Balance of Import/Export power

GivEnergy Products GivEnergy Hybrid Inverters
1

Our system comprises PV, GE HV battery and GE 3Ph inverter. Monitoring of the grid supply is done via CT clamps and the dedicated energy monitor (GEM630) which then feeds data back to the inverter via Modbus.

I realise that as the inverter runs in constant parallel with the grid there is always going to be a small and varying import/export of power with the grid going on during normal running as well as short peaks where a large resistive load (kettle/oven/hob) are switched on and it takes the inverter a moment to ramp up the supply.

In the perfect world the inverter and grid would run completely balanced with net zero delta but practically that will never happen. Given the way the electricity supply tariffs work you pay for the ( even smallest ) import but get no credit for export.

I’ve been monitoring this delta and it is often 10’s of Watts being imported. Circled areas below.

Note – The other peaks are as a result of large loads kicking in. The sampling period is 60s so looks worse than it actually is.

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As verified by the electricity supplier meter, over 24 hours this creates is a cost of ~£0.50 which over the year would be a cost in the order of £200.

I would like to be able to offset the zero point such that there was more of a bias towards export. I accept this is effectively ‘wasting’ energy but it is better than needlessly paying for energy.

GE support tells me they have no control over this particular parameter which is a shame. My other thought was to use the CT Energy monitor to do the same but the installed model can’t and I’ve not found an alternative.

Any thoughts? I can’t believe I’m the first person the ask the question though!

2

You should be able to get paid for export - who is your energy supplier ?

Yes, I had the same suggestion. But my system (gen-3 hybrid) responds pretty quickly to changes in demand. Over the summer, I’m exporting surplus most of the day, so it’s hard to provide data, but looking at half-hourly readings, it rarely amounts to 1Wh per half-hour.

I think some of the older inverters were quite slow to respond. The newer ones are much better. Not that this helps you very much, but you could ask GE if there’s a newer “fast-response” firmware available or planned for your model.

(I think the 3-phase inverter is quite new? Perhaps the firmware is not yet fully featured ?)

3

I suspect there maybe some anomaly with the import measurements so this is throwing the way the inverter is performing. That said my supplier is octopus and I’m on the octopus intelligent go tariff. You don’t get paid for export but you get a great rate on import including charging batteries.

4

with Octopus Intelligent Go you can (as well at the same time) sign up for Outgoing Octopus 12month Fixed (or similar Octopus plan). i currently pay 7p for overnight import, 24.54p for daytime import, and Octopus pay me 15p for any export (24/7). I don’t do it, but in theory, import 3kwh from 1am to 2am into the battety (cost 21p) and then reexport the same 3kwh from 2am to 3am (& get paid 45p). 20p plus in the bank :rofl:. What i do want to do is charge battery each night, then discharge to grid excess battery energy afternoon/early evening (leaving just a few kWh to run the house thru to 11:30pm). Also per other post, if i get a proper controller, ensure house is exporting a few watts minimum all day to avoid the +/- 30w problem when the battery is trying to balanced supply and demand at zero. Amazing the GE don’t provide this option.

5

Agree - to be able to ‘bias’ the energy flow towards import or export depending on your personal preferences would be very useful.

Update on my specific problem - it turns out that the cabling between the CT’s and the GEM360 monitor should NOT be extended as this introduces errors in what the inverter thinks is happening with grid supply. Installer is due back to rectify!