Hypothetical question regrading exporting and "brown energy"

I have been using my 13.5kWh AIO and gateway quite happily for months now and my smart meters were fitted 5 or 6 weeks ago. I am subscribed to Cosy Octopus for import and Fixed for outgoing. With this setup and predbat running on HomeAssistant Green, I find that my battery discharges to the configured limits thrice per day as expected. So far all is well. I import around 52kWh per day and export 24, so it should be easy to spot that at this time of the year I am simply charging the battery and selling it back. During the summer moths, the picture will be different because of my 11 solar panels and 3.6kW solar inverter

However Octopus are not obliged to make export payments for "Brown Export" so I suppose at some point they might decide to reduce/limit export payments, so I would need to do things differently.

I figure that with my current setup, charging and discharging 3x per day is marginally cost effective (the round trip losses cut in to the <3p arbitrage between my import and export rates) but at least it keeps the battery warm 🙂. I am thinking that should I not be paid for exporting, I would simply reconfigure predbat with an export rate of zero and exporting would only happen when there is excess solar generation and the battery is also full.

In this scenario predbat would be used to balance the expected solar generation and the expected load in order to minimize imports so that the battery does not get to 100%

Am I right in this assertion? My household is a heavy user of electricity and in the summer, my solar panels just about generate a whole day's worth of juice. Therefore there would be little wasted exporting if the battery was suitably discharged at sunrise.

Weasel
How do Octopus know it is brown?
I have no issues with Octo when Predbat dumps a bit at 23:00 at 15p before Eco7 charge at 00:30 at 12.76p

Weasel
My working assumption is that there is a 15% loss in the conversion between AC in, DC stored, AC out on my AIO. Looking my total charge/discharge figures, and listening to others on this forum leads me to think this isn't far off. (In Predbat I have set input_number.predbat_battery_loss and input_number.predbat_battery_loss_discharge and input_number.predbat_inverter_loss all to 5%. What do you use?)

There are several ways to discourage exports, but I'd suggest maybe looking at tweaking the assumptions of these values first? But yes, I think putting the export rate to 0p should also do the trick. Of course, it would mean that the (confusing ) Predbat graphs would be wrong.

It's perhaps worth noting that the gap between 15p export and 12.65p import on Cosy isn't very big! I would be surprised if you make anything, or at least enough to justify the battery wear and tear (you may want to check out the limits in the warranty). I do the brown export thing most nights, but I am on IOG and have the gap between 15p and 7p to exploit.

Do octopus say they are not obliged to pay for exported “Brown Energy” somewhere then?

And how would they know if you imported it and used it directly (car charging for example) or imported it and stored it for later use? And if you exported, how would they know what was exported from your generated solar (stored in the battery), directly exported from solar, or imported and then exported later?

I really hate the term “Brown Energy”. I think it’s a particularly bad and deliberately misleading definition on the part of (some) energy companies to avoid paying you as much for green energy and to make more of a profit from you. Or basically just to pay you less for your green energy that they will sell to another customer as “green energy” for much more.

All Octopus imported energy is supposed to be green right? So if you export it back to them it’s still green. What you generate from your solar or wind or a water mill is green too. So all that export will be green ! Importing at cheap times and exporting at expensive, high carbon times is supposed to help the grid AND make it greener. Which you deserve to be paid for at a reasonable rate.

Suppliers calling it “Brown energy” is just plain wrong, misleading and a way to avoid paying you for your green generation or re-export of their green energy.

The only way I’d agree it’s not green is if you were to personally run a diesel generator and export that or you buy “dirty” expensive energy from somewhere else (where?) and export it to them. Or to import from the grid at the most expensive and carbon high times and export that at the cheap green times. None of which would make any sense logically or financially.

Bit of a rant and I didn’t answer your question,
Sorry. 😂

• I’m also on IOG and importing at 7p and exporting the remains at 15p in the evening.

PianSom I do the brown export thing

Wash your mouth out ! 😂

You mean the “green export thing” 👍🏻

Pete UK yes Octopus state this in section 4.5.1

Here

PianSom
I haven't looked in detail at the predbat loss settings and I agree that the savings would be marginal. Just for grins, I will set the export rate to zero for a week or two starting next week and see what happens to my bill

Oh yep, so diesel generators out then - makes it “brown”. But presumably the GE batteries are allowed by the bit covered about SEG approved batteries. (?)

This bit is interesting too…

4.6.3 any Energy exported that has attracted a payment through a FIT scheme or another Export Tariff supplied by another energy company;

I’m sure there are people doing this. (No names) 😂

Weasel I would simply reconfigure predbat with an export rate of zero and exporting would only happen when there is excess solar generation and the battery is also full.

You could do that, but as PianSom highlights this’ll mess up your graphs and ‘cost so far today’ in Predbat.
An alternative approach is to just set predbat to ‘Control charge’ instead of ‘Control charge & discharge’ then Predbat won’t do any forced discharging, only export from solar when the batteries are full.

TBH I wouldn’t worry too much about much about the brown export risk, I’m on Agile and on cheap rate periods Predbat can be very energetic, charging in one slot, discharging the next, all to maximise the export income.

