Home Generation Part 2

[Conan_the_Librarian]

Long Post, sorry!

Given the cost of electricity, even with the capped Cap, now that I am on a variable tarrif, living in the countryside and no mains gas I'm moving forward with my microgeneration projects.
I already have 2 X PV arrays on my roof; both monitored in real time and I have been logging loads for the last couple of years. Western power has limited me to a maximum of 4Kw of PV based on the ability of the transformer on a pole near the house which supply's our little hamlet. While it's a bit of a shortsighted restriction as it's based on the 38 customers who share the transformer, it's one I can't get around. Reasoning failed! The fact that 32 of the customers live in park homes that aren't allowed PV or wind generators as a T&C of their leases and 4 of the houses are surrounded by trees or don't have a roof suitable then the last two who both have PV are still limited to 4Kw systems.

The house resting rate (night time) is, on average, 500 watts (low 320w to high 655w). When we've been out on a sunny day, the maximum the PV has ever exported is 3.25Kw. However, we still only generate 35% of the power we use and export 27% of the power generated, at 4.5 per kWh that is mildly annoying me!
Adding batteries isn't economical on the PV because we don't generate enough in winter to keep them topped up.

That's were the stream that runs through our garden comes in. Having done the maths over the last year the water throughput says a minimum of 300w in the summer and 1Kw in the winter. I have a turbine and waterwheel design and a generator capable of 1.5Kw. I've identified a charge controller and battery system with 9.6Kwh capacity but I'm stuck on how to get that capacity to the house and not out onto the grid.

A grid tie inverter would run at maximum based on the output from the batteries. That's ok when the house is demanding that load, but when it isn't, like the PV it will push it's full capacity out to the grid. With a 4.5Kw inverter that would flatten the batteries in a little over 2 hours. More in the winter if 1Kw is being generated but still a downward curve.

What I'm after is something to tell the inverter what the household load is and to only supply that much. Still being attached to the grid, if we exceed the inverters maximum the power is supplied by the grid.

Anyone any idea how to do this please?