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Environmental assessments and economic performance of BAPV and BIPV systems in Shanghai
Energy and Buildings 130 (2016) 98–106
Contents lists available at ScienceDirect
Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild
Environmental assessments and economic performance of BAPV and BIPV systems in Shanghai Wenli Wang a , Yongsheng Liu a,∗ , Xinfang Wu a , Yan Xu a , Wenying Yu a , Chunjiang Zhao a , Yunbo Zhong b a b
Institute of Solar Energy, Shanghai University of Electric Power, Shanghai 200090, China School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
a r t i c l e
i n f o
Article history: Received 24 April 2016 Received in revised form 27 July 2016 Accepted 29 July 2016 Available online 29 July 2016 Keywords: Photovoltaic power system Economics Programming environments
a b s t r a c t This paper mainly analyses two systems in Shanghai. A Building Attached Photovoltaic (BAPV) system of 3 kWp and a Building Integrated Photovoltaic (BIPV) system of 10 kW. This BAPV system is the first practical application of grid-connected roof-mounted BAPV systems in China. It has great significance to the research of BAPV systems and the development of China renewable energy. The output yields, monthly performance ratio (PR), and monthly system efficiencies of the two systems of the two systems are illustrated. This paper used net present value (NPV) and the payback period (Pd ) to analyze system benefits. PV SOL is used to simulate these two systems combined with three load profiles. The simulation results including economic and performance states are illustrated in this paper. Moreover, energy payback time (EPBT) and greenhouse-gas payback time (GPBT) are used to evaluate environmental impacts. EPBT of the two systems are 4.2 years and 3.1 years, for GPBT they are 1.3 years and 0.4 years. The economic benefit of contaminating emission reduction of the two systems is also assessed to promote the development of PV industry. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The energy construction of China is quietly unreasonable, since coal-fired power plants account for more than 60% of the total power generation, solar power generation only reaches 0.06%, wind power is about 4% in year 2015. In China, energy consumption is mainly depends on coal-fired, which is the main reason for environmental pollution and greenhouse-gas, thus our air will be foul and disruptions to our climate will threaten us all. Furthermore, the most conventional energy distributes in northwest China and north China, but China’s energy consumption is mainly concentrates in southeast coast region whose economy is relative developed. In other words, there is a significant difference in the occurrence of resources and energy consumption areas in China. In order to ease the problem, more and more researchers focus on the renewable energy. As a kind of new energy, solar energy has many advantages such as pure, renewable, abundant etc. [1]. Furthermore, compared with other renewable energies, solar energy is the most abundant and inexhaustible [2–5]. To promote the development of solar
∗ Corresponding author. Tel.: +86 21 35303922; fax: +86 21 68029219. E-mail address: [email protected] (Y. Liu). http://dx.doi.org/10.1016/j.enbuild.2016.07.066 0378-7788/© 2016 Elsevier B.V. All rights reserved.
energy, several policies were proposed by Chinese government, such as the plan of solar roof of buildings. Solar energy can be used in many forms like solar heating, solar photovoltaic, solar thermal electricity, etc. [6,7]. As a new concept to use solar energy, the building photovoltaic power system has been proposed. This paper analyzed the building attached photovoltaic (BAPV) system and the building integrated photovoltaic (BIPV) system [8,9]. It’s necessary to evaluate economic benefits in the PV industry. The system uses net present value (NPV) and payback time (Pd ) to determine profitability. Several researches have been already illustrated to assess the economic benefit of PV system by using NPV and the Pd [10–12]. In its life cycle, balance of system (BOS) production, installation, and system disposal or recycling require much energy. Life cycle assessment (LCA) is perfect to evaluate the sustainability of PV system. Energy payback time (EPBT) and Greenhouse-gas payback time (GPBT) are institute ways to evaluate environment benefit. The environmental benefits of the PV systems in literatures [13–17] are all assessed by researchers. Economic and environmental benefits of the BAPV system and the BIPV system in Shanghai, China are analyzed in this paper.
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2. The model of BAPV system and BIPV system Nomenclature S Cgen Cinv Cinst Csystem Csub
The initial cost Generator cost Inverter cost Installation cost System cost The possible quantity of financial subsidy on the initial cost CO&M The cost of operation and maintenance Cins Insurance cost Egrid The annual amount of inputting electricity to the grid Ec The amount of using PV electricity per year The inflation rate g i The nominal interest rate t The t year The lifespan of PV N Ppv The PV electricity tariff The coal electricity tariff Pc Pd The payback time Qt The profit made in year t Eoutput The amount of energy generated by the PV system per year ES The energy consumption of PV modules EBOS The energy consumption of BOS components GHGPV The total GHG emission with respect to PV modules GHGBOS The total GHG emission with respect to BOS components GHGoutput The emission prevented by installing the PV system GHGrate The GHG emission rate of per unit electricity power generated by PV system
2.1. The concept of BAPV system and BIPV system As above, building photovoltaic power system consists of BAPV system and BIPV system. For the BAPV system, the PV arrays are attached to the roof through the simple supportive structures. They can be easily installed, and have a short construction period and low installation costs. But the building load is increased and the overall effects of the building would be affected. Additionally, in the building surface, BAPV also has a repeated construction problem that will lead to the waste of the building materials. For BIPV system, the PV arrays are integrated into the envelope structure of the building effectively, which becomes an indivisible part of the building. As a result, BIPV can overcome the shortcomings generated by the BAPV system [18,19]. When choosing PV systems, we should considering the advantages and disadvantages of the two models, photovoltaic technologies, architectural forms, costs and other building site situations. 2.2. The models of the two systems The BAPV system of 3 kWp is located in Minhang district, while the BIPV system of 10 kWp is located in Pudong New Area. Both the area are in Shanghai (latitude of 31◦ 12 N and longitude of 121◦ 24 E), China. Both the systems face south with an installed angles are 25◦ . Automated data monitoring systems were installed for data acquisition, including PV ambient temperature, solar radiation and electricity generated data. The weather station of both systems are located near the PV systems. The radiation measuring instrument is installed on the same surface the PV array with a setting angle of 25◦ . The temperature measuring instrument is installed nearby the PV array with good ventilation. The BAPV system is the first practical application of a gridconnected roof-mounted BAPV system in China and has great significance to the research of BAPV and the development of China renewable energy. It started to work in later December 2006. The
Fig. 1. The environment conditions of the BAPV system.
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Fig. 2. The environment of the BIPV system.
