A 'new generation' solar operated low-power and low capital cost submersible diaphragm pump designed for medium head applications is evaluated in this paper. The pump is designed and made by SHURflo Ltd. and is the 9325 type. The primary use of this pump is in providing water for remote homes and clinics, for human consumption and for agricultural use. In all tests, the pump was connected to a dedicated controller that allows either 12 V or 24 V operation. The experiments were undertaken by using the pumping test rig at CRES, and the evaluation methodology was 'simulated field conditions'. The instantaneous water flow versus head characteristics were functions of the global irradiance on the array plane. The PV array power varied between 55 Wp and 220 Wp and both voltage modes were examined. The hydraulic efficiency was also calculated with respect to equivalent head. The daily operation charts were obtained by using the instantaneous pump performance in combination with typical daily irradiation profiles and the pump starting and stopping characteristics. These charts are useful for system sizing, taking into account the solar resource at the site of application, the required daily water delivery at a particular head and the available PV array. The results show that with this 'new generation' of direct solar-powered pumping systems, the PV array has been minimised, and so has been the capital investment cost, the need for battery storage has been eliminated and adequate water is delivered at an affordable price. (C) 2000 Elsevier Science Ltd. All rights reserved.
