4 ms·

If we all had electric cars, those batteries would BE the grid.

by smm11 4y ago

idiotsecant 4y ago
This isn't really true without massive distribution system redesign. It could be true for individual homes with transfer switches that disconnect them from the grid if that's what you mean, but a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment.
- bombcar 4y ago
  Even the first part (powerwall setup basically) could be useful. But it’s best when coupled with reduced usage where possible - if we get to a point where the majority of residential electrical usage is cars we’ll be doing pretty well.
- mwint 4y ago
  What substantial investment is required, at the hardware level?
  - jandrese 4y ago
    A big inverter would be the first thing you need.
    - mwint 4y ago
      Right, I guess my question is if anything that needs to be done to the grid itself (outside of individual homes). You're going to have a big inverter anyway to power just your house from your solar panels, batteries, whatever.
      - falcolas 4y ago
        You need transmission lines capable of handling the current. Too much current through local transmission lines can cause drooping lines, which touch trees (i.e. grounding that line), which shuts those transmission lines down automatically. It's something like this that helped cause that big power outage in Chicago. Power couldn't flow through the big transmission lines (they got shut down for a couple of reasons), so it flowed through the local lines towards the demand, and then those were shut down because they hit trees. Ironically, this electrical current issue is also a problem for charging electric cars at stations, since one fast charger at 20% utilization can draw 2-3x more power than the store whose power grid it's attached to.
        mwint 4y ago
        This is the original claim I'm asking about: "a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment." Wouldn't it be less current, in general? If your neighborhood gets 20% of its power from solar panels on your neighbor's houses, it seems clear that power lines inbound to the neighborhood would need to carry 20% less load, and lines inside your neighborhood would also carry somewhat less on average (your power consumption has not changed, and presumably your neighbor is powering his house off his own power before exporting the rest to you). I understand there are probably some topological hot spots, like if one dude has a 1MW solar installation in his backyard, but as a general principle I don't understand what big upgrades need to be done to the grid to support P2P.
        falcolas 4y ago
        Honestly, I'm not qualified to answer this specific usecase. But here's a few numbers to chew on: An average home consumes just a little over 1kW on average, and its connection to the grid will be built to that tolerance. Solar generation is generally peaks around 5kW for an average house installation; individual panels measure between 250 and 400 watts. An electric car's battery pack can, pretty easily, provide in excess of 100kW (based on their charging rates, and the fact that batteries charge more slowly than they can discharge - about 4.6x slower for Tesla battery packs).
        mwint 4y ago
        Huh, this is interesting to me. My house has 400A service (or at least that's the main panel breaker size). 400A at 240V is somewhere in the ballpark of 80kW possible draw. Does something bad happen if I actually use my home's full service for an extended period? I understand bad things would happen if everyone on my block did. As a thought experiment, would anything bad happen if a magic wand was waved over a neighborhood, and each individual house now supplied power to the grid in the same amount it would usually be consuming it? A whole neighborhood with normal electric flow, just reversed. Are there components of the grid that are unable to deal with reverse power in the exact same quantity and load distribution as forward power?
  - idiotsecant 4y ago
    Distribution systems are designed for unidirectional power flow from the transmission system at the top to individual users at the bottom. If you start doing things like reversing power flow and exporting power through already very heavily loaded distribution transformers you create bottlenecks, stability issues, and safety issues that were not originally designed around. If you expect users to be importing and exporting power from their residence you need to have automated protection that can disengage those residences from the grid at a minimum, and probably a lot more that I am not an expert on. My day job is designing control systems for renewable generation and as a result I have some exposure to transmission level and generator bus level protection schemes and they can be quite complex!
    - mwint 4y ago
      This is what I'm looking for, thanks! Any pointers on good places to read about these issues?
- mlyle 4y ago
  > but a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment. We already have grid-tie solar, and beyond that, grid-tie batteries at homes and them doing work to support frequency and voltage of the grid in many locations. Having an EV do it isn't any harder. The big challenges are figuring out how to compensate/bill for all this.