Polycrystalline silicon photovoltaic modules was installed on the roof in order to provide electricity for the building and reduce indoor heat load. The PV system is made of 22 polycrystalline silicon photovoltaic modules with a total area of 22m2 . Since there are no surrounding buildings, the PV array is covered without any shadow as shown in Fig. 1. It is beneficial for the conversion of PV array. On the standard condition, the open-circuit voltage and operating voltage of the BAPV system are DC 535 V and DC 427 V. While, the short-circuit current and the operating current of the system are DC 7.43 A and DC 7.01 A. The total installed capacity is 2992 Wp. Fig. 2 shows the photovoltaic roof structure appearance of the 10 kWp BIPV system, which adopts the monocrystalline silicon solar modules to converter radiation to electricity. The PV system forms an integrated photovoltaic roof instead of the traditional concrete pouring layer structure. This system includes PV roof array, inverters, AC protection switch devices and measuring instruments. It connects to the grid partly. The rooftop PV array includes a total number of 54 monocrystalline silicon PV modules (185 Wp per modules) and forms six string in total. Each string consists of nine pieces of modules in series. The string can be divided into three groups with each two string in parallel. The groups connect to three single-phase grid-connected inverters, whose specification is GT2.8ST. Under the standard condition, for each series group, the operating voltage and current are about DC 320 V and 5.2 A. The open-circuit voltage is between 370 V and 380 V, and the output power is from 1660 W to 1670 W. As a result, the total installed capacity is about 9.99 kWp. 2.3. Performance of the systems BIPV/BAPV systems is designed according to weather condition (temperature, humidity, solar radiation), and these data can be found in Meteonorm software and used to design PV systems. The productions and consumptions of two systems are recorded and calculated by dynamic data recorded by data acquisition system. The data of the two systems used to calculate system efficiency are based on the real one completely. An automated data monitoring systems were installed for data acquisition, including the solar radiation quantity, the generation power, the surface temperature, etc. The time interval is 5 min. We choose data of one typical year
Fig. 3. Monthly output yield and solar radiation quantity of the two systems.
to analysis the performance of these two PV systems. Fig. 3 shows the monthly output yield and solar radiation quantity. From Fig. 3, it can be found that the monthly output yield of 3 kWp system varies from 185.9 kWh in February to 357.4 kWh in August. The total output yield is 3114.3 kWh. While the monthly output yield of 10 kWp system varies from 470.3 kWh in February to 1020.4 kWh in April with a total value of 9890.7 kWh. Solar radiation quantity reaches maximum value of 134.7 kWh/m2 in July, and the minimum value is 58.6 kWh/m2 in February. The yearly total solar radiation quantity is 1181.3 kWh/m2 . The output yield and the solar radiation quantity of the two systems in winter are much smaller than that in summer. Both the parameters in June are smaller than that in May and July due to the rain. The performance ratio (PR) represents the relationship between the actual and theoretical energy outputs of the PV system. The loss may be caused by array temperature, incomplete utilization of the irradiation, and so on. We can use PR to compare different PV systems with different geographical location or rated power. We can also use PR to monitor the status of the PV power station over a long operation time. Fig. 4 shows the PR and system efficiency of the two systems. PR of 3 kWp system varies from 78.1% in December to 83.0% in July. The average PR is 80.8%. Meanwhile, the PR of 10 kWp system varies from 77.9% in April to 84.1% in October with an average value of 80.3%. Based on PR, the performance of 3 kWp
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Qt means the difference between the savings achieved in electricity bill and incurred expenses in consequence of the investment [21]. By considering the cost variation, Qt can be expressed as the following formula: Qt = Ppv Egrid + Pc Euse − (CO&M + Cins ) (1 + g)t
(7)
In the formula g represents the inflation rate. According to the above formulas, NPV of the grid-connected PV system can be expressed as the following formula:
Qt Q2 Q1 Qn + +···+ n = −S + t 2 (1 + i) (1 + i) (1 + i) (1 + i) t=1 (8) p
NPV = −S +
Fig. 4. Monthly performance ratio and system efficiency of the two systems.
system is a little better than the 10 kWp system. The average system efficiency of 3 kWp is 10.8%, while it is 11.2% of 10 kWp. System efficiency represents the performance of the overall PV array. The 10 kWp system was installed by monocrystalline PV modules, while 3 kWp system used polycrystalline silicon PV modules. The conversation efficiency of monocrystalline PV modules is larger than that of polycrystalline silicon PV modules. System efficiency in winter is much larger than that in summer. It can be attributed to high temperature in summer which can increase the surface temperature of PV modules. PR of the system can be affected by low efficiency caused by shelter of rain and dust, temperature, irradiance, power loss of inverter, cables, and transformer etc. The PR varied with seasons considerably mainly because of the temperature, irradiance, and shelter caused by rain and dust. Temperature and irradiance of PV systems are higher in summer than in winter and shelter caused by rain and dust is less in July than in December. Changing of temperature will cause decrease of output voltage, increase output current, and decrease actual efficiency as well as the output power of PV systems. Temperature is one of the important factors that affect PR of PV systems. Temperature deviate more from standard temperature in winter than in summer. That is the reason why PR varied with seasons considerably.
The payback period (Pd) means capital turnover using the following formula to calculate.
−S +
P t=1
Qj (1 + i)
t
=0
(9)
3.2. The model of the environmental assessment Through the life cycle of PV system, it consumes some energies, and generates some greenhouse gases (GHG) during power generation process. Since LCA is a technique for assessing various aspects associated with the development of a product and potential impact throughout a product’s life. So it is used to analyze the environment effects generated by the production of raw materials, the processing and purification, the manufacturing of modules and BOS components, the installation and utilization of the systems, and finally the decommissioning and disposal or recycling of the PV system [22–24]. The EPBT, Greenhouse Gas per kilowatt hour (GHGrate) and GPBT are used to value environmental benefits. 1) EPBT
3. The economic assessment of the two systems EPBT can be calculated by the following formula: 3.1. The model of the economic assessment NPV is used for financial appraisal [20], and can be expressed as follows: NPV =
p
EPBT =
ES +EBOS Eoutput
(11)
2) GHGrate (CI − CO)(1 + i)
−t
(1)
t=0
CI: cash inflows; CO: cash outflows; i: the nominal interest rate; p: the lifespan of PV (years); t: project age limit. The initial investment S for PV systems is calculated by (2): S = Cgen + Cinv + Cinst − Csub = Csystem − Csub
(2)
The cash inflows and outflows of the connected-grid system in year t can be shown as (3) and (4): CI = PPV Egrid + Pc Euse
(3)
CO = Co&M + Cins
(4)
CO&M + Cins = ˛Csystem
(1 + i)
25
i(1 + i)
−1 25
(˛ = 0.5%)
GHGrate is selected to compare the sustainability and “greenness” with different types of power generation systems. For PV power systems, the GHG emission rate can be expressed as the ratio of the total GHG emissions of PV system (including BOS) to the amount of the generated electricity during its life cycle. Equation (12) shows the calculation of the GHG emission rate in a specific PV system [25]. GHGrate =
(12)
3) GPBT
(5) GPBT is expressed as follows:
The net cash flow Qt in year t can be expressed as the following: Qt = CI − CO = Ppv Egrid + Pc Euse − (CO&M + Cins )
GHGS + GHGBOS Eout
(6)
GPBT =
GHGS + GHGBOS GHGoutput
(13)
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Table 1 The Investment of System of 3 kWp.
Table 3 The Economic Benefit of Contaminating Emission Reduction of 3 kWp.
