The technology has the following characteristics: · single reservoir – removing the need for a 2nd reservoir and associated infrastructure, thereby reducing CAPEX by > 50% compared with the standard 2 reservoir project · can be installed in gulfs, mine pit lakes, as well as reservoirs, and off-shore; the deeper the water body, the higher its storage capacity · modular & scalable – enabling standardised components to be manufactured off-site, agglomerated to a desired scale and deployed in paralel with a floating or standard solar farm. OLPHES can store 1 MWh into a concrete cylinder with 20 m radius and 20 m height, that floats on a lake, like in the above animation, has a reversible pump-turbine at the bottom, that is powered by solar or wind energy. Increasing the hight of the cylinder to 100 m, the storage capacity increases to 5 MWh, generating 1MW for 5 hours. OLPH its easily to scale up further 10 times, by floating 9 similar cylinders, that are positioned circular and share the reversible pump-turbine with the central one by connecting pipes.​ OLPHES light can be build from inflatable rubber cylinders.