PUMPS THAT PLAY TURBINES.

Water distribution systems that contain pressure reducing or flow control valves offer the possibility of a potential source of revenue to the water authority. These devices all act to reduce hydraulic head and restrict flow. They waste energy which could otherwise be converted to hydroelectric power. To economically tap this potential revenue source, engineers are now looking to standard centrifugal pumps, operating in reverse as hydroelectric turbines. The potential for hydroelectric power production is primarily a function of the quantity of flow and the size of the differential head available. Differential head is roughly the difference between the available upstream hydraulic gradient and the required downstream gradient. Due to the relatively narrow operating range of centrifugal pumps, their use as hydroelectric turbines is usually in applications where constant flow rate and differential head are available. Several options, however, are available to increase the operating range of reverse-pump turbine systems and provide a low-cost source of hydroelectric power over a broad range of flow and head conditions. These options are discussed in the article.