Economic Performance of Solar Panel Installations with Heat Gain Reduction Benefit

Transcription

1 Ecoomic Performace of Solar Pael Istallatios with Heat Gai Reductio Beefit Sappiadaa Akampho* Faculty of Egieerig, Thammasat Uiversity, Pathumthai 12120, Thailad * Phoe: ext 3258, Fax Abstract The feasibility of solar pael wall ad roof istallatios i buildig is ivestigated. Without cosiderig reduced heat gai beefit, it has bee widely show that solar paels remai prohibitively expesive. With the beefit, however, certai buildig cofiguratios become attractive cadidates. This research explores the combiatios of buildig shapes ad pael locatios leadig to ecoomically viable istallatios usig a buildig eergy simulatio program called equest. Employig Bagkok weather data, the results show that roof istallatios have the highest rate of retur for tall ad slim buildigs, while west ad south wall istallatios gives the highest retur for short ad wide buildigs. Keywords: Buildig-itegrated photovoltaics, ecoomic performace, heat gai reductio 1 Itroductio Photovoltaic (PV) has become a importat reewable eergy source. I Thailad, however, its cost effectiveess remais doubtful due to solar pael s high maufacturig cost compared to iexpesive albeit evirometally ufriedly grid electricity. Furthermore, govermet tax icetive ad subsidy programs do ot yet offset the high ivestmet costs of paels ad iverters. These cotribute to the limited use of solar paels i Thailad despite the abudace of available solar power. The partial reaso for the curretly assumed ifeasibility of solar pael is that ecoomic performace evaluatio of solar pael istallatios cosists oly of two parts: the ivestmet ad the profit from geerated electricity [1-3]. I fact, there is a additioal beefit to solar pael istallatio o a buildig the istallatio would shield the buildig from solar irradiace, reducig the buildig heat gai ad, cosequetly, the required space coolig eergy [4, 5]. The reduced heat gai ad resultat coolig load of PV-itegrated walls have bee studied extesively, i which the heat gai through the wall is reduced by 30%-50% depedig

2 o the solar irradiace i the area [6, 7]. However, this beefit has ot bee icorporated ito curret solar pael feasibility aalyses, which would likely improve the ecoomic performace of solar pael sigificatly. By cosiderig profit both from the geerated electricity ad reduced coolig load, a more thorough ad justified feasibility aalysis of ay istallatio is possible. The proposed aalysis method will subsequetly be coducted to determie buildig characteristics leadig to ecoomically viable istallatios. 2 Assumptios ad Methodology The objective of this work is to show the sigificace of reduced heat gai to the ecoomic performace of solar pael istallatio ad also to determie buildig characteristics that lead to the most viable solar pael istallatio. I order to do so, baselie assumptios regardig the buildigs, solar pael istallatios, ad ecoomic performace evaluatio must be addressed. 2.1 Buildig assumptio Three buildig base sizes ad three heights are cosidered. Small S, medium M, ad large L bases are 15 m x 15 m, 30 m x 30 m, ad 60 m x 60 m, respectively. The three heights are 2-floor, 5-floor, ad 8-floor respectively. Each floor is 4 m high (floor-tofloor). The buildigs from this poit o will be referred to by their floor umbers ad base sizes such as 8M or 5S. Figure 1: Modeled medium 2-floor buildig (2M) The buildig walls ad roof are modeled as 15 cm-thick cocrete. The widow-to-wall ratio is 15%. Each floor is 0.6 m thick. 2.2 Solar pael istallatio assumptio The modeled characteristics ad costs of solar paels ad iverters are listed i Table Table 1 ad Table 2. The parameters are used to model the amout of electricity geerated from solar pael istallatios. Table 1: Modeled solar pael characteristics ad cost based o Samsug LPC250S pael Maximum Power 250 W Maximum Power Voltage 50.5 V Maximum Power Curret 5.65 A Ope Circuit Voltage (V oc ) 62 V Short Circuit Curret (I sc ) 6.2 A Temperature Coefficiet of V oc Temperature Coefficiet of I sc Dimesio (LxWxH) V/ C 3.44 ma/ C 1.9x1.3x0.05 m Uit Cost baht

