Exergy analysis of solar energy systems - Solar Energy Sciences and Engineering Applications - page 116

3.4 CONCLUDING REMARKS

This chapter discusses energy and exergy related aspects of solar energy systems, con-
siders various solar energy-based systems for analysis, assessment and comparison,
and evaluates them for practical applications from the exergy point of view.

Nomenclature
A Area of solar module, m 2

b Breadth of PV module, m

COP Coefficient of performance

c Specific heat, kJ/kg · K

cp Specific heat at constant pressure, kJ/kg · K

E x

Exergy rate, kW

ex i Specific exergy at state i, kJ/kg · K

ex ph i Specific physical exergy at state i, kJ/kg · K

ex ch i Specific chemical exergy at state i, kJ/kg · K

h Specific enthalpy, kJ/kg

Heat transfer coefficient from black surface to air, W/m 2 h ba · K

Heat transfer coefficient from black surface to air through glass, W/m 2 h t · K

h p1G Penalty factor due to the presence of solar cell material, glass and EVA for

glass to Glass PV/T system, W/m 2 · K

h p2G Penalty factor due to presence of interface between glass and working fluid

through absorber plate for glass to glass PV/T system, W/m 2 · K

Solar flux, W/m 2 I

L Length of the PV module, m

m ˙ Mass flow rate, kg/s

P Pressure, kPa

Q

Heat transfer rate, kW

s Specific entropy, kJ/kg · K

T Temperature, K

u Specific internal energy, kJ/kg

Overall heat transfer coefficient from bottom to ambient, W/m 2

U b · K

U L Overall heat transfer coefficient from solar cell to ambient through

top and back surface of insulation, W/m 2 · K

U t Overall heat transfer coefficient from solar cell to ambient through glass

cover, W/m 2 · K

U tb Overall heat transfer coefficient from glass to black surface through

solar cell, W/m 2 · K

v Specific volume, m 3 /kg

W

Work rate, kW

z Variable

Greek letters
α c

Absorptance of solar cell

α b Absorptance of painted black surface