Every schoolboy knows that the Sun provides us with our energy. It travels to us in the form of sunlight, but by the time it reaches the earth's surface, it can be very diluted. This is partly because of the distance it has to travel (93 millions miles), and partly because of the effect of clouds and the earth's atmosphere.
Leaving the half of sunlight that's visible to us to one side, what's left is radiation: around 45% of it is infrared, with ultraviolet and other forms combining to make less than 5% of the total. Although most of us think it's the light that's harnessed in solar power, it's not. The part of sunshine the scientists are able to turn into thermal energy (heat) is radiation.
The power of sunlight has the potential to satisfy all the Earth's energy needs, if only it could be efficiently gathered and used. The advantages are clear: it is an inexhaustible supply (at least for the foreseeable future) and, unlike the dwindling supply of fossil fuels coal, petroleum, and natural gas, it is non-polluting.
Something like two hundred thousand times all the electricity we generate and consume in the entire world in a day arrives for free from the Sun each and every day of every year. The sun doesn't have a meter fitted to it, all that energy is 100% free. The only cost we have is the cost of harvesting it, though that has been proving remarkably expensive.
Solar panels are what the scientists call "collectors", and their job is to attract solar energy and convert it into heat. There are two main types of collectors: flat-plate collectors and concentrating collectors. Each type has to be pretty large to collect enough radiation. Even in a sunny climates like those of India, Florida and Morocco, a total of 40 square meters is of solar collector is needed to provide just a single person's energy requirements.
Simple flat-plate collectors are made up of a blackened metal plate, covered with sheets of glass. The sunlight falls on the panel and the heat is trapped. Tubes at the rear of the device hold what are known as "carrying fluids" - usually water treated with antifreeze -and that will take the heat to an insulated boiler or other collection and storage device.
When greater efficiency and higher temperatures are needed, a concentrating, or focusing, collector is used. Sometimes they are called "solar furnaces" and they work by concentrating sunlight from a large area into a smaller space, using mirrors and/ or lenses. Temperatures of 2,000 C (3,600 F) or more have been achieved. Typically they will be used to power steam engine generators.
Solar radiation can also be converted directly into electricity by photovoltaic cells. They work by generating a small electric voltage (around 2 watts) when light strikes the junction between a metal and a semiconductor, such as silicon. To generate hundreds or thousands of kilowatts of electric power (a solar electric plant) you need to connect lots of these cells together. But because the energy efficiency of current photovoltaic cells is only about 15-20%, vast and very costly assemblies of such cells are required to produce even moderate amounts of power. That's why we only tend to find them on watches and calculators.
Leaving the half of sunlight that's visible to us to one side, what's left is radiation: around 45% of it is infrared, with ultraviolet and other forms combining to make less than 5% of the total. Although most of us think it's the light that's harnessed in solar power, it's not. The part of sunshine the scientists are able to turn into thermal energy (heat) is radiation.
The power of sunlight has the potential to satisfy all the Earth's energy needs, if only it could be efficiently gathered and used. The advantages are clear: it is an inexhaustible supply (at least for the foreseeable future) and, unlike the dwindling supply of fossil fuels coal, petroleum, and natural gas, it is non-polluting.
Something like two hundred thousand times all the electricity we generate and consume in the entire world in a day arrives for free from the Sun each and every day of every year. The sun doesn't have a meter fitted to it, all that energy is 100% free. The only cost we have is the cost of harvesting it, though that has been proving remarkably expensive.
Solar panels are what the scientists call "collectors", and their job is to attract solar energy and convert it into heat. There are two main types of collectors: flat-plate collectors and concentrating collectors. Each type has to be pretty large to collect enough radiation. Even in a sunny climates like those of India, Florida and Morocco, a total of 40 square meters is of solar collector is needed to provide just a single person's energy requirements.
Simple flat-plate collectors are made up of a blackened metal plate, covered with sheets of glass. The sunlight falls on the panel and the heat is trapped. Tubes at the rear of the device hold what are known as "carrying fluids" - usually water treated with antifreeze -and that will take the heat to an insulated boiler or other collection and storage device.
When greater efficiency and higher temperatures are needed, a concentrating, or focusing, collector is used. Sometimes they are called "solar furnaces" and they work by concentrating sunlight from a large area into a smaller space, using mirrors and/ or lenses. Temperatures of 2,000 C (3,600 F) or more have been achieved. Typically they will be used to power steam engine generators.
Solar radiation can also be converted directly into electricity by photovoltaic cells. They work by generating a small electric voltage (around 2 watts) when light strikes the junction between a metal and a semiconductor, such as silicon. To generate hundreds or thousands of kilowatts of electric power (a solar electric plant) you need to connect lots of these cells together. But because the energy efficiency of current photovoltaic cells is only about 15-20%, vast and very costly assemblies of such cells are required to produce even moderate amounts of power. That's why we only tend to find them on watches and calculators.
About the Author:
The sun could power all of the earth's energy needs. All me have to do is devote more time, money and facilities to solving the problem. The Free Solar Energy Homes Guide helps you make your home more energy efficient and environmentally-friendly.
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