Missed opportunity, solar tonneau and hood?

[SoCal Rob]

and if I could charge 70kwh from solar daily I'd rarely need to plug it in, its almost twice my daily commute.

I’m not sure if you mean 70kWh per day or 70km per day.

I think that 70 comes from when the presenter says 70km per day at 14:50 in the video right after he discusses that solar isn’t practical for anything except an extremely efficient EV at 14:43. Rivians are nowhere near as efficient because of worse aerodynamics, higher weight and possible driveline losses through the gearing.

I think the 70km/day speaks more to the efficiency of the vehicle than the power output of the solar cells. Hopefully someone more knowledgeable than I am will have more information.

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[lostpacket]

Beyond efficiency and cost I'd also wonder about durability for something like a tonneau cover

 

[DJG]

I could see it being a nice addition for accessories or other uses though. Like if you were able to store power and use it to power your camp kitchen or lighting and save that other battery energy for your driving.

But a robust market for this already exists via solar generators. The only value add of something attached to the vehicle is to charge while driving. That being said, I'm sure it wouldn't be too hard to set a generator in the bed, secure panels to the tonneau and run the cord through and there you go.

 

[RBR1S]

I honestly doubt the area covered would even compensate for the "daily drain" even if you were able to leave it in Arizona 16 hours on summer days. Solar is just not that efficient yet.

Now, if you want to give me an array that self unfolds out of the back and covers a 200sq meters, sure, I might take it.

 

[rohobono]

and if I could charge 70kwh from solar daily I'd rarely need to plug it in, its almost twice my daily commute.

I think you're misunderstanding what the Lighyear 0 can do. It claims it can get up to 70 kilometers of range per day from solar, not 70kWh, that's a very significant difference. Watching the out of spec review of it, they saw a max of ~800w from strong summer sun.

That's not insignificant, but even if you were able to get that output for 12 hours every day that would only equate to less than 10kWh/day(800*12/1000). And realistically speaking you'll rarely see half of that in a day. Based off of Lightyear's claim of 70km and their battery and rage specs on their website, it could get a max of 6.7kWh, but I'm sure the average you would get would be well below that. 625km(battery range) / 60kWh(battery size) is 10.426 km/kWh. 1000 / 10.426 is ~96wH/km efficiency * 70km/day is ~6700 wH/day or 6.7kWh.

Again, even getting half of that 6.7kWh/day is not insignificant but it's also not going to be very useful to most people(6.7kWh would be 10-20 miles in an R1T). The tech just ins't there yet. I think Rivian made the right choice, at least for now. The small benefit it could provide is far outweighed by the additional cost in R&D, production, and complexity.

I do hope Lightyear succeeds, it's definitely an awesome concept. We are seeing more and more advances in solar tech and I think companies like Lightyear help contribute to that.

 

[happyjohn14]

I honestly doubt the area covered would even compensate for the "daily drain" even if you were able to leave it in Arizona 16 hours on summer days. Solar is just not that efficient yet.

Now, if you want to give me an array that self unfolds out of the back and covers a 200sq meters, sure, I might take it.

Yeah, just covering the daily drain would be worth it alone. I know my phone drain has increased with the Rivian app always pinging my truck, it's about 50% faster to drain now.

 

[Smithery]

It would depend on efficiencies for it not to matter that much. What the solar conversation of the panels is, and how efficient the Rivian is with using the juice that it has. Using the Lightyear as an example sounds like you rarely need to plug it in as it gets around 6kwh efficiencies and also can charge around 70kwh on a sunny day. I seem to average 3.2kwh currently driving around town.

You're mixing units on your numbers in a weird way that I don't grok.

Here's some real numbers I know:
- The "Solar Constant" is 1361 w/sqm
- The Lightyear 0 has 5 sqm of panels
- So if the Lightyear 0 was in perfect sunlight conditions and the panels were 100% efficient then they would generate 6.8kw
- The best solar panels are only generally 20% efficient. So the Lightyear 0 instead could only possibly produce 1.36kw
- That peak figure would of course only last for a small part of the day. A more typical rate would be well under 1kw

Let's assume the average hourly take for a day of sunlight in the Lightyear 0 is, in fact, 1kWh per hour for 12 hours of usable sunlight. That's, say, 12kWh

The Lightyear 0 allegedly spends 175Wh/mi.
So that full day of sunlight would theoretically give it 68.5mi of range. Maybe this makes sense!

