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Planes, Trains, and Automobiles: Is Transportation the Next Frontier for Solar?

Solar Impulse, DEMU, and the World Solar Challenge are all cutting-edge examples of how solar is finding it’s place in the future of transportation.

With the advent of cheaper large-scale lithium-ion battery technology, integrated solar technology is beginning to be a more feasible addition to nearly every form of human transportation. From the sublime around the world flight in a solar-powered plane by two Swiss adventurers to the mundane practicality of India’s solar-augmented passenger trains, solar transportation isn’t just for space stations anymore.

World Solar Challenge

At the time of this writing, solar cars are crossing the finish line in Australia at the World Solar Challenge. The solar-powered car race first took place in 1987 and has served as a showcase of the latest cutting-edge uses of solar in the automotive setting. The race is a 3,000-kilometer endurance adventure that occurs once every two years.


What began as a race of esoteric-looking single-seater rolling solar arrays now features a “Cruiser Class” of two and four-seater cars that are beginning to look like practical alternatives to petrol-powered vehicles. Event Director Chris Selwood said the Cruiser Class first aimed to deliver a practical demonstration of how the future of automotive technology might look.

“That future is now. These incredible solar cars have been designed with the commercial market in mind and have all the features you’d expect in a family, luxury or sporting car. ‘It’s about so much more than speed. As this part of the judging, based on criteria such as passenger kilometers and energy efficiency draws to a close, we now turn our attention to the most relevant issue of all – do these cars have what it takes to appeal to the consumer?”

In 1987, The General Motors Sunraycer finished the race in just over 45 hours, averaging a speed of 41.5 miles per hour. This year, Team Nuon from the Netherlands won its third straight race, finishing in 38 hours at 56 miles per hour average speed. In the new Cruiser Class, the winner in 2015 was Team Eindhoven’s Stella Lux from the Eindhoven University of Technology in the Netherlands with an average speed of 47.68 mph. As of this post, Team Eindhoven is once again dominating the Cruiser Class in 2017. Selwood said;

“Team Eindhoven are to be congratulated on their achievement to date – clearly the most energy efficient solar car in the field, capable of generating more power than they consume. This is the future of solar electric vehicles. When your car is parked at home it can be charging and supplying energy back to the grid.”
” data-lang=”en”> The Netherlands rule 🇳🇱 🏆🏆Champions in the RACV Cruiser Class & Schneider Electric Challenger Class #takeonthedutch pic.twitter.com/IsBHPosama — World SolarChallenge (@WorldSolarChlg) October 15, 2017

Don’t hold your breath waiting for truly solar-powered cars to arrive at the local dealership, though. Dr. Tom Lombardo at engineering.com points out that:

While Toyota engineers are offering a solar option that extends the Prius’ range by about four miles, European engineering students built an EV whose solar panels can add up to 220 miles to the car’s range, proving that although a solar powered car isn’t feasible, a practical, solar assisted EV is, even with current technology.

To Dr. Lombardo’s credit, he does agree that a solar-charged EV could be considered a “solar-powered car,” but he is correct that a commercially produced car with an integrated, self-contained solar power plant and onboard storage like the Stella Lux is still a long way from hitting the dealerships.

Solar Trains: Solar-Assisted DEMU

Diesel Electric Multiple Units (DEMU) are passenger railroad cars that feature a self-contained propulsion system, eliminating the need for a locomotive. DEMUs are different from other self-propelled diesel railcars as the diesel engines power electric drive units rather than directly propelling the carriage. Now, the Indian Railways Organization of Alternative Fuel (IROAF) program is fitting twenty-four coaches with solar panels to alleviate the reliance on the diesel generators and reduce air pollution in India’s congested urban areas.


In keeping with the Indian Railways (IR) ‘Solar Mission’ to reduce dependency on fossil fuels, IR launched its first 1600 HP solar-powered DEMU (Diesel Electric Multiple Unit) train from Safdarjung railway station in July 2017. The train has six trailer coaches, with 16 solar panels fitted in each of them. The solar panels will power all the electrical appliances inside. Presenting the Railway Budget for 2016-17, Railway Minister Suresh Prabhu announced plans to generate 1000 MW solar power in the next five years. According to the India Express, IR is hoping to reduce 239 tonnes of carbon dioxide emissions by saving approximately 90,800 liters of diesel per train. Indian Railways estimates that just one train with six solar-panel equipped cars will save around $20,000 per year.

