Last updated: 28 June 2017
Sri. Sankha Subhra Datta of India designed a new concept for box-type solar cooker in 2002. The key feature of the cooker is that it's designed to tilt towards the sun so that direct radiation is perpendicularly accessible to increase solar irradiance on the cooker face. Two foldable mirror reflectors are conveniently attached at both longer sides of the cooker at an angle of 115 degree with cooker face to boost up the energy collection. The cooker allows the user to cook more meals as the cooker still works when the sun is somewhat low in the sky.
During use, the cooker should be placed facing sun while keeping longer side vertically inclined position. This inclination can easily be changed up to 45 degree with respect to the ground by the adjustable stand attached at the backside of the cooker box. If the inclination is more than 45 degree, the cooker may be turned over in front for the weight of heavy glass reflectors and also for the rotation of line of action of the cooker box weight towards front. The adjustable stand is rectangular in shape exactly like the back support of old pattern canvas easy chair. Standpipes are made of lightweight MS round pipe. The cooker's inclination can be varied by changing the relative position of two rectangular support frames with respect to each other and thereafter held fixed by the help of slots formed by series of long studs.
During reorientation of the cooker, apart from changing of inclination of cooker box, the whole cooker can be rotated in the ground at desire position by the help of caster wheels attached to the bottom but the position of reflectors remain unchanged throughout the working period.
Four black cooking pots, each 1.25 liters, can be placed side by side at the longer side of the cooker on cooking trays. Each cooking tray is suspended from two pivots fixed in sidewalls of the inner box through MS strips. Length of these strips is equal to the cooking pot height. The cooking pots maintain their horizontal positions when changing their inclination due to their own weight.
Design features of the cooker are similar to conventional box type cooker. The shape of the cooker box is however different from a common type. The width and depth of the present cooker are nearly same and the length is about three times of its width. The cooker box length, width and depth are 860mm, 300mm and 260mm respectively. The outer box is made of 1mm thick GI sheet; inner box is fabricated by 0.5mm thick aluminium sheet. 50mm thick layer of glass wool is applied for insulation. Two panes of 3mm thick plain glass are used as top cover. The frame of the glass cover is hinged with cooker box. The pot is to be placed inside of oven by opening of glass cover. Cost of the cooker is Rs.2000 approximately.
- December 2011: Sankha reports that he began teaching solar cooking in 2011.
- April 2007: Sankha Subhra Datta has designed a solar box cooker that is suspended at two points within a support frame, allowing for rotation of the entire cooker around a horizontal axis from 5 to 70 degrees with respect to the ground. The cooker can therefore maintain a nearly 90-degree angle to the light as the sun's position in the sky changes. The cooker is rotated around a horizontal axis by repositioning a bar that is attached to the lower front corners of the box between any of 14 slots spread across the base of the frame. Datta says this system has advantages over solar box cookers with tilt-adjusting rear legs — a greater range of rotation can be achieved, and the cook can rotate the unit smoothly without having to lift its entire weight and risk food spillage. Another design feature that helps to prevent food spills is the weighted, rotating cooking tray that keeps the pot horizontal at all times. Regardless of cooker rotation, the pot is always at the center of the cooker because the tray rotates on the horizontal axis of the pot. "This tray holding arrangement is designed for proper utilization of top and bottom reflectors at every inclination … which is not possible in simply suspended tray arrangements [because] shifting of pot location from the central position of the inner box due to the rotation of pot around pivots," Datta says. The cooker frame sits on casters for easy rotation around the vertical axis. The outer box is constructed of galvanized iron and the inner box is aluminum, with glass wool insulation in between. The glazing is double-paned glass with a two-centimeter air gap.
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