Image: Sunswift team and their solar car – Violet | UNSW
The UNSW Sunswift solar car team last week set a new Guinness World Record for the lowest energy consumption driving trans-Australia with an electric car.
The student team completed the 4,100km journey between Perth and Sydney two days ahead of schedule and averaged energy consumption of 3.25kWh per 100 kilometres, well under the 5.5kWh/100km needed to set the record.
The Sunswift team was aiming for the energy cost to be less than that of a single tank of fuel. The total costs for the trip turned out to be $50.
Traveling an average of 600 kilometres each day, the trip was without incident – but it seems Violet is a bit of a handful to control.
“Violet is lively on the road a lot, it’s not a production car and you have to kind of handle it like a horse in order to manage it on public roads. But we did it,” said Sunswift team member Hayden Smith.
About Violet
Violet is the sixth solar car designed and manufactured by the Sunswift team and its first four-seat, family-oriented vehicle.
Violet has a length of 5.0 metres, width of 2.2 metres and stands 1.2 metres high. The vehicle weighs just 360 kilograms, thanks in part to its lightweight chassis of carbon fiber monocoque with foam and an aramid honeycomb core.
The car’s solar array consists 318 SunPower monocrystalline silicon cells with a conversion efficiency of approximately 22%. These charge a 10-20 kilowatt-hour lithium-ion battery bank that power twin rear wheel in-hub, brushless DC synchronous motors. Violet has a top speed of 140 km/h.
Violet also features front and rear boot space, reversing camera, parking sensors, an interactive display screen with GPS, plus other creature comforts such as air-conditioning.
“These students have pushed the boundaries of modern engineering and proven that solar powered cars are likely to be a big part of Australia’s motoring future,” said UNSW Dean of Engineering Professor Mark Hoffman, who met the team at the finish line in Sydney.
Gearing Up For Next World Solar Challenge
The team will be busy in the new year preparing for the 2019 Bridgestone World Solar Challenge, which covers 3,000km from Darwin to Adelaide.
Sunswift will be hoping for a better result than the last time it participated in 2017, when rear suspension failure forced the team to drop out of the race. However, Violet still achieved a very respectable third place in Practicality judging of the Cruiser Class of the Challenge.
The Cruiser Class is for efficient, practical solar cars with two or more seats.
“Cruiser Class teams aim to change the way we think about what we drive and what fuels we use,” states the Bridgestone World Solar Challenge web site.
Next year’s Challenge will be held October 13 – 20.
The Sunswift Solar Car project has been running at UNSW for 23 years.
About Michael Bloch
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I believe that I did not see the information in the above report –
1. whilst the vehicle apparently has a maximum speed of140km/hr, at what speed was it mostly crusing, and, what is its cruising speed?
2. whilst the vehicle is stated as being a four seater, with cargo space front and rear, what payload was it carrying – weight of people and weight of freight/cargo/luggage, during the trip?
A bit of rummaging around the net & I discovered that at speeds up to 60 kph the car can run solely on the solar panels covering its body. That ties in well with their 600 km/day average as, assuming sunny days, it can be achieved by running for 10 hrs at 60 kph without drawing on the battery. The battery will kick in if there’s inadequate sun or hills increasing the load. If the battery gets too low the car would be parked while it recharges itself from its solar panels.
Apparently there was a driver & passenger 90% of the time.
OK, but…
The 3 kW array on my roof has 20.4 sqm of panel area. Conversion efficiency for those panels (2010 Suntech) was 15%. Upgrading to the 22% efficiency quoted in the article brings the equivalent area down to 13.9 sqm which is about 2.8 times the maaximum allowable 5 sqm of modules. So, the array on the car should be closer to 1kW. Even if we’re generously allowing 10 peak hours of sun that should only account for 10kWh per day, and that’s assuming perfect energy transfer with no other losses.
Perhaps I picked up a wrong figure somewhere?
As I said in my post (below), this is still awesome…
Firstly… awesome. Every year these look more and more like real, drivable cars that wouldn’t seem too out of place on the roads. I remember the old days where the winning car looked something like a ping pong table on wheels with a bubble for the drivers helmet, more like a mutant trike than a car.
However, I expect the competition has also evolved a little since then. A quick bit of maths (600 km, 3.25 kWh per 100 km) tells me the average energy use was 19.5 kWh per day, which is about as much as my 3kW home system (16 190W panels) generates at the peak of summer. There’s no way that the surface area of these cars could carry my system – in fact the maximum allowable solar module area is only 5 sqm (or less depending on chosen cell type) according to the 2019 regulations (which you can find online).
I therefore have to imagine that the focus of the challenge has moved from solar cars to electric cars (with assistance from solar). And… I’m fine with that. It’s a more realistic use case for future transport on a large scale.
Yes – its difficult to find really solid info & I can’t find anything about their operating strategy. The car does have a 10-20 kWh battery so between that & the solar panels you have easily got the 19.5 kWh you calculated it used per day. Once the battery is run down, though, it would have to be recharged, so maybe every other day they drive real slow or park it in the sun to recharge.
How much does the sunswift VI violet cost? In australian dollars.