Pete UK 4.6.3 any Energy exported that has attracted a payment through a FIT scheme or another Export Tariff supplied by another energy company;

This is to cover you trying to get paid twice for export generation. If you have a FIT array then you have to give up the deemed export FIT payments when you move onto an Octopus export tariff. I guess this is their double-check that if you haven’t given up the deemed export FIT and they don’t spot it, then they’re not obliged to pay you.
(the FIT generation payments continue unchanged regardless of SEG payments)

geoffreycoan thanks for that tidbit. I have set up my export rate as zero and will run for a week to get a better idea of what is cheaper etc, bur early indications are that even on Cosy Octopus, it is slightly better for me to export as much as I can. I can save £0.60 to £1 per day, so probably £200 per year which over a 10 year period is £2000. Given I have a 12 year guarantee, then it might be worth the extra wear and tear on the system.

Next week, I will set up the Control Charge only - just to gain experience and knowledge etc

I should then be able to decide what's best for me

I wondered the same, because I have 2AIOs now so I charge for for 2 hours 12-2am, export for an hour, then charge fully before 5:30am. I use the battery all day and export what’s left before 11:30. Octopus don’t know I have batteries, they know I have solar because I have export and they know I have an EV because I’m on IOG. They don’t know that the energy im importing isn’t going into my car and they don’t know that what I’m exporting wasn’t stored in my batteries from my solar panels. So until something changes I’m going to fill my boots.

I set predbat to 'Control Charge' and reverted the export rate to the GivTCP sensor values and observed that the behaviour was as expected. I then started tweaking other values as a learning and fine tuning exercise. I now have a better understanding of more of the parameters.

This evening, I decided to revert to exporting, so reset many of my tweaks to the default values before setting 'Control Charge and discharge'. Having done this, I noticed that no discharge periods were planned so I scratched my head, restarted predbat, checked my config and apps.yaml and saw nothing obviously amiss.

It took a while for the penny to drop. I had set my battery_loss, battery_loss_discharge and inverter_loss all to 0.05 and these all combined (naturally) to make it unattractive to export at all. I changed the values back to their defaults and now have exports planned as expected.

I am writing this to remind myself and others that it is important to

• Note down all configuration changes and the reason they were made
• Take time to understand what the individual item are and how they might work in combination

I am going to continue with my brown exports as they definitely seem to be financially beneficial based upon my billing from Octopus. The difference is small on a daily basis, but it soon adds up

Weasel I am going to continue with my brown exports

What you’re doing isn’t “brown export”.

Brown energy is when you do something like fire up your own diesel generator and try to export that to the grid. ie you’re putting external energy into the grid which isn’t of a green origin.

Importing and then exporting again isn’t “brown energy” and is allowed in their T’s and C’s.

You’re really playing into their hands if you start to mis-label it as brown export. It’ll just give the energy companies an (unjustified) excuse not to pay for it.

Pete UK fair enough Pete and thanks for the advice. I am still in two minds about import and export. On the one hand, not exporting may cost me a couple of hundred quid per year, but means I have a higher SOC and can survive longer grid outages. On the other hand, apart from a recent 4 hour outage, my grid supply has been fine for years with maybe the odd hiccup.

My original motivation for a battery was to have a guaranteed supply with little consideration for cost. Now I have a battery, I realise that I can make far better use of it by not only importing at lower cost, but also exporting too.

I think I will balance my desire for a solid and guaranteed supply with my newly found desire to cut costs by setting a slightly higher minimum charge level in predbat. This plus the UPS systems I have in the house for the IT kit and telly etc should assuage my paranoia 🙂

Of course if I did not have a battery, I would not have these issues to worry about 😃

Weasel It took a while for the penny to drop. I had set my battery_loss, battery_loss_discharge and inverter_loss all to 0.05 and these all combined (naturally) to make it unattractive to export at all. I changed the values back to their defaults and now have exports planned as expected.

Glad to hear that you are getting to grips with the controls, sounds like you are well on the way to achieving your brown (energy) Predbat Ninja belt!

But seriously. you observed that setting battery and inverter losses all to 0.05 (5%) you got no export, but on changing them to the defaults you started seeing forced exports “as expected”.
The question is what are the right set of losses and are these exports you are seeing actually making you money or losing you money?

Different people on this forum more clever than me have done tests to determine battery and inverter losses and have concluded as far as I can recall that it’s between 10 and 20% overall. So somewhere in the middle like 15% is not unreasonable. Mine are 0.055, 0.05 and 0.04 but don’t ask me why I ended with those values.

Just to say that if you set the losses too low then you may well be getting exports you expected but might not be making any money from them after (true) losses are considered.
The one control that is entirely up to you to set is metric battery cycle cost. This puts a nominal value on using your battery. I have it set to 0p as I want to use my battery not artificially constrain it.

geoffreycoan i have set my battery cycle cost to zero and am ignoring the specific predbat predicted costs. I am basing my costs only upon what Octopus actually bills me. I have no desire to calculate the actual round trip losses etc, it is sufficient for me to know that Octopus will bill me less per day (by about 60p to £1).

The only artificial constraint i might consider changing is the soc_min