Using a Victron Multiplus 1.6kVA system with 2x 110Ah 12V Gel batteries was remarkably cheap and simple. The whole lot came to just over €1k and took ~1h to set up, mostly setting jumper switches.
It keeps the pellet boiler, circulation pumps, backup gas heaters and control gear going all night when necessary. The automatic switchover from mains (<20ms) is so fast that none of the PLCs, Arduinos, Raspberry Pis or heating equipment notices. Upgrading its capacity simply involves plugging in another 2x batteries (it's a 24v unit) in parallel.
The only thing I wasn't thrilled about was that it doesn't protect against power surges, and a storm fried the boiler logic board AND the gas valve in the backup heater simultaneously in midwinter. (Victron unit was fine though!) Lesson learned.
A similar installation in the house could easily power our (non-electric) central heating system, LED lighting and wifi for plenty long enough to stay civilized, and we're being prepared for 2 hour rolling blackouts here this winter.
Even if you do have a home battery system that can generate its own sinusoidal AC wave, you still need an (automatic) transfer switch to disconnect your home from the failed grid, otherwise your home battery might be attempting to power the entire (local) grid which of course doesn't work.
and some random line worker may think there's no electricity flowing when there is.
(But yes, backfeeding the grid during an outage is dangerous and highly against code.)
If you have lines in an unknown state, step 1 is to put them in a known state. For power line work, this involves grounding all the phases and neutral together at both ends of the section you intend to work on. Good luck ringing a dead short with your home inverter/generator/etc.
Is that conceptualisation correct?
What happens is you have say a conductive (iron rich) top layer. Is there still the potential to dangerously energise the ground? I assume so because that's basically what water and electricity does?
Grounding provides an alternate path for the flow of electricity, so if a wire comes loose and ends up touching a copper pipe or something the current gets routed into the ground rather than into pipes or flammable wood or something.
Dispersal over an area isn't directly the goal, but it helps. By dispersing the current into an extremely large object, you don't really have to worry about the object building up a charge to the point where you can't flow current into it anymore.
Yes, you can dangerously energize the ground. You can dangerously energize almost anything with enough voltage. E.g. a Tesla coil has enough voltage to conduct through air. Don't try to test it (obviously), but I don't think a standard 110V house grounding has enough voltage to dangerously energize ground over any significant distance.
Efficiency.
You can store excess energy from local microgeneration, particularly solar, that can be used later. With our current pricing model in the UK, that is several times cheaper than selling the excess power to the grid for a token return and then paying full price to have the same amount back from your mains supply later.
Some systems can even be configured to charge their battery from the mains at quiet times (when, again in a typical UK pricing model, the cost-per-unit can be much lower) if there isn’t enough local generation to fully charge it, for example in the middle of winter.
Most people unfortunately can't take advantage of this, but most battery packs are also suitable for off-grid use.
https://www.utilitydive.com/news/utility-scale-battery-stora...
https://www.ny-engineers.com/blog/two-ways-to-use-grid-tied-...
Things like https://www.hawaiianelectric.com/products-and-services/custo... note the https://www.hawaiianelectric.com/products-and-services/custo... - the CGS Plus and Smart Export involve use of a battery that isn't necessarily home power sufficient.
In Europe you should check if grid-independence is even legal. In some places it is not.
I suspect the dividing line is voltage? >50v systems in cars are treated differently, so maybe the same for houses, you probably don't need that much for lighting anyway.
Between that experience and the environmental benefits, we were already discussing installing a big solar panel and battery system at our home with local suppliers, even before the recent dramatic price rises and the bizarre news that in the 21st century there’s a credible threat of rolling blackouts here.
I can tell you from first-hand experience that getting such a system professionally installed and commissioned is likely to be a long wait and then cost a small fortune. Systems that can keep the household power on when the mains supply cuts out can require jumping through extra regulatory and consent hoops before anyone installs the new gear alongside a mains supply. You’ll also have fewer and often much more expensive options for the hardware than systems designed for efficiency/environmental benefits but not resilience to outages.
Of course it might still be a very good idea to do this, if you’re lucky enough to meet the practical requirements and have the money to do it. But it’s definitely not going to be some DIY system you can build for £1,000. More like £10,000–20,000 and several months of waiting for an installation date, at least in this area.
Having to work out what is protected and for how long gets old pretty quickly, though. So do alarms going off in one room or another if the mains supply cuts out in the middle of the night, when everyone is (was) probably sleeping anyway. Or occasionally annoyances like waking up to find a big job scheduled to run overnight hasn’t actually run because the system that should have run it executed a controlled power-down after an earlier power outage instead.
In contrast, a relatively large but domestic-scale battery system can easily store 10kWh or more of usable energy these days and provide it to anywhere in the building. That’s enough to run most of our house for 24h, as long as we avoid using very high consumption devices for extended periods or running too many of them at once with peak consumption levels higher than the equipment supports — a huge upgrade compared to the small-scale alternatives.
Maybe that’s the simplest solution. Every important appliance has its own UPS. Small UPS’s like that require no setup or permits and just kinda work.
I wonder if you could use one to power a fridge..
It’ll use solar when available and grid for the rest.
Since it’s inverter drive, it can use whatever amperage comes in, even if it means running a 5% duty cycle and do at least something. The contents are the battery!
In California or Texas you could recharge with solar, but in Europe, solar during winter is basically useless. I'm at 54N and in June my system generates 1400kWh, in December if I get 90kWh I'll be lucky.