Storage Heaters

[Joeboy]

I think you might be surprised at the heating profile (best way I can think to say it) compared to GCH? No peaks & troughs in temps in house.

That's one of the things that struck us about using a heat pump as well. A few things got us there on the journey. Replacing the open chimney with a stove, removing all the down lights in the bedrooms which connected directly to the cold attic. And then the heat pump.

Good to read its not just me! I had given no thought or value to the benefits of slow heating through the night, it is a very pleasant feeling. SWMBO clocked it straight away. GCH is jagged in comparison.

[Bugtownboy]

I’ll go with the slow heat thing - don’t have SH, but the WB(s) are still very warm to the touch in the morning and all the internal walls (apart from one stud in the bathroom ) are solid. All pressed red brick gives a good degree of thermal mass.

It’s a gentler, enveloping warmth that just seems to be there - presume you get the same feel with the SH ?

With our insulation improvements, should see a notable difference this year.

[Oldgreybeard]

Slow heating does seem more comfortable. Our heating is a heat pump and UFH, and the UFH is only downstairs, with the pipes set deep in the floor slab. The slab is very well insulated from the ground, but takes ages to warm up. Once warm it works a bit like a storage heater, as it's about 15 tonnes of warm concrete, gently giving off heat through the floors.

[Andy]

You could probably get there with a modulating gas boiler sized correctly. But most engineers don't seem to know or care to install them. When we arrived in our house they installed a 22kW boiler. The most we've ever used is 12kW at -14ºC. So it spent most of its short life cycling. It broke after only 4 years.

RE: the 100% efficiency of electricity. It is still better to burn it in the house at 70% unless your electricity is renewable. The conversion rate from gas to electricity is only 60% at a modern turbine. Then there are significant losses in the power lines 8-15%. So if you are heating with electricity it does depend on where it is coming from. I guess if you are looking at the grid on a day then you need about 23% renewables to be better off using the storage heater. Although if the gas is fired up because everyone is using storage heaters then maybe it is better to burn it directly in the home *shrug* Its certainly not an easy answer

[Joeboy]

I’ll go with the slow heat thing - don’t have SH, but the WB(s) are still very warm to the touch in the morning and all the internal walls (apart from one stud in the bathroom ) are solid. All pressed red brick gives a good degree of thermal mass.

It’s a gentler, enveloping warmth that just seems to be there - presume you get the same feel with the SH ?

With our insulation improvements, should see a notable difference this year.

We put the last log on the WBS at 20.30 last night and there continues to be detectable heat from the storage bricks at 10.00 today. Only just but its there. 13(elements)x4x7.5kgs(bricks per bank)=390kgs+the WBS storage part. How'd that happen!! 650kgs active thermal mass.
On the different efficiency aspect. I will wait until year end and see how the consumption figures look. Its the only way I can be accurate for my set up.

[Oldgreybeard]

We put the last log on the WBS at 20.30 last night and there continues to be detectable heat from the storage bricks at 10.00 today. Only just but its there. 13(elements)x4x7.5kgs(bricks per bank)=390kgs+the WBS storage part. How'd that happen!! 650kgs active thermal mass.
On the different efficiency aspect. I will wait until year end and see how the consumption figures look. Its tge only way I can be accurate for my set up.

Just been doing some rough sums to compare storing heat in concrete versus storing it in iron oxide bricks. Storage heater feolite bricks have a specific heat capacity of about 920 J/kg/°C, magnetite bricks are a bit lower at 752 J/kg/°C. Concrete has a specific heat capacity of about 880 J/kg/°C. Using these numbers, your 390kg of storage heater bricks will store around 358.8 kJ of heat for every 1°C they are above room temperature.

After a bit of digging around I found that the bricks in a storage heater are heated to around 660­°C (from chapter 4 in this paper, worth a read: www.esru.strath.ac.uk/Documents/MSc_2013/Becerril.pdf ).

