I think this is an interesting design tension. On one hand it's simple and cheap to make. On the other, electric resistance heating isn't the most efficient, even with the storage mechanism (and a lot of places don't have cheaper power at night).
Here in the UK you tended to see these heaters in rural areas away from the natural gas mains. They were used with special Economy 7/White Meter electricity meters that provided much cheaper electricity over the night hours. The Economy 7 meters had clocks in them that you had to set for night rate hours that varied slightly by area. I tend to associate them with the 70s and 80s (before the grid interconnects with Europe allowed us to sell surplus base load electricity from the old nuclear reactors and coal stations).
No new Economy 7 meters are being installed now but smart meters can have an Economy 7 tariff set to achieve the same outcome. Storage heaters are still sold.
Awesome, thanks for making my hypothetical concrete :-) A while back, I made some stepper motor automatic window openers to let in cool night air and try to cool down all the thermal mass in our place based on whether it was going to be hot the following day, and then closing them when it didn't help to have them open anymore, kind of a similar idea.
I wonder why you say this. Having actually had them, they're insulated and you can open/close vents as you choose. And weather is usually pretty predictable; when it's winter it's cold.
Oh look, the article even says this: "Today's storage heaters have such good insulation that the only heat coming into the room is from air being blown through the hot core by an ultra-quiet low-speed fan the length of the heater with the warm air coming out of the bottousually m of the heater at floor level - even when the core is full charged the outside of the heater is usually barely warm to the touch - and never hotter than a water-heated radiator"
I had storage heaters in a rented draughty flat in London and I loathed them. Mine were rather inadequate in really cold weather. In spring and autumn you need to be moderately clairvoyant (or keep an eye on the weather horoscope) because your decision tonight will determine whether the flat will be too warm or too cold tomorrow.
Ironically, with solar over-generation becoming the new normal in some parts of the U.S., it's going to make more sense to have "day storage heaters" rather than "night storage heaters".
We had these storage heaters when I was a young kid, they we ripped out in the mid 90s when the village got gas. My Dad kept the bricks from them though, and a few years ago used them to build a Pizza oven :-)
I wander if as we switch to "green" electric if we will see a reappearance of them. Controlled on timers and via the internet, electricity providers could schedule and stagger the times they are heated up to level the demand.
Heat pumps are ~3X more efficient and are hitting the sweet spot of economies of scale and incremental improvement. So, more likely would be water storage tanks powered by heat pumps, that store heat during the day (when temps are higher and solar power’s cheap), with release through the evening.
If there’s a neat thing about these old resistive heat storage bricks, it’s the use of a fan to deliver hot air immediately.
The efficiency only matters assuming electricity stays expensive and constantly priced.
If the economics of generation v storage work out that it's cheaper to overgenerate most of the time, efficiency isn't going to matter, demand shifting to when energy is cheap is going to be the key. So then it's a question of heat pump is battery storage v storage heater.
My electric only house used to have storage heaters. Just had a mini split air conditioner installed. It's much more efficient [COP], so should pay for itself pretty quickly.
I have some leftover solar panels and want to try connecting them straight to a (correctly sized) water heating element -> 50 gal container of water in my garage, and see if I get any meaningful heat in Fall/Winter. That would save the cost of a battery, charge controller and inverter.
If successful, phase 2 would to be to circulate that heat into the house.
Of course it's way less efficient than a solar water heater, but reduces a lot of the complexity/cost and potentially lets me dump excess solar.
Recently, people use micro-inverters to convert to AC mains at the panels, and current sensing to detect when their panels are producing more power than the house is consuming - if so, they turn on (1..n) resistive heating elements in their hot water tank to fully utilise the excess.
Another thing to ponder is a sand ‘battery’ as a power / heat sink - lower heat capacity than water but doesn’t boil at 100C so can absorb more energy.
I was thinking about a similar idea. I couldn't find a suitable DC immersion heater to connect directly. An off the shelf on-grid or off-grid inverter wouldn't have made sense either. A massive variac wouldn't be cheap. A purpose built inverter/mppt would be good but I'm not an electrical engineer so I don't know how to make one.
There are a ton of YouTube videos were people have tried the same thing. PV is vastly superior in cost and results compared to traditional Solar Water Heaters.
Night storage heaters are ideal when you have too much base-load available at night compared to use. So ideal to what they were facing in the 60s and 70s: a lot of nuclear power plants were being built that couldn't be regulated much (that improved a bit now). Electricity use was very low during night.
The issues and possibilities we are facing now are different: With heat pumps we can use electricity way more efficient than with resistive heating. When excess electricity is available doesn't follow a simple curve anymore but can be predicted only some time ahead.
At least in the UK, demand is consistently lower overnight (e.g. see https://grid.iamkate.com/) and wind output alone is close to meeting overnight demand on windy nights. So storing large amounts of cheap overnight energy can be very useful - especially if it means we can turn off heat pumps at peak times. In fact, in the UK we already have a scheme that pays consumers to not use electricity at peak times: https://www.moneysavingexpert.com/news/2022/10/octopus-ovo-e...
