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An integrated energy system (with photovoltaic (PV) and fuel cell (FC) for building) is proposed and assessed in term of its energy self-sufficiency rate in seven cities (Nagoya, Toyota, Tajimi, Takayama, Ogaki, Hamamatsu, Shizuoka) in Tokai region in Japan in this paper. In this work, it is considered that the electricity requirement of the building for household users is provided by a building integrated photovoltaic (BIPV) system and the gap between the energy demand and BIPV supply is fulfilled by the FC. The FC is powered by the electrolytic H
_{2} produced when PV power was in surplus. Based on the study of applying the proposed system in seven cities, which clarifies the effectiveness of the integrated BIPV, electrolytic H
_{2} and FC power generation system, a universal system model has been developed in this paper. It has been observed that the monthly power production from BIPV as well as FC system are higher in spring and summer, while they are both lower in autumn and winter at all considered locations. The self-sufficiency rate of the FC system is higher with decreasing households’ number and it has been observed that 16 is the most appropriate number of households in a building, whose electricity demand could be fully covered by the integrated PV and FC system. Due to its climate condition, Hamamatsu is the best city in the region for installing the proposed system. The correlation between the households’ number and self-sufficiency rate of the FC system per solar PV installation area can be expressed by the regression curve in the form of
*y = ax*
^{-b} well.

According to Energy White Paper 2017 in Japan [

Recently, the so-called building integrated PV systems (BIPV) have been attracted attention from the world [_{2} is superior to battery to store the large amount of renewable energy for a long time [_{2} [_{2} and fuel cell power generation system [_{2} and fuel cell (FC) power generation system and for developing the universal system model.

In this paper, a desk top case study has been performed to simulate a proposed BIPV system with utilization of stored energy in the form of electrolytic H_{2} and the stored H_{2} is used to fuel FC to generate the power for a building when the power generated from the BIPV is insufficient for the building. The proposed integrated BIPV + FC system consists of the solar PV array, water electrolyzer and FC. The H_{2} is generated and stored with the surplus power of the BIPV. The FC would therefore be able to buffer the intermittency (partly) between the building electricity demand (by the building) and the PV system. To investigate the impact of local climate condition on the performance of the proposed integrated system, two cities in Aichi prefecture (Nagoya, Toyota), three cities in Gifu prefecture (Tajimi, Takayama, Ogaki) and two cities in Shizuoka prefecture (Hamamatsu, Shizuoka) in Tokai region, Japan have been selected to the locations for the desk-top case study. Their meteorological data are from the project “PV300” (period from August, 2013 to July, 2014) [

The building model, used in the design study, is 10 m width, 40 m length and 40 m height (=10 stories) [^{2} per a household. The height of one floor is assumed as 4 m. Assuming that four households stay per floor, the floor space is 400 m^{2}. This study proposed the building model utilizing the accelerated wind between buildings for a power generation by wind turbine and assessed the power generation performance of wind turbine of 50 kW class whose height was 39 m [^{2} areas, and a FC using electrolytic H_{2} produced when there is the surplus power from BIPV [

The power generated by PV system is calculated by using the following equation [

E P V = H × K × P / 1 (1)

where E_{PV} is hourly electric power of PV system (kW∙h), H is hourly amount of solar radiation (kW∙h/m^{2}), K is power generation loss factor (−), P is system capacity of PV (kW), 1 is solar radiation under standard state (AM1.5, hourly solar radiation: 1 kW∙h/m^{2}, module temperature: 25 degree Celsius) (kW/m^{2}). The instantaneous solar radiation data by 10 sec of the reference [

In this study, the high-performance PV P250α Plus produced by Panasonic has been considered. This module has conversion efficiency and maximum power rating per module is 19.5% and 250 W [_{p} (=300 solar modules). To calculate K, the performance value of state-of-the-art commercial devise is used. K is calculated by using the following equation [

K = K p × K m × K i (2)

where K_{p} is power conversion efficiency of power conditioner (−), K_{m} is correction factor decided by module temperature (−), K_{i} is power generation loss by interconnecting and dirty of module surface (−). In this study, K_{p} and K_{i} are set at 0.96 and 0.95, respectively. K_{p} is assumed by referring to the performance of commercial power conditioning device VBPC259B3 manufactured by Panasonic [_{m} is calculated by the following equation [

K m = 1 − ( T m − T s ) C 100 (3)

where T_{m} is PV module temperature (degree Celsius), T_{s} is temperature under standard test condition (= 25 degree Celsius) (degree Celsius), C is temperature correction factor which is 0.35 [_{m} is calculated by using the following equation [

T m = T a + ( 46 0.41 U m 0.8 + 2 ) H − 2 (4)

where T_{a} is ambient air temperature (degree Celsius), U_{m} is wind velocity over module of PV (m/s). In this equation, the convection heat transfer by wind around the PV module is considered.

