Solar Poster

Highlights

• Two types of collection systems
  • Active - Uses other energy sources to increase effectiveness of the pannels. These systems include solar cells, solar heating, and solar heating.
    • Line focus: USes a trough or lines of mirrors to focus into a long line. This system is used in California.
    • Point focus: Uses a dish to "move" the light onto a central point where a collection center is.
    • Non-focusing: Has the benefit of being aboe to use diffuse solar radiation that can not be focused.
  • Passive - Requires no outside energy souces. It uses already existing architectural structers to maximize collection.

Power

• The most common way of collecting solar power is through the use of Photovoltaic Cells (PV). These are semiconductors.
  • Because of the high cost in production of these cells, they haven't been widely used until recently. A common place to find these are in solar powered calculators and at roadside assistant emergency phones. A third place that they are widely used is in powering satellites. The average retail cost between 1995 and 2005 was between $4 and $7.50 a watt. In 2004 the production of these cells jumped by 60%. This trend was expected to continue through 2005, but limited supplies of silicon have hampered production.
  • On a clear day at the equator the solar radiaton is approximately 1000 W/m². 1 square meter of a 10% efficient PV can continuously power a 100 W light bulb.
  • The most common and efficient material is Silicon, which can be produced in three manners.
    • Single crystal or monocrystaline wafers. Most commercial cells of this type have an efficiency on the order of 14-20 %. Because of the need to cut these from a cylindrical ingot they produce a lot of refined silicon waste and are expensive.
    • Poly or multi crystalline: these are cheaper to produce than single crystal, but have a lower efficiency. To make up for that, they can cover larger areas.
    • Ribbon silicon: “formed by drawing flat thin films from molten silicon and has a multicrystalline structure”. They have little silicon waste, especially compared to single crystal. Typically these are least efficient.

Environmental Impact

Comparison of Power Plants

Background

• The original passive solar systems date back to the ancient greeks and romans who used solar energy to heat buildings by having south facing windows.

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