In europe (At least) the company Easee makes AC chargeres that are WiFi / 4G enabled. In Sweden (And Norway) you can connect them to a service like Tibber, which allows you to automatically enable/disable charging with the electricity price, assuming you have a spot price electricity contract.

https://tibber.com/en/product/easee

Easee chargers also have a pretty bitching API, so you can also make your own automations using e.g. home assistant or what have you.

This tells me that Li-Ion batteries are far from the ideal medium for grid storage.

If one were to build a "facility" to hold short term load, that's likely what they'd use. They just can't be used in cars because they're incredibly volatile and don't hold a charge for a long period of time.

Edit: to answer my own question, they look pretty good [1]. Significantly lower storage density than batteries (roughly 50Wh/L versus 420Wh/L for Li-ion), but still dense enough for this to be workable at grid level. The linked presentation proposes converting decommissioned power plants into grid-level capacitor storage facilities, since the transmission switchyards are often intact. Furthermore, all the technology is available today, and when built, capacitors require almost zero maintenance.

[1]: https://www.energy.gov/sites/prod/files/piprod/documents/Ses...

For technical reasons, thats because the 'spinning reserve' - which is momentum of every synchronous motor and generator across the nation - already adequately handles this.

Also, large generation stations are required to have a 'load line' which damps high frequency oscillations. The load line can best be described as 'whenever the grid frequency starts slowing down, generators must put more energy in automatically'. Things like wind and solar typically don't have the ability to do that.

For human reasons, it's because electricity markets tend to be minute by minute at most.

For all those reasons, I don't think you'll make any money with capacitor energy storage banks (not to be confused with capacitors for grid scale power factor correction, which can be profitable).

The problem is that capacitors (assuming you mean super and ultra capacitors) don't have much capacity compared to batteries, so their cost per MWH of storage is high even if their cost per MW is low.

If it turns out people don't need all the cycles out their car battery then there's value in capturing that, but new large scale installations will move to other technologies over the next decade or two.

That's on the low end, like if you're fully charging/discharging the battery frequently.

Li-ion are good for frequency stabilisation: initial response times of the order of ten milliseconds, run times up to several tens of minutes maybe.

For longer durations, flow batteries and other chemistries are probably better. They win because of very good cycle life and calendar life (20_000 cycles, 50 years) but tend to take longer to start up.

Flow batteries include vanadium redox, zinc-bromine, iron-saltwater (being piloted). Other chemistries: sodium-sulfur (NaS, developed by NGK and sold by BASF in Europe/NA), carbon polymer based (PolyJoule), and a great number of experimental types.

There are also thermal batteries and compressed air energy storage, and pumped hydro.

Pumped hydro is by far the biggest form of grid storage today and is not as limited by geography or cost as one might think. It can be used in the "hours to months" range of energy delivery durations.

This functionality is already there.

> So each kwh cycled into and out of the battery costs 8 cents.

This is quite much. If you add other infra overhead, feeding power back into the grid is not going to produce much revenue for the individual unless the selling price is maybe 20 cents above the price when charging.

On the other hand, something that MAY make more sense, is if the car battery can be used to provide power to the owner's own house during short price peaks. This might allow some savings even in stable grids, but the killer app would be in grids that have rolling blackouts during high demand periods.

And even for grids where blackouts are infrequent, if your car can serve as large UPS for your house (combined with a large capacitor to keep the power stable), such functionality in the charger may be worth the cost of the hardware for many people. (Bringing the number of units up and hence the cost per unit down over time.)

Still, though, for grid stability it is probably much better to use dedicated batteries as part of the grid itself than to use car batteries.

https://www.tesla.com/sites/default/files/downloads/tesla-ne...

> Warranty Limitations

> This New Vehicle Limited Warranty does not cover any vehicle damage or malfunction directly or indirectly caused by, due to or resulting from normal wear or deterioration, abuse, misuse, negligence, accident, improper maintenance, operation, storage or transport, including, but not limited to, any of the following:

> ...

> Using the vehicle as a stationary power source

https://www.theverge.com/2022/9/12/23349971/nissan-leaf-bidi...

> Ideal for companies with fleet vehicles, the Fermata Energy Demand Charge Management application, along with the FE-15 charger, continuously monitors a building’s electrical loads, and may draw on the Nissan LEAF’s energy to provide power to the building during more expensive high-demand periods. In states with utility demand response programs, bi-directional-enabled Nissan LEAF vehicles (MY2013 and later) are able to safely send energy stored in the battery to the grid during peak energy demand times, such as in summer months.”

