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Data
One source of greenhouse gas emissions is caused by energy use in a home. A pie chart on the folloing page shows that approximately 50.1% of greenhouse gases produced by a household comes from the use of energy for space heating and cooling (29%), water heating (11.1%), appliances (7.5%) and lighting (2.4%). Solar energy may be used to reduce greenhouse gas emissions, arising from more traditional forms of energy.Solar energy is very complex. It can be collected using photovoltalic solar cells or solar furnaces. A solar furnace works by reflecting the sun's rays with a flat mirror, called a heliostat, which tracks the sun and then reflects solar energy onto curved mirrors. The curved mirrors then focus the concentrated solar energy at a target spot in the test building. A photovoltaic cell (PV) is made of semi-conductors, such as silicon, that absorb light energy. The energy knocks the electrons loose, and then from there they flow freely. Photovoltaic cells have electric fields that force electrons freed by the absorbed light to flow in a certain direction. This is called an electric current. If metal contacts are placed on the top and bottom of the PV cell, they can draw off the current so it can be used as electricity.
Solar cells can only absorb about 15% of the sunlight's energy. Light has wide range of energy, and some of it will pass through the cell. Only certain amounts of electron volts (eV) can be absorbed. This also depends on cell material. Silicon needs 1.1 eV, for example, yet other materials, such as gallium arsenide, can only use different amounts. This is called a Band gap. If a photon has more energy than needed, the energy is lost. This is true, unless the photon has twice the required energy. These effects cause th 70% loss of radiation energy. The amount of energy produced is strictly based on the quantity of solar panels.
Solar energy is very environmentally safe after the initial impact on the environment. As was mentioned earlier, it does not create any greenhouse gas emissions. It is a very safe alternative to fossil fuels.
The table below and Chart #2 show the increasing greenhouse gas levels in Canada from 1990 to 2000.
Year 1990 1992 1994 1996 1998 2000 Kilotonnes (kt) CO2 equivalent 608000 6160000 640000 673000 690000 730000