Initial investment (USD/kW)
1872.5
The emissions
NOx
CO2
SO2
Lifespan (year) Annual output yield (kWh/kW) Discount rate PV electricity tariff (USD/kWh) Grid-connected electricity
25 1000 3% 0.1498 0–100%
Generation capacity of coal system (kg/MWh) Generation capacity of PV system (kg/kW) The amount of emission reductions (kg) The cost of pollution management (USD/kg) The environmental benefit (USD)
5 5.16 359.5 1.1984 430.82
1180 1100 85200 0.0034 293.55
14 5.85 1032.4 0.7550 779.45
Table 2 The Investment of System of 10 kWp. Initial investment (USD/kW)
1947.4
Lifespan (year) Annual output yield (kWh/kW) Discount rate PV electricity tariff (USD/kWh) Grid-connected electricity
25 1044 3% 0.1498 0–100%
4. Results of economic and environmental assessment 4.1. Result of economic assessment The investments of the two systems are shown in Tables 1 and 2. The initial investment of PV modules of the 3 kWp system is higher than that of 10 kW. The reason is that, system installation of 3 kWp is earlier than the installation of 10 kWp, when the instruments were more expensive such as PV modules, inverters, etc. The BAPV system can be easily installed, and have low installation costs as well as a fraction of framework expenses. So the overall investment of the 3 kW BAPV system is lower than the 10 kW system, because of the lower installation cost and framework expenses. Annual output power of 10 kWp is larger than that of 3 kWp, the lifespan of two systems are all 25 years. According to the latest rules in 2016, PV feed in tariff in Shanghai of PV stations will be 0.1468USD/kWh in 2016 and with downside of 0.003USD/year until year 2020. The subsidy in Shanghai is 0.063USD/kWh provided by government and 0.045USD/kWh provided by Shanghai government in the first 5 years. This paper mainly analysis small grid connected PV systems with electrical appliances. The feed in tariff of these kinds of systems is equal to desulfurization coal power plant electricity price which is 0.067USD/kWh in Shanghai. The inflation rate is set to be 2%. The NPV and payback period have significant difference according to load profiles, they will be illustrated in detail in Simulation sections. 4.2. Result of environmental assessment The energy consumptions of PV modules of the two systems are 107240 MJ and 453100 MJ, which are equal to 4662.61 MJ/m2 and 6041.33 MJ/m2 . This result has been researched by several literatures [26–30]. Energy consumptions of BOS systems are 31284 MJ and 65840 M [36]. Total energy consumptions of the systems are 138524 MJ and 518940 MJ, The ratio of energy consumptions of PV modules are 77.42% and 87.31%, while energy consumptions of BOS systems only occupy for 22.58% and 12.69% respectively. So energy consumption is mostly aroused by PV modules. The annual saved energy consumptions are 32730 MJ and 120021 MJ of the two systems. Based on formula (11), EPBT of the two systems are 4.2 years and 3.1 years. The total amount of GHGemission of BAPV system within its lifespan is 3300 kg [36]. While for the BIPV system, the total amount of GHGemission is 16376 kg. As BIPV system uses PV modules as the building roof instead of the traditional building materials, so GHGemission could be reduced by building materials by 12779 kg.
The annual reductions of GHGemission are 2520 kg and 9241 kg, both the corresponding reductions of per kWh are nearly 0.84 kg. GHGrate of the two systems are 44 g/kWh and 60 g/kWh. GHGrate of the BIPV system is higher than that of BAPV system. One possible reason is that PV modules in BIPV system are monocrystalline silicon while PV modules in BAPV system are polycrystalline silicon. Researches have been proved that GHG emission of monocrystalline silicon PV modules is larger than that of polycrystalline silicon PV modules. Based on formula (13), GPBT of the two systems are 1.3 years and 0.4 years. According the above analysis, both systems have a good environmental benefit and the BIPV system has better environmental benefits than the BAPV system. Tables 3 and 4 show the economic benefit of contaminating emission reduction of the two systems. Based on the literatures [31–35], the associated emissions of sulfur dioxide (SO2 ), nitrogen oxides (NOx), and carbon dioxide (CO2 ) of the system must be considered within its lifespan to research the advantage of PV systems by comparing the emissions of PV system with that of conventional power plants. The reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 359.5 kg, 85,200 kg and 1032.4 kg. For per kWp, the reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 119.8 kg, 28400 kg and 344.1 kg. For the BIPV system, the reduced emissions of NOx, CO2 , and SO2 are 1316.8 kg, 30,8120 kg and 3787 kg, which are equivalent to 131.7 kg/kWp, 30,812.0 kg/kWp and 378.7 kg kWp. Comparing the two systems, the reduced emissions of NOx, CO2 , and SO2 of the BAPV system for per kWp are smaller than that of the BIPV system. Meanwhile, the emissions of CO2 could be reduced by building materials by 12,779 kg. By converting the emissions reduction into economic benefit, the related environmental economic benefits of the BAPV system are 430.82 USD, 293.55 USD and 779.45 USD. They can be also expressed as 143.61 USD/kWp, 97.84 USD/kWp and 259.84 USD/kWp. The total environmental economic benefit of the BAPV system within its lifespan is 1503.83 USD, the corresponding yearly average value is 60.15 USD, for per kWp, the annual value is 20.07USD/kWp. For the BIPV system, the related environmental economic benefits are 1577.99 USD, 1105.67 USD and 2859.08 USD. They are 157.80, 110.57 and 258.91 by the unit of USD/kWp. The total environmental economic benefit of the BIPV system within its lifespan is 5542.75 USD, the corresponding yearly average value is 221.70 USD, for per kWp, the annual value is 22.17USD/kWp. So the annual environmental economic benefit is 22.17USD/kWp. It can be found that the related environmental economic benefits of the BIPV system are larger than that of the BAPV system. As a conclusion, the BIPV system has a better environmental benefit than the BAPV system. Furthermore, systems of BIPV and BAPV could reduce energy consumption and emission in building. This result is valuable for the government to promote investment in PV projects base on the data. Meanwhile, we should consider the cost of external parts, which is consist of the effects on public health (including deaths) and on the environment (the climate change is taking place since human bring). For example, GHG which is generated by human activities like population could arouse climate change [36]. The application of solar energy should
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Table 4 The Economic Benefit of Contaminating Emission Reduction of 10 kWp. The emissions
NOx
CO2 (system)
Generation capacity of coal system (kg/MWh) Generation capacity of PV system (kg/kW) The amount of emission reductions (kg) The cost of pollution management (USD/kg) The environmental benefit (USD)
5 5.82 1316.8 1.1984 1577.99
1180 1638 308120 0.0034 1061.63
CO2 (building material)
SO2
12779 0.0034 44.04
14 6.31 3787 0.7550 2859.08
be promoted not only by technologies, but also depends on politics and policy issues.
5. Simulation If we combine these two systems with certain load profile and analyze with PV SOL under current subsidy and feed in tariff, the results will be more meaningful. PV SOL is a fully functioned, practicality German PV design software. PVSOL is a software that can be used to build PV programs. Grid-connected PV systems, grid-connected PV systems with electrical appliances, grid-connected PV systems with electrical appliances and battery systems, these three kinds of PV systems can be built and simulated. Climate data depend on locations and can be obtained from Meteonorm software or created by your own climate data with import files. PV systems can be planned and designed with 3D visualization. Simple roof area, complex buildings, and open area can be used to place PV systems. Several kinds of trees, walls, and buildings nearby PV systems can also be simulated in the program building process. The most suitable inverter can be chosen by your own adjustment and cable loss can be calculated in detail using parameters set by yourself. Several types of load profiles like business load, agriculture load, industrial load, and household load are available in building the PV program. Load profiles can also be built using hourly data in every season and holiday. Initial investment, consumption and operation cost, feed in tariff, and from grid tariff can be set in the economic analysis part. System energy balance, economic analysis, and performance of the PV systems can be calculated as base results. During this simulation, the PV SOL example poly modules are selected as electricity generation section and equipped with inventers. The cable is set in detail, and the total loss is 0.12%. The feed in tariffs are present tariffs mentioned above. Three kinds of load profiles are located in this paper, namely residential load, commercial
Fig. 5. Three load profiles.
load, and industrial load. The load profile of one day can be seen in Fig. 5 [37]. The annual energy consumption is 5000 kWh. The results of simulation with PV SOL can be seen in Figs. 6–12. Figs. 7–12 is production forecast with consumption of 3 kW and 10 kW. The consumption and energy produced by PV system can be seen in Fig. 6. From the figure, it’s clear that PV system energy generation reach the highest in May and July, and has a sudden decrease in June because the temperature is too high in June. The energy from grid, annual grid feed in and own consumption of three load profiles of 3 kW system can be seen in Figs. 7–9. It can be seen from the figs that PV system with residential load needs more energy from the grid and has the lowest level of own consumption. PV system with residential load has the highest level of annual grid feed in. On the contrary, PV system with industrial load needs the least energy from the grid and has the highest level of own consumption. PV system with residential load has the lowest level of annual grid feed in. The energy from grid, annual grid feed in and own consumption of three load profiles of 3 kW system can be seen in Figs. 10–12. From the figures, it’s clear that the 3 kW system has higher level of energy from grid and much lower level of annual grid feed in. Even
Fig. 6. Energy production and consumption.
