Materials for photothermal solar energy conversion

Bogaerts, Walter; Lampert, Carl M.

doi:10.1007/bf00700767

Cited by 166 publications

(75 citation statements)

References 91 publications

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“…From the literature, many different coatings are available [58][59][60][61]. Most of these coatings cannot operate at the high temperatures studied in this paper.…”

Section: Radiation Heat Lossmentioning

confidence: 99%

The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

Roux¹,

Bello‐Ochende²,

Meyer³

2014

Energy Conversion and Management

122

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The first law and second law efficiencies are determined for a stainless steel closed-tube open rectangular cavity solar receiver. It is to be used in a small-scale solar thermal Brayton cycle using a micro-turbine with low compressor pressure ratios. There are many different variables at play to model the air temperature increase of the air running through such a receiver. These variables include concentrator shape, concentrator diameter, concentrator rim angle, concentrator reflectivity, concentrator optical error, solar tracking error, receiver aperture area, receiver material, effect of wind, receiver tube diameter, inlet temperature and mass flow rate through the receiver. All these variables are considered in this paper. The Brayton cycle requires very high receiver surface temperatures in order to be successful.These high temperatures, however, have many disadvantages in terms of heat loss from the receiver, especially radiation heat loss. With the help of ray-tracing software, SolTrace, and receiver modelling techniques, an optimum receiver-to-concentrator-area ratio of A' ≈ 0.0035 was found for a concentrator with 45° rim angle, 10 mrad optical error and 1° tracking error. A method to determine the temperature profile and net heat transfer rate along the length of the receiver tube is presented. Receiver efficiencies are shown in terms of mass flow rate, receiver tube diameter, pressure drop, maximum receiver surface temperature and inlet temperature of the working fluid. For a 4.8 m diameter parabolic dish, the larger the receiver tube diameter and the smaller the mass flow rate through the receiver, the higher the receiver surface temperature and the less efficient the collector becomes. However, the smaller the receiver tube diameter, the higher the pressure drop through the tube and the smaller the second law efficiency. It was found that the 2 receiver with larger tube diameter would perform better in a solar thermal Brayton cycle. An overall solar-to-heat efficiency of between 45% and 70% is attainable for the solar collector using the open-cavity receiver.Keywords: solar, receiver, cavity, tracking, Brayton, efficiency 1.Introduction and background The solar thermal Brayton cycleThe closed Brayton cycle was developed in the 1930s for power applications [ The open Brayton cycle uses air as working fluid, which makes this cycle very attractive for use in water-scarcecountries. The open and direct solar thermal Brayton cycle is shown in Fig. 1 [2]. The parabolic dish concentrator is used to reflect and concentrate the sun's rays onto the receiver aperture so that the solar heat can be absorbed by the inner walls of the receiver. The heat is then transferred to the working fluid (air). The compressor increases the air pressure before the air is heated in the receiver. The compressed and heated air expands in the turbine, which produces rotational power for the compressor and the electric load.In the recuperator, hot exhaust air preheats the colder air before it enters the receiver. For the so...

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“…From the literature, many different coatings are available [58][59][60][61]. Most of these coatings cannot operate at the high temperatures studied in this paper.…”

Section: Radiation Heat Lossmentioning

confidence: 99%

The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

Roux¹,

Bello‐Ochende²,

Meyer³

2014

Energy Conversion and Management

122

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“…Only with the advent of new studies about Cr 3þ baths, since the beginning of 2000's, the electrodeposition processes have found new interest in mass production of components for thermal solar plants. To obtain a good coating by black chrome, a preliminary deposition of a nickel layer on the substrate is needed to ensure a better chrome adherence to the surface [19] and an improved wear and corrosion resistance [20]. Moreover this creates an "absorber/reflector tandem" having both the high solar absorbance of the black exterior deposit and the low thermal emittance of the metallic inner coating [20].…”

Section: Introductionmentioning

confidence: 99%

“…To obtain a good coating by black chrome, a preliminary deposition of a nickel layer on the substrate is needed to ensure a better chrome adherence to the surface [19] and an improved wear and corrosion resistance [20]. Moreover this creates an "absorber/reflector tandem" having both the high solar absorbance of the black exterior deposit and the low thermal emittance of the metallic inner coating [20]. Recently we investigated morphological and optical properties of nickel substrates [21].…”

Section: Introductionmentioning

confidence: 99%

Structural and optical properties of copper-coated substrates for solar thermal absorbers

Pratesi

Lucia

Meucci

et al. 2016

Superlattices and Microstructures

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a b s t r a c tSpectral selectivity, i.e. merging a high absorbance at sunlight wavelengths to a low emittance at the wavelengths of thermal spectrum, is a key characteristics for materials to be used for solar thermal receivers. It is known that spectrally selective absorbers can raise the receiver efficiency for all solar thermal technologies. Tubular sunlight receivers for parabolic trough collector (PTC) systems can be improved by the use of spectrally selective coatings. Their absorbance is increased by deposing black films, while the thermal emittance is minimized by the use of properly-prepared substrates. In this work we describe the intermediate step in the fabrication of black-chrome coated solar absorbers, namely the fabrication and characterization of copper coatings on previously nickel-plated stainless steel substrates. We investigate the copper surface features and optical properties, correlating them to the coating thickness and to the deposition process, in the perspective to assess optimal conditions for solar absorber applications.

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“…These surfaces are typically black or spectrally selective such that high absorptivity in the solar spectrum is coupled with low emissivity in the infrared (Bogaerts and Lampert, 1983). Although surface-based receivers are efficient at solar to thermal conversion, they are not well suited for transferring heat to a carrier fluid.…”

Section: Introductionmentioning

confidence: 99%

Optimization of nanofluid volumetric receivers for solar thermal energy conversion

2012

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Improvements in solar-to-thermal energy conversion will accelerate the development of efficient concentrated solar power systems. Nanofluid volumetric receivers, where nanoparticles in a liquid medium directly absorb solar radiation, promise increased performance over surface receivers by minimizing temperature differences between the absorber and the fluid, which consequently reduces emissive losses. We present a combined modeling and experimental study to optimize the efficiency of liquid-based solar receivers seeded with carbon-coated absorbing nanoparticles. A one-dimensional transient heat transfer model was developed to investigate the effect of solar concentration, nanofluid height, and optical thickness on receiver performance. Simultaneously, we experimentally investigated a cylindrical nanofluid volumetric receiver, and showed good agreement with the model for varying optical thicknesses of the nanofluid. Based on the model, the efficiency of nanofluid volumetric receivers increases with increasing solar concentration and nanofluid height. The total receiver-side efficiencies are predicted to exceed 35% when nanofluid volumetric receivers are coupled to a power cycle and optimized with respect to the optical thickness and solar exposure time. This work provides insights as to how nanofluids can be best utilized as volumetric receivers in solar applications, such as receivers with integrated storage for beam-down CSP and future high concentration solar thermal energy conversion systems.

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Materials for photothermal solar energy conversion

Cited by 166 publications

References 91 publications

The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

Structural and optical properties of copper-coated substrates for solar thermal absorbers

Optimization of nanofluid volumetric receivers for solar thermal energy conversion

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