Car with solar panel range extender? Really??

[cavac]

Just found a (german language) article about an electric car. Not much so far, but it claims to have a solar panel that can extend the cars range by "30 kilometers per day".

https://www.heise.de/newsticker/meldung/Elektroauto-Sion-Muenchner-Startup-Sono-Motors-zeigt-Prototyp-mit-Solarmodulen-3785401.html

Of course, the whole thing is financed by pre-order from a relatively unknown company. I'm not an expert on solar anything, really. Could someone here do some rough calculations if the range extension thing is even feasable with a car-roof mounted solar panel?

[Fungus]

A Nissan Leaf has a 30 kWh battery and can drive for ~50km so that's about 6kWh to drive 30km.

It depends a lot on where you live, but: Over a single day a 1 square meter panel can generate about 5kWh in Summer, less in Winter.

A panel on the roof of a car will be horizontal, that reduces the output.

Conclusion: It's not completely batshit crazy. It's in the right order of magnitude in summer with your car parked in the sun all day. In real life you might get an extra 5-10km per day depending on the time of year, the weather, where you live, etc. More suited to Spain than Scotland.

[IanMacdonald]

A Nissan Leaf has a 30 kWh battery and can drive for ~50km so that's about 6kWh to drive 30km.
It depends a lot on where you live, but: Over a single day a 1 square meter panel can generate about 5kWh in Summer, less in Winter.

Wildly out on both counts.

If a 30kWh battery can drive 50km, then that's 0.6kWh per km. 6kWh would thus get you only 10km.

The insolation received by the Earth is about 1kW/sqm. That is the theoretical value without any allowances for atmospheric attenuation, clouds, etc. Thus even with a 100% efficient 1msq panel you would be unlikely to get more than 6kWh per day even in very sunny climes.  (12h at 50% average strength sun)

Over a day, in the UK we get about 2kWh of insolation per square metre in summer, a tenth of that in winter. Surprisingly, the Sahara only manages to double our summer value, to 4kWh. 

Solar panels are about 16% efficient, which means 160W peak output in strong sun, per square metre. Thus in the Sahara your car would receive 0.64kWh per day (16% of 4kWh) or enough to drive 1.06km or just over half a mile at Nissan Leaf consumption rates. In the UK winter it would receive 200Wh*0.16 or 32Wh. Enough to travel 54 metres or 175 feet. 

https://iwr.im/science/solarhomes  (Cost per watt of panels is a little out of date but other figures still apply)

[Nusa]

Just found a (german language) article about an electric car. Not much so far, but it claims to have a solar panel that can extend the cars range by "30 kilometers per day".

https://www.heise.de/newsticker/meldung/Elektroauto-Sion-Muenchner-Startup-Sono-Motors-zeigt-Prototyp-mit-Solarmodulen-3785401.html

Of course, the whole thing is financed by pre-order from a relatively unknown company. I'm not an expert on solar anything, really. Could someone here do some rough calculations if the range extension thing is even feasable with a car-roof mounted solar panel?

You understated the article. It's 330 solar cells covering the roof, hood, and sides of the vehicle, which probably equates to several traditional "solar panels". Plus the vehicle is a smallish electric-only vehicle. It may not be that far out of the ballpark, at least in sunny climates.

[IanMacdonald]

You understated the article. It's 330 solar cells covering the roof, hood, and sides of the vehicle, which probably equates to several traditional "solar panels". Plus the vehicle is a smallish electric-only vehicle. It may not be that far out of the ballpark, at least in sunny climates.

Doesn't really make much odds, as the figures are too far out from the ballpark. 

[Fungus]

A Nissan Leaf has a 30 kWh battery and can drive for ~50km so that's about 6kWh to drive 30km.
It depends a lot on where you live, but: Over a single day a 1 square meter panel can generate about 5kWh in Summer, less in Winter.

Wildly out on both counts.

It should say "150km". I don't know where the '1' went.

Surprisingly, the Sahara only manages to double our summer value, to 4kWh.

I saw a figure of 4.8 on the web and rounded it up to 5.

It was only a finger in the air calculation, a basic "sniff test".

Doesn't really make much odds, as the figures are too far out from the ballpark. 

No they're not. It's in the right order of magnitude. We don't know how many square meters of panel are on the car or where they did their test. It might be 2m^2 and Costa Del Sol.

[mikerj]

No they're not. It's in the right order of magnitude. We don't know how many square meters of panel are on the car or where they did their test. It might be 2m^2 and Costa Del Sol.

Even with 2m^2 panel in the Sahara there's about a fifth of the energy required to do 30km, so either they have some seriously efficient panels or close to 10^2 meters of conventional ones.

[Fungus]

No they're not. It's in the right order of magnitude. We don't know how many square meters of panel are on the car or where they did their test. It might be 2m^2 and Costa Del Sol.

