Solar Energy: An Alternative Source of Power

The sun provides the earth with a tremendous amount of energy every day. This energy can be harnessed and used to generate electricity, produce space heating and cooling, heat water and provide lighting for homes and businesses.
 
Traditionally, utilities provide these services by burning fossil fuels. However, as we deplete fossil fuel supplies and better understand the negative environmental effects of burning fossil fuels, the benefits of solar energy technologies become more apparent.
 
For example, burning fossil fuels produces carbon dioxide emissions, which scientists link to global warming. Solar energy is free, inexhaustible and has no negative impact on the environment. These qualities make solar power a significant alternative energy source.
 
The energy in sunlight can be harnessed and converted into electricity to power homes and businesses. A variety of technologies convert sunlight to electricity.

Solar Energy Systems: Photovoltaics

Photovoltaic systems are made up of solar electric cells that convert sunlight directly into electricity. Solar cells are made of semi-conducting material, typically crystalline silicon, which absorbs sunlight. When sunlight hits the solar cell, it knocks electrons loose from their atoms and these electrons flow through the semi-conducting material, producing electricity. Solar cells are combined to form a module, and modules are combined to form an array.
 
Refinements in photovoltaic technology have resulted in the development of thin film solar cells that can be incorporated into roofing, siding and façade products, replacing conventional building materials. This strategy produces a product that offsets the cost of the material it replaces and also generates electricity, improving the cost-effectiveness of the overall installation.

Solar Energy Systems: Concentrating Systems

Concentrating solar power systems use mirrors to focus solar energy on a point or tube. Three types of concentrating solar systems have been invented:
  • A parabolic-trough system uses a U-shaped mirror to concentrate solar energy on absorber tubes, where it heats a fluid. The heat in the fluid is then used to power a generator and produce electricity.
  • A dish/engine system uses a parabolic dish-shaped mirror to concentrate solar energy on a receiver. The solar energy heats a fluid, which is used to generate electricity in a small engine attached to the receiver.
  • A power tower uses a field of tracking mirrors to concentrate the sun's energy on a receiver at the top of a tower. The solar energy heats a fluid—molten salt, in the case of the Solar Two installation in California. The heat stored in the salt generates electricity using a steam generator.
Research into strategies for reducing the manufacturing costs of producing solar photovoltaic cells is underway. The high price of commonly used semi-conducting materials also pushes prices up. As manufacturing processes improve and the popularity of photovoltaics provides an economy of scale, analysts predict that costs will continue to drop.
 
Concentrating solar power shows great promise as a cost-effective strategy for generating utility-scale bulk electricity. Dish/engine systems are also available in units appropriate for smaller-scale electricity generation. These systems require precise and expensive tracking systems to operate optimally, which increases their costs. Costs are expected to go down as the applications become more common and achieve economies of scale.

Solar Power for the Home

Homeowners can benefit from the sun's energy by using solar equipment for the energy services they require. The sun provides enough energy to satisfy all of our energy needs many times over. Commercially available solar technologies that generate electricity, heat water, and light, heat, and cool homes are cost-effective today.