How Long Till Solar Powered Car?

[vinnie97]

Several prototype solar cars have been built already. Of course, their practicality is another matter entirely.

 

[tander]

I think several of us are possibly being a bit absolutist in thinking. Certainly the highest currently available commercial efficiencies in solar panels are around the Sharp triple-junction at 37.9%. The latest developments seem to show Perovskite layers could add as much as 50% to efficiency, assuming the durability and other issues can be resolves, so might end out with commercial efficiency of more than 50%. Assume that happens, still a car will not have enough space for that to be useful in most populated latitudes. ... So, yes, there will be some solar panels on transport vehicles of some sort within the next decade.

Now, I will record my predictions and will happily make book that these things will happen one way or another.

+1 Well said, much more articulate me. What some of us are forgetting is that these technologies are basically where smartphones were in 2008 or older, not much refinement or investment relative to incumbent technology. As they are refined and investment increases by leaps and bounds, the small advancements will add up and combine to make a lot of things start to seem common sense that not too many years before seemed pretty fantastical and wacky, like a phone with no buttons that's also a computer, a gps, real time traffic, a camera, and a fitness monitor etc.

 

[wdolson]

There may be some gimmicks for solar panels built into cars at some point, but I doubt they will even become a mainstream product. To include solar panels on a car, you will be adding some weight and complex electronic high up on the car (adding top weight, which isn't a big problem with Tesla because the batteries are so low, but could be a problem with other BEVs and hybrids). Circuitry to charge up the batteries from the panels would have to be added in addition to the regular battery charging electronics. You wouldn't need an inverter for a car because you don't need to convert it to AC between the panel and the battery, but solar cells are a different kind of energy source than other charger technologies. Solar cells are essentially constant current sources rather than constant voltage sources like most other charging techniques.

The added cost is probably not worth the benefit. In most cases it is probably more cost efficient to provide more ways to plug in and use power off the grid. If the cost reductions in solar continue, a lot of companies will start putting solar panels on their buildings to reduce their electricity costs and providing plugs for customers and employees would be fairly cheap at that point.

There are technologies being investigated that will enable using more of the sun's energy to convert it to electricity, but those haven't left the lab yet. Even if we do boost panels to 1 Kw/m^2, it will be a drop in the bucket compared to what can be done with stationary solar stations.

Now one thing I have thought would be a good piece of survival gear kit if your driving your electric vehicle out where you aren't sure chargers are going to be available would be a portable charging panel you could set up in the wilderness on the ground next to your car and give it a boost to get back to civilization if you get stranded. It may take a day out there to get enough juice to get back to a charger, but it beats getting stranded in the middle of nowhere with no options, especially if you can't get a cell signal. If you can get a cell signal, someone may be able to pick you up, but the car still needs to get enough of a charge to get back.

The market for these would be relatively small, but it would allow BEVs to go further from civilization with at least emergency back up. This would probably be required survival equipment once BEV pick ups become available. Most pick up drivers don't get that far from civilization, but ranchers do as well as some other company vehicles.

 

[Johan]

Voted.

Comments (sorry if I come off harsh):

1. Obviously the answer is never, due to the laws of physics.

2. Obviusly number 2: the answer is "now" as in there are solar powered cars and lot's of them. Only the panels are on a roof where they can be used most effectively and the electricity is stored in this device on-board the vehicle known as a "battery" (go figure).

 

[Bangor Bob]

Work into developing "normal-ish" cars that can get a significant portion of their motive power from on-board solar is a real thing, if somewhat confined to academia at the moment. Remember that there are two sides to the equation: Maximizing solar capture is just one piece, reducing the energy requirements of the vehicle is the other, and there is a LOT of potential there that is not being applied to production vehicles.

I'll just leave this here:

Cruiser Class | World Solar Challenge 2015

In the 2013 event a car in this class covered 3000km on just 64kWh of external (charger-supplied) energy. 21Wh/km, 34Wh/mi came from the chargers, and the balance of needed energy came from the panels.

