Abstract The integration of massive renewable energy sources (RES) into electric grids poses challenges (from a grid management, but also from an economic point of view to make investments in renewable power plants more viable) that only storages can tackle. Particularly looking at issues brought by “duck curves” that are appearing more and more in worldwide electric markets (the possibility to accept large amount of Photovoltaic and Wind Energy production and to guarantee proper power ramps during the latest hours of the day) there is the need to develop large scale energy storage, able to provide large amount of power capacity in a short time horizon. In this framework, Pumped Thermal Energy Storage (PTES) is an emerging technology thanks to many positive features, including geographical and raw materials independence, long lifetime, fast reaction, possibility to offer grid services thanks to rotating machines and peculiar sector-coupling capabilities, particularly looking at Thermally Integrated PTES (TI-PTES) solutions, that can enable the valorization of waste heat and thermal RES, towards higher performances of the storage, thus enabling to enlarge electric market favourable operating conditions for the storage itself. The variability of such thermal sources to be integrated in the TI-PTES as well as the volatility and variability of electric markets, pose challenges to this type of storage systems once managing and dispatching them, as they have to often operate in off-design and part load conditions. Following the results about off-design performances presented in previous authors’ research activities and creating specific performance curves for the charging and discharging cycles respectively, this paper aims then to evaluate potential dispatchment of the proposed sCO2 TI-PTES (integrating in its performance off-design performance features presented in the previous article), performed through a Mixed Integer Linear Programming approach, in different EU electric markets aiming to minimize the operational cost computed over a one year horizon and maximizing the storage revenues on the electric market. The results highlight that the implementation of a part-load performance curve has an impact more than on the different dispatchment strategy that the optimizer calculates, on the overall economic evaluation thus showing the importance of integrating not-constant COP/η values once evaluating the charging/discharging profile of the storage to make the analysis more reliable. The study also shows that the proposed TI-PTES technology is attainable only in markets with very high volatility that could offer to the storage system relevant annual revenues able to guarantee annual positive cash flow along the project lifetime, thus highlighting the need of supporting measures/remunerations and incentive schemes (e.g. on installed capacity via capacity reserve schemes) for Long Duration Energy Storages as well as the importance for this type of storages based on rotating machines to participate to additional grid support services (e.g. frequency regulation), whose forecast and related storage dispatchment is more complicated to be modelled.
Barberis et al. (Mon,) studied this question.