Here are some of the most important uses of solar energy: (a. Solar water heating (b). Solar heating of buildings. (c. Solar distillation (d). Solar pumping. (e. Solar drying of agricultural products. (f.) Solar furnaces. (g.) Solar cooking. (h) Sun electric power generation. (i.) Solar thermal power production. (j.) Solar greenhouses.
(a) Solar Water Heating:
A solar water heater unit consists of a flat blackened metal collector and associated metal tubing that faces the sun. The transparent glass plate collector is covered with a thermal insulation layer and has a transparent cover.
The collector’s metal tubing is connected to an insulated tank that stores hot water on cloudy days. The collector absorbs the sun’s radiations and transfers them to the water that circulates through the tubing by gravity or using a pump.
The associated metal tubing is used to supply hot water to the storage tank. This water heating system is used in guest houses, tourist bungalows and hospitals, and domestic and industrial units.
(b). Solar Heating of Buildings:
Solar energy is a great way to heat buildings.
(a) Using the sun’s radiation to collect energy by an element in the building, i.e., Through large, south-facing windows, solar energy is directly admitted to the building.
(b) Separate solar collectors that heat water or air or storage devices to store the solar energy collected for later use.
The heat is transferred to the building by traditional equipment like fans, ducts, hot-air registers, and air outlets. To heat living areas of buildings.
The heated water or air from the collector can be transferred to the heat storage device, such as a well-insulated water tank or another heat holding material if the building doesn’t require heat. As a backup system, an auxiliary heating system that uses oil, gas, or electricity is needed for inclement weather.
(c) Solar-distillation:
There is a shortage of potable water in semi-arid and coastal areas. These areas have a lot of sunlight that can convert saline water to potable distilled water using solar distillation. This method allows solar radiation to enter through a transparent, airtight glass cover into a shallow, blackened basin that contains saline water.
The covers reflect solar radiation and heat into the blackened surface. This causes the water to evaporate from its brine (impure saltwater). The cool interior of the roof allows the vapors to condense and form purified water.
Condensed water flows down the roof, collects in the troughs at the bottom, and then goes into a storage tank to provide potable distilled water for areas where there is scarcity. This includes schools, defense labs, hospitals, and the pharmaceutical industry. This system produces distilled water at a lower cost per liter than other energy-based methods.
(d) Solar-pumping:
Solar pumping uses solar-energy power to pump water for irrigation purposes. This method is best for irrigation purposes as it is the most efficient for pumping water. The summer heat months have the highest demand for water pumping. When solar radiations are low, the need for water pumping will be less because the crops’ transpiration losses are lower.
(e), Solar Drying of Agricultural and Animal Products
This is an old method for using solar energy to dry agricultural and animal products. A simple cabinet dryer is used to dry agricultural products. It consists of a box that has been insulated at its base and painted black on the inside. Then, it is covered with a transparent inclined sheet of glass.
Ventilation holes are located at the top and base of the sides to allow air to flow over-drying material placed inside the cabinet on the perforated tray. These racks or perforated trays are designed to protect the skin from solar radiation.
The sugar content of fruits is increased upon drying by solar drying. This improves their quality. Soft fruits are more susceptible to insect attack because of their sugar content. However, fruit drying can save considerable time and reduce the likelihood of insect attacks.
Chilled chilies are currently dried by spreading them out on the floor. This requires lots of space and manual labor for material handling. It is also difficult to preserve their quality and taste if drying is done in controlled conditions. Sun-drying can cause products to become spoiled by sudden rains, dust storms, or birds. Reports also reveal that sun-dried chilies cannot be dried to very low moisture levels.
The chilies are more susceptible to bacteria and fungi. Sometimes, sun drying can cause overdrying and loss of quality. These disadvantages can be overcome by using solar energy to dry the produce.
Other solar-dried crops include potato chips and berseem, maize and paddy grains, ginger, potatoes, cashew nuts, timber, veneer drying, and tobacco curing. Solar dried animal products include spray drying milk and fish drying.
(f) Solar Furnaces:
A Solar furnace produces high temperatures by concentrating solar radiations onto a specimen with a series of heliostats, which are turn-able mirrors arranged on a sloped surface. The solar furnace can be used to study the properties of ceramics at very high temperatures beyond what is possible in laboratory experiments with flames or electric currents.
Heating can be done without contamination. Temperature can also be controlled by changing the focal point. This is particularly useful for chemical and metallurgical operations. An open specimen can be used to measure various property values. The production of nitric acids and fertilizers from the air is important for future solar furnaces use.
