Contributions to the preliminary assessment of a Water Pumped Storage System in Terceira Island (Azores)

•Proposal of an energy balance technical model for a wind/WPSS/thermal power system.•Proposal of an economic assessment model based on NPV and IRR.•Influence of Spinning Reserve requirements on economic feasibility enhancement.

The need to provide Spinning Reserve (SR), together with the need to respect some operational constraints, points to high power state combinations of the thermal power plants, therefore reducing the penetration of renewables in the power mix and eventually leading to wind curtailment. Water Pumped Storage Systems (WPSS) are a way to overcome this issue, by storing the surplus energy not needed in the valley periods, to use it later in peak periods. This situation is dealt with in this paper, through the proposal of an energy balance technical model, taking into account the constraints and operational limits of the thermal power plant, together with an economic model based on NPV and IRR. This model is applied to assess the Terceira Island case-study. Despite the fact that this is a simplified model, not using any optimization techniques, it was possible to conclude that WPSS provide both thermal based electricity and wind curtailment reduction, therefore facilitating the integration of renewable energy in the power system and enhancing the environmental aspects of electricity production. Moreover, it was found that there are turbine/pump sizing combinations that can turn the project into an economically viable one. Also, it was demonstrated that further economic feasibility could be achieved if SR requirements could be lowered. This aspect should be considered by Terceira system operator.