Projects, Renewables, Solar, Storage

Solar’s race to the bottom

It’s a long way from Darwin to Adelaide but the blistering sun provides perfect conditions for a solar car race. Vincent Ross reports from the 2017 Bridgestone World Solar Challenge.

As the cost of solar PV keeps dropping and piles more panels are fixed to Australian rooftops, it’s nice to be reminded the technology also powers a famous and arduous car race.

Dutch ingenuity came to the fore in the 2017 Bridgestone World Solar Challenge when the Netherland’s Nuon Solar Team Challenger Class vehicle won the gruelling 3,022km desert race.

Beginning in Darwin on Sunday October 8 and travelling south on the Northern Territory’s Stuart Highway to reach Adelaide in South Australia by the following Saturday, Team Nuon’s Nuna9 crossed the finish line two days early and nearly two hours ahead of the University of Michigan’s Novum in second place.

It was the seventh win for the Dutch, no mean feat, even for a team with a wealth of experience on its side. But it’s not an easy road for first-time challengers, who need more than just enthusiasm to get to the start line.

German Team Sonnenwagen had to build a car from scratch and it took two years of planning and lobbying to encourage a raft of sponsors to come along for the ride.

The team managed to recruit 40 corporate sponsors, including German polymer and polycarbonate manufacturer Covestro, prestige car brand Porsche, vehicle paint surface specialist PPG and Chinese telecommunications giant Huawei.

Mobile laboratory

For Covestro the race was an opportunity to use the Sonnenwagen as a “mobile laboratory” for its new polyurethane curing agent Desmodur, which is 70% made from biomass material, including corn starch derived from maize.

Covestro is no stranger to backing technological adventurers. In 2016 it supported the Solar Impulse on its 40,000km flight around the world without burning a drop of fossil fuel.

Solar Impulse, powered by 17,000 solar cells on a wingspan equivalent to that of a jumbo jet, was the brainchild of Swiss adventurers Bertrand Piccard and Andre Borschberg. A spectacular demonstration of permaculture thinking and clean technologies, the high-altitude flight required special insulation developed by Covestro.

A spin-off from German industrial giant Bayer, Covestro focuses on developing polymers and polycarbonates and new technologies that reduce the use of fossil fuels. It is involved in the development of polycarbonates in the production of wind turbine blades in China and is using carbon dioxide instead of oil in the production of polyurethane foam. The company says up to 25% of oil currently used in making foam for mattresses can be replaced with carbon dioxide.

Huawei provided six-figure financial support and made available communications equipment, which kept the support team and its mobile monitoring system in constant contact with Sonnenwagen on the 3,022km journey, travelling front and rear in vehicles provided by Porsche.

Porsche gave the Sonnenwagen team access to its Weissach Development Centre, its Motorsport Centre Flacht to research aerodynamics, electrical circuitry, airfreight logistics and team management, and took them to the FIA World Championship Spa in Belgium to study weather monitoring and racing strategy.

Degrees of experience

What the 45-strong team of engineering students from Germany’s RWTH Aachen University in association with Aachen University of Applied Sciences lacked in experience they made up for in enthusiasm. All aged in their mid-20s, with most in their last year of completing electrical, aerodynamic or mechanical engineering degrees, these are the world’s new generation of sun worshippers. But unlike the Aztecs, the sacrifice of Team Sonnenwagen was their own blood, sweat and tears.

“We knew we would have difficulties competing with teams who have been in the solar challenge for 15 years and have very large sponsor networks,” said Team Sonnenwagen vice-chairman Niklas Kaltz. “This is the challenge of a lifetime. Solar power and sustainable mobility are key technologies for the future. This is our small contribution to improving our world. It has helped us put our acquired knowledge into practice.”

For Niklas, e-mobility – the development of electric-powered drivetrains to shift vehicle design away from the use of fossil fuels – is a passion.

“In Germany and Europe and in Asian cities, e-mobility will be key in reducing emissions and making cities cleaner,” he said. “E-mobility is the first requirement for solar mobility.”

Getting the Sonnenwagen (“sun wagon”) to the start line took two years’ of lobbying for sponsorship, planning, testing and building, before the team even faced the humidity, heat, changeable weather and gritty winds of the long desert crossing.

Get set…

On race morning in Darwin’s State Square, team chairman Hendrik Lobberding was quietly confident. It was 7am and the rest of the team were having breakfast. The race would start for Sonnenwagen at 8.40am.

“We have run our weather and strategy simulations to determine initial speed. We are ready to go,” he said. “Our aim is to be the best newcomer.”

Sonnenwagen performed well in the prelude to the race, reaching 122km/h and clocking 2 minutes 15.9 seconds at an average speed of 76km/h in time trials at Darwin’s Hidden Valley race track.

Coming fifth in the trials, it was an excellent result for the first-time racers and close on the heels of solar challenge veterans Nuon Solar Team in fourth place, whose Nuna9 lapped at 2 minutes 14.1 seconds at an average speed of 77km/h.

The drivers had clocked Sonnenwagen at 130km/h and the young engineers knew it could go faster, but this race wasn’t about speed – it was about ingenuity and endurance.

Travelling at between 60km/h and 70km/h, the four drivers took four-hour shifts behind the wheel in a tiny, hot cabin with no air-conditioning, two litres of water each. They had harnessed the sun but it also was their enemy.

“The Sonnenwagen has a vent that lets fresh air into the cab,” said mechanical engineer and driver Marc Locke. “If you drive faster the temperature is quite OK, but if it’s really cloudy and you slow down, it gets really, really hot.”

Road noise was a major issue, with the endless hours of humming wheels on hot bitumen reverberating beneath Sonnenwagen’s sleek shell.

Shell be right

The team built the Sonnenwagen from scratch and only in the final months leading up to the race completed the critical power plant, a 1.4kW gearless wheel-hub electric motor, the product of designers Marc Locke and electrical engineer Enno Dulberg. The motor weighs 11kg and the battery that stores the electricity to power it weighs 20kg.

The motor is 98% efficient in turning solar-generated electricity into traction. With the battery fully charged, Sonnenwagen has a range of 300km.

As it took shape, Sonnenwagen became a thing of sleek beauty, more than fitting to wear the badge of Porsche. At 4.3m long, weighing 216kg, with a 260-cell solar panel covering four square metres providing a peak output of 920 watts, Sonnenwagen has a maximum speed of 140km/h, an average speed of 70km/h and consumes 1.8kWh/100km.

Of the 38 teams that fronted the starting line in Darwin 21 had been downgraded from the competitive Challenger Class to Adventure Class by the time they reached the finish line in Adelaide due to technical problems or failure to make check points, with Sonnenwagen ninth out of a field of 23 vehicles.

“We had a lot of trouble with the weather from day two to day four,” said Niklas Kaltz. “We had cloud cover and some quite heavy rain.”

On day five, with nine tenths of the journey behind them, Team Sonnenwagen missed the check point at Coober Pedy, 194km north of Adelaide, by 10 minutes.

“That placed us in the non-competitive Adventurer Class, but we still finished,” said Niklas. “I think the journey changed our lives, it built character. Everybody really developed. It’s definitely made us better engineers.”

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