Minimum maintenance solar pump
A minimum maintenance solar pump (MMSP), Fig 1, has been simulated for Addis Ababa, taking solar meteorological data of global radiation, diffuse radiation and ambient air temperature as input to a computer program that has been developed. To increase the performance of the solar pump, by trapping the long-wave light rays leaving the absorber - the water tank, two glass covers have been employed. Basic heat transfer equations for double glass glazing and storage tank (absorber plate) along with side and bottom insulations are derived and techniques for the solution of these equations are presented. The minimum quantity of residual water that should remain in the storage tank after the previous day's pumping process, for producing the required maximum vacuum pressure, has been determined. The maximum possible pumping head which depends on the vacuum pressure created within the storage tank and which in turn depends on the quantity of residual water evaporated has then been predicted and presented for representative days of the year.