Technical - Economical and Environmental Analysis of Utilization of Solar Water Heating Systems in Residential Buildings

In this paper, based on geographic specifications and climatic conditions, the required natural gas and hot water of a typical 8-units residential building located in Tehran city, has been taken into consideration and analyzed in two scenarios considering the national and international prices of natural gas and electricity. In scenario A, utilization of a forced circulation solar water heating system for supplying the required hot water based on national prices for electricity and natural gas and in scenario B, utilization of the same system considering international prices for electricity and natural gas were investigated through using RETScreen software. The results show that in scenarios A and B, the share of solar water heating system in supplying the required hot water is 53%. The amount of natural gas saving would be 4,777 m3/yr. The total investment costs and green house gases (GHGs) emission reduction would be US$ 7,898 and 6.4 tCO2/yr respectively. In scenario A, annual external costs diminution would be US$ 123 tCO2 and normal payback period would be 16.9 yr. In scenario B, annual external costs diminution and normal payback period would be US$ 101 tCO2 and 6.3 yr respectively. Thus using the solar water heating systems with considering the international prices of electricity and natural gas is economically feasible.