Renewable Energy
Photo: The solar panels atop West Irving Library.
The sun has produced energy for billions of years. Solar energy is the sun's rays (solar radiation) that reach the Earth. This energy can be converted into heat and electricity. Radiant energy from the sun has powered life on earth for many millions of years.
In the 1830s, the British astronomer John Herschel famously used a solar thermal collector box – a device that absorbs sunlight to collect heat – to cook food during an expedition to Africa. Today, people use the sun's energy for a variety of purposes.
Heat and Electricity
When converted to thermal energy, solar energy can be used to heat water for use in homes, buildings or swimming pools; to heat spaces inside homes, greenhouses and other buildings; and to heat fluids to high temperatures to operate a turbine that generates electricity.
Solar energy is converted to electricity in two ways:
- Photovoltaic (PV devices) or solar cells change sunlight directly into electricity. Individual PV cells are grouped into panels and arrays of panels that can be used in a wide variety of applications ranging from single small cells that charge calculator and watch batteries, to systems that power single homes, to large power plants covering many acres.
- Solar thermal/electric power plants generate electricity by concentrating solar energy to heat a fluid and produce steam that is then used to power a generator.
Benefits and Limitations
There are two main benefits of solar energy:
- Solar energy systems do not produce air pollutants or carbon dioxide.
- When located on buildings, solar energy systems have minimal impact on the environment.
There are two main limitations of solar energy:
- The amount of sunlight that arrives at the earth's surface is not constant. It varies depending on location, time of day, time of year and weather conditions.
- Because the sun doesn't deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate.