LOW-COST RENEWABLE ENERGY DEVICES: To Boost Rural Entrepreneurship
The rural people of our country mainly depend on agriculture as India is an agrarian economy. Thus, there exists a huge mass of unemployed youth who are facing constraints to continue their existence. Rural youth can find self-employment opportunity by fabricating low-cost renewable energy technologies and energy efficient devices. It is strongly believed that, if mass production of these devices is taken up, it would create an atmosphere of sustainable development in India.
A solar dryer is used as a heat source for drying crops, such as corn, fruit, or vegetable.
Solar cabinet dryer
The solar cabinet dryer (Figure 1 and Picture 1) consists of a wooden or any insulated material box of length three times of its width, insulated at its base and at the sides and covered with a transparent roof. The inside surfaces of the box are coated with black paint and the product to be dried is kept in the trays made of wire mesh bottom. These loaded trays are kept through an openable door provided on the rear side of the dryer. Ventilation holes are made in the bottom through which fresh air from outside is sucked automatically. Holes are also provided on the upper sides of the dryer through which moist warm air escapes.
- Dimensions of demonstrative model: 2.5 ft x 1 ft
- Raw materials required for fabrication: Plywood, aluminium sheet, UV-resistant polythene sheet, black dull paint, etc.
- Machinery used for fabrication: Hand saw, portable drilling machine, hammer, screwdriver, pliers, measuring tape, etc.
- Cost of fabrication of demonstrative model: Rs 600.
Solar rack-type dryer
The solar rack-type dryer (Picture 2) consists of a wooden box insulated at its base and at the sides and covered with one layer of UVresistant transparent polythene sheet on the front side. The inside surfaces of the box are coated with dull black paint and the product to be dried is kept in the trays made of wire mesh bottom. These loaded trays are placed sidewise opening of the dryer box. Ventilation holes are made at the bottom of the dryer box through which fresh outside air is sucked automatically. Holes are also provided on the upper sides of the dryer through which moist warm air escapes.
- South facing frontal area: 3 ft x 3 ft
- Depth of the wooden box: 10 inches
- Ventilation holes: At the bottom and top side of the dryer box
- Number of perforated trays: 2 nos.
- Tray area: 3 ft x 1 ft
- Placement of trays: Sidewise
- Inclination of dryer box: 45° with the base
- Dryer box: 12 mm thick wooden box with dull black aluminium sheet layer inside
- Cover: Transparent polythene sheet
- Cost of fabrication of demonstrative model: Rs 1,000.
Solar Distillation Plant to Produce Distilled Water for Automotive Battery
Impure water, in a glass-covered enclosure with a black bottom (to increase the absorption of solar radiation) is heated by solar rays and which evaporates. The vapour condenses on the underside of the glass cover and is collected as pure water through flow channels provided at the lower edge of the cover. The glass cover has a dual function, it helps retain heat inside the solar still (Figure 2 and Picture 3) by letting in short wave solar radiations and reflecting back long wave heat radiations re-radiated from the surface of the still and its underside acts as a cool surface (glass cover is at a lower temperature because it is in contact with the ambient air) for water vapour to condense. Considering the capacity to produce 2 l of distilled water/m2/ day, production capacity of single unit of this particular plant will be approximately 0.8 l of distilled water. To produce 20 l of distilled water per day 25 units are required, estimated cost of which is approximately Rs 80,000.
- MS sheets are to be cut in the size of 122 cm x 122 cm to fabricate each basin.
- Ends of each sheet are to be folded 90° upward to form the basin.
- 10° slope is to be maintained at the top open side having a maximum 30 cm height at highest end.
- Top ends of each basin walls are folded inside to provide 2.5 cm wide seating for glass cover.
- Asphalt sheet is to be used as gasket in between seating and 3 mm thick transparent plain window glass to arrest the leakage.
- Asphalt gasket is to be further placed at the top of the glass cover at all sides and glass cover is then to be firmly held with seating by lightweight MS angles screwed with the sidewalls of the basin.
- A V-shaped aluminium/stainless steel channel is to be fixed at sloped edge to collect condensate from where distilled water can be taken out through outlet connection.
- Suitable inlet connection is to be arranged at upside of basin to fill impure water time to time and another pipe is used to control the level of impure water and to flush the basin.
- Interior of the basins are to be painted dull black by automobile muffler paint to absorb solar radiation.
Mr Sankha Subhra Datta is a Senior Section Engineer (Mechanical) in the Diesel Locomotive Shed, N F Railway, Siliguri Junction, West Bengal, India. E-mail: subhradatta611@gmail. com.