3 Table 2: Modeled iverter characteristics ad cost based o Froius IG Plus-5.0 Capacity 5 kw Operatig DC V Voltage Uit Cost baht The solar paels modeled here are fixed ad face outward ormal to the buildig surface o which they are istalled, ad they completely cover the surface, leavig oly widow area exposed to the su. The paels are assumed to be directly coected to a power grid, elimiatig the eed for batteries. The buildigs are assumed to have o shades from other buildigs or surroudig trees. The solar paels ad iverters are assumed to have lifetime of 20 years. Figure 2: Illustratio of roof PV istallatio o 2M buildig The umber of solar paels eeded ( p ) is simply calculated from p A bs A A where A bs is the buildig surface area, A w is the widow area, ad A p is the pael area. The umber of paels coected i series ( series ) is calculated by p w series Wi W pael where W i is the power capacity of the iverter ad W p is the peak wattage of the pael. Fially, the umber of paels coected i parallel ( parallel ) is simply p parallel. series 2.3 Ecoomic performace evaluatio I this work, ecoomic performace of a pael istallatio is measured by its the iteral rate of retur (IRR), which is the iterest rate at which the et preset value of the ivestmet is equal to that of the beefits. I this work, the ivestmet cosists of pael cost ad iverter cost, while the beefit is the sale of electricity geerated from the paels. As previously metioed, however, a frequetly overlooked beefit is the reduced heat gai through wall or roof of the buildig o which it is istalled. The reduced heat gai traslates ito smaller space coolig load ad, cosequetly, electricity cost savig. The IRR i each case is evaluated based o the same buildig but without the PV istallatio. For example, the IRR of 2S East is calculated based o the electricity cost of 2S buildig without PV. To evaluate the electricity cost savig ad icome from solar electricity, the coolig load reductio ad electricity geerated must be determied, a task which will be calculated by a eergy simulatio program called equest. The program, developed by

4 20-year IRR AEC27 US Departmet of Eergy, has bee used i may reviewed literature to determie eergy requiremet i a buildig [8-11], takig ito accout solar irradiace, solar agle, weather data, ad heat trasfer coefficiets of buildig materials. Furthermore, it ca determie the electricity geerated from PV istallatio usig solar pael characteristics, azimuth, ad tilt agles. The reduced electricity required for coolig is traslated ito savig usig a electrical tariff equatio. The tariff is made up of two parts, the required peak power W p ad the total electrical eergy cosumptio E, as show i Equatio ElecCost k W k E 1 p 2 where k 1 = 210 baht per kw per moth ad k 2 = baht per kwh. The icome from electricity geerated is calculated from the power ad electrical eergy geerated (E G ). ElecSale k E 3 G where k 3 = 3 baht per kwh. The tariff ad icome equatios are based o actual Metropolita Electricity Authority rate for office buildigs. Oce the aual cash flow is calculated, the IRR of each case is determied. The combiatio of buildig characteristic leadig to the maximum IRR is the most viable solar pael istallatio. 3 Results ad Discussios Usig the methodology detailed earlier, IRRs of solar pael istallatios with ad without heat gai reductio will be compared. The the IRR of various istallatios with the heat reductio will be compared to determie the characteristics of buildig ad pael orietatio leadig to the most viable istallatio. 8% 6% 4% 2% 0% -2% -4% -6% -8% Roof West South East North 2S 2M 2L 5S 5M 5L 10S 10M 10L Buildig Type Fig. 1: 20-year IRR of various solar pael istallatios without heat gai reductio beefit Fig. 1 shows that for most istallatios except roof, the 20-year IRRs are egative due to high solar pael ad iverter costs ad relatively low icome from electricity sale. Without heat gai reductio cosideratio, most istallatios are ot ecoomically viable or provide too small a retur to be attractive. The maximum IRR is 2.1% for 10L roof istallatio

