Start-up GreenRay Solar has raised money to finalize development of a solar panel that puts out household-grade alternating current, a technology that backers say will make solar power more accessible to homeowners.
The Westford, Mass.-based company said that it has raised $2 million from the Quercus Trust and 21Ventures, which will allow it to start production of its solar panels in the fourth quarter this year. Since its founding three years ago, the company had raised $3.5 million in state and federal clean-energy grants.
A microinverter and solar panel.
(Credit: EnPhase Energy)GreenRay's AC Solar Module will turn out electricity that meshes with household alternating current and voltage. Solar panels put out direct current, and then an inverter, typically placed in a home's basement or outside the house, converts the direct current to alternating current.
Instead of a large inverter for many panels, there are a number of companies developing microinverters that do the DC-to-AC conversion right on the panel.
This design simplifies installation and offers a number of other benefits, said GreenRay CEO Miles Russell. Cutting out the single inverter is safer because installers are dealing with lower voltages.
Microinverters also make an array deliver more reliable performance, say advocates. When one direct current panel is shaded, that drops the performance of all the panels connected to it. Also, it's easier to gather data on an array's performance, Russell said. GreenRay's panels will transmit performance data over the wires and transmit it to the Web via a gateway, he said.
Does this mean that installing solar panels is a do-it-yourself job? Russell said that very handy people could install GreenRay's 200-watt panel, but they are electrical appliances so require typical safety precautions and inspection.
"The do-it-yourself moniker is more of a long-term objective. You could imagine them at a Home Depot and they could be installed for an extra fee," he said.
Another advantage of AC solar panels is that a person could install only a few, rather than a full array, without the cost of an inverter. On the other hand, microinverters do add cost to a solar panel, which is one reason that microinverters have not been commercialized in the past.
Enphase Energy said on Tuesday that it has raised $15 million to ramp up production of its microinverters, a design that it claims significantly boosts the power output and reliability of solar panels.
Rockport Capital Partners led the series C financing, which was joined by existing investors Third Point Ventures and Applied Ventures, the venture capital arm of solar equipment manufacturer Applied Materials.
Enphase Energy's CEO Paul Nahi said the company raised money earlier than anticipated because it's seeing strong demand for its microinverters, which can improve the energy capture of solar panels by 5 to 25 percent.
The microcomputer, or PC, of solar inverters? Enphase's microinverter.
(Credit: Ephase Energy)Solar photovoltaic panels generate direct current from sunlight. An inverter, often placed on the side of a building, is needed to convert that direct current to the alternating current that comes out of electrical outlets.
Typically, one single inverter is dedicated to a rooftop array of panels for a homeowner.
Enphase Energy, by contrast, has built a DC-to-AC inverter that is placed on each single panel.
That design is more reliable than a centralized inverter and more efficient, so panels can generate more electricity, Nahi said. The company started shipping its microinverters earlier this year and has signed on with a number of panel distributors and installers, he said.
Enphase Energy also offers a Web service, where consumers can view performance of panels, helping them spot whether they are operating at full capacity or not.
Nahi predicted that there will be more decentralized inverter companies because of the benefits.
"There's been very little question on the benefits of microinverters, but people didn't think it was possible to get the efficiency levels required," he said. "A microinverter must be developed from the silicon level up to make it work efficiently."
Enphase Energy has been able to improve the DC-to-AC conversion efficiency to around 95 percent, on par with centralized inverters.
Texas Instruments on Monday launched a line of energy-efficient microcontrollers, which can be used for microinverters. Solar companies are investigating these because they can lower the overall system cost by easing installation and eliminating the cost of cables, said TI marketing manager Keith Ogboenyiya.
"Over the next six to nine months, we'll really see whether the microinverter concept will take off," he said.
Enphase Energy on Monday released a solar power system that takes a dramatically different approach to harnessing energy from solar panels.
With an inverter on every solar panel, owners can view performance of each individual module via the Web.
(Credit: Enphase Energy)The start-up company, which raised $6.5 million in funding earlier this year, has built a "microinverter" that converts a solar electric panel's direct current to alternating current on the panel.
Inverters are typically separate devices that are hung outside or in a basement. By placing an inverter right on a panel, Enphase Energy says that it is more efficient at converting light to electricity.
In addition, the microinverters give panel owners a better means for monitoring the performance of individual panels.
The company also has a gateway that transfers panel performance data which is displayed on a Web site.
The microinverter on a solar panel.
(Credit: Enphase Energy)Its design has garnered high praise from University of California at Berkeley professor Dan Kammen who is director of the Renewable and Appropriate Energy Laboratory. In a statement, he called microinverters "disruptive technology" and said, "I think this is, in some sense, the most important technological breakthrough solar has ever seen."
Solar installer Borrego Solar beta-tested the microinverter system at residential sites and intends to use it.
Is it time for a "small revolution" in the world of renewable energy electronics?
Start-up Enphase Energy on Tuesday announced that it has landed $6.5 million in funding with the bulk of the money coming from Third Point Ventures.
The company makes a system that uses a microinverter, an electronics device that converts direct current from solar panels to grid-ready alternating current on each individual panel.
Each panel can also relay information on its performance to Enphase Energy's Web site, which customers can view from a browser. The company plans to release the system, aimed at both businesses and consumers, in the second quarter of this year.
The result of the setup is a more productive and reliable solar installation, according to President and CEO Paul Nahi.
Typically, solar panels have a single inverter to convert DC to AC. A microinverter is more efficient, so each panel will harvest more energy, said Nahi. And having information on the performance of each individual panel will give the owner or manager of the array better information for troubleshooting problems, he said.
He declined to specify how much efficiency the microinverter design brings, but he said the move to microinverters is a "fundamental, basic" shift across the solar industry.
The idea of a solar panel that can generate alternating current has been around for a long time.
But there are a number of technical hurdles to microinverters, according to a presentation given by inverter maker Xantrex (click here for PDF). Those challenges include excessive heating, efficiency, and the ability to service inverters, according to Xantrex.
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