A friend’s Facebook feed today contained a link to this article about an RV covered in solar cells.
The title of the piece is “This Solar-Powered RV Runs Without Fuel Or Charging Stations,” and in the body of the article it says:
All of this suggests to me that you can keep the RV running, both on the road and in terms of the power needed for living, just from the solar cells. It does seem to have an input that allows charging from a charging station (like a Tesla), but the whole implication of the article is that you don’t need this to keep it going. All you need is the solar cells.
I’m not electrical engineer, and so i might be way off base here, but i was under the impression that you need a LOT of solar cells to produce a relatively small amount of electricity. I don’t exactly know how many “a lot” is, or how much power the cells on this RV would produce in a given time period of charging, but 3,000 watts (in how long? it doesn’t say) doesn’t seem like much. My first thought on seeing it was, “There’s no way that thing can run on solar alone.”
The article says the solar panels can produce 3 KWh (presumably per day?). One KWh is enough to push my EV (a 2012 Mitisubishi iMiev) about four miles. Considering that most motorhomes get about 8mpg and most cars get about 32mpg, that means you need four times as much energy to push a motorhome. Hence 3 KWh is enough to push a motorhome 1 mile. If the EV motorhome has a range of 100 miles, it will take 100 days of sitting in the sun to charge the main battery pack. Then you can drive 100 miles that day, and sit for another 100 days.
But if you use the lights or the blender or the microwave then that eats into your energy budget and charging takes even longer.
Oops. My mistake. I read that as 3,000 watt-hours but it says 3,000 watts. If you get ten hours of sun per day, then it only takes ten days of sitting still to charge the batteries.
It actually says 3kW not 3kWh. If it can generate 3kW at noon, it can probably generate at 15 kWh per day. Of course it depends weather, latitude and season. So it could probably do one 100 mile trip every 3 weeks.
They may also be assuming that the user would normally park in an RV park where it can recharge from a power hookup.
It says that the battery is a 228-Ah battery. My limited understanding of electronics suggests that, to know how long it would take to “fill” that battery with 3,000W worth of solar power, we would also need to know the voltage of the battery. Is that right? Can we make any reasonable assumptions about voltage in a battery like this?
One the one hand, i’m sure that’s right.
On the other hand, though, the article made a point of saying that this thing would work “without fuel or charging stations.” That’s what really caught my eye, and caused my doubts.
One of the news stories says it uses a modified Iveco Daily EV van: http://www.elintamotors.com/datasheets/Daily_EV.pdf
That spec sheets says 30-60 kWh of battery capacity depending on configuration. It also says 70km/30kWh, which is about 1.5 mi/kWh – not terrible, about half of a Tesla.
You’d get maybe 20 miles a day of range from the solar panels, but probably less because many of them are vertical. Even 10 miles a day might be enough to cover some shorter commutes, though, and a full charge would only take maybe 4 days of good sun. Maybe just enough to get from a charging station to a park, camp for a few days, and then make it back.
Of course, this assumes that you’re not using the power from the panels for anything but recharging the batteries for propulsion. If you’re also running lights, a TV, kitchen appliances, and so on (as most people do in an RV), then you’re probably having a hard time just keeping up with that from the panels, without any left over to charge the batteries.
The article tries to talk around it, but these solar panels are to run auxiliary power for when you’re parked. That way you don’t need a generator to run your refrigerator and lights. To run the main engine you’d need to charge it like every other EV, unless you don’t mind waiting a week to get a full charge.
The RV is based on that chassis, but he RV would also probably weigh quite a lot more that the delivery van’s 2500kg (5,500lb). The body they put on the chassis for the RV is a lot larger, and it not only has all the RV-type living stuff inside it, but a bunch of solar panels on the outside. Your range calculations would probably go down a bit for the RV, compared to the delivery van.
And as Chronos suggests, the equation changes considerably if you actually want to use any of the power-draining equipment that’s in the RV itself.
Yeah, i’m sure if you asked the RV company themselves, that’s what they would say. I think it’s just the article that is written in a rather dishonest fashion. It’s on a website called GreenMatters, and their writers might suffer from a tendency to overhype new green technology.
I was doing some more reading on solar-powered vehicles last night, and the general gist of basically every story was: If you want to drive a car powered only by its own solar cells, well, sorry, but that’s probably never going to happen.