Why is everyone so worried about energy today?
The earth's non-renewable energy resources—like coal and oil-are being depleted too irresponsibly and quickly. The result is environmental damage on a scale we may have never seen before…and which we may never be able to fix.
Temperatures are rising, as are pollution levels, as are fuel prices. Most countries in the world will be facing serious energy shortages in the near future. In developing countries, improved quality of life and industrialisation are causing increasing energy demands. We seem to be creating a grim future.
What is "green energy" and why does it matter?
Against the scenario described above, terms like green energy and sustainability hold the key to a better tomorrow.
Green energy refers to natural sources of energy that are environmentally friendly-energy that does not produce pollution in its wake and is naturally replenished.
The common sources of renewable energy would include power from anaerobic digestion, biomass power, fuel-cell power, geothermal power, small-scale hydropower, solar power, tidal power, wave power and wind power. Some people add nuclear power in the category of green energy-this, however, can be debated because of issues related to nuclear safety and waste.
Green energy is increasingly gaining value in today's more environmentally-conscious world, in which people are aware of the importance of sustainable, renewable energy sources and the impact human activities have on the environment. Green energy is being harnessed and used for electricity, heating and cogeneration.
Is it economically viable to use green energy?
Both by choice and legislation, consumers are turning to green energy to meet domestic, business and manufacturing needs. And economic benefits and concessions are being offered to incentivise the generation and use of green energy:
Renewable energy certificates or RECs (also known as green certificates or green tags) are tradable commodities that attest to the energy an organisation generates by using renewable energy sources. Typically, one certificate represents generation of 1 Megawatthour of electricity. Countries using green certificates as national trading schemes include Poland, Sweden, some states in the USA, the UK, Italy and Belgium (Wallonia and Flanders).
Further, different initiatives have been started to regulate greenhouse emissions and ameliorate the effects of global warming. Examples include the Kyoto Protocol (drawn up in Kyoto in 1997) and the G8 Climate Change Roundtable (formed at the 2005 World Economic Forum) which aim to reduce emissions by the world's richest countries; and the European Union Emission Trading Scheme.
The emission / emissions trading approach-sometimes called cap and trade-facilitates large scale reduction by setting a limit or cap on the amount of a pollutant that can be emitted. Emission permits are issued to the relevant organisations / industries, which have to hold an equivalent number of allowances or credits (which represent permission to emit a specific amount of pollutants). Credits cannot exceed the cap, and if they do, the over-polluting organisation needs to "trade" (or buy) credits from an under-polluting one. Carbon credits are exchanged between businesses or bought and sold in the global marketplace at the prevailing market price. They can be used to finance carbon reduction schemes between trading partners and around the world.
Carbon finance, which encompasses the many financial implications of living in a carbon-constrained world, has become a new branch of environmental finance.
What exactly is solar energy?
Solar energy refers to the energy generated by the sun: its heat and light and the natural cycles (like the wind, water flow and plant growth) that it powers. The solar energy that reaches the earth's surface is dissipated in different ways: about 15% is reflected back into space; 30% is used to evaporate water, which eventually creates rainfall; some is absorbed by plants, land and oceans…and the rest can be economically harnessed to meet our energy needs. Solar energy is abundant, everlasting, clean, easy-to-operate, cheap, has no negative impact on the environment and can be used as decentralised source of energy.
Solar radiation refers to the electromagnetic energy transmitted from the sun. The amount that reaches the earth is equal to one billionth of the total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours. Solar radiation—along with secondary solar resources such as wind and wave power, hydroelectricity and biomass—accounts for most of the available flow of renewable energy on Earth.
How is the power of solar energy tapped?
Different technologies have been developed to tap the sun's abundant energy. They range from small powering devices for computers to individual home systems to large-scale solar power concentrating systems. What they have in common is that all of them enable us to diversify our energy sources, improve efficiency, save money-and meet our energy needs in a green and sustainable fashion.
What is the difference between active and passive solar energy?
Based on method of usage, solar energy is classified into two categories: active and passive.
Active solar refers to solar energy that is directly converted into the form in which it will be used. Active solar energy systems need a solar collector to store energy and pump-connected controls or fans that draw heat from the storage source, as may be required.
Active solar is further classified into two categories: solar thermal and solar photovoltaic. Solar thermalrefers to usages based on a heating application: heating water and air, cooking and drying, distillation and steam generation are some examples. Technologies based on solar thermal include solar geysers, solar concentrators, solar cookers and solar stills. The second category, solar photovoltaic, is based on the generation of electricity. It uses solar silicon cells to convert solar energy to electrical energy, which can be used directly or through a battery storage system.
The term passive solar is used when the architectural design, natural materials, or absorptive structures of a building themselves are used as an energy-saving system. The building itself serves as a solar collector and storage device and the builder can reduce the needs for external energy outputs for lighting, heating and cooling, pumping of water and so on.
What does ' photovoltaics' mean?
Literally translated, 'photovoltaic' means 'electricity from light'. Photovoltaic systems use daylight (not necessarily direct sunlight) to convert solar radiation into electricity. Solar cells are one way to make this conversion possible.
How do solar cells work?
Solar cells convert light energy into electrical energy either indirectly (by first converting it into heat) or through a direct process known as the photovoltaic effect.
The most common types of solar cells are based on the photovoltaic effect. This happens when light falls on a two-layer semiconductor material and results in a potential difference, or voltage, between the two layers. The voltage produced in the cell is capable of driving a current through an external electrical circuit that can be utilised to power electrical devices.
Solar cells are usually made from silicon, which is treated to release electrons-thereby generating an electric current-when light strikes it.
Solar cell production increased by 50% in 2007, to 3,800 megawatts, and has been doubling every two years.
