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Solar CPV: Could less be more?


Mark Halper

Hypersolar Wants to up the concentrated solar PV ante with a low magnification technology. Could this be CPV for the masses, or has the game already passed the company by?

When concentrated photovoltaic start-up HyperSolar Inc. announced in February that it had designed a magnification sheath that tripled the intensity of sunlight in a solar panel, curious observers wondered, “so what?”

After all, other concentrated solar PV (CPV) companies claim concentration of 500-times and more. REhnu, the Tucson, Arizona company run by University of Arizona Roger Angel (professor of astronomy and optical science), reports 1,200 times concentration. This is a level that can purportedly melt steel - using large reflectors, fancy ball lenses and optics inspired by Angel's prize-winning work on telescopes.

If Angel can perform such Herculean feats, why should anyone care about the three-times claim made by Tim Young, CEO of Santa Barbara, Calif.-based HyperSolar?

The answer, to paraphrase Young, is that HyperSolar epitomises the maxim “less is more”. Not only does his low magnification – the “less” - potentially slash costs and improve panel efficiency, he explains, it does so by bringing CPV into the mainstream.

It works with the standard silicon solar cells that make up the vast majority of today's photovoltaic installations – the “more”. HyperSolar does not require the costly, highly-efficient “multiple junction” gallium arsenide solar cells typically deployed in the high concentration products made by the likes of REhnu, Amonix Inc., Concentrix Solar GmbH, and SolFocus Inc.

Nor does it rely on specialised and bulky components that can add cost and complexity, such as mechanical trackers, mirrors or large lenses.

Rather, HyperSolar has designed a thin plastic layer that coats a traditional solar panel. The entire layer, rather than individual cells, collects light through tiny plastic lenses called “micro concentrators”, and routes it through “light pipes” to silicon solar cells.

You could call it the common man's concentrated solar PV:

“Because of the preponderance of silicon solar cells, if you can make the silicon more efficient and cheaper using a low concentration technology, you really have something that's a game changer,” says Young. “Our goal is to make solar power less expensive so it's more widely used, by cutting down the number of expensive silicon solar cells and replacing them with our concentrator layer.”

Young claims that 300% magnification will allow solar panel makers to reduce the number of solar cells they use by 66%. A 400% boost – which he is optimistic he can achieve - would cut the number of cells by 75%. Solar cells represent 80% of the cost of a panel, so the potential cost savings are significant, notes Young.

But will his numbers really work out?

The economic trick in any CPV system is to ensure that the added costs of magnification are less than the cost of the replaced solar cells. “To justify the concentrator approach, the cost savings from using less of the cell has to outweigh the additional cost, complexity, and power losses from the optics and associated tracking,” notes Daniel Friedman, manager of the III-V multi-junction solar cells group at the National Renewable Energy Laboratory in Golden, Colorado.

Young thinks he'll achieve that. By cutting out 66% of the solar cells, he'd slash the cost of a panel by 53%. The ceo of the publicly traded company conservatively notes that even if HyperSolar reduces the solar cell count only by half, it would still reduce panel costs by 40%.

The entire layer, rather than individual cells, collects light through tiny plastic lenses called ‘micro concentrators’, and routes it through ‘light pipes’ to silicon solar cells. You could call it the common man’s concentrated solar PV.
 

But how much cost would HyperSolar then add with its magnification layer?

“Our goal is that our layer will be significantly less expensive than the silicon,” says Young. “If we add 10% back in with our layer, you're still looking at a 30% cost reduction,” he notes. And that's his most conservative forecast.

He's not willing to state yet what his cost will be, or how much HyperSolar-enhanced panels will cost per watt to manufacture – the defining economic metric in any renewable quest to supplant fossil fuels by reaching “grid parity” with them.

One reason Young won't commit is that the technology is still in development. What HyperSolar announced in February was completion of a prototype design, not an actual prototype. It has yet to finalise key manufacturing and materials decisions. As this story was going to press, the company was choosing between three manufacturers to make the prototype - two in California and one in New York state.