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Fig. 7. Energy from grid of 3 kW PV system with three load profiles.
Fig. 11. Annual grid feed in of 10 kW PV system with three load profiles.
Fig. 8. Annual grid feed in of 3 kW PV system with three load profiles.
Fig. 12. Own consumption of 10 kW PV system with three load profiles.
Fig. 9. Own consumption of 3 kW PV system with three load profiles.
Fig. 10. Energy from grid of 10 kW PV system with three load profiles.
increase installation power from 3 kW to 10 kW, own consumption energy hasn’t rise to much. The payback period of 3 kW PV systems are 14.4 years, 12.6 years, 12.4 years respectively under residential, commercial, industrial load. The NPV are 3876.52, 5127.77, and 5236.49 USD for PV systems under residential, commercial, industrial load. The return on assets are 4.56%, 5.82%, and 5.93% correspondingly. The selfconsumption rate is 60.4% for residential, 74.7% for commercial load and 77.7% for industrial load. The degree of self-sufficiency rate is 36.5% for residential, 45.2% for commercial load and 47.0% for industrial load. The payback period of 10 kW PV system are 11.6 years, 11.0years, 10.9years respectively under residential, commercial, industrial load. The NPV are 16101.93, 17813.80, and 18027.16 USD for PV systems under residential, commercial, industrial load. The return on assets are 6.52%, 7.10%, and 7.17% correspondingly. The self-consumption rate is 20.5% for residential, 27.1% for commercial load and 28.7% for industrial load. The degree of selfsufficiency rate is 43.6% for residential, 57.5% for commercial load and 61.0% for industrial load. It’s clear from this section that when combined with different load profiles, economic benefits are quite different. PV system with industrial is the most profitable, for industrial load has the most coincidence with PV system generation and residential load has the least coincidence with PV system generation. The 10 kW system has lower payback period and higher degree of self-sufficiency than 3 kW system. The degree of return on assets of 10 kW system is higher than 3 kW system. PV system under residential has the lowest level of return on assets and industrial has the highest. PV system combined with industrial load is more economic than commercial load and residential load, because when combined with industrial load, PV system has lower payback period than others. With increase of installed power, payback period will be decreased meanwhile the degree of self-sufficiency
W. Wang et al. / Energy and Buildings 130 (2016) 98–106 Table 5 Simulation Results of 3 kW PV System. 3 kW
Residential
Commercial
Industrial
Payback period (years) NPV (USD) Return on assets (%) Self-consumption rate (%) Self-sufficiency rate (%)
14.4 3876.52 4.56 60.4 36.5
12.6 5127.77 5.82 74.7 45.2
12.4 5236.49 5.93 77.7 47.0
Table 6 Simulation Results of 10 kW PV System. 10 kW
Residential
Commercial
Industrial
Payback period (years) NPV (USD) Return on assets (%) Self-consumption rate (%) Self-sufficiency rate (%)
11.6 16101.93 6.52 20.5 43.6
11.0 17813.80 7.10 27.1 57.5
10.9 18027.16 7.17 28.7 61.0
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of NOx, CO2 , and SO2 are 1316.8 kg, 308120 kg and 3787 kg. For the BAPV system, the annual value of the total environmental economic benefit is 20.07 USD/kWp. For the BIPV system, the annual value of the total environmental economic benefit is 22.17 USD/kWp. The result means both the systems has a good environmental benefit.
Acknowledgments This work is supported by Natural Science Foundation of China (Nos. 11374204, 11674215), “Shu Guang”and “Chen Guang” projects of Shanghai Municipal Education Commission and Shanghai Education Development Foundation (Nos. 13SG52, 12CG63), project of Science and Technology Commission of Shanghai Municipality (No. 11160500700), and Innovation Program of SMEC (No. 12ZZ174).
References increased. The self-sufficiency rate raise with the rise of PV installation power, and reach a steady state depending on the load profiles. The self-consumption rate decrease with the PV installation power. The payback period, self-sufficiency and self-consumption rate and other parameters can be seen in Tables 5 and 6. Depreciation rate of the system can be calculated as 1−residual rate . The depreciation time of both two systems are 25 depreciation time years. The residual rate of the two systems are 5%. The PV arrays of 3 kW system has lower residual rate than 10 kW system because the 3 kW system installed earlier when the PV module was not well developed compared with modules of nowadays. But the 3 kW system has less framework than 10 kW system, and for the residual rate of framework is lower than that of PV modules and pull down the overall residual rate, the ultimate residual rate of the two systems can be estimated as a same value of 5%. The depreciation rate of two systems can be calculated as 3.8%. That is 213.465 USD/year of BAPV system, and 470.01 USD/year of BIPV system. If using the sun of the years digits method, the annual discount time−number of years that has been used rate is depreciable × 100%. The depredepreciable time×(depreciable time +1)/2 ciable rate of every year are 7.69, 7.38, 7.08, 6.77, 6.46, 6.15, 5.85, 5.54, 5.23, 4.92, 4.62, 4.31, 4.00, 3.69, 3.38, 3.08, 2.77, 2.46, 2.15, 1.85, 1.54, 1.23, 0.92, 0.62, 0.31(%) namely. 6. Conclusion This paper mainly analyses economic and environmental benefit the BAPV and the BIPV system in Shanghai, China. The output yield of the BAPV and BIPV systems are 3114.3 kWh and 9890.7 kWh, the corresponding solar radiation quantity is 1181.3 kWh/m2 . Monthly performance ratios of the two systems are 80.8% and 80.3% respectively, and monthly system efficiencies of the two systems are 10.8% and 11.2%. This paper uses NPV and the Pd as the parameters to determine the profitability of the system based on some actual measured data. PV SOL software is used to analyze the NPV and Pd as well as other parameters of these two systems under different load profiles considering current tariffs which are carried out in 2016. Three load profiles combined with two PV systems are simulated in this paper and economic benefits are analyzed. EPBT of the two systems are 4.2 years and 3.1 years, for GPBT they are 1.3 years and 0.4 years, GHGrate of the two systems are 44 g/kWh and 60 g/kWh. The ratio of energy consumptions of PV modules are 77.42% and 87.31%, while energy consumptions of BOS systems only occupy for 22.58% and 12.69% respectively. So energy consumption is mostly aroused by PV modules. The reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 359.5 kg, 85200 kg and 1032.4 kg. For the BIPV system, the reduced emissions
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Contents lists available at ScienceDirect
Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild
Environmental assessments and economic performance of BAPV and BIPV systems in Shanghai Wenli Wang a , Yongsheng Liu a,∗ , Xinfang Wu a , Yan Xu a , Wenying Yu a , Chunjiang Zhao a , Yunbo Zhong b a b
Institute of Solar Energy, Shanghai University of Electric Power, Shanghai 200090, China School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
