
Technology (FCT) and by PIDDAC, unde he esea ch p ojec INDuGRID, ERANETLAC/0006/2014.
Con lic s o In e es : The au ho s decla e no con lic o in e es . The ounding sponso 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 , and in he
decision o publish he esul s.
P oceedings 2018, 2, 1472 4 o 5
Appendix A
Table A1. Case s udy o mula ion and esul s o achie ing ze o ene gy in all-elec ic buildings.
P oblem Fo mula ion
Objec i e unc ion:   ×
 +
 ×
 +
 × (2)
Subjec ed o:  ×
 ≥0
(3)
 ×
 ≤

(4) 


−
 ×
 +
 ×
 +

󰆄
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󰆅
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
=0 (5)
 ×
 ≥0  ×
 ≤

 ≥0  ≤

, numbe o PV and WT/, cos o PV and WT/ high cos alue/, powe gene a ed om PV and
WT/, a ea occupied by PV and WT/, o al a ea a ailable o PV and WT/, powe impo ed and
consumed
Demand
(kWh/yea )
A ea o
PV/WT (m2)
Numbe o
PV/WT Uni s
Es ima ed Cos
o PV/WT (€)
Gene a ed Powe
(kWh/yea )
Impo ed
Powe
(kWh/yea )
Flou mill 1,351,603 3200 */1125 794.57/3.58 516,472/30,044 918,141 456,083
Qua y 245,516 900 */1500 223.47/4.77 145,258/40,059 301,893 25,589
Ab asi es 891,592 3360 */1200 * 834.30/3.82 542,296/32,047 964,740 140,048
Hype ma ke 2,694,503
4925 **/6500
*
1222.89/20.69 794,883/173,590 1,589,001 1,105,502
* Roo op ins alla ion/** Pa king lo ins alla ion
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P oceedings 2018, 2, 1472 5 o 5
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