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On this topic: Does anyone know why we haven't started to utilize electric cars as a mechanism for nighttime home energy? It seems like having these batteries

On this topic: Does anyone know why we haven't started to utilize electric cars as a mechanism for nighttime home energy? It seems like having these batteries centralized is actually not the right solution, but instead that they should be at the edge, and connected to the home grid, such that they can be charged during the day, and decharged during the night to some maximum amount specified by the user. A Tesla has 50kWh capacity and I typically use 6kWh at night - it seems like an obvious place we could leverage batteries already in existence to reduce the demand on central generation.

Retric 8y ago
Rang is a rather big deal in electric cars. You would need to be able to tell the car, I don’t need X range today before discharging it to the grid is a good idea. On top of that, discharge cycles reduce battery lifespan so you need to make a lot bore they are worth using. The reverse was considered viable as nighttime energy was cheap and as long as you charged before X AM users would presumably not care.
goodcanadian 8y ago
It has started: https://www.indra.co.uk/v2g https://www.indra.co.uk/v2g Disclaimer: I am an employee.
matt4077 8y ago
We (somewhat) have. I was part of a focus/design thinking group for VW working on this. I think what’s mostly holding it back right now is the relative low prevalence of electric cars and that, as far as I can tell, we have not yet reached the point where renewable energy actually needs batteries. The scheme only makes sense when Wind & Solar actually exceeds demand for significant stretches of time. After that, there are some issues: car manufacturers need to somehow find a scheme for them to make it worthwhile for them. Owners need to be compensated at least for whatever wear it inflicts on batteries. They had simulations showing the scheduling would actually be somewhat easy. This was three or four years ago, and their algorithms were already almost perfect in predicting when you would need your car.
qqqwerty 8y ago
One of the main reason is concerns about degradation. Battery capacity and performance degrades as the number of discharge cycles increases. And EV users are particularly sensitive to that degradation (see issues with early Nissan leafs for example). And replacing an EV battery is currently really expensive (often exceeding the entire value of the used vehicle). It does look like with good battery management, the lifespan can be considerably lengthened however. Particularly, if you cap the max charge to 80% and min charge to 20%. This, plus active cooling is probably how Tesla has managed to achieve such good battery longevity. I wouldn't be surprised if in a few years, EV owners get more comfortable with it. Another thing to consider is that right now the 'peak' grid usage (when EV discharge would be most useful) usually occurs in the evening, probably when a lot of folks are still using their EV for commuting. So rolling out the infrastructure to do two way charging is probably not worth the cost because utilization might be pretty low. I.E. What % of EV drivers would have enough spare battery capacity to discharge a non-trivial amount right after their commute. Probably not many, at least not until we either see a big increase in EV capacity (which will probably happen as batteries get cheeper).
- AnthonyMouse 8y ago
  > What % of EV drivers would have enough spare battery capacity to discharge a non-trivial amount right after their commute. It would probably still be pretty high. Total ranges are in the hundreds of miles, but the average commute is 16 miles, so most of the capacity would still be there when you get home. The real question is going to be whether it's cost effective. If you do that and then have to replace the battery twice in ten years instead of once, is that actually more profitable than having one battery for your car that lasts ten years and another which is purpose built for grid storage and also lasts ten years? Basically a question of time value of money vs. whether being built for purpose is sufficiently more efficient.
  - qqqwerty 8y ago
    The point I was trying to make was that 2 way charging infrastructure is not cheap[1]. And right now battery storage is really only cost competitive as a peak flex provider largely because you need to pay for the electricity that goes into the battery, i.e. a battery does not generate electricity, it merely allows for price arbitrage. So you would have to try and make your money back by only selling during a 2-3 hour window each day, and that window happens to coincide with prime commuting hours. So even if you weren't commuting during that time, ever, you would be making about ~$1 per day[2] and $365 per year. Assuming $5k in infrastructure costs you are looking at 13 year payback, and this ignores battery degradation entirely, among other things[3] [1] Lets say $5000, which is pretty reasonable considering you would need a new charger, an inverter, and would probably have to modify your vehicle. [2] You are arbitraging, so lets' say you but at $0.08/kwh and sell at $0.16/kwh. And in 2 hours you can discharge 10-15 kwh, which puts you in the $1 dollar per day range. [3] Also assume the utility will pay you retail rates for you kwh.
toomuchtodo 8y ago
Tesla has the ability to orchestrate this, and has an ongoing trial program in Scandinavia. It’s only one way though (commanding the vehicle to charge or not); vehicle battery chemistry is not designed to discharge to the grid like the Powerwall/Powerpack products are.
rtkwe 8y ago
A couple come to mind. First is that it'll put additional shallow cycles on the batteries and it would have to include some logic so that it was still full by morning in case the owner wanted to take a long drive. Coming out to a partially charged car after an overnight charge would be bad. On top of that night as far as I know with our current system isn't exactly an expensive time to get electricity because the sun is down and most people are asleep in their homes not in businesses where a lot of peak use is. That will change as the amount of solar in our system increases but for now it's not really an issue. I think the additional cycles is my personal biggest issue with the idea. Battery wear is already among my biggest worries with getting an electric car after years of dealing with the slow terrible decay of cellphone batteries.
criddell 8y ago
Your comment reminded me of the little 10 MW nuclear reactors that Toshiba was developing. The idea was that you bury them around neighborhoods and they work for some decently long time. I wonder what happened to that idea? Is there any hope of small/safe/cheap nuclear power?