a r t i c l e
i n f o
Article history: Received 24 April 2016 Received in revised form 27 July 2016 Accepted 29 July 2016 Available online 29 July 2016 Keywords: Photovoltaic power system Economics Programming environments
a b s t r a c t This paper mainly analyses two systems in Shanghai. A Building Attached Photovoltaic (BAPV) system of 3 kWp and a Building Integrated Photovoltaic (BIPV) system of 10 kW. This BAPV system is the first practical application of grid-connected roof-mounted BAPV systems in China. It has great significance to the research of BAPV systems and the development of China renewable energy. The output yields, monthly performance ratio (PR), and monthly system efficiencies of the two systems of the two systems are illustrated. This paper used net present value (NPV) and the payback period (Pd ) to analyze system benefits. PV SOL is used to simulate these two systems combined with three load profiles. The simulation results including economic and performance states are illustrated in this paper. Moreover, energy payback time (EPBT) and greenhouse-gas payback time (GPBT) are used to evaluate environmental impacts. EPBT of the two systems are 4.2 years and 3.1 years, for GPBT they are 1.3 years and 0.4 years. The economic benefit of contaminating emission reduction of the two systems is also assessed to promote the development of PV industry. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The energy construction of China is quietly unreasonable, since coal-fired power plants account for more than 60% of the total power generation, solar power generation only reaches 0.06%, wind power is about 4% in year 2015. In China, energy consumption is mainly depends on coal-fired, which is the main reason for environmental pollution and greenhouse-gas, thus our air will be foul and disruptions to our climate will threaten us all. Furthermore, the most conventional energy distributes in northwest China and north China, but China’s energy consumption is mainly concentrates in southeast coast region whose economy is relative developed. In other words, there is a significant difference in the occurrence of resources and energy consumption areas in China. In order to ease the problem, more and more researchers focus on the renewable energy. As a kind of new energy, solar energy has many advantages such as pure, renewable, abundant etc. [1]. Furthermore, compared with other renewable energies, solar energy is the most abundant and inexhaustible [2–5]. To promote the development of solar
∗ Corresponding author. Tel.: +86 21 35303922; fax: +86 21 68029219. E-mail address: [email protected] (Y. Liu). http://dx.doi.org/10.1016/j.enbuild.2016.07.066 0378-7788/© 2016 Elsevier B.V. All rights reserved.
energy, several policies were proposed by Chinese government, such as the plan of solar roof of buildings. Solar energy can be used in many forms like solar heating, solar photovoltaic, solar thermal electricity, etc. [6,7]. As a new concept to use solar energy, the building photovoltaic power system has been proposed. This paper analyzed the building attached photovoltaic (BAPV) system and the building integrated photovoltaic (BIPV) system [8,9]. It’s necessary to evaluate economic benefits in the PV industry. The system uses net present value (NPV) and payback time (Pd ) to determine profitability. Several researches have been already illustrated to assess the economic benefit of PV system by using NPV and the Pd [10–12]. In its life cycle, balance of system (BOS) production, installation, and system disposal or recycling require much energy. Life cycle assessment (LCA) is perfect to evaluate the sustainability of PV system. Energy payback time (EPBT) and Greenhouse-gas payback time (GPBT) are institute ways to evaluate environment benefit. The environmental benefits of the PV systems in literatures [13–17] are all assessed by researchers. Economic and environmental benefits of the BAPV system and the BIPV system in Shanghai, China are analyzed in this paper.
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2. The model of BAPV system and BIPV system Nomenclature S Cgen Cinv Cinst Csystem Csub
The initial cost Generator cost Inverter cost Installation cost System cost The possible quantity of financial subsidy on the initial cost CO&M The cost of operation and maintenance Cins Insurance cost Egrid The annual amount of inputting electricity to the grid Ec The amount of using PV electricity per year The inflation rate g i The nominal interest rate t The t year The lifespan of PV N Ppv The PV electricity tariff The coal electricity tariff Pc Pd The payback time Qt The profit made in year t Eoutput The amount of energy generated by the PV system per year ES The energy consumption of PV modules EBOS The energy consumption of BOS components GHGPV The total GHG emission with respect to PV modules GHGBOS The total GHG emission with respect to BOS components GHGoutput The emission prevented by installing the PV system GHGrate The GHG emission rate of per unit electricity power generated by PV system
2.1. The concept of BAPV system and BIPV system As above, building photovoltaic power system consists of BAPV system and BIPV system. For the BAPV system, the PV arrays are attached to the roof through the simple supportive structures. They can be easily installed, and have a short construction period and low installation costs. But the building load is increased and the overall effects of the building would be affected. Additionally, in the building surface, BAPV also has a repeated construction problem that will lead to the waste of the building materials. For BIPV system, the PV arrays are integrated into the envelope structure of the building effectively, which becomes an indivisible part of the building. As a result, BIPV can overcome the shortcomings generated by the BAPV system [18,19]. When choosing PV systems, we should considering the advantages and disadvantages of the two models, photovoltaic technologies, architectural forms, costs and other building site situations. 2.2. The models of the two systems The BAPV system of 3 kWp is located in Minhang district, while the BIPV system of 10 kWp is located in Pudong New Area. Both the area are in Shanghai (latitude of 31◦ 12 N and longitude of 121◦ 24 E), China. Both the systems face south with an installed angles are 25◦ . Automated data monitoring systems were installed for data acquisition, including PV ambient temperature, solar radiation and electricity generated data. The weather station of both systems are located near the PV systems. The radiation measuring instrument is installed on the same surface the PV array with a setting angle of 25◦ . The temperature measuring instrument is installed nearby the PV array with good ventilation. The BAPV system is the first practical application of a gridconnected roof-mounted BAPV system in China and has great significance to the research of BAPV and the development of China renewable energy. It started to work in later December 2006. The
Fig. 1. The environment conditions of the BAPV system.
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Fig. 2. The environment of the BIPV system.
