Integrated management of hydropower reservoirs and variable renewable energy sources: a modelling framework for hybridization with solar photovoltaics

Variable renewable energy sources (VRES), like solar photovoltaics (PV), offer a power generation profile which is driven by climate-related variables and which is therefore different from the consumers’ electricity demand. Hydropower (HP), thanks to flexibility and storage capacity, can facilitate the introduction of high shares of VRES in the energy mix. Integrating VRES and HP in a single power station (hybridization) is a promising solution to smooth out VRES fluctuations and obtain more regular power generation profiles. Focusing on hybrid solar-hydro power stations, we present a modelling framework to quantitatively assess the effects of complementing a reservoir-based HP plant with a PV plant; the method relies on meteorological input data and on hydrological data, possibly obtained through hydrological modelling. The proposed approach is first tested on a numerical experiment to analyse the effects of increasing solar-hydro hybridization levels on a synthetic, yet realistic case study in south-eastern Alps. The methodology is then applied to a real Swiss pumped-storage HP plant located in the pre-Alpine region, which is assumed to be complemented through a fictional floating photovoltaic (FPV) plant. Simulations are first performed using historical (1981-2018) meteorological input data and hydrological data obtained through hydrological modelling; simulations are then repeated under 39 future climate projections (covering three emission scenarios over the period 1981-2099) derived from the latest downscaled and de-biased Swiss climate change scenarios CH2018, based on the EURO-CORDEX dataset. Results show that, at least in the study region, hybridization with PV has a significant positive effect on the performance of a reservoir-based HP plant under current climate conditions and may help to mitigate possible impacts of climate change on HP generation. The proposed modelling framework proves to be a flexible methodology for performing quantitative analyses of hybrid solar-hydro power systems both under historical conditions and under future climate scenarios.