Storing heat in bricks

[AntronX]

I came across this Rondo Heat Battery storing heat in bricks at 1500C and it got me thinking. One regular brick weights 2.3Kg, has 1000J/Kg/K specific heat capacity (0.278Wh/Kg/K) and costs $0.50 in bulk. Heated to 1500C one brick stores 0.278*2.3*1500=959Wh of heat. $0.5/0.959=$0.52/kWh(t) storage capacity cost. Compare this to $100/kWh(e) storage cost for batteries. Bricks can be assembled into a cube with internal channels to run coiled up nichrome wire to run electric current for heating the brick. Multiple banks of heating wire coils can be step switched to present ideal MPP load to solar panels reducing cost of MPPT controllers since solar panels can directly connect to heating wire without DC-DC converter. With PV cost being so cheap this could be great way to store multiple days of sun energy for house heating during winter. 1 Ton of bricks (434 bricks = $217) would store up to 416 kWh of heat equivalent to 16 gal of propane. Rondo claims 1% heat loss per day. The cost of insulated enclosure and air-air or air-water heat exchangers is extra but should not be expensive to DIY.

 

[AntronX]

Or place bricks inside double wall with high temp insulation tuned to pass heat into the house at controlled rate. This removes heat exchangers and makes walls better noise insulated but once the battery is "charged" it cannot be turned off until stored heat dissipates away into the house.

 

[Partimewages]

I'm dumb on this one. How do you get the bricks that hot and what do you insulate the area with? Tell me like I'm a 5 year old!

 

[AntronX]

Make a cube of bricks with electric heat strips inside the "core". Heat dissipates from the center of the cube toward outer bricks. Mount the cube on a rack with feet placed on heat insulating material to prevent thermal bridging. Build insulated box around brick cube lined with layer of heat reflective material inside backed by thermal insulation material that can withstand temps that high. Blow air through this enclosure and through heat exchanger to remove heat for use.

 

[Partimewages]

What kind of voltage for the coils? What is a good insulator for 3000 degrees?

 

[AntronX]

1500W halogen light bulbs can be used inside the brick core to produce very high temps without degradation. They are pretty cheap and can operate "forever" at reduced power.

 

[AntronX]

What kind of voltage for the coils?

Whatever your PV panels output.

 

[42OhmsPA]

I'd use a fire brick.

https://www.tractorsupply.com/tsc/product/us-stove-single-firebrick

Rutland 4.5 in. x 9 in. x 1.25 in. Fire Brick (6 per Box) 604 - The Home Depot

RUTLAND Fire Bricks are perfect for intermediate duty for building new fireplaces or to replace old or broken bricks in existing fixtures (wood or coal stoves, furnaces, and fireplace inserts). They can

www.homedepot.com

 

[AntronX]

I'd use a fire brick.

Probably unnecessary. Getting to 1500C with DIY methods is not happening since steel will melt making it pretty complicated to make something like that yourself. Steel loses half it's strength at about 700C. Still not bad at 447Wh per brick.

 

[Crowz]

Isn't this just a fancy version of what the British use for space heaters now?

Storage Heaters - Best Storage Heaters 2023 - Buying Guide

Browse Electric Night Storage Heaters for Market Leading Brands Including Dimplex and Creda. Compatible With the Economy 7 Tariff. Free Next Day Delivery.

www.electricpoint.com

I plan on getting one to try it out as a solar power dump to heat my house some.

 

[AntronX]

Yep. These space heaters heat bricks up to 600C.

 

[Partimewages]

So you will use excess PV to heat the bricks to store BTUs to heat with later?

 

[Quattrohead]

Yeah in the UK we call those storage heaters and they run on the Economy 7 tariff, well at least they did when I was a kid 40 years ago LOL.
They had a manual damper on the top that you could adjust to regulate the heat output but they invariably were extremely hot in the morning and had no heat left by the end of the day so overall slightly useless.

 

[garetwo]

So AWESOME to have people who think like this!! Thank you

 

[SeaGal]

Yeah in the UK we call those storage heaters and they run on the Economy 7 tariff, well at least they did when I was a kid 40 years ago LOL.
They had a manual damper on the top that you could adjust to regulate the heat output but they invariably were extremely hot in the morning and had no heat left by the end of the day so overall slightly useless.

"slightly"?... that's the understatement of the year.

 

[ksmithaz1]

I have this new carburetor you can put on your car that will let it run on water instead of gas. No really! So while you are re-inventing in-floor radiant heat . . . IMNSHO this is a hair-brained idea.

Even when it works, this stuff always sounds great in theory, but rarely pans out. In practice we generally find out about the hundreds of implementation issues that were not considered in the original model that render the idea much less useful. Every time you move energy from one form/state to another there is loss. You have to look at the practicality of the state shifts. Sometimes ideas like this do make sense for a very narrow set of conditions, but generally it's very hard to predict how your use case is going to change. During the course of the thread, we see the design discussion get increasingly complex as we work around various limitations.

From a solar perspective just throw up a couple of extra panels, and put in a bit more inverter, and run a heat pump for heat. In-floor radiant heat has a proven track record, that would be drastically easier to implement than something esoteric with brick, the density of the material is better and with fluids you can more easily move the heated material where it needs to be. If you had to you could heat that with resistive heat as well.

I used to live on military bases with steam plants, that were used for all kinds of things including heat and running machinery. There is a darn good reason why most of this equipment has been retired. It sucks. Generating energy, then using some dense material to store it as extreme heat, then using the heat to generate steam is an idea that should be forgotten.

 

[RussNM]

There is no way this would be remotely possible. firebrick listed above is rated at 2000f max. Even high duty brick (k26) is rated to 2600f max. Kaowool is also rated for 2200f. 3000f? Only with very expensive zirconium silicate and nitrite bonded silicon carbide is this temp even remotely possible. And to keep this thermal mass contained? Contained in what? Maybe you could hire Superman to hold your bricks. This sounds like some unicorn thing along the lines of perpetual motion. NO. ...TOTAL FANTASY .

 

[ksmithaz1]

You bury it in a portable volcano... Don't you know anything?

 

[AntronX]

Regular bricks start to crack at 650°C = 400Wh of heat storage per brick = $1/kWh.

 

[chasingentropy]

Regular bricks start to crack at 650°C = 400Wh of heat storage per brick = $1/kWh.

How would you insulate your diy brick battery while also allowing input and output from the system?