Massive battery + electric boiler

[GarethC]

Starting new thread as felt bad hijacking "Home battery without solar" thread. Thanks Stinsy et al for prior input.

Decarbonising the heating and hot water systems for my victorian home is a PITA. An ASHP would be my best bet, but would be expensive, even post grant, disruptive, given I'd need new radiators and a hot water cylinder, and in all probability might struggle to heat my home well.

If I installed a 60kWh battery, charged using off-peak electricity, then swapped my combi boiler for a, say 26kW electric boiler, how would that be as a strategy? Realise would need power supply to be 3 phase, but would be cool if battery could instead supplement single phase when required, saving need for upgrade. Standard inverters wouldn't supply that kind of output either, would they?

Sorry this is probably all half baked....

[Krill]

If a 26kW electric boiler is expected to pull straight from a battery, don't you need to get inverters which can provide that level of power (plus the rest of the house load)? And then don't you need to size the battery to manage that level of charge, ie wouldn't you be looking at something closer to 100kWh worth of storage?

That would be massive. Regardless of hte cost, just how much space would it take?

[spread-tee]

You really want to do a proper heat loss calculation for your house, or at least look at your previous heat demand to work out the kind of storage you need. 60kWhr isn't going to heat a leaky Victorian house for long when it is freezing outside, a few hours at best. Personally I would think long and hard before ditching a gas boiler in a Victorian house. Obviously investigate all the insulation options before doing anything.

Desp

[GarethC]

Ah yep. We're pretty damn parsimonious when it comes to gas usage, only heating our home to about 16 degrees, but having just checked even we hovered around 100kWh of gas per day in December and January last year. Even allowing for boiler inefficiencies, we'd probably need a 100kWh battery to cover our total daily usage, and that would be maintaining our -relatively- energy frugal lifestyle. Lots of space, expense and need for an extra punchy inverter.

As Stinsy pointed out, would probably need a heat pump anyway to reduce the elecricity demand to something far more coverable by a battery, but then I'm back to lots of disruption and expense anyway.

So probably still going to go down the ASHP route. Not prepared to burn gas for much longer.

[AGT]

Do you have space ! plant room for all this equipment?

[Gareth J]

Using batteries to store energy you want to use for heating is bonkers. Economically and environmentally. Especially resistive heating with electricity you've bought.

There are so many options for thermal storage that you could explore; water, phase change, high temperature, heat pumped geothermal, sand, earth, etc ..... All make more sense for thermal storage than storing energy in electrochemical batteries for it.

[GarethC]

Yes probably absolutely right. I just wondered if using a -single- storage mechanism for low cost, low carbon off peak energy that could provide for heat -and- electrical load (very big battery) -might- be better than separate storage mechanisms for heat and leccy (battery + hot water cylinder + potentially storage heaters). Especially as non-phase change thermal storage has quite low energy density (iirc) and high standing losses.

I think the conclusion is almost certainly not unless perhaps you have a heat pump to make far better thermal use of the electricity.

Although I'm not sure I entirely agree using time shifted off-peak electricity for direct electric is that bonkers. Currently our overnight (in Scotland) electricity is particularly low carbon and increasingly, given grid constraints, curtailed. Potentially better to use it than lose it perhaps, but would need further analysis.

[Stinsy]

I think you need to bin the idea of mahoosive battery and resistive heat! It just isn’t practical/economically viable.

[GarethC]

I think have!

It's not so different from using storage heaters though, is it? And while I think many on here have had a lot of success buying second hand ones, am I right that not many have shelled out for new ones? I -still- don't understand why they cost so much...

[chris_n]

High temp heat pump to reduce need for changes to your existing wet system and a good look at air leakage with a bit of insulation thrown in should do it. The only reason normal heat pumps don't work in leaky buildings is the air is changed quicker than you can warm it so you are always heating cold air. This problem is mitigated somewhat by both increasing heat pump temp and reducing air changes.