Retric 8y ago

Rang is a rather big deal in electric cars. You would need to be able to tell the car, I don’t need X range today before discharging it to the grid is a good idea. On top of that, discharge cycles reduce battery lifespan so you need to make a lot bore they are worth using. The reverse was considered viable as nighttime energy was cheap and as long as you charged before X AM users would presumably not care.

goodcanadian 8y ago

It has started: https://www.indra.co.uk/v2g https://www.indra.co.uk/v2g Disclaimer: I am an employee.

matt4077 8y ago

We (somewhat) have. I was part of a focus/design thinking group for VW working on this. I think what’s mostly holding it back right now is the relative low prevalence of electric cars and that, as far as I can tell, we have not yet reached the point where renewable energy actually needs batteries. The scheme only makes sense when Wind & Solar actually exceeds demand for significant stretches of time. After that, there are some issues: car manufacturers need to somehow find a scheme for them to make it worthwhile for them. Owners need to be compensated at least for whatever wear it inflicts on batteries. They had simulations showing the scheduling would actually be somewhat easy. This was three or four years ago, and their algorithms were already almost perfect in predicting when you would need your car.

qqqwerty 8y ago

One of the main reason is concerns about degradation. Battery capacity and performance degrades as the number of discharge cycles increases. And EV users are particularly sensitive to that degradation (see issues with early Nissan leafs for example). And replacing an EV battery is currently really expensive (often exceeding the entire value of the used vehicle). It does look like with good battery management, the lifespan can be considerably lengthened however. Particularly, if you cap the max charge to 80% and min charge to 20%. This, plus active cooling is probably how Tesla has managed to achieve such good battery longevity. I wouldn't be surprised if in a few years, EV owners get more comfortable with it. Another thing to consider is that right now the 'peak' grid usage (when EV discharge would be most useful) usually occurs in the evening, probably when a lot of folks are still using their EV for commuting. So rolling out the infrastructure to do two way charging is probably not worth the cost because utilization might be pretty low. I.E. What % of EV drivers would have enough spare battery capacity to discharge a non-trivial amount right after their commute. Probably not many, at least not until we either see a big increase in EV capacity (which will probably happen as batteries get cheeper).

AnthonyMouse 8y ago
> What % of EV drivers would have enough spare battery capacity to discharge a non-trivial amount right after their commute. It would probably still be pretty high. Total ranges are in the hundreds of miles, but the average commute is 16 miles, so most of the capacity would still be there when you get home. The real question is going to be whether it's cost effective. If you do that and then have to replace the battery twice in ten years instead of once, is that actually more profitable than having one battery for your car that lasts ten years and another which is purpose built for grid storage and also lasts ten years? Basically a question of time value of money vs. whether being built for purpose is sufficiently more efficient.
- qqqwerty 8y ago
  The point I was trying to make was that 2 way charging infrastructure is not cheap[1]. And right now battery storage is really only cost competitive as a peak flex provider largely because you need to pay for the electricity that goes into the battery, i.e. a battery does not generate electricity, it merely allows for price arbitrage. So you would have to try and make your money back by only selling during a 2-3 hour window each day, and that window happens to coincide with prime commuting hours. So even if you weren't commuting during that time, ever, you would be making about ~$1 per day[2] and $365 per year. Assuming $5k in infrastructure costs you are looking at 13 year payback, and this ignores battery degradation entirely, among other things[3] [1] Lets say $5000, which is pretty reasonable considering you would need a new charger, an inverter, and would probably have to modify your vehicle. [2] You are arbitraging, so lets' say you but at $0.08/kwh and sell at $0.16/kwh. And in 2 hours you can discharge 10-15 kwh, which puts you in the $1 dollar per day range. [3] Also assume the utility will pay you retail rates for you kwh.

toomuchtodo 8y ago

Tesla has the ability to orchestrate this, and has an ongoing trial program in Scandinavia. It’s only one way though (commanding the vehicle to charge or not); vehicle battery chemistry is not designed to discharge to the grid like the Powerwall/Powerpack products are.

rtkwe 8y ago

A couple come to mind. First is that it'll put additional shallow cycles on the batteries and it would have to include some logic so that it was still full by morning in case the owner wanted to take a long drive. Coming out to a partially charged car after an overnight charge would be bad. On top of that night as far as I know with our current system isn't exactly an expensive time to get electricity because the sun is down and most people are asleep in their homes not in businesses where a lot of peak use is. That will change as the amount of solar in our system increases but for now it's not really an issue. I think the additional cycles is my personal biggest issue with the idea. Battery wear is already among my biggest worries with getting an electric car after years of dealing with the slow terrible decay of cellphone batteries.

criddell 8y ago

Your comment reminded me of the little 10 MW nuclear reactors that Toshiba was developing. The idea was that you bury them around neighborhoods and they work for some decently long time. I wonder what happened to that idea? Is there any hope of small/safe/cheap nuclear power?