Photovoltaic
Photovoltaic (PV) devices generate electricity directly from sunlight via an electronic process that occurs naturally in certain types of material. Electrons in certain types of crystals are freed by solar energy and can be induced to travel through an electrical circuit, powering any type of electronic device or load.
PV Devices can be used to power small devices e.g. road signs, calculators or phone call boxes, homes, or even large stores or businesses .
History and future
The photovoltaic effect was observed as early as 1890 by Henri Becquerel, and was the subject of scientific inquiry through the early 20th century; Albert Einstein's only Nobel Prize, in fact, arose from solar power research.
In 1954, Bell Labs in the United States introduced the first solar photovoltaic device that produced a useful amount of electricity, and by 1958, solar cells were being used in small-scale scientific and commercial applications (especially for the space program.)
The energy crisis of the 1970s saw the beginning of major interest in using solar cells for power here on Earth, but prohibitive prices (approximately 30 times current prices) made large scale applications unfeasible.
However, industry developments and research during this period made PV feasible for remote applications (especially for the telecommunications industry,) and a cycle of increasing production and decreasing costs began which continues today.
The new millennium has seen PV become cost-effective in a rapidly growing number of areas as research and production advances continue every day. Global PV market growth has averaged a stunning 25%+ annually over the last 10 years, with worldwide growth rates for the last 5 years well over 35%. (meaning installed power doubles every 4 years or less.) However, this rapid growth is from a very small base; PV still accounts for a small percentage of electricity generation worldwide.
Given appropriate policies, the coming years will continue to see rapid increase in the use of PV for homes and businesses, including the increased usage of new commercial systems of 500,000 watts or more, as well as small, standardized systems for rooftops, 
and attractive "building-integrated" devices in commercial buildings. The "virtuous cycle" of increased sales volume and decreased prices will continue to drive itself, and attempts to bring electricity to the developing world will frequently employ solar as the lowest-cost alternative. New, next-generation PV materials currently under research may bring dramatic, unexpected decreases in price. Small PV systems provide an excellent means of beginning the transition to a hydrogen economy, as they can produce hydrogen through electrolysis in a very scalable fashion.
SEIA Policy Priorities
SEIA is focused on:
- Reducing regulatory barriers to PV installation through the spread of standardized and technically legitimate standards for interconnection and net metering.
- Increasing markets for photovoltaics nationwide through meaningful and appropriate incentive programs at the state and Federal level.
- Ensuring robust and continuing Federal research and development into photovoltaic devices and supporting technologies (inverters, balance-of system equipment, etc.)
Resources on the Web:
Research:
National Renewable Energy Laboratories' National Center for Photovoltaics
Center for the Federal government's ongoing photovoltaics research.
Policy Partners:
- Interstate Renewable Energy Council - The Interstate Renewable Energy Council's mission is to accelerate the sustainable utilization of renewable energy sources and technologies in and through state and local government and community activities.
- Clean Energy States Alliance - The Clean Energy States Alliance (CESA) is a group of 17 publicly managed clean energy funds from twelve states, created to expand the use of clean energy across the country by supporting solar, wind, fuel cells and other clean energy projects and companies.
Concentrating Solar Power
Concentrating Solar Power (CSP) devices optically focus or concentrate the thermal energy of the sun to drive a generator or heat engine. They do so by means of lenses or more commonly mirrors arranged in a dish, trough or tower configuration.
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"Trough" systems, such as those manufactured focus the sun's energy on a pipe filled with a heat exchange fluid, and use that heat to turn a steam generator in a central plant. These plants can be very large; over 354 MW has been installed in California alone, and with the construction of a 50 MW plant near Boulder City due for 2005, there should be enough of this type of generation to power over 100,000 American homes.
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"Power Tower" systems, use a field of computer-controlled flat mirrors to focus solar heat on a central tower, which then runs a central generator. Demonstration systems have shown power outputs of over 10 megawatts, along with the ability to run overnight or in bad weather by storing heated transfer fluid in a hyper efficient"Thermos bottle."
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"Dish" systems use a dish which tracks the sun to focus energy onto a high-efficiency heat engine which generates electricity directly.
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When the sun is unavailable, CSP plants can also provide constant output using natural gas or landfill gas.
SEIA Policy Priorities
SEIA is focused on:
- Ensuring robust and continuing government research and development into trough, tower and dish technologies
- Working to provide appropriate incentives, through tax credits and portfolio standards, for the construction and operation of concentrating solar power plants in the Southwestern US.
Resources on the Web:
Research:
Department of Energy's SUNlab - focal point for US concentrating solar power research.
Policy Partners:
The Western Governor's Association has publicly supported a call for 1000 MW of Concentrating Solar Power in the American Southwest. Download a copy here.
Solar Water Heating
Solar Heating Devices directly absorb the sun's radiation with specially-coated absorbers to heat air or water for use in a building. Solar water heaters can be used in large commercial applications (e.g. hotels or breweries) solar water heaters racked for commercial installation or in attractive, low-profile installations on residences anywhere in the United States.
Solar water heating systems can be either "open loop," in which the water to be heated flows directly through the rooftop collector, or "closed loop," in which the collector is filled with an antifreeze solution that passes through a heat exchanger mounted in or around your normal water heater.
(Closed loop systems can be used anywhere in the US, even in freezing conditions, while open loop devices must be drained during freezing conditions.) During the day, in good weather, your water can be heated entirely by the sun! In any weather, the heating system can back up your existing heater, reducing overall energy costs. The comparatively lower temperature increase required for a swimming pool enables the use of even simpler, lower-cost open loop designs that can keep a pool open and usable for many more weeks in any given year, without the considerable expense and maintenance headaches associated with natural gas usage.
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The largest application of this type to date is likely the 1 million gallon pool used for the 1996 Atlanta Olympics; using a 10,000 square foot solar heating system on this natatorium is estimated to be saving upwards of $12,000 per year in avoided energy costs.
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Direct solar air collectors also exist. These simply circulate air through a pre-engineered enclosure designed to absorb a great deal of solar heat before forcing the air back into the temperature-controlled space, and can be very low-cost.
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In most cases, a properly engineered solar air or water heating collector can provide an excellent return on investment for a homeowner or business, especially as natural gas and heating oil prices continue their volatility and rising price trends.
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History and future
Solar water heating devices are a relatively simple technology, with well-understood materials and manufacturing. Worldwide, they are extremely prevalent - anecdotally displacing approximately 6% of annual residential energy consumption in Israel, for instance. In the United States, states like Hawaii with exceptionally high energy costs enjoy very high market penetration rates, with more than 15% of homes sporting a solar heating devices. Solar heating devices could provide a simple, short-term means of reducing the United States' energy usage by several percentage points.
SEIA Policy Priorities
SEIA is focused on:
- Obtaining EPA / DOE Energy Star recognition for hyper efficient solar water heating devices.
- Reducing regulatory barriers to solar water heating installation through efforts to modify restrictive homeowner's association covenants.
- Ensuring robust and continuing Federal research and development to further reduce the costs of energy from solar thermal devices, and to develop integrated "zero energy buildings" that require no net energy.
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