Even with 2m^2 panel in the Sahara there's about a fifth of the energy required to do 30km, so either they have some seriously efficient panels or close to 10^2 meters of conventional ones.

Fine.

All I was doing was a quick sniff test to see if it was in Fontus/uBeam/Batteroo territory.

[mtdoc]

No they're not. It's in the right order of magnitude. We don't know how many square meters of panel are on the car or where they did their test. It might be 2m^2 and Costa Del Sol.

Even with 2m^2 panel in the Sahara there's about a fifth of the energy required to do 30km, so either they have some seriously efficient panels or close to 10^2 meters of conventional ones.

Not only that, without active cooling (which is not free) those panels will be too hot to produce even that much.

[mikerj]

Fine.

All I was doing was a quick sniff test to see if it was in Fontus/uBeam/Batteroo territory.

Clearly it will work in the sense that it will provide some extra range, and it's not hopelessly impractical so it's already head and shoulders above those jokers.  I just suspect that the range claims have been inflated.

[Nusa]

More info in English, with a few of the more relevent tidbits pulled out:

https://www.sonomotors.com/sion.html

"the Sion can cover up to 30 kilometer per day - for free."

"A total of 330 SunPower cells are producing 1,208 W peak at an efficiency of 24 %.
This amount could provide power for up to 40 km in one day. However, this is a theoretical maximum value which is highly unlikely to be achieved under real-life circumstances."

"For the solar panels we use monocrystalline silicon cells."

https://www.indiegogo.com/projects/sion-a-solarcar-for-everyone-car-solar#/

7.5m^2 of panels

[Fungus]

"A total of 330 SunPower cells are producing 1,208 W peak at an efficiency of 24 %.
This amount could provide power for up to 40 km in one day. However, this is a theoretical maximum value which is highly unlikely to be achieved under real-life circumstances."

"For the solar panels we use monocrystalline silicon cells."

https://www.indiegogo.com/projects/sion-a-solarcar-for-everyone-car-solar#/

7.5m^2 of panels

So there you go. Those seem reasonably honest claims to me. Having panels on the side of the car will make a big difference. It's almost as good as having panels which track the sun.

The part which causes me problems is that a bunch of guys on kickstarter are going to make an electric car with solar panel body and sell it for 14k bucks. Really?

That, and the moss on the dashboard:

[Nusa]

Those prices were without the battery, which will either significantly increase the final cost or be supplied via a rental scheme.

[Codebird]

Drivers around London are probably more excited by the moss air filter than the solar panels.

[mtdoc]

"A total of 330 SunPower cells are producing 1,208 W peak at an efficiency of 24 %.
This amount could provide power for up to 40 km in one day. However, this is a theoretical maximum value which is highly unlikely to be achieved under real-life circumstances."

"For the solar panels we use monocrystalline silicon cells."

https://www.indiegogo.com/projects/sion-a-solarcar-for-everyone-car-solar#/

7.5m^2 of panels

So there you go. Those seem reasonably honest claims to me. Having panels on the side of the car will make a big difference. It's almost as good as having panels which track the sun.

Unfortunately, no.

1200 watts STC PV can, even under ideal real world conditions, produce perhaps 1000 watts of usable power over any meaningfull length of time.  But ideal conditions will NEVER occur in this case. In fact far from it:

There will never be a time when anywhere close to all the panels are in full sun.

Roof and hood panels will only ever be in full sun near midday and even that will only occur for part of the year (unless near the equator) or not at all if too far from the equator.

The door panels will never see direct sun unless the car is on an Arctic or Tierra Del Fuego plain mid-summer and slowly driven in a circle to follow the sun....

Even if and when any modules on this car are in full sun, they will be unable to produce anywhere near to their theoretical max power due to the heat that will rapidly build up. Of course some sort of active collong could be engineered but that would use power...

So in the real wotld, that much PV, in that varied array orientation, integrated into the skin of a car in that way, could be expected to produce on the order of 1-2 kWh of energy if the car is in the full sun for a full day.

How much range will that add ? ....

Oh, and 1200 W of Sunpower PV cells alone will cost at least $4k or so..

[Fungus]

"A total of 330 SunPower cells are producing 1,208 W peak at an efficiency of 24 %.
This amount could provide power for up to 40 km in one day. However, this is a theoretical maximum value which is highly unlikely to be achieved under real-life circumstances."

"For the solar panels we use monocrystalline silicon cells."

https://www.indiegogo.com/projects/sion-a-solarcar-for-everyone-car-solar#/

7.5m^2 of panels

So there you go. Those seem reasonably honest claims to me. Having panels on the side of the car will make a big difference. It's almost as good as having panels which track the sun.

Unfortunately, no.

Which part of those claims I quoted is hugely dishonest?

