Solar cars

Solar cars are powered by electricity through the use of solar energy. Solar panels are attached to the surface (generally, the top) of the vehicle. Photovoltaic (PV) cells convert the Sun's energy directly into electrical energy.

Powering cars using solar energy has some great benefits:

• Using solar energy means fossil fuels (which are a limited resource) will be used less.
• Solar energy is free.
• Solar energy doesn’t cause pollution.
• Solar energy will never run out.

However, there are some problems:

• You can only get solar power during the day (and there is less on cloudy days).
• Solar equipment is very expensive.
• Expensive batteries are needed to store solar energy for cars to be able to run at night.
• Solar cells are not very efficient, and the collector areas are too big for consumer cars.

Scientists are working on these problems. Battery systems that offer high-density energy have become a focus of auto industry scientists. Development continues towards designing solar panels on cars that are more efficient.

Unfortunately, at this stage, solar cars are still not suitable for day-to-day transport. However, solar cars are built for special purposes (demonstration and engineering exercises) and are built by enthusiasts who want to race them.

There is a very famous race called the Bridgestone World Solar Challenge that is held every 2-3 years from Darwin to Adelaide in Australia. It’s held there because there is lots of Sun. It’s 3,006 km long. Kiwi couple Vivianne and Stewart Lister designed and built a solar car and entered it in the 1993 race. (You can read about their story in School Journal Part 4, Number 3, 1994.)

Vivianne and Stewart constructed a large solar panel across the top of their car. They made the panel adjustable so that it could be moved to face the Sun. This was great because they could keep going all day by just tilting the panel. It did cause a problem though – the car became unstable at high speeds. Consequently, their average speed was 50 km/h. One time, a great gust of wind picked the car up 10 metres into the air and dumped it into the rocks and trees about 100 metres from the road.

Other problems included extreme heat in the cockpit while driving (40–45°C), and the battery was not able to store enough energy for cloudy weather. The batteries were large and took up a lot of space.

Vivianne and Stewart finished the race and came first in their class (for private owners). There were better and faster cars, but they were cars sponsored by big companies such as Toyota who could put lots of money into making them.

Research and development into solar cars continues. The cars are getting faster and big corporations are looking at more efficient solar cells and battery technology – where the batteries are lighter and hold more energy. When the World Solar Challenge began (1987), the winner’s average speed was 67 km/h. In 2007, the winner’s average speed was 91 km/h.