The gravity pump: a new approach to a natural energy water pump

The double-acting gravity pump is an environmentally friendly, positive-displacement device for pumping surface water using the natural energy resource of falling water as its motive power. The genesis of this design of pump derived from a need to generate high delivery pressures for rural water supply projects in the developing world; pressures that were beyond the capacity of the conventional ram pump. The paper outlines the theory behind the operation of the gravity pump and goes on to describe an experimental programme carried out on a prototype in order to prove the concept. The results of the experiments confirm the theoretical analysis in all respects and the performance of any configuration of gravity pump may now be forecast with confidence. The paper describes a second prototype pump destined for field trials, which is currently in the course of a construction. This version incorporates a number of design improvements following from the experience gained in building and testing the first pump. Research and development of the gravity pump is supported by an Invention and Innovation Award from the National Endowment for Science, Technology and the Arts (NESTA).