On-grid domestic battery storage

JKenH

mmmmikey wrote: »

Too embarassed to admit what I'm paying for PowerVault but you can find the details here!


https://www.edfenergy.com/for-home/battery-storage


The reason I went for this expensive option is that anything over 4kWh is wasted on me due to low consumption and the PowerVault has hardware and software support for frequency response grid services, which I'm gambling on being a significant factor in improving future economics and payback. Also really impressed with the company.

I note from the link that EDF can charge and discharge the battery at their discretion. Do you have to pay for the energy EDF put into the battery and do they pay you for what they take out?

zeupater

JKenH wrote: »

I note from the link that EDF can charge and discharge the battery at their discretion. Do you have to pay for the energy EDF put into the battery and do they pay you for what they take out?

Hi

... and just as importantly, not just the metered ins & outs, but the round trip losses too ??

HTH
Z

mmmmikey

JKenH wrote: »

I note from the link that EDF can charge and discharge the battery at their discretion. Do you have to pay for the energy EDF put into the battery and do they pay you for what they take out?

The simple answer is yes, you pay (your normal provider, which doesn't have to be EDF) for what goes in to the battery, and no you don't get paid on a kWh basis for what goes out (but EDF do pay you a flat rate for allowing them to use your battery).

Having said that, it's a bit more complex than first appears. The natural expectation is that they'll be putting energy in overnight when it's cheap and taking it out early evening when it's expensive, but it doesn't work like that. They're actually using your battery to even out very short term blips minute by minute. In more detail....

1. You're not actually contracting with EDF for import and export per se, you're contracting with them to use your battery to manage demand (bear with me on this). You have three separate contracts. In addition to your normal energy and FIT contracts you have an additonal grid services contract with EDF, allowing them to manage demand by using your battery to participate in the Firm Frequency Response (FFR) market. The normal energy and FIT contracts can be with anyone, you're not tied to EDF. Any payments in relation to energy import and export go to/come from your regular providers, nothing to do with EDF. So how do EDF make money.....?

2. When the load on the grid increases suddenly, the frequency decreases slightly (as the various generators bog down and start spinning slower before the regulators kick in) and conversely when the load suddenly decreases the frequency increases. (You can see this changing on the gridwatch website). This is more to do with volatility than natural daily demand variation - they know there's going to be high demand at 17:00 so the gas fired stations are already up and running.

3. National Grid is required to maintain the frequency within tolerances, and to do this it puts FFR contracts out to tender. Big commercial users (refrigeration plants, aluminium smelters and such like) bid and agree to monitor the frequency and to rapdily increase or decrease their demand to bring the frequency back into range - i.e. if the frequency is low they'll agree to quickly switch something off and if it's high they'll switch something on. National Grid pay them to do this - independently of any energy charges.

4. In a similar way battery storage with appropriate hardware can very quickly respond to frequency changes, charging from the grid or discharging to the grid and managing demand accordingly. EDF can contract with domestic users and aggregate batteries, and then bid for FFR contracts, which is where they make their money (again, independently of any energy charges).

5. There are different types of FFR contract depending on how quickly you can respond to frequency changes and how long you can maintain that response. Batteries can respond very quickly so EDF are bidding for valuable quick response but low duration contracts, so typically they'll only be using the battery for a few minutes here and there (or so the story goes!).

6. The financial implications of this are (a) EDF pay you £1500ish up front (for a 4kWh battery) to allow them to do this for 10 years (so £150 per year - you can opt out at any time by giving them the money back pro-rata) (b) if your battery starts charging from the grid to bring down the frequency, this results in additional import and you pay your regular supplier (whoever that is, you can still choose whoever you want). This isn't lost, you can still use what you've bought, but you've eaten up some of your battery capacity, so there's a possible opportunity cost depending on how you're using your battery (c) if your battery starts to export to the grid to increase the frequency then whatever you export is lost.

This is too new for there to be any data yet, so it really is a gamble as to whether the £150 per year is enough to compensate you for the opportunity cost of lost storage and what you export. According to my rough and ready guesstimates (based on the probable state of my battery and demand at different times of day) I expect to be quids in, but it really would be foolish to bank on that.

I've gone for this option for future-proofing, in that it gives me a system with frequency response capability. As the market for domestic FFR matures I can swicth to a better contract if one becomes available. My instinct is that the EDF offering is probably quite generous because the cost to them is peanuts and they'll not want to kill the market before it develops by exploiting early adopters, but this is just speculation.

To give you an idea of how new this is - they need 1Mwh of capacity to start bidding and they're not there yet. PowerVault have plenty of orders (hence the installation delay) and they should be there imminently (next few months). So this isn't just at the early adopter stage, it really is bleeding edge.

Note that I keep saying EDF, this is actually some kind of joint venture between EDF and PowerVault and I'm not sure who does what bit. The grid services contract is with EDF but the £1500 up front payment is made to PowerVault and seen as a discount off the cost of the system - as per the website.

