V2G technical Query

rogon said:

Is there not an inverter in an EV and why is this not available to connect the stored battery to the grid ?

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After suitable communication between the car and the controller in the chargepoint/V2G unit, yes the raw battery voltage appears on terminals of the socket, and you then need an inverter similar but not identical to a solar inverter of the same power to connect it to the grid.

So if you look at the price of a solar inverter, add a substantial extra cost for the CHAdeMO or CCS protocol controller, contactors and connector (the CHAdeMO connectors in particular are not cheap), you get the notional price of one of these units. Add then an allowance for the fact that these are currently only built in low volumes and you get the price you see now (actually, £8k-£9k is a pretty good price as things stand today).

Personally, I'm not at all convinced that full V2G is a good idea. You can get most of the benefit with very much smaller cost by simply managing EV charging speeds/times. In such a scheme, you would input by some mechanism the amount of charge you need and when, and the system would charge at time and rate to suit grid balance - maybe not charging at all some nights when you have enough for your commute the next day, maybe charging more than you need on other nights when there happens to be excess. This also side-steps issues of battery wear, and accounting for losses in the charge/discharge cycle (if you do real V2G, you are getting less out of the battery than you put in and need to account for that in the billing).

Thanks for the replies.(and forgive any ignorance of the technical difficulty, bit of blue sky thinking)

arg said:

So if you look at the price of a solar inverter, add a substantial extra cost for the CHAdeMO or CCS protocol controller, contactors and connector (the CHAdeMO connectors in particular are not cheap), you get the notional price of one of these units. Add then an allowance for the fact that these are currently only built in low volumes and you get the price you see now (actually, £8k-£9k is a pretty good price as things stand today).

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Option 1.
If you have or more likely are going to invest in solar panels (of the correct output say 360v dc to match the leafs battery) you already have the sunk cost of a suitable inverter ?
Yes CHAdeMO connectors are pricey ($1000 to $2000) but surely in this application type the cost can be cut as only using DC cable/pins etc...can get plug for $120 here
ev charger plug Electric car Type2 IEC 62196 IEC standard CCS type 2 charging plug-in Chargers & Service Equipment from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group

The cost of CCS/CHAdeMO protocol controller I can not get a fix on for such an application ??

The principle is the hybrid inverter system using solar and battery, but in this case direct use of the EV battery. e.g.
https://www.cleanenergyreviews.info/blog/2014/8/14/what-is-hybrid-solar

Alternatively there is the more complex option as set out in the following paper.
Vehicle-Solar-Grid Integration: Concept and Construction - IEEE Journals & Magazine



Option 2
In virtually all EV's the DC of the motive battery is inverted on board the vehicle to supply AC to the permeant magnet AC drive motor. (ignore and other inverter for the 12 V battery).
Could this inverter not be reconfigured to supply in Europe a 220/240V AC supply to either the AC motor or alternatively back to the grid.... and more so why not ?
I am guessing the AC is chopped for speed control but surely the electronics could be configured for either function. (reason to remove the need for a 2nd pricy external inverter).
Why not look to redesign the EV power electronics from scratch with this in mind ?


Why do this at all...i.e why V2G or V2X
The reason for the individual would be a combination of an additional revenue stream and possibly environmental considerations. (rebrand the car as the mobile power hub which travels with you and your energy needs. Similar to the smart phone which is much more than a phone.... )
Aggregation of the EV would enable revenue from ancillary services, capacity and trading (in a balancing market). From a study by National Grid UK V2G can earn £600 (US$980) per year for a 3 kW system to in the region of £8,000 (US$13,000) per year for a 50 kW three phase installation. This compares to Demand side management which would provide a modest annual financial return to the individual vehicle owner of approximately £50 (similar to the "managing EV charging speeds/times" that Arg alluded to).
Ricardo, National Grid study explores market potential for grid-balancing services for plug-in vehicles


From the grid perspective with the increase in renewables there is an imminent need for frequency support.
I live in Ireland which is a small grid approx. 7GW peak demand, currently 3.5GW of installed wind, with plans to increase this penetration to 6GW's. But this can only be done if the instability of wind/solar can be balanced. This is where batteries could step in, and why duplicate battery installation with wither industrial scale or "powerwall" solutions, when EV's can fulfill both the energy and transport needs.

Finally lets look at a utopian future where EV's represent 10% of road vehicles ?
In this scenario for Ireland that means 200,000 cars. Say 50% are grid connected V2G at any time at 10KW inverters?. That's 1GW of additional power over wind available to the grid (and generally more local to power demand).
Further push out to 50% of EV's this would mean more than 5GW's of power. This would eliminate the need for most thermal power plant !!!!

P.S. I do get the fact that as the number of V2G vehicles are connected the revenue to the individual would reduce proportionately but with mass roll out the cost of the technology would also drop and governments might be prepared to support V2G as replacement generation. Lastly as more V2G is installed the frequency and quantity of drawdown from each individual EV is less negating the concerns about battery degradation due to V2G cycling ????


Forgive me if I am a dreamer !!!