Design of a 2 MW Molten Salt Driven Supercritical CO2 Cycle and Turbomachinery for the SOLARSCO2OL Demonstration Project

Abstract

Supercritical CO2 (sCO2) power cycles have been identified as technology enablers for increasing the cost-competitiveness of Concentrating Solar Power (CSP) plants. Compared to steam cycles, sCO2 cycles have the advantage of allowing higher inlet turbine temperatures, while also deploying turbomachinery that can be a ten-fold more compact. Ongoing research in CSP focuses mainly in developing new receiver and storage concepts able to withstand such required higher temperatures, alongside new heat exchangers that enable coupling to a sCO2 cycle. Meanwhile, advancements in sCO2 turbomachinery have taken place in research projects aimed at investigating the technical feasibility of the cycle, including the optimized design of its individual components and new cycle configurations. Among these, only few focus in demonstrating a full-integrated system, including cycle control and dynamics, and only two worldwide have started plans for MW-scale pilots, none of them in Europe. The EU-funded SOLARSCO2OL project aims at demonstrating a first-of-a-kind 2 MW gross simple-recuperated sCO2 Brayton cycle driven by heat provided by molten salts similar to those deployed in commercial CSP plants, which are able to operate at temperatures of up to 580°C. This paper introduces the project objectives and implementation plan, to then focus primarily on the results derived from the first year in specific relation to the conceptual design of each of 2 MW scale power cycle and its key components, including also the proposed integration and operational regimes, expected thermodynamic performance at nominal point, and up-scaling considerations.

Dynamics and control implementation of a supercritical CO2 simple recuperated cycle

“…The SOLARSCO2OL [11] Horizon2020 European project aims at the installation and demonstration of a first-of-a-kind MW-scale sCO2 plant coupled with CSP in Europe. The sCO2 demo plant will be installed at the premises of the University of Evora and coupled with a pre-existing CSP plant using molten salts (MS) as heat transfer fluid.…”

“…This solution has a cycle efficiency of 21.3%. However, the study by Guedez et al [11] demonstrated that an upscaled version of this concept could reach an efficiency higher than 31%, and adding recompression to the plant could lead to almost 50%.…”

Untapping Industrial Flexibility via Waste Heat-Driven Pumped Thermal Energy Storage Systems

“…sCO 2 could make this possible via WH P2H2P solutions exploiting sCO 2 HPs and power cycles. Based on previous thermo-economic analysis of advanced sCO 2 power cycles [35] and thermal energy storage for industries [36], in this paper an innovative layout and concept is proposed, aiming at valorizing industrial WH and achieving attractive round-trip efficiency (RTE).…”

“…In this case, the above presented PTES cycle was studied starting from an analysis of the discharging cycle with a maximum pressure limit of 250 bar and a TES with a temperature of 450 • C (HITEC XL as the TES media). This value was determined by the authors based on their previous study [35] considering technological factors to ensure manageable compression ratios and the use of pressurized HEXs among other considerations. Additionally, in accordance with the assumptions made, a maximum CO 2 temperature of 440 • C and a typical compressor inlet temperature of 35 • C were selected to ensure stable compressor operation.…”

“…To capture the behavior of the recuperated layout, two values of recuperator effectiveness (60% and 80%) were analyzed. From these values, an optimal minimum pressure of 83 bar was selected (Figure 6), ensuring a maximum power output while also guaranteeing proper compressor operation based on the authors' previous experience [35]. This pressure value falls within the aforementioned range.…”