Manage Export

[AberDino]

I have a GivEnergy gateway, AIO and EVC, as well as a third party PV inverter. The 3kW PV installation is from 2012 and earlier this year I switched my deemed FiT export to metered SEG export. I use Home Assistant to manage the system.

Following the collapse of Tomato Energy, I switched my import and export to Good Energy (EV and Solar Savings). The Solar Savings export tariff pays 15p/kWh but the terms and conditions state that they have no obligation to make payments for any brown export.

This means that effectively I would like to export all my solar PV energy and run my house from the battery only, which is charged up to 100% overnight on the off-peak EV rate. As per the Predbat documentation, I have set the switch.predbat_set_export_freeze_only to on, which means excess solar will be exported rather than used to charge the battery. Given the time of year, I've not been able to test that yet, but I have no reason to believe this won't work. However, in addition to the excess solar energy, I would also like to export the "base" solar PV energy used to power the house load. Does anybody have any ideas or suggestions on how to accomplish this? I'm thinking I could use Home Assistant automation to track solar PV energy and export energy, and instruct the battery to discharge x kWh as required to keep export energy aligned with solar PV energy. Would that be possible?

On a different note, after watching Trefor's most recent YouTube video, I decided to sign up to Axle Energy (I used @springfall2008's referral link). I like the idea of supporting the grid as required and to get rewarded for it. The FAQs state that "Axle works for every tariff and supplier in the UK", but I'm wondering what the implications are for my Solar Savings tariff, given I would be exporting brown energy during the Axle events. Does anybody know whether Axle effectively take over my export meter during their events, i.e. there is no overlap with the regular export tariff? If that is the case, there would be no double-dipping and it would keep Good Energy and Axle Energy readings separate (and for me there would be no issue from a brown energy perspective). What would be the easiest way to temporary disable switch.predbat_set_export_freeze_only during an Axle event?

Thanks in advance for any feedback.

[gcoan]

I would also like to export the "base" solar PV energy used to power the house load. Does anybody have any ideas or suggestions on how to accomplish this? I'm thinking I could use Home Assistant automation to track solar PV energy and export energy, and instruct the battery to discharge x kWh as required to keep export energy aligned with solar PV energy. Would that be possible?

Yes that would be possible, when the sun goes down, assuming you have a suitable entity from your inverter you will have your solar energy today in kWh. Divide that by your inverter export rate, times by two for number of slots, and that will give you the number of predbat slots you need to set to manual export. Will need to adjust a bit for base house load.

I'm wondering what the implications are for my Solar Savings tariff, given I would be exporting brown energy during the Axle events. Does anybody know whether Axle effectively take over my export meter during their events, i.e. there is no overlap with the regular export tariff? If that is the case, there would be no double-dipping and it would keep Good Energy and Axle Energy readings separate (and for me there would be no issue from a brown energy perspective). What would be the easiest way to temporary disable switch.predbat_set_export_freeze_only during an Axle event?

Axle don't take over your export meter, you have granted them access to your export meter so they will obtain your export meter readings from the DCC and pay you based on what you export, and you will also get paid whatever Good Energy pay you for export as normal. As you note they're under no obligation to pay for brown export, but worst case is they won't pay, best case is you get a few pence extra.
I think the brown export term is common to a lot of energy suppliers. I think Octopus might say the same but in practice they always pay.

Predbat turns an axle event binary sensor on and off when there is an event on so you could use that to trigger an automation to change switch.predbat_set_export_freeze_only

[AberDino]

Thanks @gcoan, with a bit of tinkering that sounds doable. Do you know whether the Predbat Axle event binary sensor follows the start and end times of the event, or does it get triggered as soon as there is an Axle event scheduled? I don't want to have switch.predbat_set_export_freeze_only in the off state for too long, hence the question.

