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Directory:Cool Earth Solar

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Cool Earth Solar (CES) has developed an inflatable solar concentrator technology that slashes materials costs, making solar competitive with commercial electricity generation systems.

The design consists of two 2.5-meter diameter sheets of plastic (Mylar) sealed around the perimeter like a party balloon. One sheet is clear, and the other has a thin coating of aluminum to make it reflective. They are then inflated like a balloon, to create a concentrated beam which is collected onto a photovoltaic cell suspended by a metal strut inside the inflated space. This achieves a 200- to 300-sun concentration, generating about 1 kilowatt of electricity. Water is used to keep the receiver cool. Each balloon is kept within a certain pressure (about 1/3 atmosphere above ambient). Several balloons are mounted on a frame which tracks the sun (2-axis, N-S and E-W).

The first commercial 10 MW plant, slated to begin construction in central California in the Summer of 2009, is expected to have an installation cost of just $1/Watt. Within five years, the company thinks they could get as low as $0.5/Watt, making it cost competitive with coal power plants.

This design lends itself to being able to be deployed very rapidly and inexpensively, and could be a significant contributing technology for meeting Al Gore's challenge for the U.S. to go 100% renewable within 10 years.

While the design resembles a balloon, it is quite strong. Wind will not be much of a problem. The system will be able to generate electricity, even with 30-40 mph winds, after which it will be shut down. Structurally, it can withstand up to 125 mph winds.



Official Website


  • Download (13 Mb; mp3) - On Aug. 9, 2008, Sterling D. Allan conducted a 1-hour interview with Rob Lambkin, CEO of Cool Earth Solar, as part of the Free Energy Now radio series. They talk about how the company's inflatable solar concentrator technology slashes materials costs, making solar farms able to compete with natural gas plants, and eventually even coal plants. Commercial deployment expected next year; could satisfy a large portion of Gore's 10-years-to-100%-renewable initiative.


  • Inflatable Solar Collectors - " has a patented idea for inflatable solar collectors that are much cheaper than polished mirrors to concentrate sunlight onto Photovoltaic chips. Their design is 400x cheaper than polished aluminum mirrors, will withstand 130 mph winds, lasts a year, repairs with tape, takes 15 minutes to change out, costs $2 per balloon, or 18 cents per watt, compared to $5 per watt for conventional installations, and has a minimal effect on the ground underneath the array!" (YouTube July 10, 2007)

Latest Developments

December 2008

"The first utility-connected Cool Earth project is scheduled to go online during the first half of 2009, a 1.5-MW plant on 12 to 13 acres near Tracy, CA. It is being financed with the firm's US $21 million in Series A financing. The off-taker "probably will be a northern California utility," says Lamkin. Cool Earth Is Scaling Up Solar Energy Generation (Renewable Energy World; Dec. 5, 2008)

February 2008

Received $21 million in funding to build pilot plant

March 2007

Building prototype for Fall 2007 and raising capital to enable rapid growth.

How it Works


Image:Cool Earth Solar concept sketch.gif

Image:Cool Earth Solar farm concept sketch 500.gif



  • Inflatable mirrors are 400x cheaper than polished aluminum mirrors.
  • 2-m diameter
  • Withstand 130 mph winds
  • 1-year life span of replaceable films
  • repair with tape
  • replace in 15 minutes
  • $2 cost
  • Rigging requires 60x less steel than truss work [for conventional solar]
  • Minimal grounds preparation
  • Much faster installation
  • Land use and habitat minimally affected

Price Point

" Our Phase II system will cost (us)
- 18 cents / Watt for materials
- 29 cents / Watt installed in a large solar farm
Compared with $5 / W for conventional solar installations." [1]


  • 4 Patents Filed
  • Several in process.

Company Profile

Founded in 2007, this new company is in the process of building the concentrated solar PV modular and system. CES is looking for top engineering and business talent to assist.

"Our goal is to cut the cost of solar electricity to a price that is truly competitive with coal and other non-renewable sources--while generating profits for our users on par with today's best investments." -- company website

Business Model


  • FY07+ - 10-50 kW installations
  • FY08+: 50 kW - 1 MW installations
  • FY10+: 1-10 MW Micro-utility franchises



  • Proof of principle complete.
  • Detail design and subsystem prototyping under way
  • Seeking manufacturing partnerships
  • Building manufacturing team
  • Seeking investment to bring Phase I product to market by end of 2007

In the News

  • Cool Earth Is Scaling Up Solar Energy Generation - At an installed cost of US $1 per watt and thus lower project ROI, "it doesn't have to have maximum insolation (rate of delivery of solar radiation per unit of horizontal surface)" and the type of site it seeks is typically close to transmission. (Renewable Energy World; Dec. 5, 2008)
  • Solar Bubbles Get Funding - Cool Earth Solar has received $21M in funding to build a pilot plant. The company is developing inexpensive solar concentrating mirrors in transparent balloons to lower the cost of solar photovoltaics. (EcoGeek; Feb. 19, 2008)
  • Concentrated Solar > Coolearth > CoolEarth Solar Receives Major Funding - CoolEarth, which develops and owns solar power plants utilizing a proprietary concentrated photovoltaic (CPV) technology (reflective balloons), has received $21 million in VC funding for a cost efficient power plant that competes economically with conventional fuels. (Inhabitat; Feb. 14, 2008) (Thanks RLP)
  • Inflatable solar? Coolearth Concentrated Photovoltaics - Coolearth Solar has patented a design for inflatable solar collectors that are supposedly a cheaper way to concentrate sunlight onto photovoltaic cells. They claim their design is up to 400 times cheaper than polished aluminum mirrors. (TreeHugger; Dec. 6, 2007)
  • Balloon technology could cut cost of solar energy 90% by 2010 - CoolEarth Solar could make solar energy cheaper than coal within 3 years using inflatable solar PV concentrators suspended above farmland. The company hopes to cut the cost of electricity in a 1 MW installation to 29 cents per watt by 2010, with limited environmental impact. (Mongabay; February 21, 2007)
  • Won runner up at the California Cleantech Open in 2006 for concept.


CoolEarth Solar, Inc. 

4659 Las Positas Road, Suite C
Livermore, CA 94551
Phone: 925.454.8506
Fax: 925.454.9487

Tony Chen;

Senior Manager, Business Development
Phone: 925.454.8506 X231

NEC Specialists

  • New Energy Congress member, Jonathan Bonanno, is an investor and sits on the Board of Directors of Cool Earth Solar.


See Discussion page

See also





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