Storage optimizer block

This function block runs a battery storage according to electricity prices. From the price series, the PV forecast and the state of charge it computes a schedule and derives a power setpoint: negative means charging, positive discharging, 0 standby. The setpoint can be connected directly to the input "Power setpoint" of the Marstek storage block, but in this form it also suits other batteries. For systems that expect the power at the grid connection point instead (for example Victron with ESS) the additional output "Grid setpoint" is available — there negative means feeding in.

The block covers two operating cases with one common method:

• Shifting surplus. The generated energy is buffered in the battery and released when it is worth most — either as avoided consumption in the house or as delivery into the grid.
• Recharging from the grid. If generation is not sufficient, the battery can be charged from the grid during a cheap hour and released later at a higher price. This happens only if the price spread exceeds the configured minimum profit.

How the schedule is built. The block forms pairs of a charging time and a later discharging time and rates each pair with its margin in cent per kilowatt hour. The charging cost already includes the losses of charging and discharging; the margin is therefore the profit that remains after all losses.

What is rated is always a combination of the origin of the energy and its later destination. Both prices of the price source are needed for this:

Three behaviours follow from this rating on their own, without having to be programmed separately:

• Because the consumption price is always above the feed-in price, own consumption is always more rewarding than feeding in — the battery supplies the house first.
• For the same reason, charging from your own generation is cheaper than from the grid — generation takes precedence.
• When feeding in is well paid at the moment, the cost of PV charging rises. The battery then does not buffer and the energy goes straight into the grid.

All pairs are ordered by their margin and served in that order, as far as charging power, discharging power and the state of charge permit over the whole period.

The schedule only enables, the magnitude comes from the measurement. If the schedule says "charge from generation", the block uses the measured grid power to put exactly the surplus into the battery so that as little as possible flows into the grid. If it says "discharge for own consumption", only as much is taken as the house is currently drawing. This keeps the schedule usable even when the forecast is off.

Without valid prices the battery keeps working on own consumption, only the price optimization is dropped. The setpoint is therefore not simply set to 0. The setting "Behaviour on data loss" allows standby to be selected instead.

The price source does not have to be wired. The blocks eFriends, AWATTAR and Day ahead electricity prices ENTSO provide their price series internally; the selection is made with the setting Price source. An exchange price source knows the consumption price only — for the feed-in the configured feed-in tariff is then used. If no price series is available at all, select the price source "Fixed prices": the block then works with the fixed consumption price and feed-in tariff. With a constant price no charging or discharging plan arises and the battery runs pure own consumption.

For the calculation to be correct, the prices of the source must reflect the cost actually billed. With the exchange price sources their VAT and surcharge parameters have to be set for this (these remain on the respective price block) — the plain exchange price contains neither taxes nor grid fees and would make grid charging look far too cheap.

The schedule is recomputed at the interval set under "Recompute every" — 15 minutes as delivered. Additionally on every interval change, on new prices, after every change in the settings dialog, whenever the PV forecast for today changes noticeably and whenever the measured state of charge deviates noticeably from the plan. The measurement inputs — grid power, state of charge, PV power, consumption and battery power — do not trigger a recomputation; they change continuously and are handled by the real-time control. For the state of charge there is the separate deviation check, which takes effect no earlier than one minute after the last computation.

Recording. Every hour the block stores grid consumption, feed-in, generation, consumption, charged and discharged energy, the state of charge as well as cost and revenue in euros; the data is kept for two years. It is shown in the charts of the Block storage optimizer control element. The amounts in euros are built continuously with the price valid at that moment — they cannot be derived from kilowatt hours times a fixed price once the tariff changes every hour.
Only what is measured gets recorded. If the input Grid power is unused there is no consumption, feed-in or monetary channel; without PV power no generation, without Battery power no charging and discharging, without State of charge no charge curve. Used means: an address or a connection to a neighbouring block. Consumption is recorded even when only the PV power is connected — the block then computes it itself.

Every computation starts at now. The first interval of the schedule is therefore shorter than the others and only holds the energy that still fits into the time remaining. In the schedule dialog the bar of the current hour is thus the power for the rest of that hour, not its average — after an interval change it grows back to full height.

Recording consumption and PV yield. The consumption of a house depends on the hour and the day of the week — a single fixed value is too rigid for that. The block therefore measures along every second and builds two profiles from it: consumption for every hour of every weekday (168 values) and the PV yield as a daily curve over 24 hours. The setting "Base load" only applies to hours for which there is no measurement yet.

Measurement runs through the input "Consumption". If it is not connected, the block computes the consumption from PV power, grid power and battery power — the same method as the Energy monitor block. If neither consumption nor PV power is connected, no recording takes place: without the generation the midday value would be systematically too low, and a wrongly learned profile would be worse than the fixed value.

At the end of each hour the hourly average enters the profile — not as a replacement of the old value but as a moving average with the configured learning rate. Outliers are limited beforehand to four times or a quarter of the previous value. A single unusual day — party, holiday, thunderstorm — therefore shifts the profile only slightly and fades out over the following days. The very first measurement of an hour is taken over directly so that an empty cell does not creep towards the correct value for weeks.

A cell is only filled once that hour has passed on that weekday — a complete profile therefore takes a week. As long as the cell itself is still empty, the average of the same hour across the weekdays already learned applies. The time of day shapes consumption far more than the weekday, so the profile takes effect after the first full day instead of only after a week. Only when nothing at all has been learned for an hour does the configured base load apply. The diagnostic CSV file records the origin per interval: "Profil", "Profil (Stundenmittel)" or "Parameter".

The PV profile additionally replaces the fixed bell between 6:00 and 20:00: the daily total from the forecast is distributed over the curve actually observed, which thus follows the season by itself. If no PV forecast is connected at all, the profile serves directly as the generation value.

Both profiles are stored and are available again immediately after a restart or after transferring a project. With diagnostics switched on the block outputs them as a message on every full hour; they get no addresses of their own.

The schedule has no addresses. Setpoint, consumption price and planned state of charge per hour are stored as runtime data in the controller and shown in the control element Block storage optimizer as vertical bars — one column per hour, up to 48 hours ahead. Several hundred values per block would be unwieldy as an address range.

What the recording does not do: public holidays look like a normal working day and pull its profile down. A longer absence lowers the values over several weeks, and the recovery takes just as long. After one week every one of the 168 cells has a value; the profile has settled after about four to six weeks.

Operating mode, the locks and the manual setpoint are not inputs. They are operated together with all other settings in the control element Storage optimizer block.

This is the only parameter of the block. All other settings — operating mode, locks, battery data, state of charge limits, price source, economics, recording and control — are made in the settings dialog of the control element Block storage optimizer. They are stored in the controller and survive the transfer of a project.

Without a linked control element the block works with its default values: automatic mode, automatic price source, 10 kWh capacity (the dialog expects the value in Wh, so 10000), 2500 W charging and discharging power each, state of charge 10 to 100 %. It runs with those, but it is not matched to the installation.

A right click on the block leads straight to the control element via Go to linked element. If several are linked, all of them are offered.