A case study is carried out for economic comparisons of dif-ferent water heating systems. It is assumed that all the systems
studied have the same heating capacity and are designed to sup-ply hot water for one room with two persons in a hotel. Accord-ing to CIBSE GUIDE [11], the heating load should be able to heat
280 l water from 20Cto55C. The initial temperature of water
is set as 20C because the average dry bulb air temperature is
about 20C from February to May, a period during which the
lowest solar radiation occurs. If the heating load during this per-iod could be guaranteed, the system can then satisfy the hot
water requirement a year round. In order to use the same basis
for comparisons, the solar collector area of 6 m
2
is adopted and
the efficiency of solar collector loop is set as 0.4 for all the solar
thermal systems