(g) Solar Cooking:
Cooking uses a variety of fuels, including kerosene and cooking gas, as well as dung cakes, kerosene and cooking gas. These fuels are in short supply due to the energy crisis. Wood, coal, kerosene and cooking gas are either degrading or too valuable to be wasted. Cow dung can also be used to improve soil fertility. Developing solar cookers and solar energy has been necessary to make this possible. The flat plate, the box-type solar cooker, is the simplest solar cooker.
It is made up of a metal or wooden box that has been well insulated and blackened on the inside. The box is only able to receive solar radiation of a short wavelength. Higher wavelength radiations cannot pass through the glass covers. This reduces heat loss and minimizes re-radiation.
Convection heat loss can be minimized by making the box airtight. For minimizing heat loss from convection, the box should have a rubber strip placed between its upper lid and box. The space between the outer cover and the blackened tray is filled with an infuriating material such as glass wool, sawdust, or paddy husk.
The sun’s rays can penetrate the glass and absorb the blackened surface, causing a rise in the temperature within the box. The solar box can be used to store blackened cooking pots.
Uncooked food is cooked using the heat energy generated by the solar box. The collector area of a solar cooker with this feature can be increased by adding a reflector mirror to the reflector to increase the heat energy in the box. This will result in a temperature rise of 15 to 25 degrees Celsius.
Solar cookers don’t require fuel or attention to cook food. There is no overcharging of food, and the best advantage is that the nutritional value of cooked food is high because the vitamins and natural flavors of the food have not been destroyed.
The solar cooker’s maintenance cost is negligible. The solar cooker’s main drawback is the inability to cook food at night, on cloudy days, or at short notice. A solar cooker is slower for cooking and can’t cook chapattis.
(h). Solar Electric Power Generation:
Photovoltaic cells can produce electricity or solar energy directly. Photovoltaic cells are energy conversion devices that convert sunlight photons into electricity. It is composed of semiconductors that absorb photons from the sun and create free electrons with high energies.
These electrons, high in energy and free of any toxicity, are induced by an electrical field to flow out from the semiconductor to perform useful work. Photovoltaic cells are usually equipped with a p junction of different materials with different electrical properties. These cells can be made using various fabrication techniques to attain maximum efficiency.
These cells can be arranged in series or parallel to make cell modules. These modules have many special features, such as high reliability, low fuel consumption, minimal maintenance costs, portability and modularity. They also provide pollution-free working.
Photovoltaic cells are used to power irrigation pumps, railway crossing warnings, navigational signs, highway emergency call systems, automated meteorological stations, and other functions in areas that are difficult to install power lines.
They can also monitor the weather and provide portable power sources for TVs, computers, watches, computer card readers and battery charging. Photovoltaic cells can also power pump sets, provide electricity in rural areas, and supply drinking water. Street lights etc.
(i). Solar Thermal Power Production:
Solar energy conversion to electricity via thermal energy is called solar thermal power production. This process uses solar energy to heat any working fluid, such as water, gas, or other volatile liquid. The heat energy is then converted to mechanical energy by a turbine. This mechanical energy is then converted into electrical energy by a turbine and a conventional generator.
Production through Solar Ponds of Power:
A solar pond can be a natural or artificial body that uses water to absorb and store solar radiation. It is very small (5-10 cm in depth) and has a bottom of black plastic (radiation-absorbing). The cover is made of curved fiberglass and allows solar radiation to enter. It also reduces radiation losses due to convection (air movement) and radiation. A bed of insulation material is placed under the pond to reduce heat loss.
Solar ponds use water to collect and store solar energy. This can be used in many ways, including space heating, industrial process heating, and electricity generation by using a turbine driven by the evaporation of an organic fluid with low boiling points.
(j). Solar Green Houses:
A greenhouse is made of transparent material, such as glass or plastic. It collects sunlight and uses it to grow plants. The greenhouse has heating, cooling, and ventilating devices to regulate the temperature.
While solar radiation can pass through the greenhouse’s glass, thermal radiations from objects inside the greenhouse cannot. The radiation is trapped in the greenhouse, causing an increase in temperature.
Because the greenhouse structure is enclosed, the greenhouse’s air gets enriched in CO 2 because there is no mixing between the greenhouse and the ambient air. Due to limited transpiration, there is less moisture loss. These features allow for plant growth all year.