An inverter in every solar panel?

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.

[Joe Real]

One of the reasons why microinverters in every panel helps in a very big way is the fact that shading on some of the panels will not stop the entire group of panels from generating electricity.

The main disadvantage of using a centralized inverter for a group of solar panels is that when the panels received 10% shading, the whole group will not produce electricity. The microinverters overcomes this limitation, for example in situations that you have protruding chimneys or trees that could shade some of your panels.

The question remains, how reliable are the microinverters? We already know that the regular central inverters conk out in 10 to 12 years and needs to be replaced. Solar Panels on the other hand are known to last more than their lifespan of 25 years. The regular inverters while tucked in weather protected garage, and they only last 10 to 12 years, 15 years if you're lucky. These microinverters are silicon based and perhaps able to survive the extreme weather conditions in the rooftop.

[tech_crazy]

Wonderful! AC outputs from the various panels is now going to be even harder to gang together thanks to phase now adding to the equation!

[joelnwil]

"Enphase Energy's CEO Paul Nahi said the company rose money ..."

Is there an editor? Does this stuff ever get proof-read? It is rise, rose, risen, intransitive verb. It is raise, raised, raised, transitive verb. Look them up at dictionary.com.

[mlamonica]

you're right. I corrected the verb to raised.

[William Crow]

Just for grins...I hope these microinverters last longer than my "energy saving" folded fluorescent light bulbs that, though they save energy in the short run, burn out quickly based on how often I turn them on and off. If you never turn them off they may last 10 times longer than normal lightbulbs, but with normal use maybe 2 times longer. I prefer not to burn a bulb 24 hours a day.
So I end up spending 20 times as much for the folded fluorescent that lasts maybe twice as long. Then I have to drive to a special location to discard it.

Don't get me started on the story about the "Environmentalist (capital 'E') with the giant flat screen TV."

I'm all for it but feel we have a ways to go to make real energy savings occur.

[Manhattan2]

Why are we trying to lower the cost to the homeowner? There will always be a better solution no matter what the cost becomes. The planet must come first. Solar will be the answer to many of our problems but not done this way.

[Brent_Norris]

I missed the cost? True that ac can run longer lengths but we can go 48 volt for efficiency, no? I've never heard of shading causing all the panels to stop producing power, so what do I know? I can barely read. I even missed the obvious typo.

[carlhage]

Besides Joe Real's note about extracting peak power optimized per panel, it seems that there might be a cost advantage per watt for smaller transistors. Consider a 500W UPS (with battery) costs <$50 but a 3KW grid-tie inverter costs about $3000-- a 10X difference in price. I'm not sure how much is economy of scale, but it seems the lower power units like a UPS are cheaper per watt.

Also, inverters located near the panels mean a lot more flexibility in connecting and expanding panels, since you just have a common 240VAC (or whatever) cable to run. Otherwise there is some complex series-parallel configuration of connections and feed wiring.