Promotion the efficiency of thermosyphon solar-electrical water heater using daily scheduled timer key

The solar radiation energy is one of the clean, essential and renewable resources for future. Iran, having 300 annual sunny days, has such intrinsic potential and thermosyphon solar-electrical water heaters (TSEWH) are the simplest solar-thermal convertors. Despite their unique merits, they can not supply hot water for domestic applications during cold period, so, an auxiliary backup system such as electrical resistance heater (electrical element) is required. The reduction of consumed electrical energy by electrical element not only leads to decrease of electrical network load, but also enhances the solar water heater efficiency and speeds up their application in the buildings sector. Careful scheduling the electrical element circuit via a timer key (timing mode operating) leads to reduction of auxiliary portion compared to the case that its circuit to be activated permanently (continues mode). Field results imply that, implementation the timer key to TSEWH has been considerable during cold period and reduced the consumed electrical energy as much as700kWh yearly and promoted its annual efficiency from 46% up to 67%.