ZEMCH 2019 International Conference Proceedings April.2020 | Page 385
h �� is the heat loss coefficient between the back panel and ambient air. The useful thermal energy and
efficiency of dual fluid PV/T system are given as follows:
(7)
Q � � � � C � �T �,� � T �,�� � � � � C � �T �,� � T �,�� �
ŋ �� �
� �
� � �
(8)
where Q � and ŋ �� are the useful thermal energy and efficiency of the dual-fluid PV/T system. The
equivalent thermal efficiency can be calculated as:
ŋ ��� � ŋ �� � ŋ � /ŋ ��
(9)
ŋ ��� and ŋ � are the equivalent thermal and electrical efficiencies, respectively. ŋ �� is the electric
generation efficiency of the conventional power plant and its value is taken as 38%.
2.2. Exergy Analysis
Exergy is a thermodynamic concept which defines every transformation process undergoes the
loss of measure of quality, especially considering low quality energy such as thermal energy (heat)
which involves temperature change. Exergy analysis becomes more important when the extraction of
maximum useful work from the system is concerned. Exergy balance for single‐fluid PV/T system given
by Agrawal and Tiwari [18], is modified for the dual‐fluid PV/T system for this study. Following
equations show the inflow and outflow of exergy from the proposed system [19].
∑ Ex � �∑ E �� � ∑ Ex �
(10)
Ex � is the overall exergy gain, and E �� and Ex � are the thermal and electrical exergy gains,
respectively. For dual‐fluid PV/T system the thermal exergy gain is the sum of thermal exergy agains
associated with circulating pipe fluid (E ��,� ) and air (E ��,� ), respectively, can be expressed as follows:
∑ E �� � ∑ E ��,� � ∑ E ��,�
(11)
∑ E ��,� � Q � � � � C � �T � � ��3�log �
� �,� ����
�
� �,�� ����
(12)
∑ E ��,� � Q � � � � C � �T � � ��3�log �
� �,� ����
� �,�� ����
(13)
�
Q � and Q � are the useful thermal gain associated with circulating pipe fluid and air, respectively.
ŋ � �� �
∑ Ex � � �
����
(14)
�
Performance Evaluation of Photovoltaic/Thermal (PV/T) System Using
Different Design Configurations
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