Startups, researchers and carmakers are working on a new way of powering transport that one day may be no more unusual than a hybrid-electric Prius: Cars that drive on self-generated energy straight from the sun.
There are already a number of prototypes and concepts of solar-powered vehicles, from the eponymous and aerodynamic Lightyear One, designed and developed by Dutch startup Lightyear, and the planned Sion by German solar car startup Sono that smashed crowdfunding targets recently to the tune of €53 million ($A85 million).
Hyundai has even unveiled a hybrid Sonata with photovoltaic (PV) panels integrated into its roof (it was first launched in South Korea in 2019) that it claims can add an extra 1,300km a year in driving range to its small battery from six hours of sunshine a day.
Then there’s the World Solar Challenge, among other solar car races, for which solar car technology is pushed to the limits and in which Australia’s own Sunswift solar racing team from UNSW excelled in 2019 coming second only to the Dutch Team Eindhoven.
The motivations for developing solar-powered cars are many.
Electric cars can already help reduce Australia’s dependency on petrol and diesel – the country currently has only has 18 days fuel in reserve, 75% of which is used for transport – and reduce transport-related carbon emissions, which accounts for 23% of all carbon emissions.
Being able to charge a car directly off the sun, however, is also a boon for those without the ability to install their own solar panels at home, or wanting to reduce consumption of energy powered from a grid still reliant on fossil fuels.
But how close are we really to seeing solar cars a part of every day life? What would the benefits be, and for what price? And how far will they really be able to drive on free power sourced purely from the sun?
At an event hosted by the UNSW Digital Grid Futures Institute on Tuesday, experts in the research, marketing and realisation of solar cars pondered these topics.
“Thirty kilometres a day in Japan might not sound like much but it’s more than 70% of passenger journeys in Japan,” Ekins-Daukes said.
“Actually most of us day-to-day don’t drive very far day to day – of course, people go on holidays and we do long road trips but most of the time we are making short trips.”
To increase solar range, Ekins-Daukes says that options are to use more panels on the vehicle, increase the efficiency of the vehicle, and use more efficient, but relatively affordable, cells.
While standard silicon crystalline cells (that are about 20% efficient) used on rooftops costs only 20c/watt, the upper range of PV tech (such as used on the Airbus Zephyr and are 35% efficient) can cost upwards of $100/watt.
Obviously, more expensive and efficient cells would increase range – but blow the price of cars using them out of the water making them a commercial failure.
“The challenge for us as PV researchers is to make technologies [that are more efficient]. We need something more affordable, but importantly, it doesn’t need to be super cheap [like silicon crystalline cells].”
Bonna Newman, program manager and senior scientist at Dutch research facility TNO, says that solar cars offer the opportunity to not only reduce carbon emissions associated with charging electric cars from fossil-fuelled grids, but also reduce the number of times they need recharging per year.
“We can talk about extended range – but what does it mean on a day-to-day basis? What does it mean about your planning and your needs … and your dependence on the grid?” said Newman.
In tests conducted by Newman using 750 watts worth of PV on a car, it was shown that a solar car could reduce the number of times plugging in to recharge per year by up to 80% in Madrid, Spain – and Newman says this would be similar in Australia.
Savings could be up to €354 ($A573 converted) and 410kg of CO2 emitted a year, based on the Madrid scenario says Newman.
Newman is working with Dutch startup Lightyear, which is a spinout of the Solar World Challenge.
“They are one of the companies worldwide that are trying to make this a reality … about a year ago we developed the first full sized car roof prototype,” Newman said.
With over 90% of the roof area covered in active cells getting more 19% efficiency on the generation 1 prototype, the team achieved 86% module performance and Newman believes it is possible to get 1,000 watts on a car.
“This design is now being integrated by Lightyear on the car in California,” she says.
Cars are not the only application for this technology, of course. Newman notes that she is also working with solar train company Trens, and solar truck maker IM Efficiency for auxiliary power and refrigeration of goods, and Pic Nic which is using solar on their delivery trucks to prove applicability and feasibility.
Newman thinks that within 20 years solar on vehicles will be a reality.
“This technology is in its infancy and we’re really just taking first steps right now in developing this technology and bringing it to the world,” she says.
“We are picking up steam on it, and soon we are going to be running, and as we run we’ll be changing the world together.”
This article has been updated to correct the efficiency of III-V cells used on the Airbus Zephyr, which is 35%. The highest demonstrated efficiency of solar cells is 47%.