Solar PV on electric cars

[hendorog]

Here is a puzzle for the electric fan girls and boys to grind their teeth on.

Is putting solar panels on an EV a good idea?
Why?

Now let the games begin. 

- For the record, I think it is a great idea.

[NiHaoMike]

I recall the general consensus is that the area is too little to generate much power. The main exception being a RV, where the solar is very useful when the RV is parked.

[digsys]

This has been beaten to death on these forums and doesn't need re-starting. IF you are interested, there are a few of us here in Solar EV clubs - If you really want to know more, check out - https://www.worldsolarchallenge.org/  or https://www.facebook.com/WorldSolarChallenge/  (If you are on FB)  or https://www.facebook.com/ISFsolarcar/
(That's our last / current car :-) ) Up to 45 teams have been designing / running solar cars for over 35 yrs, and the last several years, there is a new category - Road legal capable.
In fact, the "race" is coming up in OCT 13 this year - Darwin to Adelaide. No need to start a crap shoot - ymmv

[tautech]

Just measured my 4 door sedan and there's at least 1.2 m² roof area available for panels if it was an EV.
Is that an insignificant area ? 

[hendorog]

I recall the general consensus is that the area is too little to generate much power. The main exception being a RV, where the solar is very useful when the RV is parked.

Interesting.

So solar panels don't generate much power when they are on a vehicle?

Perhaps the electrons get car sick?

[fourfathom]

I recall the general consensus is that the area is too little to generate much power. The main exception being a RV, where the solar is very useful when the RV is parked.

Interesting.

So solar panels don't generate much power when they are on a vehicle?

Perhaps the electrons get car sick?

the 1.5 square meters of available area for solar panels that Tautech mentions will receive about 1500W of sunlight at noon.  Good panels are about 20% efficient, giving about 300W peak power.  Over a day this will add up to about 1.5kWh, or perhaps a bit (or a lot) less depending on latitude and season.  Batteries, controllers and motors do have some loss, but the total efficiency might be around 80% or 1.2kWh.

1kW equals 1.3HP.  You do the math, but that's not going to get you very far in a typical electric car.

[bdunham7]

Here is a puzzle for the electric fan girls and boys to grind their teeth on.

Is putting solar panels on an EV a good idea?
Why?

Now let the games begin. 

- For the record, I think it is a great idea.

Hmmmm.  Can trolls do math? 

[hendorog]

I recall the general consensus is that the area is too little to generate much power. The main exception being a RV, where the solar is very useful when the RV is parked.

Interesting.

So solar panels don't generate much power when they are on a vehicle?

Perhaps the electrons get car sick?

the 1.5 square meters of available area for solar panels that Tautech mentions will receive about 1500W of sunlight at noon.  Good panels are about 20% efficient, giving about 300W peak power.  Over a day this will add up to about 1.5kWh, or perhaps a bit (or a lot) less depending on latitude and season.  Batteries, controllers and motors do have some loss, but the total efficiency might be around 80% or 1.2kWh.

1kW equals 1.3HP.  You do the math, but that's not going to get you very far in a typical electric car.

Correct. But that was the easy and obvious answer that everyone thinks of.

The answer I'm thinking of requires a little bit of out of the box thinking.

Edit: And, to be fair, a bit of thinking about the future.

[tautech]

Hmmmm.  Can trolls do math? 

The OP ?
Probably not but I'm not much good at it either.

However 1.2 KW into the battery daily for exactly what cost over the life of the vehicle sounds good to me.
And I haven't had to purchase it.

How much can a custom PV panel and a charge pump really cost ? 

[digsys]

Trying to stay out of this :-) just adding some REAL numbers ..
Our 10 yr old 24% "off the shelf" sunpower panels, on 6 sq mtrs of area generate 1.2KWhr
Split up into 6 sections, we got solar > battery efficiency of 98.5% (MPPTs were designed in-house and now used / sold all over the world). That efficiency is even in dawn / dusk due to a micro-groving layer on the panels.
Our wheel motor is 98+% efficient, over a wide range. Only 20KW max, but it is the first design, all back 10+ yrs ago. Also sold all over the world.
Granted, this is a pure race car, but it can get a max 900Km range on panels alone (a good day) +~ 400Km on a 5KWhr battery pack (at 20Kg). That was 10+ yrs ago
SO, a road legal car will be a lot less, due to much extra weight and poorer aero, but it is a start. Our modelling indicates, up to 250Km max per day on panels alone.
Many teams don't get that good a figure, but they only have 2 yrs to design and build, then most graduate and leave Uni, and it mostly all starts again.
The links I posted have more detailed links to all solar EV groups currently working.

[hendorog]

I recall the general consensus is that the area is too little to generate much power. The main exception being a RV, where the solar is very useful when the RV is parked.

Interesting.

So solar panels don't generate much power when they are on a vehicle?

Perhaps the electrons get car sick?

the 1.5 square meters of available area for solar panels that Tautech mentions will receive about 1500W of sunlight at noon.  Good panels are about 20% efficient, giving about 300W peak power.  Over a day this will add up to about 1.5kWh, or perhaps a bit (or a lot) less depending on latitude and season.  Batteries, controllers and motors do have some loss, but the total efficiency might be around 80% or 1.2kWh.

1kW equals 1.3HP.  You do the math, but that's not going to get you very far in a typical electric car.

