Livermore, California-based Cool Earth Solar is set to complete construction of their first prototype plant in the next few weeks. If all goes according to plan the new plant will change the shape of renewable energy scalability – literally.
I had the opportunity last week to speak with CEO Rob Lamkin about Cool Earth Solar’s mission and the difficulties facing alternative energy companies. In terms of the challenges of renewable energy, Lamkin was clear and concise: “scalability”.
Says Lamkin: “If you’re going to replace hydrocarbons with solar, you’re going to need a lot of collecting surface”. Cool Earth Solar addresses this challenge by changing the shape of the collecting surface.
Instead of using row upon row of flat panel solar collector “boxes-with-lenses” requiring heavy, expensive materials to build, Cool Earth utilizes what might be considered an application, in both concept and materials, of Ockham’s Razor: Keep it simple.
Cool Earth’s patented design is centered on an inflated balloon-shaped “solar concentrator”, about eight feet in diameter, made of thin plastic film – the same sort of material used in potato chip bags. The upper hemisphere of the “balloon” is transparent, the lower is reflective, and sunlight is concentrated on the photovoltaic cell held at the focal point. A single concentrator can generate about 1 kilowatt of power.
The unique design is simple in its concept and produces 300 to 400 times the electrical output that same cell could produce in a conventional solar collector.
Challenging fossil fuel
At $1 per watt, Cool Earth Solar is able to produce electricity at a cost already competitive with power generated from natural gas. And coal is square in their sites, as Lamkin recently told Discover magazine:
“…the bottom line is that today we can generate electricity as cheaply as, or more cheaply than, we do natural gas – and we expect to pass coal soon. ”
Lamkin intends to prove the scalability of the concept when the quarter-million-watt prototype plant is up and running in four or five weeks. The plan is to scale up and refine the plant in phases, with each phase an improvement of the technology. Other issues beyond scalability Lamkin told me he anticipates the prototype plant will address include improving concentrator tracking of the sun and collecting data on the thin film membrane of the device.
Lamkin acknowledges the longevity of the film is currently only about one year, and the data collected will help extend it. Still, Lamkin says, a single unit only uses a few dollars worth of film, and the material is readily available.
“There is enough plastic film produced every year to supply one entire 2 terrawatt plant”, says Lamkin.
Cooling and support
Each concentrator unit weights about 20 pounds when inflated. The structure is strong enough to support a person’s weight and aerodynamically stable enough to withstand 125 mile-per-hour winds.
The film enclosure protects the PV cell from the weather, dirt, and insects. A tethered steel strut inside the concentrator holds the cell at the focal point with a conduit in the the strut providing a small water loop for cooling.
A flexible lightweight steel band around the circumference of the concentrator helps support the inflated concentrator’s shape, holds the unit in place, and helps aim the PV cell toward the sun.
Concentrators are deployed in the field using a system comprised of wood poles and steel cables in a patented support design based on the principal of tensegrity, an architectural concept of stabilizing structures by continuous tension rather than by continuous compression (and more fully described by by Dr. Timothy Wilken).
The whole design is geared toward using a minimum of materials with a relatively small environmental footprint.
Scaling up toward the future
In 2005, 17,320 terrawatt-hours (TWh) of electricity was generated world-wide. That figure is expected to double by 2030.
In an article I recently wrote in Cleantechnica.com, some commenters expressed their skepticism in the idea of scaling the Cool Earth design with comments along the lines of “the sky filled with balloons blocking out the sun”. Specific to that comment, of course, is the fact that concentrators are deployed close to the ground and will hardly “block out the sun”.
The fact is, as I see it, that scaling any technology to a degree capable of making a serious contribution to our voracious energy appetite and weaning us off our unsustainable use of fossil fuel will mean lots of something; be it windmills, geothermal plants, or solar plants. The idea that any method or technology of generating the power our society requires can be totally benign is a myth that is best abandoned sooner rather than later. Generating power requires an environmental footprint.
The hope and promise of the Cool Earth Solar concept is to minimize that footprint, bring the cost per watt of solar energy down to a level that meets or beats fossil fuels, and provide a means of scaling up to a degree capable of making a significant contribution to our future energy needs.
Lamkin believes Cool Earth can do that. In fact, he believes that Al Gore’s challenge of 100% electrical generation within ten years is doable, at least technically, and that Cool Earth could do it with one 150 mile by 150 mile solar plant (or, presumably, with a number of smaller plants). The point being is that it is doable.
Cool Earth has a ways to go to reach that point, but Lamkin and his team are on a mission, and they aren’t about to let a little skepticism stand in the way of what they believe is the full potential of their design. Lamkin is chomping at the bit to prove what it can do.
Beyond the imminent completion of the Livermore prototype plant, there are plans to build the first commercial-scale 1.5 megawatt plant in Tracy, California early next year, with further plans to rollout larger 10 to 30 megawatt plants throughout California’s central valley.
Inherent in the design is the ability to install solar plants in terrain unsuitable to conventional solar plants. A 30–megawatt plant requires roughly 200 acres, or about 20% less land than conventional solar.
First California and then the world
Lamkin’s vision is to bring his technology to the world. He sees the Cool Earth design as one the addresses the central constraints of renewable energy in general and solar power in particular. He sees the only block to achieving the goal of 100% renewable power generation as one of political and social will.
For people like Lamkin and his team at Cool Earth Solar, the future looks bright as we stand on the eve of the new energy economy.