Performance characteristics of the Spiky Central Receiver Air Pre-heater (SCRAP)

Abstract

Combined cycle concentrating solar power (CSP) plants provide significant potential to achieve an efficiency increase and an electricity cost reduction compared to current single-cycle plants. A combined cycle CSP system requires a receiver technology capable of effectively transferring heat from concentrated solar irradiation to a pressurized air stream in a gas turbine. The novel spiky central receiver air pre-heater (SCRAP) technology is proposed to overcome barriers experienced to date.The SCRAP receiver is a novel metallic receiver technology aimed at pre-heating an air stream to about 800 °C, either prior to a combustion chamber or alternatively prior to a cascaded secondary non-metallic receiver system, capable of achieving elevated temperatures.A ray-tracing analysis demonstrated that the flux imposed on the absorber assemblies is dependent on the heliostat size. A thermodynamic computer model was developed to investigate the performance characteristics of the absorber assemblies (spikes) of the SCRAP receiver. The model was validated against an experimental test setup. Satisfactory agreement at various air flow rates was obtained.The thermal efficiency of the spikes was investigated and used to approximate the receiver’s solar-thermal efficiency. The receiver is predicted to perform at solar-thermal efficiencies exceeding 80%. The geometric design of the receiver achieves a relatively low radiative heat loss, predicted at about 4–5%. A relatively large vulnerability to convective heat losses was identified. The pressure loss was found to be relatively low, compared to existing alternative receiver designs, with system pressure losses below 40 mbar achievable.