> The downsides to V2G tech are that it must degrade your battery (to some extent or another) to be discharging and charging more frequently, and it leaves your battery with less charge at times when you may wish you hadn’t discharged at all. Some people will always take that tradeoff, though, and it is great to simply have an option on the table for consumers who really want V2G tech. Stay tuned and watch this space.

> The article on the Fermata Energy/Nissan announcement is not quite correct. It’s for commercial use only – not residential. The Nissan-approved FE-15 bidirectional charger is available for commercial and government fleet owners. https://www.fermataenergy.com/fe15-sales

---

The other part is that this is grid supplemental charging where there is already a steady main current to be matched. If you are using it to power an island (home or similar disconnected from the grid), it is a different situation and would require completely disconnecting from the grid with safety cutouts to make sure that when the grid comes back on that the systems are not out of phase and damage equipment.

Grid storage is a different (and arguably easier) problem than home backup in the case of a blackout.

There needs to be a specialized charging (and discharging) setup in the garage. People who charge using a regular extension cord without installing additional hardware will not be able to do V2H or V2G.

The charging setup needs to be able to cut off power from the grid to the home. This involves a more extensive modification to the home's electrical setup. Note that there's a different culture with housing in Japan.

https://en.wikipedia.org/wiki/Housing_in_Japan

> An unusual feature of Japanese housing is that houses are presumed to have a limited lifespan, and are generally torn down and rebuilt after a few decades, generally twenty years for wooden buildings and thirty years for concrete buildings – see regulations for details. Refurbishing properties, rather than rebuilding them, is a relatively uncommon practice in Japan, though its prevalence is increasing, indicating that attitudes towards older houses may be changing.

> ...

> The taxable value of a house is controlled by its building material. Wooden houses are considered to have a lifespan of twenty years, and concrete ones to have a lifespan of thirty years, and the assessed price depreciates each year contrary to housing markets in other nations.

This means that basically every 20 years the house is rebuilt and you've got more recent electrical setup. If you're building/buying a new house in Japan and had an EV, the incremental addition to the cost of building the house isn't significant.

The house I am living in was built before electricity was available, had gas pipes to each room for lighting (though not in use), and had functioning knob and tube wiring as recently as 2010.

I do look at a home generator (and the corresponding changes to the electrical wiring needed) - but that's not a small change. If I was getting an EV, and considering V2H as an add on, it would likely not be something I'd do.

Simple delayed charging with a timer is common, yes. The grid interactivity part? Much less so.

The few V1G pilot programs out there have been very encouraging.

>better to use dedicated batteries as part of the grid itself than to use car batteries

Fortunately, it's not an either/or. We can better optimize the total system cost by doing both.

Why? Every kwh we can store using car batteries is a kwh of dedicated grid storage we don't need to purchase. It can increase the speed we add new storage on the grid. It is a more efficient use of lithium and other precious metals. This "smart charge" or "flex EV" is the type of incentive utility companies can push, and something that would decrease the amount of capital investments they need to make.

I can imagine a few counter arguments for why dedicated batteries are better, but nothing that convinces me. This claim that dedicated batteries are better than car batteries has little support in your comment and I would like to understand why you believe this claim.

Then there are the efficiency downsides. Storage "at the edge" means more transmission infrastructure is needed, on average, compared to more centralized storage. Also, grid batteries can be optimized for number of charge cycles, not for charge amount per unit weight. Finally, servicing individual cars is probably more expensive than replacing batteries in a storage facility.

And this is before going into inconvenience aspects, such as risking that your car doesn't have a near-full charge when you need to go on an unexpected trip, or the hazzle of handling the payment agreements, etc, just for a couple of dollars per day in potential revenue.

In computer terms, it's kind of running mining software on your computer GPU at night. For those especially interested, it may be fun, but for the average consumer, probably not worth bothering with.

So you can forget about your car (or even most solar inverters) to work during blackouts unless a couple of things are present:

- a automatic grid disconnection switch (aka a transfer switch)

- special firmware to allow the inverter to operate in 'off grid' mode

Both Xantrex and Victron have inverters that can do this but they are not normally deployed for such installations and they wouldn't know what to do with your car battery (voltage much higher than the ones that they require, typically 48V max).

Growatt has some off-grid units too, but those still won't satisfy the impedance requirements of your cars inverter (the grid is 'too small' so it will fluctuate too much due to high impedance).

Personally having an EV and a Victron inverter with batteries and same vendor car charger I HATE the fact I can't even adapt charging amps depending on p.v. available power in AC charging.

With HA and a bunch of scripts you can actually get quite far in automating all this, but when the grid fails everything will shut down.

