Clean Power rotary converter

Published on May 19th, 2014 | by Jake Richardson


$1 Million Dollar Prize Offered By Google For Better Solar Power Inverters

May 19th, 2014 by  

An Emphase Micro-Inverter

An Enphase Micro-Inverter

Called the Little Box Challenge, Google announced recently that it will be offering a $1 million prize for inventing much smaller solar power inverters. The challenge will be launched this summer, so currently few details have been released to the public.

Note that Google Ventures is an investor in Transphorm, a company that doesn’t make solar inverters but is trying to make gallium nitride more efficient to reduce energy loss in solar inverters, motor drives, power supplies and servers.

Interestingly, an article on Greentech Media appeared to take some issue with focusing on inverter size, “The big question, said Shiao, is whether it’s wise to concentrate on the size of the inverter, rather than on what it’s capable of doing. Inverter materials now make up less than 10 percent of overall solar system costs, meaning that any innovation in this area would likely have a negligible impact on overall cost. Adding smart features and functionality to inverters, on the other hand, could lower integration and installation costs, improve monitoring and maintenance, and lead to a slew of potential revenue-generating opportunities in grid balancing over time.”

Why a much smaller inverter? Would it be for mobile technology, like for a solar power electric car charging system? (This might be a silly speculation.) Another possibility is that much smaller solar power inverters might simply be easier to install. Increased ease could also result in more rapid deployment and the reduction of labor time and costs for solar installations, which is all a big part of installed solar power costs these days. Of course, there are always shipping costs to consider and lighter objects do cost less to transport.

rotary converter

Image Credit: Igor Chudov, Wiki Commons

Some of the earliest inverters were rotary converters and motor generators. Rotary converters were used in railway electrification and were rather large devices (pictured above). Later, vacuum tubes and gas-filled tubes were used. The thyatron is an example of such a gas-filled tube. Nothing like solar inverters of today.

While the progress in technological development may sometimes seem slow, if you compare today’s inverters with technology from previous decades, you can see a lot of progress, though inverters typically don’t get the press other inventions do, such as solar panels and wind turbines.

In fact, the Google Little Box Challenge is likely to be the largest prize ever offered for better solar power inverter design, and so will probably generate some much-needed press for the often less-noticed, but essential devices.

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About the Author

Hello, I have been writing online for some time, and enjoy the outdoors. If you like, you can follow me on Google Plus.

  • Think we need to use other materials to face this challenge, graphene or something like that.

  • spec9

    I don’t understand what Google is looking for with this. Physical size doesn’t seem to be an issue . . . the microinverters mount right under the panels. It would be nice if they could reduce a cost a little bit more for microinverters.

  • I am not sure what improvements Google wants. Today’s small (residential) inverters are already >97% efficient. Big beasts for utility scale are close to the 99% mark.

    The only thing I can imagine is them wanting a small inverter that is light and cheap enough to integrate into the panel. These microinverters already exist, but are too expensive and only cost effective in some circumstances.

    Google figured, if it is small, it is likely cheap, because small = less material (Unless expensive exotic materials are needed). An integrated inverter makes installing solar cheaper and easier. No need to match panels to each others and to the inverter. No more worrying about shade on one or two panels decreasing the power of an entire string.

    I have long figured that that is the future of residential solar panels, but until today, these AC panels are still that: the future.

    • LookingForward

      It would also shave off of installation time and cost and transport cost, I think this might be google’s goal

    • sjh

      Just take this idea a bit further: one inverter per cell. (Maybe in that diamond-shaped small white space in between the cells in a monocrystalline module) Make them talk to each other so most any output voltage/current can be made. The module could be a battery charger, constant-voltage DC power supply, matched to older modules in a replacement, whatever. And, more surface area to get rid of heat with. Such a module would be a game-changer. I think Google is spot-on.