If we all had electric cars, those batteries would BE the grid.

by smm11 4y ago

If we all had electric cars, those batteries would BE the grid.

This isn't really true without massive distribution system redesign. It could be true for individual homes with transfer switches that disconnect them from the grid if that's what you mean, but a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment.

bombcar 4y ago
Even the first part (powerwall setup basically) could be useful. But it’s best when coupled with reduced usage where possible - if we get to a point where the majority of residential electrical usage is cars we’ll be doing pretty well.
mwint 4y ago
What substantial investment is required, at the hardware level?
- jandrese 4y ago
  A big inverter would be the first thing you need.
  - mwint 4y ago
    Right, I guess my question is if anything that needs to be done to the grid itself (outside of individual homes). You're going to have a big inverter anyway to power just your house from your solar panels, batteries, whatever.
    - falcolas 4y ago
      You need transmission lines capable of handling the current. Too much current through local transmission lines can cause drooping lines, which touch trees (i.e. grounding that line), which shuts those transmission lines down automatically. It's something like this that helped cause that big power outage in Chicago. Power couldn't flow through the big transmission lines (they got shut down for a couple of reasons), so it flowed through the local lines towards the demand, and then those were shut down because they hit trees. Ironically, this electrical current issue is also a problem for charging electric cars at stations, since one fast charger at 20% utilization can draw 2-3x more power than the store whose power grid it's attached to.
      - mwint 4y ago
        This is the original claim I'm asking about: "a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment." Wouldn't it be less current, in general? If your neighborhood gets 20% of its power from solar panels on your neighbor's houses, it seems clear that power lines inbound to the neighborhood would need to carry 20% less load, and lines inside your neighborhood would also carry somewhat less on average (your power consumption has not changed, and presumably your neighbor is powering his house off his own power before exporting the rest to you). I understand there are probably some topological hot spots, like if one dude has a 1MW solar installation in his backyard, but as a general principle I don't understand what big upgrades need to be done to the grid to support P2P.
        falcolas 4y ago
        Honestly, I'm not qualified to answer this specific usecase. But here's a few numbers to chew on: An average home consumes just a little over 1kW on average, and its connection to the grid will be built to that tolerance. Solar generation is generally peaks around 5kW for an average house installation; individual panels measure between 250 and 400 watts. An electric car's battery pack can, pretty easily, provide in excess of 100kW (based on their charging rates, and the fact that batteries charge more slowly than they can discharge - about 4.6x slower for Tesla battery packs).
        mwint 4y ago
        Huh, this is interesting to me. My house has 400A service (or at least that's the main panel breaker size). 400A at 240V is somewhere in the ballpark of 80kW possible draw. Does something bad happen if I actually use my home's full service for an extended period? I understand bad things would happen if everyone on my block did. As a thought experiment, would anything bad happen if a magic wand was waved over a neighborhood, and each individual house now supplied power to the grid in the same amount it would usually be consuming it? A whole neighborhood with normal electric flow, just reversed. Are there components of the grid that are unable to deal with reverse power in the exact same quantity and load distribution as forward power?
- idiotsecant 4y ago
  Distribution systems are designed for unidirectional power flow from the transmission system at the top to individual users at the bottom. If you start doing things like reversing power flow and exporting power through already very heavily loaded distribution transformers you create bottlenecks, stability issues, and safety issues that were not originally designed around. If you expect users to be importing and exporting power from their residence you need to have automated protection that can disengage those residences from the grid at a minimum, and probably a lot more that I am not an expert on. My day job is designing control systems for renewable generation and as a result I have some exposure to transmission level and generator bus level protection schemes and they can be quite complex!
  - mwint 4y ago
    This is what I'm looking for, thanks! Any pointers on good places to read about these issues?
mlyle 4y ago
> but a peer-to-peer setup where your house is powering your neighbor down the street doesn't work without some substantial investment. We already have grid-tie solar, and beyond that, grid-tie batteries at homes and them doing work to support frequency and voltage of the grid in many locations. Having an EV do it isn't any harder. The big challenges are figuring out how to compensate/bill for all this.