Solar Thermal Water Pumps: A Preliminary Analysis of the Working Process

Solar thermal water pumps are low cost and low maintenance devices with a pumping capacity of $0.2-1m3$/hour at a dynamic head of 1.5–5 m. The working fluid in the thermodynamic cycle is an air-steam mixture. In this paper we suggest a simple mathematical model to numerically simulate the internal processes in such a pump and determine the performance and physical dimensions of a preliminary design. The proposed mathematical model has been calibrated against experimental data and it provides the numerical simulation of the processes which occur in the cycle within an acceptable degree of accuracy for engineering purposes. The results of the analysis show that the performance of the solar water pump is mainly determined by the “steam” fraction of the cycle. The power of the solar thermal water pump increases with an increase in the maximum temperature in the cycle, while the indicated efficiency reduces because of the increase in the heat loss due to water vaporization and condensation processes.