I have always liked this idea, it is such a neat middle ground between massive grid scale systems and the hassle of individual system maintenance.

I don't understand the purpose of consumers owning individual solar panels in a large array. How is that better than a single entity owning the whole array, and what function does the consumer provide?

I don’t think the Silverado is optimized for driving range, but rather - can it do typical “truck” stuff. For example hauling and/or towing. For this workload, having more towing capacity in a slightly less aerodynamic package is probably a good trade off. You don’t get a truck for the efficiency, you get one so you can do stuff with it.

Still, having a 400 mile range also makes this more useful for the middle of the country where there are wide open spaces between towns for charging. Also, having a legitimate truck EV makes it more likely for traditional truck buyers to think of getting an EV.

Part of it is the weight of a battery this size but the bigger issue is the aerodynamics of the large frontal area.

The Lucid Gravity has a 450 mile range with a 123kWh pack. It’s the only other vehicle with a range close to the GM large packs.

You can do bidirectional with most GM vehicles now with the GM energy solution. I don’t have this but I did have a call with them.

Thier max output is only 9.6kW so it can’t do a whole home backup and the car can only run in backup mode when the grid is out.

https://gmenergy.gm.com/

I consume about 17MWh a year between two EVs and a large heat pump for winter heating.

I will have overproduction now with the 2nd array. We do have net metering at about 80% of the cost on NEM 2.0. Our bill is split by transmission, generation, distribution and fees. We get 100% on transmission and generation and 25% on distribution.

https://www.energy.nh.gov/sites/g/files/ehbemt551/files/inli...

From an efficiency standpoint, we should probably be building grid-scale solar in Alberta and pumped storage in BC. There's more sunshine on the east side of the Rockies.

As a resident of Alberta, I pay $0.205/kWh for energy and delivery, which I largely attribute to bad decisions made by our provincial government. Even still, my 10 kW rooftop solar install is barely financially viable at those rates.

With that said, it would help if the Canadian government didn't have enormous tariffs on solar panels. Canada levies taxes such that solar panels here cost nearly triple what they cost elsewhere.

The relevance is readily apparent to people who aren’t grumpy yahoos.

The Prius Prime solar panel roof I think can net 3-6 miles a day under ideal conditions (which we're probably close to here in Arizona). I think that's a little more than people would expect, but still only applicable in niche conditions (tiny daily commute, or a longer non-daily commute). I think the math works out to ~4-6 years to break even for the cost of adding the solar roof assuming $0.15 per kwh, which isn't terrible.

If solar tech gets more efficient or cheaper, I think it starts becoming a much more attractive option in some areas. If you get into the 10+ miles per day range, that would cover a lot of peoples commutes in certain areas.

I just started doing this with my car, mostly to add a camera/temp monitoring for when I leave my dog in the kennel in the car (she's well watched over, please don't fret over it).

I'm hooking it up via starlink specifically so it works in remote areas with no cell coverage too.

Monitoring and proxying everything via an RPI as well. Victron DC-DC inverter to keep the bluetti battery pack charged with bluetooth relay boards so we can turn loads (camera/starlink/others) on/off programmatically (it only turns the starlink on when there's no good/known wifi for example).

Fun project, combines software dev (which I'm fairly good at) with hardware work (which I'm less) and my dogs (which I'm a big fan of).

The maths says that the *mean* number of miles driven by a vehicle is surprisingly low, and that tiling the surface of a car can get to about 80% of that *mean* in places where the car is just left out on the street and not shaded parking.

But!

That's a practical consideration at the level of "should a government require EV makers to design the roof, bonnet, doors etc. to be tiled in PV in order to reduce, but not eliminate, the induced extra demand on the grid" and definitely not "should I personally bolt a small, fixed, PV panel and inverter into my EV as an aftermarket DIY job?"

The former gets wind-tunnel tests for efficiency, QA, designed around all the other safety concerns cars have e.g. crash safety.

The latter, doesn't.

Very nice. How long does that tend to stay alive for? And what kind of cold weather conditions do you have to contend with?

If only we didnt start off with having 3000+ lbs of metal to move a 100-200lb person as a design limitation

The simplicity of EVs is one of their big strengths! Compare all the cooling, transmission, lubrication and fuel systems of an ICE car to the simple Electric Motor of an EV. Vastly simpler. As an end user, I see it to, my EV has no scheduled maintenance, whereas the ICE wants me to take it to the dealer every 20k miles.

The 2010 Prius IV had this as an option - one of my favorite cars due to low maintenance (the lowest maintenance visits per year for its era). The solar panel air vent circulation is a nice feature (even if slightly gimmicky) and I suspect extends the hybrid battery life as well by preventing some marginal battery heat death while parked.

The newest (2023+) Prius brought back the solar roof as an option - and this time it charges the battery (albeit marginally / but not bad for those that drive minimally).

