Ultrasolar Technology is a Silicon Valley startup that has developed a pyroelectric device to boost solar cell efficiency.
We all know what “pyro” means, but what is “pyroelectric” all about? According to this Greentech Media piece, which provides a helfpul overview of Ultrasolar’s methodology, “[p]yroelectricity converts heat to [an] electric field.”
One of Ultrasolar’s patents says this:
Pyroelectric materials may generate electrical energy (e.g., temporary voltage) when they are subjected to a change in temperature (e.g., heated or cooled).
More to the point, Ultrasolar’s technology draws “hot” electrons, which would normally lose their energy in the crystal structure of the solar cell, to the solar cell’s electrodes, thereby increasing the power produced from the cell (and the modules).
Ultrasolar owns at least five U.S. patents and applications relating to its pyroelectric technology. According to Cleantech PatentEdge™, the company also owns two international, or PCT, applications.
U.S. Patent Application Publication No. 2011/0232734 is entitled “Pyroelectric solar technology apparatus and method” and directed to methods of increasing solar cell efficiency by depositing pyroelectric film on a cell (’734 Application).
In its basic embodiment, the ’734 Application describes a solar cell (102) having a transparent pyroelectric film (104) on its front surface and an opaque pyroelectric film (106) on its back surface. The transparent pyroelectric film (104) may be applied onto a resistor (108) placed on the front surface of the cell, and an ohmic contact (110) placed on the transparent film (104).
According to the ’734 Application, heating of the transparent pyroelectric film (104) and/or the opaque pyroelectric film (106) generates an electromotive force to bias the solar cell (102), thereby creating an open circuit voltage. Moreover, heat from the sun or waste heat can cause current in the pyroelectric material (104, 106), thus increasing the total current of the solar cell (102).
According to U.S. Patent No. 8,324,783, the pyroelectric material may produce electric charge when subjected to a change in temperature over time.
The ’734 Application explains that a temporal temperature gradient may be generated on the solar cell (102) through a standing infrared wave through the pyroelectric films or using pyroelectric films of varying specific heats and conductivities at a front and/or back of the solar cell.
What are these pyroelectric materials that seem so promising? The ’734 Application lists a bunch:
In one or more embodiments, transparent pyroelectric film 104 may comprise of a polyvinylidene fluoride, a tri-glycerin sulphate, a lead zirconatetitanate, a stannic titanate, a lithium tantalate, lithium niobate, aluminum nitride, titanium aluminum nitride, barium titanate, and/or barium strontium titanate. In one or more embodiments, opaquepyroelectric film 106 may comprise of a polyvinylidene fluoride, a tri-glycerin sulphate, a lead zirconatetitanate, a stannic titanate, a lithium tantalate, lithium niobate, aluminum nitride, titanium aluminum nitride, barium titanate, and/or barium strontium titanate.
The Greentech Media story says Ultrasolar is hoping to use these pyroelectric materials to boost solar module efficiency by 20 percent.
Eric Lane is a patent attorney at McKenna Long & Aldridge LLP in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@mckennalong.com
