Proposal and performance analysis of a central receiver with helical absorber for small-scale concentrating solar thermal applications

Small-scale central receiver concentrating solar power (CSP) plants have recently gained attention due to their potential for reduced construction times and lower costs. This study proposes a cavity receiver with helical absorber for a 1 MWth central receiver CSP plant. Such a receiver configuration has not been proposed or investigated for central receiver CSP systems. The proposed design includes a helical absorber enclosed within a cubic cavity receiver and is evaluated for three absorber tube outer diameters, with the feasible diameter range constrained by the maximum allowable flow velocity at the lower limit and the maximum permissible film temperature at the upper limit. A radial-staggered, north-oriented heliostat field is modelled to predict the receiver surface heat-flux distribution using Monte Carlo ray-tracing, accounting for heliostat geometry, optical errors, and variations in solar position. The opto-thermal simulation of the heliostat-receiver system results in an optimised configuration consisting of 985 heliostats and a receiver tilt angle of 30 ∘ . The peak heat flux observed on the absorber surface is around 500 kW/ m 2 . The thermo-hydraulic model of the receiver is validated against established correlations, showing deviations of less than 5% for the Nusselt number and less than 9% for the friction factor. The results indicate that the maximum receiver efficiency is achieved at a non-dimensional pitch of about 2. A sensitivity analysis over different solar incidence angles confirms that the optimal non-dimensional pitch is largely non-sensitive to sun position. Thus, the proposed receiver offers a compact and reliable solution for small-scale central receiver CSP systems.