On the selection of shape and orientation of a greenhouse for composite climates

Five most commonly used single span shapes of greenhousesviz. even-span, uneven-span, vinery, modified arch and quonset type have been selected for comparison.The length, width and height (at the center) is kept same for all the shapes. Total solar radiation input (beam, diffused and ground reflected) to each shape (through each wall, inclined surfaces and roofs) is theoreticallycomputed for east-west and north-south orientationsand compared for each month of the year at 31 N latitude. The total solar radiation available for each shape is then introduced in a developed transient thermal model to compute hourly inside room air temperaturefor the selected day of the year. Experimental validation is carried out for measured air temperature data for an even-span greenhouse (in which capsicum is grown) at Ludhiana (31 N and 77 E), Punjab, India. The predicted and measured values are in close agreement.Even-span or quonset shape in east-west orientationis the best suited for year round applications. Variationin greenhouse shape can cause change up to 3.5-5.5 C in the inside air temperature during different hours of the day at 31N latitude.