Solar Powered Car - Lightyear One

[BrianHG]

Their design is light as safely possible with absolute minimal air drag.  They are claiming a range of 400km on a battery charge alone in the dark, and 800km range in the sun under optimal conditions.  They appear legit.  I'm happy even if the sun extended range is only 200-300km above the 400km battery capacity.  My my short daily city ~45km commute, with strategic parking, maybe I would never need to plug it in.

[digsys]

This guy sums it up very well !!
https://jalopnik.com/the-lightyear-one-solar-car-is-amazing-but-isnt-quite-w-1835853011
The current group of "cruiser class" cars in the coming World solar challenge are about the best "real" solar mostly cars designed to date.
(https://www.worldsolarchallenge.org/event-information/2017_classes/cruiser_class

[BrianHG]

  My damn optimism got the best of me...

[digsys]

  My damn optimism got the best of me...

Don't sweat it :-) it WILL happen one day. Our team has been working on this for 10 yrs + (road legal version), plus helped out / evaluated many other team designs.
Even after 10 yrs of research / modelling, it is still a tough ask. Best we've seen / achieved is - ~200Km solar only, and ~200Km on 40Kg battery BUT -
Car weight is critical ~250Kg max. The cruiser class aims at 60-70KmHr solar only, which is regarded as absolute MIN safe speed.
You can check out all this years entries on the WSC website or FB .. The event is just around the corner :-)

[Cyberdragon]

Can we move this to dodgey tech please? Pretty sure that's the land of broken promises and shattered dreams.

[digsys]

Can we move this to dodgey tech please? Pretty sure that's the land of broken promises and shattered dreams.

Well, you're entitled to your opinion .. the "tech" is very do-able, and quite "practical", as shown by many teams. No, they won't be Teslas or BMWs at first,
but that doesn't mean it's a pointless exercise. There are plenty of people who would be quite happy with the limitations(?) (most that I find excessive).
The big change is the use of carbon fiber, which is becoming very common now in a LOT of transport areas.

[nctnico]

What is interesting is that with the solar panels on the roof the car is cool. With a combustion engine nobody wants it even though the shape & lower weight will give you a huge improvement of milage. The rear of the car looks similar to what people who are 'hypermiling' add to their cars to reduce drag.

[LapTop006]

Can we move this to dodgey tech please? Pretty sure that's the land of broken promises and shattered dreams.

Well, you're entitled to your opinion .. the "tech" is very do-able, and quite "practical", as shown by many teams. No, they won't be Teslas or BMWs at first,
but that doesn't mean it's a pointless exercise. There are plenty of people who would be quite happy with the limitations(?) (most that I find excessive).
The big change is the use of carbon fiber, which is becoming very common now in a LOT of transport areas.

If there's any reason to consider it "dodgy tech" it's far more because of how many startup car manufacturers never manage to ship any significant volume, if at all. Electric drive doesn't really change much there.

[SparkyFX]

I like that they eventually made it a plug in concept. I think there is no point in following a purist, but arbitrary definition of powering the vehicle onboard solar only. Sure, it´s where it´s roots are and what the WSC is, but everyday traffic and life works different than in this competition and therefore the focus might be more on the fact that the application is to get you from point A to point B. It is an option and the responsibility of the driver what energy is used to charge it.

[digsys]

  are they special solar panels? those you cant buy off the shelf?

