Posted by: @transparent

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Posted by: @graeme

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I am not sure how realistic it is for most folk to be off-grid?

Realistic in terms of price?
Or because of practical arrangements to have a storage battery installed?

What you are suggesting doesn't seem to be off-grid, but rather balancing the grid by using home - batteries. Storing excess grid power in people's home batteries *is* better than wasting it. But this *does* need a connection to the grid.

Within a year I produce 150% of my electricity need. My home battery is 11kwh which balances my daily usage and balances day to day usage in summer. But I also export continuously to the grid for 8 months of the year. For the remaining 4 months, I import during the night for usage during the day. Although I am (currently) more than self-sufficient - I need the grid to balance summer - to winter. To truly disconnect from the grid, I would need a 1000 kwh battery!!!

So in terms of my OP - I am not (normally) permitted to increase self-production on my grid-connected power circuit. There is nothing to prevent me, however, from having an *additional* off-grid power circuit. If using PV's, I still have a problem of having lots of power during the summer and not enough during winter. If used simply for powering a heating element, there is no real need for a battery within a days usage - and just silly to think of it for time-shifting across seasons. Sizing is important - because it is not connected to the main house circuit, any spare capacity is just wasted (though some must be expected). The heating element is not an issue - but powering the thermostat is. Using low voltage/wattage, can make the thermostat ineffective - resulting in blowing up your cylinder. Not pleasant. The Austrian heating element I mentioned is designed for its thermostat to be self-powering direct from panel.

But your answer made me question whether my existing system is already being "clipped" and an additional battery may be beneficial. Certainly any move away from gas space heating in winter would need additional capacity.

Thanks

Graeme

Posted by: @graeme

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What you are suggesting doesn't seem to be off-grid, but rather balancing the grid by using home - batteries. Storing excess grid power in people's home batteries *is* better than wasting it. But this *does* need a connection to the grid.

Yes, I agree that my terminology doesn't embrace 'off-grid' in the way that it would be perceived by a crofter in Scotland, for example.

I'm suggesting that the home is supplied by a storage battery, but that the grid can be used to re-charge that battery when conditions for that are favourable.

Your grid export is constrained, regardless of external fluctuations.
Whereas I'm suggesting that recharging from the grid should be dynamic, responding to external conditions:

• price per kWh
• energy-mix
• excess generation within the same locality

Posted by: @graeme

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For the remaining 4 months, I import during the night for usage during the day.

And that is commonly the case.
The reduced night tariffs are there to keep the Gas Turbine plants operating in Combined Cycle mode.
It's an artificially low price, which adversely affects wind-farms whose output gets curtailed.

But that day/night balance will gradually change as more EVs account for road traffic.

You don't need to have a completely separate off-grid system, incidentally.

Some inverters (SunSynk for example) can limit grid export to the grid within the figure stipulated by the DNO,
but also run the house from a battery.
During a grid-outage, the house remains supplied with electricity.

Posted by: @transparent

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Yes, I agree that my terminology doesn't embrace 'off-grid' in the way that it would be perceived by a crofter in Scotland, for example.

"Off-grid" means "off-grid", whether it is in the Highlands, Berlin or Tokyo. My original post is about designing a system not connected to the grid in any form. It can have advantages such as not being tied to 240v AC and thus, in some circumstances, does not need an inverter. My initial difficulty is that the Austrian Kit is not sized for UK cylinders.

It may be possible to get someone to make an adapter or alternatively purchase a Scottish-made but Euro-sized Cylinder;

ACV.COM "https://www.acv.com/gb/technology/cylinders"

High-Performance Cylinders for Efficient Hot Water Solutions
- ACV

Cheers

Graeme

 

 

In conversations with engineers in the UK electricity supply network, they use the term 'off-grid' when the 240v AC is not synchronised to the 50Hz of the grid.

The reason I needed to mention SunSynk is that their inverters have two 240v mains ports, one of which operates unsynchronised during a power outage.
AFAIK they are the only G99 Approved Supplier who offers such functionality.
G98 would normally prohibit such operation under the 'anti-islanding' requirements.

The ENA also recognises their particular implementation of 'export to grid' as being capable of limitation to whatever the DNO stipulates - including 'zero export'.

Those accreditations for installation in the UK would appear to be unique.