Abstract
Pumped Hydropower Storage (PHS) is the maturest and most economically viable technology for storing energy and regulating the electrical grid on a large scale. Due to the growing amount of intermittent renewable energy sources, the necessity of maintaining grid stability increases. Most PHS facilities today require a geographical topology with large differences in elevation. The ALPHEUS H2020 EU project has the aim to develop PHS for flat geographical topologies. The present study was concerned with the initial design of a low-head model counter-rotating pump-turbine. The machine was numerically analysed during the shutdown and startup sequences using computational fluid dynamics. The rotational speed of the individual runners was decreased from the design point to stand-still and increased back to the design point, in both pump and turbine modes. As the rotational speeds were close to zero, the flow field was chaotic, and a large flow separation occurred by the blades of the runners. Rapid load variations on the runner blades and reverse flow were encountered in pump mode as the machine lost the ability to produce head. The loads were less severe in the turbine mode sequence. Frequency analyses revealed that the blade passing frequencies and their linear combinations yielded the strongest pulsations in the system.
Highlights
The demand to control and regulate the electrical grid to provide grid stability is ever increasing
The current study investigated the shutdown and startup sequences for a model-scale CRPT, in both pump and turbine modes
Preliminary shutdown and startup sequences were numerically evaluated for a model counter-rotating pump-turbine in both pump and turbine modes
Summary
The demand to control and regulate the electrical grid to provide grid stability is ever increasing. This is a consequence of the fact that intermittent renewable energy sources, e.g., wind and solar, are on the rise and will continue to increase in the coming decades [1]. Pumped Hydro Storage (PHS) is the maturest and most cost-efficient solution to store energy and provide grid stability [2,3,4]. PHS facilities require very specific site locations to make them economically feasible. According to Deane et al [6], the head of the PHS facility is the most essential criterion, and a higher head is preferable.
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