4 ms·

At 1m^2 for the panel and a top end panel its going to peak out at ~230W. In an hour that is 230 Wh. That is 230Watts during the peak hours of the sun assuming

At 1m^2 for the panel and a top end panel its going to peak out at ~230W. In an hour that is 230 Wh. That is 230Watts during the peak hours of the sun assuming its angled to directly capture the sun, which it doesn't appear to be in their concept CGI. Its probably going to be less than that. The Zoe which is a small electrical car has a 100KW engine for acceleration purposes. It goes 4.5 miles using 1Kwh of power at 31 mph (20C). It will cover that distance in 9 minutes at that speed. 230Watt hours in an hour of charging is a very far way from the 6.9Kwh needed for an hour of driving and this is optimal conditions as people brake/accelerate and travel faster than 31 mph. This design might reduce the cost from the grid a bit and be useful for camping and trickle charge a bit through the day if its in a car park etc. But its not enough to run even the smallest electrical car today, its an order of magnitude off and even with a 100% efficient panel the cars would need to be 7x more efficient than they are today, and electric cars are already a lot more efficient than combustion engines. It fundamentally doesn't add up as a concept.

rbanffy 3y ago
Besides, it’s probably a better idea to always extract peak power from the solar array to charge the battery and let the motor use it at its own peak efficiency. The math doesn’t add up at all. But they did publish it (and it got some press buzz), so their goal was achieved.
hn_throwaway_99 3y ago
At this point, I think we should be willing to call out these ideas for being unhelpful distractions from what will really be needed to combat climate change. As you point out, the math just doesn't add up. Photovoltaics on car roofs is just a dumb idea, beyond perhaps some novelty charging of accessories (e.g. running the A/C on hot, sunny days). There was a good article recently (maybe it was Washington Post, can't remember), about what will really be needed to combat climate change, and I thought it was pretty great. Did a great job of highlighting the things to focus on that can actually be built fast enough (e.g. overbuilding renewables generation, upgrading electrical grids, "electrify everything", etc.) vs what are just distractions that are too small (or slow to build out) to make a dent in what actually needs to happen. You could perhaps argue with the author on some of the details around the edges, but the main points were pretty unassailable in my opinion. These proposals that will never amount to more than a drop in the ocean aren't worth wasting time on, and worse than that, they can make people "feel" like they're doing something valuable when they really aren't (see: most plastics recycling).
abdullahkhalids 3y ago
This recumbent electric bike [1] with solar panels as roof takes 11.8Wh/km (plus human pedaling) to go at a speed of 26.5 km/h. So, one hour of biking, covering 26.5 km will consume 312 Wh. So within optimization distance, you can perpetually run this bike on clear sunny days on the Sun's power alone. So, yeah, solar panels on vehicle works as a concept for for bikes, not for cars. [1] https://www.recumbent.news/2021/05/23/the-ultimate-tilting-solar-powered-serial-hybrid-delta-trike/ https://www.recumbent.news/2021/05/23/the-ultimate-tilting-s...
- antisthenes 3y ago
  And even then, only as a concept. That thing is huge. Can't take it on a bus, attach it behind a car like a regular e-bike. Can't ride it in windy weather lest you get tipped over by a gust. Can't ride in rainy weather (well, I suppose you can, if you just rely on your leg power), but at least it shields you from rain, I suppose. It's just not practical. Leave solar panels stationary where they belong.
aimor 3y ago
Ok but if it was 3 m^2 of panels and if the energy needed was 100 Wh per mile then it starts to look possible. That's Aptera's solar vehicle design. I'm not saying this is currently reality, but in this case 1 order of magnitude doesn't feel so insurmountable that we should dismiss the dream. The article is pretty clear EV applications are a longshot example.
- tppiotrowski 3y ago
  A nice design would be: When you park the car, solar panels cover all the windows or open like flower petals from the roof for maximum power harvesting.
  - throwaway4220 3y ago
    That’s too many moving parts. Hell I would settle for covering up my windshield in the hot sun automatically with no ridiculous collapsible sun shades needing that janky visors
dangus 3y ago
Still, cars spend way more time parked than driving. A Tesla Model 3 (.24 kWh/mile energy usage) would gain up to a mile of range per hour in the sun with this system. It’s not much but it’s not nothing either. If you park outside and live in a city with most of your trips handled by transit and walking it means that you could realistically own an electric car and never plug it in, even in non-ideal conditions. It’s also nice to know that your car isn’t slowly draining like a smartphone when you’re off mains.
chris222 3y ago
You can cover a parking spot with 3-4kW of solar though.
throwaway4220 3y ago
Let me challenge you with this map. https://www.altestore.com/diy-solar-resources/solar-insolation-map-usa/ https://www.altestore.com/diy-solar-resources/solar-insolati... Take 4 kWh/m2 https://insideevs.com/reviews/443791/ev-range-test-results/ https://insideevs.com/reviews/443791/ev-range-test-results/ Take 3 mi/kwh from the table in the middle I know my car sits in the sun at my work in the asphalt lot. My commute is 12 miles each way and it would cover half this about half the year

