The performance of an integral greenhouse solar air-heater

Master Thesis


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University of Cape Town

The Baird-type solar collector is a solar air-heater, utilising black shade-cloth as the absorber, that is incorporated as part of the roof of a greenhouse. It is intended to be used, in conjunction with a heat storage device, to provide greenhouse heating (and cooling), and so to assist in maintaining an optimum greenhouse plant-cultivation environment. An analysis of a Baird-type integral greenhouse solar collector is presented in this thesis. This has involved designing and building a solar simulator, which was used to test the performance of a model of a greenhouse-integral solar collector. The experimental results thus derived were compared with results generated using a theoretical heat-transfer model of the solar collector and show that, on average, the theoretical model was capable of predicting the model solar collector heat-gain to within six percent of the measured values. Predictions of performance were made for various input conditions, such as high and low values of inlet-air temperature, different ground temperatures, different mass-flowrates and radiation intensities. Although subject to the input conditions, the results indicated an efficiency of solar energy collection of about 35 percent for the model greenhouse solar collector. The theoretical model was used (with appropriate modifications), to predict the performance of a "life-size" Baird-type greenhouse integral solar collector. Predictions were made for average conditions in the Cape Peninsula for the months of January and June. Assuming zero windspeed, a collector efficiency of approximately 42 percent is anticipated for most of the January day and approximately 33 percent for most of the June day.

Bibliography: leaves 76-83.