Description

Concentrated Solar Power (CSP) plants can play an important role in the energy supply mix in the twenty first century. Nevertheless, the Levelized Cost of Electricity (LCoE) of CSP has not attained the level targeted except for few installations in exceptionally good locations. As of today, many ongoing research projects aiming at enhancing the efficiency of the power block and reducing the associated costs are based on supercritical CO₂-technology. However, relatively high ambient temperatures, typical in regions characterized by high solar irradiation, remain the Achilles heel of supercritical CO₂-cycles, as the efficiency of these systems drops dramatically in warm environments, where ambient temperature is close to, or higher than the critical temperature of pure CO₂ (31°C), hence not allowing to adopt condensation (Rankine) cycles with expectedly higher efficiencies. This issue stems as an intrinsic critical hurdle for the future commercialization of CSP-plants, which may be difficult to overcome by any means, with the technology currently in use or with standard supercritical CO₂-technology.

To address this limitation, this project analyses a modified working fluid whereby carbon dioxide is blended with certain additives to enable condensation at temperatures as high as 60°C whilst, at the same time, still withstanding the required peak cycle temperatures. This presents a major breakthrough in CSP-technologies as it increases the thermomechanical conversion efficiency from the current 42% to above 50%, bringing about large reductions in LCoE.

There are two main areas of research in this project: The first is the identification of the optimal additive, which would reduce the size and increase the efficiency of the power block. The second is the development of tailored heat exchanger designs, particularly for the air-cooled condenser, to operate with the innovative fluid as these are key enabling components for the proposed technology. Both actions will lead to a significant reduction of CAPEX and OPEX with respect to conventional CSP technologies.

Objectives

The project aims at developing and demonstrating an innovative power cycle based on blended CO₂ for CSP-applications, yielding higher efficiency and lower cost. The aim of the SCARABEUS project is to demonstrate that the application of supercritical CO₂ blends to CSP-plants has the potential to reduce CAPEX by 30% and OPEX by 35% with respect to state-of-the-art steam cycles, thus exceeding the reduction achievable with standard supercritical CO₂ technology.

The project demonstrate the innovative fluid and newly developed heat-exchangers at a relevant scale (300 kWth) for 300 h in a CSP-like operating environment.