The R1T spends ~450 Wh/mi, so that's only 26mi of range.

I don't think the R1T has 5 sqm of surface area to dedicate to panels, even hood + tonneau.

So the amount of panel would be less, meaning the daily generation would be less.

And all of the above calculations are idealistic. The real world numbers for most people in most parts of the world would be less.

So the TLDR is:
It's not worth the added weight, cost, and fragility to add less than 26mi a day of range to a "gas guzzler" truck that goes over 300 mi on a charge.

 

[happyjohn14]

You're mixing units on your numbers in a weird way that I don't grok.

Here's some real numbers I know:
- The "Solar Constant" is 1361 w/sqm
- The Lightyear 0 has 5 sqm of panels
- So if the Lightyear 0 was in perfect sunlight conditions and the panels were 100% efficient then they would generate 6.8kw
- The best solar panels are only generally 20% efficient. So the Lightyear 0 instead could only possibly produce 1.36kw
- That peak figure would of course only last for a small part of the day. A more typical rate would be well under 1kw

Let's assume the average hourly take for a day of sunlight in the Lightyear 0 is, in fact, 1kWh per hour for 12 hours of usable sunlight. That's, say, 12kWh

The Lightyear 0 allegedly spends 175Wh/mi.
So that full day of sunlight would theoretically give it 68.5mi of range. Maybe this makes sense!

The R1T spends ~450 Wh/mi, so that's only 26mi of range.

I don't think the R1T has 5 sqm of surface area to dedicate to panels, even hood + tonneau.

So the amount of panel would be less, meaning the daily generation would be less.

And all of the above calculations are idealistic. The real world numbers for most people in most parts of the world would be less.

So the TLDR is:
It's not worth the added weight, cost, and fragility to add less than 26mi a day of range to a "gas guzzler" truck that goes over 300 mi on a charge.

Thanks for that break down. It would have to be something that unfolds to make it anywhere close to working. I also thought PV was getting more efficient, closer to 25% for commercial systems? 45% for in space?

 

[Smithery]

Thanks for that break down. It would have to be something that unfolds to make it anywhere close to working. I also thought PV was getting more efficient, closer to 25% for commercial systems? 45% for in space?

The absolute upper physical limit for silicon crystal PV cells - which is what most people think of when they think "solar cell" - is 29.43%. Something like 27% has been achieved in controlled lab settings.

The absolute best commercial panels you can actually buy right now are roof panels that are a bit over 22% efficient.

Multi-junction cells are commercially available above 30% efficiency and have shown the current record 47% efficiency for any technology. But those are *extreme* specialty items in that they're heavy and cost a lot more to make.

Making a hood and tonneau cover out of those would make the R1T cost another $100k and add another many hundreds of pounds of weight.

All to still only give you 20 more miles over the current commercial offering, assuming otherwise perfect conditions.

I admire what Lightyear 0 is TRYING to do, and they actually ship a car with the specs they've outlined then it will make fantastic sense for some people in some parts of the world

But the best generalized application of solar for EVs is not embedding the car with them to offset a modest amount of energy usage each day... It's to lay down large, permanent solar installs to power a charger that can fill up the battery in a timely manner. (Rooftop solar at home, solar plazas at office buildings, etc etc)

 

[emoore]

Thanks for that break down. It would have to be something that unfolds to make it anywhere close to working. I also thought PV was getting more efficient, closer to 25% for commercial systems? 45% for in space?

I can say from experience that space is nowhere near 45%.

 

[happyjohn14]

I can say from experience that space is nowhere near 45%.

I was just reading 47% in a lab where 50-114% is possible. Think it was a popular mechanics article.

 

[emoore]

I was just reading 47% in a lab where 50-114% is possible. Think it was a popular mechanics article.

Maybe with a solar concentrator. Certainly not in space.

 

[Smithery]

I was just reading 47% in a lab where 50-114% is possible. Think it was a popular mechanics article.

114%?

I mean... Popular Mechanics is kinda a hack, but even they probably wouldn't seriously suggest a solar panel can put out more energy than it collects from the sun.

 

[cbuckley]

I can say from experience that space is nowhere near 45%.

Astronaut humble brag

 

[emoore]

Astronaut humble brag

Haha. No way I’m qualified enough to be an astronaut.

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