I'd love to see these babies become more easily (and cheaper!) to source:

https://en.wikipedia.org/wiki/Lithium-titanate_battery

The energy density isn't super but for stationary applications that's fine. 6K+ cycles, fast charging, what's not to like?

Beside modern water heater nothing else is available on sale and even to simply "trigger switches by software" means pay not marginal prices for IoT devices like Shelly ones, who have simply too much stuff, starting from a webui, to justify their costs.

Even the simple, decades old modbus, is BADLY spoken just by few devices, MQTT even less...

I can definitely recommend the 'Shelly' stuff, it's been absolutely problem free and super reliable, they have a nice range of sensors and controllers.

Some actually have happened, like minisplit with optional remote control module to be installed easily lifting the front top and some hot water heater, but such controls are still very rare and damn limiting...

A small example, I cite it because it's not on sale anymore (there is a slightly updated version, with a different name) my home hot water is made with a Daikin/Rotex M2O EKHHP it feature a "renewable integration" witch consist in two dry contacts who allow just to tell the machine:

- do not run

- run as you want

- run full power (heat pump, if possible PLUS classic resistive stick)

- run for an hour with heat pump only, then full power.

Those who design such logic have NO IDEA about domestic p.v. self consumption. Why the hell such logic instead of:

- do not run, except antifreeze

- do run full power (heat pump and resistance)

- do run ONLY in heat pump mode if possible

- do run ONLY with resistance

My actual "solution" is:

- knowing the outside temperature in HA, so being able to decide if I can run the heat pump or not

- decide to trigger the "run for an hour with heat pump only, then full power", switching to "do not run", switch again to "run for an hour with heat pump only, then full power"

just to limit the load to ~600-800W of the heat pump, BUT for instance sometimes I can use more, like the 2kW resistive stick BUT NOT 2kW+600-800W and for that I have no option. Sure it does not change my life, but it's absurd. Why not give such simple controls?

My VMC is even nicer: it have a range of ModBUS controls, with some registers badly enough documented I can't understand what they mean, some not documented but understandable through observation manually command the machine via it's own keyboard/display.

I've decided to buy an absurdly expensive EV domestic charger from the same vendor of my main home inverter, a Victron EVC. It claim formally to be integrated. Actually in p.v. mode all it do is staring a charge at 6A if there is at least them available from p.v. of course if there is room to more amps no way to change them, it seems to be hardcoded. Only option use the manual mode driven via ModBUS from Home Assistant. At that point I do not even understand the dams logic, the only thing better than a far cheaper charger is that it's three-phase, I have a 3-phase 36kVA domestic contract so if I need a quicker charge I can run around 7*3kW from grid. But that's all. Other domestic chargers for EVs are not better and still with absurdly high price for a simple metered socket with some extras on a mini-board computer, something who can cost around 30€...

Your generator is not allowed to feed a non-functioning grid for safety reasons. It can't distinguish between a blackout and a utility worker disconnecting to service something. Your inverter would kill that unsuspecting person by surprising them with a generator on the side they're touching.

That might just inevitably conclude in "OK, I guess others are willing to ask a lower price than I am, so I won't be in a position to participate in a V2G scheme."

That seems more reasonable for the owner, but no utility co would pay it.

If you can really treat the whole cost of the battery as X cents per charge cycle, disregarding the lifetime of the car/battery, this won't work at grid scale. Someone else will build a storage facility that just charges and discharges batteries, and they will outcompete rational EV owners, because they will have economies of scale and battery banks designed for this use. It only makes sense if the EV owner can somehow get charge capacity "for free" - eg the car will be EOL after 1000 charges but the battery lasts 2000 - he should sell the extra 1000. Or alternatively if getting 8c now is better than getting 1 charge in several years time (plausible if interest rates, energy futures prices etc are right).

However, this could be wrong. The same logic says rooftop solar can't exist without special subsidies, and a lot of people disagree with me there.

> It only makes sense if the EV owner can somehow get charge capacity "for free"

The EV owner has the power electronics 'for free' - ie. they have almost infinite lifespan, and just a capital cost.

Additionally, the variations of energy prices on the grid are really wide. There might be $100k/MWh for 5 minutes per year. It isn't worth a static operator paying the capital cost for the batteries (which also degrade with time) to setup for 5 minutes use per year. But it does make sense for the EV owner to do so, because his marginal cost is tiny.

This depends where you live and the size/efficiency of your rooftop setup, right?

If you completely neglect the installation part, sure. Utility-scale solar farms have massive efficiencies of scale on purchasing panels and on labor-related overhead.

It's not that clear cut, basically.

I think what the EV model allows is for private car owners to essentially sell a part of their car back in increments, if for some reason their driving behavior changes and they don't need to drive as much as they used to.

