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Comment by egberts1 | Hacker News Reader

This should bode well for electric vehicles if an electrical outage were to occur.

Electrical outages take out gas stations, too.

We have an electric car, and we survived a 3 day outage caused by a wind storm a few weeks ago just fine. That's because we started with a full battery, just like we do every morning.

OTOH, many people with gas cars had empty tanks and had to endure 4+ hour lines at the few gas stations that had electricity and hadn't yet run out of gas.

I suppose you'd have been fine if your gas car had a full tank too?

It's harder to ensure a full tank of gas every day than to ensure a full EV charge every day.

Yes it takes more effort to ensure you stop by a gas station on the way home than it is to plug in at night, but still fairly minimal.

My father instilled in to me to never let my tank get below half, in case there are emergencies and I still follow that practice.

Two points:

1. When I switched to an EV as a daily driver, I realized I had underestimated how much time and hassle I was spending at gas stations. When it's been engrained in your psyche as being just part of life, we don't really realize how nasty gas stations are compared to just plugging something in.

2. Another good reason to never let your tank get below half: If you get "bad" gas, you'll only have half a tank of it, diluted with presumably "good" gas. Rare occurrence nowadays, but a benefit nonetheless.

A buddy of mine from the Air Force (I wasn't in AF, he was) told me they never fill above half-full unless you are going long distances. Apparently something to do with MPGs and the weight of fuel.

I never listed to him, but to this day he still only fills his car up half way for better gas mileage. I'm sure it matters if you have a 200 gallon tank, but 60 pounds of fuel will not make a difference in a vehicle that weighs 3000 pounds. Adding a single passenger is going to be more than double that.

I can see it for something with a very large fuel capacity, that doesn't often get driven around motorpool/base unless deployed.

Agreed - it was dumb of him to adopt that in his civvy life, but I couldn't convince him otherwise.

The EPA says that for every 100 pounds of weight carried around by a car, fuel efficiency drops by around 1%.

So if you avoid carrying around 8 gallons of fuel everywhere, you could increase fuel efficiency by around half a percent.

Not a lot of savings.

https://www.fueleconomy.gov/feg/driveHabits.jsp

This is where EVs don’t work so well: you are carrying the entire weight of the battery no matter how much it is charged. Not so important for cars, but for electric planes it is significant.

Regenerative braking negates much of the weight penalty in cars.

You don’t have to. I have 15 gallons of ethanol-free gas I get from the airfield (unleaded) in the garage for filling up the mower, generators, the snowblower, etc. It usually takes about six months to get through it all. I fill up a jug when it goes empty, etc., etc. If it really becomes a problem, I’ve got plenty of gas to get to where someplace has working gas pumps.

Sure, but I think the point is that EV owners are topping off everyday vs ICE owners don't fill up until they need to (maybe weekly or if it runs low, certainly not daily).

I am sure many EV owners also woke to mostly empty batteries because they didn't charge them that night and other ICE car owners who just happened to fill up the night before. Not sure what advantage you see for electric here. Both need to be "fueled" somehow.

In fact you can fill an ICE car in a few minutes so you can have many cars per single pump. EVs require long periods of time at a dedicated plug that many apartment owners, renters, and others don't have access to.

Could you imagine the lines at a charging station when it takes 30 minutes best case per vehicle?

As long as the sun rises, my house has power and my EVs charge. The sun is more reliable than petroleum supply infrastructure. It’s Mr Fusion 8 light minutes away.

I don’t have batteries yet because I have favorable net metering and my utility is natural gas fired (which pairs better with distributed renewable generation vs coal or nuclear), but if/when their power quality declines, my system is future proof to accept battery storage.

Most people have grid tied systems that disconnect when the grid is down :/

Most US grids are reliable, and more rooftop solar would bolster generation when it’s needed: hot days when the sun is shining and cooling loads are straining generation.

"The sun is more reliable [in my locale]"

Fixed it for you.

Germany has 60GW of solar generation capacity (with plans to expand that to 200GW by 2030) at its relatively high latitude. When it’s hot, the sun is shining. When the sun is shining, you use it for cooling. You even can use it for heating in the winters with heat pumps.

There are very few inhabited places on Earth where the sun is unreliable enough that today's solar is uneconomical. My parents live in upstate NY—hardly a place known for its high rate of sunny days—and since they installed their rooftop solar, they've said it generally provides enough power for the house unless it's actually covered in snow.

Would you spell it out for us? What exactly happens when the grid fails at your site? Overnight, obviously you have no power. Then "the sun rises" but surely if there's any load, it must get above a certain point in the sky before it can run your house and charge your EVs, especially in the winter. And same thing in the afternoon, there must be a point where the sun is shining but too low in the sky and the load cannot be sustained- what exactly happens then?