Retrofitting Historic Trains with Solar

Meanwhile, in the Australian beachside town of Byron Bay in New South Wales, two vintage 1949 passenger train carriages have been retrofitted with solar and battery storage to create what the Byron Bay Railroad Company claims is the world’s first 100% solar passenger train. The refurbished two-carriage 600 series train will soon be ferrying passengers along about two miles of restored track between the Byron Bay town center and the North Beach neighborhood – home to Byron Arts Estate, Sunrise Beach and Elements of Byron resort.

The train has a capacity of 100 seated passengers plus standing room, and it will operate an hourly shuttle service between stations for $3AUD for a one-way trip.


The project – restoring the train, repairing the track and bridge, and constructing two platforms – has been entirely funded by Byron Bay Railroad Company, a not-for-profit organization founded by mining millionaires Brian and Peggy Flannery, who also own the five-star Elements resort. The projects development director Jeremy Holmes explained;

“Internally the trains have been restored to as close to their original condition as possible. Some people will be attracted to the heritage nature of the train and service; others will be fascinated by the world’s first solar-powered train.”

Solar Air Travel: Beyond Impulse

Flight may be the most problematic form of transportation to power with solar. However, on July 26th, 2016, the world’s first entirely solar-powered aircraft touched down in Abu Dhabi, completing an epic 505-day odyssey around the globe. Piloted by two Swiss adventurers, Andre Borschberg and Bertrand Piccard, Solar Impulse 2 proved that solar photovoltaic generation of electricity could not only power our homes but also power our dreams.

Solar Impulse 2 was not the first around the world flight to rely on solar power, however. The Breitling Orbiter 3 was the first hot-air balloon to circumnavigate the globe, piloted by Brian Jones and… none other than Bertrand Piccard. Piccard’s first successful trip around the globe in 1999 used solar panels suspended below the gondola to power critical systems.


Chances are, a totally solar-powered airliner is probably never going to happen, according to Aatish Bhatia of Princeton Univerity. In a Wired article entitled “Solar Planes are Cool, but They’re Not the Future of Flight” he wrote;

“Sadly, we still have a long way to go in building a viable, greener alternative to conventional flight… I’ve argued that it isn’t even possible – commercial airplanes are about as energy efficient as they’re ever going to get. The Solar Impulse is certainly an impressive technical feat, and it gets us to think more clearly about what really matters when it comes to building a better airplane.”

Professor Bhatia may be correct, but his back-of-the-envelope calculations using current technologies has not stopped the development of prototype electric planes by NASA, France’s Airbus and others. According to NASA’s Tom Neuman;

“While the range of electric aircraft has been growing, limited flight time remains their main weakness. The reason is that batteries are heavy relative to the propulsive energy they provide—by a factor of 10 or more compared with that of gasoline-powered internal combustion. For ground vehicles, designers can compensate somewhat for this shortcoming by adding more or bigger batteries. But aircraft are extremely sensitive to extra weight: Just about every component of a plane’s structure must grow in size for each added kilogram. The requirement for beefier components, in turn, leads to a heavier aircraft, one that requires still more energy and therefore larger batteries to fly. This vicious circle means that for electric-plane design, adding batteries to boost range isn’t a viable strategy.”

For Now, Solar Assisted Transportation

For now, fully solar-powered transportation is still in the future. However, integrating solar generation into current transportation, from cargo ships to city buses is a completely viable option and can reduce fuel consumption in nearly any system that is currently relying on robbing power from the main engine to generate electricity. Air conditioning, lighting, and any other electrical needs could be handled by lithium batteries and solar, or at the very least augmented. In the words of Solar Impulse’s Bertrand Piccard;

“If an aircraft can fly day and night without fuel, propelled only by solar energy, let no one claim that it is impossible to do the same thing for motor vehicles, heating and air-conditioning systems, and computers. This project voices our conviction that a pioneering spirit with political vision can together change society and bring about an end to fossil fuel dependency.”

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