Wake up daily to our latest coverage of business done better, directly in your inbox.


Get your weekly dose of analysis on rising corporate activism.


The best of solutions journalism in the sustainability space, published monthly.

Select Newsletter

By signing up you agree to our privacy policy. You can opt out anytime.

Tina Casey headshot

Solving the EV Charging Problem, with Mobile Solar Energy

Toyota and its partners are testing an electric vehicle with built-in solar panels, providing mobile solar energy and offering more range and freedom from fossil fuels.
By Tina Casey
Mobile Solar

Electric vehicles (EVs) could soon be a major part of the mainstream car market, but buyers are still wary of the time it takes to recharge an EV battery. Toyota and its partners in Japan are working to overcome that obstacle. They are testing an EV with built-in solar panels for mobile solar energy. If all goes according to plan, fleet managers and other vehicle buyers could have some interesting new options in the future.

The time has come for mobile solar energy

The basic idea behind equipping a car with solar panels is simple enough. Built-in solar panels can provide additional solar energy to an EV battery while the vehicle is in motion, in addition to recharging the battery when the vehicle is parked.

In terms of bottom-line benefits, the extra electricity would provide drivers and fleet managers with more options to operate their fleets more efficiently. They could plan for longer trips between charging times, because the vehicle could remain on the road for longer periods.

Fleet managers could also plan trips that don’t require regular access to charging stations. The car could simply recharge its battery while parked in any spot where sunlight is available.

In addition, fleet managers could have more flexibility to plan trips around the most convenient opportunity to provide for a full recharge at a charging station, however long that may take.

What’s holding back the mobile solar fleet of the future?

Until recently, solar-equipped cars were not entirely practical. Conventional silicon solar panels are relatively heavy. For EVs, the added weight offsets at least some of the battery range gained from solar energy.

Conventional solar panels are also not ideal for plug-in hybrid EVs. The added weight could result in a loss of fuel efficiency (plug-in hybrids run on both gasoline and electricity from a charging station or standard outlet).

Fortunately, conventional silicon solar panels are no longer the only solar energy option. Lightweight thin film solar cells are coming into use for small mobile devices, as well as backpacks and items of clothing.

Thin film is also flexible, so it can be molded around the curved parts of a vehicle.

Last year, the startup Sono Motors introduced the idea of built-in solar panels integrated with lightweight body materials.

Toyota’s approach is similar, though the solar panels are attached rather than fully integrated.

Solar panels on electric vehicles

Toyota is producing the new solar-powered EV demonstration in partnership with Sharp and NEDO, the New Energy and Technology Development Organization of Japan.

Sharp developed the new thin film solar cell in 2016. The company created it in support of NEDO’s goals for a lightweight, flexible, low-cost and high-efficiency solar energy system for use on vehicles.

Last week Toyota announced that the partners are ready to begin public road testing for the mobile energy project later in July. The tests will deploy a Prius PHV plug-in hybrid with Sharp’s solar cells distributed around the car, including on the roof, hood and rear hatch door.

Reducing carbon emissions from the EV fleet

So far, the tests have apparently demonstrated some improvement over a standard Prius PHV with a solar charging system. The new onboard thin film solar system has yielded an increase of almost 5 percent in power output.

The real proof will be how the new system performs in the real world. Toyota will begin driving the solarized Prius later this month in and around Toyota City, Aichi Prefecture, Tokyo, in addition to other places.

If all goes according to plan, the public road tests will demonstrate that on-board solar energy can boost the fuel efficiency of plug-in hybrids and provide for longer drives between charges.

For companies seeking to improve their carbon footprint, the implications are clear. The new system would enable plug-in hybrids to go off grid for longer periods.

That would help reduce carbon emissions related to companies that currently rely on grid-supplied power to charge up their EV fleet.

That’s because in many areas, fossil fuels still play a key role in the power grid.

Getting a leg up on the future

Companies seeking an EV or plug-in hybrid solution for carbon emissions are facing a dilemma. As more electric vehicles enter the market, demand for more fossil-sourced electricity could also increase.

Alternatives like on-board solar energy could provide businesses and fleet managers with the opportunity to push their carbon footprint down more quickly than the local power grid.

If the public demonstration meets expectations, fleet managers will also have some hard data in hand to make the case for solar-equipped vehicles.

Toyota and its partners plan to evaluate the impact on carbon emissions and improvements in convenience and efficiency, too.

Image credit: Toyota

Tina Casey headshot

Tina writes frequently for TriplePundit and other websites, with a focus on military, government and corporate sustainability, clean tech research and emerging energy technologies. She is a former Deputy Director of Public Affairs of the New York City Department of Environmental Protection, and author of books and articles on recycling and other conservation themes.

Read more stories by Tina Casey