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Part 1 of this article described the California startup DartSolar, which has developed a roof rack-friendly system for attaching solar panels to an electric vehicle. What makes the company unique is its DIY, right-to-repair business model encouraging individuals to modify the system as desired. I reached out to co-founder Omid Sadeghpour for more details and he kindly responded by email. Following is his commentary in full, exclusively for CleanTechnica.
More Details About The Roof Racks:
“For any Tesla, the DartSolar attaches directly to the rooftop of the vehicle, it acts as both a roof rack and the expanding mechanism for the solar panels. For any other electrical vehicle, the DartSolar can connect to any standard roof rack — for example a Thule roof rack.
“The advantages of doing it this way are that for any Tesla vehicle, the aerodynamic profile is much lower, almost an inch lower. For any other electric vehicle, there might be a slight increase in height and that depends on the roof rack that that driver selects.
“The aerodynamic drag loss test described on our website has been done on a Tesla Model Y with the roof rack that we have developed attached to it. And that’s how we got the 2% our dynamic drag loss. Which is a record. From the videos on dartsolar.com you can see that the model we showcase is the one where the DartSolar is the roof rack and the expanding solar frame all in one.
“We can confirm that the expending solar roof rack can be attached to sedans, vans, and SUVs. For very high vehicles where a hand cannot reach the handlebar to expand the solar panels — we place a small hook so that the driver can use a long stick to expand and contract the solar panels — just as easily as in our videos.
“The roof rack can also be attached laterally, so that the solar panels expand side to side. For example, imagine a pickup truck that places this on its truck bed and wishes to expand the solar panels side to side.
“We have designed the frame so that it can also adapt to the different aspect ratio rooftops that exist among different vehicles.”
More Details About The Solar Manufacturer:
“The current manufacturer we use is based in Laos such that we are not be required to pay the anti-dumping tariffs that the US has imposed on Chinese and south-east Asian solar panels.
“We have tried to search for US manufacturers of semi-flexible solar panels, but we have not been able to find any for the custom panels that we need developed. For example, the manufacturer we use has been very flexible and has designed solar panels without the junction boxes so that we can integrate the diode into our frame. They also place XT60 connectors to them, a task that eases our assembly. We’re very open to a US-based manufacturer, perhaps out of this article one can contact us.
“We have gone to great lengths to make sure that the solar panels are easily serviceable and repairable. For example, we have made the solar panels only 23 inches wide so that in case any solar cell breaks, only the faulty solar panel can be replaced. This will decrease the cost of maintenance for consumers.
“The manufacturer that we are working with is also very open to changing the aspect ratio of the solar panels as we please, since they use solar cells of varying sizes. We specifically use the 182 mm solar cell because it just so happens that you can put the most watts in a solar panel with the 182 mm solar cell to maximize the surface area of a Tesla rooftop.
“We specifically targeted the Tesla rooftop because of the great number of Teslas in the US, but we are also looking at BYD and other EV manufacturers.”
More Details About The Solar Cells
Note: In DartSolar’s press release of December 9, the company mentioned they were looking into using tandem solar cells in the future, such as those developed by the Toyota supplier Kaneka and the UK startup Oxford PV. CleanTechnica has been following Oxford’s work in the perovskite solar cell space, including a new tandem version that combines the solar conversion efficiency of silicon technology with the cost savings of perovskite. Here are more details from Sadeghpour:
“In 2024 tandem solar cells sort of exploded and became commercializable. I am right now in Tokyo, for example, trying to connect with Kaneka, which is the solar cell supplier to Toyota. They developed a tandem silicon on silicon solar cell that is about 25% effective in converting light to power. I’ve also reached out to Oxford PV, but I’ve had no luck in developing a semi-flexible perovskite solar panel yet.
“Advantages of Oxford PV tandem solar cells — and by the way there are about a dozen other companies also developing tandem — is that their solar cells can reach a 30% conversion rate, as opposed to the standard 20%. AND also last about 10 years under standard outdoor conditions.
“This means that a tandem solar cell can produce almost 50% more electricity when compared to a conventional mono crystalline silicon solar cell — in the same surface area.
“When you use tandem solar cell power generating numbers on the surface area that we are planning to use in our next design, we should be able to charge an EV 30 to 40 miles per day — assuming Los Angeles weather. Theoretically we should be able to charge an EV 60 miles per day, but when you take into account all the electrical losses the 60 miles per day quickly shrinks to 30 to 40 miles per day.”
Next Steps For Solar Panels On Cars
That concludes Sadeghpour’s email — from Tokyo! — and I thank him again for providing so many details for our readers.
Keep an eye out for more news about Kaneka. The company briefly crossed the CleanTechnica radar back in 2017, for its work with silicon solar cell technology. That was back when the perovskite field was still relatively new and the finicky material was difficult to control (see more perovskite solar cell background here).
By 2022, researchers had developed various strategies for addressing the challenges of perovskite solar cell design. That included Kaneka.
“Using an in-house designed polyimide substrate and drawing on its expertise in the mass production of thin-film silicon solar cells, Kaneka has been developing ultra-thin perovskite solar cells that are approximately 10µm thick—the thinnest in the world—and has already achieved a world-class conversion efficiency of 20% for film-type perovskite solar cells,” the company announced in March of 2022.
As an indicator of how quickly things are heating up in the perovskite field, just one year later Kaneka introduced a tandem silicon-perovsite solar cell featuring a solar conversion efficiency of 29.2%.
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Image (screenshot, reversed): The US startup DartSolar is developing DIY-friendly rooftop solar panels for a variety of electric vehicles, adding miles to the battery, running electric tools and equipment, or providing power in emergencies (courtesy of DartSolar).
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