This article throws light upon the seven important types of solar gadgets: 1. Solar Dryers 2. Solar Cooker 3. Solar Water Heater 4. Solar Lantern 5. Solar Home Lighting System 6. Solar Street Light 7. Solar Water Pump
Type # 1. Solar Dryers:
Solar dryer is required for drying crops, vegetables and fruits. While drying these products in the direct sunlight, the birds, insecticides and dust will spoil these products. The colour of the vegetables and fruits also changes and nutritious ingredients also get spoiled when dried in open sunshine.
Solar dryer is made up of hot (wooden) box. On one side of the dryer, an insulated door is provided for loading and unloading the perforated trays. For air flow, holes are provided on the bottom and in the back side near the top of the dryer. The interior of the dryer is painted with dull black paint for absorption of solar radiation.
A transparent window glass sheet is fixed as glazing on the front of the hot box for solar energy interception. The hot box is supported on the base frame mounted on castor wheels for easy mobility of dryer. The perforated trays are arranged at different levels, one above the other inside the hot box. The product to be dried is placed in these perforated trays.
Solar dryers are of two types:
(i) Domestic Solar Dryer:
Domestic solar dryer is small sized natural circulation solar dryer. Most of the products that are used in powder form in domestic kitchen, e.g. chilies, garlic, ginger, mango powder, coriander, onion, fenugreek leaves etc. are dried in this dryer. It is capable of drying about 2-3 kg of fresh product in 2-3 days. Its photograph is shown in Figure 4.1.
(ii) Multi Product Solar Dryer:
For drying agricultural products, drying air temperature should be below its maximum allowable temperature because temperature above this causes quality deterioration of dried product. In multi-product solar dryer, drying air temperature is maintained below maximum permissible temperature limit of drying product. This solar dryer has capacity to dry 20-30 kg of agricultural products per day. The photograph of this solar dryer is shown in Figure 4.2.
Type # 2. Solar Cooker:
Solar energy is one such source which can save 20% to 50% conventional fuels used for cooking. A solar cooker is a device in which cooking of the food is done by using solar energy. Solar energy is collected in the form of heat by using reflectors/lenses or insulated boxes and the heat thus collected is used for cooking.
A solar cooker consists of an insulated box with a transparent window through which sunshine enters the box. With the use of these reflectors, it becomes necessary to make a few adjustments of the cooker towards the sun. Chapatti making and frying cannot be done in the solar cookers. The different types of solar cookers have been shown in Figures 4.3 and 4.4.
Method of cooking in solar cookers:
(i) Setup the solar cooker in the sun so that it starts getting pre-heated before the ingredients of the food stuffs are placed in it.
(ii) Put the ingredients of the food in the containers and add just sufficient quantity of water (if water is required e.g. for rice, lentils etc.) along with required quantity of salt, peppers, spices, etc. as per recipe.
(iii) Vegetables, eggs, potatoes etc. do not require water in solar cookers. Large pieces of vegetables and potatoes are cut into smaller pieces before placing these in solar cooker.
(iv) The food ingredients along with water should preferably fill about half or less the depth of the containers.
(v) Lift the double glass cover to open hot box. Clean it from inside and place the food containers in it. Now close the double glass cover fully.
(vi) Adjust the cooker towards the sun.
(vii) Do not open lid of the hot box too frequently.
Type # 3. Solar Water Heater:
One of the popular devices that harness the solar energy is solar water heating system for heating water. Where heat energy needed at relatively low temperatures i.e. less than 100°C, solar water heaters are used for heating water. Solar water heater is a device which absorbs solar energy and converts it into heat energy. Solar water heater is also called a solar collector.
A typical solar water heater is shown in Figure 4.5. The tubes of the collector are joined to header of the bottom and the top. Insulated storage tank is mounted such that its bottom is at least 60-70 cm above the top of the collector. The tube and fin assembly is insulated at the back and the sides and its front is covered with a glass sheet.
When the sun rays fall on the tube and fin assembly, water gets heated and moves to the upper part of the storage tank by natural convection and relatively heavier cold water from the bottom of the storage, tank flows to the bottom header of the collector.
Type # 4. Solar Lantern:
This is an emergency light charged with sunlight and works for 3 to 4 hours. It has been shown in Figure 4.6.
Type # 5. Solar Home Lighting System:
In this system, the inverter is charged with solar light which can operate two lights and two fans for 5 to 6 hours. It has been shown in Figure 4.7.
Type # 6. Solar Street Light:
In this system, the battery is charged with solar light which operates solar light after sunset. These lights can be installed in the streets and on the road sides and are operated automatically when sun sets. It has been shown in Figure 4.8.
Type # 7. Solar Water Pump:
This system consists of motor which operates during the day time with solar panel for water pumping. It pumps water from water level up to 35 to 40 feet. It has been shown in Fig. 4.9.
