Abstract

TORCHIA-NUNEZ, J.C.; PORTA-GANDARA, M.A.  and  CERVANTES-DE GORTARI, J.G.. Steady-State Exergy Analysis of a Simple Solar Still. Ing. invest. y tecnol. [online]. 2010, vol.11, n.1, pp.25-34. ISSN 2594-0732.

This paper presents a steady-state, theoretical exergy analysis of a solar still, focused on the exergy flows in the components of the still: collector plate, brine and glass cover. The analytical approach states an energy balance for each component resulting in three coupled equations where three parameters -solar irradiance, ambient temperature and insulation thickness- are studied. The energy balances are solved to find temperatures of each component; these temperatures are used to compute energy and exergy flows. Results in the steady-state regime show that the collector transports 13% of incident radiation exergy to the heat the brine, while in the brine the evaporation exergy accounts for the 6% of total exergy. Exergy/energy ratio shows that the most efficient component is the brine reaching more than 90% for almost any value of the parameters under study, while the collector has a 23% exergy/energy ratio for a 1,000 W/m² solar energy input. The solar still is a device that uses efficiently the heating of a collector and the general discussion about its promotion should not, as it must be with almost every other solar device, be about thermodynamic limitations.

Keywords : Exergy; efficiency; solar still; irreversibilities; thermodynamics.

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