P-PHES VELILLA is located in the province of Palencia, Spain. It is a reversible hydro storage power plant with an installed capacity of 143.81 MW (2 groups of 71.91 MW each) in generation mode and 144.4 MW in pumping mode. The maximum daily gross stored energy that can be obtained is 839 MWh.

The project comprises the construction of two reservoirs with a volume of 1.015 hm³ each (upper and lower). The water flows handled by the facility are 47 m³/s in generation mode and 34 m³/s in pumping mode. The static head is 363.9 m. According to the plant design, the round cycle efficiency reaches 77.8%.

The purpose of the project is, on the one hand, hydroelectric use of water from the drainage of acidic water from two nearby mines (currently closed) and on the other hand, the purification of such water, taking advantage of the physical phenomena that occur in the P-PHES, being its subsequent discharge into the usual watercourse in accepted quality conditions, in accordance with current regulations.

The vast majority of P-PHES VELILLA facilities are excavated in the ground and buries installations.

The maximum annual production of P-PHES VELILLA is estimated at 306,235 MWh/year, which will reduce CO₂ emissions from fossil fuels by approximately 62,471 tons of CO₂ per year of operation.

The concept and design used in the P-PHES, as in the case of VELILLA, is included in a Spanish patent, which has already been processed at European and international level.

The average water flow discharged by both mines and managed by the water treatment plant is approximately 3,500 m³/day.