A more practical solution is to leave the windows slightly open so the hot air escapes.

You might like the series by youtuber 'Power of Light' where he packs solar panels in his car to charge his car to do a solar cannonball run from New York to California on those solar panels alone: https://m.youtube.com/playlist?list=PL9nfj0jfPXYBF8FO7sckzvV...

Can't remember how long it took, think a couple weeks at least?

Not sure if I've slipped a 0 here but 500w taken over the year, at say a 10% capacity factor, is still over 3500 miles of range per year. A fair bit short of the average mileage (in the UK somewhere around 10k) but still more significant than I expected. Of course 500w is a lot of solar for a car and 4 miles / kWh is also quite efficient.

I think this is a flawed comparison. You only care about speed when driving, but charging we care about whenever the car gets sunlight. I would argue for most people car in sunlight time is a multiple of car driving time. Still pretty abysmal, but less bad than 2 mph.

This is a good way to look at it, but perhaps a new unit, like range per hour? Since mph is alreday a unit of velocity.

There have been solar car competitions that colleges have been doing for decades. Here's a YouTube compilation of one that ran last week: https://www.youtube.com/watch?v=ZBin-oXBJzM

I think it can help calibrate people's intuitions about what you can expect out a pure-solar car.

You also need to remember that inside those shells is basically nothing but a driver. No AC, no seats for people beyond the bare minimum. And that's broad daylight. So you need to look at them doing 20-30mph and bear in mind that it's still not comparable to a street-legal sedan of a similar size doing 20-30mph... those cars are essentially as close to "a mobile cardboard box" as the competitors can make them.

You might be able to build something that people would agree is "a bus" that moves with a couple of people on board, but it probably will stop moving once it enters shadow. Anything that we'd call "a bus" is going to need a lot more physical material per unit solar input than those cars have. I'm not sure that even "moves with a couple of people on board" will necessarily end up being faster than those couple of people walking, either. It's effectively impossible to power a vehicle with its own solar footprint in real time. It also ends up difficult to use them to power batteries because having to move the additional mass of the batteries eats up the advantages of being able to gather power for larger periods of time. It's possible, because of course you can hook a car up to solar panels and eventually charge it, but you don't get very many miles-per-day out of it for what fits on the car itself alone if you work the math.

It's an interesting idea. I did some napkin math based on the Solaris Urbino 18 bus. The buses have about 45 square meters of ceiling area (18m by 2.5m). Assuming efficient solar panels you could get 250w/sqm. That works out to 11.25 kwh/hour. The bus advertises with 600km of range with 800kwh of batteries so that is 1.33 kwh/km. Hence it could do ~8km/h on average when it is sunny.

The math does not really work out to a viable product with this bus, but it is not too far off. A city bus that has been purpose-built for low speed in urban areas without other traffic may work as it can make some sacrifices. For instance, since it runs much slower on average it would need smaller engines. It could also use more light-weight material since it won't need to handle high speed collisions. If it is just used for short distances within a city center it could also do away with seats. Lower speed should also lead to lower consumption.

The Solaris Urbino 18 weighs 17.5 tons curb weight. Assuming fuel consumption is pretty linearly related with weight and you could get it down to less than half, you could get a bus with a range of 10 miles per hour of charging. If it drove for 6 hours a day, but got charged for 12, 20 miles on average per hour is possible.

4kW on a bright sunny day, for a few hours around noon. Even my small EV outputs 100kW when floored, and 4kW doesn't get it very fast.

We have trams. We don't need to make worse trams

I suspect the lightweight, and hence low power requirements, are the correct part of the hypothesis. But making the vehicle as big as a bus implicates a lot of weight. Maybe a solar charging cargo bike fairing would have some benefit, but that's an expensive bike and it will tend to get stored indoors.

Maybe an electric assisted pedal bus with a solar roof would make sense.

Very location specific, might do wonders in Cancun or San Francisco or Vegas, not so much in Gatlinburg or Seattle or anywhere where there is not a lot of tourism or where there is a lot of rain or that has a long snowy season.

One horsepower is roughly equivalent 754 watts. 4000/754 = 5.305 horsepower. Even tripling it only gets you to 15 HP.

I am not an automotive engineer but I doubt that is enough power for a bus that people can ride.

Well, if you have a fixed route you are not limited by space on the vehicle to put solar on, but can provide electricity via a rail or wire or something and then gather energy on some larger Solarstation or from wind turbines or what else comes to mind.

Then you can reduce rolling resistance by using steel tracks and steel wheels ...

... and oh, you have invented the tram/light rail ;)

(But even with solar you need to finance the construction and maintenance, even the slow vehicle need some ... thus either tax finance or charge fares or mix income)

Yep. A solar car ceiling seems great to make EVs more reliable on the hands of people that only charge them rarely or may travel to the middle of nowhere and can get surprised by battery faults.