rbanffy 3y ago

Besides, it’s probably a better idea to always extract peak power from the solar array to charge the battery and let the motor use it at its own peak efficiency. The math doesn’t add up at all. But they did publish it (and it got some press buzz), so their goal was achieved.

hn_throwaway_99 3y ago

At this point, I think we should be willing to call out these ideas for being unhelpful distractions from what will really be needed to combat climate change. As you point out, the math just doesn't add up. Photovoltaics on car roofs is just a dumb idea, beyond perhaps some novelty charging of accessories (e.g. running the A/C on hot, sunny days). There was a good article recently (maybe it was Washington Post, can't remember), about what will really be needed to combat climate change, and I thought it was pretty great. Did a great job of highlighting the things to focus on that can actually be built fast enough (e.g. overbuilding renewables generation, upgrading electrical grids, "electrify everything", etc.) vs what are just distractions that are too small (or slow to build out) to make a dent in what actually needs to happen. You could perhaps argue with the author on some of the details around the edges, but the main points were pretty unassailable in my opinion. These proposals that will never amount to more than a drop in the ocean aren't worth wasting time on, and worse than that, they can make people "feel" like they're doing something valuable when they really aren't (see: most plastics recycling).

abdullahkhalids 3y ago

This recumbent electric bike [1] with solar panels as roof takes 11.8Wh/km (plus human pedaling) to go at a speed of 26.5 km/h. So, one hour of biking, covering 26.5 km will consume 312 Wh. So within optimization distance, you can perpetually run this bike on clear sunny days on the Sun's power alone. So, yeah, solar panels on vehicle works as a concept for for bikes, not for cars. [1] https://www.recumbent.news/2021/05/23/the-ultimate-tilting-solar-powered-serial-hybrid-delta-trike/ https://www.recumbent.news/2021/05/23/the-ultimate-tilting-s...

antisthenes 3y ago
And even then, only as a concept. That thing is huge. Can't take it on a bus, attach it behind a car like a regular e-bike. Can't ride it in windy weather lest you get tipped over by a gust. Can't ride in rainy weather (well, I suppose you can, if you just rely on your leg power), but at least it shields you from rain, I suppose. It's just not practical. Leave solar panels stationary where they belong.

aimor 3y ago

Ok but if it was 3 m^2 of panels and if the energy needed was 100 Wh per mile then it starts to look possible. That's Aptera's solar vehicle design. I'm not saying this is currently reality, but in this case 1 order of magnitude doesn't feel so insurmountable that we should dismiss the dream. The article is pretty clear EV applications are a longshot example.

tppiotrowski 3y ago
A nice design would be: When you park the car, solar panels cover all the windows or open like flower petals from the roof for maximum power harvesting.
- throwaway4220 3y ago
  That’s too many moving parts. Hell I would settle for covering up my windshield in the hot sun automatically with no ridiculous collapsible sun shades needing that janky visors

dangus 3y ago

Still, cars spend way more time parked than driving. A Tesla Model 3 (.24 kWh/mile energy usage) would gain up to a mile of range per hour in the sun with this system. It’s not much but it’s not nothing either. If you park outside and live in a city with most of your trips handled by transit and walking it means that you could realistically own an electric car and never plug it in, even in non-ideal conditions. It’s also nice to know that your car isn’t slowly draining like a smartphone when you’re off mains.

chris222 3y ago

You can cover a parking spot with 3-4kW of solar though.

throwaway4220 3y ago

Let me challenge you with this map. https://www.altestore.com/diy-solar-resources/solar-insolation-map-usa/ https://www.altestore.com/diy-solar-resources/solar-insolati... Take 4 kWh/m2 https://insideevs.com/reviews/443791/ev-range-test-results/ https://insideevs.com/reviews/443791/ev-range-test-results/ Take 3 mi/kwh from the table in the middle I know my car sits in the sun at my work in the asphalt lot. My commute is 12 miles each way and it would cover half this about half the year