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What is Solar Energy?
Only a fraction of that radiation reaches the earth, the rest goes into space, but it is more than enough to provide all of our power needs several times over. More energy from the sun reaches the earth in an hour than the whole world uses in a year. The challenge is harnessing that power and converting it into energy forms more useful to us, such as heat and electricity.
How is Solar Energy Harnessed?
Harnessing passive solar energy often involves appropriate building design and placement, building components such as walls, windows, the floor, and the roof, to make use of sunlight for daytime lighting, space heating and/or space cooling. For example, passive solar heating of buildings occurs when sunlight passes through a window. Landscaping can assist building design elements by providing summer shade to control overheating or by providing a windbreak in the winter.
There are differences in the level of insulation and efficiency, but generally, solar water heaters pump water through pipes located within the panel. The collectors are dark or black to absorb the sun's heat energy, and that energy is used to heat the water in the pipes.
Unfortunately, solar cells are not very efficient, since not all solar energies hitting the cell will "knock" electrons loose. Much of the sunlight is either reflected or absorbed by the cell (like heat). Typically, a cell has an efficiency of about 15%, which is why multiple cells arranged into arrays or panels are needed to produce a usable amount of electricity. Although an efficiency of 15% may seem low, this is a vast improvement over the first PV cells built in the 1950s. They had an efficiency of less than 4%!
What Can Solar Power Do?
Active solar systems can be used for many purposes, including the heating of water. Solar collectors can also be used in a variety of locations, including your own home, a cottage, and other commercial and industrial locations. For example, within your home, a solar hot water system can be used to provide hot water for your showers, laundry, and dishwasher, as well as for applications such as heating your pool or providing radiant floor heating. A system can be designed to provide up to all of your hot water needs, but the average system will provide about 50% to 60% and act as an offset to a traditional water heater.
Your home may not have been designed to make the best use of passive solar energy, and you probably don't have an active solar water heater yet, but you likely already have a solar cell in your home. The earliest PV cells were used for simple applications including the handy, everyday calculator. You may even have a set of solar-powered garden lights in your back yard or have solar panels on your camping trailer. Solar panels have also been used for decades to power the space station.
There are many other commercial applications as well, including powering roadside signs and parking meters. PV cells also have potential for rural and developing world electrification because the panels are relatively small and portable and can be used for all sorts of off-grid applications.
Larger solar panels can be used to provide electricity to homes. Homeowners with south-facing roofs in full sun, or similar sunny space on the ground can provide a significant portion of their domestic electricity use through solar panels. If the solar system is connected to the grid, homeowners can avoid the problem of storage and make use of either the net metering program or the SOP in Ontario. Finally, panels can be grouped together to create a solar farm. 33,500 150-watt panels were grouped together on a solar farm outside of Leibzig, Germany, to create a 5 MW solar farm. At the time it was built in 2004, it was the largest solar farm in the world. The farm is capable of providing enough energy to power 1,800 homes. An even larger plant is planned near Sarnia, Ontario. If the project goes through, the plant will have a capacity of about 40 MW, and generate enough electricity to power between 10,000 and 15,000 homes.
Benefits of Solar Power
Second, unlike conventional fossil fuels, solar energy is free following the initial equipment costs, and is virtually unlimited. Also, the use of the fuel - solar energy - doesn't produce waste or pollution. Like most renewable energies, solar power offers a way to mitigate climate change by replacing the need for greenhouse gas emitting coal and gas-fired generators.
Finally, solar energy is extremely handy for some of the low-power applications mentioned above, such as calculators and parking meters, and may prove to be essential for rural electrification, especially in developing countries. Like wind power, biomass and small hydro, solar also has much to offer the community power sector in Ontario, including economic benefits to the community.
Last Updated: Thursday, October 08, 2009 at 10:26:32 AM
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