Thermal modeling of a secondary concentrator integrated with an open direct-absorption molten-salt volumetric receiver in a beam-down tower system

Abstract

Abstract. An upward-facing three-dimensional secondary concentrator, herein termed Final Optical Element (FOE), is designed to be used in a beam-down tower in combination with an open volumetric direct-absorption molten-salt receiver tank acting simultaneously as a thermal energy storage system. It allows reducing thermal losses from the open receiver by decreasing its aperture area while keeping minimal spillage losses. The FOE is exposed to high solar fluxes, a part of which is absorbed by its reflector material, leading to material degradation by overheating. Consequently, the FOE may require active cooling. A thermal model of the FOE under passive cooling mechanism is proposed as a first step to evaluate its sensitivity to some design parameters. Then, it will be used to evaluate the requirements for the active cooling system. The model provides insights on the FOE thermal behavior and highlights the effectiveness of a design modification on passive cooling enhancement. First prototype tests under reduced flux and with no active cooling will be used for model adjustment.

Testing of a secondary concentrator integrated with a beam-down tower system under non-liquid cooling strategies

“…In order to estimate the passive cooling behavior of the FOE and its maximum temperature profile with no cooling enhancement measures, a simplified thermal model 9 was developed assuming extreme flux and ambient temperature conditions. The model was used as well to evaluate two non-liquid-based cooling measures.…”

A Novel Dual Receiver–Storage Design for Concentrating Solar Thermal Plants Using Beam-Down Optics

“…This unit, called CSPonD (concentrated solar power on demand demonstration), includes 280.7 m 2 of heliostats and is designed for a nominal heat input of 100 kW th with a concentration ratio of up to 600 and an optical efficiency of up to 77% [13]. In an additional stage, a 600 kWh molten salt storage tank was incorporated [13,14], with an overall thermal performance in the range of 24-28% (using an idealized Carnot cycle) [15]. A scale-up analysis predicts a LCOE of ~0.1 USD/kWh for a plant of 50 MW e [16].…”