They are pretty much off-the-shelf raw noncrystalline panels, but naturally use the highest grade. Currently that is 24.5% from Sunpower, which btw, was
developed in OZ (NSW). They aren't that much dearer than the cheap stuff found on house roofs though. The BIG trick is on laminating them - both to be able to
"curve" them to the car body shape (remembering that they are literally thin sheets of glass), and NOT losing too much efficiency. 0.5 - 1.0% is about the best
you can do. As of a few years ago, there were only 2 companies in the world that could do that successfully, and it used to cost us ~$100K
The other part of the laminating process is micro-groving - where millions of cross cuts (die formed) are made in the top layer, so as to trap ALL light at any angle.
A new well cut panel will either look pitch black (no light escaping) or as an intense point.
Several new companies are now developing lamination processes, but they are ~1% less efficient, and don't have micro-groving sorted. It will get better.
Some teams, as was our 2nd car, use gallium arsenide (space) panels, and these can cost well over $1 million, usually up to $2-3 million for app 5-6 squ meters.
So, yes, they are "normal" panels, with special preparation. The BIG technology push is now getting the lamination process cheaper and better.
It may be only a few %, but that is very important for the space we have, not withstanding the "capture at ALL angles" aspect.
Our team is lucky, as Sunpower is one of our sponsors :-)

[digsys]

I like that they eventually made it a plug in concept. I think there is no point in following a purist, but arbitrary definition of powering the vehicle onboard solar only ....

The whole point of the WSC was to bring together many teams of engineers (future), in a friendly quest to push development of solar power to the limits.
There have already been MANY technologies / advancements directly from the WSC event that have gone out into commercial use - including ultra high efficient,
(98.5%+) MMPTs, 98.5%+ motor controllers, Silicon tyres and many other breakthroughs. It is a way of bringing 100s of R+D people together for a common cause.
In our years of student support, we have found at least 1-2 from each group that have been outstanding, many starting successful companies.
So it is not just cars that benefit. But yes, they are also EVs and can be plugged in to charge.

[GeorgeOfTheJungle]

They are claiming a range of 400km on a battery charge alone in the dark, and 800km range in the sun under optimal conditions

There's around 6..7 m² of PVs in that car at most (1.5*1.5*3). In one hour under the sun that's 0.7 kWh. A twizy (500kg) with 6kWh runs (in theory) 100 km. But this car draws less than one tenth of that? Unbelievable. Ok, make that 0.7 kWh twice as much. Still unbelievable.

[digsys]

It's not the first team / spinoff to come up with "wild" claims like that - stretching the numbers :-)
Usually, it is the university / sponsor / fund partner etc that requires some sort of "official press release  / validation", sometimes just a crazy venture capitalist :-)
But to be fair, it is a pretty good effort, better than many others I've seen, and it gives other teams something to compare to / analyze (done already :-) )
As a famous aussie once said "tell them they're dreaming" :-)

[BrianHG]

They are claiming their panels produce 1.25kw, not 0.7kw, though if they do achieve 0.7 in fair circumstances, this isn't too horrible.  I know this isn't much more in the grand scheme, but the game here is every drop counts.  Now, if solar cell technology would ever achieve around 65% efficiency, and I lived in a really sunny climate, I may just get away with only needing to plug in my car 2 or 3 times a month.

They are claiming a range of 400km on a battery charge alone in the dark, and 800km range in the sun under optimal conditions

There's around 6..7 m² of PVs in that car at most (1.5*1.5*3). In one hour under the sun that's 0.7 kWh. A twizy (500kg) with 6kWh runs (in theory) 100 km. But this car draws less than one tenth of that? Unbelievable. Ok, make that 0.7 kWh twice as much. Still unbelievable.

[Zero999]

I like that they eventually made it a plug in concept. I think there is no point in following a purist, but arbitrary definition of powering the vehicle onboard solar only ....

The whole point of the WSC was to bring together many teams of engineers (future), in a friendly quest to push development of solar power to the limits.
There have already been MANY technologies / advancements directly from the WSC event that have gone out into commercial use - including ultra high efficient,
(98.5%+) MMPTs, 98.5%+ motor controllers, Silicon tyres and many other breakthroughs. It is a way of bringing 100s of R+D people together for a common cause.
In our years of student support, we have found at least 1-2 from each group that have been outstanding, many starting successful companies.
So it is not just cars that benefit. But yes, they are also EVs and can be plugged in to charge.

Please avoid putting new lines everywhere. It makes your posts harder to read on a small screen. Allow the forum to word wrap.

