The Department of mechanical, energy and management engineering of an Italian university has developed a computer code based on combined statistical and numerical methods, allows the selection of a pump suitable for operation as a turbine (PAT) in microhydro power plants, with the data of the hydraulic resource and the technical characteristics supplied by centrifugal pump manufacturers.
In an energy scenario today characterized by an impoverishment of traditional energy sources, the exploitation of small energy resources is attractive and is now an obligation. The plants exploit micro-hydraulic resources (less than 100 kW) that, although interesting, are penalized by the excessive cost of small turbines. The use of PAT (pumps as hydraulic turbines) is a smart and important alternative. Centrifugal pumps are mass-produced for a wide range of heads and flow rates, so their main cost is lower than that of the turbines and their maintenance is easier, due to the availability of spare parts, even in developing countries. The efficiency of these machines will be lower but, since they exploit otherwise wasted energy sources, this is not a critical problem. The application of PAT in the pico / micro-hydroelectric range is recommended for energy production in rural, remote and hilly areas where water streams flow with a certain level difference. Other interesting fields of application are:
- energy recovery from drinking water networks, wherever there are hydraulic pressure drops induced by the aqueduct regulating valves;
- energy recovery from irrigation systems, where pipelines with relatively high flow rates and pressures are present.
- energy recovery from the water supply pipe of the purification plants.
From the economic point of view, it is often stated that pumps operating as turbines in the range of 1 to 100 kW involve payback periods of two years or less, which is considerably lower than that of a conventional turbine. Unfortunately, although a large number of centrifugal pumps are commercially available for a hydroelectric micro-engineering plant, the manufacturers do not provide information on the performance of centrifugal pumps in turbine mode. Therefore, establishing a procedure that allows the passage from the characteristics of the "pump" to the characteristics of the "turbine" is the main challenge in the use of a PAT (pump as a turbine).
Through this procedure a pump is selected, its characteristic curves are obtained in the inverse operating mode and, finally, the operating point is identified. This also makes it possible to estimate the annual energy yield of the machine and the comparison of alternative solutions.
The Italian University is looking for international partners who are interested in implementing the proposed technology, in order to recover energy more efficiently. The cooperation will be carried out in the framework of commercial agreements with technical assistance.