I suspect that the batteries in the trailer are actually for providing power *in* the trailer, e.g., lights, fans, etc. The article mentioned that when they stop for the night--presumably at campgrounds with 50 amp NEMA 14-50 outlets--the car will need the outlet. So, the solar charged batteries will be used in the trailer, not for the car.
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Solar Roof Option
- Thread starter theganjaguru
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- Model 3
EV-lutioin
Active Member
I don't think they intend to use solar as their only source of power, but they hope it will add some range on layover days while camping. My question is on a perfectly clear day sitting in the campground with the panels oriented just right, how much range could they generate per day with 800 W of solar?
Garlan Garner
Banned
Maybe a mile....with that trailer connected. And I'm being generous.
Why not just do the math? Numbers and explicit assumptions are a lot more useful than speculation.
1) 800W of power charging for 8 hours is 6,400 Wh of energy
That would go into the trailer battery then later into an inverter and into the Model X. Let's assume the conversion efficiency from the panel output to the X's battery is 50%.
2) So that's 6,400 x 0.5 = 3,200 Wh of energy into the Model X
How much energy does the car and trailer combo use to go 1 mile? How about double the Model X alone: 350 x 2 = 700 Wh/mi.
3) 3,200 Wh of energy being used at 700 Wh/mi is 3,200 / 700 = 4.6 miles
Garlan Garner
Banned
Why not just do the math? Tired of thinking...lol
wow a whopping 4.6 miles. My assumptions were amazingly close - especially since your calculations are assuming constant and perfect sunlight angles and with panels that produce exactly what they are rated for.....which hasn't ever happened for my 250W panels on my roof. SolarEdge
Soooo... We are close to my assumption of 1 or 1.5 miles.
Yep my initial thought of their trip taking 10 years....is about right.
JRP3
Hyperactive Member
Engineering and installation would likely be no more complex, probably less, than a pano roof, since there are no moving parts or seals.
Since it is DC to DC, wouldn't the efficiency be in the 92% range?
Using 4 miles to account for cloudy days etc, that would be about 1,400 miles a year. Close to 10% of average miles per year. Assuming the DC to DC efficiency is in 90% range, pushing 3,000 miles a year. I think the real use of the power would be, as it is in the Prius, to cool/heat the vehicle 10 minutes before one is going to use it. Original Prius solar panel kept the temp in the car to ambient which was nice and helped the AC system and helped keep the heat deterioration of interior down. In Tesla's case, running a battery heater on those bitterly cold, sunny days at Jackson Hole and warming the car up in the AM and PM.
Not sure why Tesla never liked the solar roof idea. It was kind of fun and surprisingly practical on the Prius.
No place in Canada gets 8 sun-hours per day. The highest is 3 sun-hours per day, most places much less.
No, because there is a solar panel voltage converter to charge the trailier batteries, battery losses, another conversion (probably DC-AC-DC) from the trailer batteries to the Tesla batteries.
The loss for cloudy days is more like 50% than 13%. Nor presumably would one be using the trailer charger every day.
So, 800W at 3 sun-hours = 2.4 kWh * (0.85 * 0.85) = 1.7 kWh
My estimate for hauling the trailer would be 500 Wh/mile (and 300 without). So if one is driving more than 9 miles, it would be better to leave the trailer at home. Or expect the solar to reduce the loss of range from adding the trailer, by 9 miles.
[It should be noted for Summer driving, insolation estimates are low]
Thank you kindly.
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I'm not in Canada. Most people aren't in Canada. Look on the bright side though, with global warming, Canada will get warmer and get more solar radiation. However, as you see from the Canada/IUS solar power map, much of Canada has decent solar power potential.
l live in Pacific NW which has a "low" solar potential area in both US and Canada, yet I have a very efficient 100% solar power install on my home and the Prius solar power panel worked great to ventilate the car on hot days. Even cloudy days provide a lot of solar power.
Interesting as most DC-DC converters are 93% efficient. Solar panels being DC and Tesla batteries being DC one would expect that kind of efficiency. Same as Prius is getting on its solar panel running a small DC fan and the vent motors but maybe there is something unique on the Tesla.