A caveat to end with. I'm making it sound like I know what I'm talking about but may not I have researched this extensively and discussed it with PowerVault so it should be about right, but please don't bet your pension on it!

Hope this is of some interest, Mike

p.s. happy to try again and answer questions if this doesn't make sense. If it does make sense it will lead to questions about iBoost and other things, but I've left that bit out for now.....

EDIT - saw your post about round trip losses after I'd written this, will think about that a bit before responding

ASavvyBuyer

Would it be worth having a separate thread for V2H & V2G news for those that are interested in it?

Personally, I would rather use a small % of an EV battery, rather than buy a home battery, to reduce import, providing the cost of an V2H/G inverter was reasonable.

mmmmikey

zeupater wrote: »

Hi

... and just as importantly, not just the metered ins & outs, but the round trip losses too ??

HTH
Z

First, a comment on metering. All the additional metering needed is internal to the PowerVault and accessed by EDF via an internet connection that the contract stipulates you must have. Access to this data is necessary for operation of the contract between EDF and National Grid. This data has no bearing on what EDF pay you - you get a flat rate of £1500 for 10 years paid up front. As I understand it, this data is not currently available to you, as the consumer, via the PowerVault portal.

As far as round trip losses are concerned, in the same way that you lose a bit by charging your battery with E7 overnight and using it during the day, you do so here with anything that is put in as part of the grid services contract. This does erode the benefit because of the need to import 1.2kWh to use 1.0kWh after it's been through the battery (obviously you can use your own figures here).

zeupater

mmmmikey wrote: »

First, a comment on metering. All the additional metering needed is internal to the PowerVault and accessed by EDF via an internet connection that the contract stipulates you must have. Access to this data is necessary for operation of the contract between EDF and National Grid. This data has no bearing on what EDF pay you - you get a flat rate of £1500 for 10 years paid up front. As I understand it, this data is not currently available to you, as the consumer, via the PowerVault portal.

As far as round trip losses are concerned, in the same way that you lose a bit by charging your battery with E7 overnight and using it during the day, you do so here with anything that is put in as part of the grid services contract. This does erode the benefit because of the need to import 1.2kWh to use 1.0kWh after it's been through the battery (obviously you can use your own figures here).

Hi

In a system where there's an annual payment for operating within the scheme, I'd certainly be extremely reticent to sign a contract without there being quite explicit usage limitation clauses .... I fully understand what the scheme is attempting to achieve, but the balance of capital outlay, risk & uncertainty seems to be heavily bourne by the scheme membership as opposed to the operator, with the benefit flow being out of balance in the opposite direction, totally in the hands of the scheme operator as opposed to the owner ... not quite the kind of cost/benefit analysis I'd be looking to be paying above market rates (£/kWh installed) for capital equipment on, even after applying a theoretical 'on-paper' discount!.

Additionally, there's the calculation of depreciation (/write-off) lost opportunity costs, which must be considered as the cycle count benefiting the scheme operator has no proportional financial benefit to the scheme member ...

What needs to be recognised is that in operating within such a scheme, a few minutes at a time at a fixed discharge power will (on average) impact on a 4kWh system more than a larger system ... it's not inconceivable to predict that the additional cycles will shorten the useful battery life to the owner by in the region of 25% on a small capacity system, for example - 4kWh storage with 3kW discharge on an average 4x 5min calls/day likely adds ~25% to the number of annual cycles.

Having solar PV in place brings further complexity ... Depending on the call timing, the remaining state of charge may result in additional energy imports to replace stored on-site generation, effectively provided for 'free' - and extending this further, couldn't the timing of evening energy replacement also have a direct effect on the following day's opening state of charge and therefore reduce the storage system's ability to soak-up excess generation the next day and therefore the effectiveness & performance of the combined battery/PV system? ....

As mentioned earlier, there are lots of variables which can have a negative impact on the scheme member which don't apply to the scheme operator, all of which would be subjected to careful & detailed analysis and the application of fair usage limitation clauses in a business environment before raising a purchase order, so surely it would be appropriate for consumers to expect & require the same detail & contract protections?

Regarding efficiencies ... the scheme moves from ...
charge > store > ... to ... charge > store > discharge > charge > store > ... adding two stages of efficiency loss. If the first stage charging was from PV at well below the maximum charge rate and the second stage charging was closer to the full nominal rate then the effect of relative battery resistance based on rate of charge rate per cell needs consideration ... it all depends on the control settings, but the same likely applies to discharge too ...

A quick sanity exercise would suggest that operating such a scheme with a typical PV system & a 4kWh battery with 1kWh of daily scheme supply could add 'up to' ~£80/year (17p/kWh as used recently) to the electricity bill, to which additional lifetime asset depreciation (based on 10 year scheme membership) of around ~£700 (25% of £700/kWh) could be considered reasonable ... doesn't that represent a potential total 10 year cost to the member (at current costs!) of £1500, for a 'one off' benefit of £1500 (amortised over 10 years!) .... which seems to be a remarkable coincidence! ... who'd have thought it?

