Integrating a wind- and solar-powered hybrid to the power system by coupling it with a hydroelectric power station with pumping installation

The high variability of solar and wind energy sources makes their integration into power systems complicated and in some cases unnecessarily delays their transition from centralised to dispersed energy sources. In this paper, a mixed-integer non-linear mathematical model has been developed for simulating the integrated operation of a novel hybrid involving wind- and solar power and a hydroelectric power station with pumping installation. This hydropower plant is a special case of pumped storage hydroelectricity which to some extent utilises the available flow of the river on which it is located. It is thereby able to compensate for the varying energy output from the wind turbines (WT) and photovoltaics (PV) by discharging water previously pumped to the upper reservoir (or held back from the available flow) when a surplus from WTs and/or PVs occurs. The impact on the national power system (NPS) has been investigated based on the energy exchange values (unexpectedly occurring deficits and surpluses) between the considered hybrid energy source and the grid. The obtained results indicate that such a hybrid energy source not only significantly reduces the total volume of the energy exchange with the grid but also minimizes the ramp rate of those values. Accumulating water from available flow rate minimizes the need for oversizing the capacity installed in PVs and WTs. However, the inherent variability and typically low heads of existing run-off-river power plants with pondage lead to the size of the upper reservoir being prohibitive. The conclusions show that such a type of pumped storage hydroelectricity should mainly be used on a small scale. (C) 2017 Elsevier Ltd. All rights reserved.