Assuming that storage heaters need to stay around 40°C above room temperature to still give out useful heat (like a radiator would), then with a room temperature of 20°C storage heaters could work over a range of around 600°C. 390kg of feolite bricks with a 600°C working temperature differential would store about 215.3 MJ of useful heat. That's equivalent to about 59.8kWh, so quite a lot. Magnetite bricks would store about 18% less heat.

Our 15 tonne concrete floor only runs at about 5°C above room temperature, but it does have a much greater area to give off heat. It stores about 66MJ, or about 18.3kWh, so a great deal less than your storage heaters.

Be interesting to strip down a load of old storage heaters and re-build them into one big unit, with loads more insulation and a fan to blow air through the bricks and out, a bit like the old GEC Nightstore, but with ducted air heating. Could work well with MVHR, just diverting the fresh air duct through the bricks.

[marshman]

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[Oldgreybeard]

Be interesting to strip down a load of old storage heaters and re-build them into one big unit, with loads more insulation and a fan to blow air through the bricks and out, a bit like the old GEC Nightstore, but with ducted air heating. Could work well with MVHR, just diverting the fresh air duct through the bricks.

Now that is an interesting idea !

Need to reinforce the ceiling joists (the MHRV fan unit and main duct runs are up there) before dumping a few 100 kgs of heat store up there . Not sure how much excess PV I will have to warm it up when we get to the time of year when it will be needed, will monitor it this year and proceed from there.

We only need around 20kWh to 25kWh per day for heating, so could get away with about 160kg of bricks, less if it's just for a bit of supplementary heating. Be neat if the insulation could be improved so that heat could be stored for a few days, too. Might be possible to then heat the bricks up on sunny days and store it until needed on cold days, perhaps.

[Joeboy]

Be interesting to strip down a load of old storage heaters and re-build them into one big unit, with loads more insulation and a fan to blow air through the bricks and out, a bit like the old GEC Nightstore, but with ducted air heating. Could work well with MVHR, just diverting the fresh air duct through the bricks.

Now that is an interesting idea !

Need to reinforce the ceiling joists (the MHRV fan unit and main duct runs are up there) before dumping a few 100 kgs of heat store up there . Not sure how much excess PV I will have to warm it up when we get to the time of year when it will be needed, will monitor it this year and proceed from there.

We only need around 20kWh to 25kWh per day for heating, so could get away with about 160kg of bricks, less if it's just for a bit of supplementary heating. Be neat if the insulation could be improved so that heat could be stored for a few days, too. Might be possible to then heat the bricks up on sunny days and store it until needed on cold days, perhaps.

I thought of this t'other day. It would be great to build but sadly I don't need it. I have also given some thought to increasing the mass so end up with a 2:1 ratio of bricks to heating elements? Could build it in such a way that you could have cassette type elements pre encapsulated/entombed in a set of bricks that can be slid in or our when the element fails. Bind the main sarcophagus with liquefied fire cement et voilà! Ready to be insulated. Thanks for working out the potential kWh storage OGB . I Stacked the WBS for later this afternoon and it has taken off on its own. Good to get some heat into the other 250kgs of thermal mass/storage brick at 300 degs.

[chris_n]

Be interesting to strip down a load of old storage heaters and re-build them into one big unit, with loads more insulation and a fan to blow air through the bricks and out, a bit like the old GEC Nightstore, but with ducted air heating. Could work well with MVHR, just diverting the fresh air duct through the bricks.

Now that is an interesting idea !

Need to reinforce the ceiling joists (the MHRV fan unit and main duct runs are up there) before dumping a few 100 kgs of heat store up there . Not sure how much excess PV I will have to warm it up when we get to the time of year when it will be needed, will monitor it this year and proceed from there.

We only need around 20kWh to 25kWh per day for heating, so could get away with about 160kg of bricks, less if it's just for a bit of supplementary heating. Be neat if the insulation could be improved so that heat could be stored for a few days, too. Might be possible to then heat the bricks up on sunny days and store it until needed on cold days, perhaps.

When I was a child we moved into a new build ( early 70's ) that had a system that was ducted air from a large central storage heater. The unit must have been close to 2m tall, 0.8m wide and about 1m deep. Don't know any details as i was only coming into my teens at the time.