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Just doing a heckin' science to figure out my solar system requirements... How much battery capacity do I really need? (No, really -- I'm asking!) (thelemmy.club)
submitted 6 months ago by to c/solardiy@lemmy.world
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I'm planning to cut my grid connection and go full off-grid. Which raises the question of how much capacity I really need. And what you see here is me trying to answer that question based on ~51,000 5-minute data points of usage data my power company provided to me, complete with custom-made python script to parse all that data and pretty charts! (Yes, I have 6 monitors. And this kind of shows why.)

And what I'm really torn about now is how much battery capacity I need. Should I get enough to cover the absolute worst case scenario (~66kwh) or is something closer to my average overnight usage (~20kwh) acceptable?

Not the absolute end of the world if the batteries run dry and I need to temporarily supplement with generator backup, I suppose. Nobody is life-or-death depending on any electrical appliances here, and even on the coldest days, waiting a few minutes to go start a generator isn't a huge deal.

But definitely would like a word from the wise about how much battery capacity I really need. And also how much solar panel wattage I need, I suppose.

screenshot of data processing for solar system design
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[–] 2 points 6 months ago*

Well we already made up our minds that we were going to externally insulate before we moved in. It may be more expensive but there's a lot less mess and upheaval when compared to internal insulation.
If we did internal insulation then we'd have to rip out all the plasterboard/lath and plaster etc, rejig the electrics etc, insulate, refit plasterboard and plaster. Whereas with external then all I have to do is clean the render off and reroute the guttering and downpipes.
Plus I'm doing it all myself. Mostly to save money, but also because where we are there's not many people around who do the things we need doing.
Example: when we moved in we had an oil boiler but no heating yet the quickest a plumber could get out to us was about 2 or 3 weeks, and that was doing a favour for the farmer who we bought the house off.

Now that type of external insulation...?
Like I said, our house is all solid walls but only about 30% of it is the original sandstone that they dug out of the ground to build it. The rest is high density concrete blocks.
On the concrete part of the house I'm probably going to use the standard EPS. I'm unsure whether to use standard adhesive or use the special foam adhesive. Or a mix of both. But I'll definitely be using plastic fixings to prevent as much thermal bridging as possible.
On the original part then that's a bit more tricky because the walls have to 'breathe'. There are a few things I can use such as wood wool or mineral wool. Finished off with lime render of some sort.

We are also going the MVHR route. Which will keep the humidity down etc.

There is another thing called geocell insulation
https://unitylime.co.uk/shop/brand/geocell/geocell-foam-glass/
Apparently that stuff could go in between the plaster and wall, and apparently it doesn't stop and condensation but it does keep the heat inside. I've only just heard of this stuff so I don't know much about it. I learnt it from a guy who sells it when I was at a Self Built show a free mouths shop. I will do the research on it at some point, and if it does allow the walls to breathe then I'll also get loads of that and pump it into my walls. Fingers crossed.

What are your thoughts?

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