Polycrystalline silicon photovoltaic modules was installed on the roof in order to provide electricity for the building and reduce indoor heat load. The PV system is made of 22 polycrystalline silicon photovoltaic modules with a total area of 22m2 . Since there are no surrounding buildings, the PV array is covered without any shadow as shown in Fig. 1. It is beneficial for the conversion of PV array. On the standard condition, the open-circuit voltage and operating voltage of the BAPV system are DC 535 V and DC 427 V. While, the short-circuit current and the operating current of the system are DC 7.43 A and DC 7.01 A. The total installed capacity is 2992 Wp. Fig. 2 shows the photovoltaic roof structure appearance of the 10 kWp BIPV system, which adopts the monocrystalline silicon solar modules to converter radiation to electricity. The PV system forms an integrated photovoltaic roof instead of the traditional concrete pouring layer structure. This system includes PV roof array, inverters, AC protection switch devices and measuring instruments. It connects to the grid partly. The rooftop PV array includes a total number of 54 monocrystalline silicon PV modules (185 Wp per modules) and forms six string in total. Each string consists of nine pieces of modules in series. The string can be divided into three groups with each two string in parallel. The groups connect to three single-phase grid-connected inverters, whose specification is GT2.8ST. Under the standard condition, for each series group, the operating voltage and current are about DC 320 V and 5.2 A. The open-circuit voltage is between 370 V and 380 V, and the output power is from 1660 W to 1670 W. As a result, the total installed capacity is about 9.99 kWp. 2.3. Performance of the systems BIPV/BAPV systems is designed according to weather condition (temperature, humidity, solar radiation), and these data can be found in Meteonorm software and used to design PV systems. The productions and consumptions of two systems are recorded and calculated by dynamic data recorded by data acquisition system. The data of the two systems used to calculate system efficiency are based on the real one completely. An automated data monitoring systems were installed for data acquisition, including the solar radiation quantity, the generation power, the surface temperature, etc. The time interval is 5 min. We choose data of one typical year
Fig. 3. Monthly output yield and solar radiation quantity of the two systems.
to analysis the performance of these two PV systems. Fig. 3 shows the monthly output yield and solar radiation quantity. From Fig. 3, it can be found that the monthly output yield of 3 kWp system varies from 185.9 kWh in February to 357.4 kWh in August. The total output yield is 3114.3 kWh. While the monthly output yield of 10 kWp system varies from 470.3 kWh in February to 1020.4 kWh in April with a total value of 9890.7 kWh. Solar radiation quantity reaches maximum value of 134.7 kWh/m2 in July, and the minimum value is 58.6 kWh/m2 in February. The yearly total solar radiation quantity is 1181.3 kWh/m2 . The output yield and the solar radiation quantity of the two systems in winter are much smaller than that in summer. Both the parameters in June are smaller than that in May and July due to the rain. The performance ratio (PR) represents the relationship between the actual and theoretical energy outputs of the PV system. The loss may be caused by array temperature, incomplete utilization of the irradiation, and so on. We can use PR to compare different PV systems with different geographical location or rated power. We can also use PR to monitor the status of the PV power station over a long operation time. Fig. 4 shows the PR and system efficiency of the two systems. PR of 3 kWp system varies from 78.1% in December to 83.0% in July. The average PR is 80.8%. Meanwhile, the PR of 10 kWp system varies from 77.9% in April to 84.1% in October with an average value of 80.3%. Based on PR, the performance of 3 kWp
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Qt means the difference between the savings achieved in electricity bill and incurred expenses in consequence of the investment [21]. By considering the cost variation, Qt can be expressed as the following formula: Qt = Ppv Egrid + Pc Euse − (CO&M + Cins ) (1 + g)t
(7)
In the formula g represents the inflation rate. According to the above formulas, NPV of the grid-connected PV system can be expressed as the following formula:
Qt Q2 Q1 Qn + +···+ n = −S + t 2 (1 + i) (1 + i) (1 + i) (1 + i) t=1 (8) p
NPV = −S +
Fig. 4. Monthly performance ratio and system efficiency of the two systems.
system is a little better than the 10 kWp system. The average system efficiency of 3 kWp is 10.8%, while it is 11.2% of 10 kWp. System efficiency represents the performance of the overall PV array. The 10 kWp system was installed by monocrystalline PV modules, while 3 kWp system used polycrystalline silicon PV modules. The conversation efficiency of monocrystalline PV modules is larger than that of polycrystalline silicon PV modules. System efficiency in winter is much larger than that in summer. It can be attributed to high temperature in summer which can increase the surface temperature of PV modules. PR of the system can be affected by low efficiency caused by shelter of rain and dust, temperature, irradiance, power loss of inverter, cables, and transformer etc. The PR varied with seasons considerably mainly because of the temperature, irradiance, and shelter caused by rain and dust. Temperature and irradiance of PV systems are higher in summer than in winter and shelter caused by rain and dust is less in July than in December. Changing of temperature will cause decrease of output voltage, increase output current, and decrease actual efficiency as well as the output power of PV systems. Temperature is one of the important factors that affect PR of PV systems. Temperature deviate more from standard temperature in winter than in summer. That is the reason why PR varied with seasons considerably.
The payback period (Pd) means capital turnover using the following formula to calculate.
−S +
P t=1
Qj (1 + i)
t
=0
(9)
3.2. The model of the environmental assessment Through the life cycle of PV system, it consumes some energies, and generates some greenhouse gases (GHG) during power generation process. Since LCA is a technique for assessing various aspects associated with the development of a product and potential impact throughout a product’s life. So it is used to analyze the environment effects generated by the production of raw materials, the processing and purification, the manufacturing of modules and BOS components, the installation and utilization of the systems, and finally the decommissioning and disposal or recycling of the PV system [22–24]. The EPBT, Greenhouse Gas per kilowatt hour (GHGrate) and GPBT are used to value environmental benefits. 1) EPBT
3. The economic assessment of the two systems EPBT can be calculated by the following formula: 3.1. The model of the economic assessment NPV is used for financial appraisal [20], and can be expressed as follows: NPV =
p
EPBT =
ES +EBOS Eoutput
(11)
2) GHGrate (CI − CO)(1 + i)
−t
(1)
t=0
CI: cash inflows; CO: cash outflows; i: the nominal interest rate; p: the lifespan of PV (years); t: project age limit. The initial investment S for PV systems is calculated by (2): S = Cgen + Cinv + Cinst − Csub = Csystem − Csub
(2)
The cash inflows and outflows of the connected-grid system in year t can be shown as (3) and (4): CI = PPV Egrid + Pc Euse
(3)
CO = Co&M + Cins
(4)
CO&M + Cins = ˛Csystem
(1 + i)
25
i(1 + i)
−1 25
(˛ = 0.5%)
GHGrate is selected to compare the sustainability and “greenness” with different types of power generation systems. For PV power systems, the GHG emission rate can be expressed as the ratio of the total GHG emissions of PV system (including BOS) to the amount of the generated electricity during its life cycle. Equation (12) shows the calculation of the GHG emission rate in a specific PV system [25]. GHGrate =
(12)
3) GPBT
(5) GPBT is expressed as follows:
The net cash flow Qt in year t can be expressed as the following: Qt = CI − CO = Ppv Egrid + Pc Euse − (CO&M + Cins )
GHGS + GHGBOS Eout
(6)
GPBT =
GHGS + GHGBOS GHGoutput
(13)
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Table 1 The Investment of System of 3 kWp.
Table 3 The Economic Benefit of Contaminating Emission Reduction of 3 kWp.
