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Tuesday, 01 November 2011 09:31

Renewable Sources Featured

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Renewable Sources

New emerging technologies for renewable energy   are many but of most of them are underdeveloped. These technologies include hot-idly-rock geothermal power, ocean power, and cellulosic ethanol (International energy, 2007). These technologies have not been widely been demonstrated and most of them are also not commercialized. What aim most interested in is the advanced thin film technologies used in the increasing of a sustainable power supply from photovoltaic energy. The expectation of this technology   is to resolve social problems and reinforce competitiveness through the provision of a cost effective PV modules which is a thin film which would substantially lead to an increases in sustainable energy supply contribution.

The largest PV production globally is from US, Japan, and Europe.The advanced thin film technologies are also known as the thin-film photovoltaic, cell   or the thin-film solar cell. A solar cell is developed from the deposit of one or numerous thin film/layers on substrates which has numerous photovoltaic materials. There is a wide range of thickness in the various layers from a few nanometers to other hundreds of micrometers.Photovoltaic materials of different varieties are deposited through different methods of depositation on a wide variety of substrates. The solar cells thin layers are grouped into photovoltaic material categories depending on how they are used.
Theses are the cadmium Telluride (CdTe),   thin film silicon (TF-Si) and Amorphous Silicon (a -Si), Dye-sensitized solar cell (DSC) and Cooper indium gallium selenide (CIGS). These silicon types show a twisted and dangling bonds which leads to deep defects of levels of energy in the bandgap and also the conduction and valence bands. These material are the ones which form solar cells which tend to have low efficiency of energy conversion compared to the bulk silicon which is also called wafer silicon or crystalline. These solar cells from conduction and valence material are however less expensive in their production.
The thin-film solar cells’s quantum efficiency is also lower because of the reduced level of charge carriers collected in each incident photon.The Amorphous silicon is made in a way which it has higher bandgap compared to crystalline silicon. This therefore means that it is able to absorb the part of the solar spectrum which is visible in a much stronger way compared the spectrum’s infrared portion. Since c-Si and nc-Si have the same bandgap, they can be combined in highly thin, layers to form a layered cell known as tandem cell. A a-Si top cell absorbs light which is visible and does not tamper with the infrared part in nc-Si bottom cell. In the past few years the various limitation seen in the thin –film silicon have been altered through the light trapping schemes which abliques the incoming light into the light transverses and into the silicon. The film continuously enhances the absorption of sunlight.
The silicon crystallinity is enhanced by the techniques of thermal processing   and eventually leads to the pacifying of electronic defects. The traditional PV panel is advantageous because they are low in weight but cannot be uplifted by the wind. Compared to other new technologies, the disadvantage is that it has reduced rate of efficiency and have increased cost of production.The potential and performance of the thin-layers materials is very high with increased efficiencies of up to 12%-20%. High efficiency is also seen in the module prototype with a percentage of 7% -13percent. There is also a range of 9% in its production module. The module efficiencies in the future is expected to rise to the level of modern way state of art of the best cells by 10-16% (Appleyard Renewable energy world, Com, 2009).  

Appleyard D (2009) Utility –Scale Thin Film: three new plants in Germany total almost 40MW. Retrieved from

On March 28, 2011

 International Energy Agency (2007). Renewable in global energy supply: an IEA facts sheet (PDF), OECD, p. 3.

 NREL (2009) learning about renewable energy. Retrieved from

On March 28, 2011

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