Well we can work it out.

Wikipedia says that the 2016 Nissan leaf gets 19.1 kWh/100km. So 1.2kWh would get you about 6.3 km's.

[tautech]

Hmmmm.  Can trolls do math? 

I might have been quite wrong.
Apparently so. 

Well we can work it out.

Wikipedia says that the 2016 Nissan leaf gets 19.1 kWh/100km. So 1.2kWh would get you about 6.3 km's.

So that conservitavely could be 5 km free motoring/day. 
That might be 50% of someones EV running.

[f4eru]

It's not a really good idea on an everyday car, due to the added weight and disproportionnate cost.

Let's take an example of the most meaningful example we can find where it would add minimal cost/weight/aero:
A reasonnable everyday electric car : Tesla Model 3

It has 1,4m² of shaded roof glass already, ideal to replace the shading by printed on solar panels.

Printed on solar panels are crappy, but don't add weight.
You get 14% efficiency, 3.5 kWh/day of sunlight (sunny, parked with no shade) -> 0.686 kWh of electricity/sunny day

That's 4.7km of travel....

Now you get only 20% of the full sunny days in average on a year because of many factors (weather, shade, parking, etcetc...).
In average on a year, you get 1km/day.

That's nothing. With a roof solar PV panels 20m², you get 100x more, and you can cover all of your commutes, with power to spare in the summer, for a tenth of the cost/km....

'Seriously guys, the right place for solar panels in everyday use is on the roof, nowhere else.

[tautech]

Why would it be like any conventional PV panel we already know ?
Surely this is a job for a custom curved and optimized PV panel that's part of the cars structure.

Why hasn't this already been done ? 

[wraper]

Why would it be like any conventional PV panel we already know ?
Surely this is a job for a custom curved and optimized PV panel that's part of the cars structure.

Why hasn't this already been done ? 

It has been done and it's stupid. It's similar to solar roadways. It's sort of works but no way can be justified from any practical standpoint. Simply using larger battery for the same money spent makes much better car

[tautech]

Sure, but aren't we missing the use of free energy ? Stupid ? 

[wraper]

Sure, but aren't we missing the use of free energy ?

What use of that "free energy" if it will never cover the upfront costs for producing itself.

[hammy]

Is putting solar panels on an EV a good idea?

Already done: https://sonomotors.com/de/sion/
Toyota, Kia and Hyundai use solar panels for the next generation of BEV and PHEV.
https://www.electrive.com/2019/07/04/toyota-testing-hybrid-prius-fitted-with-solar-cells/

[wraper]

FWIW unless it's nearly free to implement and maintain, it's just a gimmick.

[tautech]

Is putting solar panels on an EV a good idea?

Already done: https://sonomotors.com/de/sion/
Toyota, Kia and Hyundai use solar panels for the next generation of BEV and PHEV.
https://www.electrive.com/2019/07/04/toyota-testing-hybrid-prius-fitted-with-solar-cells/

wraper mentioned stupid, are Toyota, Kia and Hyundai stupid or just ahead of the rest of the stupid other EV manufacturers ?

[tautech]

Sure, but aren't we missing the use of free energy ?

What use of that "free energy" if it will never cover the upfront costs for producing itself.

Could we not say the same of the carbon footprint to build an EV vs a conventional ICE car ?

[wraper]

Sure, but aren't we missing the use of free energy ?

What use of that "free energy" if it will never cover the upfront costs for producing itself.

Could we not say the same of the carbon footprint to build an EV vs a conventional ICE car ?

EVs actually pay over for themselves. Both from larger initial carbon footprint standpoint and lifetime fuel cost.

[tautech]

Sure, but aren't we missing the use of free energy ?

What use of that "free energy" if it will never cover the upfront costs for producing itself.

Could we not say the same of the carbon footprint to build an EV vs a conventional ICE car ?

EVs actually pay over for themselves. Both from larger initial carbon footprint standpoint and lifetime fuel cost.

That could be questionable IMO.
There’s another elephant in the room you may have overlooked.

[wraper]

There’s another elephant in the room you may have overlooked.

Dare to name it?

[nctnico]

EVs actually pay over for themselves. Both from larger initial carbon footprint standpoint and lifetime fuel cost.

Governments earn big bucks from tax on fuel. Do you really think they will let that milk cow go away (*)? And then there is the charging infrastructure. Nowadays largely free but at some point you'll pay dearly and you'll have no alternative (unless you have your own driveway where you can charge and never venture far away). You also have to calculate the cost of the battery into the fuel costs because batteries don't have an eternal life. Add these together and you'll see an EV is way more expensive then you are lead to believe.

Maybe putting solar panels on the roof of an EV isn't such a bad idea after all cost wise and from a point of convenience. Even if it is just to keep the batteries charged while the car is parked or have enough 'juice' to drive to a super charger nearby.

*In the Netherlands there is an ongoing study by the government about taxation of EVs. EVs are now excempt from road tax but because of their high weight EVs do more damage to the roads so that will need to be paid by the owners somehow. That is one. The other is income from fuel taxes which the EV owners don't pay; it is possible EV owners are going to pay an extra tax per distance travelled to compensate for fuel taxes. In Norway there is a similar discussion. Norway and the Netherlands are the leading countries where it comes to EV adoption so what happens in these countries is going to happen in other countries too.