New hydropower converters for very low-head differences

There is a significant but unused hydropower potential with head differences below 2.5 m in many countries. Standard turbine types are considered not economical in this situation, since large turbine diameters and extensive civil engineering works are required. In addition, ecological effects need to be considered. Recently, a novel power-conversion mechanism which utilizes hydrostatic force differences was developed at Southampton University. Two different applications were developed: (1) the hydrostatic pressure wheel for head differences between 0.2 and 1 m and (2) the hydrostatic pressure machine for head differences between 1 and 2.5 m. Theoretical analysis and four series of model tests were conducted. Efficiencies ranged from 0.5 to 0.9 for (1) and up to 0.8 for (2). The simplicity of the machines suggests economical advantages, while the slow speed, the continuity of the bed and the large cells promise good ecological characteristics.