A conventional SWH system has three major parts: the solar
collector, water tanks and auxiliary heating equipment. In this
study, both towngas and electricity are selected as auxiliary energy
sources. The former system is called towngas boosted SWH and the
later one is electricity boosted SWH.
Fig. 4illustrates the basic components of the electricity boosted
SWH system which consists of flat plate solar collectors, a 0.4 m
3
solar hot water tank, a storage water tank of 0.28 m
3
and an elec-tric water heater with a rated heating capacity of 11 kW. In the
towngas boosted SWH system, a towngas water heater of 11 kW
is used instead of the electric water heater.