CAPTure project has designed an alternative power plant layout (Figure 2) that complements the first designed plant configuration (Figure 1). This plant configuration is based on a multi-tower decoupled advanced solar combined cycle approach that not only increases cycle efficiencies but also avoids frequent transients and inefficient partial loads, thus maximizing overall efficiency, reliability as well as dispatchability, all of which are important factors directly related to cost competitiveness on the power market.
The innovative solar receiver will be an open volumetric receiver allowing operating temperatures beyond 1000 °C, providing the absorbed solar heat to the pressurized air circuit of the Brayton cycle via a network of fixed bed regenerative heat exchangers working in alternating modes (non-pressurized heating period, pressurized cooling period).
Figure 1: The CAPTure plant configuration is based on a multi-tower decoupled advanced solar combined cycle approach
Figure 2: Alternative power plant layout: Solar powered combined cycle scheme with open volumetric air receiver and high-temperature TES upstream the gas turbine – The low-temperature TES enables regenerative use of return air heat.
Figure 2 shows a scheme of an alternative plant layout that is also analysed in WP1. In contrast to Figure 1, here the thermal energy storage system is placed upstream the gas turbine, allowing dispatchable operation of the combined cycle. This alternative solar powered combined cycle plant applies the same open volumetric air receiver technology, a high-temperature thermocline air/ceramic TES and the CAPTure regenerative system coupling the high-temperature atmospheric air stream with the pressurized air loop of the topping Brayton cycle. It must be emphasized that the temperature level of the “cold” return air stream leaving the air/air heat exchange system, is a function of compressor outlet temperature (i.e. compressor pressure ratio and ambient temperature) and the exit temperature of the first turbine stage, in the case of reheat. The resulting air-return temperature level is too high for efficient blower operation and the recirculation to the high-temperature TES or the receiver is thus not feasible. A low-temperature air/rock thermocline TES is thus proposed in order to reuse the return air heat in regenerative manner. In order to keep air transport parasitic power consumption acceptable, the operating temperature of the blower should be kept at ambient temperature level.
The global objective of this project is to increase concentrated solar power plant efficiencies and reduce levelised cost of electricity (LCOE) by developing the key components of an innovative plant configuration. This plant configuration is based on a multi-tower decoupled advanced solar combined cycle approach (see Figure 1 and Figure 2) that not only increases cycle efficiencies but also avoids frequent transients and inefficient partial loads, maximizing overall efficiency, reliability as well as dispatchability.