Upon moving to Dublin my wife and I had a storage heater. Horrible, horrible thing. Would spend all night getting hot, then spend the day trickling away heat and despite all our careful adjustments crapping out and getting cold around 6 PM, when we got home from work. They might have made more sense when more people were in their flat during the day.
As the article mentions newer models are a lot better insulated and only release heat on demand. My parents had one installed last year which allows you to set different temperature schedules throughout the day, and the front of the heater is barely above room temperature.
I've since built a home with a heat pump that works quite well, but that's good to hear! Does a storage heater still make sense considering how affordable air to air heat pumps are?
I imagine something like this connected to a heat pump and a resistor along with natural gas - and you pay the utility for BTUs and they decide how to heat (gas when it’s cheaper, switch to electric when that’s cheaper, use thermal heat storage to level out bumps).
Water has ~5x the heat capacity of brick. My first thought was a heat-pump water heater combined with radiant flooring. This way the heated water is stored in an insulated container until it is needed.
Yes, but the problem is that the hotter the storage water becomes, the lower the COP of the heat pump gets. The problem is one big tradeoff based on how cheap the off peak rates are, how much capital expenditure (oversized heat pump and water storage tanks aren't free), and how variable your day to day heating load is versus peak. Plus most people don't like capital expenditures.
I wish the original article touched upon the electricity rates. If you can rely on off peak rates being less than 1/4 of the on peak rates, then I can see this making sense. Otherwise it seems better to use electricity more efficiently, exactly when needed.
I've been scoping out this company for some time, my boiler is currently in good shape but would love to switch down the road.
They heat up water via HeatPumps to required temp during the day when outdoor temps are higher and electric is cheaper. Max water temp can change based off excepted nighttime temp.
I recently converted our house from gas to heatpump for HVAC and water. We were considering Artic Heatpumps, but then when it came time to make a final decision, we were talked out of Artic by the contractor. They recommended Mitsubishi for HVAC, and Rheem for water, with the argument that these companies will be around for a long time for parts etc. We have all kinds of problems with the hot water heater, and managing the waste cold air from that unit and not having enough heat to pull in from that utility room. I have to figure out some ductwork to eventually deal with the problem.
I really regret the choice, and wish I had gone with Artic with their integrated system for HVAC and water. It just makes so much more sense.
There are definitely not enough installers trained on heatpumps, and many just treat them as drop-in replacements for gas fired equipment, because that's what they know. It is rare to find someone who looks at the whole picture and also deals with the heat loss mitigation.
These considerations are part of the reason I replaced gas with gas - I’ll move to heat pump when I build a house so I can be sure I have it designed for it.
As it is a tankless water heater may be the easiest way to “fix” yours - or spend a big amount for a knowledgeable energy contractor.
I remember the website of one enterprising New Zealander, where he was using an under house water storage tank as a heat sink accessible by his heat pump!
For the storage heaters I had the 'bricks' seemed to be mainly iron oxide IIRC. Also I am struggling to believe water has that multiples of capacity over brick, do you have a ref?
Feolite
specific heat = 920.0 J·kg−1−1·°C−1,
density = 3,900 kg·m−3,
thermal conductivity = 2.1 W·m−1·°C−1.
maximum operating temperature 1000 °C.
Water
specific heat = 4184 J·kg−1·°C−1
density 1,000 kg·m−3,
thermal conductivity = 0.591 W·m−1·°C−1.
maximum operating temperature <100 °C unpressurised.
Brick has a heat capacity of 840 J/kg°C. Water has a heat capacity of 4182 J/kg°C. Almost but not quite five times as much heat capacity. Water has a staggering heat capacity.
This assumes a level of competence and conviction to lower energy consumption and bills that is definitely absent from any of the UK’s retail energy suppliers today.
When I worked at Kaluza (which was started by the founder of OVO and afaik is part of the OVO group) on smart charging EVs, the company was also running trials to smart charge storage heaters when energy prices were low (see https://www.kaluza.com/kaluza-and-glen-dimplex/). I never worked on this directly, but as a company we were really focused on delivering value to customers and helping them save money on their energy bills. I know Octopus is working on a similar system, so there is a group of people within the energy retail space that are looking to drive down bills.
It's understandable given the high profile collapses. In addition, stories like "UK energy customers receiving bills of up to £49,000 after Ovo takeover of SSE" [1] don't help at all.
In defence of smart meters, they allow half-hourly settlement, which was required for smart charging of EVs. I don't understand exactly why this was required, but we couldn't work with retailers that didn't have this in place.
I wonder if a larger central version of this would be better?
Overall heat loss would be lower, it could be an easier upgrade for homes with radiators, and could also serve hot water, at a wider range of temps than a normal tank type water heater.
> The device has been installed in the Vatajankoski power plant which runs the district heating system for the area. Low-cost electricity warms the sand up to 500C by resistive heating.. generates hot air which is circulated in the sand by means of a heat exchanger. Sand is a very effective medium for storing heat.. device could keep sand at 500C for several months. So when energy prices are higher, the [sand] battery discharges the hot air which warms water for the district heating system which is then pumped around homes, offices and even the local swimming pool.
