A cocktail of advancements in battery technology, lightweight materials, engineering analytical software and, of course, solar panels, have allowed some extraordinary achievements to take place in the world of sustainable automobiles. More than ever, solar powered cars are looking less like something out of science fiction, and more like reality.

Schools and universities around the world are leading the charge in this exciting realm, with organized events such as the:

• World Solar Challenge (www.worldsolarchallenge.org),
• American Solar Challenge (www.americansolarchallenge.org),
• South African Solar Challenge (www.solarchallenge.org.za),
• And aimed specifically at high school students, the Solar Car Challenge (www.solarcarchallenge.org)

all providing a high powered boost to interest and innovations in clean transportation.

And the statistics are impressive. For example, the World Solar Challenge, first launched in 1987, pits teams against each other in a gruelling 3022km route across the Australian outback from the north to the south of the country (Darwin to Adelaide). By 2005, the race rules were modified to limit the performance of the cars to address both the challenge of support crews being able to keep up with solar cars capable of 130km/hr, and the highway speed limits of 110 km/hr. Believing that the objective of designing cars capable of highway speeds had been accomplished, they moved on to other challenges. Restrictions such as reductions in allowable solar panel coverage and stricter battery weight limits came in. Despite this, top performers are still averaging speeds over 90km/hr.

So what are the specs behind such cars? Cars in the World Solar Challenge have had about 5 kilowatt hours (kWh) stored on board. This refers to the amount of battery power available to be used. It’s estimated that this is about 10% of the race’s total energy requirement- the rest is generated from the sun. When you consider the relatively low efficiencies of solar panels (see our article on solar energy here), this is quite an achievement.

As an example, the World Solar Challenge regulations include the following:

• A maximum of 6 square metres of solar panel area (for silicon photovoltaic systems), and 3 square metres for gallium arsenide systems. Depending on efficiencies and sun conditions, this could generate anywhere from 500 to 1500 watts of power. For reference, your home toaster probably uses about 1200 watts. And so these cars need to be EFFICIENT.
• Depending on the race class, either 20kg or 60kg of lithium-ion or lithium-polymer batteries (some other battery types are also allowed in varying weights). With these batteries generally providing in the range of 100 to 265 watt hours per kg (Wh/kg), that’s a total storage of 2000-5300 Wh. And if its sucking up 500 to 1500 Watts, batteries won’t go far.

But these cars combine aerodynamics and light weight to harness the little power they have. The new Cruiser class of the World Solar Challenge aimed at encouraging development of a practical vehicle capable of carrying four people. The 2013 inaugural event saw a car complete the event with a total energy consumption of just 64 kWh. For comparison, a typical modern car would consume an energy equivalent of around 5000 kWh. One of the 2015 entrants, the Stella Lux, weighed just 826 pounds, or 374 kg. An average commercial family car can weigh 4000 pounds.

But rather than being intended as cars for use commercially themselves, the vehicles act as a platform to test new concepts and demonstrate the capabilities of sustainable technology. And with the number of teams and sponsors getting involved around the world, these solar powered cars are definitely achieving that goal. The horizon is looking bright for these futuristic machines, and we look forward to following their evolution…