When you think about portable solar power, you probably envision a solar charger panel kit or similar device. But the ultimate in portable solar power is, of course, solar vehicles. These vehicles are powered wholly or partially by sunlight, usually via photovoltaic (PV) cells. There are quite a few examples of solar vehicles in use today, but the technology holds more promise than reality. What is more feasible currently is indirect solar charging, where solar panels charge batteries that are then used to charge vehicles or feed electricity into the power grid.
For the solar vehicle market to grow, a few limitations will have to be overcome:
- Vehicle size: You can’t get a lot of solar panel acreage on the roof of a car.
- Cost: PV is still relatively expensive, though the costs continue to come down.
- Ruggedness: PV panels are usually made for stationary use, even if portable. A moving vehicle puts more stress on a PV panel, shortening its lifetime. Still, the panel will likely outlive its vehicle.
- Weight: Panels are heavy, so they must provide more energy than they waste.
Notwithstanding these challenges, solar vehicle development continues. Here are some interesting examples:
- Solar Cars: Plug-in hybrid or pure electrics can use external solar batteries or solar arrays for charging. A triple hybrid car adds a solar panel to the gasoline/battery drive system. In 2010, the Toyota Prius started offering a solar roof panel that runs the air conditioner when the car is parked in the sun. Other cars followed suit, including the Audi A8 and the Mazda 929. Solar golf carts and scooters have come onto the market in recent years. The scooters have fold-out solar panels that charge while the scooter is parked.
- Solar Bicycles and Tricycles: A small motor supplements the rider’s foot power. The motor draws power from a battery hooked into a set of fold-out solar panels. Solar-powered quadracycles are used in India. The 1985 Tour del Sol in Switzerland was the first solar cycle race.
- Solar Watercraft: A solar catamaran sailed from Spain to Miami in 2007. A solar catamaran yacht was launched in 2010. Japanese shipping lines are placing solar panels aboard to generate auxiliary power.
- Spacecraft: Most satellites are powered by solar panels, though solar power is not generally used for propulsion. However, Martian orbiters have indeed used sunlight for their propulsion systems, typically ion thruster drives.
- Other Applications: There are lightweight manned and unmanned aircraft that use solar power. Italian rail freight cars have tested onboard PV panels to generate auxiliary power. There are also experimental solar trams, buses and trolleys in various stages of development.