Abstract
Although electricity generation is steadily increasing in Ethiopia, a bias between the grid extension and the load of power generated resulted in shortage of electricity and thus frequent power cut. Limited electricity service makes the reliable power supply in isolated system more attractive. The use of renewable energy and particularly the solar thermal energy represents one of the most promising alternative strategies. Ethiopia is in a relatively sunny area with an average global horizontal radiation of 5.2kwh per meter squares a day and 6.25kwh per meter square a day in Diredawa. The residential sector represents 87% of the total energy consumption and thus offers an interesting opportunity for the development of solar thermal market. In this paper an attempt is made to examine and explore the impact of the use of solar thermal equipment for heating and hot water on an energy saving and as substitute in the residential sector considering Diredawa city as a model. The energy consumption is calculated for the typical building using validated polysun solar thermal simulation model. Two model systems are considered, one in which only solar thermal is used to supply energy demand but there is no energy savings. In the second model, heat pump is coupled with solar thermal. The system not only covered the energy demand but also showed the maximum energy savings of 3857.2Mcal. The payback period is calculated for heating and hot water for model system one is 4 years. The analysis showed that the payback period of the system is 3 years for the second model of the system.