I can see your points about meeting challenge being good for engineering, but it doesn't change the fact that a car roof isn't the best place for a solar panel. It's much better to move the solar panels elsewhere and use them to charge batteries which power cars. The only benefit of having a solar panel on a car is needing to charge less often, but it's still comparatively expensive and less practical.

[tszaboo]

They are claiming a range of 400km on a battery charge alone in the dark, and 800km range in the sun under optimal conditions

There's around 6..7 m² of PVs in that car at most (1.5*1.5*3). In one hour under the sun that's 0.7 kWh. A twizy (500kg) with 6kWh runs (in theory) 100 km. But this car draws less than one tenth of that? Unbelievable. Ok, make that 0.7 kWh twice as much. Still unbelievable.

You have to park in the center of this:

Seriously, I dont like these kind of publicity stunts, cause 99% of people will not understand the logistics of it.

And I'm saying it, even though my car has a solar panel on top of it. You know what it is good for? Running the air conditioning...

[digsys]

Please avoid putting new lines everywhere. It makes your posts harder to read on a small screen. Allow the forum to word wrap

oops, thanks for pointing that out. didn't realize ... just a habit
As for all the comments on "it will never work" - I'll agree to disagree (otherwise I'd have to tell 1,000s students / unis etc etc, that have worked on this for the last 35 yrs to drop it :-) )

[Zero999]

As for all the comments on "it will never work" - I'll agree to disagree (otherwise I'd have to tell 1,000s students / unis etc etc, that have worked on this for the last 35 yrs to drop it :-) )

I'm sure there have been plenty of new discoveries/inventions, from perusing dead ends. Just because it's not practical, it doesn't mean all that was a wasted effort. The time spend has been worthwhile in improving solar panels, aerodynamics, lightweight materials etc.

[digsys]

errr it was "friendly sarcasm" :-)  I had already covered all those points and more ... being "not practical" is your opinion, which is what I was disagreeing with.

[wraper]

FWIW using larger battery instead of spending money on fancy and very expensive solar panels will result in better car. Also intentionally placing car under highest sunlight is not something you want to do constantly. Not to say lighting conditions will be so unstable that practical effect is highly dubious. You'd be much better just placing regular solar panels on your house and using Tesla powerwall to store the energy.

[rrinker]

 The Jalopnik article seems pretty much bang on. Does this work? Sure it does. As good as they claim? Probably not. But what about practicality? As they say, it would be far better to simply put a roof over a parking lot, with solar panels arranged near as possible to the optimum angle for the latitude, and use them to power standard chargers. It looks cool, and in a pinch I guess you could camp out a few days in the sun and build up enough charge to get back to civilization. But what happens if you are in an accident? How many of those solar panels are going to be so much junk after that?

 Say, has anyone come up with this idea yet? Roof over a semi truck trailer with solar panels, to drive the refrigeration unit. Instead of the small diesel engine driven units currently used. Same for refrigerated rail cars.

[jmelson]

  My damn optimism got the best of me...

Don't sweat it :-) it WILL happen one day.

Well, I'm pretty dubious!  I love the concept, but the efficiency of solar photovoltaic panels is approaching the theoretical maximum.  The efficiency of the drive train is already quite good, the only problems are air resistance and rubber tires.  These are going to be pretty hard to fix.  Having a bunch of cars clamp their bumpers together and ride like a freight train on steel wheels and track will help greatly to solve that.  But, that interferes greatly with the practicality.

So, when a car needs ~10 kW to cruise on the highway, how are you going to get anywhere NEAR 10 KW from the panels that will blend into the car's body?

Jon

[GeorgeOfTheJungle]

So, when a car needs ~10 kW to cruise on the highway, how are you going to get anywhere NEAR 10 KW from the panels that will blend into the car's body?

^^^^ that!! Hear, hear!

[Zero999]

  My damn optimism got the best of me...

Don't sweat it :-) it WILL happen one day.

Well, I'm pretty dubious!  I love the concept, but the efficiency of solar photovoltaic panels is approaching the theoretical maximum. 