 

[tander]

Voted.

Comments (sorry if I come off harsh):

1. Obviously the answer is never, due to the laws of physics.

2. Obviusly number 2: the answer is "now" as in there are solar powered cars and lot's of them. Only the panels are on a roof where they can be used most effectively and the electricity is stored in this device on-board the vehicle known as a "battery" (go figure).

Okay so I agree that right now putting solar panels on rooftops and backyards etc. makes an awful lot of sense, and likely will make the most sense for quite a while, it's a practical solution using current technology. However that said I'm surprised at how many "nevers" there are, that does seem kind of harsh for the general forward thinking types that seem to frequent TMC. Just imagine asking people tens years ago if smartphones that could do all the things that an Iphone 6 does today would be possible for every (okay not every) part time baristsa to own? I'm guessing a lot of people would say that it would never happen either because they didn't think it was possible to combine all this stuff into such a small package or because they thought it would end up costing 100k a piece and therefore be totally impractical. Who could have imagined that the prices and quality on all the individual components could have improved so much so fast that non-CEO types would want one...not Research In Motion (Blackberry). But an incredible increase in demand, energy, and investment made it happen. It might "never" make sense in Norway because the physics don't seem to work and there just isn't that much sun hitting the earth, but in Texas or North Africa?

 

[Johan]

Even with theoretical 100% efficient panels at perfect angels toward the sun all the time there just isn't enough solar energy hitting the surface area of a normal sized car.

Enthusiasm doesn't beat the laws of thermodynamics, sorry to be a Debbie downer.

 

[Saghost]

It might "never" make sense in Norway because the physics don't seem to work and there just isn't that much sun hitting the earth, but in Texas or North Africa?

In Texas and North Africa - there still isn't enough sun hitting the earth.

How fast do you like to drive?

Do you think future cars will be lighter or heavier than current cars?

Is there room for them to get much more aerodynamic without impacting crash safety and packaging?

The only way a car powered directly by solar energy is possible is if cars get a *lot* more efficient - and since current EVs are already over 80% efficient in delivering the power they use, it has to come from the load side - they have to become lighter and more aerodynamic - by an order of magnitude or so for freeway speeds.

Here's a chart for battery range for the Nissan Leaf developed experimentally by the folks on the MNL forums. I like it because in addition to actual range numbers, they provided miles per kWh - and real time usage in kW:

Range Chart - My Nissan Leaf Forum

You'll note that even at a measly 35 mph, the Leaf is already using 5.56 kW of power just to sustain the pace on flat ground with no wind. When you consider that the typical car has maybe four or five square meters of horizontal surface area and that theoretical 100% perfect energy conversion would still only produce 1 kW per square meter of panel area at high noon on the equator, you begin to understand the scope of the problem.

Is it theoretically possible to build a vehicle that can move at freeway speeds on just sunlight? Absolutely - SunRaycer proved it - with 1980s technology it could do 68 mph under ideal conditions - in a single person teardrop that weighed less than 600 pounds with one powered wheel and no chance in any collision. But they averaged less than 45 mph for the race, and it is in no way a practical vehicle for anyone.

Sunraycer - Wikipedia, the free encyclopedia

 

[Neo]

I voted never too.

Solar panels are about 20-25% efficient. Even if that increases to 100%, it wouldn't be enough to make a regular car because cars are heavy and they need wide tires and all that creates lots of rolling resistance. You could make a single seater lightweight vehicle that rides on bicycle wheels but not a regular car.

 

[jerry33]

Even with theoretical 100% efficient panels at perfect angels toward the sun all the time there just isn't enough solar energy hitting the surface area of a normal sized car.

Enthusiasm doesn't beat the laws of thermodynamics, sorry to be a Debbie downer.

