[Vision2020] Good solar news

[Kenneth Marcy]

Stacking Cells Could Make Solar as Cheap as Natural Gas

http://www.technologyreview.com/news/529651/stacking-cells-could-make-solar-as-cheap-as-natural-gas/ 


A novel manufacturing method could make it practical to stack solar 
cells and convert more of the energy in sunlight into electricity.

By Kevin Bullis 
<http://www.technologyreview.com/contributor/kevin-bullis/> on August 6, 
2014

When experts talk about future solar cells, they usually bring up exotic 
materials and physical phenomena. In the short term, however, a much 
simpler approach---stacking different semiconducting materials that 
collect different frequencies of light---could provide nearly as much of 
an increase in efficiency as any radical new design. And a new 
manufacturing technique could soon make this approach practical.

The startup Semprius <http://www.semprius.com/>, based in Durham, North 
Carolina, says it can produce very efficient stacked solar cells quickly 
and cheaply, opening the door to efficiencies as high as 50 percent. 
(Conventional solar cells convert less than 25 percent of the energy in 
sunlight into electricity.)

Semprius has come up with three key innovations: a cheap, fast way to 
stack cells, a proprietary way to electrically connect cells, and a new 
kind of glue for holding the cells together. In its designs, Semprius 
uses tiny individual solar cells, each less than a millimeter across. 
That reduces costs for cooling and also helps improve efficiency.

The conventional way to stack semiconductors is to grow layers on top of 
each other. But not all semiconductors can be combined this way, because 
their crystalline structure doesn't allow it (see "Adaptive Material 
Could Cut the Cost of Solar in Half 
<http://www.technologyreview.com/news/529476/adaptive-material-could-cut-the-cost-of-solar-in-half/>"). 
Semprius grows semiconductor materials in the conventional way but also 
stacks several different combinations, resulting in a solar panel that 
can capture more energy from sunlight.
Semprius has demonstrated cells made of three semiconductor materials 
stacked on top of a fourth solar cell that would not have been 
compatible otherwise. It has made two versions of the device this year, 
one with an efficiency of 43.9 percent and the other, using slightly 
different materials, with an efficiency of 44.1 percent.

In addition to being fast and precise, the approach also makes it 
possible to reuse the expensive crystalline wafers that multijunction 
solar cells are grown on. Eventually the company hopes to stack two 
multijunction devices, for a total of five or six semiconductors with a 
"very high performance, beyond 50 percent efficiency," says Scott 
Burroughs <http://www.semprius.com/company/leadership.html>, vice 
president of technology at Semprius. He says the company hopes to 
achieve this in three to five years.

The one catch is that the cells will be more costly than conventional 
ones. Sarah Kurtz 
<http://www.nrel.gov/pv/performance_reliability/research_staff.html#Kurtz>, 
a principal scientist at the National Renewable Energy Laboratory, says 
costs won't come down until production happens at a large scale.

With economies of scale, however, such cells could improve the economics 
of solar power. At a scale of 80 to 100 megawatts a year of 
manufacturing capacity, a cell with 50 percent efficiency would make it 
possible to reach costs of less than five cents per kilowatt-hour, 
Burroughs says. The U.S. Energy Information Administration estimates 
that new natural-gas power plants will produce electricity at 6.4 cents 
per kilowatt-hour.

http://www.technologyreview.com/news/529651/stacking-cells-could-make-solar-as-cheap-as-natural-gas/ 



Ken

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.fsr.com/pipermail/vision2020/attachments/20140817/bcd8ad13/attachment.html>