4 ms·

Fun fact, the effective charging power of a gas pump is ~6MW (20MW thermal). Good luck getting a 1MW utility feed.

BobLaw 4y ago
That would be a silly way to approach it. You would be paying $40k+ per month in just demand charges some places. A much better idea is to have battery packs you can charge at constant slower rates and feed the charging station at higher burst rates. Tesla and Electrify America already do this. https://electrek.co/2021/12/02/electrify-america-deployed-tesla-powerpacks-over-140-charging-stations/ https://electrek.co/2021/12/02/electrify-america-deployed-te... https://driveteslacanada.ca/semi/tesla-megacharger-installation-giga-nevada-wraps-up-construction/ https://driveteslacanada.ca/semi/tesla-megacharger-installat...
- krab 4y ago
  Or swappable batteries if we standardize on a few sizes. You can then charge those slowly. However that brings problems with quality control - a worn battery costs less than the new one. Maybe a model where the customer doesn't own the battery?
  - ccozan 4y ago
    Renault does that with Zoe, if I am not mistaken
    - gambiting 4y ago
      They did for a while but at least here UK there is no battery leasing anymore with Zoe. You just buy the whole car outright.
wbsss4412 4y ago
Gasoline is incredibly energy dense, as you point out, it’s very unlikely that batteries will approach it anytime soon. Fortunately/unfortunately, so much of that energy in ICE cars is wasted as heat, so the effective gap to make EVs competitive is much smaller.
snovv_crash 4y ago
Well, given that an ICE is ~30% efficient compared to an electric motor at ~95%, comparable charge rates would be 2MW. Still a mind boggling number.
- galenlynch 4y ago
  I think that was already accounted for (parent mentioned 20 MW thermal)
krab 4y ago
Gas station could store the energy (supercapacitors?) to average out the utility load. According to https://www.energy.gov/sites/prod/files/piprod/documents/Session_D_Miller_rev.pdf https://www.energy.gov/sites/prod/files/piprod/documents/Ses... the technology seems to exist.
- robocat 4y ago
  Perhaps. If a station has a lengthy peak period of use, then perhaps the batteries would need to be huge. The number of discharge cycles required for the batteries also matters, as does the conversion losses (charge, discharge). Replacing batteries after end-of-life could be a significant expense. I am guessing the savings from off-peak charging cover that expense given that some charging stations have storage batteries, but at a guess the cost implies ≈10% systemic ecological cost on top of the power charged to the vehicle.
  - krab 4y ago
    I don't know much about the technology - the lack of larger installations is a red flag. Anyway, I tried to calculate with the numbers from the document above with the following assumptions: 10 charging stations, 6 cars per hour per station, 100 kWh per car. That makes 6 MW peak consumption for the whole "gas" station. A capacitor storing 6 MWh (60 cars served, no incoming electricity) would need to have 120 m³ of storage. Google says that a gas station storage size is between 30 000 and 40 000 gallons (110 000 - 150 000 l) so that seems comparable. Another way to look at it - 200 m³ of storage is a building of 10 x 10 x 2 m, without the need to manipulate flammable liquids. Not sure about the investment costs (the doc says 5 000 cycles but no cost estimate), how long the peaks are and other aspects of running a gas station. Still, it seems the order of magnitude is about right.

That would be a silly way to approach it. You would be paying $40k+ per month in just demand charges some places. A much better idea is to have battery packs you can charge at constant slower rates and feed the charging station at higher burst rates. Tesla and Electrify America already do this. https://electrek.co/2021/12/02/electrify-america-deployed-tesla-powerpacks-over-140-charging-stations/ https://electrek.co/2021/12/02/electrify-america-deployed-te... https://driveteslacanada.ca/semi/tesla-megacharger-installation-giga-nevada-wraps-up-construction/ https://driveteslacanada.ca/semi/tesla-megacharger-installat...

krab 4y ago
Or swappable batteries if we standardize on a few sizes. You can then charge those slowly. However that brings problems with quality control - a worn battery costs less than the new one. Maybe a model where the customer doesn't own the battery?
- ccozan 4y ago
  Renault does that with Zoe, if I am not mistaken
  - gambiting 4y ago
    They did for a while but at least here UK there is no battery leasing anymore with Zoe. You just buy the whole car outright.

wbsss4412 4y ago

Gasoline is incredibly energy dense, as you point out, it’s very unlikely that batteries will approach it anytime soon. Fortunately/unfortunately, so much of that energy in ICE cars is wasted as heat, so the effective gap to make EVs competitive is much smaller.

snovv_crash 4y ago

Well, given that an ICE is ~30% efficient compared to an electric motor at ~95%, comparable charge rates would be 2MW. Still a mind boggling number.

galenlynch 4y ago
I think that was already accounted for (parent mentioned 20 MW thermal)

krab 4y ago

Gas station could store the energy (supercapacitors?) to average out the utility load. According to https://www.energy.gov/sites/prod/files/piprod/documents/Session_D_Miller_rev.pdf https://www.energy.gov/sites/prod/files/piprod/documents/Ses... the technology seems to exist.

robocat 4y ago
Perhaps. If a station has a lengthy peak period of use, then perhaps the batteries would need to be huge. The number of discharge cycles required for the batteries also matters, as does the conversion losses (charge, discharge). Replacing batteries after end-of-life could be a significant expense. I am guessing the savings from off-peak charging cover that expense given that some charging stations have storage batteries, but at a guess the cost implies ≈10% systemic ecological cost on top of the power charged to the vehicle.
- krab 4y ago
  I don't know much about the technology - the lack of larger installations is a red flag. Anyway, I tried to calculate with the numbers from the document above with the following assumptions: 10 charging stations, 6 cars per hour per station, 100 kWh per car. That makes 6 MW peak consumption for the whole "gas" station. A capacitor storing 6 MWh (60 cars served, no incoming electricity) would need to have 120 m³ of storage. Google says that a gas station storage size is between 30 000 and 40 000 gallons (110 000 - 150 000 l) so that seems comparable. Another way to look at it - 200 m³ of storage is a building of 10 x 10 x 2 m, without the need to manipulate flammable liquids. Not sure about the investment costs (the doc says 5 000 cycles but no cost estimate), how long the peaks are and other aspects of running a gas station. Still, it seems the order of magnitude is about right.