Three crucial aspects still to be overcome to achieve commercial competitiveness of the solar thermochemical production of hydrogen and carbon monoxide are recuperating the heat from the solid phase, achieving continuous or on-demand production beyond the hours of sunshine, and scaling to commercial plant sizes. To tackle all three aspects, we propose a moving brick receiver–reactor (MBR2) design with a solid–solid heat exchanger. The MBR2 consists of porous bricks that are reversibly mounted on a high temperature transport mechanism, a receiver–reactor where the bricks are reduced by passing through the concentrated solar radiation, a solid–solid heat exchanger under partial vacuum in which the reduced bricks transfer heat to the oxidized bricks, a first storage for the reduced bricks, an oxidation reactor, and a second storage for the oxidized bricks. The bricks may be made of any nonvolatile redox material suitable for a thermochemical two-step (TS) water splitting (WS) or carbon dioxide splitting (CDS) cycle. A first thermodynamic analysis shows that the MBR2 may be able to achieve solar-to-chemical conversion efficiencies of approximately 0.25. Additionally, we identify the desired operating conditions and show that the heat exchanger efficiency has to be higher than the fraction of recombination in order to increase the conversion efficiency.

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We investigated the forced convective heat loss from a model of a multi-MW cavity receiver of a concentrated solar power (CSP) tower system in a high-pressure wind tunnel. Measurements of 5 geometrical configurations of this model are reported in this contribution. The experiment covered a Reynolds number range of between 2 ⋅ 10 6 and 8 ⋅ 10 6 , based on the external flow field. The results show that the maximum forced convective heat loss for all configurations occurs when the wind blows from frontal directions of between 60° and 80° relative to the tower symmetry plane. We found that the peak location does not vary for different inclinations, but does vary for different apertures. Also, the results show that the direction of the wind causes the forced convective heat loss to vary with a factor of up to 6.3. Last but not least, we augmented the interpretation of our heat loss measurements with images produced with a Background-oriented Schlieren Imaging (BOS) setup.

This paper investigates a stowing strategy of a heliostat field based on wind speed and direction, in terms of the potential benefit of additional energy collection through the partial stowing of heliostats within an azimuth angle range with reduced operating wind loads. Correlations of one-minute wind speed and DNI at a heliostat field site with the operating wind loads, based on the azimuth-elevation tracking angles of individual heliostats, were used to assess the increased operating time and collected thermal energy by the field. The results show that more than 23% of heliostats in the sector of the field with operating wind loads that are smaller than 50% of the stow loads can continue to operate during a high-wind period (e.g. 10 m/s). Adopting a stow strategy based on wind direction can increase the annual operating time of the heliostat field by 6% with increasing stow design wind speed from 6 m/s to 12 m/s. Furthermore, the stowing strategy based on wind direction to allow heliostats to continue to operate at wind speeds exceeding 10 m/s can achieve an additional 280 MWh of thermal energy collected by the heliostat field operation during time periods that would conventionally stow the entire field with 24 GWh of annual thermal energy captured.