Initial investment (USD/kW)
1872.5
The emissions
NOx
CO2
SO2
Lifespan (year) Annual output yield (kWh/kW) Discount rate PV electricity tariff (USD/kWh) Grid-connected electricity
25 1000 3% 0.1498 0–100%
Generation capacity of coal system (kg/MWh) Generation capacity of PV system (kg/kW) The amount of emission reductions (kg) The cost of pollution management (USD/kg) The environmental benefit (USD)
5 5.16 359.5 1.1984 430.82
1180 1100 85200 0.0034 293.55
14 5.85 1032.4 0.7550 779.45
Table 2 The Investment of System of 10 kWp. Initial investment (USD/kW)
1947.4
Lifespan (year) Annual output yield (kWh/kW) Discount rate PV electricity tariff (USD/kWh) Grid-connected electricity
25 1044 3% 0.1498 0–100%
4. Results of economic and environmental assessment 4.1. Result of economic assessment The investments of the two systems are shown in Tables 1 and 2. The initial investment of PV modules of the 3 kWp system is higher than that of 10 kW. The reason is that, system installation of 3 kWp is earlier than the installation of 10 kWp, when the instruments were more expensive such as PV modules, inverters, etc. The BAPV system can be easily installed, and have low installation costs as well as a fraction of framework expenses. So the overall investment of the 3 kW BAPV system is lower than the 10 kW system, because of the lower installation cost and framework expenses. Annual output power of 10 kWp is larger than that of 3 kWp, the lifespan of two systems are all 25 years. According to the latest rules in 2016, PV feed in tariff in Shanghai of PV stations will be 0.1468USD/kWh in 2016 and with downside of 0.003USD/year until year 2020. The subsidy in Shanghai is 0.063USD/kWh provided by government and 0.045USD/kWh provided by Shanghai government in the first 5 years. This paper mainly analysis small grid connected PV systems with electrical appliances. The feed in tariff of these kinds of systems is equal to desulfurization coal power plant electricity price which is 0.067USD/kWh in Shanghai. The inflation rate is set to be 2%. The NPV and payback period have significant difference according to load profiles, they will be illustrated in detail in Simulation sections. 4.2. Result of environmental assessment The energy consumptions of PV modules of the two systems are 107240 MJ and 453100 MJ, which are equal to 4662.61 MJ/m2 and 6041.33 MJ/m2 . This result has been researched by several literatures [26–30]. Energy consumptions of BOS systems are 31284 MJ and 65840 M [36]. Total energy consumptions of the systems are 138524 MJ and 518940 MJ, The ratio of energy consumptions of PV modules are 77.42% and 87.31%, while energy consumptions of BOS systems only occupy for 22.58% and 12.69% respectively. So energy consumption is mostly aroused by PV modules. The annual saved energy consumptions are 32730 MJ and 120021 MJ of the two systems. Based on formula (11), EPBT of the two systems are 4.2 years and 3.1 years. The total amount of GHGemission of BAPV system within its lifespan is 3300 kg [36]. While for the BIPV system, the total amount of GHGemission is 16376 kg. As BIPV system uses PV modules as the building roof instead of the traditional building materials, so GHGemission could be reduced by building materials by 12779 kg.
The annual reductions of GHGemission are 2520 kg and 9241 kg, both the corresponding reductions of per kWh are nearly 0.84 kg. GHGrate of the two systems are 44 g/kWh and 60 g/kWh. GHGrate of the BIPV system is higher than that of BAPV system. One possible reason is that PV modules in BIPV system are monocrystalline silicon while PV modules in BAPV system are polycrystalline silicon. Researches have been proved that GHG emission of monocrystalline silicon PV modules is larger than that of polycrystalline silicon PV modules. Based on formula (13), GPBT of the two systems are 1.3 years and 0.4 years. According the above analysis, both systems have a good environmental benefit and the BIPV system has better environmental benefits than the BAPV system. Tables 3 and 4 show the economic benefit of contaminating emission reduction of the two systems. Based on the literatures [31–35], the associated emissions of sulfur dioxide (SO2 ), nitrogen oxides (NOx), and carbon dioxide (CO2 ) of the system must be considered within its lifespan to research the advantage of PV systems by comparing the emissions of PV system with that of conventional power plants. The reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 359.5 kg, 85,200 kg and 1032.4 kg. For per kWp, the reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 119.8 kg, 28400 kg and 344.1 kg. For the BIPV system, the reduced emissions of NOx, CO2 , and SO2 are 1316.8 kg, 30,8120 kg and 3787 kg, which are equivalent to 131.7 kg/kWp, 30,812.0 kg/kWp and 378.7 kg kWp. Comparing the two systems, the reduced emissions of NOx, CO2 , and SO2 of the BAPV system for per kWp are smaller than that of the BIPV system. Meanwhile, the emissions of CO2 could be reduced by building materials by 12,779 kg. By converting the emissions reduction into economic benefit, the related environmental economic benefits of the BAPV system are 430.82 USD, 293.55 USD and 779.45 USD. They can be also expressed as 143.61 USD/kWp, 97.84 USD/kWp and 259.84 USD/kWp. The total environmental economic benefit of the BAPV system within its lifespan is 1503.83 USD, the corresponding yearly average value is 60.15 USD, for per kWp, the annual value is 20.07USD/kWp. For the BIPV system, the related environmental economic benefits are 1577.99 USD, 1105.67 USD and 2859.08 USD. They are 157.80, 110.57 and 258.91 by the unit of USD/kWp. The total environmental economic benefit of the BIPV system within its lifespan is 5542.75 USD, the corresponding yearly average value is 221.70 USD, for per kWp, the annual value is 22.17USD/kWp. So the annual environmental economic benefit is 22.17USD/kWp. It can be found that the related environmental economic benefits of the BIPV system are larger than that of the BAPV system. As a conclusion, the BIPV system has a better environmental benefit than the BAPV system. Furthermore, systems of BIPV and BAPV could reduce energy consumption and emission in building. This result is valuable for the government to promote investment in PV projects base on the data. Meanwhile, we should consider the cost of external parts, which is consist of the effects on public health (including deaths) and on the environment (the climate change is taking place since human bring). For example, GHG which is generated by human activities like population could arouse climate change [36]. The application of solar energy should
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Table 4 The Economic Benefit of Contaminating Emission Reduction of 10 kWp. The emissions
NOx
CO2 (system)
Generation capacity of coal system (kg/MWh) Generation capacity of PV system (kg/kW) The amount of emission reductions (kg) The cost of pollution management (USD/kg) The environmental benefit (USD)
5 5.82 1316.8 1.1984 1577.99
1180 1638 308120 0.0034 1061.63
CO2 (building material)
SO2
12779 0.0034 44.04
14 6.31 3787 0.7550 2859.08
be promoted not only by technologies, but also depends on politics and policy issues.
5. Simulation If we combine these two systems with certain load profile and analyze with PV SOL under current subsidy and feed in tariff, the results will be more meaningful. PV SOL is a fully functioned, practicality German PV design software. PVSOL is a software that can be used to build PV programs. Grid-connected PV systems, grid-connected PV systems with electrical appliances, grid-connected PV systems with electrical appliances and battery systems, these three kinds of PV systems can be built and simulated. Climate data depend on locations and can be obtained from Meteonorm software or created by your own climate data with import files. PV systems can be planned and designed with 3D visualization. Simple roof area, complex buildings, and open area can be used to place PV systems. Several kinds of trees, walls, and buildings nearby PV systems can also be simulated in the program building process. The most suitable inverter can be chosen by your own adjustment and cable loss can be calculated in detail using parameters set by yourself. Several types of load profiles like business load, agriculture load, industrial load, and household load are available in building the PV program. Load profiles can also be built using hourly data in every season and holiday. Initial investment, consumption and operation cost, feed in tariff, and from grid tariff can be set in the economic analysis part. System energy balance, economic analysis, and performance of the PV systems can be calculated as base results. During this simulation, the PV SOL example poly modules are selected as electricity generation section and equipped with inventers. The cable is set in detail, and the total loss is 0.12%. The feed in tariffs are present tariffs mentioned above. Three kinds of load profiles are located in this paper, namely residential load, commercial
Fig. 5. Three load profiles.
load, and industrial load. The load profile of one day can be seen in Fig. 5 [37]. The annual energy consumption is 5000 kWh. The results of simulation with PV SOL can be seen in Figs. 6–12. Figs. 7–12 is production forecast with consumption of 3 kW and 10 kW. The consumption and energy produced by PV system can be seen in Fig. 6. From the figure, it’s clear that PV system energy generation reach the highest in May and July, and has a sudden decrease in June because the temperature is too high in June. The energy from grid, annual grid feed in and own consumption of three load profiles of 3 kW system can be seen in Figs. 7–9. It can be seen from the figs that PV system with residential load needs more energy from the grid and has the lowest level of own consumption. PV system with residential load has the highest level of annual grid feed in. On the contrary, PV system with industrial load needs the least energy from the grid and has the highest level of own consumption. PV system with residential load has the lowest level of annual grid feed in. The energy from grid, annual grid feed in and own consumption of three load profiles of 3 kW system can be seen in Figs. 10–12. From the figures, it’s clear that the 3 kW system has higher level of energy from grid and much lower level of annual grid feed in. Even
Fig. 6. Energy production and consumption.
