Solar power is the conversion of sunlight into electricity, either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaics convert light into an electric current using the photovoltaic effect.
The image above illustrates how a Solar Panel converts sunlight into Electricity (Photovoltaic Effect)
Photovoltaics were initially, and still are, used as a source of renewable power for small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. They are an important and relatively inexpensive source of electrical energy where grid power is inconvenient, unreasonably expensive to connect, or simply unavailable. However, as the cost of solar electricity is falling, solar power is also increasingly being used even in grid-connected situations as a way to feed low-carbon energy into the grid.
Solar power is anticipated to become the world's largest source of electricity by 2050. The International Energy Agency expects solar photovoltaics and concentrated solar power to contribute about 16 and 11 percent of worldwide demand, respectively, with most installations being deployed in China and India.
Commercial concentrated solar power plants were first developed in the 1980s. The 392 MW Ivanpah installation is the largest concentrating solar power plant in the world, located in the Mojave Desert ofCalifornia. Other large CSP plants include the SEGS (354 MW) in the Mojave Desert of California, the Solnova Solar Power Station (150 MW) and the Andasol solar power station (150 MW), both in Spain. The two 550 MW solar farms, Topaz Solar Farm and Desert Sunlight Solar Farm in the United States, are the world’s largest photovoltaic power stations.
The image above illustrates how a typical Solar System on a house would work Photovoltaics
A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photovoltaic effect. The first solar cell was constructed by Charles Fritts in the 1880s. The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery. In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide, although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.
The array of a photovoltaic power system, or PV system, produces direct current (DC) power which fluctuates with the sunlight's intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of inverters. Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase.
Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets. In these grid-connected PV systems, use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such stand-alone power systems permit operations at night and at other times of limited sunlight.
The image above illustrates how a typical Concentrated Solar Power Plant works
Concentrated Solar Power
A parabolic collector concentrates sunlight onto a tube in its focal point. Main article: Concentrated solar power
Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists: among the best known are the parabolic trough, the compact linear Fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage. Thermal storage efficiently allows up to 24-hour electricity generation.
A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The reflector is made to follow the sun during daylight hours by tracking along a single axis. Parabolic trough systems provide the best land-use factor of any solar technology. The SEGS plants in California and Acciona's Nevada Solar One near Boulder City, Nevada are representatives of this technology.
Compact Linear Fresnel Reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants.
The Stirling solar dish combines a parabolic concentrating dish with a Stirling engine which normally drives an electric generator. The advantages of Stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime. Parabolic dish systems give the highest efficiency among CSP technologies. The 50 kW Big Dish in Canberra, Australia is an example of this technology.
A solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP technologies. The PS10 Solar Power Plant and PS20 solar power plant are examples of this technology.
Solar Power in South Africa
Solar power in South Africa includes photovoltaics (PV) as well as concentrated solar power (CSP). Installed capacity is expected to reach 8,400 MW by 2030, along with 8,400 MW of wind power
In 2014 several Solar PV have been commissioned, including the 96 MW Jasper Solar Energy Project, one of Africa's largest photovoltaic power stations providing enough solar power for 30,000 homes.
South Africa's Solar Potential
South Africa's insolation greatly exceeds the average values in Europe, Russia, and most of North America.
The image above illustrates the potential for solar energy in South Africa Plants - operational and projected
A 50 MW concentrated photovoltaics (CPV) power plant is planned for Touwsrivier, in Western Cape, South Africa. A 75 MW solar power plant started production on September 13, 2013 in Kalkbult, in the Northern Cape(implemented by Scatec). Two other PV plants will be completed by the same company in 2014. These are located at Linde in the Northern Cape and Dreunberg in the Eastern Cape, both sun drenched regions boasting some of the best conditions for solar power in the world. Altogether, these 3 plants will provide power for around 90,000 South African households.
Sonnedix and Juwi have announced that they will construct an 86 MW solar photovoltaic (PV) plant in the Northern Cape province. The Mulilo Sonnedix plant in Prieska plant will be larger than any PV plant currently on line in the African continent, and was awarded through the third round of the South Africa's Renewable Energy Independent Power Producer Programme (REIPPP). Financial close on the project is targeted for July 2014, with commissioning planned for the second half of 2015.
Iberdrola has completed the Jasper Solar Energy Project solar photovoltaic (PV) power plant, which at 96 MW is the largest in Africa, the company announced. It was carried out in a desert area with extreme temperatures and involved the installation of over 325,000 PV modules. This PV plant is located in Northern Cape province in a remote, semi-desert location. It covers a surface area equivalent to 205 football pitches.
Acciona has put the Sishen solar photovoltaic (PV) plant into service in December 2014. It has a peak capacity of 94.3 megawatts (MWp) – 74 nominal MW – and is located in Dibeng in the Northern Cape province. Its horizontal tracking structures allow the PV panels to capture more radiation by following the sun’s trajectory across the sky. The plant will produce electricity equivalent to the consumption of around 100,000 South African households, or around 420,000 people (2011 South African household size = 3.6 persons).
As of January 2015 a total of 593 MW produced from PV plants were connected to the grid.
A consortium led by ACWA Power International (Saudi Arabia) has completed financing and begun construction on a 50 MW concentrating solar power (CSP) project in South Africa's Northern Cape. The Bokpoort CSP project includes 9.3 hours of thermal energy storage, which will allow it to meet demand during peak hours between 5 and 9 PM. ACWA describes this system as the largest thermal storage system ever built for a CSP plant of its size and capacity.
Two CSP plants are being built by Abengoa in the Northern Cape. Khi Solar One is a Solar Tower plant of 50 MW capacity near Upington and Kaxu Solar One is a Parabolic Trough plant of 100 MW capacity near Pofadder with storage capability for 3 hours.
Solar Thermal Energy See also: Solar thermal energy
The South African government requires renewable energy to replace 10,000 GWh of electricity by 2013. The Department of Energy estimates that 23% of this target can be met through solar water heating and Eskom is therefore actively encouraging consumers to switch to solar water heating.