Correct. The average energy reaching the ground worldwide is about** 340 W/m[SUP]2[/SUP]. At the equator it can be 1000 W/m[SUP]2[/SUP]. This is on a clear day at noon. Austin, TX gets a total of 4800 W/m[SUP]2[/SUP] per day on average which can be used to generate electricity (for those that don't know, Austin is close to the geographical centre of Texas). That works out to a Tesla driving distance of about 31 km (19 miles) per m[SUP]2[/SUP] of car solar panel surface (and assumes a 100% efficient, perfectly oriented, solar panel that doesn't increase the current weight of the car).

** These are the best numbers I could come up with in a short time. If anyone has any better numbers, go for it.

 

[wk057]

I've managed several thousand 100% solar powered miles in my Model S so far with my off-grid solar setup (see signature). While I think it's completely crazy to try and put solar panels on a car and expect to do anything useful with them, putting solar on a house and charging from that power makes perfect sense.

On a side note, I chuckle a little when I see people with grid tied system saying they power their cars from solar. Good effort, but probably not actually true.

 

[jerry33]

On a side note, I chuckle a little when I see people with grid tied system saying they power their cars from solar. Good effort, but probably not actually true.

If you purchase a wind or solar plan from your electric company, you force them to purchase that much wind and/or solar power. In many cases, unless you force them to by choosing that plan, they won't purchase any. So although the actual electrons powering your car may not be from solar or wind sources, the amount of energy you use has been put into the grid from those sources (and that much less fossil fuel energy has been used).

 

[Johan]

If you purchase a wind or solar plan from your electric company, you force them to purchase that much wind and/or solar power. In many cases, unless you force them to by choosing that plan, they won't purchase any. So although the actual electrons powering your car may not be from solar or wind sources, the amount of energy you use has been put into the grid from those sources (and that much less fossil fuel energy has been used).

If you want to get really semantic about it I suppose you could say that the electrons your battery came with from the factory stay in it for its entire life; when you charge whether it be directly from solar panels or the grid all that happens is energy is added and the electrons get pushed to orbits with higher potential energy (assuming classic physics). As you discharge this process reverses.

Or you could choose to see it as a directional flow of electrons. Since one is indistinguishable from another we wouldn't know the different.

Hence this also applies on a macro scale: if you're offsetting any other type of electricity production using solar panels, somewhere, you might as well say your car is solar powered. At least IMHO.

 

[tga]

Is it theoretically possible to build a vehicle that can move at freeway speeds on just sunlight? Absolutely - SunRaycer proved it - with 1980s technology it could do 68 mph under ideal conditions - in a single person teardrop that weighed less than 600 pounds with one powered wheel and no chance in any collision. But they averaged less than 45 mph for the race, and it is in no way a practical vehicle for anyone.

I was in college during the American Tour de Sol days (late 80's), and had friends who worked on Dartmouth's entry (the various SunVox cars). None of the entries were anything you'd consider "practical". I tried to find pictures, but no luck. Dartmouth has a bunch of stuff cataloged, but it's all 35mm film/prints - nothing on line.

 

[tander]

Correct. The average energy reaching the ground worldwide is about** 340 W/m[SUP]2[/SUP]. At the equator it can be 1000 W/m[SUP]2[/SUP]. This is on a clear day at noon. Austin, TX gets a total of 4800 W/m[SUP]2[/SUP] per day on average which can be used to generate electricity (for those that don't know, Austin is close to the geographical centre of Texas). That works out to a Tesla driving distance of about 31 km (19 miles) per m[SUP]2[/SUP] of car solar panel surface (and assumes a 100% efficient, perfectly oriented, solar panel that doesn't increase the current weight of the car).

