Idiot's guide to a self build battery

[Joeboy]

I've done a trawl of the site for a couple of hours and will provide an update soon. Its facilitated the adding of more members to my list, 96 members now out of the total membership of 249.

Batteries will all be lumped together and shown as gross because if I attempt to do a useable alteration, I'll have to keep doing maths and it will get complicated as folk alter their systems. I will also not include any EV battery storage, maybe I'll add that as a separate category some day.

Hot water and thermal storage data collection will be patchy and understated as not many add it to their sig or specify how much of it they have. Had a similar issue with Solar Thermal in the past as there is a lot of it out there, but few know how much it generates, so the info is less meaningful.

Impressive Nowty. Good separation of streams too. Interesting to see how it plays out. Cheers!

[Oldgreybeard]

Just wondered, how many sheets of PB would acually warm up due to solar gain and by how much (direction of window, size etc all make this more interesting), since as soon as the PB is warmer than the air in the room it will start to lose heat, don't they drop back to room temp well before night? - obviously they will incerase the thermal mass of the room so keeping it warmer for longer into the night though. How much difference does wall colour make? In our case, SWMBO decided all walls & ceiling were to be white (or at least so close as makes no difference), the PB does not feel to warm up, but anything dark left in front of a window certainly does. Since our windows are double/triple glazed heat it supposed to be retained eather than reflected out.

Just out of curiosity, how big is the house? Ours is 225m2 and I only used 300 sheets of PB (250 x 12.5mm 2.4 x 1.2 standard 25kg each, and 50 soundbloc same size but 38kg each) that included the ground floor ceiling being double boarded where there was a room above (100m2).

I did play around with the effect of colour on heat absorption, definitely makes a difference, but not as big a difference as I expected. Comes down to the infra red reflectivity to a large extent, and that's closely related to emissivity. Turns out that matt white painted walls are only around 10% to 15% less good at absorbing long wavelength IR than black painted walls, bit of a surprise, TBH. For example, a black soot finish has an emissivity of around 0.98, whilst a white painted surface has an emissivity of about 0.84. For comparison, a mirror finish, as seen on IR reflective glass, has an emissivity of around 0.05.

The heat absorption of the plasterboard depends mostly on the air temperature increase inside rooms that get some solar gain, so not just direct heating from the sun shining in on walls. A good example is our spare bedroom, that gets a lot of early morning sun. This room can easily be two or three degrees warmer for a few hours in the morning, and some of that heat gets absorbed and stored by the plasterboard on the walls and ceiling, then given out later in the day as the sun moves around.

[Joeboy]

Yeah yeah, if you have your own land that you coppice I'd buy that but in general, no chance, and for a list like this? Sure, save the data, it doesn't mean much. It's like when nurses way peoples faeces to check how much food has been absorbed for people with eating disorders, why does anyone really want to have that data?

Can't say I appreciate your yeah yeah attitude or your negativity. Also it's weigh not way and I didn't know that was a thing. Each to their own though.

I'm sorry for the spelling mistake, I can see how upsetting that is to you.

It doesn't change the point that creating a list of all the known values (such as UFH on a known volume of concrete) is going to be more accurate than including in that list unknown volume of bricks.

I'm not sure where you're going with the sarcasm after the dismissive words. Be more accurate in your meaning though in the stuff that matters (unknown volume of bricks?) I am not upset but do hope that people (including you) who take the time to contribute here do it at a reasonable level and respect the various ideas floated. 'Yeah yeah' isn't good enough, fair enough?

[Krill]

Can't say I appreciate your yeah yeah attitude or your negativity. Also it's weigh not way and I didn't know that was a thing. Each to their own though.

I'm sorry for the spelling mistake, I can see how upsetting that is to you.

It doesn't change the point that creating a list of all the known values (such as UFH on a known volume of concrete) is going to be more accurate than including in that list unknown volume of bricks.

I'm not sure where you're going with the sarcasm after the dismissive words. Be more accurate in your meaning though in the stuff that matters (unknown volume of bricks?) I am not upset but do hope that people (including you) who take the time to contribute here do it at a reasonable level and respect the various ideas floated. 'Yeah yeah' isn't good enough, fair enough?

Actually I am being sincere when I say I can see how upsetting it is to you. Thank you for pointing out the spelling mistake. FWIW if I was being sarcastic I would have used /s.

The data which is tabulated into a useful form is useful, but most of all as advertisement, or dare I say in some peoples eyes, propaganda. It can be useful as discrete information (when available in the constituent parts such as x amount of PV at x azimuth at y latitude, or p kw battery storage in a household which uses q kwh/day on average etc). One example is that a newcomer to the forum could understand, as a lyaman, what apatations they can make that will support them in these aims. What is less useful, with the thermal storage, is how people interpret it when it is not clear what it is, or how it is used.

