Abstract
The increasing penetration of variable renewable energies (VRE) in the European electricity mix requires flexible energy storage systems (ESS), such as pumped storage hydropower (PSH). Disused mining voids from deep closed mines may be used as subsurface reservoirs of underground pumped-storage hydropower (UPSH) plants. Unlike conventional PSH plants, the air pressure in UPSH plants is variable and it differs from the atmospheric conditions. In this paper, the hydraulic transient process of an UPSH plant operating in pumping mode was investigated and a preliminary thermodynamic analysis of the closed surge tank was carried out. Analytical and CFD three-dimensional numerical simulations based on the volume of fluid (VOF) model with two-phase flow have been performed for analyzing the transient process. In the transient simulation, air and water are considered as ideal gas and compressible liquid, respectively. Different guide vanes closing schemes have been simulated. The obtained results show that the dimensioning of underground reservoir, surge tank, and air ducts is essential for ensuring the hydraulic performance and optimizing the operation of UPSH plants. The static pressure in the air duct, surge tank and lower reservoir reaches −1.6, 112.8 and −4 kPa, respectively, while a heat flux of −80 W was obtained through the surge tank walls.
Highlights
In 2019, renewable energies generated 34.6% of Europe’s electricity [1]
Renewable generation increased by 65 TWh in 2019, exceeding the 2010–2018 average of 50 TWh per year. This high level of renewable energy sources (RES) production was mainly attributable to an increase in wind generation
The increasing of some ways of intermittent renewable energy sources (RES), such as wind and solar PV, is making energy storage systems (ESS) increasingly important for balancing electricity supply and demand [2,3]
Summary
In 2019, renewable energies generated 34.6% of Europe’s electricity [1]. Renewable generation (excl. hydro) increased by 65 TWh in 2019, exceeding the 2010–2018 average of 50 TWh per year.This high level of renewable energy sources (RES) production was mainly attributable to an increase in wind generation. In 2019, renewable energies generated 34.6% of Europe’s electricity [1]. Hydro) increased by 65 TWh in 2019, exceeding the 2010–2018 average of 50 TWh per year. This high level of renewable energy sources (RES) production was mainly attributable to an increase in wind generation. Since 2015, 84% of the growth in total renewables generation has come from wind, 18% from solar, and 10% from biomass [1]. The increasing of some ways of intermittent renewable energy sources (RES), such as wind and solar PV, is making energy storage systems (ESS) increasingly important for balancing electricity supply and demand [2,3].
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