The meteorological data, such as solar radiation, the ambient air temperature, and wind velocity of the cities involved in the study have been taken from the data base of the project “PV300” for the period from August, 2013 to July, 2014 [

In this study, it has been assumed that the surplus power generated by the PV system over the electricity demand of households [_{2} production (i.e. long term energy storage in the form of electrolytic H_{2}). To optimize the size of BIPV system,

Year | Month | Day | Hour | Min | Sec | Amount of horizontal solar radiation (kW/m^{2}) | Air temperature (degree Celsius) |
---|---|---|---|---|---|---|---|

2013 | 8 | 1 | 10 | 0 | 0 | 0.2826 | 26.2 |

2013 | 8 | 1 | 10 | 0 | 10 | 0.2828 | 26.2 |

2013 | 8 | 1 | 10 | 0 | 20 | 0.2825 | 26.2 |

2013 | 8 | 1 | 10 | 0 | 30 | 0.2826 | 26.3 |

2013 | 8 | 1 | 10 | 0 | 40 | 0.2822 | 26.3 |

2013 | 8 | 1 | 10 | 0 | 50 | 0.2808 | 26.3 |

2013 | 8 | 1 | 10 | 1 | 0 | 0.2799 | 26.2 |

2013 | 8 | 1 | 10 | 1 | 10 | 0.2777 | 26.2 |

2013 | 8 | 1 | 10 | 1 | 20 | 0.2747 | 26.2 |

2013 | 8 | 1 | 10 | 1 | 30 | 0.2721 | 26.2 |

2013 | 8 | 1 | 10 | 1 | 40 | 0.2690 | 26.2 |

2013 | 8 | 1 | 10 | 1 | 50 | 0.2663 | 26.2 |

2013 | 8 | 1 | 10 | 2 | 0 | 0.2638 | 26.2 |

2013 | 8 | 1 | 10 | 2 | 10 | 0.2617 | 26.2 |

2013 | 8 | 1 | 10 | 2 | 20 | 0.2592 | 26.2 |

2013 | 8 | 1 | 10 | 2 | 30 | 0.2580 | 26.2 |

2013 | 8 | 1 | 10 | 2 | 40 | 0.2576 | 26.3 |

2013 | 8 | 1 | 10 | 2 | 50 | 0.2575 | 26.3 |

2013 | 8 | 1 | 10 | 3 | 0 | 0.2578 | 26.3 |

number of households has been varied by 40, 20, 16 and 12 which correspond to 10, 5, 4 and 3 stories of the building, respectively. In this study, the building which has 4 households per floor is assumed. Then, the multiple number of 4 is based for assessment. To keep a building structure, the lowest limit of stories is set at 3 which is the standard low height building, indicating 12 households. The Type-S electrolyzer manufactured by IHT [_{2} production rate, power consumption and electrolysis efficiency are 760 N∙m^{3}/h, 4.45 kW∙h/N∙m^{3} and 79.5%, have been used in this design study. The amount of electrolytic H_{2} could be produced by the surplus power generated from the PV system is calculated by the following equation:

V H 2 = E s / P e (5)

where V_{H}_{2} is amount of electrolytic H_{2} produced (N∙m^{3}), E_{s} is surplus power generated by PV system (kW∙h), P_{e} is power consumption (kW∙h/N∙m^{3}). In this study, it is assumed that the electrolyzer can be operated following the power generation characteristics of PV system every time and the produced H_{2} can be stored as well as used instantaneously [

It has been assumed that the H_{2} produced by the electolyzer would be used to generate power through a polymer electrolyte fuel cell (PEFC) system [_{2} is converted into electricity by FC following the below equation:

H 2 + 1 / 2 O 2 = H 2 O + η f Q (6)

where η_{f} is power generation efficiency of latest PEFC stationary system based on lower heating value (= 0.39) [_{2} (=242) (kJ/mol). It is assumed that the energy loss for operating pump to preserve and provide gases is ignored [

In this study, a monthly self-sufficiency rate of the proposed combination system consisting of the PV and FC has been investigated for Nagoya (Latitude: 35.10˚N, Longitude: 136.54˚E), Toyota (Latitude: 35.4˚N, Longitude: 137.9˚E), Tajimi (Latitude: 35.19˚N, Longitude: 137.7˚E), Takayama (Latitude: 36.8˚N, Longitude: 137.15˚E), Ogaki (Latitude: 35.21˚N, Longitude: 136.36˚E), Hamamatsu (Latitude: 34.42˚N, Longitude: 137.43˚E) and Shizuoka (Latitude: 34.54˚N, Longitude: 138.18˚E). They are the main cities in Tokai region located in the center of Japan. The self-sufficiency rate is defined as the power supplied (from the combined PV and FC system) to the electricity demand of the households living in the building. The hourly time change in the self-sufficiency rate in the day, when the daily mean amount of horizontal solar radiation per month has been obtained and estimated.

