Pumped hydropower storage (PHS) is a costeffective and mature energy storage technology. However, it has inherently been limited to locations with suitable topographies. Therefore, the ALPHEUS project aims to implement PHS for shallow seas and coastal environments with the goal to support grid stability. To ensure optimal efficiency and fast switching times in these low-head applications, a 10 MW Contra-Rotating (CR) axial Reversible Pump-Turbine (RPT) is designed, which has a rim diameter of 6.4 m and a high efficiency – maximum 84% and 90% for pump and turbine, over a large operating range. Furthermore, the RPT is rim-driven, which averts the hydraulic impact caused by shaft-driven systems. To ensure optimal efficiency at variable speed operation, the runners are driven by two separate Axial-Flux Permanent Magnet Synchronous Machines (AF-PMSMs).
Pumped Hydropower Storage (PHS) is an established and cost-efficient technology. In the ALPHEUS project, Reversible Pump-Turbines (RPT) and adjacent technologies are improved to make low head PHS economically viable . A 10 MW system is designed that is highly efficient and has low mode switching times, to allow to provide grid ancillary services. One of the investigated RPTs is a rim-driven Contra-Rotating (CR) RPT. Here, the two runners have opposite rotational motion, which limits the creation of swirl behind the RPT, thus increasing efficiency , improving pump stability and suppressing cavitation . The two runners are driven at their This research is part of the ALPHEUS project and is funded by the European Union’s Horizon 2020 research and innovation programme, grant agreement No 883553. rim by two separate electric machines. Therefore, the use of
conventional shafts is averted, alleviating the impact of the Power Take-Off (PTO) on the hydraulic efficiency.