For a single junction cell yes, but multi-junction solar cells have the potential for much greater efficiencies. Yes, they're far too expensive at the moment to be economical, but that might change in 20 years time.

So, when a car needs ~10 kW to cruise on the highway, how are you going to get anywhere NEAR 10 KW from the panels that will blend into the car's body?

I agree, even with a massive boost in solar cell efficiency, it just isn't feasible.

errr it was "friendly sarcasm" :-)  I had already covered all those points and more ... being "not practical" is your opinion, which is what I was disagreeing with.

But you've not provided any facts or figures to back-up your opinion. You've just stated that it can be done and no one is disagreeing with that, just that a solar powered car is highly unlikely to ever be practical.

Just a few points:

• How much power does it take to move the car at 130km/h (forget 60 to 70km/h, no one will be happy with that!)? Someone said 10kW, but with good aerodynamics, I'm sure that can be reduced significantly.
• How much power can the whole car body plastered with solar cells generate? I haven't done the calculation, but I'm sure it's mush less than 10kW.
• What will the solar cells and the super lightweight car cost? Probably a lot, compared to a Tesla
• Where does the energy go if the car is parked and the battery is fully charged? It's wasted!
• How about when the car is scrapped, if the solar panels are still good, can they be reused?
• What about cleaning the solar panels?
• Are the solar panels easily damaged by minor collisions? Could a rock flicked up by a passing lorry damage them?
• How about driving in winter, especially far away from the equator, where there's very little sunlight?
• Towns have buildings and the suburbs have lots of trees where people drive and park their cars, so it's unlikely it will be in an optimal position to charge.

Now think of a conventional electric car, charged by solar panels, connected to the grid.

• The solar cells remain in a sunny place. They can be a long way from the user and generate energy which can be used, for other things than cars.
• Moving the solar cells away from the car allows them to cover a much larger area. They can be in the desert or even at sea.
  
• The car's body work can easily be damaged and repaired, without the expense of having to deal with solar cells.
• The car doesn't need to be that lightweight. It can be relatively cheap.
• The solar cells don't need to be scrapped with the car.

The only advantage of having solar panels on a car is it can drive a long way from any connection to the grid. The only application for them is driving across the desert.

I think you've spent too much time and money in researching this, you can't think about it objectively.

Solar cars seem to be in a similar category to solar roadways. Perhaps Dave should do a video on them?

[2N3055]

On average
Tesla Model S 60D will use 20,13 kWh/100 km.
2017 Ford Focus Electric will use 19,57 kWh/100km
Hyundai IONIQ Electric will use 15,4 kWh/100 km
Nissan Leaf (30 kWh battery) will use 18,7 kWh/100 km
That is some standard cycle that gets used for that kind of testing.

This car is really light, so maybe 10-15 kWh/100 km at same standards.
Power used would be highly dependent on aerodynamics...
So with 1,0-1,5 kWh you get 10 km range at slow speeds.

To get power needed , you need to calculate air and roll resistance.
Cd is claimed to be 0,2 and weight 500 kg. Let's say 600 kg with a passenger. Let's assume Friction coefficient of 0,015 (got that from other car, ballpark should OK)
Quick and dirty calc gets:

50 km/h - 2 kW
80 km/h - 5 kW
100 km/h - 8,2 kW
130 km/h - 16 kW

That is on flat surface. Going up hill will need more force to go up..
That is also pure power on wheels, translated to surface. With losses, we get that guesstimate of 10-15 kWh/100 km seem correct.
Of course, all without acceleration, steady state.

[james_s]

I think the best use of onboard photovoltaic panels on a car is to power the AC so the car is not scorching hot when you get in it after parking in the sun on a hot day, that could go a long way toward protecting the leather and other interior bits. Otherwise why haul the solar panels around with you? Install them on the roof of your house or carport and plug the car in at home. Even if we achieved massive gains in solar panel efficiency I don't think enough panels will ever fit on a car to adequately charge it. At least not in any car that is sturdy enough to be safe to drive on the road with other cars and has the creature comforts that people expect.