Agile periods and charge/discharge efficiency compensation

RB63

I've been thinking (always a bad sign...!)
Setup here is 6kW solar to Gen 1, 5kW Giv 5.0 Inverter with 19.2kWH battery storage (2 x GivBat9.5). Max charge/discharge rate 2.6kW with the batts/inverter
On Agile.
We use about 30kWh of leccy a day (the business building runs off the supply as well as the house).

Now - the raw turnaround efficiency of putting energy in and getting it back out of the batteries is about 90%. So I was thinking if we could automate the picking of slots based not on the cheapest but based on the differential between forward periods, i.e. if the next x periods are more than 10% than the current ones then it is worth charging. Just not sure how you would define the current and forward periods - because if it was expensive for, say, 6 periods (like early evenings) then you would want to start charging earlier to cover that. I know just picking the cheapest x slots works of a sort but is there a better algorithm to optimise this?

Digitalsafaris

Similarly thinking, and related.... In general, in winter, I use WW Agile slot selection to charge the battery when it's cheapest and use the battery when it's expensive. I often get to midnight with plenty still in the battery. I'd like to export that (for 15p) but it's only worth while if I paid less than that (15p-10% for efficiency) in the first place. I can do this manually with an export schedule which I check daily and turn ON/OFF depending on the current import costs. But if this could be automated, so that export only happened if the selected Agile import prices in the last 24 hours averaged less than a set threshold (say 14p), that would be fantastic. ("Conditional Export" - a wish, rather than a formal enhancement request).

johalareewi

Digitalsafaris but it's only worth while if I paid less than that (15p-10% for efficiency) in the first place

Not strictly true. If there is plunge pricing coming up (or very cheap electricty) then dumping the battery at 15p, importing at the plunge (or cheap) price then exporting at 15p can more than cover the 'loss' you made to dump the battery in the first place.

kerregan

Digitalsafaris Sunk cost fallacy: the price you bought at is irrelevant.

Digitalsafaris

kerregan Had to look this one up. Shortest definition found is "sunk costs are costs that have already been incurred and cannot be recovered". Need persuading as to why this applies here, to a decision of whether or not to export by discharge from battery. Cost of charging the battery is a "sunk cost", but if you can recover that cost by exporting, I see no fallacy.

Maybe what you are saying is that is the wrong approach- you need to look at the cost of recharging after the export, rather than the cost of selling what you already have. That would be consistent with johalareewi

kerregan

Digitalsafaris The price you bought at is totally irrelevant, even if was free or negative pricing. The past is the past and cannot be undone. Imagine you charged / bought 5kw at 20p and 5kw free, their value now has nothing to do with the price they were bought at. All 10 units each have the exact same value, which is what you could sell them for now, or the current import price if you use them.