An exergy based unified test protocol for solar cookers of different geometries

It is beneficial for the consumer to have solar cookers of various varieties in terms of geometrical designs, performance and price but it is also a challenge to develop a uniform test standard for evaluating the thermal performance of the cookers irrespective of their geometrical construction. In this paper, four exergy based parameters, are proposed for solar cookers of different topological design, as their thermal performance indicators. To this end, graphs between exergy output power and temperature difference are plotted, and they resemble a parabolic curve for each design. The peak exergy (vertex of the parabola), can be accepted as a measure of devices’ fuel ratings. The ratio of the peak exergy power gained to the exergy power lost at that instant of time can be considered as the quality factor of the solar cooker. Besides, the exergy power lost is found to vary linearly with temperature difference irrespective of the topology of the device and the slope of the straight line obtained through curve fitting represents the heat loss coefficient of the cooker. The proposed parameters can lead to development of unified test protocol for solar cookers of diversified designs.

► Exergy output of various varieties of solar cookers is compared.
► Rationale behind exergy based thermal performance evaluation procedure is discussed.
► Four new thermal performance indicators for solar cookers are proposed.
► Peak exergy power and exergy temperature difference gap product are determined.
► Quality factor and heat loss coefficient are also obtained from exergy analysis.