The Sun is the main source of energy for Earth’s oceans, atmosphere, land and biosphere. Calculating a year, the solar energy reaches an average of 342 watts per square meter of the earth.
That’s a huge amount of power—44 quadrillion (4.4×1016) watts of power, to be exact. In comparison, a large power plant produces about 1 billion (1×109) watts of electricity. To equal the amount of energy coming from the sun, 44 million such power plants would be needed.
Sun is the nearest star to earth. Even from a distance of 150 million kilometers (or 93 million miles), the Sun holds the planet Earth in its orbit through its gravitational pull. The existence of life on earth is possible due to the light and heat coming from the sun or solar energy radiation.
Plants need sunlight to grow. And other animals including humans need plants for food and oxygen. Without the sun’s heat, the Earth would freeze—there would be no wind, ocean currents, or clouds to transport water.
Like the sun, the solar system has been around for about 5 billion years. Although mankind is not that ancient, they have been using solar energy in various ways for thousands of years.
Solar Energy In Agriculture
Solar energy is essential in agriculture—from farming to growing crops and raising livestock.
Agriculture, which developed about 10,000 years ago, played a key role in the rise of human civilization. Sun-based techniques like planting different crops seasonally on the same land helped produce more crops. Crops were protected from rotting by drying food in sunlight and air. This surplus of food made possible dense settlements and the establishment of orderly societies.
Collecting Sunlight And Heat
Ancient civilizations in different parts of the world used to build dwellings or houses facing south to collect heat and light. For the same reason they used windows and skylights, to ensure ventilation at the same time. These are the basic elements of sun-centered architecture.
Other strategies include using shade and choosing building materials that retain heat, such as stone and concrete.
Greenhouse
Greenhouses are another ancient form of solar energy utilization. By converting sunlight into heat, greenhouses make it possible to grow crops that are not currently possible naturally. That is, with the help of sunlight, plants can be grown in different seasons and in unsuitable climates through greenhouses.
One of the earliest greenhouses was built around 30 AD, before the invention of glass. So early greenhouses were not made of glass, but of transparent sheets of a thin mineral called mica. Created for the Roman Emperor Tiberius, who wanted to be able to eat cucumbers all year round. Although many improvements have been made to increase the variety and quantity of crops, the principles of greenhouses remain the same today.
Solar Energy In Cooking And Disinfection
The first solar box cooker was developed by Swiss physicist Horace de Saussure in 1767. The temperature of the cooker went up to 87.8 °C (190 °F), used for cooking fruit. Now various types of solar cookers are used for cooking, drying and pasteurization.
Pasteurization is a process by which harmful microorganisms in food are destroyed. Since they do not use fossil fuels, the process is completely safe, causing no pollution or destruction of vegetation.
Solar cookers are growing in popularity in many parts of the world. About 5 lakh solar cookers are used in India alone. The country has two of the largest solar cooking systems in the world, which can prepare meals for 25,000 people every day. In Nicaragua, medical equipment is sterilized in clinics using a special type of solar cooker.
Solar Energy For Water Heating
Solar energy can also be used to heat water. Invented in the late 1800s, solar water heaters were superior to wood- or coal-burning stoves because they were hassle-free to clean and cost less to run. They were very popular for American homes located in sunny areas including California, Florida, Arizona. In the early 1900s, cheaper oil and natural gas replaced solar water systems.
And now not only are they available, but solar water systems are becoming commonplace in some countries, including China, Greece and Japan. In Australia, Israel and Spain it is mandatory to use them in new construction.
Solar Energy In Potable Water Preparation
Apart from heating water, solar energy is also used to prepare potable or edible water. Solar Disinfection (SODIS) is one such method. Invented in the 1980s, this process involved filling plastic soda bottles with water and leaving them in sunlight for several hours. It destroys viruses, bacteria and protozoa in water. More than two million people in 28 developing countries of the world use this method for daily drinking water. Note that water sterilized by SODIS remains potable for 24 hours.
Solar Power
Another application of solar technology is the process of converting sunlight into electricity. This can be done in several ways. Two of the most commonly used methods are photovoltaic (solar cells) and concentrating solar power.
Solar cells convert sunlight directly into electricity. The amount of energy each cell produces is extremely small. So, like the panels on the roof of a house, a large number of cells have to be put together to produce enough energy.
The first solar cell was built in 1880. The earliest significant use of solar cells was on the US satellite Vanguard-1, launched in 1958.
A radio transmitter powered by solar cells lasted about 7 years, using conventional batteries that could last only 20 days. Since then, solar cells have been the main source of power for all artificial satellites, including satellites used in the telecommunications industry.
Solar cells are used in everything from calculators and clocks to homes, commercial buildings and even stadiums around the world. The Kaohsiung World Stadium in Taiwan, built to host the World Games in 2009, has more than 8,800 solar panels on its roof. When the stadium is not in use, the electricity generated from the solar panels can meet 80 percent of the electricity needs of the surrounding area.
Some Challenges
There are also some challenges to using solar energy. First, it is irregular, i.e. not continuously flowing. When there is no sunlight, such as at night, electricity cannot be produced. A continuous power supply requires an energy source like wind power or energy storage.
Second, wherever photovoltaic and concentrated solar energy can be used, its equipment takes up a lot of space. With the exception of an existing structure, relocation would displace flora and fauna, which would have a negative impact on the ecosystem.
Besides, the cost of collecting, converting and storing solar energy is very high. But as technology advances and demand increases, so will the cost.
Fossil fuels such as coal, oil and natural gas currently provide most of our electrical and mechanical energy. They also produce almost all of our pollution. Moreover, they are non-renewable resources, i.e. their supply is limited.
On the other hand, the sun provides abundant and free, clean energy. In fact, it provides much more energy than our consumption capacity. The question now is how and when we can take full advantage of it.