This study has investigated the power production from the PV system using the meteorological data base of PV300 [

summarized as hourly data by integrating the instantaneous data available at 10 sec intervals.

As an example,

Time (h) | Aug, 2013 | Sep, 2013 | Oct, 2013 | Nov, 2013 | Dec, 2013 | Jan, 2014 | Feb, 2014 | Mar, 2014 | Apr, 2014 | May, 2014 | Jun, 2014 | Jul, 2014 |
---|---|---|---|---|---|---|---|---|---|---|---|---|

0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

4 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

5 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4 | 4 | 6 |

6 | 13 | 4 | 3 | 1 | 0 | 0 | 0 | 2 | 7 | 17 | 14 | 13 |

7 | 21 | 11 | 12 | 8 | 2 | 3 | 6 | 14 | 22 | 33 | 18 | 23 |

8 | 32 | 26 | 25 | 20 | 13 | 14 | 16 | 30 | 35 | 38 | 24 | 38 |

9 | 29 | 11 | 22 | 30 | 23 | 26 | 23 | 43 | 42 | 38 | 31 | 34 |

10 | 41 | 31 | 22 | 37 | 21 | 35 | 36 | 53 | 46 | 45 | 22 | 41 |

11 | 43 | 44 | 29 | 26 | 35 | 40 | 37 | 56 | 52 | 55 | 37 | 47 |

12 | 55 | 49 | 29 | 26 | 29 | 23 | 37 | 53 | 57 | 52 | 30 | 60 |

13 | 50 | 39 | 22 | 11 | 31 | 21 | 28 | 18 | 48 | 39 | 50 | 49 |

14 | 35 | 42 | 20 | 21 | 13 | 27 | 31 | 14 | 34 | 46 | 38 | 22 |

15 | 26 | 28 | 12 | 4 | 8 | 15 | 17 | 10 | 19 | 32 | 42 | 13 |

16 | 16 | 15 | 7 | 2 | 1 | 3 | 8 | 8 | 7 | 24 | 27 | 6 |

17 | 8 | 4 | 0 | 0 | 0 | 0 | 1 | 1 | 3 | 8 | 13 | 6 |

18 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 | 2 |

19 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

20 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

21 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

22 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

23 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

Total | 370 | 303 | 202 | 185 | 176 | 207 | 241 | 303 | 373 | 431 | 354 | 362 |

constant value up to the midnight. In addition, it is obvious that the electricity demand is higher in summer and winter, especially at the night in summer. However, it is lower in spring and autumn.

Time (h) | Aug, 2013 | Sep, 2013 | Oct, 2013 | Nov, 2013 | Dec, 2013 | Jan, 2014 | Feb, 2014 | Mar, 2014 | Apr, 2014 | May, 2014 | Jun, 2014 | Jul, 2014 |
---|---|---|---|---|---|---|---|---|---|---|---|---|

