V2H and V2G

JKenH

michaels said:

JKenH said:p

I was prompted by a recent comment on relatively low monetary returns to the householder and that made me wonder about the round trip efficiency of V2G. There are a number of articles around but this summary from Wikipedia covers a range of results. 

Most modern battery electric vehicles use lithium-ion cells that can achieve round-trip efficiency greater than 90%.[24] The efficiency of the battery depends on factors like charge rate, charge state, battery state of health, and temperature.[25][26]

The majority of losses, however, are in system components other than the battery. Power electronics, such as inverters, typically dominate overall losses.[27] A study found overall round-trip efficiency for V2G system in the range of 53% to 62%'.[28] Another study reports an efficiency of about 70%.[29]The overall efficiency however depends on several factors and can vary widely.[27]

https://en.wikipedia.org/wiki/Vehicle-to-grid

Can anyone on a V2G trial advise me on what the returns look like after the round trip losses (suggested here as ranging from 30-47% ) are factored in. As an example if we take a mid range figure for losses of (say) 40% and you import 10 units at 10p, by the time you have completed export you have lost 4 units so to break even you need to be paid 16.7p per unit for the 6 units you actually manage to return to the grid. Does the electricity provider make an allowance for the losses in what you are paid for export? 

This of course also impacts on self consumption so if the car battery has charged up overnight at say 10p a unit then if you are cooking your tea when the unit is exporting you will effectively be paying 16.7p a unit. 

If the losses were 30% then you would only need 14.3p to break even. 

Any feedback from users would be welcome.

Pretty sure the round trip efficiency (reported by the charger) for our unit is about 80% and that is probably an underestimate of the actual charging efficiency as having the charger on and connected increases vampire loses in the car.  If the charger was smart enough to turn on only when charging or discharging then the efficiency would probably be about 90%+

Thanks.

I find I lose about 15% charging AC to DC with my Leaf. (The difference between what LeafSpy reports added to the battery and what my Zappi reports as having put in). The V2G is doing the AC/DC conversion rather than the car so might be more efficient but then it has to convert back again from DC to AC. I can see a 30% loss as being realistic. I think from the range of results different chargers and car combinations will produce different results but as the vast majority (all?) of the trials in the UK are with the Leaf.

At 80% efficiency do you make anything out of it?

michaels

JKenH said:

michaels said:

JKenH said:p

I was prompted by a recent comment on relatively low monetary returns to the householder and that made me wonder about the round trip efficiency of V2G. There are a number of articles around but this summary from Wikipedia covers a range of results. 

Most modern battery electric vehicles use lithium-ion cells that can achieve round-trip efficiency greater than 90%.[24] The efficiency of the battery depends on factors like charge rate, charge state, battery state of health, and temperature.[25][26]

The majority of losses, however, are in system components other than the battery. Power electronics, such as inverters, typically dominate overall losses.[27] A study found overall round-trip efficiency for V2G system in the range of 53% to 62%'.[28] Another study reports an efficiency of about 70%.[29]The overall efficiency however depends on several factors and can vary widely.[27]

https://en.wikipedia.org/wiki/Vehicle-to-grid

Can anyone on a V2G trial advise me on what the returns look like after the round trip losses (suggested here as ranging from 30-47% ) are factored in. As an example if we take a mid range figure for losses of (say) 40% and you import 10 units at 10p, by the time you have completed export you have lost 4 units so to break even you need to be paid 16.7p per unit for the 6 units you actually manage to return to the grid. Does the electricity provider make an allowance for the losses in what you are paid for export? 

This of course also impacts on self consumption so if the car battery has charged up overnight at say 10p a unit then if you are cooking your tea when the unit is exporting you will effectively be paying 16.7p a unit. 

If the losses were 30% then you would only need 14.3p to break even. 

Any feedback from users would be welcome.

Pretty sure the round trip efficiency (reported by the charger) for our unit is about 80% and that is probably an underestimate of the actual charging efficiency as having the charger on and connected increases vampire loses in the car.  If the charger was smart enough to turn on only when charging or discharging then the efficiency would probably be about 90%+

Thanks.

I find I lose about 15% charging AC to DC with my Leaf. (The difference between what LeafSpy reports added to the battery and what my Zappi reports as having put in). The V2G is doing the AC/DC conversion rather than the car so might be more efficient but then it has to convert back again from DC to AC. I can see a 30% loss as being realistic. I think from the range of results different chargers and car combinations will produce different results but as the vast majority (all?) of the trials in the UK are with the Leaf.

At 80% efficiency do you make anything out of it?

As I say import and export are as reported by the charger, no idea if that is into battery and out of battery or form grid and to house/grid or even if it is true!

The trial I am on gives a fixed 26p for all export as read by the smart meter so for us PV as well as from the car, year one when the import was only 13p we did nicely, year 2 the import is 16p and there is a lot less profit (we are notoriously high energy users).  In order to get the export we are locked to OVO and their import price fixes were about 10-20% higher than the market leaders when we fixed for each year.  With the solar export included we make a profit on the deal and hopefully at the end of trial we will have a functional V2H unit (current cost 5k) that could for example let us arbitrage the Octopus time of day tariffs.

As an aside when we started paying 26p for export looked like a big loss ovo, more recent agile export prices mean they are getting it cheap, especially as our W facing solar generates quite a lot after 4pm.

QrizB

michaels said:

As an aside when we started paying 26p for export looked like a big loss ovo, more recent agile export prices mean they are getting it cheap, especially as our W facing solar generates quite a lot after 4pm.

Recent Agile export rates have even made my 2012-vintage FIT seem quite cheap!

JKenH

FALSE STARTS: THE STORY OF VEHICLE-TO-GRID POWER

A 2001 experiment proved electric cars could feed the grid. So why hasn’t V2G taken off?
https://spectrum.ieee.org/v2g

There are some useful links at the bottom of the article for those interested in V2G
Edit: apologies for the bold formatting which only appears after posting 

70sbudgie

Interesting article - though it needs a "long read" warning. I haven't got to the end yet...