Environmental Life-Cycle Analysis of Hybrid Solar Photovoltaic/Thermal Systems for Use in Hong Kong

Table 6

Evaluation of cost payback time.

Investment: HK$	Free-stand PV/T [6]	BiPV/T [7]
Water storage tank	400	750
Collector frame and support	400	1800
Modular thermal absorber	600	2700
Solar cells and encapsulation	4000	17500
Inverter	700	1000
Piping, wiring and accessories	300	900
Installation costs	1500	3000
Total system costs (HK$)	7900	27650
Useful energy savings	MJ (kWh)	MJ (kWh)
Thermal energy	2650.4 (736.2)	8127.5 (2257.6)
Electrical energy	473.2 (131.4)	1162.4 (322.9)
Space cooling load	—	742.6 (206.3)
Cost savings: HK$
Gaseous fuel at HK$0.2/MJ	530.1	1625.5
Electricity at HK$0.95/kWh	124.9	372.0
Annual saving	655.0	1997.5
Cost payback time (CPBT)	12.1 years	13.8 years

Note: USD1 is equivalent to HK$7.8.