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Fig. 7. Energy from grid of 3 kW PV system with three load profiles.
Fig. 11. Annual grid feed in of 10 kW PV system with three load profiles.
Fig. 8. Annual grid feed in of 3 kW PV system with three load profiles.
Fig. 12. Own consumption of 10 kW PV system with three load profiles.
Fig. 9. Own consumption of 3 kW PV system with three load profiles.
Fig. 10. Energy from grid of 10 kW PV system with three load profiles.
increase installation power from 3 kW to 10 kW, own consumption energy hasn’t rise to much. The payback period of 3 kW PV systems are 14.4 years, 12.6 years, 12.4 years respectively under residential, commercial, industrial load. The NPV are 3876.52, 5127.77, and 5236.49 USD for PV systems under residential, commercial, industrial load. The return on assets are 4.56%, 5.82%, and 5.93% correspondingly. The selfconsumption rate is 60.4% for residential, 74.7% for commercial load and 77.7% for industrial load. The degree of self-sufficiency rate is 36.5% for residential, 45.2% for commercial load and 47.0% for industrial load. The payback period of 10 kW PV system are 11.6 years, 11.0years, 10.9years respectively under residential, commercial, industrial load. The NPV are 16101.93, 17813.80, and 18027.16 USD for PV systems under residential, commercial, industrial load. The return on assets are 6.52%, 7.10%, and 7.17% correspondingly. The self-consumption rate is 20.5% for residential, 27.1% for commercial load and 28.7% for industrial load. The degree of selfsufficiency rate is 43.6% for residential, 57.5% for commercial load and 61.0% for industrial load. It’s clear from this section that when combined with different load profiles, economic benefits are quite different. PV system with industrial is the most profitable, for industrial load has the most coincidence with PV system generation and residential load has the least coincidence with PV system generation. The 10 kW system has lower payback period and higher degree of self-sufficiency than 3 kW system. The degree of return on assets of 10 kW system is higher than 3 kW system. PV system under residential has the lowest level of return on assets and industrial has the highest. PV system combined with industrial load is more economic than commercial load and residential load, because when combined with industrial load, PV system has lower payback period than others. With increase of installed power, payback period will be decreased meanwhile the degree of self-sufficiency
W. Wang et al. / Energy and Buildings 130 (2016) 98–106 Table 5 Simulation Results of 3 kW PV System. 3 kW
Residential
Commercial
Industrial
Payback period (years) NPV (USD) Return on assets (%) Self-consumption rate (%) Self-sufficiency rate (%)
14.4 3876.52 4.56 60.4 36.5
12.6 5127.77 5.82 74.7 45.2
12.4 5236.49 5.93 77.7 47.0
Table 6 Simulation Results of 10 kW PV System. 10 kW
Residential
Commercial
Industrial
Payback period (years) NPV (USD) Return on assets (%) Self-consumption rate (%) Self-sufficiency rate (%)
11.6 16101.93 6.52 20.5 43.6
11.0 17813.80 7.10 27.1 57.5
10.9 18027.16 7.17 28.7 61.0
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of NOx, CO2 , and SO2 are 1316.8 kg, 308120 kg and 3787 kg. For the BAPV system, the annual value of the total environmental economic benefit is 20.07 USD/kWp. For the BIPV system, the annual value of the total environmental economic benefit is 22.17 USD/kWp. The result means both the systems has a good environmental benefit.
Acknowledgments This work is supported by Natural Science Foundation of China (Nos. 11374204, 11674215), “Shu Guang”and “Chen Guang” projects of Shanghai Municipal Education Commission and Shanghai Education Development Foundation (Nos. 13SG52, 12CG63), project of Science and Technology Commission of Shanghai Municipality (No. 11160500700), and Innovation Program of SMEC (No. 12ZZ174).
References increased. The self-sufficiency rate raise with the rise of PV installation power, and reach a steady state depending on the load profiles. The self-consumption rate decrease with the PV installation power. The payback period, self-sufficiency and self-consumption rate and other parameters can be seen in Tables 5 and 6. Depreciation rate of the system can be calculated as 1−residual rate . The depreciation time of both two systems are 25 depreciation time years. The residual rate of the two systems are 5%. The PV arrays of 3 kW system has lower residual rate than 10 kW system because the 3 kW system installed earlier when the PV module was not well developed compared with modules of nowadays. But the 3 kW system has less framework than 10 kW system, and for the residual rate of framework is lower than that of PV modules and pull down the overall residual rate, the ultimate residual rate of the two systems can be estimated as a same value of 5%. The depreciation rate of two systems can be calculated as 3.8%. That is 213.465 USD/year of BAPV system, and 470.01 USD/year of BIPV system. If using the sun of the years digits method, the annual discount time−number of years that has been used rate is depreciable × 100%. The depredepreciable time×(depreciable time +1)/2 ciable rate of every year are 7.69, 7.38, 7.08, 6.77, 6.46, 6.15, 5.85, 5.54, 5.23, 4.92, 4.62, 4.31, 4.00, 3.69, 3.38, 3.08, 2.77, 2.46, 2.15, 1.85, 1.54, 1.23, 0.92, 0.62, 0.31(%) namely. 6. Conclusion This paper mainly analyses economic and environmental benefit the BAPV and the BIPV system in Shanghai, China. The output yield of the BAPV and BIPV systems are 3114.3 kWh and 9890.7 kWh, the corresponding solar radiation quantity is 1181.3 kWh/m2 . Monthly performance ratios of the two systems are 80.8% and 80.3% respectively, and monthly system efficiencies of the two systems are 10.8% and 11.2%. This paper uses NPV and the Pd as the parameters to determine the profitability of the system based on some actual measured data. PV SOL software is used to analyze the NPV and Pd as well as other parameters of these two systems under different load profiles considering current tariffs which are carried out in 2016. Three load profiles combined with two PV systems are simulated in this paper and economic benefits are analyzed. EPBT of the two systems are 4.2 years and 3.1 years, for GPBT they are 1.3 years and 0.4 years, GHGrate of the two systems are 44 g/kWh and 60 g/kWh. The ratio of energy consumptions of PV modules are 77.42% and 87.31%, while energy consumptions of BOS systems only occupy for 22.58% and 12.69% respectively. So energy consumption is mostly aroused by PV modules. The reduced emissions of NOx, CO2 , and SO2 of the BAPV system are 359.5 kg, 85200 kg and 1032.4 kg. For the BIPV system, the reduced emissions
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