It had also not yet decided on exactly what material to use for its magnification layer. Although Young was reasonably certain he'll use a polymer, he had not ruled out glass. Possible suppliers include Frankfurt, Germany-based TOPAS Advanced Polymers. Young hopes to have a prototype by early summer, and to offer a commercial product within 18 to 24 months.

Obviously, HyperSolar must cross a number of hurdles before it popularises low concentration solar PV. For one, it faces stiff competition against other solar PV and renewable vendors. Those include other low concentration solar PV providers, who, unlike, HyperSolar, are already shipping.

Solaria Corp., Fremont, Calif., and Skyline Solar, Mountain View, Calif., among others, already offer products in the low magnification business – Solaria at 2× and 3×, Skyline at 10×. Like HyperSolar, they also use conventional crystalline solar cells, although both modify the cells. Solaria, for instance, cuts them into strips.

But whereas both Solaria and Skyline use trackers to keep solar cells pointed at an optimal sun angle, HyperSolar has eliminated trackers. Instead, it uses the entire surface of its concentrator layer to collect sunlight.

“Sunlight doesn't have to hit the cell directly,” says Young. “We're expanding the collection area of a solar cell in order to collect and transport more light onto it.” The company bases its design on technology developed by its chief scientific advisor and University of California Santa Barbara professor Nadir Dagli.

Even if HyperSolar is able to trump other low concentration solar PV vendors, it still faces the general problem that confronts all concentrated solar PV manufactures: compared to other forms of solar-generated electricity, the technology is unproven. It remains a minute fraction of all installed solar generated electricity.

HyperSolar will have to be exceedingly low cost to compete against the standard silicon panels coming from China at steadily declining prices.
 

According to Brett Prior, an analyst with GTM Research, CPV installations were well below 1% of the 13 Gigawatts that the U.S. Energy Information Administration said was installed globally in 2008, which itself was only 0.3% of the world's installed generating capacity (2008 is the last year for which EIA had reported international figures by press time). Prior says total installed CPV capacity today is around 25 MW, barely a scratch in the world's total.

As Prior notes, CPV is characterised by a lack of standardisation, and HyperSolar's technology is yet another new approach. It remains unclear how reliable and effective the company's magnification layer – with its novel “light pipes” – will be.

“You need bankers and equity guys to put money in, but they don't want to if they're worried it's going to break down,” says Prior. Even if companies like HyperSolar offer guarantees, power providers will almost certainly insist that they buy warranty insurance to cover against breakdown, much like SolFocus purchased from insurer MunichRe last October.

Prior claims that CPV is already the lowest cost of all solar technologies, at around US$0.12 per kWh, on a levelised cost of electricity basis, and yet it remains a “a challenged space” because of its unproven status. It has also lost one of its imperatives: developers rushed to it several years ago during a silicon shortage that has since abated, he notes.

And some people just don't buy the “less is more” benefit of low concentration solar PV. One doubter is Roland Winston, professor at the University of California Merced, and director of the University of California Advanced Solar Technologies Institute, research collaboration between the University's Merced, Berkeley, and Santa Barbara campuses. He claims that high concentration solar PV, using advanced optics and highly efficient multi-junction cells, is the only way to go in the long run, especially as optical prices decline. “Anything else is either misleading, hype or transient,” he says.

Meanwhile, HyperSolar will have to be exceedingly low cost to compete against the standard silicon panels coming from China at steadily declining prices. “The cheap panels from China are really creating a very challenging price situation,” says Winston.

But Young is hopeful. “We're taking low concentration technology and applying it to traditional infrastructure,” he says. He believes HypserSolar will hit a sweet spot by vastly improving the cost/performance of traditional solar panels, rather than re-inventing the wheel. He just has to hope that the market hasn't passed him by the time he rolls into it.


About:

Mark Halper writes for TIME and Fortune magazines, covering many aspects of clean energy.


Renewable Energy Focus, Volume 12, Issue 2, March-April 2011, Pages 10-12

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Photovoltaics (PV)  •  Solar electricity

 

Comments

Anumakonda said

09 July 2011
Good move by Hypersolar to bring CSP to developing countries at an affordable price.

Dr.A.Jagadeesh Nellore(AP),India
Wind Energy Expert
E-mail: anumakonda.jagadeesh@gmail.com

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