(also, no clouds where you are?)

Assume there is no utility power. The sun must rise high enough on the horizon to energize the system (I haven’t done the math to know what the altitude/sky position is yet, I’ll report back). Once energized, the system will operate as a microgrid and attempt to maintain frequency and voltage if there are clouds until the sun sets and falls below the horizon. Some loads are more tolerant than others. The EVs of course will charge whenever there is power, and the hot water heater and pool pump will operate just fine only when power is present. Only the AC unit is fickle about power quality.

[removed strawman comment for being unnecessarily combative] When my utility is operational, I’m not just offsetting my consumption but also pushing back clean power into the grid for others locally to consume (which reduces the natural gas generation required of my utility) and while the failure mode isn’t perfect when the grid is down, it’s better than having no power at all (until battery storage costs decline).

Edit: https://pv-magazine-usa.com/2021/10/25/enphase-launches-micr...

Not a strawman (I don't think? not sure what you meant by this..), just very curious. You have a setup that is in between useless when grid is down, and fully self-sufficient. Seems possibly very practical to me, but I haven't heard of it before.

It is a very uncommon setup, I've met installers that don't know about it. The new generation of microinverters enable this setup more easily, so it should become more common.

My EV is plugged in whenever it is in the garage. I'm sure most other EV owners have the same habit.

Pretty much every EV owner that can plugs in every night.

People just do not get how much different an EV is vs gas. Never having to go to a gas station is just SO nice once you never have to do it.

If you arrive home by 6, it normally takes 4 hours to top off. It should be done by 10pm. What time did the grid go down again?

The car charges at a rate of 48 km/hr on a 32 amp garage circuit. So on an average day it recharges in less than an hour. However, it's programmed to charge at the cheap overnight rates, so it doesn't start charging until midnight.

Therefore we were out ~30km of range when the power went out. 370km rather than 400km is still "full" in my opinion, though.

> That's because we started with a full battery, just like we do every morning.

Which - if we're being honest - is a bit of a privilege. Most folks with cars do not have a dedicated garage, nor a parking space with an outlet.

> That's because we started with a full battery, just like we do every morning.

You're assuming the electric outage happened after you filled up your car with electricity.

It could also be possible that the electric outage happened after you filled up at the gas station and the gas station ran out of power.

Actually, it did happen later in the day, so it was down 30km, an average days usage. So we had 370km of range rather than 400km. That's still full, essentially.

My point is that the only time the car drops below 300km of battery life remaining is when we're on a road trip, so maybe once a month.

Whereas our gasoline car will have somewhere between 1/8 and full on a random day.

Rather then some strange comment about electric vehicles and your apparent distaste because they depend on a electric grid (as opposed to gas, which is also a commodity and has the same issues, transportation being one of them). Why not look at how do we fix this? Maybe we need to offer more incentives for solar panels or fix the grids by providing money to the states?

Unless you routinely run your electric car down to a low battery, it's not a problem. 300+ miles per charge is normal now. Most people top up every night. It would take a power outage that lasted longer than a week for my car to run out of juice with my normal driving habits.

By the way, if the power is out, gas station pumps don't normally work either.

They could have on-site generators for the gas pumps for such an emergency.

It's not like they don't have a tank of gas nearby .....

One of the inherent weaknesses of external combustion engine-powered vehicles.

Should be fine if the vehicle is kept charged. Ford F-150s can power most homes for a few days on a single charge [0]

[0] https://www.thedrive.com/tech/40695/the-electric-ford-f-150-...

Yes, it should. EVs make great standby power sources.

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.

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.

What substantial investment is required, at the hardware level?

A big inverter would be the first thing you need.

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.

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.

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.

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).

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?

You would have to spread that load across multiple circuits in your house to avoid tripping breakers/blowing fuses. You might not have enough capacity to absorb all 400A if the original installer oversized the main breaker to allow for additional capacity later.

The bad thing is you would get a huge power bill at the end of the month.

I think the thing I'd be worried about first is the transformers. Would they handle that much power flowing in reverse without overheating/catching on fire? They're already one of the weaker parts of our system; they don't handle overcurrents well (they're largely what folks are concerned would fail due to a solar flare).

The second thing would be all the sensors attached to the grid. Would they identify a sudden and dramatic change in flow as a fault, and throw their switches?

Also, where would that supply of energy flow? If there's not enough of a sink for that electricity, what happens to the generators? If the sink is outside the local area, what would happen to those transmission lines?

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!

This is what I'm looking for, thanks! Any pointers on good places to read about these issues?

> 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.

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