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Making solar cells with a kitchen microwave – Prashant Sarswat and Michael Free (Inventors) – USA

For most people, experiments involving a home microwave typically don’t go much further than inflating a marshmallow like a balloon or reheating leftovers in plasticware – both with messy results. For metallurgists though, microwaves are sometimes employed to efficiently process metals, which is how researchers at the University of Utah found themselves using a secondhand kitchen appliance in their lab. Their resourcefulness paid off recently, when the team discovered a method for creating solar cell material with just a few basic ingredients and an old microwave.

The material is called CZTS after its components, copper, zinc, tin, and sulfur, and is known to act as a photovoltaic semiconductor, converting the sun’s rays into usable electricity. Scientists have only recently begun turning to it for use in commercial-grade solar cells, since its low-cost, environmentally friendly ingredients make it a perfect fit with green energy sources. Unfortunately, CZTS has been difficult to create properly in the past and usually requires more complicated methods involving chemical suspensions.

Prashant Sarswat and Michael Free, two metallurgical engineers at the University of Utah, devised a cheaper, faster method using a microwave rescued from a student kitchen. The pair dissolved acetate salts from each metal in a solvent of oleylamine and sent that concoction straight into the microwave (presumably after wiping away the splatter from months-old spaghetti sauce). After just 8 minutes, the nanocrystals needed to form CZTS began to take shape and reached equivalent sizes after 18 minutes, which isn’t bad compared to previous methods that required 45 to 90 minutes to prepare.

The resulting CZTS is suspended in an ink-like substance, which can be painted onto most surfaces or combined with other substances to build a functional solar cell. Sarswat and Free even built a small photovoltaic cell to prove their microwave-made CZTS would work. Leaving the CZTS in the microwave for specific times will also form different sizes of nanocrystals, giving the material different properties. Larger crystals absorb heat and convert it to electricity, while smaller crystals can be made to emit light at certain energy levels. The two researchers believe this could lead to LEDs that require less power.

With cheaper, less toxic ingredients than most semiconductors combined with an easier manufacturing process, CZTS is poised to become a widespread material in a number of industries. However, the research team has warned that most people should not try to concoct CZTS in their own microwave at home since, as your mother no doubt warned you, putting metal into a microwave can be dangerous.

Sarswat and Free also learned during the course of their study that a research team at Oregon State University was developing a similar microwaving method, though their process uses different chemicals. The pair of metallurgists are now performing further experiments to improve their process and find more applications for CZTS. Besides solar cells, they’ve also looked at possibly incorporating the material into biological sensors, hydrogen fuel cells, and electronic circuitry, though it’s still too soon to tell when or if any of these ideas will lead to a commercial product.

Source : University of Utah

Using solar power to keep truck drivers cool and saves fuel upto 1500 ltrs/year

A trio of companies has joined forces to develop a truck cabin air conditioning system that uses solar energy generated from panels on the trailer’s roof area for its power.

ICL Co Ltd, Mitsubishi Chemical Corp and Nippon Fruehauf Co Ltd co-developed the air conditioning system and the companies plan to conduct field tests of the i-Cool Solar system shortly. If the trials go well, we could see these units on highways in spring 2012.

The “i-Cool Solar” system stores electricity via the photovoltaic panels in special on-board batteries and uses the stored energy to power the cabin air conditioner when the truck is idle.

The system is made up of the i-Cool air conditioner from ICL, the installation mount for the PV panels from Nippon Fruehauf’s, and the PV cell modules from Mitsubishi Chemical.

The companies claim the i-Cool Solar can save roughly 1.8 liters of light oil per hour when the truck is not moving and reduce fuel consumption by about 1 percent when the truck is moving (based on calculations made on a standard 10 ton truck).

This results are fuel savings of around 1,500 liters of light oil per year.

The i-Cool Solar unit also makes it possible to operate other equipment on trucks, such as moving up and down the tail gate. The air conditioning system can also reduce the over-discharge of the storage battery which increases its lifespan.

A smaller version for use in cars is also in development.

Here comes the low-grade silicon for cheaper and more efficient solar panels – Australia

While we wait for affordable multi-junction solar cells that are pushing past the 40 percent conversion efficiency mark to make it out of the lab and onto our roofs, we have to make do with standard commercial silicon cells that currently max out at around 19 percent. A team from the University of New South Wales (UNSW) in Australia has found a way to improve the quality of low-grade silicon, enabling higher efficiency solar cells to be produced from cheaper, low-grade silicon.

It’s been known for several decades that hydrogen atoms can be introduced to help correct the efficiency-reducing defects and contaminants found in lower-grade silicon. However, researchers have had limited success in controlling the hydrogen to maximize its benefits. The solution found by the UNSW team relates to controlling the charge state of the hydrogen atoms.

Hydrogen atoms can exist in a positive, negative or neutral charge state, which determines how well they can move around the silicon and their reactivity, which is important to help correct the defects. The researchers say that by controlling the charge state, it will be possible to achieve higher efficiencies using lower-cost, low-grade silicon.

“We have seen a 10,000 times improvement in the mobility of the hydrogen and we can control the hydrogen so it chemically bonds to things like defects and contaminants, making these inactive,” says Scientia Professor Stuart Wenham from the School of Photovoltaics and Renewable Energy Engineering at UNSW. “This process will allow lower-quality silicon to outperform solar cells made from better-quality materials.”

Wenham expects to achieve efficiencies of between 21 and 23 percent using this new technique, which was patented by the UNSW team earlier this year. The researchers have attracted the interest of industry partners interested in commercializing the technology, and they are working with manufacturing equipment companies to introduce it into solar cell manufacturing processes.

Source : UNSW