Solar Cells Info

By: Irma Venter, 24 Oct 08
Source: Creamer Media’s Engg News
http://www.engineeringnews.co.za/article.php?a_id=145203

A car powered by the sun is such a novel idea to South Africans that the Kokstad traffic police stopped the participants in the country’s first solar car race, demanding to know where “they are taking these solar panels”.  However, says race organiser Winstone Jordaan, it also epitomises everything this race is about: exposing South Africans to alternative technologies, and educating the public about solar energy specifically.

Participants in the race included three South African teams, two Indian teams and a Japanese team – and, just for fun, a hydrogen-powered motorcycle, all the way from Malaysia.

Unfortunately, a South African team was not the first to cross the finishing line, with the honours going to a well-oiled team of Japanese engineering students from the Tokai university, near Tokyo.

To win, the team, (ironically from the land of the rising sun) had to complete a more than 4 000 km route from Johannesburg to Cape Town, and back up again along the Garden route, via Durban, to Tshwane, their vehicle powered by nothing but the sun.

Completing the journey took 11 days.

The team driver was Japanese racing legend Kenjiro Shinozuka – the 1997 winner of the Paris – Dakar rally.

He says the South African race was a particularly tough one as the steep up- and down-hills made it difficult going for solar cars, which excel on flat terrain.

Solar car relies on solar panels that convert sunlight into electricity. This electricity is stored in batteries, which are then used to power electric motors that turn the car’s wheels. As such, solar cars are not very powerful.

The Japanese car is a 1,6 horsepower vehicle – compared to an average car which kicks out 120 horsepower – making it difficult to tackle steep inclines.

Shinozuka also notes that persistent rain and fog in the Eastern Cape almost got the better of the solar cars.

The Japanese team leader, the Tokai university’s professor Hideki Kimura, says the Japanese solar car, already 12 years old, can travel for about five hours without aid from the sun.

To achieve this, the car makes use of advanced lithium-ion batteries, which store the energy captured by the solar panels, covering nearly every inch of the top of the roughly two-by-three metre vehicle.

The choice of batteries is pivotal to success.

The first South African team across the finishing line was renewable energy company Divwatt’s Team Sunna – referring to the sun goddess. (South Africa’s universities were all absent from the race.)

MD Ian de Villiers says the biggest lesson the company learnt their first time out on the track was that “it’s all about weight”.

He says Team Sunna made use of lead acid batteries, which already weighed 120 kg without adding the solar panels, wheels or structure.

“We could have gotten twice as much power from lithium polymer batteries weighing about 30 kg,” says De Villiers.

Divwatt plans to enter a new car in the second solar challenge, scheduled for 2010.

“The race has shown us that this design is too heavy, which is why it has been dubbed the ‘Flying Brick’,” says a tired, but amused De Villiers.

“This is the first solar car we ever built, and there were a lot of unknowns.

“Now we know, the higher the tech, the better. The lighter, the better.”

De Villiers says Divwatt started design work on its vehicle in May already. Once in full flight, the company completed the vehicle in three and a half weeks.

Team Sunna’s top speed is 75 km/h, says driver William Baloyi.

The lighter the car, the faster it travels – which is evident when considering the carbon-fibre Japanese car weighs 150 kg in total.

However, advanced technology also means a jump in cost.

Kimura says the Japanese sun chaser costs around R550 000 – and for that price one can buy a luxury German sedan with all the extras, and not a small, cramped single-seater vehicle, without indicators and a radio – even if your monthly fuel bill may be nonexistent.

Each team was assigned an independent observer, who made sure it adhered to the rules. For example, no car is allowed to travel in the slipstream of another car, and batteries may not be charged overnight.

The car must truly use only the sun as its source of power.

Jordaan says the South African solar challenge will be back in 2010, following the Soccer World Cup.  Maybe, by then, we will have a corporate sponsor, and not only the nonprofit Advanced Energy Foundation.  “Already we have 15 South African teams hoping to participate. This first race has generated a lot of positive response,” says Jordaan.