** These are the best numbers I could come up with in a short time. If anyone has any better numbers, go for it.

Okay let's use your numbers for a minute here and look at a scenario. Let's figure we're in Austin in 2025 and we get 4800 w/m^2 sun per day on average. We've got a 2025 model s with the same dimensions as today 16x6ft, roughly 10m^2 horizontal surface area. If you average 4.8kwh/m^2 and you've got 10m^2 at 50% efficiency, that gets you 24kwh a day right? That's not enough to drive continuously, but it's more than enough to cover the average commute considering that in 2015 the model s is averaging like 3mi per kwh. And when you start factoring in using side panels and windows (photo voltaic "paint" and glass might be fairly mature by 2025) and higher efficiency absorption, and improvements in the efficiency of the car (energy density, self-driving, regen etc.) it starts to look like people wouldn't need to charge at night in Austin unless they drive a lot. Even in Oslo where you're getting like a half the sun of Austin it could add up to enough for the average daily commute. So am I missing something, in spite of the poll results, with 4800w/m^2 in Austin or 2400/m^2 in Oslo, the laws of physics seem to pretty complimentary to the idea when you pair it with the exponential growth of investment in renewable tech, but maybe I'm too idealistic or got the numbers wrong? Maybe cars will have 1000kwh batteries and they'll be charging by drone fly overs by then and this idea will be redundant, but I don't understand how the physics are so impossible. I guess one big assumption I'm making is that electric cars and rooftop solar are pretty ubiquitous by then and the "laws" of economics (expensive and unrefined batteries/solar panels) will have improved a lot. Solar irradiance - Wikipedia, the free encyclopedia

 

[jaguar36]

Okay let's use your numbers for a minute here and look at a scenario. Let's figure we're in Austin in 2025 and we get 4800 w/m^2 sun per day on average. We've got a 2025 model s with the same dimensions as today 16x6ft, roughly 10m^2 horizontal surface area. If you average 4.8kwh/m^2 and you've got 10m^2 at 50% efficiency, that gets you 24kwh a day right?

Well first off you're not getting 10m^2 of solar cells on a Tesla. Maybe you'd get half that. More likely 1/4. Also keep in mind that you're not going to make the Model S a huge amount more efficient. It's not like a an iPhone in 2008, the aerodynamic shape of a car has been studied for far far longer than smartphones have even existed. And aero is where most of the power goes. The motor is already extremely efficient, you're not going to get much more there either. The batteries will probably get somewhat lighter, as will the frame and body panels. Of course this will all be offset by all the weight of the solar cells (and the addition of more safety gear which has and will continue to happen to all cars) so you're probably not going to save any weight either.

Regardless it will never make sense to do. You're always going to be better off putting the cells on a rooftop where you don't have to deal with the vibrations, aesthetics, or safety of putting them on a car and then just charging the car off them. If you could eliminate the batteries, sure, different story, but then you can't drive at night, or in the rain.

 

[MorrisonHiker]

I was just reading about the Immortus solar powered concept car this morning. Supposedly it would be able to do 35 mph on solar. With a projected price of $370,000, I think solar panels at home or in a community solar garden would be much more affordable.

 

[nwdiver]

IMO there a general misunderstanding of solar energy with some of the public.... here's proof... :tongue:

 

[JRP3]

Fully powered by on board solar, probably never, unless vehicles become much smaller and lighter, which is possible, but not likely. However, as I've mentioned in other threads on the subject, I do expect on board solar could provide a significant portion of real world average daily driving needs, which is less than 40 miles a day. During the day most vehicles are not parked at home and not parked in garages, but sitting outside parked for 8 hours. That takes care of the vampire drain and more. If the panels get cheap enough I'd want them on the hood and roof.

 

[wk057]

When my system is complete, if all of my power were used for driving it would produce enough power solely from my own solar panels to drive nearly 1000 miles per day in the summer time (or in my case two Model S driving up to 500 miles/day). Again, if all of my power were used for driving which isn't nearly the case. I think that's pretty good and definitely proof that it's possible to drive any daily real world distance on purely solar with the right setup.

On-board solar is just never going to happen.