Business case for a battery

[Simon R]

58 minutes ago, Wil said:

Agreed! my 5kWp system facing south only managed 5434kWh in '23. 4622kWh so far this year!

It's a case of don't post when jet lagged....

My 7MWh figure is total from 28/10/2022 not this years PV generation which rather changes the figures.

However it still does not take long for a battery to become carbon neutral which is the important issue.

[Simon R]

10 hours ago, G and J said:

And I’m the absence of such a case I’m tempted to conclude that as it uses resources then such is likely to be environmentally negative.  
 

I might want one for battery backup (lights, internet, MVHR, freezer, etc) but that’ll be managed in a different way to a save money battery.  So I’ll therefore accept that my battery system will be an indulgence.  

While it's true that consuming is environmentally negative, investing to use less in the future is not environmentally negative. Without it we would not have solar or wind farms.

Building to passive house standards consumes more resource, but pays back in reduced energy cost over the building life. Similarly running an EV is less damaging that running an IC over the life of the vehicle.

Backup for the grid was not a consideration in my choice to install a battery.

 

[G and J]

26 minutes ago, Simon R said:

It's a case of don't post when jet lagged....

My 7MWh figure is total from 28/10/2022 not this years PV generation which rather changes the figures.

However it still does not take long for a battery to become carbon neutral which is the important issue.

Now I understand.  I stupidly assumed you meant per year.

[JamesPa]

On 20/10/2024 at 09:46, Simon R said:

However it still does not take long for a battery to become carbon neutral which is the important issue.

I agree carbon neutrality is important, but how are you saying a battery becomes carbon neutral.  You seem to be linking it to solar and I confess I don't understand the linkage, unless for some reason you can't export any excess solar generation you may have to the grid and so, in the absence of a battery, it is wasted.  

[Simon R]

5 hours ago, JamesPa said:

I agree carbon neutrality is important, but how are you saying a battery becomes carbon neutral.  You seem to be linking it to solar and I confess I don't understand the linkage, unless for some reason you can't export any excess solar generation you may have to the grid and so, in the absence of a battery, it is wasted.

Well, it's true I'm considering PV input to the battery as carbon neutral. If I didn't store any electricity, any residual from local consumption would get exported, which all helps decarbonise the grid. If the grid was carbon neutral then there would indeed be no case for batteries.

With a battery in place I use very little electricity from the grid and the times at which it gets used are typically outside the times when solar is being generated. If a battery was not available this would have to come from the grid with the associated carbon cost.

In an ideal world it would be great if EV's were grid linked when plugged in and their batteries available as a supply/demand grid buffer. There are moves to make this a future possibility, but like all things it's more complex than it would at first seem.

[SteamyTea]

1 hour ago, Simon R said:

Well, it's true I'm considering PV input to the battery as carbon neutral

The problem is, we need to sequester the excess atmospheric CO₂ levels (from about 422ppm today down to about 300ppm) as well as deal with the excess ocean/lakes and rivers acidification.

The UK uses about 130 MTOE (1,511,900,000 MWh) each year (2020 numbers for total UK energy).

That is a mean power requirement of 1,725,913 MW, or 1,729 GW.

As an example, a large nuclear reactor can deliver 1.5 GW, so we would need 1,200 of them.

As demand fluctuates between by a factor of 3 during the year, we would need storage of approximately 15,768,000 MWh, or 16,000 GWh to smooth of those fluctuations.

Taking a best case of 50 kg CO₂/kWh for a battery manufacture, and 10,000 charge cycles, that is 5 gCO₂/kWH or 5 tonneCO₂/GWh.  80,000 extra tonnes of CO₂ added to the environment.

Now my car has emissions of 185 gCO₂/mile (ish).  So that 80,000 kg extra tonnes of CO₂ is equivalent to 432 million miles.  About 1% of the mileage of my last two cars over 12 years.

 

So I don't think we have to worry about the CO₂ from batteries even of we have to replace them every 10,000 charges.

 

 

Edited October 26 by SteamyTea

[Simon R]

4 hours ago, SteamyTea said:

The problem is, we need to sequester the excess atmospheric CO₂ levels (from about 422ppm today down to about 300ppm) as well as deal with the excess ocean/lakes and rivers acidification.

I must confess I’m slightly intimidated when replying to your post…..

 

I don’t think that any sane person would argue that the figures on atmospheric CO2 are just horrible. There are quite a few carbon sequestration options around but few are showing anything like the promise to be able to do the job, which is depressing in itself. Getting control of atmospheric CO2 is the biggest challenge facing humanity.