Conspiracy theory, well maybe not, but even those without Faraday cages & tin-foil hats would be able to follow the logic & recognise the conclusion! ...


HTH
Z

joefizz

mmmmikey wrote: »

So how do EDF make money.....?

On this point, essentially they dont have to, they just dont have to lose as much as going out of sync or running up more expensive diesel battery sets would cost.
When I worked in a manufacturing environment the factory would have a dirty great diesel generator power plant just sitting there in case of power failure. Now at times of peak load a message would go out for us to reduce our usage and the generator would fire up and help manage the grid. I think most large manufacturers were part of the load balancing scheme.


In recent years anyone that could replace the diesel set with wind has done so and with the decline in energy consumption across the board in manufacturing (and loss of manufacturing in general) theres less and less of these balancing units.
Plus in my previous points about moving away to a more distributed network it sort of makes sense for them to utilise whats already out there and if enough homes sign up they dont have to build new cabinets near the substations to do it with everything that involves.


It will be interesting to see where this goes as its a very cheap option for the provider and as has been mentioned a lot of the residuals are passed on to the householder. Its the gig economy applied to power generation ;-)
Like free apps probably the most valuable thing to the power companies is the actual usage data rather than the energy itself, thats just a mechanism for getting the data.
Similarly with solaredge and solarman, I dont think they do free monitoring out of the kindness of their own hearts.


No coincidence that there are a fair few fenced in diesel generator set sites going up around the uk, its not to cover events like the beast from the east, more to cover load balancing that the newer technologies are increasingly likely to introduce.
We had a big power cut here a few years ago and whilst the initial strike was a line failure at one of the main power stations, it tripped out another station because of the imbalanced load and took time to get the load back to a state that both could come back online again.

1961Nick

zeupater wrote: »

Conspiracy theory, well maybe not, but even those without Faraday cages & tin-foil hats would be able to follow the logic & recognise the conclusion! ...


HTH
Z

You called......:)

After looking at the numbers I really couldn't decide whether this scheme would work or not without knowing the likely calls on the battery by the grid. It'd probably take 12 months of data gathering .....data that appears to be withheld from the end user....to have any idea how it will interact with solar production/storage. The worst case is that a battery full of solar energy is discharged by the grid just after sunset, and replenished just before sunrise. Even with a small 4kWh battery that's 4 x 13.5p of lost solar + an import of 4 x 16.9p (15% round trip inc) + 4kWh of solar needlessly exported the following morning.

On the other hand, if the grid makes little call on the battery, it's money for virtually nothing.

If I was to sign up for this scheme (which I wouldn't), I'd want access to the grid demand data, and I wouldn't exclude the £1500 payment from my initial budget as I'd anticipate having to buy out the contract.

joefizz

mmmmikey wrote: »

p.s. happy to try again and answer questions if this doesn't make sense. If it does make sense it will lead to questions about iBoost and other things, but I've left that bit out for now.....

Mike,
Doesnt really apply to me (being in a different country and all) but if you had the smaller powervault and signed up to this, theres nothing stopping you putting a sofar and pylontech on the ac side and using that as your own....
...would probably need a diagram, flow chart etc as you might end up charging the powervault from your pylontech or whatever but if you generate enough and normally top the battery out....
I know it complicates no end and youd need to work out the figures. Ive no research on the powervault so it might be cheap enough to get 2 and only use one for STOR with all things considered...

Hmmm... Ive imported 2 units since the start of the month and exported 77...


I know there is talk here of changing DNO requirements to allow for STOR with possible matching panels (not capped at 4kw) sometime this year but until its firmed up Ive no figures.
Like yourself I dont have a full year of data yet but having already doubled battery size, having 2 split systems may at first seem stupid, if theres some sort of scheme to pay or almost pay for one and you have spare capacity...or can add it...

Zarch

So with 4.8kw of Pylontech batteries and the inverter at £2200.

https://www.ebay.co.uk/itm/Pylontech-4-8-Battery-Sofar-Solar-PV-ME3000SP-offgrid-Storage-Controller-Cables/264235136644?hash=item3d85a43684:g:eOkAAOSwMoZchY6j

4kWh usable for arguments sake? Fill it from solar say 300 days a year, save 4kw x 13.7p (current electrical unit price) x 300 = £164/year.

£2200 / £164 per year = 13.4 years payback...... we not quite there yet?

How low does it need to go for people to start getting tempted?

Just thinking out loud, are there days where you could possibly get more than 4kw out of it each day? Ie you use it through the night, fill it in the morning via solar, midday clouds, dip into battery with washing on etc, sun comes out again, battery fills back up..... then its full again for evening use?