Levelized cost of electricity evaluation of liquid sodium receiver designs through a thermal performance, mechanical reliability, and pressure drop analysis

The receiver in a concentrated solar power (CSP) tower system accounts for a considerable proportion of plant capital costs, and its role in converting radiant solar energy into thermal energy affects the cost of generated electricity. It is imperative to utilize a receiver design that has a high thermal efficiency, excellent mechanical integrity, minimal pressure drop, and low cost in order to maximize the potential of the CSP system. In the present work, thermal, mechanical, and hydraulic models are presented for a liquid tubular billboard receiver in a representative CSP plant. A liquid sodium heat transfer fluid as well as a number of receiver configurations of heat transfer area, tube diameter, and tube material have been analysed. The thermal analysis determines tube surface temperatures for an incident heat flux, thereby allowing for the calculation of thermal losses and efficiency. The mechanical analysis is carried out to establish creep deformation and fatigue damage that the receiver may undergo through a life service. The hydraulic analysis is concerned with calculating the required pumping power for each configuration. Results show that thermal efficiency increases for a decreasing heat transfer area, however reducing receiver area comes at the penalty of increasing tube surface temperatures and thermal stresses. The selection of tube diameter is critical, with small diameters yielding the greatest thermal efficiency and mechanical life, however the increased pressure drop reduces the overall plant efficiency due to a necessary increase in pumping power. The optimum receiver configuration is established by finding an appropriate trade-off between thermal performance, service life, pressure drop, and material costs, by using the levelized cost of electricity (LCOE) as the objective function. The analysis highlights necessary trade-offs required to optimise the design of a solar receiver.