A case study is carried out for economic comparisons of different water heating systems. It is assumed that all the systems
studied have the same heating capacity and are designed to supply 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 period 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