Concentrated PV

Chromasun and Cogenra are two companies forging an entirely new path in cogenerating electricity and hot water using low concentrating PV (LCPV) for commercial rooftops.

While the detail of their technologies differ, Chromasun founder Peter Le Lievre told PV-Insider that their products offer very similar benefits to customers, in providing both electricity and hot water. “You need to find customers who need electric power and hot water at the same time,” he says. “Now that’s not every body. But if you have a hospital or a university rooftop and you only put PV on it you’re throwing away 85% of the energy you could be collecting.”

Chromasun came from utility-scale CSP experience and developed the concept of generating both electricity and hot water on commercial rooftops from the frustration of trying to build large utility-scale CSP projects as Ausra, the company Peter Le Lievre founded in 2007 and sold to Areva in 2010 for $275m.

“We were operating in Australia and California, and we spent literally hundreds of millions of dollars in permitting and design, purchasing land and trying to get financing - it gets extremely expensive.”

“With utility scale you need to build a large plant and finance it from scratch; it’s very challenging,” he explains.

“Whereas on a rooftop, you can usually get a sale with a customer who not only owns the rooftop, and can give you permission to use it, but can often write a check for the system.”

Cogenra developed from a silicon background. PV-Insider also talked with Dr. Mani Thothadri of Cogenra, who told us that Gilad Almogy initially founded Cogenra as a purely CPV company.

He had left Applied Materials with the idea that active cooling of a CPV system would make more sense than using passive cooling using designs such as fins to radiate out the heat, where you are dependent on wind convecting the heat away, which would raise module costs.

While removing the heat had begun as an active cooling idea to increase electrical efficiency, it became the cogeneration that characterises the company, by allowing for additional income streams by “utilizing that waste heat and monetizing it.” Instead of relying on passive cooling, they created a hollow stack under the PV for active cooling to extract that heat.

“And then how we use that heat is what separated us, is that we use the heat as hot water. It is a very low hanging fruit.”

Learn as you go

The fundamental decision was made by Cogenra's CEO Gilad Almogy, "who is a brilliant man,” says Dr. Thothadri “to walk before we run.”

“With rooftops, the economics are very good and the projects are small so you can easily go out and find customers who are willing to pay cash, they are willing to try out new technologies.” As a result, within just twelve months Cogenra has racked up 30-plus projects, after their intial pilot project in Sonoma.

A key issue for the Silicon Valley-based Cogenra was having a managable learning curve - on their own dime. Doing many small projects made it possible to iron out the small issues that come up at a manageable scale, setting up the supply chain, the customers, as a revenue-based company, where “we are not burning up someone else’s money.”

Low cost learning

“With any product,” Dr. Thothadri explains, “there are always going to be small issues, nothing fundamental, but a lot of these little things come up. If you go right away to a very large project, if you are trying to solve these, they’re no longer small, having to fix even a small issue at megawatt scale, can mean a big problem.”

“What happened with all the CPV guys is that they would have all the technology they would prove in their back yard then go out and get a 10 MW project PPA [power purchase contract with a utility] and start building.”

With such a large jump, “every small issue becomes a big one, with all the nightmares, so a lot of projects never got off the ground, or solved all the issues. They were never able to benefit from the scale and the cost curve that would come from just implementing more projects.”

As well as starting small, both chose to go with low concentrating PV. Cogenra concentrates just 8-10 suns, though CPV companies can go up to 500 suns.

“A lot of CPV players are going HCPV, so they can’t use standard silicon. Gallium arsenide cells work better when you’re putting a lot of suns on them - but they’re more expensive, so you need to go high concentration to extract all the energy, so you must have exact tracking accuracy, so your tracking costs increase, and you have to find a way to cool that, so all your costs go up.”

Standard manufacturability

Chromasun is having parts manufactured locally by a tier one automotive supplier (for Toyota) in Australia that is tooling-up to make their modules.

“A car seat is made of metal and electrical parts,” Le Lievre points out. “Our product is metal, glass and electrical parts, so basically these panels are medium technology to manufacture. They don’t require a million dollar factory to put into production. They are a fairly straightforward fabrication.”

No trailblazing

Almogy’s idea was based on standard PV. China was already driving the costs down, so his thought process was that somebody else could spend and do all the hard work, the efficiency improvement, and fights in the marketplace to drive down costs.

“The thing with standard silicon cells is it’s being produced by everybody. It’s available. I come from a semiconductor background, so does Gilad,” points out Dr. Thothadri, who had a similar engineering focus as Dr. Almogy at Applied Materials. “And from that background you never bet against silicon.”

“Just when you think it has hit a brick wall they come up with something or other - and boom. And it is very low cost so it’s just the easiest way to do things.”

Chromasun gave similar reasons for using off-the-shelf PV with silicon, which is why both technologies are low concentrating.

“Silicon is limited by its bandwidth characteristics,” explains Dr. Thothadri. “It is limited to a certain amount of current, or the number of electrons that you can make jump from one bandgap to another.”

However, the trade-off of using low concentrating silicon is low cost. Both technologies wring two to three times more energy from the “low hanging fruit” thermal side. “We are working with a five star hotel in Hawaii that has a $50,000 a month propane bill for hot water, so they are very keen to use solar to reduce those bills, and they are the perfect customers for us,” says Le Lievre.

Both concentrate enough to increase the electrical side efficiencies (20-25% for Cogenra) but not so much that no one can afford their systems - so they wouldn’t get enough repeat business to ever “walk before they can run.”

Le Lievre concedes he will be very happy if he does $10m this year:“I think we’re both trying to unlock a new market together. We wish Cogenra all the best to be very successful. I think we will be too.”