Renewable resources of energy : solar energy

Solar energy is the most readily available and free source of energy since prehistoric times. It is estimated that solar energy equivalent to over 15,000 times the world's annual commercial energy consumption reaches the earth every year.
India receives solar energy in the region of 5 to 7 kWh/m2 for 300 to 330 days in a year. This energy is sufficient to set up 20 MW solar power plant per square kilometre land area.
Solar energy can be utilised through two different routes, as solar thermal route and solar electric (solar photovoltaic) routes. Solar thermal route uses the sun's heat to produce hot water or air, cook food, drying materials etc.
Solar photovoltaic uses sun’s heat to produce electricity for lighting home and building, running motors, pumps, electric appliances, and lighting.

advantages of solar energy

Here are some examples of what it has over oil, the world's current number one energy source:

•Solar energy is a renewable resource. Although it cannot be utilized at night or on cloudy days, its availability may be generally relied upon day after day. The solar energy supply will last as long as the sun.

•Oil, on the other hand, is not renewable. It takes millions of years to form. Currently, oil reserves are being depleted at a rate much quicker than more would take to develop.

•Solar energy is non-polluting. Of all the advantages of solar energy over oil, this is perhaps the most important. The burning of oil releases carbon dioxide and other greenhouse gases into the air. In addition to this, the process of obtaining it may result in damaged ecosystems through dredging or spills.

•Solar cells are long-lasting and require very little maintenance

• Although solar panels and their accessories (solar lights, etc.) may be expensive to buy at the onset, money is saved in the long run. This is because energy from the sun is widely available and free. Today rising oil prices are a major frustration on many government as well as individual levels.

•Solar powered lights and other solar powered products are very easy to install. This is because there are few wiring issues and little need to ever dig supporting trenches.

The many advantages of solar energy range from benefiting your pocketbook to benefiting the environment. In contrast, few features could be considered disadvantages. These include the current costliness of solar cells, as well as the fact that solar power cannot be created at night or on darkened days (though it can be stored during brighter times.)

Still, the advantages of solar energy far outweigh the disadvantages. In addition to this, the disadvantages are sure to be overcome as technology improves.

applications of solar energy

1) solar water heater

Most solar water heating systems have two main parts: a solar collector and a storage tank. The most common collector is called a flat-plate collector (see Figure 12.1). It consists of a thin, flat, rectangular box with a transparent cover that faces the sun, mounted on the roof of building or home. Small tubes run through the box and carry the fluid – either water or other fluid, such as an antifreeze solution – to be heated. The tubes are attached to an absorber plate, which is painted with special coatings to absorb the heat. The heat builds up in the collector, which is passed to the fluid passing through the tubes. An insulated storage tank holds the hot water. It is similar to water heater, but larger is size. In case of systems that use fluids, heat is passed from hot fluid to the water stored in the tank through a coil of tubes. Solar water heating systems can be either active or passive systems. The active system, which are most common, rely on pumps to move the liquid between the collector and the storage tank. The passive systems rely on gravity and the tendency for water to naturally circulate as it is heated. A few industrial application of solar water heaters are listed below:  Dairies: Ghee (clarified butter) production, cleaning and sterilizing, pasteurization.
 Textiles: Bleaching, boiling, printing, dyeing, curing, ageing and finishing.
 Breweries & Distilleries: Bottle washing, wort preparation, boiler feed heating.
 Chemical /Bulk drugs units: Fermentation of mixes, boiler feed applications.
 Electroplating/galvanizing units: Heating of plating baths, cleaning, degreasing applications.
 Pulp and paper industries: Boiler feed applications, soaking of pulp.

2) solar cooker

Solar cooker is a device, which uses solar energy for cooking, and thus saving fossil fuels, fuel wood and electrical energy to a large extent. However, it can only supplement the cooking fuel, and not replace it totally.
It is a simple cooking unit, ideal for domestic cooking during most of the year except during the monsoon season, cloudy days and winter months.
Types of solar cookers :
1) Parabolic concentrating solar cooker :
A parabolic solar concentrator comprises of sturdy Fibre Reinforced
Plastic (FRP) shell lined with Stainless Steel (SS) reflector foil or
aluminised polyester film. It can accommodate a cooking vessel at its
focal point. This cooker is designed to direct the solar heat to a
secondary reflector inside the kitchen, which focuses the heat to the
bottom of a cooking pot. It is also possible to actually fry, bake and
roast food. This system generates 500 kg of steam, which is enough to
cook two meals for 500 people (see Figure 12.3). This cooker costs
upward of Rs.50,000. Positioning of solar panels or collectors can
greatly influence the system output, efficiency and payback. Tilting
mechanisms provided to the collectors need to be adjusted according to
seasons (summer and winter) to maximise the collector efficiency.
The period four to five hours in late morning and early afternoon
(between 9 am to 3pm) is commonly called the "Solar Window". During
this time, 80% of the total collectable energy for the day falls on a solar
collector. Therefore, the collector should be free from shade during this
solar window throughout the year - Shading, may arise from buildings or
trees to the south of the location.


2)Box type solar cookers:
The box type solar cookers with a single
reflecting mirror are the most popular in India. These cookers have
proved immensely popular in rural areas where women spend
considerable time for collecting firewood. A family size solar cooker is
sufficient for 4 to 5 members and saves about 3 to 4 cylinders of LPG
every year. The life of this cooker is upto 15 years. This cooker costs
around Rs.1000 after allowing for subsidy. Solar cookers.