If someone builds that storage facility to do it commercially then great.

> rooftop solar can't exist without special subsidies

Yet it does

https://www.seia.org/initiatives/solar-investment-tax-credit...

> The solar Investment Tax Credit (ITC) is one of the most important federal policy mechanisms to support the growth of solar energy in the United States. Since the ITC was enacted in 2006, the U.S. solar industry has grown by more than 200x - creating hundreds of thousands of jobs and investing billions of dollars in the U.S. economy in the process.

The Section 48 commercial credit can be applied to both customer-sited commercial solar systems and large-scale utility solar farms. The rate is effectively at 30% until Treasury issues guidance on new wage and apprenticeship standards. Two months later, the rate will be at 6%, with an additional 24% (for a total of 30%) available for meeting these new labor standards.

So utility-scale solar farms can get the same 30% credit as rooftop solar. They're both tax-advantaged compared to (e.g.) building a new gas plant, but the rooftop credit isn't any higher, at least not on the federal level. Self-consumption from rooftop solar may avoid other taxes, like sales tax, but in many states there is no sales tax on residential electricity to begin with.

It's part of the "Inflation Reduction Act of 2022" (and at a higher rate than before): https://www.solar.com/learn/inflation-reduction-act/

Rooftop solar is heavily subsidized almost everywhere it’s popular. Rooftop solar isn’t a good deal for utilities or their non-rooftop-solar customers.

I say this as someone who lived off the grid on solar for years; encouraging rooftop solar may have kickstarted the learning curve for the solar panel industry, and as such may have been pretty good social policy.

But it definitely owes its existence to subsidies.

These days grid scale solar makes lots of sense, rooftop solar still doesn’t (and the subsidies are now harder to defend).

Plug in the numbers. A charge cycle is probably around 200 miles (not even optimistic). That means that 1000 charge cycles is 200000 miles. That's roughly the lifetime of a car. However, I have heard anecdotes that EVs should last longer, due to a simpler transmission, so this may be a little up in the air.

I already have to own a car for short trips most days and an occasional long trip. And when I'm not going on a long trip I have a lot of extra battery capacity that I can rent to the grid at extremely low (additional) cost to me.

A dedicated battery storage facility on the other hand has to justify the entire price of the battery.

A real deployed algorithm would estimate the "degradation cost curve" over the entire DoD, and stop charging when total (fully-considered) costs exceed revenue.

That milestone has been hit in some places Australia already.

If the system still depends on distribution, someone has to pay for it.

It may be that rooftop solar users will be asked to pay more for that distribution than they think is reasonable.

I’m sure not excited about my grid operator proposing a $50/month minimum for electricity, it makes my panels seem worthless. But there is logic; I was being subsidized by net metering. And in future I may have to pay a cost closer to the true cost of access to the stability of the grid.

The market they can buy and sell this capacity is called an “aggregator”, and they can earn more money on this then selling just power.

Seems quite different from “your household is an autonomous actor and you get almost all of the arbitrage value of reducing peak consumption”, which would be a radically different system (but ignores who’s going to pay for distribution, which is getting closer and closer to being the dominant cost of the grid).

Yeah, I think that's far more likely. I can also see the possibility of a grid-mandated signal for "please, stop charging for five minutes, we're at capacity".

https://news.ycombinator.com/item?id=34518188

If your life is so chaotic that this doesn't work for some reason, don't turn on V1G

After those 2000 cycles is the battery completely dead, or does it still work but at a reduced capacity?

If it does still work at a reduced capacity, does continued use reduce the capacity to 0 after a while, or does is plateau at some fixed reduced capacity and stop further degrading?

This study is great but a energy storage comparison study that calculates total cost would tell us much more. Wouldn't be surprised if the Department of Energy already has or is [1]

[1] They do a lot of these studies already. i.e. https://iea.blob.core.windows.net/assets/ae17da3d-e8a5-4163-...

I think people worry a lot about market access when it doesn’t make sense. The market operators cannot handle the settlement and operations overhead of microscale power generators. They are not offering reliable commitments, and the metering just doesn’t exist at the small scale. Your local PG&E equivalent isn’t equipped to operate an efficient power market, I don’t think.

For context - a “small” scale solar power plant is in the 10s of MWs, which >1000x bigger then a car battery at full output. Utility-scale storage is also in the same ballpark.

Since prices a per day, announced the day before, the algorithm is not that complicated.

Also, if I install solar panels, the electricity just goes back into the grid, and I would get money for it. For the car it would be the same, just reverse the electricity into the grid. So it is mostly just the connecting the day-ahead prices, plus the cars and wall chargers returning electricity of-course.