Comment by mattmaroon | Hacker News Reader

Comment by mattmaroon | Hacker News Reader

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Ha, nobody's camper has 2kw solar on the roof. You've got a huge installation if you've got half that. Your roof has ACs, skylights, vents, ect to work around. I've got a 35' travel trailer I live in 4 months a year (and that's close to as bit as they get) and I think I could get 1,200w up there if I really squeezed. I took some measurements because I'm planning to.

RVs are often parked in full sun at least, but even then. I think I'd be lucky to get more than 5kwhh a day. Which is great for me as long as I'm not running the ACs. But that would not even remotely account for the extra drag it put on an EV to trailer it ten miles.

There've been attempts to make "solar paint" for cars, which would be lovely if possible, but even then I think the economic argument will essentially never work out when you factor in time value of money. As the original article said, the economics will likely always be much better for putting the solar panels on your house and charging at home.

It’s true many RV’s have a lot of random junk on their roofs but this discussion is about what happens if you optimize the vehicle for solar at the design phase rather than trying to slap whatever you can after market.

Here’s a random 2.6 kW example which still has a great deal of wasted space. https://youtu.be/Ekoh_QhiJJI

5th wheel with 3kW and still a significant amount of wasted space. https://youtu.be/BPTfkocNEu4

>Here’s a random 2.6 kW example which still has a great deal of wasted space. https://youtu.be/Ekoh_QhiJJI

Did you watch that video? The solar panels are not even able to fully handle their appliances and AC, and they still use a generator to supplement. They aren't used for charging a car battery at all.

>but this discussion is about what happens if you optimize the vehicle for solar at the design phase

It still doesn't change the equation because you're not looking at a order of magnitude difference. In the case of RVs and the YouTube videos you posted, you don't need to worry about what happens if you 'optimize' a vehicle for solar during a design phase - just do a back-of-the-napkin calculation by doubling the output and ... nothing changes. The challenges are the same. The use-cases are still the same (namely, hope for sunny days to generate power to run some appliances). You're still not making any meaningful progress towards extending EV range - and that's assuming double output (and you're not going to get double in the real world).

That’s moving the goalposts you just said, “nobody's camper has 2kw solar on the roof” and yet here’s several people who do.

Clearly a camper that people live in has different demands for things like AC and a microwave than a car that’s just sitting around empty most of the day. A 15.5 foot long car is half the length and nearly the same with so downscaling a 3kW system to ~1kW seems perfectly reasonable.

Toyota built a demo by sticking solar panels on a stock Prius and says it added roughly 25 miles per day of range. That would cover the majority of what the average American drives per year. Yes most people would still need to charge their cars, but suddenly using a normal outlet at home rather than paying for a level 2 charger looks reasonable. So not only are you saving on electricity but also instillation costs.

>That’s moving the goalposts you just said, “nobody's camper has 2kw solar on the roof” and yet here’s several people who do.

I'm not sure where I've said that because I'm not against solar panels on campers or solar panels in general. Solar panels make a lot of sense in a lot situations. For example, I don't think it's a bad idea for an RV that is frequently off-grid to have them built-in to provide whatever power they can - after all, some power is better than no power. Solar panels on outside parking lots, that makes a ton of sense to me.

Solar panels for EV range extension does not make any sense.

>Toyota built a demo by sticking solar panels on a stock Prius and says it added roughly 25 miles per day of range.

Again, this is under ideal conditions, and it wasn't meant for range extension[0] (i.e. to charge the car while it's moving). But let's go with that for argument's sake .. so you're looking at a day of charging for 25 miles of range. 25 miles is approximately a 30 mins charge connected to the grid. That makes no sense. If you really want to use solar to power your EV just get regular rooftop solar and charge your car from your mains.

[0]https://www.torquenews.com/8113/toyota-prius-solar-game-chan...

I said it and I didn’t mean “nobody” literally but it is very uncommon, even amongst people who do expensive solar installations.

And as the original article points out, when Toyota says they add 25 miles per day, they are doing so under nothing even remotely like real world conditions. They’re surely counting on full sun, flat driving with no air conditioning running, etc. An actual user likely wouldn’t even get half of that.

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