Customer wants a 5.0kW hybrid with 8.2kWh battery fitted. He wants to increase his peak output and storage capacity without adding more PV so can I install an AC coupled inverter with a 8.2kWh battery? Will the inverters be connected to the same communication bus too?
Phdavies1 You can install an AC coupled inverter with attached battery. The hybrid and AC-coupled will be on separate communications buses but when the AC detects export to grid, it would divert to charge its own battery. As long as the hybrid was set to ECO mode where the house load is supplied from solar/battery (if no solar) first. Once house load was fulfilled from solar, any surplus from PV is diverted to its battery at a rate of up to 2.5kW (just over 3 hours to fully charge from empty). Once solar exceeds house load + 2.5kW (or the attached battery is full), the surplus is exported to grid. At this point, the AC-coupled would detect the surplus and start to charge its battery.
Both would discharge to the house when demand exceeded PV output (ie at night) and stop when SoC dropped to 4%.
A simpler and cheaper solution would be to add the second battery to the hybrid inverter which would see them as a single 16.4kWh battery. The ability of the inverter to feed house load from battery only would be limited to 2.5kW but it would be much cheaper to buy a 2kW kettle than an AC-coupled inverter and live with the odd occasion when you have to import from grid for the oven.
Tim Thanks for the reply Tim. The customer insists on trying not to consume energy from the grid. He has air conditioning, induction hob, electric oven among other electrical appliances (EV on its way too), so there will many moments where his peak demand outweighs the hybrid capacity. If initial outlay is not his primary concern do you think it would work?
Also, would the app see both inverters in one site for example?
Phdavies1 I had similar ideas when we had 12kWp of PV and two 5kW inverters each connected to a 8.2kWh battery. The PV is about 18 degrees west of south (more sun in the afternoon) and about 45 degrees roof pitch. We do consume 15-20kWh/day and have a peak house load (ignoring the rarely-used electric shower) of maybe 5kW when the oven and microwave are both on. We can supply all of this from the two battery/inverters and now have a grid import of about 30kWh/month because the grid buffers supply/demand as the inverter output ramps up or down to meet house load.
However, at our latitude of 51 degrees North, given the roof orientation and angle we should average a little under 1,000kWh generation annually for each 1kWp PV installed . On average, we should be producing around 12,000kWhpa. Since our system was commissioned in January, most days the two batteries are at around 40-60% charge level when they start charging in the morning and if the sun is shining, they are fully charged by lunch time. The afternoon is when we do the washing and charge our EV when it needs it and any surplus is exported. There have been at least two occasions when we have had poor weather and the generation has only been able to match house load during the day. That means we start the evening at maybe 50-60% charge level. When we have a second day like that, we are back on the grid during the evening/night of the second day and continue to be so until we have a really sunny day. We cannot survive days of rain and low cloud without the grid. We already know we will struggle in late autumn through the winter, to be almost off-grid because of the weather and shorter days.
To mitigate this, we have changed to an EV tariff with EdF and will use the 5 hour overnight window when necessary to charge the EV and the house batteries to whatever level we need at 4.5p/kWh.
Thinking about our situation, I don't think we would be able to charge a second battery to 100% via an AC3 on surplus PV except on the sunniest days. Our surplus on those days goes to EV charging and washing/dishwashing and the grid. If you customer has a significantly lower daily usage (say 10kWh) or is located much further south with no shading on the PV, it might work out OK. Otherwise accepting that you can't get a quart out of a pint pot might be the answer.
Regarding the app/web portal, all the plant is summarised by the Givenergy system and appears as one plant. You can drill down on the web portal but not the app.