[Joeboy]

I'm sorry for the spelling mistake, I can see how upsetting that is to you.

It doesn't change the point that creating a list of all the known values (such as UFH on a known volume of concrete) is going to be more accurate than including in that list unknown volume of bricks.

I'm not sure where you're going with the sarcasm after the dismissive words. Be more accurate in your meaning though in the stuff that matters (unknown volume of bricks?) I am not upset but do hope that people (including you) who take the time to contribute here do it at a reasonable level and respect the various ideas floated. 'Yeah yeah' isn't good enough, fair enough?

Actually I am being sincere when I say I can see how upsetting it is to you. Thank you for pointing out the spelling mistake. FWIW if I was being sarcastic I would have used /s.

The data which is tabulated into a useful form is useful, but most of all as advertisement, or dare I say in some peoples eyes, propaganda. It can be useful as discrete information (when available in the constituent parts such as x amount of PV at x azimuth at y latitude, or p kw battery storage in a household which uses q kwh/day on average etc). One example is that a newcomer to the forum could understand, as a lyaman, what apatations they can make that will support them in these aims. What is less useful, with the thermal storage, is how people interpret it when it is not clear what it is, or how it is used.

I appreciate the sincerity if not the accuracy, I'll leave your spelling alone going forward.
For thermal storage they can ask a question and engage with the forum. Bring their own ideas with them and spread knowledge. A good thing.

[Oldgreybeard]

What is less useful, with the thermal storage, is how people interpret it when it is not clear what it is, or how it is used.

Perhaps it makes sense for those with thermal storage to clarify how it's used. @Joeboy has been clear about the way he's using storage heaters, hopefully I've been fairly clear about how I use our floor slab as a storage heater (and our only form of heating) and our Sunamp phase change thermal store works just like a water filled thermal store, really. If anyone needs to know a bit more detail then the best bet might be to ask about it in a post, I'm sure we'd all happily chip in with a bit more info if asked.

[Moxi]

https://www.engineeringtoolbox.com/sens ... _1217.html

One of my favourite sites on the web with a wealth of information and guides, I thought the page linked above may help some people consider their own specific circumstances to get a feel for what is, or indeed, what is not, possible for them.

As I may have noted earlier, I think? after we had the EWI fitted to the cottage some years ago the whole place became instantly more comfortable to live in and over time this got even more noticeable and cosier.

The reason for this are no doubt numerous, but the first was the obvious reduction in drafts afforded by the EWI "blanket" that was thrown around the walls eliminating many many draughts and leaks in the structure.

The second appreciable benefit took longer to identify, and this was the thermal mass effect as with less energy escaping, the walls slowly acquired a new base temperature.

I hope people find the linked calculator of interest.

Moxi

[Oldgreybeard]

That's where I got the data for energy density of materials from that I quoted in this post recently:

Not sure what's really meant by thermal mass, TBH, it seems to be something often quoted but quite hard to really define. I think the key thing to know is the heat capacity, i.e how much useful heat energy is stored in any particular thing, either in Joules or Wh, perhaps. The mass is a bit irrelevant, I think, as energy density only uses volume and energy. For example, concrete stores about 2,122kJ/C° of heat per cubic metre.

You don't need to know the mass of a cubic metre of concrete to work out how much useful heat it contains, you only need to know the difference in temperature between the volume of the lump of concrete and the room temperature.

It's easy to measure or estimate the volume of something and easy to measure its temperature, so just using the energy density for common building materials allows the useful heat stored to be quickly calculated. I've listed below the energy densities for some common materials (taken from the Engineering Toolbox site). To convert these numbers to kWh/m³.°C divide them by 3600:

Brick = 1,813kJ/m³.°C

Granite = 1,896kJ/m³.°C

Concrete = 2,122kJ/m³.°C

Fireclay = 2,200kJ/m³.°C

Cast iron = 3,889kJ/m³.°C

Water = 4,190kJ/m³.°C

Very useful site in general for getting material properties and other stuff.

[Moxi]

Brilliant site,

Usually, my go to place for inspiration and information on all sorts of stuff, I hadn't spotted the likeness of the data you posted before and the table in the web page OGB, sorry.

Moxi

[Oldgreybeard]

Brilliant site,

Usually, my go to place for inspiration and information on all sorts of stuff, I hadn't spotted the likeness of the data you posted before and the table in the web page OGB, sorry.

Moxi

My fault, I should have posted the link directly, glad you thought to post it. It is a brilliant site, and pretty much my go-to site for getting material data. Always seems to be a lot more accurate than some other sites, too.