[gcoan]

The binary_sensor.predbat_axle_event is on when there is an actual event occurring and off otherwise so you can simply use change of state of the event as the triggers for your automation https://springfall2008.github.io/batpred/components/#axle-energy-vpp-axle

When an event is scheduled the details are available as attributes of the binary_sensor so if you wanted to trigger beforehand then you could read the attributes, but for your purposes triggering on the binary_sensor changing to on and off would do the job

[AberDino]

Hi @gcoan,

There is an Axle event in my area tomorrow morning, so hopefully my automation will work. I'll keep an eye on it in any case and let you know how it goes.

In terms of the custom export automation, I'd like to build in a safeguard to check there is sufficient charge left in the battery to take me through to midnight (off-peak), before scheduling a manual export. Given Predbat uses historic loads etc. to predict the battery SoC I was hoping to use that in my automation, but I can't quite work it out, probably because I don't fully understand the logic behind the various parameters.

The documentation suggests there are three sensor which could potentially be useful for the purpose of predicting house load:

• predbat.load_energy_actual
• predbat.load_energy_adjusted
• predbat.load_energy_predicted

However, I've been plotting these for the last few days, and they look a bit odd in the sense that the load energy forecast tails off for all three after 8pm, even though the actual load energy at 8pm is already close to the predicted daily total load energy. Also, at the end of the day I would expect predbat.load_energy_actual and predbat.load_energy_adjusted to equal my actual load energy, but they don't.

As you can see from the two plots below with yesterday's data, the 'predicted' predbat load energy values are 18.3kWh, but the actual load energy is 23.9kWh. Even at 8pm, the actual load energy is already higher (19.2kWh) than the predbat load energy values at the end of the day. I can confirm that this is the same load sensor defined in the apps.yaml file.

I've had a look through the predbat log files, and I did notice that the the load energy when my AIO is charging is ignored. At 2am last night:

Current data so far today: load 2.34kWh, import 13.8kWh, export 0.0kWh, PV 0.0kWh
Historical load totals for days [7] are [27.55]kWh, minimum value 27.55kWh
Historical days now [7] weight [1]
Today's load divergence 100.0%, in-day adjustment 94.67%, damping 0.95x, yesterday 94.67% today 100.0% blend 100.0%
Today's predicted so far 0kWh with 0.0kWh car/iBoost excluded, 2.39kWh import ignored, and 0kWh forecast extra
Today's actual load so far 0kWh with 0.0kWh car/iBoost excluded, and 2.31kWh import ignored

At the end of yesterday, a total 6.76kWh was ignored. As it happens, 18.27 + 6.76 = 25.03 / 1.05 (load factor) = 23.84kWh, which essentially is my actual load energy. So, is it correct that the 'actual' component from predbat's predicted load energy values does not include the load energy from the periods where the battery is not suppling the house (i.e. house use from grid when battery is charging or when there is is excess solar PV)? If so, why is that, because load is load, whatever is used to meet that load (grid/pv/battery), and is there a sensor which reports the "import ignored" energy value?

[AberDino]

Hi @gcoan,

Just to let you know the automation worked as planned this morning, switch.predbat_set_export_freeze_only was disabled for the Axle session only and just over 5kWh was exported.

If it helps others, this is the automation I used:

alias: Axle Event Allow Export
description: ""
triggers:
  - trigger: state
    entity_id:
      - binary_sensor.predbat_axle_event
    to: null
conditions: []
actions:
  - if:
      - condition: state
        entity_id: binary_sensor.predbat_axle_event
        state:
          - "on"
    then:
      - action: switch.turn_off
        metadata: {}
        target:
          entity_id: switch.predbat_set_export_freeze_only
        data: {}
    else:
      - action: switch.turn_on
        metadata: {}
        target:
          entity_id: switch.predbat_set_export_freeze_only
        data: {}
mode: single

There was a slight 'cosmetic' issue where the Axle export rate was doubled in the Predbat plan during the Axle event, but I'll report that separately as an issue.

If you have time at some point to provide feedback on my Predbat load prediction observations in the previous post, that would be much appreciated, thanks.

[AberDino]

I just noticed you have already fixed the Axle export rate doubling, so I will not report that as an issue.