What is solar energy? Solar energy is the heat and radiation of the sun that reaches the earth. It can be used as a renewable source of energy for various purposes.
Facts: The earth receives approximately 174 petawats of incoming solar radiation per year. From this radiation 30% is reflected back to space and the rest is absorbed by oceans, clouds and land. The spectrum of solar light reaching the surface of the earth is spread among the visible and infrared range and is about 3.850.000 exajoules per year. This means that in one year there is twice as much solar energy reaching the earth as it will ever be obtained by all the non – renewable energy sources (coal, oil, natural gas, uranium).
What kind of technologies exist? There are many different kinds of technologies used to absorb solar energy. Some of the most important are:
Photovoltaic cells: the photovoltaic cells convert sunlight (photons) directly into electricity (voltage) through a process called the PV effect. The PV effect was discovered in 1954 when scientists found that silicon produced electricity when exposed to sun light. Photovoltaic cells are combined into modules to construct solar panels. These panels are mounted on the roof of businesses and houses in order to absorb as much sun as possible. Alternatively, they are installed on tracking devices that follow the sun. Many solar panels combined together are called a solar array.
Solar water heating: the water in the shallow parts of a lake is usually warmer than the water in the deeper parts of the lake. Τhis is because the sun warms the bottom of the lake and this heat is infused to the upper water streams. Τhis is nature’s way of solar water heating. Solar water technologies work in a similar way. Most solar water systems have two main parts: the solar collector and the storage tank. The solar collector is mounted on the roof of buildings in order to collect the solar heat. Small tubes run through the solar collector and carry the water through to be heated. As heat builds up, it warms the water of the tubes which is then passed to the storage tank for further use.
Passive solar technologies: many buildings today are designed to make the most of day light. These ways of using the natural solar energy are called passive solar technologies. Architects design houses with large windows on the south part of the building. These windows absorb the light of the day and make it easier to keep the room warm at night. Also they construct south facing walls from adequate materials that keep the warmth during the day and release it during the night..
Which are the advantages and disadvantages?
Advantages: one of the main advantages of solar energy is that it is potentially inexhaustible. This means that it can provide heat and light for many years to come. Solar energy does not pollute the environment and it does not add to the greenhouse effect emissions. Unlike conventional ways of producing energy, solar energy is environmentally safe and it ensures a balanced ecosystem for the next generations.
Disadvantages: one of the main disadvantages is the cost. Solar panels, solar water systems and photovoltaic installations require a lot of money that the average household cannot afford. Also most solar panels demand many hectares of land in order to be installed and produce energy on a large scale. Apart from this, cloudy weather and low sun exposure during the winter can undermine the effectiveness of solar energy. However, with developing technologies and falling prices solar power can be a good investment for the future.