In a past article, I went through some of the interesting projects people were pursuing for solar cars. While functional, and even useful in some cases, some solar experiments were rather unelegant. In this article, I want to let readers know about a cool project that is making it easier for anyone to have an elegant, simple, and efficient solar EV charging setup.
But before I get to the new part that’s in development, I want to address the skeptics a bit so that we can all appreciate the value of what’s going on here.
Why Solar Cars Aren’t Really A Thing Yet
I hear people throw lots of numbers out there, and I see lots of people try to say that solar cars will either be very useful, almost worthless, not worth the cost, etc.. I could explore and confirm or debunk the numbers, but Jason at Engineering Explained basically took care of that for us.
Charge EV Batteries With Solar Panels
By the time you factor in the losses, you’re realistically looking at getting anywhere from 2-4 kWh of battery power per day of charging if you cover the whole car in solar cells and keep the charging efficient. 2-4 kWh isn’t nothing, like the naysayers say. It’s about the same as 2-3 hours of level 1 charging.
Whether that’s useful is heavily dependent on not only your daily driving needs, but also your vehicle’s efficiency. For something like my Nissan LEAF, putting some cells on the roof yields around 8-10 miles of driving range per day. My normal daily driving needs are roughly 40 miles per day on school days, so it doesn’t make much sense. But, if I were to switch this out for an Aptera (which only uses ~100 Wh/mile), then that same 2-4 kWh yields 20-40 miles per day of solar range. So, on good sunny days, that actually would work (especially when you consider that it also charges on days I don’t drive it).
As solar cells get more efficient, on-vehicle solar will become more and more useful, even for vehicles that aren’t as efficient as the Aptera.
The Numbers Look Good to Me, How Do I Add Solar Panels To My EV?
If adding 8-10 miles per day of range sounds like it would be worthwhile to you, it is possible, but it’s generally not a great idea to just start cobbling together different off-the-shelf solar hardware to charge your EV. In another article, I shared the story of Sam Elliott’s solar-powered Nissan LEAF. In his case, he had a LEAF with a very degraded battery, and he was just a few miles short of making it back from work every day. So, by adding solar charging, he could come up with enough charge to get home during his workday.
The problem is that his initial charging setup was quite complicated. He had solar panels mounted to the roof of the LEAF, which went into a pretty standard 12-volt DC charge controller. This charge controller charged a bank of lead-acid batteries. A power inverter took power from the batteries and converted it to 120 volts of AC power. This powered the stock EVSE, which charged the car just like level 1 charging. Unfortunately, it wasn’t providing enough juice to make the EVSE happy, so he had to add a timer to the EVSE so it only charged part of each hour.
It worked, but it took up the whole trunk with extra batteries, power inverter, etc.. Plus, converting from DC power to AC power, and back to DC power, plus other conversion losses, meant it was fairly inefficient.
Making A Better EV Solar Charger
What EV drivers really need to be able to efficiently solar charge is a charge controller that doesn’t waste energy and space by converting the solar cell power directly to the 400 volts most EV batteries need. Fortunately, that’s a new thing that’s starting to happen. The project to build such a circuit board that I previously covered is now ready for others to begin testing.
Not only does the board convert the power of two solar panels to 400 volts, but it also has provisions to be able to close the battery’s contactors and power any other electronics that you’d need to actually get the vehicle charging. In other words, if you wire it up properly, it could add a constant 300 watts of power to your car’s main battery pack in the most efficient and safe way possible.
This isn’t an easy project, but it could still prove useful to the EV community. Most EV enthusiasts won’t have the skills to take this board, bolt on some panels, and wire it all up safely. Electronics technicians should be able to figure it out, but it’s also something independent EV shops and other EV businesses could do. So, if you’re wanting to add solar to your EV without giving up your whole trunk for secondary batteries or otherwise creating an electrical Rube Goldberg machine, it’s now possible.
Why This Matters
Like I said, adding 8-10 miles per day with solar panels might not seem like much to most EV drivers, but it’s enough to make a difference in some situations. It might be a technical challenge, or a desire to bring impacts to absolute minimum. It might actually cover someone’s very small driving needs. Or, someone might live at an apartment or other housing with no access to charging. It could even just be for aesthetics or bragging rights. Whatever the reason, there are certainly worse ways to be parted with your money.
On the other hand, the future utility of solar panels for charging is nothing to sneeze at, either. The best commercially available cells today are around 24% efficient, meaning they’re converting about a quarter of solar energy to electricity. In the near future, cells could jump to as good as 30%. 40-50% is in the pipeline, and 90% is theoretically possible. Even if you can’t get all of the power you want today, it’s very possible that future cells will put you at adding 30-40 miles per day for normal EVs. Even if your experiments only help others test and work toward integrating solar technology, that’s well worth it.
Featured image: Screenshot from Real Solar Cars’ YouTube video (embedded above).