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Nature provides answers to better solar energy systems

We found this article published by Energy Harvesting Jouinal on 20th August 2012. It just goes to show that “Nature knows best.” We can find the answers to our solar energy challenges if we study nature.

Sunflowers inspire more efficient solar power system

A field of young sunflowers will slowly rotate from east to west during the course of a sunny day, each leaf seeking out as much sunlight as possible as the sun moves across the sky through an adaptation called heliotropism.

It’s a clever bit of natural engineering that inspired imitation from a  University of Wisconson-Madison electrical and computer engineer, who has found a way to mimic the passive heliotropism seen in sunflowers for use in the next crop of solar power systems.
Unlike other “active” solar systems that track the sun’s position with GPS and reposition panels with motors, electrical and computer engineering professor Hongrui Jiang’s concept leverages the properties of unique materials in concert to create a passive method of re-orienting solar panels in the direction of the most direct sunlight.
His design, published in Advanced Functional Materials and recently highlighted in Nature, employs a combination of liquid crystalline elastomer (LCE), which goes through a phase change and contracts in the presence of heat, with carbon nanotubes, which can absorb a wide range of light wavelengths.
“Carbon nanotubes have a very wide range of absorption, visible light all the way to infrared,” says Jiang. “That is something we can take advantage of, since it is possible to use sunlight to drive it directly.”
Direct sunlight hits a mirror beneath the solar panel, focused onto one of multiple actuators composed of LCE laced with carbon nanotubes. The carbon nanotubes heat up as they absorb light, and the heat differential between the environment and inside the actuator causes the LCE to shrink.
This causes the entire assembly to bow in the direction of the strongest sunlight. As the sun moves across the sky, the actuators will cool and re-expand, and new ones will shrink, re-positioning the panel over the 180 degrees of sky that the sun covers in the course of the day. “The idea is that wherever the sun goes, it will follow,” says Jiang.
In Jiang’s tests, the system improved the efficiency of solar panels by 10 percent, an enormous increase considering material improvements in the solar panels themselves only net increases of a few percent on average. And a passive system means there are no motors and circuits to eat into increased energy harvest. “The whole point of solar tracking is to increase the electricity output of the system,” says Jiang.
The materials driving Jiang’s design have only been available in the past few years, so for now, he and his team are researching ways to refine them for use driving larger solar panels, where the net energy gain from his system will be the greatest.
But eventually, Jiang hopes to see huge industrial solar farms where fields of photovoltaic solar panels shift effortlessly along with the sunflowers that inspired him. “This is exactly what nature does,” says Jiang.
Source:  University of Wisconson-Madison


You can read the original article here Sunflowers inspire more efficient solar power system

Posted in Energy Saving Devices, Home Energy News, Solar Panels, Solar Power For Homes0 Comments

Solar panels from cheap copper oxide

We found this interesting article by By on August 10, 2012 at 1:10 pm published on

Hopefully the price of solar panels will be coming down further.

So long, silicon: Researchers create solar panels from cheap copper oxide

Researchers from the University of California and Berkeley Lab have discovered a way of making photovoltaic cells out of any semiconducting material, not just beautiful, expensive crystals of silicon. In principle, this could open the doors to much cheaper solar power.

Almost every solar panel on the market is made by cutting off two thin (200 micron, 0.2mm) slices from a large crystal of silicon, and then doping them with impurities to enhance the photovoltaic effect — phosphorous to make n-type silicon, and boron to make p-type silicon. These slices are layered together, electrodes are added to the top and bottom, the whole thing is framed in protective glass — and voila, a standard photovoltaic cell.

Now, in theory, you can dope any semiconductor — but cheaper, more-readily-available semiconductors, such as copper oxide, don’t retain dopants very well, eventually leading to the breakdown of the p-n junctions. Silicon holds dopants very well, but it isn’t cheap.

To get around this problem, the Californian researchers have developed a new type of solar cell called screening-engineered field-effect photovoltaics, or SFPV for short. Instead of physical doping, SFPVs use a minute electric field to achieve the same doping effect. While this electric field is present, the p-n junction remains and the photovoltaic cell continues to produce a lot of electricity. The energy required to produce this electric field is apparently a lot less than the energy produced by the photovoltaic effect.

The electric field effect isn’t new (you may have heard of field-effect transistors?), but its application in photovoltaic cells is novel. The main problem that the UoC and Berkeley Lab researchers came across is that you need a contact above the semiconductor to deliver the electric field — but of course that obscures the semiconductor from sunlight. The solution devised by the researchers is simple: You either use a very thin contact, like graphene (which is transparent), or you use a series of narrow, fin-like contacts (pictured above).

What’s next? “This research opens up scores of new semiconductors (many metal oxides, sulfides, and phosphides) for practical photovoltaic applications, so we are currently identifying the ones with the greatest potential for low-cost, high-efficiency solar cells,” says Will Regan the lead author, to Ars Technica.

Once the best material has been found, it still won’t be an easy ride: there’s a huge industry (mainly in China) dedicated to producing standard photovoltaic cells, and they lack the equipment or expertise to produce SFPVs. It isn’t quite as bad as the computer chip industry, where trillions of dollars are invested in silicon, but it will still take considerable effort to shift the industry towards SFPVs. The cost savings are there for the taking, though — and I dare say, the first company to produce solar power that’s significantly cheaper than fossil fuels is onto a winner.

Read: Solar panel made with ion cannon is cheap enough to challenge fossil fuels

Research paper: DOI: 10.1021/nl3020022

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Why Home Energy Saving Devices are Important

Why Home Energy Saving Devices are Important

All of the appliances employed at home contain the so-called switch wherein there are the on and off indicators. To run the home appliances, they need to be switched on. On the other hand, when they are no longer in use, they must be switched off. There is this fact which most homeowners do not realize though. Continue Reading

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Home Energy Saving Devices

Home Energy Saving Devices

If your electric meter is spinning as fast as slot machines for as long as you can remember, then today is the right time to be concerned. You are paying large on electric bills month after month right? And you are still trying to figure out how will you be able to lower down your energy cost to somehow make paying easier for you. Continue Reading

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