3 ms·

A company I worked with looked into this model. The problem is that most cars are not in garages near PV during the day, they're in parking lots at work or in

A company I worked with looked into this model. The problem is that most cars are not in garages near PV during the day, they're in parking lots at work or in shopping/errand locations. They return to garages and plug in just before sunset, so the load on the grid from EVs actually goes up right as the input from PV is going down. The model does work great with powerwall-type devices, though.

sp332 7y ago
But if you offer to pay people who keep their cars plugged in during the day, probably more people would do it. Also, while car batteries are likely to be lower in the evenings, they're probably not completely dead. They could feed the remaining energy back to the grid at that time, then charge up later at night when the load is lower.
- mdorazio 7y ago
  1) The percentage of people with EVs who leave them plugged in at home during the day is very small. This is unlikely to change for several years. 2) It's a bad proposition to people because you're basically telling them they won't be able to take long trips in the morning and you're going to decrease the life of their battery (people are rightfully really concerned about this). 3) The big concern with utilities right now is how to handle home renewable excess power during the day. All the rooftop PV is feeding a bunch of power back into the grid when it's sunny, then all those homes are sucking down power from dusk to dawn. The utilities need daytime power storage or non-daylight generation to offset this. Storing power at night doesn't do much to actually solve the problem, so there's not much of a business model in it. Grid-scale battery installations are quickly becoming the solution here. If you're looking for a car-based model that could potentially work for this, it has to involve solar parking lots and also be car-specific. Charge your car at a parking lot during the day, drive it home and plug it in to power your house in the evening. Get a discount from your electric company as a result.
  - oceanplexian 7y ago
    I sorta get the idea but who wants to burn cycles on your EV to save a couple of bucks a month? It makes no sense to me. You can just buy batteries for your house. We’re down to what? $200/kWh? Less? If there wasn’t so much mark up in the industry, you could buy a whole house battery for 2-3k that would be good enough to shift most of your energy usage. Utilities just need to incentivize it, which presumably would happen naturally due to market forces as solar adoption goes up.
beefield 7y ago
What stops the cars being charged at the parking lot at work or shopping/errand locations? One could imagine a distributed model where you have a small battery home and you not only shop your groceries but also the electricity and bring that home with your car. (Likely not relevant model in densely populated areas)
- ben_w 7y ago
  In that scenario, the parking lots need to be on the grid. Even if you cover a car in solar panels, for almost everyone they’d be a range booster rather than turn the car into a net producer.
  - AnthonyMouse 7y ago
    > In that scenario, the parking lots need to be on the grid. Not necessarily. You can imagine a grocery store covering the roof of their building in solar panels to run chargers in the parking lot. If solar gets cheap enough they might even do it for free (or below market rates) to drive business to the store. Then you charge up your car while shopping, use the power at night.
    - ben_w 7y ago
      Even that won’t be enough. At least, that’s what I remember from https://withouthotair.com/c6/page_42.shtml https://withouthotair.com/c6/page_42.shtml Don’t get me wrong, I’m optimistic about replacing fossil fuels and think things are already better than McKay dared to hope for, but I think a grid has to be part of the solution. Grid is also useful for time shifting power demand/production to smooth out the morning/evening dips, for space-shifting production to deal with clouds etc., and (assuming wind is part of the solution) the best wind resources aren’t where you actually want to build houses.
      - AnthonyMouse 7y ago
        > Even that won’t be enough. It looks like you're right that just covering the store and parking lot in panels wouldn't be enough. But then you've got two possibilities. One is the store is in the city, and then it can be on the grid, because there is always going to be a grid in the city. The other is the store isn't in the city and then you've got cheap land next to the store to fill with panels and turbines. > Grid is also useful for time shifting power demand/production to smooth out the morning/evening dips, for space-shifting production to deal with clouds etc., and (assuming wind is part of the solution) the best wind resources aren’t where you actually want to build houses. But batteries (especially when they're in cars) do the same thing. Your house may not be on the grid, but it's got panels on it that power it during the day, meanwhile your car is out getting charged up somewhere else, and you use that power at night. Electric car typically has a >50kWh battery, which will power a typical household for about two days on its own, call it twice that if the house runs on its own panels during the day. So as long as you get the equivalent of a full charge twice a week, that's all you need, right?

