Small scale, one-size-fits-all, solar water pumps

This project proposes the development of a novel solar powered, water-pumping system for irrigation – either direct to irrigation or to an intermediate water storage facility. Building on recent work at the University of Liverpool, the system will be “one-size fits all” – i.e the same pump system will be used irresepctive of well depth (up to e.g. 10m), but still giving optimum performance. The system will also be designed to be modular, allowing quick and simple maintenance. Two key problems exist in solar water-pumping technology: 1. the ability of a pump to start under low solar irradiance; and 2. the matching of pumps to specific locations. Without complicated electronics, positive displacement pumps are rarely able to achieve either of these. The first of these becomes more realistic with centrifugal pumps, which begin to spin with low input power and then pump once “critical” rotational speed is reached. However, centrifugal pumps have defined operating characteristics – away from their intended output head they operate at low efficiencies and with low water output. Research at the University of Liverpool, using novel “induced flow” technology, has demonstrated proof of concept in a system that significantly broadens the operating conditions of centrifugal pumps. For example, a small 12V input pump, with only 6V input (equivalent to low sunlight), was still able to operate at 5 times its design output head and twice its normal maximum head, but with efficiency similar to its peak. In the laboratory, the system is manually tuned to the operating conditions, but with electronic control systems could be made to auto-tune itself to the conditions in which it is situated. However, this project will investigate the feasibility of providing a “passive” system with minimal electronics. We will explore how broad the operating conditions can be without changing the pump system/electronics, aiming to optimise system performance whilst minimising system complexity. The design will be fully modular, to allow easy and cheap manufacture/maintenance/replacement. The "one-size fits all" nature of the entire system is expected to significantly reduce costs, through providing economies of scale. In doing so, a single, non-site-specific, low-cost pumping unit would be able to pump water from a multitude of sources, to any given height-demand, be it for human consumption, animal consumption or irrigation.