Tuesday

Solar Electricity Basics

SEPA (2005)

SEPA focuses exclusively on solar electric technologies, of which there are two basic types - photovoltaics and solar-thermal electric.

1. Photovoltaics

Photovoltaic (PV) is the technical word for solar panels that create electricity. Photovoltaic material, most commonly utilizing highly-purified silicon, converts sunlight directly into electricity. When sunlight strikes the material, electrons are dislodged, creating an electrical current which can be captured and harnessed. The photovoltaic materials can be several individual solar cells or a single thin layer, which make up a larger solar panel.


Photovoltaic cells power many of the small calculators and wrist watches in use every day. More complex systems provide electricity to pump water, power communications equipment or highway construction signs, and a myriad of other small, off-grid uses, which almost always provide electricity for small and/or intermittent electricity needs that are cleaner and cheaper to operate than extending a power line or using liquid fuels. Rural solar electrification in the developing world, away from the electric grid, can also provide much needed electricity to replace or reduce the use of kerosene lamps, diesel generators, and wood fires for lighting, refrigeration, communication, etc.


Photovoltaics are also making inroads as supplementary power for utility customers already served by the electric grid. In the last two years, grid-connected solar systems are now a larger market than off-grid applications. Currently, compared to most conventional fuel options, photovoltaics are still a very small part of the energy make-up of any country. However, more and more individuals, companies, and communities are choosing PV for a variety of environmental, economic development, emergency back-up, fuel and risk diversification, and now, economic reasons. The economics of a photovoltaic system for your home or business is not just the solar resource (see map below), but rather a combination of the solar resource, electricity prices, and local/national incentives.

Wednesday

Electricity from Solar Power

Mark Zuckerberg, Berlin Institute, 2003

The ultimate source of much of the world's energy is the sun, which provides the earth with light, heat and radiation. While many technologies derive fuel from one form of solar energy or another, there are also technologies that directly transform the sun's energy into electricity.
The sun bathes the earth in a steady, enormous flow of radiant energy that far exceeds what the world requires for electricity fuel.
Since generating electricity directly from sunlight does not deplete any of the earth's natural resources and supplies the earth with energy continuously, solar energy is a renewable source of electricity generation. Solar energy is our earth's primary source of renewable energy.
There are two different approaches to generate electricity from the sun: photovoltaic (PV), solar-thermal technologies. Hence, people can produce their own electricity from the sun. Also they produce it unlimited while the sun shows itself on the sky.
Today, people pay for electricity consumption. Whereas, if electricity can be produced easily with solar energy we would not to need paying for the consumption. In times to come, the technology of solar energy area will improve and consuming of the electricity for free.
Initially developed for the space program over 30 years ago, PV, like a fuel cell, relies upon chemical reactions to generate electricity. PV cells are small, square shaped semiconductors manufactured in thin film layers from silicon and other conductive materials. When sunlight strikes the PV cell, chemical reactions release electrons, generating electric current. The small current from individual PV cells, which are installed in modules, can power individual homes and businesses or can be plugged into the bulk electricity grid.
Solar-thermal technologies are, more or less, a traditional electricity generating technology. They use the sun's heat to create steam to drive an electric generator. Parabolic trough systems, like those operating in southern California, use reflectors to concentrate sunlight to heat oil which in turn creates steam to drive a standard turbine.Two other solar-thermal technologies are nearing commercial status. Parabolic dish systems concentrate sunlight to heat gaseous hydrogen or helium or liquid sodium to create pressurized gas or steam to drive a turbine to generate electricity. Central receiver systems feature mirrors that reflect sunlight on to a large tower filled with fluid that when heated creates steam to drive a turbine.