The sleek curve of an airfoil. Four lean racing tires, half-veiled in black. Gleaming tiles of midnight blue – the all-important solar cells. A small black bubble rises amid the sapphire squares, housing the eyes of the driver and a window to the machinery hidden below.
This foxy beauty of engineering, the Beam Machine, is the most recent brainchild of the California Solar Vehicle Team (CalSol for short). A core group of twenty students, mostly mechanical and electrical engineers, designed and constructed the solar car over the course of two years. And this summer, we get the chance to race it against the creations of our peers – 2,500 miles from Texas to Alberta in the North American Solar Challenge.
The July 17-27 race will include three stage stops. Teams can only drive between 8 AM and 6 PM, but all will wake up at sunrise to charge their solar arrays, and will charge again after each day's drive until sunset. During the race, strategy and quick identification and resolution of problems will determine the winning teams. I will be involved in any array-related issues, and will run the simulator we’ve programmed to help us make decisions about when to charge (and not drive) and what speeds to maintain. And I'll be filing reports and photos (daily, I hope) as we cruise through America's heartland and Canada's prairie provinces on beams of sun.
But before we get there, we need to qualify as roadworthy. In May, we traveled to Heartland Park in Topeka, KS, to be inspected by officials and compete in the track race, the Formula Sun Grand Prix. That was our first test, and I'll be writing about it in this journal. In July, we will again be required to qualify for the Solar Challenge. If we do, we have a race and hard work ahead of us. If we don’t, we go home.
Formula for success
Solar car design hinges on minimizing power consumption and maximizing solar power, while still having a safe vehicle. The first part requires good aerodynamics, reduced weight, and limited energy dissipation in the electrical and suspension systems. Increasing power from the solar cells depends on the efficiency of the cells and the setup behind the wiring.
(Steve McConnell photo)
We addressed these issues for the Beam Machine by using aluminum tubing (instead of steel) for the chassis, carbon fiber composites for the shell, canopy, and wheel fairings, lithium-ion batteries (because of their high power-to-weight ratio), monocrystalline silicon for our solar panels, and a 97% efficient hub motor.
Running on about 1,500 watts of electrical power – around what your toaster uses – solar cars like ours can cruise at freeway speeds of 65 mph. They've even been clocked at over 100 mph on test courses. However, as vehicles registered with the DMV to travel on ordinary roads, the Beam Machine also has to obey things like speed limits, and be equipped with turn signals and mirrors. (We get away with not having headlights because we don’t drive in the dark, although we could run off of battery power for a while).
Each Saturday and Sunday, CalSol members put in about nine hours a day working on the car at our base at the Richmond Field Station. We also put in time during the week in the student machine shop on campus and doing planning and design work, in addition to coping with the rigorous engineering curriculum. Then there are the financial issues. While some of our materials have been donated by sponsors like 3M, Hexcel, Dow and others, big-ticket items such as solar cells, batteries, the motor and motor controller usually don't come from donor companies. The cost of building a solar car can range from $80,000 to several hundred thousand dollars. We used to joke about selling our kidneys to finish building the car, but thankfully, we acquired our generous primary sponsor, Hybrid Technologies, in fall 2004.
Sound like a crazy amount of work? We won’t deny it. But CalSol means so much more. It’s the stimulation of being with a tight group of motivated, talented individuals. It’s knowing that our calculations will turn into something tangible, like a finely machined kingpin, rather than a good grade on a test. It’s realizing that being wrong doesn't mean just points off on a quiz, but could result in mechanical failure, flames, or even loss of life. It’s the spirit of creation born to catch the sun.
This July, it's the chance to test all our hard work. For two years, we've poured our passions into an airfoil form on wheels. Now it's time to pit ours against theirs. When I hear that gun at the start in Austin, it will begin a 2,500-mile-long adrenaline surge.
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