Power tower concentrating solar plants with thermal energy storage will play a key role in the transition to a low carbon scenario, thanks to be a dispatchable renewable energy system. The ternary MgCl2/KCl/NaCl salt appears as one of the most promising due to its lower melting point, higher heat capacity, lower cost and stability up to 800 °C. A cavity-type receiver has been selected because minimizes radiation heat loss at high working temperatures, compared to an external-type receiver, since all commercial selective coatings degrade in air.

Supercritical Brayton power cycle is chosen for the power block because it can surpass 50% efficiency, even when working in dry cooling conditions, and printed circuit heat exchangers are usually recommended due to its ability to support the high pressures. However, plugging/clogging issues arise in their small channels when using molten salts. This paper proposes a novel supercritical CO2 Bayton power cycle whose heat power is supplied through the low pressure side (over 85 bar) allowing the use of shell and tube heat exchangers, achieving a higher compactness and a lower investment. Thus, different options based on the recompression layout with intercooling and reheating have been investigated in both dry and wet cooling scenarios. Reheating is recommended for wet cooling, reaching 54.6% efficiency and an investment of 8662 $/kWe; intercooling with reheating is the best option for dry cooling, reaching 52.6% efficiency and an investment of 8742 $/kWe.

This work proposes a new particle receiver for Concentrating Solar Technology (CST) that employs air and particles as heat transfer fluid (HTF). The novel Linear Particle Solar Receiver (LPSR) is located at the ground level receiving the concentrated solar energy linearly from the top. This receiver is formed by several fluidized beds connected consecutively allowing the horizontal movement of solids and the linear absorption of solar energy. A new solar field is proposed and analyzed to redirect the concentrated solar energy towards the receiver linearly.

The optic analysis of a linear beam-down system is carried out using a ray-tracing software. Then, the performance of a linear particle solar receiver is analyzed considering target temperatures of 200 °C, 400 °C, 600 °C and 800 °C to reproduce CST integration with medium and high temperature process heat, Rankine power generation and supercritical CO2 (sCO2) cycles, respectively. The temperature of the hot streams of air and sand are calculated considering the heat losses from the receiver and the compressor parasitic consumption. The procedure to determine the optimum design is shown studying one line as a function of the target temperature. For instance, a sand mass flow of 1.75 kg/s in a receiver of 0.5 m width and a secondary reflector eccentricity of 0.8, can be heated up to 600 °C in a length of 280 m, showing a solar field efficiency of 40.25% and a receiver thermal efficiency of 80%.