Those are a very small share of car owners, and EVs are nowhere close to the market penetration to care abut them. But it will eventually make sense.

I believe that solar panels were an option on the Maybach 62S, and they would run the ventilation fan while you were parked so you wouldn't return to a hot car after going to the store.

Like everyone else has said - there just isn't enough area on the top surfaces of a car to do any noticeable charging.

Using "270Wh/mile" from another comment,

(61kWh/month) / (270Wh/mile) / (31day/month) = 7.3mile/day =~ 11.7km/day

(39kWh/month) / (270Wh/mile) / (31day/month) = 4.7mile/day =~ 7.5km/day

My conmute is like 3 or 7 miles (4 or 11 km), depending on where I have to go.

Anyway, I expect that a rooftop installation is much more efficient.

60kWh may be enough for occasional short trips.

When I'm not using my vehicle, it's in my garage.

Of course. It is an intriguing idea, but a local maximum.

- The panel sits at open-circuit voltage of 48V

- That then needs to be converted/boosted to 400V (conversion loss)

- The converter needs to talk to the BMS to make sure batteries can be charged at this moment (component that is live all the time and is a current draw)

- Need to think about it, but you want another set of contactors between panel and HV-Bus where the battery sits (current draw)

1km of driving is 150Wh so 1kWh gets you 6.6km or 4.1 mi

Let's be generous and say you have a 500W panel(punchy) for 8 hours at full blast (doesn't happen), you get 500W x 8 hrs = 4kWh. Lets say isolated converter loses you 10% so you are at 3.6kWh Thats 24km or 15mi of driving in perfect conditions.

2x Gigavac contactors, keep them closed costs you 24W, so that lowers the input further to 476W * 8hrs = 3.8kWh, less 10% = 3.42kWh ...

Someone who studied EE might be able to make this more accurate. Back of the napkin math, not totally impossible, but not worth adding it for a trickle charge. Adding components that can break, adding weight etc.

There are interesting solar cars out there where you reduce the weight heavily and fold out big solar sails. Then you are getting somewhere, for a city car you don't have enough surface. For an SUV or American Style Flatbed truck you have so much weight it's not worth it either.

But an RV is also way bigger and heavier.

RV panels make sense for the boondocking use case, where you want to charge computers or power a satellite internet terminal or something, but I can't imagine actually trying to drive on that trickle of juice.

It’s always going to be anecdotal. I reckon a mid size RV (say upper class B) will have 1500-2000W of solar capacity, if it’s really boxy. It’s going to have the aerodynamics of a brick. Meaning you’ll be lucky to get 1mi/kwh at highway speed, maybe 2~2.5 if you keep under 30.

So you’ll be charging at 2~5mi/h, if the sun is shining straight overhead.

It’ll count for something if you park the RV in the sun for a week as you camp somewhere, but on the road it gives you some limping ability and that’s about it. The main benefit is not running the AC off of the engine.

It doesn't make sense to power any vehicle with onboard solar. There are no electric RVs yet because the batteries required to have any amount of range are cost prohibitive and heavy.

I put 1800W on my RV and that's covering the roof end to end. I'd guess it'd be enough for something like 1-2 miles a day on an electric drive train, assuming you don't use power for anything else.

Even better to get a fixed structure such as a garage or carport, that keeps the vehicle safe and out of the sun, and cover that in Solar.

It has larger surface area, doesn't weight the vehicle down at all even if it's built in a less weight-efficient way, and the vehicle doesn't need to be exposed to the elements.

Who lunches for several days/weeks? logically you would charge high speed through a plug with energy generated by panels that are much more efficiëntly (money+yield) placed and not have to carry around.

People are absolutely starting to populate their RVs with solar. What I've seen so far is just a few panels - around 600 watts. Usually connected to a battery separated from the RV wiring.

Yes! Exactly this.

My last EV used 22 MWh over 6.5 years. That works out to 390W.

My solar array is located at high latitudes (northern Minnesota), the mounting angle isn't great, it's occasionally covered in snow, etc. In these conditions, I need 6.3 solar panels to produce 22 MWh over 6.5 years.

The area used by 6.3 solar panels -- enough PV to cover _all_ my EV's energy needs -- works out to be a parking spot large enough to fit the vehicle but not large enough to fully open any of the doors.

Exactly.

Only thing holding off my EV purchase is that I want proper V2G support. If I'm paying for 100kWh of lithium battery capacity I damn well want to use it as a backup for my house.

That's actually mandatory in France for large parking lots

Honestly we should consider giving generous tax benefits so that every open air parking lot in any city in America that has more than 50,000 residents would be stupid to not have solar installed that covers the front of the cars in the parking lot and the walkways between the lot and the stores.

