The Potential of Electric Vehicle Energy Storage: Exploring V2G

[shivajikobardan]

How can electric vehicle deliver energy to grid?

This is the one of the few block diagrams that I could see in google. Do you have better one or can you explain this one? If I am not wrong. V2G is basically giving excess charge in your EV back to the grid.

 

[Baluncore]

How can electric vehicle deliver energy to grid?

First you must charge the EV battery when the price is low. If you do not use the vehicle, you can sell that energy back to the grid later, at a higher price. You must then charge the EV battery again when the price cycle falls.

 

[Rive]

In theory, the price on the grid changes through the day, depending on the demand/surplus. Supposed to be low at night and high at peak periods (mid-day and early night).
So if you charge your car at night and deliver some of the charge back during peak periods, you can both earn some money and mitigate the demand (and surplus) on the grid.

In practice, it's still unclear whether this could work. You can charge at night, sure: but the midday peak is more about PV these days: when PV goes down and most battery would be needed you are on your way back home: at the early night peak you just arrived home with low battery.

 

[artis]

How can electric vehicle deliver energy to grid?View attachment 300746
This is the one of the few block diagrams that I could see in google. Do you have better one or can you explain this one? If I am not wrong. V2G is basically giving excess charge in your EV back to the grid.

Many renewable energy source output DC directly (like solar panels) which is then put into grid inverters that use semiconductor switches and low pass filtering to output AC that can be attached/supplied to grid or directly used in household systems.
An electric vehicle has a battery and batteries are DC storage sources, that means that the EV battery is in electrical terms just another energy source that much like a solar panel can be fed back into grid via an inverter.
In this regard it is almost identical to a solar panel, just that it doesn't produce the energy it has it simply stores it. Much like a pumped storage hydro plant just with different physics behind it.

The common idea is that once EV's will be plenty the total battery capacity will be large and if enough users driven by profit used their EV's to supply peak demand then the EV car fleet would function as another grid stabilizer, aka energy storage system, similarly to how pumped hydro and hydrogen fuel cells work.

But unlike pumped hydro and other industrial storage solutions, EV's are private and scattered around and I'm not sure whether one will be able to get an accountable and systematic charge/discharge ratio out of this.

Another downside is that every charge/discharge cycle shortens the battery life, and using your EV car to stabilize grid is not a straightforward "green" or viable solution to my mind.
Battery's cost a lot and use a lot of toxic chemicals that are not easy to produce and take great care to recycle so I think this is a two way road.

 

[anorlunda]

Can you do it? Yes.
Is it a good idea? Possibly, but probably not.

However, there are ideas about assisting the grid frequency control by varying demand. For example, if a million EVs are charging and if the grid frequency is low, the EVs could pause charging for 2-3 seconds until the grid recovers. If frequency goes high, add additional loads. It is called demand side response.

How would they know when to do that? Everyone can measure the local frequency of power at the plug. Because the grid is synchronized, it is (in the steady state) the same as the frequency everywhere else.

However, there is little to be gained by demand side frequency regulation because the grid already has inexpensive ways of doing that. So the economic value of another method is low.

But if you leave the grid out of the question, and ask about using an EV to provide emergency backup power to a house for 1-3 hours (when safely isolated from the grid), then it is closer to reality. It might compete with a UPS or with a gasoline generator. The EV could serve the same function as a "Powerwall" battery system.

 

[artis]

The EV could serve the same function as a "Powerwall" battery system.

I'm not sure but I would suspect Tesla is using the same cells both in their "powerwall" as well as their EV's.

On the other hand so far it seems Tesla is voiding warranty if they find out that you have been powering any outside appliance from the car
https://electrek.co/2021/02/23/tesl...wer-your-home-with-electric-car-battery-pack/

I'm not exactly sure how they would find that out , maybe there is a data logger inside the car power electronics that registers power consumption and can see current flowing steadily out instead of in.
I don't think a tesla car has real time power management communication over the air with a Tesla dealership like a household with smart meter that works by PLC or through RF via mobile network of WIFI.

 

[anorlunda]

I don't think a tesla car has real time power management communication over the air with a Tesla dealership like a household with smart meter that works by PLC or through RF via mobile network of WIFI.

You missed my point about power frequency. No remote communications are needed. Just sense the frequency at the charging station. If < 59.99 then stop charging. If > 60.01 then start charging. Voila grid frequency regulation.

 

[Baluncore]

Voila grid frequency regulation.

What incentive is there for the EV owner to stabilise the grid ?

For all we know, the EV manufacturer is already trading 10% of your battery capacity to their advantage and hiding the details.

 

[anorlunda]

What incentive is there for the EV owner to stabilise the grid ?

It's mostly a scam, but it is real in certain places.

So-called aggregators write contracts with tens of thousands of retail customers to collectively provide some service to the grid. But they exaggerate how much the grid is willing to pay, and underestimate the fees the aggregator collects. I could name the states where legislation explicitly encourages that, but that would become political because it is viewed as "empowering the people" (no pun intended.)

Compare it to class action lawsuits where the lawyer gets $10 million and "victims" get $0.39 each. I actually got a check for $0.39 from a lawsuit called "bought milk."

 

[artis]

You missed my point about power frequency. No remote communications are needed. Just sense the frequency at the charging station. If < 59.99 then stop charging. If > 60.01 then start charging. Voila grid frequency regulation.

I think this time you might have misunderstood what I said, I agree about the grid frequency monitoring , sure everyone can do it at their home socket, I was referring to how Tesla might check whether one has used his tesla car to use the battery as a power source for whatever goal. In order for them to void any warranty they need to know one has "outsourced" the battery power and I suspect the car has some sort of a logger inside the power management that charges the battery etc.

 

[sophiecentaur]

But they exaggerate how much the grid is willing to pay,

Something that really annoys me is that governments set up this sort of scheme (the Feed In Tarif etc), to look good, and any 'profit' that the users get comes from the majority of other consumers having to pay more for their energy.
This is grossly unfair because, to take part in such schemes, you need to be a home owner, situated in the right place with room to instal equipment. Needless to say, the underprivileged miss out once again.

 

[anorlunda]

Something that really annoys me is that governments set up this sort of scheme (the Feed In Tarif etc), to look good, and any 'profit' that the users get comes from the majority of other consumers having to pay more for their energy.

Electric rates have always been 90% politics. Government gets extraordinary influence because the utilities are regulated monopolies (or worse, state-owned). But in history, before regulated monopolies, wild speculators and dishonest holding companies made it even worse for the consumers.

 

[profbuxton]

I find this EV charge and the resell to the grid rather strange. I note that power suppliers are now wanting to disable solar fed into the grid since it reduces their income etc.
Also there is a problem that solar feed in that it has to be at a suffieient voltage to actually feed power in and with so many being connected there is a problem with differing voltage levels etc.
Surely this would also be a problem with the large possible numbers of EV all trying to feed into a grid. Isnt there a possibility that say, one street of EVs are feeding into the grid while another street is being charged by the former(depending on voltage drops in the distribution system. so we end up with little charge/discharge loops in the system.