The state-of-the-art CSP system, usually known as second generation, is the molten-salt solar tower, which uses the so-called “solar salt” as heat transfer fluid (HTF) at temperatures up to approx. 570 °C. EU SET Plan and agendas target significant cost reductions, coupled with the new development of HTFs, storage technologies and power systems able to reach thermal efficiencies higher than 50%. Evolving from 570 °C to higher temperatures, however, will require a new HTF, owing to traditional solar salt degradation at around 600 °C. Furthermore, advanced power cycles more flexible and able to operate at higher temperatures, and with higher efficiencies, must be used to achieve the LCOE objective. Each technology shift (e.g. HTF, TES, and power block) will have consequences on the CSP plant, with high risk for developers and financiers. Therefore, a step-wise approach where key sub-systems and components of the novel system are individually developed, optimized and tested prior to their full integration is of utmost necessity to push new innovations in CSP (as also suggested by Turchi et al.4). Such approach allows assessing technologies under controlled environments where external boundary conditions can be emulated (e.g. weather), and where components can be optimized gradually by progressively testing these at more challenging operating conditions (e.g. temperature and pressure) and under a number of cycles, while simultaneously allowing for data to simulate and evaluate integration and control aspects. Financing high-risk technologies is highly challenging, and progressing towards the EU SET goals in steps that the CSP industry members can support and implement is essential for the health of the industry and the commercial viability of newly developed technologies.
SHARP-sCO2 hereby proposes a step-wise approach towards a more cost-efficient and flexible generation of hybrid CSP-PV plants leveraging on existing industrial/R&D partners’ scientific and commercial know-how. Four main critical innovations are investigated via enabling technologies tested at lab scale (TRL5 - on-sun testing in the case of solar receiver) to enhance the performance and further reduce CSP plants LCOE in the near term:
i) the promotion of air as a suitable HTF for massive implementation of CSP leveraging upon its availability and cost (free), safety, stability and capacity to allow more dynamic and flexible integrated plants.
ii) the promotion of sCO2 driven power cycles to replace steam Rankine ones;
iii) the hybridization of CSP cycles with PV via the integration of EHs;
iv) the promotion of packed bed solid media TES exploiting low-cost and more sustainable materials (such as waste from industrial processes and recycled media) when compared against molten salts.
