In this article in the online publication Laser Focus World, DILAS (Tucson) General Manager & Vice-President Dr. Georg Treusch discusses this application from the vendor’s viewpoint. It’s a somewhat technical and very interesting article. We learn, for example, that DILAS “…supplied the best performer in 2007 with a power-beaming source on very short notice (three weeks), using a new modular diode-laser-based power beamer that is applicable for both terrestrial as well as spaceborne applications.” The ‘best performer’ referred to was USST.
Dr. Treusch also discusses what is planned for 2008:
The new design for the power beamer considers various approaches from different teams using low-cost Si- or highly advanced GaAs-based photovoltaic (PV) cells. Material choices, PV cell, and beam characteristics are up to the competing teams; the challenge simply sets the distance and minimum average rate of climb. Each team is likely to have its own approach with power-beaming systems ranging from 2.5 kW to values above 10 kW.
The wavelength for the power-beaming sources will likely be between 800 and 980 nm. High-power diode lasers have efficiencies greater than 60% and power levels greater than 100 W per 10 mm bar. It is a happy coincidence that Si and GaAs photocells are more efficient at this spectral range compared to wavelengths above 1 µm, which is the spectral domain of fiber and disk lasers.
A very interesting article – highly recommended.
Also, while searching through this publication’s archives, I found this article. While it focuses on delivering power to photovoltaic cells via fiber-optics, it also discusses delivering power to photovoltaics via ‘free space’; i.e. using light (or lasers). It also briefly mentions the 2005 Space Elevator competition.
I guess I’ll have to keep watch on this publication, too. So many articles, so little time…