 

Moving on….I’m trying to get my head around the figures. Google informs me our generating capacity is in the order of 101GW (2022 figure). Energy consumption total in the region of 1,729GW, so a factor of 17ish short when it comes to consumption. That’s a lot of additional generation capacity required and the goal of being oil free is a long way off.

 

Housing accounts for something like 14% of the UK power consumption. Some 5% houses in the UK have PV installed, depending on what figures you take 50-65% are suitable for PV installation. If I could use my EV battery to buffer my use, it would be better than having a separate house battery. However the standards aren’t there and even if they were it would not be a universal solution.

 

For me it’s the ‘ant pissing in the ocean’ approach, every little helps, even if it’s apparently inconsequential.

[JamesPa]

11 hours ago, Simon R said:

Well, it's true I'm considering PV input to the battery as carbon neutral. If I didn't store any electricity, any residual from local consumption would get exported, which all helps decarbonise the grid. If the grid was carbon neutral then there would indeed be no case for batteries.

With a battery in place I use very little electricity from the grid and the times at which it gets used are typically outside the times when solar is being generated. If a battery was not available this would have to come from the grid with the associated carbon cost.

 

Your are right to consider PV as (more or less) carbon neutral.  However I think you are wrong to conclude that this means that the battery helps reduce carbon emissions:  

• If you generate 1kWh of PV and use it yourself at the same time (ie without a battery) then that's 1kWh less that the grid must supply and therefore the carbon associated with 1kWh is 'saved'.
• If you generate 1kWh of PV and use it yourself wholly or partly after storing it in a battery then that's (with a little loss) 1kWh less that the grid must supply and therefore the carbon associated with 1kWh is 'saved'.
• If you generate 1kWh of PV and export it (whether or not you are paid) then it will be used by your near neighbours and that's (with a little loss) 1kWh less that the grid must supply and therefore the carbon associated with 1kWh is 'saved'.  This is the case until the local solar density is so high that all of the local load is satisfied, which, just by casual observation of rooftops, is a long way off in most places in the UK

 

The carbon reduction is due to the PV not the battery, and the battery doesn't make a material difference, its the PV that matters.  So this is emphatically not (at present) an argument for the environmental benefit of batteries.

 

11 hours ago, Simon R said:

an ideal world it would be great if EV's were grid linked when plugged in and their batteries available as a supply/demand grid buffer. There are moves to make this a future possibility, but like all things it's more complex than it would at first seem.

 

Absolutely and I think its the future.  This will reduce the scale by which the grid capacity needs to be increased (saving shedloads of money) and indirectly save carbon emissions.  The later is because of the embodied carbon in the infrastructure that will not need to be built as a result of using a resource that was going to be created anyway (the car) to do two jobs not one.

 

Edited October 26 by JamesPa

[Simon R]

1 hour ago, JamesPa said:

If you generate 1kWh of PV and use it yourself wholly or partly after storing it in a battery then that's (with a little loss) 1kWh less that the grid must supply and therefore the carbon associated with 1kWh is 'saved'.

Yup, that's precisely what I find is the case. Energy generated and stored during the day is used to run the house to cook supper, watch TV, do the washing and make breakfast all done when the sun is not shining. Of 7MWh generated 4MWh went into the house and 3 got exported. Without a battery far more would have been exported as it is generated at times when we couldn't use it. Any residual left in my battery gets used to charge my EV leaving just 20% in the battery to get me through breakfast and into PV time. It's not perfect by any means but it helps.

 

[JamesPa]

21 hours ago, Simon R said:

Without a battery far more would have been exported as it is generated at times when we couldn't use it. Any residual left in my battery gets used to charge my EV leaving just 20% in the battery to get me through breakfast and into PV time. It's not perfect by any means but it helps.

Sorry but the battery doesn't help carbon emissions.  If excess generation is exported instead of being used by you then others on your street 'cause'  less carbon emissions as a result of a proportion of 'their' electricity coming from your PV rather than a power station. 

 

The global (and even local) outcome is (more or less) the same with or without a battery.

 

The only carbon benefit would be if you can store in a battery and use at times when carbon intensity is higher (in lieu of import).  So far as I am aware batteries don't yet respond to the carbon intensity of the grid, they respond to price which does not appear to be a good proxy for carbon intensity (unless someone can show that carbon intensity and price are well correlated which hasn't occurred to date).

Edited October 27 by JamesPa

[SteamyTea]

1 hour ago, JamesPa said:

they respond to price which does not appear to be a good proxy for carbon intensity (unless someone can show that carbon intensity and price are well correlated which hasn't occurred to date).

How far back in time have you looked?

