The historic city of Salamanca, crossed by the river Tormes, has about 330,000 citizens and is located northwest of Madrid. The drinking water supply network has several regulating valves that reduce pressure in certain areas of the municipality.

Thanks to the installation of the water turbine in parallel to one of the city’s pressure reducing valves (PRV´s), energy previously dissipated in the form of noise and heat in the valve itself is transformed in to usable electrical energy. The water turbine has been installed in parallel to the reducing valve by means of a bypass. In this way, part of the flow rate of the reducing valve is diverted by the water turbine to produce energy. Specifically, the water turbine works with a flow rate of 2.5 liters / second and a pressure drop of 22 meters, generating 175W of power.

The energy generated is stored in a 24 volt battery bank and has an offgrid inverter with 230 volts output (single-phase) and up to 1200W of power. To provide greater security in the energy supply, the batteries can be also recharged from the electrical network. Therefore, it is a hybrid system in which the primary source of energy is the water turbine and only in case of turbine failure or maintenance the energy is taken from the electrical network. The energy is used to supply the pump of a public water font.

Water turbine is located in an underground housing next to the pressure reducing valve (PRV). The rest of the electrical equipment (batteries, turbine control panel and inverter) has been installed inside a prefabricated metal cabinet on the street, next to the public water font.

Through this solution based on self-consumption, significant savings are achieved in the purchase of energy from the electricity company. The water turbine works 24 hours a day, 365 days a year, generating energy continuously. It is a pioneering initiative and widely replicable in any urban water distribution network with pressure reducing valves (PRVs).


Hydraulic turbine bypass
Water turbine cabinet

Installation date: July 2020

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