A simple relationship between the sunlight concentration factor and the thermal conductance in a class of photothermal engines

Rocha-Martínez, J A; Navarrete-González, T D; Angulo‐Brown, F.

doi:10.1088/0022-3727/31/14/019

Cited by 2 publications

(2 citation statements)

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“…In the case of a direct steam solar thermal power plant, this resistance will manifest itself in the heat transfer coefficient associated with the boiling of water within the solar receiver pipes. Navarrete-Gonzalez et al [6,7] broached this matter and found that there appeared to be an optimal level of geometric concentration at which a solar thermal system's efficiency was maximised. What was not clear, however, was how this optimum affected real solar thermal plant designs.…”

Section: Fig 1 Mueser Enginementioning

confidence: 99%

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Optimal concentration and temperatures of solar thermal power plants

McGovern

Smith

2012

Energy Conversion and Management

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Publication informationEnergy Conversion and Management, Publisher Elsevier Item record/more information http://hdl.handle.net/10197/4904 Publisher's statementThis is the author's version of a work that was accepted for publication in Energy Conversion and Management. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Energy Conversion and Management (60, , (2012) Abstract:Using simple, finite-time, thermodynamic models of solar thermal power plants, the existence of an optimal solar receiver temperature has previously been demonstrated in literature. Scant attention has been paid, however, to the presence of an optimal level of solar concentration at which the conversion of incident sunlight to electricity (solar-to-electric efficiency) is maximized. This paper addresses that gap. The paper evaluates the impact, on the design of Rankine-cycle solar-trough and solar-tower power plants, of the existence of an optimal receiver temperature and an optimal level of solar concentration. Mathematical descriptions are derived describing the solar-to-electric efficiency of an idealized solar thermal plant in terms of its receiver temperature, ambient temperature, the receiver irradiance (radiation striking unit receiver area), solar receiver surface to working fluid conductance, condenser conductance, solar collector efficiency, convective loss coefficients and radiative loss coefficients. Using values from the literature appropriate to direct-steam and molten-salt plants, curves of optimal solar receiver temperature, and optimal solar-to-electric conversion efficiency, are generated as a function of receiver irradiance. The analysis shows that, as the thermal resistance of the solar receiver and condenser increases, the optimal receiver temperature increases whilst the optimal receiver irradiance decreases. The optimal level of receiver irradiance, for solar thermal plants employing a service fluid of molten salts, is found to occur within a range of values achievable using current solar tower technologies. The tradeoffs (in terms of solar-to-electric efficiency) involved in using molten salts rather than direct steam in the case of solar towers and solar troughs are investigated. The optimal receiver temperatures calculated with the model suggest the use of sub-critical Rankine cycles for solar trough plants, but super-critical Rankine cycles for solar tower plants, if the objective is to maximize solar-to-electric efficiency.

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Section: Fig 1 Mueser Enginementioning

confidence: 99%

“…In this section, a simplified model of a Rankine cycle solar thermal power plant is developed based on previous work [1][2][3][4][5][6][7][8]. In our analysis, we choose to treat solar irradiation as an incident heat flux, specified as a rate of heat input per unit solar collector area, s q  .…”

Section: Optimal Receiver Irradiance Of Solar Thermal Plantsmentioning

confidence: 99%