 

I think the problem may be because the 'grid' is set up with 4 priorities:

 

Security of supply

Long Term Delivery Contracts

Low Carbon Priority

Predictions/Balancing

 

None of those sit well with each other these days.

[JamesPa]

19 minutes ago, SteamyTea said:

1 hour ago, JamesPa said:

they respond to price which does not appear to be a good proxy for carbon intensity (unless someone can show that carbon intensity and price are well correlated which hasn't occurred to date).

How far back in time have you looked?

I plotted UK carbon intensity Vs east of England agile price for Oct 2023 - sept 2024.  I then repeated the exercise with carbon intensity as a percentage of average carbon intensity on the same day, which I think is a metric more relevant to batteries.

 

In both cases there was a weak positive correlation (r squared =0.2). Visually they look close to uncorrelated.

I couldn't download regional carbon intensity for more than a day at a time, which is why I used UK figures.

 

I would be delighted to be proven wrong.  Others may have more information.

Edited October 27 by JamesPa

[Simon R]

1 hour ago, JamesPa said:

Sorry but the battery doesn't help carbon emissions.  If excess generation is exported instead of being used by you then others on your street 'cause'  less carbon emissions as a result of a proportion of 'their' electricity coming from your PV rather than a power station. 

I think we're both suffering a bit of confirmation bias, I could easily be wrong.

The carbon intensity if the grid is not linear. The very times I'm using electricity are the times when the grid carbon intensity is at it's greatest. If having a battery helps smooth this great. I would love to think that if enough people had batteries it would prevent the firing of a gas turbine.

Think local , act global. I'm not an expert, but I do care.

[JamesPa]

Just now, Simon R said:

. I would love to think that if enough people had batteries it would prevent the firing of a gas turbine.

If they had batteries and solar then yes, on days it's sunny.  But unless there is no local real time use for excess PV generated, the batteries aren't helping.  This will likely occur when we have a lot more PV than we currently do, but at present there can't be many places in the UK where that is the case (we will know when we start getting charged for export not paid).

 

In the absence of PV saturation and unless price and carbon intensity correlate, or they specifically charge and discharge their batteries to minimise carbon intensity not cost, then probably not.

[JamesPa]

32 minutes ago, Simon R said:

The very times I'm using electricity are the times when the grid carbon intensity is at it's greatest

If that's the case for you then I grant a battery may help.

 

However most people reputedly use a battery to minimise cost and, in the absence of a good correlation between cost and carbon intensity then that's not the same as minimising carbon.

 

We could really do with some solid information on this, nothing would please me more than to find evidence that domestic batteries do minimise carbon as it would make the case for me to simplify my energy management!

 

That said it may well be that consumer batteries are needed to reduce the infrastructure costs of a decarbonised grid to acceptable levels.  Without a doubt electrification places strains on the grid which will require expensive infrastructure upgrades.  These can be mitigated in part by load management.  Whether we need batteries to do this or alternatively the combination of the management of car charging and using houses to store heat energy by managing heat pumps, I don't know. 

 

I'm not even sure that the industry has yet reached a position on this.  My understanding is that, until recently, they were focussed on grid reinforcement (at our considerable expense) not demand management.  I also understand that this may change now that NESO has been brought into public ownership.

Edited October 27 by JamesPa

[SteamyTea]

18 minutes ago, JamesPa said:

Others may have more information

I am having a look at things at the moment.

 

Different data sets, Gridwatch and ONS system prices, which is sadly just daily prices.

[SteamyTea]

Right.

As usual, with statistics, life is never easy.

This is a correlation chart that plots price and generation.

I have grouped the generation by CO₂, Coal, Gas, Oil are high CO₂, Biomass and Pumped are medium CO_2, and Nuclear, Wind, Solar and Hydro as low CO₂.

The data runs from Jan 1^st 2020 to 26^th October 2024.

 

 

More to follow

[SteamyTea]

Right

 

Some quick chart plotting against demand.

The main thing I can glean from this very quick analysis is that two things happen.

CO₂ is lower when generation is lower i.e. <33000 GW and that charging batteries when demand is lower will increase demand, and therefore increase CO₂.

 

(I may have got the axis title wrong and actually mean MW not GW, shall have to check later, like tomorrow, as it is past my bed time)

 

 

 

 

 

[JamesPa]

12 hours ago, SteamyTea said:

Right

 

Some quick chart plotting against demand.

The main thing I can glean from this very quick analysis is that two things happen.

CO₂ is lower when generation is lower i.e. <33000 GW and that charging batteries when demand is lower will increase demand, and therefore increase CO₂.