sp332 7y ago

But if you offer to pay people who keep their cars plugged in during the day, probably more people would do it. Also, while car batteries are likely to be lower in the evenings, they're probably not completely dead. They could feed the remaining energy back to the grid at that time, then charge up later at night when the load is lower.

mdorazio 7y ago
1) The percentage of people with EVs who leave them plugged in at home during the day is very small. This is unlikely to change for several years. 2) It's a bad proposition to people because you're basically telling them they won't be able to take long trips in the morning and you're going to decrease the life of their battery (people are rightfully really concerned about this). 3) The big concern with utilities right now is how to handle home renewable excess power during the day. All the rooftop PV is feeding a bunch of power back into the grid when it's sunny, then all those homes are sucking down power from dusk to dawn. The utilities need daytime power storage or non-daylight generation to offset this. Storing power at night doesn't do much to actually solve the problem, so there's not much of a business model in it. Grid-scale battery installations are quickly becoming the solution here. If you're looking for a car-based model that could potentially work for this, it has to involve solar parking lots and also be car-specific. Charge your car at a parking lot during the day, drive it home and plug it in to power your house in the evening. Get a discount from your electric company as a result.
- oceanplexian 7y ago
  I sorta get the idea but who wants to burn cycles on your EV to save a couple of bucks a month? It makes no sense to me. You can just buy batteries for your house. We’re down to what? $200/kWh? Less? If there wasn’t so much mark up in the industry, you could buy a whole house battery for 2-3k that would be good enough to shift most of your energy usage. Utilities just need to incentivize it, which presumably would happen naturally due to market forces as solar adoption goes up.

beefield 7y ago

What stops the cars being charged at the parking lot at work or shopping/errand locations? One could imagine a distributed model where you have a small battery home and you not only shop your groceries but also the electricity and bring that home with your car. (Likely not relevant model in densely populated areas)

ben_w 7y ago
In that scenario, the parking lots need to be on the grid. Even if you cover a car in solar panels, for almost everyone they’d be a range booster rather than turn the car into a net producer.
- AnthonyMouse 7y ago
  > In that scenario, the parking lots need to be on the grid. Not necessarily. You can imagine a grocery store covering the roof of their building in solar panels to run chargers in the parking lot. If solar gets cheap enough they might even do it for free (or below market rates) to drive business to the store. Then you charge up your car while shopping, use the power at night.
  - ben_w 7y ago
    Even that won’t be enough. At least, that’s what I remember from https://withouthotair.com/c6/page_42.shtml https://withouthotair.com/c6/page_42.shtml Don’t get me wrong, I’m optimistic about replacing fossil fuels and think things are already better than McKay dared to hope for, but I think a grid has to be part of the solution. Grid is also useful for time shifting power demand/production to smooth out the morning/evening dips, for space-shifting production to deal with clouds etc., and (assuming wind is part of the solution) the best wind resources aren’t where you actually want to build houses.
    - AnthonyMouse 7y ago
      > Even that won’t be enough. It looks like you're right that just covering the store and parking lot in panels wouldn't be enough. But then you've got two possibilities. One is the store is in the city, and then it can be on the grid, because there is always going to be a grid in the city. The other is the store isn't in the city and then you've got cheap land next to the store to fill with panels and turbines. > Grid is also useful for time shifting power demand/production to smooth out the morning/evening dips, for space-shifting production to deal with clouds etc., and (assuming wind is part of the solution) the best wind resources aren’t where you actually want to build houses. But batteries (especially when they're in cars) do the same thing. Your house may not be on the grid, but it's got panels on it that power it during the day, meanwhile your car is out getting charged up somewhere else, and you use that power at night. Electric car typically has a >50kWh battery, which will power a typical household for about two days on its own, call it twice that if the house runs on its own panels during the day. So as long as you get the equivalent of a full charge twice a week, that's all you need, right?