Figure 5 . Daily PV power generation of BIPV and BIPVT collector
The reason why the amount of PV power generation got a difference between BIPV and BIPVT collectors can explain in figure 6 . Figure 6 is a graph comparing the average temperature of the PV module in the BIPV and BIPVT system . The graph shows the PV module temperature was changed according to the change in solar radiation . The PV module temperatures increased as the solar radiation increased . Both PV module temperature of BIPVT and BIPV system was increased according to the solar radiation increase , but the PV module temperature of BIPVT collector was lower than that of BIPV . The temperature of BIPV was 15 ~ 58 ° C for one day , and the BIPVT collectors were 12 ~ 41.8 ° C . It was analyzed that the PV temperature of the BIPVT system had been kept by lower than BIPV by exiting the heat with air , and it can help to prevent from degradation of PV power generation according to temperature increase of PV module .
Figure 6 . Effect of time on PV temperature and solar radiation on BIPVT and BIPV system
The following figure 7 compares the electrical efficiency of the PV module in BIPV and BIPVT system , and the efficiency was calculated by equation : ηη ��� �
��� � �� ��
( 1 ) where ηη ��� , VV , II , AA �� and GG are the electricity efficiency ( ‐ ), maximum voltage ( V ), maximum current ( A ), PV area ( m 2 ) and global solar radiation ( W / m 2 ), respectively . In the case of BIPV , when solar radiation increased more than 600W / m 2 , it was found that the electrical efficiency was decreased . The reason why the electricity efficiency of BIPV was degraded is the increase of PV module temperature according to the high solar radiation . The electrical efficiency of the PV module decreases about 0.5 % each time when it increases 1C from 25 ° C of PV module temperature . However in the PVT
Experimental Performance of an Advanced Air Type Photovoltaic-Thermal ( PVT ) Collector with Direct Expansion Air Handling Unit ( AHU ) 406