Rooftop Solar Charging

[pineapple]

That being said, I never said it was gonna be cheap. My guesstimate at least 12 to 15 K.

 

[AeroWolf]

Just remember, the daily average continental US solar power is 1 kwh per square meters per day. And the Slate footprint is not quite 8 square meters. You might get 5-7 kWh a day for when considering practical factors that limit collection efficiency.

 

[Tom Sawyer]

I haven't seen this specific setup covered in this forum. Apologies if I've missed it.

I'm very seriously considering installing a collapsible solar panel array (500-600 watts) on the roof of the Slate, and collecting the power in a stand-alone battery generator, with the intent of dumping the stored charge into my Slate via Level 2 charging every day or two.

I'm not an engineer, but I am a technician, and pretty good at electro-mechanical DIY. I also acknowledge that there's a wealth of smart people in this forum, and I would love to hear any thoughts or suggestions about this idea.

Use-Case: My daily commute is about 16 to 20 miles, mostly freeway. I'm thinking about attaching the solar panels in a collapsible or folding configuration, using Slate's roof rack, either with or without SUV kit. I haven't decided what standalone generator to use, and I'm open to a piecemeal approach if that's more economical or efficient. I'm thinking of putting the equipment in the frunk.

Tell me your thoughts! Any and all comments are welcome and appreciated.

Try it! What have you got to lose? Sounds like a fun experiment.

 

[ScooterAsheville]

In Europe, they have balcony deployable solar. In the US, you can buy portable solar-battery combos, and use the power for anything. Here's one of many OEMs. Do keep in mind that most BEVs are power hogs. They don't sip electrons through a straw, but through a firehose.

https://www.bluettipower.com/

 

[kvermeer]

Someone will be along shortly to do the math, I'm sure, so I'll leave that to them.

Sorry I'm late.

Let's assume a pair of 58x36" 300W rigid marine panels up on ladder racks or as a rigid "tonneau cover."

Here in Michigan, we get an average of 3.8 peak sun hours in horizontal irradiance (assuming a clear view of the sky). If you tilt the panels up towards the equator at 30-45 degrees and if you turn the truck so they're facing southeast in morning and southwest in the evening, you can do maybe 25% better, but for the simplest install you're looking at 1.8 kWh/day average (a measly 0.8 in winter and 2.6 kWh/day in summer) from that 600W array.

The truck will have some parasitic drains - internal cell losses, always-on electronics, and especially the battery heating in winter - that will draw it down 1% or so per day.

But ignoring those losses, at roughly 2.9 miles per kWh, that would give about 5 miles of range in a day. And you're carrying a couple hundred pounds of weight, adding 25 sqft (horizontal, but still) of drag, it costs about $2500 for a good set of marine-rated 300W panels, maybe $3000 total... For 5 miles of range per day.

Yeah, if you double or triple that investment into a fold-out array with all that complexity, you can do 10 or 15 miles per day, but the $10k investment for that buys a lot of watts at a DC charger. Or you could put a lot of static solar panels on a roof or whatever, and plug into that array instead of driving it around.

 

[ElectricShitbox]

Worksport makes a solar tonneau cover intended to charge a battery bank
https://www.worksport.com/products/solis

 

[2thlesswithta2s]

Assuming a 600W panel & some efficiency loss because you're never going to get it perfectly aligned to the optimum exposure angle, at peak conditions you're likely only adding 1 mile of range for every hour of solar charging.

So this isn't really a strategy for fully charging; it's just a way of extending your range a bit. You might get 4 or 5 extra miles on a sunny day. If I get some time I might do the economic calculations on how long it takes for the panels to pay for themselves.

 

[Tom Sawyer]

Who will be first to market a bed cap made of PV panels! That stuff would sell. Off grid camping and all that.

This place is just bursting with great, paradigm-shifting ideas!

 

[danielt1263]

Instead of the roof rack, how about a tonneau cover? Something like this? https://www.worksport.com/products/solis

 

[ScooterAsheville]

If you look at the accessories of the Telo build, you can get a solar roof or tonneau. Real money though, so you have to be swimming in the stuff.

https://build.telotrucks.com/

 

[sodamo]

There have been very good discussions on this topic in past, highly recommend finding them. I myself was very very interested and contributed a bit. Remember, the solar pnels are just part of the solution, still have to get those electrons into the battery.
The tonneau cover above has inverter/battery available, but 120v, meaning Level One, hence slow charging but only when not driving. Do check the numbers, not a lot of capacity. Not charging truck while driving.
Telo apparently licensed the Aptera technology, but i haven’t seen details.
Almost viable solution is Bluetti, the Apex 300. This provides about 3.8kw but at 250v, therefore Level 2. This unit can be charged various ways, up to 4kw solar. Battery portion is expandable. I would consider this a viable emergency backup for maybe 10 miles! But likely decent for camping. Again, not charging truck while driving.

My solution at this point, add 8kw PV to my current off grid system with a dedicated Level 2 charger. keep Slate @ 80% unless I knowingly need 100%. Could still opt for the 240v backup, but that money could pay for lots of commercial charging. I no longer camp, don’t foresee carrying a standalone system.

 

[cadblu]

For those living in sunny southwest regions, e.g. Arizona, Nevada, New Mexico, it would definitely make sense to pursue some kind of solar solution. Along with some kind of mechanism that can maintain the optimal angle of the solar arrays with the sun throughout the day.

 

[E90400K]

For those living in sunny southwest regions, e.g. Arizona, Nevada, New Mexico, it would definitely make sense to pursue some kind of solar solution. Along with some kind of mechanism that can maintain the optimal angle of the solar arrays with the sun throughout the day.

The Hummer EV "crab" function comes to mind.

 

[JustChris]

Let's assume a pair of 58x36" 300W rigid marine panels up on ladder racks or as a rigid "tonneau cover."

Here in Michigan, we get an average of 3.8 peak sun hours in horizontal irradiance (assuming a clear view of the sky). If you tilt the panels up towards the equator at 30-45 degrees and if you turn the truck so they're facing southeast in morning and southwest in the evening, you can do maybe 25% better, but for the simplest install you're looking at 1.8 kWh/day average (a measly 0.8 in winter and 2.6 kWh/day in summer) from that 600W array.

The truck will have some parasitic drains - internal cell losses, always-on electronics, and especially the battery heating in winter - that will draw it down 1% or so per day.

But ignoring those losses, at roughly 2.9 miles per kWh, that would give about 5 miles of range in a day. And you're carrying a couple hundred pounds of weight, adding 25 sqft (horizontal, but still) of drag, it costs about $2500 for a good set of marine-rated 300W panels, maybe $3000 total... For 5 miles of range per day.

Yeah, if you double or triple that investment into a fold-out array with all that complexity, you can do 10 or 15 miles per day, but the $10k investment for that buys a lot of watts at a DC charger. Or you could put a lot of static solar panels on a roof or whatever, and plug into that array instead of driving it around.

Well, dang. That's not the math I want to hear, but perhaps you're exactly right. I would love to harvest my own power, using equipment I own, but I may have to face facts that it doesn't make sense for me.

Thank you for your honest feedback.

 

[ScooterAsheville]

Having watched the solar industry for decades now, it has the same long term trend as BEVs. Better for cheaper over time.

I have to confess that after doing the math after incentives ended, I decided to go with a whole house propane generator for the next 5-10 years. I'm waiting for 100% fireproof and lifetime batteries - they're coming. But they're not here.

But at some future point people will just look at you like you're from another planet if you don't have solar + battery in your house, connected to a virtual grid so it earns you money.