Concentrating solar thermal has also been investigated as a direct thermal method of producing aluminum.

While not a technology, photosynthesis is arguably the most important photochemical interaction. A diverse biology has developed capable of photosynthesizing light in the visible, ultraviolet, near infrared and far infrared regions of the electromagnetic spectrum.

To demonstrate the principle of photovoltaics at an open-air fair, Greg Johanson wired some PV cells onto a toy electric train. Seeing the attention this little solar train got as it sped around its track, Greg and I thought that a solar vehicle would attract more interest in PV. That's what inspired us to build our first solar vehicle.

Our first vehicle was not strictly solar powered. It was a lightweight three-wheeler with an 1/2 horsepower, 60-volt, direct current motor. Five small, 20-amp hour, 12-volt batteries wired in series were used for motive power. Five 35-watt Arco Solar modules, mounted like a canopy, trickle charged the batteries. The vehicle could travel (very unsafely) over 40 mph (64 km/h), but under 30 mph (48 km/h) it was fun to ride. Under direct solar power in full sun, the vehicle would go 6 mph (9.6 km/h).

To charge the batteries, we chained the three-wheeler to a pole outdoors in the sun. The steering wheel was removed to prevent joy riding or theft. Unfortunately, one evening, the vehicle was stolen. Despite its unique appearance, a police investigation, and a $500 reward, it was never found.

The theft was a shock and a setback. All the time and money put into the vehicle was lost, but we had been bitten by the solar vehicle "bug." We wanted to build something bigger and better. Our experience and calculations indicated that a solar-only vehicle was possible. Besides, battery vehicles are fairly commonplace. We wanted to do something new.

After research and discussions with bicyclists and engineers, we sketched plans. Sunrunner, our aptly named vehicle, was designed for speed. Although some of the design ideas came from work developed by members of the International Human Powered Vehicle Association, compromises had to be made to accommodate the solar array. Also, we wanted the array to double as a portable power plant for more practical demonstrations.

Construction proceeded slowly as we were paying for the project out-of-pocket with no sponsor or grant. We used lightweight chrome-molly steel for Sunrunner's frame. The design provided enough flex to eliminate the need for suspension hardware. We used wheels designed for tandem racing bicycles and light-weight wheelchairs. No batteries were used on Sunrunner; the solar array would be the entire power plant.

To simplify the steering mechanism, we made the turning radius large. As the speed run would be a straight track, high speed maneuvering was unnecessary. Our experience with the first solar vehicle taught us to design for the open, quiet roads in the desert, not the city. There are no restrictions on experimental vehicles, but city driving is out. The danger of an accident caused by curious drivers and onlookers was too great. Every time we took Sunrunner on the street, traffic would stop and people would stare.

Our first brakes were racing bicycle disc brakes which worked too well. They locked the wheels on our lightweight vehicle that weighed less than 600 pounds (272 kg) driver included, causing tire burn-through. We compromised and used bicycle caliper brakes, which we jokingly called "slower-downers."