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Solar power and focused heat could provide all global power.
1/10,000 (0.01%) of all suns energy reaching the earth could provide all the energy consumed on earth and eliminate the need for oil, gas, coal, nuclear. Solar power uses the suns radiation and various ways of doing so are being developed. However to be available at night as well as day, means of energy storage or cross world transmission must be developed.
Parabolic trough reflectors
Parabolic reflectors focus the suns rays onto a heat collector containing fluid (water or oil at 400 C) which in turn raises steam in a heat exchanger. The steam powers turbine driven generator/s. Banks of trough mirrors track the sun automatically.The basic energy cost (excluding transmission and storage) is currently the same as that from a $50 a barrel of oil and is could reduce considerably possibly to $20 in the future (ref 142).
The energy received by 1 sq km of desert is equivalent to 1.5 million barrels of oil. A hot desert area of 254 X 254 km covered with these reflectors would theoretically provide the entire world consumption ( ref 127).
A certain degree of heat storage is desirable (in nitrates of Sodium or Potassium) to help diversity and existing installations can include further back up with fossil fuel.
Power can be transmitted long distances by HV DC (High Voltage direct current), including under sea, losses being 3% per 1000 km probably. A further feature in the future is that the shaded areas under the reflectors could be used for crops watered by local desalination plants.
Dish/Sterling engine
A parabolic dish focuses sunlight onto a point to heat a gas or fluid (water) to 1500 C to drive a sterling engine which in turn drives an electric generator. Each dish is dual axis controlled to track the sun.
Efficiency of up to 30% compared to 20% in the case of the trough reflector.
Solar Power Tower
Hundreds of dual axis controlled flat mirrors (heliostats) in a circular array focus energy onto a power tower. A fluid (eg water) is used as a heat collector (eg up to 1000 C) which is stored and used to generate steam in a heat exchanger to drive a turbo alternator. Liquid Sodium may be used in larger arrays as a heat collector.
A refinement is the Multi Tower Solar Array (MTSA) (proposed by D R Mills & P Schramek) to reduce ground area. Several smaller towers recieve radiation from a reduced number of heliostats per tower. This uses areas otherwise blocked or shaded.
More detail about solar power generating systems.
Solar induced draught tower
In NSW Australia a large 1000m tower in the desert induces air heated under glass at ground level. The flow drives wind turbines. This design is based on a smaller 50 kw tower experiment in Spain. The building of five more are planned.
Solar Photo voltaics (ref 127) electricity source of the future?
Photovoltaic cells will be a significant green source of electricity in the future with obvious local application on buildings at the point of use. Power storage would require batteries and diversification obtaind from the grid(s.) However massive arrays of cells are needed to provide power on a large scale.
Photons (sunlight) absorbed by semiconductor material (eg silicon p-n semiconductor junctions) cause electrons to be emitted producing direct current (DC). Voltaic cells consist of a thin film of crystalline semiconductor attached to glass. The glass faces the sun to provide protection from the elements.
A cell 100 sq cm would produce up to 2A at up to 0.4V with 1000 w/m2 radiation. Thus a 233 sq metre array should produce up to 24 kw.
The original single junction devices were only 33% efficient. These are being superceded by thin film materials on glass or ceramics. Cells can be made wafer thin and printed on aluminum foil. Use of low cost materials and production techniques will pull costs down and increase efficiency eg by manipulating materials on a nano scale to keep sunlight bouncing around inside to boost the amount of electricity produced.
The world production of electricity by Photovoltaics is projected to be 0.4% by 2010. There are several installations of 10 to 20 MW in Europe and a 130 MW installation planned in Spain. A 154 MW installation of photovoltaic panel heliostats, which track the sun in both axes, is planned in Victoria Australia by 2013. Light is also being magnified onto the cells eg using Fresnel lenses (light weight lens with wide aperture as used in lighthouses.)
AbuDhabi is building a 6 sq km city for 50,000 residents and 1500 businesses entirely powered by the solar photovoltaics, which should be complete by 2012. Thin film polysilicon rubber will be applied to the surface of buildings and on canopies. A feature will be travel by bike and light rail with no cars. Design by Foster and partners. See Masda project .
550 MW Topaz Solar Farm project will use thin film PV panels by OptiSolar, producing electricilty direct. These swivel in 2 dimensions to track sun. These installations could soon be competitive with CSP and wind but in future may be several times as effective which could enable them to be a major contibution to zero carbon homes, including older dwellings, in addition to large scale arrays / power plants. (ref 187.)
Thin film solar generators.
Solar generators will in future be made up from Polycrystaline thin film (1 to 10 micrometres reduced from 100 t0 300 micrometres). These could be incorporated in flexible materials which could be used as canopies or become cladding for buildings.
Solar panels for buildings
Domestic installations convert the heat collected from suns rays on roof panels which in turn heat water fed into a cylinder to heat water. The first systems of tubes with water circulating are now superceded by metal elements in vacuum tubes transferring heat to water at a header. These are more efficient. Designs need to consider storage volume to carry over from day to day and loss through insulation and (heat) conduction along pipes entering water cylinders.
Solar Car project
Design based on previous car ' Affinity' that run the length of the British Isles in June 2008.
Solar round the world flight 2011 (ref185)