Cool a big tank of water/ice using solar, so you can keep chiller aircon running overnight without using more electricity.
I think I've seen commercial versions of this (icebear?), but nothing domestic. In fact even domestic-sized chillers (for central hydronic cooling) seem rare.
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[ 4.2 ms ] story [ 117 ms ] threadNo new Economy 7 meters are being installed now but smart meters can have an Economy 7 tariff set to achieve the same outcome. Storage heaters are still sold.
Because of their length they were usually installed in corridors, so they warmed corridors rather than bedrooms or living rooms.
I am not sure why stopped being popular but maybe it was the rise of heat pumps which are ubiquitous in most of the country now.
I like your license :-D
Finland's gigantic commercial "sand battery" stores heat for months. Hopefully their techniques can be adapted for smaller use cases, https://www.bbc.com/news/science-environment-61996520
Oh look, the article even says this: "Today's storage heaters have such good insulation that the only heat coming into the room is from air being blown through the hot core by an ultra-quiet low-speed fan the length of the heater with the warm air coming out of the bottousually m of the heater at floor level - even when the core is full charged the outside of the heater is usually barely warm to the touch - and never hotter than a water-heated radiator"
I do not miss them one jot.
But needing to prophecy the weather of the morrow and being too hot or cold when not successful, no, that's on the technology.
[0] https://en.m.wikipedia.org/wiki/Trombe_wall
I wander if as we switch to "green" electric if we will see a reappearance of them. Controlled on timers and via the internet, electricity providers could schedule and stagger the times they are heated up to level the demand.
If there’s a neat thing about these old resistive heat storage bricks, it’s the use of a fan to deliver hot air immediately.
If the economics of generation v storage work out that it's cheaper to overgenerate most of the time, efficiency isn't going to matter, demand shifting to when energy is cheap is going to be the key. So then it's a question of heat pump is battery storage v storage heater.
If successful, phase 2 would to be to circulate that heat into the house.
Of course it's way less efficient than a solar water heater, but reduces a lot of the complexity/cost and potentially lets me dump excess solar.
Another thing to ponder is a sand ‘battery’ as a power / heat sink - lower heat capacity than water but doesn’t boil at 100C so can absorb more energy.
https://www.youtube.com/watch?v=kkoesuG72xQ
https://energyeducation.ca/encyclopedia/Thermal_mass
The issues and possibilities we are facing now are different: With heat pumps we can use electricity way more efficient than with resistive heating. When excess electricity is available doesn't follow a simple curve anymore but can be predicted only some time ahead.
If insulation products can enable safe, economical storage at very high temperatures, sand can be used for energy storage, https://news.ycombinator.com/item?id=33696105
I wish the original article touched upon the electricity rates. If you can rely on off peak rates being less than 1/4 of the on peak rates, then I can see this making sense. Otherwise it seems better to use electricity more efficiently, exactly when needed.
I've been scoping out this company for some time, my boiler is currently in good shape but would love to switch down the road.
They heat up water via HeatPumps to required temp during the day when outdoor temps are higher and electric is cheaper. Max water temp can change based off excepted nighttime temp.
I really regret the choice, and wish I had gone with Artic with their integrated system for HVAC and water. It just makes so much more sense.
There are definitely not enough installers trained on heatpumps, and many just treat them as drop-in replacements for gas fired equipment, because that's what they know. It is rare to find someone who looks at the whole picture and also deals with the heat loss mitigation.
As it is a tankless water heater may be the easiest way to “fix” yours - or spend a big amount for a knowledgeable energy contractor.
I remember the website of one enterprising New Zealander, where he was using an under house water storage tank as a heat sink accessible by his heat pump!
That's an astonishing difference in capacity.
But then it can explode and destroy a small town.
Remember, hot water moved mountains.
My own opinion of the sector has been tarnished by repeated bankruptcies and constant haranguing to get a sodding smart meter installed.
In defence of smart meters, they allow half-hourly settlement, which was required for smart charging of EVs. I don't understand exactly why this was required, but we couldn't work with retailers that didn't have this in place.
1. https://www.theguardian.com/money/2022/nov/23/uk-energy-cust...
Overall heat loss would be lower, it could be an easier upgrade for homes with radiators, and could also serve hot water, at a wider range of temps than a normal tank type water heater.
> The device has been installed in the Vatajankoski power plant which runs the district heating system for the area. Low-cost electricity warms the sand up to 500C by resistive heating.. generates hot air which is circulated in the sand by means of a heat exchanger. Sand is a very effective medium for storing heat.. device could keep sand at 500C for several months. So when energy prices are higher, the [sand] battery discharges the hot air which warms water for the district heating system which is then pumped around homes, offices and even the local swimming pool.
Cool a big tank of water/ice using solar, so you can keep chiller aircon running overnight without using more electricity.
I think I've seen commercial versions of this (icebear?), but nothing domestic. In fact even domestic-sized chillers (for central hydronic cooling) seem rare.