I got it wrong the first time, then got it at the second take, thought I had it wrong again reading your comment and turned around again. The writing was weirdly misleading.
> Solar panels, even at high noon, usually only produce about 200 watt-hours per square meter.
> The most efficient production electric vehicles today (probably the Hyundai Ioniq and the Tesla Mod 3) would only be able to travel 2–4 miles on that amount of electricity…in an hour. Most people could walk faster.
From what I get:
- in the best conditions the panels could produce 200W in an hour
- 200W would allow for 2-4miles on the most efficient cars
The author's point seems to be that if the solar panel was the only source of energy the car would be slower that walking. It's different from seeing it as an additional source of electricity, just like regenerative braking is for instance.
> - 200W would allow for 2-4miles on the most efficient cars
Sorry, but that's wrong. They meant 2-4 miles per 1 kWh, not per 200 Wh.
Very good EVs get about 4-4.5 miles / kWh at optimal speed (usually between 25 and 35 mi/hr). So, best case, 200 Wh is good for about 1 mile, assuming you can deliver the 200 Wh over a period of 2 minutes.
However, 200 W can't push the car at 1 mi/hr because of "vampire" losses: Power for accessories and vehicle systems (like power-assisted steering, power-assisted friction brakes, the ABS controller, the airbag monitor, etc). 200 W of power isn't just slower than walking: In a normal-sized car, you will literally go 0 mi/hr.
More importantly, 200 W/m^2 is the best-case scenario at noon, in the tropics, on a cloudless day, with no shadows, using expensive, high-efficiency panels aimed squarely at the sun. As soon as any of those qualifiers is not met, power drops precipitously.
In particular, the atmosphere absorbs a large amount of light: In space, solar insolation is about 1300 W/m^2. At earth's surface in the tropics, solar insolation is about 1000 W/m^2 at noon. At higher latitudes, or other times of the day, solar insolation is lower.
A good rule of thumb is that (for Europe and North America) the total insolation over a full day is about 5000 Wh/m^2. So, a solar panel on a sun-following mount is limited to about 1000 Wh/m^2/day, again assuming no clouds. For a fixed solar panel, such as on the hood of a car, you'll get about half of that: 500 Wh/m^2/day. Remember, you need 1000 Wh to go 4-5 miles.
That "4-5" implies a lot of accuracy, but I would have thought that the distance you can travel on 1000 Wh would vary by orders of magnitude depending on the speed, terrain and road surface.
However, if you are moving a 1 tonne vehicle up a 5% gradient then you won't do more than 4.5 miles on 1000 Wh, if I've calculated that correctly.
> Solar panels, even at high noon, usually only produce about 200 watt-hours per square meter.
> The most efficient production electric vehicles today (probably the Hyundai Ioniq and the Tesla Mod 3) would only be able to travel 2–4 miles on that amount of electricity…in an hour. Most people could walk faster.
From what I get:
- in the best conditions the panels could produce 200W in an hour
- 200W would allow for 2-4miles on the most efficient cars
The author's point seems to be that if the solar panel was the only source of energy the car would be slower that walking. It's different from seeing it as an additional source of electricity, just like regenerative braking is for instance.