Performance Enhancement of Solar Water Heater with a Thermal Water Pump

In order to reduce weight on a building roof and save electrical energy for water circulation, a solar water heater with a built-in thermal water pump was introduced. However, such a system still does not have high enough effectiveness. The target of this study was to improve the efficiency of the solar water heater by eliminating critical losses such as vapor and head losses. Consequently, a new system of 1.58 m(2) flat plate solar collectors, an overhead tank placed at the peak level, a larger water storage tank without a heat exchanger at the lower level, a new vent tube and a one-way valve for water circulation control were constructed. The discharge head was reduced to be 0.5 m. A pump was powered by steam and air and operated at a solar collector temperature of about 70-80.2 degrees C and gauge pressure of 2.2-6.3 kPa. The stored hot water of the solar water heater ranged between 25 and 89.9 L/day. Furthermore, the max water temperature in the storage tank was roughly 64.6 degrees C. The max daily pump efficiency was about 0.0012%. For the 0.5 m h discharge head, the solar water heater had daily max thermal efficiency of about 41.2% compared to 17.4% for a previous system of the same type. The system simulation gave a reasonable agreement with the experimental results (error of less than +/-10%). Long-term performance and economic analysis were included. (C) 2014 American Society of Civil Engineers.