Category: Battery Electric Car

Qualifying day for the Bridgestone World Solar Challenge at Hidden Valley Raceway didn't follow any script with an underdog team setting the fastest overall time, a Michelin Cruiser Class car coming in second fastest and many of the favorites struggling to set a competitive time at all.

Pole position goes to Australian TeamArrow, a Queensland based team associated with the Queensland University of Technology who set a lap time 5 seconds clear of the entire field. Second in the Schneider Electric Challenger Class is Japanese team Kogakuin University Solar Vehicle Project with a close third place going to the Stanford team with Luminos.

Of the favorite teams, University of Michigan are fifth in the starting order with Nuna7 starting lucky 13th having set a time 33 seconds off the pace while Tokai Challenger starts 20th after spinning twice at the final corner leading onto the main straight. The 'official' reason given is sand on the track although only one other car spun at that corner, the Hochschule Bochum SolarCar Team who still qualified third in the Michelin Cruiser Class.

Of all the asymmetric cars (with the driver positioned on one side of the car) in the 2013 Bridgestone World Solar Challenge, Tokai Challenger is the only car with rear wheel steering which may have contributed to the car spinning each time it negotiated the final turn at Hidden Valley. We don't expect there are many hairpin corners along the 3,000 km route from Darwin to Adelaide so this may not be a good indicationn of likely race performance.

On pole for the Michelin Cruiser class, and second fastest time overall is Solar Team Eindhoven with their 4 seater Stella. University of Minnesota starts second with final turn spinners Hochschule Bochum SolarCar Team starting third.

UNSW Solar Racing Team with their Sunswift eVe two seater start forth with a qualifying time 26 seconds off the pace following some drama on their first attempt at a flying lap. Sunswift's eVe literally limped around the Hidden Valley track on it's first warm up lap and came straight back into the pits barely moving under it's own power. The problem turned out to be a seized front brake caliper that was only diagnosed after the team were forced to set a time before eVe could be repaired.

Pole position for the GoPro Adventure class, which includes quite a few older generation three wheeled solar cars that no longer qualify for the outright class, was set by SIKAT Solar Philippines with SIKAT II followed by Aurora Evolution and Team Solaris from the Dokuz Eylül University in Turkey.

This year’s Bridgestone World Solar Challenge is held from 6th – 13th October. If you can’t make it to Darwin or Adelaide, you can follow the race on Twitter via @tsport100 or @WorldSolarChlg.

Disclosure: This post is sponsored by Bridgestone World Solar Challenge. Words and thoughts are entirely my own.

Full results: Bridestone World Solar Challenge

This time next week the world's most energy efficient electric cars will be hitting speeds of up to 130 km/h (81 mph) as they race 3,000 km (1,865 Miles) coast to coast across the Australian Outback contesting the Bridgestone World Solar Challenge.

The outright contenders for line honours will come from the big budget single seater aerodynamic vehicles of the Schneider Electric Challenger Class. The only external energy source allowed during the race is solar irradiation received by a maximum of either 3 square meters of high-efficiency (22.5%+), triple-junction gallium arsenide (GaAs) solar cells or 6 square meters of silicon based solar cells with less than 22.5% efficiency. The solar array is paired with a maximum on-board energy storage capacity of 5 kw/h to assist with energy use strategy, hills, clouds or extra acceleration for overtaking.

To have a good chance to win each car has to 1) Collect as much solar energy as possible and 2) Use as little energy as possible. This means special attention needs to be applied to the efficiency of transferring electrical energy to the wheels and minimising friction from aerodynamic drag and rolling resistance which is affected by vehicle weight amongst other things.

To achieve the electrical efficiency goal, every Bridgestone World Solar Challenge winner since at least 1999 has used a direct drive in-wheel motor to propel the vehicle. Direct drive eliminates mechanical transmission losses that can be as much as 20%.

Solar cars use very low rolling resistance tires that are specially designed for this race with a rolling resistance ten times less than an average road car. With the rolling resistance of a cars tyres accounting for roughly 20% of all energy used, tyres can account for up to one in every five tanks of fuel in a regular road car. Vehicle weight is also kept extremely low with extensive use of carbon fiber, again to minimise rolling resistance.

Tokai Challenger in 2011 won with an average speed of 91.54 km/h (56 mph). With such high average speeds combined with the physics of air resistance being proportional to the square of speed, aerodynamic drag is the main source of losses on a solar race car. Much design effort is invested in CFD computer simulation, scale and full size wind tunnel testing. The best solar race cars achieve a drag coefficient as low as 0.07 (Nuna 3 – which holds the record for highest average winning speed @ 102.8 km/h) where a road car ranges from 0.24 (Tesla Model S) to 0.35 (Toyota Land Cruiser).

It is the chase of maximum aerodynamic efficiency that has lead to the race winning dominance of “coffee table” type vehicle designs which brings up the question of how practical can a solar-powered vehicles be? The 2013 Bridgestone World Solar Challenge sees the introduction of the Michelin Cruiser Class which is not focused on speed but practicality, with the ultimate goal of entrants being able to meet the requirements for road registration. Cruiser Class cars must seat a minimum of two people and will be allowed over-night battery charging at select locations.

While the Michelin cruiser class aligns solar race car design more closely with road car requirements, if the limitations of having the solar panels on the vehicle itself are removed, powering a regular road going EV with solar power is an affordable reality today!

Tesla Motors recently launched a network of solar powered superchargers capable of charging their Model S to 320 km of range in 30 minutes. Even a modest 1.5 kw residential roof-top PV solar system generates enough energy to power a commuter EV like a Nissan Leaf for more than average annual mileage. In fact, displacing the cost of petrol instead of grid power will reduce the break even time on a roof-top PV installation to just a few months.

This year’s Bridgestone World Solar Challenge is held from 6th – 13th October. If you can’t make it to Darwin or Adelaide, you can follow the race on Twitter via @tsport100 or @WorldSolarChlg.

Disclosure: This post is sponsored by Bridgestone World Solar Challenge. Words and thoughts are entirely my own.