  • Vensonata

    The inverter cost is about 35 cents per watt, the pv panel is about $1 watt. The goal should be about 18cents per watt for inverter and 70cents for pv. This is rapidly approaching. In fact at commercial scale may be possible now. This is only grid tied inverters, off grid single inverter charger hybrid off/on grid are still about 60cents watt. That needs to fall to 25 cents. Then only battery and mounting are the major price impediment. The best lead acid agm maintenance free batteries still add 16cents per kilowatt hour to off grid electricity costs. That’s where the fat in the systems lies…needs a 75% reduction.

    • DennisF

      Nickel-iron battery introduction into North America would solve that problem.

  • James Van Damme

    I don’t know where they’re trying to go with this. Usually, when your main design parameter is “make it smaller”, it costs more, uses special parts, has more heat buildup in a small space, and is therefore less reliable. You have all that space behind a solar panel, so make it big so you can spread out the heat, use easily available parts, and robust connectors. It’s worth considering whether you should collect and store energy at DC, and have one big inverter off a battery bank.

    I’ve used both inverters and rotary converters like the one in the picture above, and sometimes the m-g set wins out.

  • Offgridmanpolktn

    One improvement it would seem to be important for grid tied inverters is to be able to let the homeowner be able to utilize their systems when the grid cuts out. Being off grid it doesn’t affect myself, but when suggesting going solar to friends or neighbors the inability to have power during outages (which in our rural area still happen 2-4 times/year) turns them off to doing it.
    This will be a definite plus if this capability could be done without the need for battery investment, or with smaller battery packs to just keep the lights on at night and run the appliances during the day directly from solar.
    It wouldn’t hurt to do something on cost either, grid tie inverters still seem to be about ten times the expense of off grid by capacity right now, which was the situation eight years ago when setting up my system and a small part of the incentive for staying off grid.

    • driveby

      the solution to this are hybrid inverters, that can go ongrid, offgrid or backup.. whatever you want.

      In regards to the OT, I’d hoped for Google to be more drastic/innovative and take a slab from their 380VDC datacenter power distribution and push for something like 380/400VDC house distribution systems.
      Most appliances these days take the 120/230VAC and male DC from it.
      Now solar panels don’t produce AC, they make DC. So all those nice inverters hack and slash the power from the solar panels to convert it under losses of 2-5% into AC, just so that all those appliances (washing machine, TV, computers, Laptops, LED lights, etc..) make DC under new losses (5-15%) so it can be used..
      Pretty idiotic if you ask me.
      The only appliances that rely on AC are usually fridges.

      Do you have any idea how much in material and energy could be saved if this DC>AC>DC conversion chain could be wiped out?!?!
      The datacenters, who use up 2% of the worlds energy production are said to save 15-20% in energy if they can distribute 380VDC instead of 120/230VAC..


      • Steve Svensson

        Engineered and installed a $1.3 million grid intertie system 208 3 ph for three branches of the same bank, worked great. A lot is working with existing wiring, which is AC. Sending DC over any distance becomes challenging, even at higher voltages. Point of use is important, as line loss through transmission can be up to 50%, so building solar plants out in the desert is simply a money scam.

        • BruceMcF

          Though it does matter how high you take the voltage … line loss of +/- 320kV and up HVDC is 5% and less per 1,000km, well under line losses of equivalent AC.

        • Bob_Wallace

          How did this bizarre claim sneak through?

          Steve, Steve, Steve…. Learn some transmission facts.

          HVDC involves a small conversion loss at each end (~1.5%) and then about 3.5% per 1,000 km.

          A 50% loss would take ~14,000 km, 8700 mile line. Roughly the distance from Barrow, Alaska to Conception, Chile.

          Chile does have some good solar potential, but I think we can find power closer to home for Barrow.

  • Steve Svensson

    The Enphase inverters work great. Why not invest in them?

    • I think they’re looking to have much smaller inverters developed.

  • Thanks for sharing! As a 12+ experiences solar specialist I will subscribe to this google ventures project. Great read, thanks, Derrick van Voorst

    Ps. Check out my website: and I’m happy to help, Jake. Also added you in Google Plus. Keep up the good work

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