The high overall efficiency of around 85 percent is due to minimal friction losses within the system and the high efficiency of the machines used of (from 90 to 94 percent). The HDS is a closed system with short paths for the storage and propellant media, without foreign objects such as sand or sediments as they occur in a pumped hydro storage system. The efficiency remains stable over the entire operating area despite high flexibility and is independent of the operational sequence. Depending on the grid voltage and structure, transformers for infeed and outfeed can be avoided, which contributes to a further improvement in efficiency.
Due to the fact that it operates independently from external energy, the HDS is ideally suited for black starts – i.e. in the event that a network has to be repaired and stabilized with the help of an energy storage system after a sudden and complete power failure, so called blackout. This option is available with only a few power storage systems.
The turbines used are particularly suitable for high pressures greater than 100 meters of water column (mWS) and work in a control range between 10 and 100 percent with a consistently high level of efficiency. This range can be expanded to zero to 100 percent by additional measures.
A sensitive control and regulation system enables short-term load changes. This also ensures that the power output can be quickly adapted to the grid. With the help of an idling drive, the turbine and the generator are kept rotating so that they can run up to power in seconds, even when waiting.