For a quick glimpse of how photovoltaic cells generate electricity,
go to http://www.youtube.com/watch?v=napVP6jAZxM&feature=related
What materials are used to produce solar cells? The most important material for solar cells production is silicon. At the time being, it is almost the only material used for solar cell mass production.
Gallium Arsenide (GaAs)-GaAs is used for production of high-efficiency solar cells. It is often utilised in concentrated PV systems and space applications. Their efficiency is up to 25%, and up to 28% at concentrated solar radiation. Special types have efficiency over 30%.
Cadmium Telluride (CdTe)-Thin-film material produced by deposition or by sputtering is a promising low-cost foundation for photovoltaic applications in the future. Lab solar cells' efficiency is up to 16%, while efficiency in the commercial types is up to 8%.
Copper-Indium-diSelenide (CuInSe2 or CIS)-Thin-film material has an efficiency of up to 17%. The material is promising, yet not widely used due to production-specific procedures.
go to http://www.youtube.com/watch?v=napVP6jAZxM&feature=related
What materials are used to produce solar cells? The most important material for solar cells production is silicon. At the time being, it is almost the only material used for solar cell mass production.
Gallium Arsenide (GaAs)-GaAs is used for production of high-efficiency solar cells. It is often utilised in concentrated PV systems and space applications. Their efficiency is up to 25%, and up to 28% at concentrated solar radiation. Special types have efficiency over 30%.
Cadmium Telluride (CdTe)-Thin-film material produced by deposition or by sputtering is a promising low-cost foundation for photovoltaic applications in the future. Lab solar cells' efficiency is up to 16%, while efficiency in the commercial types is up to 8%.
Copper-Indium-diSelenide (CuInSe2 or CIS)-Thin-film material has an efficiency of up to 17%. The material is promising, yet not widely used due to production-specific procedures.
Structure of a Solar Cell
A typical solar cell is a multi-layered material, comprising:
A typical solar cell is a multi-layered material, comprising:
- A cover layer of clear glass that provides outer protection from the elements.
- Transparent adhesive that holds the glass to the solar cell.
- An anti-reflective coating that is designed to maximise energy absorption by preventing the light that strikes the cell from bouncing off.
- Front contact that transmits the electric current.
- A thin N-type semiconductor layer made of silicon, doped with phosphorous.
- A second thin P-type semiconductor layer of silicon, doped with boron.
- A back contact that transmits the electric current.
What are the technologies used to make solar cells? Thanks to extensive research, many types of solar cells are now available. And new and different approaches-permitting a trade-off between lower manufacturing costs versus lower efficiency in converting sunlight to electricity-have it possible to reduce the costs of production.
There are three basic types of solar cell. Monocrystalline cells are cut from a single large crystal of silicon whilst polycrystalline cells are made from a number of crystals. The third type is the amorphous solar cell.
Monocrystalline Silicon
This type of solar cell uses a single layer of silicon for the semi-conductor. In order to produce this type of silicon it must be extremely pure-which means it is the most expensive type of solar cell to produce.
Polycrystalline Silicon
To make polycrystalline silicon cells, liquid silicon is poured into blocks that are subsequently sawed into plates. This type of approach produces some degree of degradation of the silicon crystals, which makes them less efficient. However, this type of approach makes manufacture easier and cheaper.
Amorphous (Thin-Film) Silicon
This type of solar cell uses layers of semiconductor that are only a few micrometers thick (about 1/100th the thickness of a human hair). While this lowers the material cost, it makes it less efficient than the other types of silicon. However, because it is so thin, this type of cell has the advantage that it can be placed on a wide variety of flexible materials in order to make things like solar shingles or roof tiles.
The manufacturing process for amorphous silicon photovoltaic modules is a third-generation technology based upon a highly successful and field-proven large batch approach to amorphous silicon deposition.
Incidentally, the term thin-film is based on the method used to deposit the film, not from the thinness of the film. Thin-film cells are deposited in very thin, consecutive layers of atoms, molecules or ions. Thin-film cells are also usually amenable to large-area fabrication and are suitable for automated, continuous production, arraying and packaging. They can also be deposited on flexible substrates.
What exactly is a SPV System?
The solar cell is the smallest unit of a Solar Photovoltaic (SPV) System. Solar cells are electrically connected to make solar or PV (photovoltaic) modules.
A number of solar cells joined in series and parallel make a module. PV modules are very flexible in their applications: they are portable, can be transported to different locations or can be used as a generating station for the utility. PV panels include one or more PV modules assembled as a pre-wired, field-installable unit. A number of linked panels make an array.
A combination of solar module(s) in series/parallel combination, storage battery, interface electronics, mechanical support structure, cable and switches, etc. constitute an SPV System. SPV systems can be used to provide electricity for lighting, water pumping, battery charging as well as for feeding power to the grid, etc.
SPV systems can be used for either centralised or distributed power generation. The fuel (sunlight) is free, and no noise or pollution is created from operating PV systems. In general, PV systems which are well designed and properly installed require minimal maintenance, have long service lifetimes and are very reliable. As abundant solar radiation is available in most parts of India, SPV systems can be used anywhere in the country. In addition, they are easy to install and yield quick savings on investment. However, it is necessary to store energy generated by SPV systems in storage batteries for use in non-sunshine hours.
Solar-generated electricity is most often fed into the electricity grid using inverters (grid-connected PV systems). In stand-alone systems, batteries are used to store the energy that is not needed immediately.
In 2007, installations of all photovoltaics increased by 83%, to bring the total installed capacity to 8.7 GW-and make grid-connected photovoltaic electricity the fastest growing energy source. Germany accounted for almost half this increase, followed by Japan.