The efficient use of human energy for micro-scale irrigation

The potential for improving the efficiency of micro-scale irrigation in Africa through the use of simple human powered pumps is discussed. In a series of tests carried out in Harare, Zimbabwe the sustainable performances of three hand-operated pumps, the rope-washer, the Rower and the Bumi and one foot-operated pump, the treadle, were evaluated. Human power output was calibrated against heart rate for two subjects. This calibration, in conjunction with heart rate monitoring during pump operation was used to assess pump efficiencies in enabling human energy and effort to raise water for irrigation. The rope-washer pump, which is the cheapest and easiest to make of the pumps tested, performed surprisingly well at all pumping heads, producing similar outputs to that of the treadle pump. The Bumi pump gave good flow rates but only at low heads while the Rower pump gave the lowest outputs over a restricted range of pumping heads. The results demonstrate the importance of designing for foot rather than hand operation in order to achieve the best efficiency of utilization of human effort and indicates that sustainable pump power outputs in excess of 40 W are possible with the pumps tested. A strong preference for a narrow operating speed range, 30 to 50 rev/min, was confirmed for both hand and foot operation.