That's so much real estate available that would lower electricity costs, decrease the amount of AC used to cool cars down, and make going to malls and similar places a little nicer for everyone.

Exactly. Maybe just because I live in a city and almost everyone I know with a car will just find street parking somewhere within walking distance of their apartment.

So .. it would make sense to make a law that requires new parking spaces to have a solar roof which can charge the cars which park there for a few. This would spread rather quickly, I think.

I have solar panels at home and can charge a car .. but I'm mostly parked elsewhere when the sun is shining the most.

The study literally proves you wrong.

The big issue tends to be complex logic for going to sleep often getting stuck. Ie. "oh, I was trying to use the LTE connection to poll for updates, but the connection got reset so I kept the CPU awake forever whilst retrying every 5 minutes rather than going to sleep mode".

Older cars had this too - I had a bunch of cars which would kill their own batteries if not locked - the engineers assumed that all owners lock the car when walking away, which often isn't the case in your own garage.

It's not, but older cars tried to keep their batteries fully charged. Newer cars with the so-called "smart" alternators never keep the battery full, they always leave some empty capacity to recover energy while moving.

Doesn't anti-theft precautions kick in when you do this? On my Honda, if the battery goes completely dead or when I replace it, I have to enter a code in after, and IIRC all my radio stations reset, so it would be really inconvenient to do this often.

My way around this, which is also somewhat inconvenient- is that I pop the hood and connect a trickle charger if I have a feeling I won't be driving for a few weeks. I have a garage so this is the lesser evil.

I haven't found any appreciable drain on my EV's primary battery over the longest period I've left it sitting so far (a little over a week, so not that long, admittedly), but the car _does_ do a very bad job of keeping the 12V battery charged and I've already had to replace it once in <2 years of ownership, plus I bought one of those small jump start packs in case it ever dies not at home (luckily, for an EV, it barely requires any power at all to turn everything on and get it started, so the very smallest, cheapest, jump packs are way more than sufficient). A built in trickle charger to combat that would indeed be nice, if the car companies are incapable of figuring out the logic necessary to do it off of the massive primary battery.

Can you elaborate here?

I went the plugin hybrid route. The added complexity caused a lot of maintenance and reliability issues. I ended up having to dump the vehicle at a loss.

Something to keep in mind: A full EV doesn't require oil changes, which you still need to do with a plugin hybrid.

If you're able to do all your daily driving on battery only, then why bother with a gas engine that you aren't using? High speed charging works very well for the occasional road trip; it's at the point where if you take your bathroom breaks at high-speed chargers, you don't even need to "think" about charging.

I'm sure; it's certainly intuitive that a hybrid could do quite a lot with a PV setup. I just don't see PV doing much for a non-hybrid ICE vehicle outside of acting as a battery tender.

Let's not forget to do the math on how much less efficient the vehicle is over all with panels strapped to the top messing with the aerodynamics.

Even then, he said hybrid.

If he only drives Mo-fr the math works out though

Are we sure his car wasn’t a Twike or something? There’s ultralight EVs for which this could work.

Edit: Never mind, “hybrid station wagon”.

I don't remember the exact details, it's possible that he charged it over the weeked (or just didn't use it, thus getting 2 extra day of charge).

You can play around with assumptions, like what if it was driven in stop-and-go traffic at very low speeds? Then your quoted 270Wh figure might be lower.

But anyways, with these general conditions, with the numbers you quoted, and with a 10 kwh battery (aspull), you'd be looking at a net loss of 775Wh/day, which means you could go 13 days between charges.

The point I tried to make, is that solar panels on hybrids/EVs add a lot of practical value to people who can't charge at home/work, and it's not just meaningless greenwashing.

Also that 2.6kWh figure is a yearly average probably, sunlight varies greatly over the year.

My exact numbers might be off (which is kind of a problem it seems on HN), but the point still stands - you can add practical amounts of range by having the car just sitting there, even in places where there's not that much sunlight.

Besides, I just checked out panels, and there's a lot of 500w ones that are appx 1mx2m, these station wagons are huge, easily 2m wide and 5m long, half of it a flat roof, so its not outrageous.

A lot of car parks have chargers. Wiring up low wattage chargers is no big deal, considering AC chargers are just wiring+breakers. Considering cars will spend a long time here, large wattages are not needed, you could wire up a multi-story parking lot for chump change, and the entire wattage would be still less than a DC fast charger serving half a dozen cars.

Those people dont read papers or believe science

I don’t believe the primary cost is so much the physical panel but the cost to engineer and design it into a roof, also the additional systems needing to hook it into the wiring harness. It’s a fun toy for some but has no real benefit for the many.

Needless manufacturing complexity. Far better having static panels with current tech.

They are nice gimmicks like that newer model of Prius but far from being economic reality.

That option is a gimmick though.