April 20, 2012

Competing systems for wearable solar power

Business Week - Miles Barr wants to make curtains, cell-phone cases, and even shirtsleeves that generate electricity from the sun.

Chemical vapor deposition changes the quality of a surface without using extreme temperatures or solvents that might cause damage. When Barr’s team at MIT figured out how to use the process to make solar cells, he says, they went to an office supply store and loaded up on stuff to test it on: “Saran Wrap, copy paper, tissue paper, almost anything you can imagine,” he says. Barr maintains the technique could be adapted for mass production. Because it relies on abundant organic molecules, rather than heavy metals or rare elements, it could be cheap, too. Right now, Barr’s solar cells convert only about 2 percent of the energy in light into electric power, compared with 10 percent to 20 percent for conventional photovoltaic panels, though he thinks he can eventually raise the efficiency to 10 percent.

Last year, Barr co-founded Ubiquitous Energy to embed solar technology into everyday objects such as windows or cell phones, which could be particularly suited to people living off the grid. Ubiquitous Energy has gotten $1 million in Angel funding.

The cost of installing panels keeps many people from adopting solar power, Barr says. By integrating it into ordinary materials, he thinks he can clear that hurdle. “You’re already hanging a curtain in your house,” he says. “Why not add some energy to that?”

Miles C. Barr received the prestigious $30,000 Lemelson-MIT Student Prize for his innovative solar technologies and creativity.

To succeed it must promise low enough cost and low enough sensitivity to humidity. Other attempts to create printable solar cells have been criticized for failing to meet these criteria.

Competing solar technology

There are many competing technologies and companies trying to develop cheap and wearable solar power.

Researchers have developed flexible, stretchable polymer-based solar cells on plastic foil substrates thinner than spider silk and able to generate 10 watts per gram.

Cooperation between scientists at the Johannes Kepler University Linz (JKU) in Austria and the University of Tokyo led to the development of the cells, which are over ten times thinner, lighter and more flexible than any other solar cell of any technology to date.

The new cells can attain a 4.2% power conversion efficiency and tensile strains of more than 300% on an elastomeric support.

The substrate used for the cell is a commercially available form of Mylar 1.4 CW02, a form of PET film. The total device is only 1.9 microns thick and around one-quarter of the thickness is the active solar cell.

MIT Wearable Solar

The basic process is essentially the same as the one used to make the silvery lining in your bag of potato chips: a vapor-deposition process that can be carried out inexpensively on a vast commercial scale.

The resilient solar cells still function even when folded up into a paper airplane. In their paper, the MIT researchers also describe printing a solar cell on a sheet of PET plastic (a thinner version of the material used for soda bottles) and then folding and unfolding it 1,000 times, with no significant loss of performance. By contrast, a commercially produced solar cell on the same material failed after a single folding.

Thinner than Spider Silk Solar

Military Projects to incorporate solar and thermoelectrics into uniforms

In 2011, there was a two year project in the UK for a combination of solar photovoltaic (PV) cells, thermoelectric devices and leading-edge energy storage technology will provide a reliable power supply round-the-clock, just like a normal battery pack.

We aim to produce a prototype system within two years,” says Professor Gregory. “We also anticipate that the technology that we develop could be adapted for other and very varied uses. One possibility is in niche space applications for powering satellites, another could be to provide means to transport medicines or supplies at cool temperatures in disaster areas or to supply fresh food in difficult economic or climatic conditions”.

Researchers at the Australian National University in Canberra devised wearable solar panels capable of powering electronic equipment in the field. The flexible, paper-thin cells, aptly dubbed “sliver,” can generate up to 140 watts of power. Transform solar provides the solar cells Monocrystalline solar cell technology is in the 15-25% efficiency range.

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