Again, look at the map for what the average per year is vs. what one hour might be. Lot of variables even on cloudy days. You'd go by the average per the map to see what you could expect.
Plus the black roof was a cool looking option.
Solar roof on the car worked great in practice and it would be in the Tesla DNA to offer the all black PV roof on Teslas.
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Garlan Garner
Banned
Topher said: ↑
No place in Canada gets 8 sun-hours per day. The highest is 3 sun-hours per day, most places much less.
Click to expand...
Really? There has to be a place that gets much more than 3 hours. I'm in Chicago Illinois and we are getting 10 hours of billable sunlight. Canada is not that much further away.
No place in Canada gets 8 sun-hours per day. The highest is 3 sun-hours per day, most places much less.
Click to expand...
Really? There has to be a place that gets much more than 3 hours. I'm in Chicago Illinois and we are getting 10 hours of billable sunlight. Canada is not that much further away.
The TRAILER is.
Neat trick. How does global warming affect axial tilt? Global warming has nothing to do with how much energy from the sun directly hits a surface. Any effect is likely to be in a reduction in insolation, and small.
Where do you think I got the 3 sun-hours figure from.
I'm proud of you. None of that makes it any easier to push a a two ton car though air at 60 mph.
I am discussing the idea of a trailer with its own batteries, if you aren't you might want to address some other post.
There is a large difference between running a small DC motor directly off a solar panel, and charging 400V batteries off that same solar panel. Yes the efficiencies are going to be different. More so when charging batteries, and then using those batteries to charge other batteries.
To power a small fan. Sure. To push a car, not so much.
Thank you kindly.
EV-lutioin
Active Member
Um, Canada gets way more sun than the U.S. in the summer months.... has something to do with the tilt of the Earth I am told
Alberta gets 16 hours of sunlight per day in June.
Garlan Garner
Banned
That's what I thought.Um, Canada gets way more sun than the U.S. in the summer months.... has something to do with the tilt of the Earth I am told
Alberta gets 16 hours of sunlight per day in June.
I'm proud of you. But the topic is solar panels on a Tesla. You might want to address some other thread if want to talk about your trailer in some other context.
As we saw lots of good solar spots in Canada even the least solar potential, Pacific NW, for Canada is the same as my location in the US Pacific NW so the solar roof option using the calcs provided would be good for 1,500 to 3,000 miles of power.
With much of the North American population in much higher solar potential, a good chance of a Tesla solar roof producing in the 3,000 mile plus range for the vast majority of people.
Again the best use would be in providing heating, cooling, ambient ventilation so that does not impact the miles.
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The way I read it, the batteries can be used for the X, but that's not the primary purpose. Mostly it's for the trailer itself.
Full article at:
Saanich couple takes off on electric adventure across Canada
Their blog post on the batteries:
Battery Power for Electric Car & Camping Trailer Charging Set-up
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For Solar PV, the energy production is not calculated with the number of hours of visible sunlight, but with the "Average Solar Radiation" or "Peak Sun Hours".Um, Canada gets way more sun than the U.S. in the summer months.... has something to do with the tilt of the Earth I am told
Alberta gets 16 hours of sunlight per day in June.
There is a good explanation here: Average Solar Radiation | PVEducation, as well as several sample seasonal values for some cities around the world.
I think the average in Alberta is about 5.5 hours a day.
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Um, Canada gets way more sun than the U.S. in the summer months.... has something to do with the tilt of the Earth I am told
Alberta gets 16 hours of sunlight per day in June.
Sun-hour: A commonly used term is “peak sun hours,” which reflects the energy received during total daylight hours as defined by the equivalent number of hours it would take to reach that total energy value had solar irradiance averaged 1000 W/m2.
Sorry for the jargon.
Thank you kindly.
Looking at the solar map of North America above, teasing out Southern Alberta which has a much higher solar rating than Northern Alberta and much higher population it looks like it might be close to 7 hours a day vs. the 5.5 average for the whole province.
The solar panel on the Tesla roof is not going to produce much but, like the Prius and now the Prius plug in, it would be useful for heating/cooling for short periods prior to use and ventilation during the day. With Tesla taking in Solar City and, I'd guess, Tesla owners more into solar panel than the general population, solar roof on the Tesla would be fun and practical.
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