| The sun represents the most abundant, most | | | | design and the ambient air temperature, but they are |
| renewable form of energy available to our planet. | | | | almost always more efficient gatherers of the sun's |
| Some experts estimate that the amount of energy | | | | energy than their photovoltaic counterparts and |
| provided by the sunlight that strikes the Earth | | | | efficiencies in excess of 50% are not uncommon. |
| represents 8,500 times the amount needed to power | | | | Solar Power Towers. Solar power towers are |
| the entire human race. New ways of harnessing this | | | | massive power plants that use fields of mirrors to |
| energy are being invented every day, and as energy | | | | focus the sun's rays on a central tower. The tower |
| costs continue to rise, the popularity and interest in this | | | | may contain either water or molten salt. Either way, |
| technology continues to grow. Here are a few | | | | the end result is steam generated to drive a |
| examples of what is being done to harness the power | | | | conventional turbine that produces electricity. These |
| of the sun. | | | | plants can store the sun's energy in the form of heat |
| Photovoltaic solar cells. Photovoltaic solar cells are | | | | and then convert it into electricity even on cloudy days |
| what most people think of when they think of solar | | | | or at night. The largest existing solar power tower is |
| panels. They convert sunlight that strikes their surface | | | | the Planta Solar 20 located in Spain. This tower |
| directly into electricity. Generally, the electricity that is | | | | includes 1,255 "mirrors" with a surface area of 1,291 sq |
| generated is then stored in batteries which are used to | | | | ft each. Each mirror is motorized and automatically |
| power devices. This evens out the flow of electricity | | | | adjusts to keep the sun's rays focused on the tower. |
| from the solar cell as its power output is proportional to | | | | The plant is capable of producing 20 megawatts of |
| the intensity of the sunlight that strikes its surface. | | | | electricity (enough to power about 10,000 homes). The |
| Photovoltaic solar cells are not very efficient. Typical | | | | efficiency of solar power towers is better than that of |
| efficiency is between 9% and 14% although there are | | | | photovoltaic solar cells at between 14% and 17%. |
| some newer designs that claim 40% or greater | | | | The demand for clean and renewable sources of |
| efficiency. | | | | energy is growing. One company, BrightSource Energy, |
| Solar heating. Solar heating systems use solar | | | | is heading up the "Ivanpah Project"... a 440 megawatt |
| collectors (panels) that capture the sun to heat air or | | | | solar electric generating system that is expected to |
| fluid that circulates through them. This heated fluid can | | | | begin construction in Southern California in mid 2010. |
| then be used to heat a building or for hot water. | | | | This is an energy initiative that's gaining steam (no pun |
| "Active" solar heating systems use pumps and | | | | intended) and will continue to grow as the cost of |
| controls to force fluid through the system while lesser | | | | electricity produced using these methods continues to |
| efficient "passive" systems generally use natural | | | | fall. Look for solar energy conversion of all types to |
| convection to achieve fluid flow. The efficiency of | | | | gain momentum in the near future. |
| solar heating collectors varies widely depending on | | | | |