What an exceptionally helpful thread! Does anybody have any thoughts on the following issue?
We're trying to achieve a reasonably simple Time Based Control nuance, using 2 PWs and a Smart Gateway, coupled to a 10kWp 32 panel solar array. We publish reasonably comprehensive data on our set up and the financial and CO2 savings it delivers at
How to Electrify Your Life, Save Loads of Money and Save the Planet
We have a simple TOU tariff (Octopus Go Faster, UK), which has only Peak and Off Peak rates (no Shoulder rate, etc.). The off peak window is 20:30 to 01:30; all the rest of the day is peak, from 01:30 to 20:30.
With the app set to Time Based Control, 0% reserved for grid outages, and Grid Charging set to "Yes", the system performs as we want it to, along the following lines. Let's assume the daily cycle starts with the batteries at 0% SOC at 20:30 to make things clearer.
A: During the 20:30 to 01:30 Off Peak window, the PWs charge from 0% to 100% using off peak grid import.
B: From 01:30 to some point in the day, the PWs discharge to power all loads in the house, depleting to 0% in the winter months.
C: At some point in the day (which can be either before or after B, depending on season) surplus solar starts recharging the PWs.
D: At some point in the afternoon/evening, there is no more surplus solar and the PWs stop charging (or when they reach 100% in summer).
E: From D onwards, residual solar powers the house and the PWs remain at the SOC they reached at D.
F: When residual solar is insufficient to power the house, the PWs blend in and discharge as required to top up whatever residual solar is available.
G: When ALL solar stops, the PWs entirely power the house, until they deplete to 0%
H: If G is reached before 20:30, expensive peak grid import powers the house.
And then the cycle starts again. All working as expected, simple and transparent. Off peak grid powers the house AND recharges the PWs during the 20:30 to 01:30 window. If the PWs are full of solar at 20:30, they will continue to power the house into the off-peak. In high summer, the PWs will entirely power the house throughout the 01:30 to 20:30 peak period, with the whole charge/discharge cycle being exclusively powered by solar, without the need for overnight off peak grid imports to charge the batteries.
Now here comes the nuance we're seeking to achieve. Is there any way to convince the PWs to remain at 100% from the end of the grid off peak window until some LATER time we specify, so that they don't start discharging straight away? We want deliberately to allow PEAK electricity to power the house from 01:30 until our specified later time (let's say 06:00 for example). We want PW discharge to kick in at that specified time, not immediately at 01:30.
Could this be done by 'pretending' to have medium peak rate?
We're trying to do this to optimise PW discharge into the time it's most valuable to us, typically the 06:00 to 09:00 period, when heat pumps are at maximum load, electric bathroom radiators are on, our MX and Leaf are usually preconditioning and we're boiling the kettle (because Brits can't start the day without tea). Delaying the start of the discharge also gives the PWs a better chance of continuously 100% powering the house without the need for peak grid imports until the solar starts up in the autumn and spring months.
We're also trying to get finer grained control over discharge and charge timings, so that we're in a position to fully exploit the upcoming Octopus 'Savings Sessions' implementation of the National Grid "Demand Flexibility Service" during the coming winter. This is a UK scheme under which very large subsidies will be paid to eliminate demand from SPECIFIC peak periods (say 17:00 to 17:30 on a given day) to avoid grid outages during the most constrained periods. With incentives of £4 to 6 per kWh being proposed (which is FAR more than our Off Peak and Peak grid tariffs), having the CERTAIN knowledge that there will be sufficient juice in the Powerwall to give the house a ZERO grid import requirement in the target slot is super-important. And as these slots are most likely to be in the EVENING peaks, starting the PWs discharge LATER on a winter's day is the way to achieve the desired result. In short: we don't want to be in position where we cannot power the house from the PWs during those superpeak demand slots. We don't want to import a single electron in those periods!
Any thoughts from the assembled geniuses on this thread would be hugely appreciated.
Finally, on a related note, we've spotted that Version 22.18.3.21c0ad81 of the app FORCES the user to enter a sell price for each specified period in the Utility Rate. And it will NOT accept zero as the sell rate, so we had to enter £0.01. This does not reflect our particular reality: we don't get paid to export on a metered basis, we get a 'deemed export' subsidy under the old UK Feed In Tariff scheme. We do not want the AI to think there is ANY value in EVER exporting energy to the grid.