0 | 3 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 4 | 3 | 2 | 3 |

1 | 3 | 3 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 3 | 2 | 3 |

2 | 3 | 3 | 3 | 3 | 3 | 4 | 4 | 3 | 4 | 3 | 2 | 3 |

3 | 3 | 3 | 3 | 3 | 3 | 4 | 4 | 3 | 4 | 3 | 2 | 3 |

4 | 2 | 2 | 3 | 3 | 3 | 4 | 4 | 4 | 4 | 3 | 2 | 2 |

5 | 2 | 2 | 2 | 2 | 3 | 4 | 4 | 4 | 2 | 2 | 2 | 2 |

6 | 7 | 6 | 7 | 7 | 7 | 8 | 8 | 7 | 8 | 7 | 5 | 6 |

7 | 9 | 8 | 8 | 8 | 10 | 13 | 12 | 11 | 9 | 8 | 7 | 8 |

8 | 10 | 9 | 8 | 8 | 11 | 14 | 13 | 12 | 9 | 8 | 8 | 9 |

9 | 9 | 8 | 8 | 8 | 10 | 13 | 12 | 11 | 9 | 8 | 7 | 8 |

10 | 9 | 8 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 7 | 8 |

11 | 9 | 8 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 7 | 8 |

12 | 10 | 9 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 7 | 8 |

13 | 11 | 10 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 8 | 9 |

14 | 11 | 10 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 8 | 9 |

15 | 10 | 9 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 7 | 9 |

16 | 10 | 9 | 8 | 8 | 10 | 12 | 12 | 11 | 9 | 8 | 7 | 8 |

17 | 10 | 9 | 8 | 8 | 14 | 17 | 16 | 15 | 9 | 8 | 7 | 8 |

18 | 14 | 13 | 13 | 13 | 14 | 17 | 16 | 15 | 15 | 13 | 11 | 12 |

19 | 25 | 23 | 19 | 19 | 16 | 19 | 18 | 17 | 22 | 19 | 19 | 22 |

20 | 25 | 23 | 18 | 19 | 15 | 18 | 17 | 16 | 21 | 19 | 19 | 22 |

21 | 24 | 22 | 16 | 17 | 14 | 17 | 16 | 15 | 19 | 17 | 18 | 21 |

22 | 20 | 18 | 15 | 16 | 12 | 15 | 14 | 13 | 18 | 16 | 15 | 17 |

23 | 17 | 15 | 15 | 15 | 9 | 11 | 11 | 10 | 17 | 15 | 12 | 14 |

Total | 257 | 232 | 208 | 214 | 220 | 272 | 259 | 240 | 237 | 211 | 192 | 221 |

study, it has been assumed that the surplus power of PV system is used to electrolyze water and the H_{2} produced is stored for fueling the FC to make up the shortage of power during the required time.

According to

The households’ number is changed to investigate the proper households’ number for same installment area of solar array on the roof/top of building. Figures 4-6 have shown the monthly self-sufficiency rate of FC system assumed to be installed in Nagoya, Toyota, Tajimi, Takayama, Ogaki, Hamamatsu and Shizuoka for 20, 16 and 12 households’ cases, where the stories of buildings are 5, 4 and 3, respectively. Figures 7-9 show the monthly mean temperature, mean wind velocity and sunshine hours [

It can be seen from Figures 4-6, the self-sufficiency rate of FC system is higher with decreasing households’ number. This is because that the surplus power of PV system increases with decreasing households’ number, i.e., decreasing electricity demand. In addition, the self-sufficiency rate of FC system can be over 100% in spring and summer while that is below in autumn and winter. This trend matches with the power generation characteristic of PV system. Though the electricity demand increases in summer, the power of PV system seems to be sufficient, resulting in the high self-sufficiency rate of FC system in summer. Comparing seven cities, the self-sufficiency rate of FC system from November to January in Takayama is lower than that in the other cities. Since Takayama has a lot of snow in winter which can be explained by short sunshine hours shown in _{2} generated. The self-sufficiency rate of FC system in Hamamatsu is high through the year, and it is over 100% even in winter for the 12 households’ case. Hamamatsu has long sunshine hours through the year

according to

_{2} obtained in the month whose monthly self-sufficiency rate is over 100% can be stored and provided for the month whose monthly self-sufficiency rate is below 100%. Therefore, the annual self-sufficiency rate of FC system is a good indicator to determine the optimum households’ number which can cover the electricity demand through the year.

According to

The correlation between the households’ number and self-sufficiency rate of FC system per solar PV installation area for two cities in Aichi Prefecture, three cities in Gifu Prefecture and two cities in Shizuoka prefecture has been shown in Figures 11-13, respectively. In these figures, the regression formula of the approximate curves and R^{2} error are also shown.

Formula show the correlation between the households’ number and self-sufficiency rate of FC system per solar PV installation area can be expressed in the form of y = ax^{b} well. It might be thought that the self-sufficiency rate of

FC system per solar PV installation area will increase for the households’ number which is smaller than 12. However, this study assumed that the lowest limit of stories were set 3 which was the standard low height building. Therefore, this study hasn’t considered the case for households’ number which is smaller than 12.

This study has proposed an integrated BIPV + FC system for Japanese buildings.

The FC is fueled by H_{2} which is generated from the surplus power generated from BIPV through electrolytic process. The self-sufficiency rates of the FC have been investigated using meteorological data of two cities in Aichi prefecture (Nagoya, Toyota), three cities in Gifu prefecture (Tajimi, Takayama, Ogaki) and two cities in Shizuoka prefecture (Hamamatsu, Shizuoka) of Japan to understand the impact of local climate condition on the performance of the proposed system as well as to find out a universal system model. As a result, the following conclusions have been drawn from the study:

1) The annual self-sufficiency rates of FC system for 16 and 12 households’ cases are over 100% in all cities studied. Therefore, 16 households (= 4 stories) are thought to be the optimum households’ number for the proposed BIPV + FC system.

2) Hamamatsu is the most appropriate city for installing the proposed BIPV + FC system among the seven cities studied.

3) The correlation between the households’ number (x) and self-sufficiency rate of FC system per solar PV installation area (y) can be expressed in the form of y = ax^{b} well, where a and b depend on the locations/cities.

Nishimura, A., Tanikaga, S., Hirota, M. and Hu, E. (2018) Energy Characteristics of an Integrated Power Generation System with Photovoltaic and Fuel Cell. Smart Grid and Renewable Energy, 9, 57-73. https://doi.org/10.4236/sgre.2018.94005