Cool Earth Solar — a cool innovation

Instead of expensive mirrors, why not use 8-ft diameter mylar balloons — clear on top, reflective bottoms? Solar electricity cheaper than natural gas? Let’s wish this team can succeed to take this approach to industrial scale!

If solar power is expensive in part because the materials come dearly, then use cheaper materials. That’s the design principle behind thin film solar cells, and now also behind a form of concentrated solar using plastic balloons, designed by a firm called Cool Earth Solar.

Concentrated solar uses mirrors to shine more light onto regular solar photovoltaic cells, in order to get more energy, and thus more profit, out of a single cell. However, the mirrors themselves and machinery needed to keep them precisely aimed usually drive the cost per watt back up.Cool Earth’s idea is to use a reflective inflatable made out of mylar, a cheap plastic often used for food packaging, to reflect light onto cells. The company claims that its scheme produces energy at a lower cost than natural gas plants.

How frequently are these balloons going to have to be — i.e., what is their average life expectancy? Note that the company is in the electric utility business — they will not sell solar components to you as consumer. They are working on contracts to sell their solar-generated power to the California utilities. Excerpts from their FAQ:

When will you be accepting customers? coolearth is currently negotiating with electrical utilities for the sale of energy from our solar power plants. The company’s goal is to provide clean, renewable, solar power electricity at a competitive cost with current fossil based sources of grid power.

How is the coolearth solution better than other solar technologies? coolearth’s solution has two main advantages. First, our CPV technology addresses the limited availability and cost fluctuations of solar cells. Second, our innovative use of reflective thin films as our reflector material reduces by an order of magnitude both the amount of material and the weight required for a CPV system. The result is a solution that generates electricity at a price competitive with that of traditionally fueled power plants.

Why are your solar concentrators inflatable? Serendipitously, inflation air allows us to make an effective concentrator from nothing but thin flat clear and reflective plastic films that are bonded to each other like a conventional foil balloon. The inflated structure is lightweight but strong enough to survive 125 mph winds. We can optimize the optical properties of the balloon by actively controlling its inflation. The balloon also forms a protective barrier around our receiver.

What is Concentrator Photovoltaic (CPV) technology?

Similar in principle to using a magnifying glass to concentrate light, concentrated solar systems use lenses or reflectors to concentrate sunlight onto highly efficient solar cells. By concentrating the light onto a single high efficiency cell, the technology vastly reduces the amount of traditional solar cell area needed to produce electricity. Multi-junction, high efficiency cells derived from satellite technology allow CPV systems to generate the same amount of electricity as traditional flat panel PV systems while using up to 500 times less solar cell material.

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