Electric Cars and the Grid

Much has been made the past few years about various faults and failures in utilities across the country. Of course there’s the famous incident from Texas a few years back, and now California is facing grid problems during an unusually hot September.

Many people are pointing out the irony that the same week California is struggling with power, they announced a ban on gas powered cars. That ban is, of course, years away, but that doesn’t stop plenty of pundits from making their comments.

Something else I’ve found interesting lately is the Tesla virtual power plant. The TL;DR is that plenty of Power Wall owners (people who have a big freaking battery in their house) are getting paid to send some of that power back to the grid when needed. $2 per kWh is crazy.

People have this overly simplified model in their mind that the whole country is connected with a big wire, and you can add or remove power as needed. That’s sort of how it works, but as you could expect, it’s way more complicated than that.

One of the biggest issues is that wires can’t carry an unlimited amount of electricity. Electricity moving through wires creates heat. More electricity means more heat. So even when power grids are interconnected, where they are interconnected matters a whole lot, and how much power can go through that interconnection is limited by the size of the interconnection. If you need a lot of power in Los Angeles, having a bunch of extra hydro-electric power from Oregon available might not do you any good if there’s not enough carrying capacity from point-A to point-B.

The other issue is that it takes time to add capacity to the grid. It doesn’t take any time at all for me to use that capacity. The dryer and air-conditioner are the two largest consumers of electricity in my house. I can turn both on at the same time with hardly a thought. If everyone does at approximately the same time (such as coming home from work), people working at power plants have to fire up the generators and that takes time.

Add this up and when people use electricity is almost as important as how much is used. Air-conditioning is hard because it is extremely power hungry, and most of the demand is going to follow the sun heating the earth up, so a lot of people will want to use a lot of power, all at the same time. Or, a lot of people get home from work to a house that has been heated by the sun all day, turn their air-conditioning on, and now the grid has a problem. (this is also a problem because most people are getting home from work about the same time that solar power is waning as the sun is starting to go down)

There are a lot of schemes to help with this. Our utility provider Xcel is introducing time of use pricing, which uses meters that track when you use power as well as how much, and you get charged more money when you use power when the grid is already close to max-use. This is an economic incentive to encourage you to dry your clothes at off-peak times when the grid is less maxed out.

The other thing that you could do that’s really interesting to me is to do some thermal shifting. If you normally set your A/C to cool to 75º at 6pm, you could set it to cool to 70º at like 2pm. You might use more electricity in total this way, but you’re potentially shifting your power use to when the grid has less demand and more renewable power available (because of solar). Your house can “store” that cool air until you get home, and when you arrive at home from work, the house is already cool and comfortable and you don’t use any grid capacity at 6pm when the grid is at its max.

But what’s really interesting to me is the Tesla Virtual Power Plant when it comes to electric cars. As far as I can see, the Tesla power plant only uses the stationary Power Walls installed in customer’s homes. But what major battery capacity has been coming online the past 10 years or so? Electric cars. Many of these electric cars have 300+ miles range. What if on the days that you don’t need to go somewhere 300 miles away, you could trade some of what’s stored in your batteries for a free payout to help the grid out?

What if you could help your neighbors out, power their A/C, and make like $30-$60 in the process? And the only thing you’d be giving up is 150 miles range for the evening?

I assume the Tesla Virtual Power Plant only covers Power Walls because using cars to power the grid requires a bit of extra hardware. The higher trim F-150 Lightnings actually advertise being able to connect the truck to your house and using it as a battery backup for “2-3 days” for most average sized houses. That’s crazy! And there’s no reason you couldn’t do the same thing with that equipment that Power Wall owners are doing for a “virtual power plant”.

This has a lot of really interesting properties. Decentralizing power means the grid doesn’t have to be upgraded as much, which saves a ton of money. It also means you can operate fewer generators and use those generators within their optimal usage range. But grids are also not perfectly uniform either. Maybe one neighborhood has more people working from home, or more solar, or an electrical problem. You can imagine the grid putting some of those distributed batteries to work to help even out differences and make the grid more intelligent.

If we’re going to put very large batteries in most garages over the course of the next 20 years, there’s a lot of interesting things you can do with that, if you have the right hardware. But honestly, even if you can’t feed power from the cars back to the grid, there’s still a lot that makes sense. Let your car charge when the grid has excess capacity (such as late at night when most people are asleep and not running much A/C, or in the middle of the day when solar is at its peak) and don’t charge your car when you need to run A/C.

I guess I just don’t see the humor in what the pundits are saying. Electric cars don’t automatically mean the end of the California grid, or anybody’s grid. In fact, they could be a really helpful tool in making the grid a lot more stable and resilient.