Optimum aperture size and operating temperature of a solar cavity-receiver

Steinfeld, Aldo; Schubnell, Markus

doi:10.1016/0038-092x(93)90004-8

Cited by 230 publications

(70 citation statements)

References 7 publications

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“…(1)) so having high solar absorptance becomes much more important to the receiver efficiency. Therefore, typically high optical concentration is used in combination with a black absorber or a blackbody cavity to efficiently operate at higher receiver temperatures (Prakash et al, 2009;Steinfeld and Schubnell, 1993). However, using high optical concentration ratios introduces complications such as large temperature gradients and complex heat exchangers required to handle a high heat flux.…”

Section: Introductionmentioning

confidence: 99%

Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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Abstract:A principal loss mechanism for solar receivers in solar-thermal systems is radiation from the absorbing surface. This loss can be reduced by using the concept of directional selectivity in which radiation is suppressed at angles larger than the incident angle of the sunlight striking the absorber. Directional selectivity can achieve efficiencies similar to high solar concentration, without the drawbacks associated with large heat fluxes. A specularly reflective hemispherical cavity placed over the absorber can reflect emitted radiation back to the absorber, effectively suppressing emission losses. An aperture in the cavity will still allow sunlight to reach the absorber surface when used with point focus concentrating systems. In this paper the reduction in radiative losses through the use of a hemispherical cavity is predicted using ray tracing simulations, and the effects of cavity size and absorber alignment are investigated. Simulated results are validated with proof of concept experiments that show reductions in radiative losses of more than 75% from a near blackbody absorber surface. The demonstrated cavity system is shown to be capable of achieving receiver efficiencies comparable to idealized spectrally selective absorbers across a wide range of operating temperatures. Highlights:-A specularly reflective cavity placed over a solar absorber reduces radiative losses -Cavity performance is sensitive to cavity size and cavity-absorber alignment -Radiative loss reduction validated with proof of concept experiments -Losses from near blackbody absorber reduced by over 75% -Receiver efficiency shown to be comparable to idealized wavelength selective absorber

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Section: Introductionmentioning

confidence: 99%

Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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“…Consequently, the equipment faces the trade-off between the maximum energy that can be absorbed by the cavity-receiver and the energy that is irradiated back through the aperture. Depending on the solar flux concentration, the subsequent optimum temperatures vary between 1100 and 1800 K [56]. More detailed thermodynamic evaluations of solar thermochemical processes have been reviewed elsewhere [10,54,57,58].…”

Section: Introductionmentioning

confidence: 99%

Functioning devices for solar to fuel conversion

Mul¹,

Schacht²,

Swaaij³

et al. 2012

Chemical Engineering and Processing: Process Intensification

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a b s t r a c tThis paper provides a perspective on the technologies capable of converting solar energy, CO 2 and H 2 O into an easy to use fuel. The paper addresses bio-based approaches, but mainly focuses on (i) the combination of photovoltaic (PV) devices and electrocatalysis, (ii) single unit operation by photocatalytic conversion, and (iii) solar thermal conversion. Each option is described in a general manner, including a brief evaluation of the advantages and disadvantages. Also suggestions for future research endeavours are given. Based on the used literature data, for electrocatalytic and photocatalytic technologies, dramatic improvements should be made in material optimization, as well as reactor design and operation. Large efficiency gains are necessary to enable use of these technologies in practice. Solar thermal conversion is more mature, and requires specific optimization in processing, as will be discussed.

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“…Hence, it seems that the former effect is lower that the latter. Also note that we only consider the optical phenomena from sunlight so including other phenomena accounting for other energy loss mechanisms could yield in an effectively optimal aperture size, see [13]. Finally, we vary the cavity diameter.…”

Section: Resultsmentioning

confidence: 99%

Radiation Performance of a Cavity Receiver for a Parabolic Dish Solar Concentrator System

López¹,

Arenas²,

Baños³

2024

RE&PQJ

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Abstract. The radiation performance of a modified cavity receiver for a low-cost concentrating solar power plant is studied. The optical phenomenon taking place is modelled by using a ray tracing technique based on a finite element approach. This design is also compared to a flat receiver. Corrections for sunlight and optical errors of the parabolic dish are included. Its efficiency is analysed by varying some geometrical parameters of the receiver, maximizing the total power absorbed. It is found that the flux density on the cavity walls is less than on the flat receiver walls, hence decreasing heat losses. Also, in order to reach a maximum radiation performance the receiver is to be placed closer to the concentrator from the focal position. However, the aperture does not improve notably its efficiency, although it has an important role in the convection heat losses as shown in previous works. Finally by varying the cavity diameter it is possible to improve the efficiency when it is well adjusted to the radiation performance of the concentrator on the focal point.

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Optimum aperture size and operating temperature of a solar cavity-receiver

Cited by 230 publications

References 7 publications

Optical cavity for improved performance of solar receivers in solar-thermal systems

Optical cavity for improved performance of solar receivers in solar-thermal systems

Functioning devices for solar to fuel conversion

Radiation Performance of a Cavity Receiver for a Parabolic Dish Solar Concentrator System

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