 

(I may have got the axis title wrong and actually mean MW not GW, shall have to check later, like tomorrow, as it is past my bed time)

 

 

 

 

 

 

Excellent plots thanks, can you tell us what conclusions you reach from this in relation to price and carbon intensity (these are wholesale prices I presume, Im guessing agile follows wholesale prices).

 

[SteamyTea]

18 hours ago, SteamyTea said:

 

That is the conclusion.

The grid gets more sooty as we use more, really down to not enough low carbon generation, but that is changing, so price stability will cost me along.

[JamesPa]

1 hour ago, SteamyTea said:

That is the conclusion.

The grid gets more sooty as we use more, really down to not enough low carbon generation, but that is changing, so price stability will cost me along.

Sorry to be dense, but I'm still not seeing how to interpret that to work out if retail price and carbon intensity correlate or not 

[JohnMo]

1 hour ago, SteamyTea said:

really down to not enough low carbon generation

Unless you live in Scotland 😁

[SteamyTea]

18 minutes ago, JamesPa said:

Sorry to be dense

That's OK.

 

Basically, the amount of low and medium CO₂ generation is fixed, so marginal increases are dealt with burning gas. Gas has a volatile price.

Also, because we don't have enough spare RE generation, and very little storage, in the scheme if things (pumped storage is to do with load balancing), we rely on demand predictions. It is those demand predictions that set the price, and because they are predictions, some margin has to be built in.

When it goes wrong, and we have to quickly add generation, what actually happens is that the 'hot spinning reserved' come on line. It is those reserves that cost a fortune i.e. £500+/MWh.

When the prediction is the other way, and there is over production, it is often the RE that gets switched off, and that has to be paid for, often at double the going rate i.e. the strike price.

It may seem strange to switch off the low CO₂ generation, but it works out cheaper because it is easy to switch of say 10, 2 MW turbines, in different places to balance the local grids, that switch off a 100 MW CCGT and switch on a few  small diesel generators to make up the 80 MW.

 

It is more common complicated than that in reality as other factors have to be taken into account. 

One more of the pervers factors us the way that the half hour bidding auctions have elevated some RE generation that is still based in gas prices.

While this does not affect new RE generation, the legacy stuff is still generating, and because they have a lot of data, and market experience, they can decide not to bid on the day ahead market, but hope to pick up some balancing capacity, which pays better.

 

While our wholesale market has generally been very good at keeping the price down, it has caused, at times, higher CO₂ generation overall.

 

So getting back to storage, local or large scale, at the moment, it probably increases overall CO₂ grid intensity.

This will change in time with the introduction of more RE, but not for a decade or so.

 

It has been a long time since I looked at all this, but I seem to remember that grid frequency, which many people think can be used to control local storage i.e. elevated frequency, start storing, lower frequency, start delivering, does not work. 

The Grid Operator, predicts about 4 hours in advance the short term needs, and allows the frequency to rise and fall a bit. It is similar to slightly raising your house temperature because you know the night will be extra cold.

 

The whole grid balancing is a (expletive deleted)ing marvel and we should really not tinker with it too much to save a few quid on our bills. The security of supply is globally second to none. We don't want our hospitals, and traffic lights losing power at 6PM, so we can earn £2. 

It is one of the reasons that these ToU tariff trials are small scale, it will be very hard to integrate in a large scale.

[SteamyTea]

13 minutes ago, JohnMo said:

Unless you live in Scotland

Yes, it is why we disconnect you.

 

 

[Mr Blobby]

23 hours ago, SteamyTea said:

CO₂ is lower when generation is lower i.e. <33000 GW and that charging batteries when demand is lower will increase demand, and therefore increase CO₂.

 

The first statement is correct but it does not follow that increasing demand will always uncrease co2 emissions. 

In Ireland, where admittedly wind penetrations is much higher than GB, at about 50%, and almost all on-shore with no nuclear here, then wind is regularly curtailed at night when demand falls off a cliff.

Wind  is curtailed because the increase in demand at 6 am requires fossil fuel plant to remain on,  close to min gen, to ramp up quickly and exceed total wind capacity.

Any increase in demand here overnight when wind is curtailed is satisfied with zero extra co2 emissions as the turbine blades are not feathered.  Wind is not curtailed just because of cost (ok there are start costs in the market for fossil plant) but there is just more wind generation than there is demand.  

The grid stability question here is an interesting one.  Ccgt plant running near min gen during periods of low demand is less efficient and increases emissions per MWh.  For such ccgt plant the increase in demand would improve the heat rate and  reduce emissions per MWh generation.

The increase in domestic batteries and EVs charging overnight and smoothing demand will ultimately reduce overall emissions per MWh.

 

Edited October 28 by Mr Blobby