By Sherry Listgarten
What can you do with your EV battery?Uploaded: Jan 23, 2022
I have heard from many of you who have EVs and would like to know when you will be able to use your car to power your house during a blackout, charge your laptop at a campground, or even contribute some power to the grid when there is a flex alert. This blog post is a short overview of where we are on those “vehicle-to-X” tasks. The topic is complicated -- a recent working group identified over 1000 use-cases for vehicle-grid integration which it “narrowed down” to 320. Plus the technology is quickly evolving. So this post will mostly touch on the surface and I may have some follow-ons as I learn more.
For those of you who like acronyms (anyone??), this subject is a gold mine. For the purpose of this blog post, I’ll stick with four: V1G, V2G, V2L, and V2H. (1) These stand for different ways that your EV battery can be deployed for uses beyond driving. I’m going to try to explain what these are and the current status, though I would love to hear from those of you who know more in the comments!
V1G: Charging your EV, ideally when there’s plenty of power
The simplest way to use your EV to help the grid is by adjusting when you charge it, for example to avoid peak periods (4-9pm) and to charge less on “flex alert” days. The number “1” in the V1G acronym refers to the uni-directional flow of charge from the grid to the EV. (The rest stands for “Vehicle to Grid”.) Anyone can do this (basically, charge at a different time), but power providers and third parties have been experimenting with how to better reward and aggregate this kind of “flexible demand” and make it more responsive to grid needs.
Today many of you can program your EVs to avoid charging during certain periods (e.g., evenings). But you won’t always know when the grid is stressed. Another option is to get a grid-aware charger (e.g., JuiceBox) that will charge your car at times that are best for the grid while respecting your charging needs. With JuiceBox, you can specify that you need your EV charged at a certain time, and you can specify if you have time-of-use rates that you would like it to respect. The charger company, Enel X, earns some money by providing this aggregated flexible demand to the grid, and in some locations EV owners can earn money as well.
Silicon Valley Clean Energy is promoting GridShift, which works with some vehicles and chargers. Peninsula Clean Energy is conducting managed pilots. After the recent summer power crunches, California is actively looking for ways to reduce demand during flex alerts and other peaks, and the state is funding and seeking to quickly develop and expand these managed charging programs.
Some of the issues they are trying to figure out include:
- What is the right way to incentivize EV owners to participate? How do you determine the baseline behavior to compare against, and is a special charger or meter needed?
- How “big” do these aggregated services need to be in order to register with the grid?
- How often and when will they be called upon to respond?
- If customers are already on time-of-use rates that discourage 4-9pm charging, are there other times/occasions when flexible demand would be helpful?
If you are interested in flexible charging, contact your local power provider to see what programs are available. This is an easy and inexpensive way to reduce our power peaks, increase reliability, and save money. In my view all power providers should be encouraging it. I hope the majority of chargers are participating in a few years’ time.
V2L: Charging a small load (L) from your EV
While “V1” refers to applications that charge the EV, “V2” refers to applications in which the EV is used to charge something else. That is, the EV is exporting power rather than importing it. In the case of “V2L”, the EV is used to directly power some load (“L”). This is a fancy way of saying that your EV has plugs.
A number of EVs are coming out with pretty powerful outlets. The Ford F-150 Lightning has up to 11 outlets with a total of 9.6 kW of power. The 240-volt outlet in the truck bed can even charge another EV! The Hyundai Ioniq 5 has an outlet on the outside of the car that can provide up to 1.9 kW. Kia, Toyota, and others have announced models with this feature as well. This seems pretty useful, with the primary downside being that if it’s overused it could drain or even degrade the battery.
Most EVs today do not support this capability. But if you know what you are doing, or if you trust videos on the internet made by preppers and frostbitten Texans, you can install an inverter like this, or even a kit, to convert the high-voltage direct current from your EV battery to lower-voltage alternating current that your appliances can use. If you are successful, you can plug in a coffee maker when you are car camping, or plug in a refrigerator during a power outage. I hope that more EVs start incorporating this feature so there’s less need to jerry-rig it.
