What is Photovoltaics?
Photovoltaic systems convert solar energy from the sun directly into electricity. This is a renewable form of energy production.
What can photovoltaics do?
Many electric power needs (short of industrial-scale loads) can be met by an appropriately designed and installed photovoltaic (PV) power system.
Who uses photovoltaic (PV) systems?
Photovoltaic is a very rapidly growing global technology with wide-spread application. Homeowners, businesses, governments, local bodies, and non-profit organisations throughout the world use Photovoltaic panels to provide electricity for their needs. Users are found in rural, suburban and urban areas.
What are photovoltaic (PV) cells?
The basic unit of a Photovoltaic system is the photovoltaic cell. Photovoltaic cells can convert light into direct current (DC) electricity. They are usually made of silicon with traces of other elements. In practice, Photovoltaic cells are grouped into modules, which are sealed units of convenient size for handling. Modules in turn can be grouped into panels, which can then be grouped into an array.
Frequent Questions about photovoltaics:
How does Photovoltaic work?
The short answer is very well! Each cell consists of layers of semiconductor materials with different electronic properties. In a typical cell one of the layers of silicon is “doped” with a small quantity of boron to give it a positive (or p-type) character. Another layer at the front of the cell is doped with phosphorus to give it a negative (or n-type) character. The interface between these two layers contains an electric field and is called a junction.
When light (which consists of particles called photons) hits the solar cell, some of the photons are absorbed in the region of the junction, freeing electrons in the silicon crystal. If the photons have enough energy the electrons will be able to overcome the electric field at the junction and are free to move through the silicon and into an external circuit.
As the electrons flow through this external circuit they give up their energy as useful work and return to the solar cell via the wiring. This useful work can take the form of providing light, driving motors for water pumping, running refrigerators, or charging batteries, etc.
Photovoltaic panels are totally solid state and self-contained. There are no moving parts that require maintenance or wear out and no materials are consumed or emitted.
Advantages of Photovoltaic
- Grid-connected solar electricity can be used locally thus reducing transmission/distribution losses (transmission losses were approximately 7.2% in 1995)
- Once the initial Capital cost of building a solar power plant has been spent, operating costs are extremely low compared to existing power technologies.
- When grid-connected, solar electric generation can displace the highest cost electricity during times of peak demand (in most climatic regions), can reduce grid loading, and can eliminate the need for local battery power for use in times of darkness and high local demand; such application is encouraged by net metering. Time-of-use net metering can be highly favorable to small photovoltaic systems.
- Solar electric generation is economically superior where grid connection or fuel transport is difficult, costly or impossible. Examples include satellites, island communities, remote locations and ocean vessels.
- Facilities can operate with little maintenance or intervention after initial setup.
- Solar power is pollution free during use. Production end wastes and emissions are manageable using existing pollution controls. End-of-use recycling technologies are under development
- The 89 petawatts of sunlight reaching the earth’s surface is plentiful – almost 6,000 times more – compared to the 15 terawatts of average power consumed by humans. Additionally, solar electric generation has the highest power density (global mean of 170 W/m²) among renewable energies.
Disadvantages of Photovoltaic
- Solar cells produce DC which must be converted to AC (using a grid tie inverter) when used in currently existing distribution grids. This incurs an energy loss of 4-12%
- Limited power density: Average daily insolation in the contiguous U.S. is 3-7 kW·h/m and on average lower in Europe.
- Solar electricity is not available at night and is less available in cloudy weather conditions. Therefore, a storage or complementary power system is required.
- Solar electricity is almost always more expensive than electricity generated by other sources.
- BP has been involved in solar power since 1973 and its subsidiary, BP Solar, is now one of the world’s largest solar power companies with production facilities in the United States, Spain, India and Australia, employing a workforce of over 2,000 people worldwide. BP Solar is a major worldwide manufacturer and installer of photovoltaic solar cells for electricity.The company has begun constructing two new solar photovoltaic (PV) solar cell manufacturing plants, one at its European headquarters in Tres Cantos, Madrid, and the second at its joint venture facility, Tata BP Solar, in Bangalore, India.
Major photovoltaics companies include BP Solar, Yingli Green Energy, Kyocera, Q-Cells, Sanyo, Sharp Solar, SolarWorld, Motech, SunPower, and Suntech.
Kyocera Corporation has announced a plan to increase its solar cell production to 500 MW per year in 2010. 500 MW is about three times the current output of 180 MW, and the company will reinforce production bases in Japan, the US, Europe and China, investing a total of about ¥30 billion through FY2010. Through this production enhancement, Kyocera looksto meet increasing demand across the world for solar cells.
Q-Cells is the world’s second largest cell manufacturer, based in Thalheim, Germany
Yingli Green Energy is currently one of the largest manufacturers of PV products in China, with an annual production capacity of 200 megawatts of polysilicon ingots and wafers, cells and PV modules, as of July 2007. Yingli Green Energy sells PV modules under its own brand name, Yingli Solar, to PV system integrators and distributors located in various markets around the world, including Germany, Spain, China and the United States.
Sanyo Electric produced $213 million worth of solar cells at its plant in Hungary in 2006, and expects to triple its production capacity to 720,000 units in 2008.
SCHOTT AG is one of the world largest producers of solar photovoltaic technologies. SCHOTT employs over 900 people and has worldwide production capacity of over 130 MW.
Renewable Energy Corporation (REC) is based in Norway, and was established in 1996. Over a relatively short period, REC has become the world’s largest producer of polysilicon and wafers for PV applications. REC is involved in all steps of the value chain, from production of solar grade silicon to wafer, cell and module production. The company has customers all over the globe and seven production plants in three different countries. It operates on three different continents and has approximately 1,100 employees.
United Solar Ovonic, a wholly owned subsidiary of Energy Conversion Devices Ovonics currently employs 700 people and expects to increase its production of thin-film amorphous photovoltaics from 117 MW/yr at the end of 2007 to over 300 MW/yr by the end of 2010. They are best known for producing building-integrated photovoltaic (BIPV) roofing systems (roofing shingle photovoltaics) and continuous roll-to-roll manufacturing of thin-film amorphous silicon alloy multi-junction solar cells.
Sharp Solar is the world’s largest photovoltaic module and cell manufacturer, which manufactures in Japan, and near Wrexham, UK. Sharp Solar produces both single and multi-crystalline solar cells which are used for many applications, from satellites to lighthouses, and industrial applications to residential use. Sharp began researching solar cells in 1959 with mass production first beginning in 1963. Production capacity amounted to 324 MW in 2004.
SunPower Corporation designs and manufactures high-efficiency silicon solar cells and solar panels based on an all-back-contact “All-Black” design. They install them through their subsidiary PowerLight. Recent projects include the Nellis Solar Power Plant, the largest PV installation in North America.
SolarWorld is headquartered in Bonn, Germany, and purchased Shell Solar’s crystalline silicon activities in 2006.
Suntech Power is based in Wuxi, China, where construction of a 1 GW module plant has begun. Year-end production capacity for 2007 is expected to be 480 MW.