GreenVolts Concentrates PhotoVoltaics in San Francisco

Establishes headquarters near SF Financial District

I first heard and reported about GreenVolts at Solar Power 2006, and I met GreenVolts ( CEO Bob Cart at the 19th NREL Industry Growth Forum:

Solar start ups at the 19th NREL Industry Growth Forum Part 1
California Governor Arnold Schwarzenegger addresses Solar Power 2006

On February 9, 2007, I interviewed Mr. Cart for the inaugural meeting in the main conference room at GreenVolts’ new offices in San Francisco. GreenVolts had just moved into these offices on the same day. The office space was donated by PG&E Corporation (NYSE:PCG) to GreenVolts as the 2006 Winner of the Renewables Prize at the California Clean Tech Open.

Since the NREL Forum, Mr. Cart has been refining and implementing the GreenVolts strategy, and he said:

During our R&D investment phase, GreenVolts has successfully developed an efficient solar generation system capable of low cost mass manufacture. This was a vital step towards achieving our goal of providing utilities the lowest total cost solar energy solution possible with direct delivery of electricity to their customers over the existing grid.

Under his leadership, GreenVolts has focused on delivering 1 to 20 MW (Megawatt) scale projects generating near load and on the transmission grid while requiring no new transmission lines.

GreenVolts has made steady progress building its core team, developing utility customers, and raising capital to achieve business goals. Bob Cart said the company has moved from SolidWorks models to expensive, one off, physical prototypes. Although I was not allowed to snap a photo, a scale prototype of the High Concentration PhotoVoltaic Off-Axis Microdish was on the conference room table during our discussions. The mirror for this one off prototype cost GreenVolts $20,000 USD to fabricate based on their two exclusive licenses from Lawrence Livermore National Laboratory.

Besides the basic microdish, GreenVolts has sought to lower the total cost of installation by leveraging their CarouSOL concept, an array of fourty-four (44) quad microdishes arranged to follow the sun with two axis tracking. Using III-V multijunction (MJC) terrestrial solar cells from Spectrolab, a unit of The Boeing Company (NYSE:BA), and adding 14 quad microdishes to the original design, the system capacity of the CarouSOL has increased to 3.5kW. I saw a video in Bob Cart’s office of a CarouSOL base mechanism prototype in dual tracking operation. As a non traditional tracking approach, the CarouSOL does not require poles set with concrete like SolFocus or Concentrix and can be assembled on site, set on the ground, and secured at lower cost.

Beyond manufacturing and installation, GreenVolts recognizes the importance of operation and maintenance costs to the total cost of system operation. As their products proceed from prototype development to qualification and manufacturing ramp, GreenVolts is partnering with utilities, national labs, and certification bodies to ensure a smooth transition to volume production. Since CarouSOL is located on the utility side of the grid, high power, three phase inverters ranging from 100kW (kilowatt) to 250kW are required to convert the DC (direct current) to AC (alternating current) for power conversion and transmission.

If you look at the GreenVolts’ website, there is page front with a link to the California Clean Tech Open Announces Inaugural Winners and a visitor logon. I expect there will be exciting new developments from GreenVolts in the weeks and months ahead.


  1. Nathan says:

    Great reporting and very interesting. It seems there are a large number of concentrators entering the market. Greenvolt’s angle seems to be focusing on utilities.

  2. Anonymous says:

    At first glance, the GreenVolts CarouSol concept is already being built by Pyron Solar in Southern California.


    Although Pyron uses Fresnel lenses and not parabolic mirrors, both concepts use low profile floating bearings for the azimuth axis tracking of the sun.

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