Roof and hood panels will only ever be in full sun near midday and even that will only occur for part of the year (unless near the equator) or not at all if too far from the equator.

The door panels will never see direct sun unless the car is on an Arctic or Tierra Del Fuego plain mid-summer and slowly driven in a circle to follow the sun....

Yes, but they have both. That means you can live at a reasonable latitude.

Even if and when any modules on this car are in full sun, they will be unable to produce anywhere near to their theoretical max power due to the heat that will rapidly build up.

In the previous paragraph you said they'll hardly ever be in full sun. 

So in the real wotld, that much PV, in that varied array orientation, integrated into the skin of a car in that way, could be expected to produce on the order of 1-2 kWh of energy if the car is in the full sun for a full day.

How much range will that add ? ....

On a Nissan Leaf it would add 5-10km.

[mtdoc]

Which part of those claims I quoted is hugely dishonest?

"However, this is a theoretical maximum value which is highly unlikely to be achieved under real-life circumstances."

The honest statement would be that this will never, ever be achieved in this car, nothing even close to that will be.

Yes, but they have both. That means you can live at a reasonable latitude.

You can live anywhere but you'll never live in a place where you make use of all the panels at the same time. In almost all locations the door panels will always at all times be nearly useless for power production.

Even if and when any modules on this car are in full sun, they will be unable to produce anywhere near to their theoretical max power due to the heat that will rapidly build up.

In the previous paragraph you said they'll hardly ever be in full sun. 

The word "Even" is a qualifier as in "Even if the above was not the case" . So the point is even if the car was large enough to put 1200W of PV on its roof and parked midday, in full sun, on the equator,  it would still not be able to get anywhere close to the theoretical power output.

[Avacee]

The repairs costs after an accident will be higher for that car so the insurance premiums will be higher to compensate. A ding/dent in your door in a car park has now got even more expensive and a major accident will push the cost even more towards it being declared a write-off and the associated environmental costs entailed.
I fully expect they'll be announcing a very expensive solar covered roofbox soon for those times one will cover the car's roof:p

And where does the captured dust go?.. Assuming the magic moss doesn't magically discharge the captured dust outside the vehicle it either needs a backwash system or replacements (at what cost and availability?) .. or does it just block/stop working (a bit like all the other filters until replaced)?

[mtdoc]

I'm not sure most people realize how big of an effect temperature has on PV power output in real world conditions.

There is variation depending on the cells temp coefficient, but in real world conditions a typical, properly mounted PV panel - mounted to allow good airflow across both sides of the panel -  will still see an efficiency drop of about 10% (relative to STC) when the panel is in full sun. Of course once you add to that wire losses and charge/discharge efficiency losses, usuable power generally comes in at 20-30% below STC.

In this car, with panels mounted flush and hence no air flow underneath, efficiency losses due to temperature alone are going to be much worse than the temperature losses for a typical roof or rack mounted PV.

[Kevman]

My Bolt is averaging 6.1 Km / KWh right now.

How much weight do the solar panels add and what is its impact against the vehicle's efficiency? EVs have a lot of lightweight materials in them to help keep weight down and this seems to add a lot back, especially since the hood and roof is basically going to have to windshield glass on it.

It might charge enough to come out ahead in the summer, but what about when you look at it year round? Is it worth it to haul all that weight around all year to gain only significant amounts during certain months?


That would be a direct strike against range, too, which is more important than the cost of charging. Trust me, the cost of electricity is hardly significant when it comes to owning an EV. This really helps against the part of EV ownership that no one really concerns themselves with and hurts in the area that everyone does. 

Tesla has been looking into it, though, but had trouble meeting crash standards with it... https://electrek.co/2017/02/28/tesla-model-3-solar-roof-panasonic/

[Fungus]

FWIW I think this is a bad idea.

All I'm saying is that the claims made seem to be within half an order of magnitude.

(and that's very unusual for this type of project)

[eugenenine]

I thought the Pius was available with solar panel on it already.

[Brumby]

Maybe parking it across the road from 20 Fenchurch Street could have improved power generation.


... but they've put up shades now, haven't they?   

[2N3055]

Parking car in shade, so you don't have to use air conditioning afterwards to cool whole car from 60°C will probably extend range in the same ballpark ...

[rs20]

I wonder, in reasonably typical conditions (average weather, car is in shade some of the time, etc), whether the added weight (and maybe drag) of all the panels and conversion circuitry would reduce the range, and how that would compete with any gains? There must be some sort of typical break-even usage situation where those outcomes would cancel out exactly, it'd be interesting to express the feasibility of this concept by describing that situation (and how ridiculous or sensible it seems).

Leaving the car parked out in the sun is not one of those situations, because you'd obviously be better off putting those panels on the roof, correctly angled and not weighing down the car, etc.