5 20-year IRR Icrease 20-year IRR AEC27 8% 6% 4% 2% 0% -2% -4% -6% -8% Roof West South East North 2S 2M 2L 5S 5M 5L 10S 10M 10L Buildig Type Fig. 2: 20-year IRR of various solar pael istallatios with heat gai reductio beefit However, oce heat gai reductio is cosidered, all solar pael istallatios see icrease i their IRRs, as show i Fig. 2. The maximum IRR is 3.5% for 10L roof istallatio, ad the miimum IRR is -3.8% for 2S orth istallatio. Although it is importat to ote that the IRRs of may other istallatios have ow become positive. 8% 7% 6% 5% 4% 3% 2% 1% 0% Roof West South East North 2S 2M 2L 5S 5M 5L 10S 10M 10L Buildig Type Fig. 3: IRR improvemets due to heat gai reductio beefit Fig. 3 shows the magitudes of IRR improvemets for various buildigs. The largest icreases are from west istallatios (10L at 6.6%), followed by east, ad south. The icreased IRRs i the west wall istallatios are the highest due both to the reduced mothly peak load ad reduced eergy cosumptio, while that i the east ad south istallatios are mostly due to reduced eergy cosumptio. Sice the peak load teds to occur i late afteroos, the west istallatio is able to prevet a majority of heat gai from solar irradiace. Fig. 3 also shows the effect of buildig shape o ecoomic performace of solar pael istallatios. For 2-floor buildigs, the roof IRR decreases with the icreasig base area. For 5- ad 10-floor buildigs, the roof IRR icreases with the base area. This is because the beefit of heat gai reductio is miimal i short buildigs to small air volume. For wall istallatios, IRRs always icrease with the base area regardless of buildig height. 4 Coclusio This work proves that the effect of heat gai reductio should ot be igored whe evaluatig ecoomic performace of a solar pael istallatio, especially i regios with high solar radiatio like Thailad, as it ca add up to 6.6% of IRR. Furthermore, the results show that roof solar pael istallatios ca be ecoomically viable i buildigs especially whe it is tall ad wide, i which roof istallatios are particular suitable because it ca geerate more salable electricity. I shorter buildigs, west istallatios are the optimal selectio due to large heat gai reductio beefit. This work also shows great promises for the future use of solar paels i Bagkok area where tall ad large office buildigs are

6 the orm. I these buildigs, the heat gai reductio beefit would be eve larger. Coupled with icreasig electricity tariff ad decreasig pael costs, the ecoomic viability of buildig-itegrated solar paels would be eve greater. 5 Refereces 1. Oliver, M. ad T. Jackso, Eergy ad ecoomic evaluatio of buildig-itegrated photovoltaics. Eergy, (4): p Faey, A.H., B.P. Dougherty, ad M.W. Davis, Measured performace of buildig itegrated photovoltaic paels. Joural of solar eergy egieerig, : p Davis, M.W., A.H. Faey, ad B.P. Dougherty, Measured versus predicted performace of buildig itegrated photovoltaics. Joural of solar eergy egieerig, : p Yag, H., et al., Grid-coected buildigitegrated photovoltaics: a Hog Kog case study. Solar eergy, (1-3): p Heso, J.W.C., CLIMATE AND LATITUDE EFFECTS FOR BIPV SHADE ELEMENTS. 6. Yag, H., J. Burett, ad J. Ji, Simple approach to coolig load compoet calculatio through PV walls. Eergy ad buildigs, (3): p Wag, Y., et al., Ifluece of a buildig's itegrated-photovoltaics o heatig ad coolig loads. Applied eergy, (9): p Crawley, D.B., et al., Cotrastig the capabilities of buildig eergy performace simulatio programs. Buildig ad Eviromet, (4): p Scheuer, C., G.A. Keoleia, ad P. Reppe, Life cycle eergy ad evirometal performace of a ew uiversity buildig: modelig challeges ad desig implicatios. Eergy ad buildigs, (10): p Yezioro, A., B. Dog, ad F. Leite, A applied artificial itelligece approach towards assessig buildig performace simulatio tools. Eergy ad buildigs, (4): p Erickso, V.L., et al. Eergy efficiet buildig eviromet cotrol strategies usig real-time occupacy measuremets ACM.