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A novel concept of a particle receiver for high-temperature solar applications was developed and evaluated in the present work. The so-called Centrifugal Particle Receiver (CentRec) uses small bauxite particles as absorber, heat transfer, and storage medium at the same time. Due to advantageous optical and thermal properties, the particles can be heated up to 1000 °C without sintering in the storage. High thermal efficiencies at high outlet temperatures are expected indicating a promising way for cost reduction in solar power tower applications. A 15kWth prototype was designed, built, and tested in order to demonstrate the feasibility and potential of the proposed concept. Extensive high flux experiments were conducted, investigating the thermal receiver performance and efficiency. For an input flux of 670 kW m−2, the target outlet temperature of 900 °C at a receiver efficiency of about 75% was successfully demonstrated.

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.

In this paper we present a study on the use of remote sensing data combined to the 3D modeling of radiative transfer (RT) and energy balance in urban canopies in the aim to improve our knowledge on anthropogenic heat fluxes in several European cities (London, Basel, Heraklion, and Toulouse). The approach is based on the forcing by the use of LandSAT8 data of a coupled radiative transfer model DART (Direct Anisotropic Radiative Transfer) (www.cesbio.upstlse.fr/dart) with an energy balance module. LandSAT8 visible remote sensing data is used to better parametrize the albedo of the urban canopy and thermal remote sensing data is used to enhance the anthropogenic component in the coupled model. This work is conducted in the frame of the H2020 project URBANFLUXES, which aim is to improve the efficiency of remote-sensing data usage for the determination of the anthropogenic heat fluxes in urban canopies [5].

Abstract An open cooling system based on metal hydrides is a promising new technology to reutilize the compression work in a hydrogen pressure tank by generating heat or cold. Our first of its kind system consists of two alternately operating plate reactors, which are filled with around 1.5 kg of Hydralloy C2 ( T i 0.98 Z r 0.02 V 0.41 F e 0.09 C r 0.05 M n 1.46 ) and coupled to a polymer electrolyte membrane fuel cell. In the present study, an extensive performance investigation for a variation of the main influencing parameters is performed: The electrical fuel cell power and the operating temperatures. Overall, it can be observed that in the entire range of various operating conditions, the fuel cell operation is not affected by the alternately operating H2 desorbing reactors. The variation of the electrical fuel cell power between 1.8 and 7.9 kW results in a maximum average cooling power of 807 W at an electrical power of 7 kW, reaching a specific cooling power of 276 W k g M H - 1 . The systems performance decreases with rising ambient temperatures (varied in the range: 24.3–42.3 °C) and decreasing cooling temperatures (varied in the range: 13–25.4 °C) due to increased thermal losses and reduced half-cycle times. Concluding the parameter variations, optimization recommendations are given and the expected performance for an improved system design is derived.

Solid sensible heat storage is an attractive option for high-temperature storage applications regarding investment and maintenance costs. Using concrete as solid storage material is most suitable, as it is easy to handle, the major aggregates are available all over the world, and there are no environmentally critical components. Long-term stability of concrete has been proven in oven experiments and through strength measurements up to 500 °C. Material parameters and storage performance have been validated in a 20-m3 test module with more than 23 months of operation between 200 °C and 400 °C and more than 370 thermal cycles. For an up-scaled concrete storage design with 1100-MWh capacity in a modular setup for a 50 MWel parabolic trough power plant of the ANDASOL-type, about 50 000 m3 of concrete is required and the investment costs are approximately 38 million euro. The simulation of the annual electricity generation of a 50 MWel parabolic trough power plant with a 1100-MWh concrete storage illustrates that such plants can operate in southern Europe delivering about 3500 full load hours annually; about 30% of this electricity would be generated by the storage system. This number will increase further, when improved operation strategies are applied. Approaches for further cost reduction using heat transfer structures with high thermal conductivity inside the concrete are analyzed, leading to a 60% reduction in the number of heat exchanger pipes required. For implementation of the structures, the storage is build up of precast concrete blocks.