What is a rocket mass heater?
Why Hacker News recommends it
Linked as the quickest way to grasp the rocket mass heater concept in threads on heating and thermal storage.
What it is
A two-minute explanation of what a rocket mass heater is, starting from how a conventional wood stove works and why creosote and chimney fires occur. It shows how burning hot and storing the heat in thermal mass makes for an efficient heater.
Recommended by 2 HN commenters across 2 different months, 2018 to 2022.
What Hacker News said
Recommends michaelbuckbee · 2018-10 · on “Heat Storage Hypocausts: Air Heating in the Middle Ages (2017)”
I wonder what the efficiency is compared to a modern "rocket stove" build [1] Mass rocket stoves are _incredibly_ efficient. So much so that I've always wondered why more similar designs weren't used in times when the primary heat sources were wood, etc. 1 - [this video] (skip to 1:50 if you want to see a full one and not the ms paint diagrams)
Recommends mikeytown2 · 2021-02 · on “What went wrong with the Texas power grid?”
Best fireplace in terms of efficiency is a rocket mass heater. It burns the wood gas in a secondary burn chamber and then routes the exhaust through a lot of thermal mass. One 2 hour fire a day will usually heat 2000 sq feet of house. 3m video explains the concept; longer videos will better explain it [this video]
Recommends mikeytown2 · 2021-02 · on “What went wrong with the Texas power grid?”
You can do a hybrid approach with the hot metal burn chamber for wood gas and earthen materials to slowly radiate the heat. This is called a rocket mass heater. The exhaust temperature is usually below 100C and often smokeless (a complete burn). Using a fan to extract heat from the final vertical stack (pipe around the exhaust with air running by) can give you an exhaust temperature of around 40C. Here's a quick 3 minute video that explains the concept; there's other YouTube videos that go into greater details if you wish to research this topic more. [this video]
Cites tomohawk · 2021-12 · on “Oven Stoves and Heat Walls (2008)”
The rocket mass heater is the modern replacement for this. [this video] Uses about 1/10th the fuel, and fuel can be wood unusable in other stoves. Very little exhaust / smoke. Super efficient.
Cites mikeytown2 · 2022-08 · on “Home Heating Cost Comparison”
Quick Video about the rocket mass heater. I'm guessing the cost to heat with wood, would be even lower if your house was built around this. [this video]
Cites zdragnar · 2022-11 · on “A sand battery could transform clean energy”
A few things: Clay weighs significantly more than sand. For the same volume of material, clay will store significantly more thermal energy. The big question is- is the hot air on a closed loop or an open loop? I don't know of too many fans comfortable cycling 600C air, which means that you need an open loop of air (fresh air > fan > heater > sand > exhaust). If the sand isn't drawing heat off of the hot air fast enough, the heat won't actually "sink" in through the sand. If we are talking a closed loop of air (fan > heater > sand > fan) then the sand will get fully heated. My reference to "residential" is the aformentioned rocket stove mass heater- see [LINK] or [this video] and [LINK] if you pre