V2H: Charging your home (H) from your EV
It is much simpler to charge a few appliances with your EV (e.g., via outlets or an add-on inverter) than it is to power a building with it. Not only is more power needed, but the inverter needs to be integrated with your electric panel, and your house needs a switch that will automatically disconnect your house from the grid when the power goes out. (You don’t want the power from your house feeding back onto the grid and potentially harming linemen.) This means permits and inspections and expense. If you think about it, this kind of setup is very similar to installing a home battery (albeit one on wheels).
The Ford F-150 Lightning supports this capability, and it is a big selling point for many buyers. But the installation is non-trivial. Ford provides its own "charging station" that needs to be professionally installed (they are partnering with SunRun for that), and it requires a 320-amp service.
Almost no cars are equipped with bidirectional chargers capable of powering a home. However, a few companies are developing external chargers that can do the job. These “DC chargers” convert the grid’s AC current to DC so they can deliver DC charge directly to the EV for faster charging. They can also convert large amounts of DC charge from the vehicle into the AC needed by the home. It is arguably easier to do this conversion outside of the car rather than inside the car since on-vehicle components have many constraints. (2) The Wallbox Quasar is one such product, and the dcbel Home Energy Station is another. Unfortunately they only work with cars with CHAdeMO connectors right now (e.g., Nissan Leaf and Mitsubishi Outlander PHEV). The CCS standard adopted by most other EVs in the US does now support bi-directional charging and some pilot projects are beginning to explore this. (3)
PG&E in particular is interested in seeing how much V2H can mitigate the impacts of its high-fire-danger power-shutoff (PSPS) events. The state is very supportive, in part because the generators that many households rely on are very polluting. A $7.5M PG&E pilot for residences will try to evolve the V2H technology while also learning how to deploy it most effectively.
If you have an EV and your home is in a PSPS area, ask your utility if there is a V2H pilot that you can participate in. Only a few types of vehicles are likely to be supported. If you are not eligible, my guess is it will be a few years before the market (e.g., vehicles and chargers and installers) has evolved to support the ability for a typical EV to power a home during outages.
V2G: Powering the grid (G) with your EV
Finally, it should be possible to send power from your EV battery onto the grid in times of need, in return for cold hard cash. This requires not only the infrastructure described above, but also some ability for the state’s electricity market to recognize this new type of generation, incorporate it, and compensate it.
If your EV is configured to export electricity, it could perform like a solar roof in some ways, providing power to your home or the grid, and it would need to be metered and wired in a similar way. The CPUC is in fact looking into extending the solar Net Metering rate structure to work with EV charging.
One question that people are trying to answer is how more frequent charging and discharging would impact the health of an EV battery. There is no clear answer yet since it depends on several factors. (4) I expect it is fine to respond to flex alerts and outages by exporting power from your EV battery, but it might be more problematic to send power to the grid every evening at 7pm.
Only 25% of the use cases that the working group looked at were residential. Other interesting cases involve fleets of school buses and transit buses, big drayage trucks that do short set routes between ports and warehouses, local delivery trucks, and airport shuttles. If done properly, V2G can reduce the costs of maintaining these electric fleets while also saving the grid money. In that sense, V2G can accelerate electrification by making it more affordable.
But getting it right, or even just making it work, involves coordination between the grid, the power providers, and vehicle manufacturers. With so many interested parties (1000+ use cases!) and the state’s very inclusive process, not to mention the technical and market complexity, the V2G discussions have been slow going. I think we will largely be in the “pilot” phase for a few more years.
I look forward to your comments and questions on this topic, and maybe I’ll do a more focused follow-on once I learn more.
Notes and References
1. There is also V2B (“Vehicle to Building”), V2X (“Vehicle to Anything”) and V2V (“Vehicle to Vehicle”, aka charging one EV from another EV).
2. I like this explanation of how onboard and offboard chargers compare.
3. PG&E's description of a pilot program they are planning says: “For vehicles that use the Combined Charging Standard (CCS) for DC charging, there are two existing pathways to enable bidirectional charging. One is through the DIN 70121 specification, and one is through the ISO 15118-20 specification. The DIN 70121 specification has been finalized and is therefore, currently more mature in functionality than the ISO 15118- 20 specification, which is targeted to be formalized sometime at the beginning of 2022.”
4. You can find a few references here and here and here and here (this last only if you have IEEE access, which I don’t!).
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