Home thermal energy storage
Discussion
I thought I'd start a thread detailing my journey into building a thermal battery - basically a f**k off big tank of water that will be heated cheaply overnight and utilised during the day.
We live in a 6000sqft barn conversion that's 'OK' insulated but lots of glass and vaulted ceiling as well as other compromises means it's not the most thermally efficient.
The goal is true net zero (cost). We have 30kw solar array, 30kwh battery storage, 2 ground source heat pumps and a 25kw Mitsubishi multi City heating / air conditioning with fresh air heat recovery (that I installed about 6 years ago - retrospectively adding hidden AC took 6+ months and ripping the house to pieces!).
Everything is controlled via Raspberry Pi.
We live in a 6000sqft barn conversion that's 'OK' insulated but lots of glass and vaulted ceiling as well as other compromises means it's not the most thermally efficient.
The goal is true net zero (cost). We have 30kw solar array, 30kwh battery storage, 2 ground source heat pumps and a 25kw Mitsubishi multi City heating / air conditioning with fresh air heat recovery (that I installed about 6 years ago - retrospectively adding hidden AC took 6+ months and ripping the house to pieces!).
Everything is controlled via Raspberry Pi.
The theory is that you heat something up when electricity is cheap and use the heat when it s expensive. As I m with octopus it s 7p overnight per kWh.
We live in a fairly big barn conversation which already has a couple of ground source heat pumps that overheat the floor at night (charge it up) and this gradually releases heat during the day. In the deepest depths of winter they often need to run again.
I stumbled across a very large air to water Mitsubishi CAHV 45kw 3phase Air source heat pump on arsebook. £38k new, this one s ten years old and I picked it up for £500, did some fiddling about and repaired the cooling fans that were shattered causing it to be very out of balance.
Tested with a wheelie bin full of water that ie heated to 55 degrees in about 2 mins!
We live in a fairly big barn conversation which already has a couple of ground source heat pumps that overheat the floor at night (charge it up) and this gradually releases heat during the day. In the deepest depths of winter they often need to run again.
I stumbled across a very large air to water Mitsubishi CAHV 45kw 3phase Air source heat pump on arsebook. £38k new, this one s ten years old and I picked it up for £500, did some fiddling about and repaired the cooling fans that were shattered causing it to be very out of balance.
Tested with a wheelie bin full of water that ie heated to 55 degrees in about 2 mins!
On the one hand, cool. On the other hand, slightly disappointed when the title reads "thermal energy storage" and the content reads "water". Look into sand batteries.
"Sand batteries heat up to very high temperatures, typically reaching around 500°C to 600°C (932°F to 1112°F), storing energy from renewables like wind and solar in the sand or crushed soapstone, and then releasing it as hot air, water, or steam for district heating or industrial processes. The exact heat depends on demand, but these systems are designed to store thermal energy efficiently for long periods, with output temperatures ranging from 60°C to 400°C."
"Sand batteries heat up to very high temperatures, typically reaching around 500°C to 600°C (932°F to 1112°F), storing energy from renewables like wind and solar in the sand or crushed soapstone, and then releasing it as hot air, water, or steam for district heating or industrial processes. The exact heat depends on demand, but these systems are designed to store thermal energy efficiently for long periods, with output temperatures ranging from 60°C to 400°C."
Hoofy said:
On the one hand, cool. On the other hand, slightly disappointed when the title reads "thermal energy storage" and the content reads "water". Look into sand batteries.
"Sand batteries heat up to very high temperatures, typically reaching around 500°C to 600°C (932°F to 1112°F), storing energy from renewables like wind and solar in the sand or crushed soapstone, and then releasing it as hot air, water, or steam for district heating or industrial processes. The exact heat depends on demand, but these systems are designed to store thermal energy efficiently for long periods, with output temperatures ranging from 60°C to 400°C."
You're not going to get the multiplier effect of a heat pump with that sort of set up. A water tank is exactly the right solution for a house being heated by cheap electricity. It's cheap and scales up. The bigger the better for thermal efficiency. It's also far better than using a battery to try to store the electricity. One colossal winning feature of a thermal store is that you can shove heat into it from as many sources as you can be bothered to plumb in ... heat pump, biomass burner, direct solar, your old gas or oil boiler for backup. And the other is that they can dump a huge amount of power into your house when you want it."Sand batteries heat up to very high temperatures, typically reaching around 500°C to 600°C (932°F to 1112°F), storing energy from renewables like wind and solar in the sand or crushed soapstone, and then releasing it as hot air, water, or steam for district heating or industrial processes. The exact heat depends on demand, but these systems are designed to store thermal energy efficiently for long periods, with output temperatures ranging from 60°C to 400°C."
When we moved here we discovered that th house was originally plumbed for an oil boiler but last minute changed to a Ground Source heat pump but it’s only 11kw so as soon as temp went below 10 degrees the 9kw immersion came on!
When electricity was 15p/kw our annual bill was apx £6-7k a year. Plus £10k vehicle fuel.
Being a barn conversation it got very hot in summer and cold in winter.
Our 13kw log burner gave an indication as to what was needed!
When electricity was 15p/kw our annual bill was apx £6-7k a year. Plus £10k vehicle fuel.
Being a barn conversation it got very hot in summer and cold in winter.
Our 13kw log burner gave an indication as to what was needed!
Water is nice and cheap, easy to store, easy to heat evenly, easy to extract heat from or just use directly, and has great heat capacity.
What you're limited on is how hot you can make it, but that also helps with the storage as no exotic containers and simple to insulate.
If your demand is all going to be thermal and to drive output at normalish 55/60 type degrees for heating etc then it's a fine simple solution.
If you've got the space and the free power why not?
What you're limited on is how hot you can make it, but that also helps with the storage as no exotic containers and simple to insulate.
If your demand is all going to be thermal and to drive output at normalish 55/60 type degrees for heating etc then it's a fine simple solution.
If you've got the space and the free power why not?
cptsideways said:
A big tub of candle/paraffin wax I think is even more storage capacity.
Only half the specific heat capacity vs water, vastly more expensive, and who wants thousands of litres of hot paraffin nearby?Water is great stuff for storing energy if you can accept the temperature range.
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff