Well, once you start looking at the options with solar energy things look pretty rosy right? I mean in ten years from now a third of the produced energy will be solar or otherwise green ( wind power, biomass… ). Most building will be energy self suficient with those fancy dyes on every window and spray-on solar cells everywhere. Right? Well not quite. Everything looks fine until you realize that to produce solar cells NF3 is used. NF3 or nitrogen trifluoride is a gas thats used in the production of LCD displays and solar cells. Unfortunately it is also a very potent green house gas.
Fortunately The Linde Group a world leading producer of gasses has found out that NF3 can be replaced with fluorine gas. Fluorine has no effect on the green house effect and its readily available. On top of that it also speeds the production process thus lowering the costs of solar cells altogether.
For the in detail story click below:
http://www.marketwatch.com/news/story/making-lcd-tv-solar-cell/story.aspx?guid={96198A7A-9B93-43DF-BF35-D7C74148E3F5}&dist=hppr
One of the big problems of solar energy has always been availability. There’s no sun on a cloudy day or at night. The solution would be to store the suns energy and use it when the sun is not available. Storing elecrticity in such quantities is very expensive. Another solution would be to use the electricity to produce hydrogen that can be latter used to produce electricity again. This process is not very efficient and storing hydrogen is both expensive and dangerous.
The proposed solution is to store heat which is both cheap and effective. The accumulated heat can later be used to produce electricity when it is needed.
The system uses an array of mirrors that reflect the sun’s heat onto a tank of water. The produced steam turns a turbine. Really simple – a good old fasioned steam engine. This works even at night because water can store heat for a long time.
A new invention that would allow domestic window to function as solar panels was recently invented by scientist at MIT in Boston. The real invention is a special coat that aplied to the windows conducts some of the light to the edges where the solar cells are. This has several advantages it allows for smaller solar cells lowering the cost of the installations, concentrates the light raising the eficiency as the solar cells are more eficient at higher light intensities. Another major saving is the unobtrusive installation that requires just a coat of the revolutionary material thus eliminating the need of expensive roof mounted panels or concentrators that need further cooling.
In 2007 a plan has been laid out to that would benefit both North Africa and Europe. The plan starts in northern Africa in coutries such as Morocco, Algeria and Libya where an immense array of solar cells is to be deployed in the Sahara desert. The electric power produced by the cells will then be conveyed to Europe via undersea cables. Some residual power will be available to the countries hosting the solar cells for desalinization of sea water, thus providing said countries with much needed fresh water.
The plan seems to address and exploit some interesting aspects. Mostly it taps into the endless supply of solar power available in the desert. Lets also consider that the weather in the desert is almost always sunny. The land in the african desert is cheap while very expensive in Europe.
Another more technical aspect of solar cells in the desert is the fact that at night the desert also radiates heat back into the atmosfere, heat that could be absorbed by the newest spray on and converted into electric power providing a steady supply even at night.
One of the breakthroughs in the field came in late 2005 with the invention of a plastic solar cell that can be sprayed on other materials to form a very versatile source of energy. One can envision the material being sprayed on cell phones, laptops, cars … giving the devices true independence from wires and recharging. Larger scale implementations could be the use of the spray to cover entire buildings or even unused land such as deserts to provide an abundant green source of renewable energy.
Scientists are expecting to improve on the efficiency of the plastic cells by harnessing the infrared part of the sun’s light, which represents about 50% of the total light that reaches the earth and which other solar cells cannot use to produce electricity. Another benefit of this aspect is the possibility to use the cells in cloudy weather or even at night in warm climates as infrared light is actually heat.
With greater efficiency come lower costs. Solar power is infact 3-5 times more expensive than the average U.S. residential power costs. The spray on power cells may finaly brige this gap and bring solar power to the mainstream.
The photovolataic effect is the means by which the photovoltaic cells ( the first generation of solar cell ) are able to transform sunlight into electricity.
A photovoltaic cell is made from a thin slice of semiconductor, usually silicon or galium-arsenide. Two special types of impurities called dopants are added to the semiconductor. The upper and lower part of the slice become respectively a p-type and n-type semiconductor. The n-type has a surplus of electrons while the p-type has a lack of electorns – also called “holes”. This electron imbalance forms an electric field in the semiconductor slice.
When an electron is hit by a photon it becomes free of the p-n structure leaving a “hole” or positive charge behind. Being in an electric field he negative electron and the positive “hole” begin to move in oposite directions creating an electric current. If we connect wires to the semiconductor we can run this current through a load ( light bulb, battery charger, etc ).
Of course not all the photons hit the electrons in the solar cell. Some light bounces right off the cell and some misses the electrons and passes right through. Also the semiconductors used today are able to absorb just about half the spectrum of sunlight, further limiting the efficiency of cells.
The efficiency of photovoltaic cells can be raised using different combinations of semiconductors to try to absorb the whole length of the sun’s specturm and also use thicker slices with more p-n junctions to catch the photons that pass thorough the first junction.
Many of us might thing that solar cells are something new and cutting edge. Well the truth is that they have been around for decades. The buzz surrounding them now is caused mainly by the soaring gas prices and the green movement in general. The solar cells technology is at its third generation.
The first generation the classic photovoltaic silicon based cells still represents more than 80% of all the installations. They are highly effective but bulky and expensive.
The second generation tries to address the shortcomings of its predecessors. The lightweight and flexible thin-film solar cells are very low cost. They can be arranged in many different ways making their use much more suitable for urban settings. Despite their lower efficiency they are expected to dominate the solar market in a few years.
The third generation of cells are actually a group of technologies that are still being researched. The research is directed towards new materials like polymers and nanotechnology and away from silicon-based materials. The idea is to merge the flexibility and low cost of the thin-film cells and the effectiveness of the classic silicon based cells. I will try to cover the new technologies in a later post.
