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Heat Storage Hypocausts: Air Heating in the Middle Ages (2017)
- VBprogrammer 8y agoThese are a fore-bearer of the masonry heater. Very similar to what some off-grid types have built and called a rocket mass heater. Very interesting principle but unfortunately (or fortunately if you are so inclined) they will never compete with the ease of operation of a gas (or oil) central heating system.
- toss1 8y ago... as much as there are issues w/oil & gas heat, reverting with wood would for the current population would quite quickly deforest the planet, not to mention be more polluting (especially particulates). Design for efficiency, solar collection into a thermal mass, etc...
- black6 8y agoCoppicing and pollarding are sustainable methods of producing wood for rocket mass heaters, which operate best with kindling-sized sticks of wood. Rocket mass heaters are extremely efficient. The wood undergoes almost complete combustion and particulates are not a concern.
- KirinDave 8y agoIt's worth noting a good rocket heater will have similar properties to a wood gassification system, which people may recognize as powerful enough and light enough to run converted service vehicles in the tail end of WW2.
- pbhjpbhj 8y agoKindling is the very smallest pieces you start a fire with - are you really supposed to use mm sized pieces? Coppicing would not be useful for that, unless you're heavily processing the coppiced wood first?
- pjc50 8y agoWe use a lot of energy. Last time I ran the numbers I estimated that if the Drax wood-fired plant used UK wood rather than Canadian wood it would consume every tree in the country within a year. 750k tonnes/year: https://www.drax.com/sustainability/one-company-helped-transform-biomass-business/ https://www.drax.com/sustainability/one-company-helped-trans...
- greglindahl 8y agoDrax looks like it generates electric power, not heat.
- KirinDave 8y agoWell, what's an interesting question about these systems is, "In a modern context where we understand science much better and have much more sophisticated materials available, could we use these principles?" The real trick here is using available materials for heat storage, using air convection to circulate heat but not waste gas, and tightly limiting oxygen flow to make the most of minimal materials. It's definitely not bad, from an efficiency standpoint, to be compared to rocket heaters. They're still some of the most efficient systems we have.
- adrianN 8y agoWe could probably improve the dimensions quite a bit if we used something other than granite for heat storage. Something that changes phase, like in those pocket warmers, would probably be more effective.
- yetihehe 8y agoThere is fireclay [1], and I have fireplace with several bricks made from it. When fired in the evening for 2-3h, will keep warm until morning. [1] https://en.wikipedia.org/wiki/Fire_clay https://en.wikipedia.org/wiki/Fire_clay
- xenadu02 8y ago“High efficiency” water heaters and furnaces use similar principles to this (and the glazed tile oven mentioned). A winding network of passageways to get maximum contact with the flue glasses and thus extract as much heat as possible. By contrast a traditional straight chimney wastes a lot of heat by dumping it outside.
- Retric 8y agoThat can be a feature in the summer when you wanted to cook inside.
- Yetanfou 8y agoI cook on a wood-burning stove year round. Here in west-Sweden it can get quite warm in summer (with last summer being an extreme example with a maximum of 37°C and a period of around a month with daily temperatures between 25°C and 30°C, we did most of our cooking outside on an electric plate as open fire was prohibited due to the extreme drought). When firing the stove just for cooking I use quick-burning wood (spruce, fir, etc) and it doesn't really add that much heat to the kitchen, the thing is quite efficient. Come the colder months I light the stove a bit earlier, using heavier types of wood (birch, elm, oak, etc). I have yet to fell a living tree for either the stove or the heating stove (which, between the two of them, heat the whole house) as every year there is enough windfall to keep up with the demand (between 3 and 5 cubic meters of split wood per year). Felling, hauling, cutting and splitting wood is about 2 weeks of exercise per year, it is the fuel which keeps you warm twice - once while harvesting, the second time while burning it. Yes, this might be more work than just flicking a switch, touching a zone on an induction cooker (which I used before I moved to Sweden) or turning a knob but it is more reliable, more sustainable, more useful and more fun than the alternative (electricity).
- pagutierrezn 8y agoIn some rural areas of Spain where access to wood used to be limited hypocausts still exist, work great and are heavily used because they are very efficient. I've seen lots of them and their construction is practically the same described by Romans
- dsfyu404ed 8y ago>A furnace's dimensions would depend on the size of the room to be heated. In private homes, where only the bedroom was heated, it would be one to two metres long, a little more than a metre wide and 50 to 60 cm high. In public buildings and monasteries, where large halls and rooms had to be heated, the furnaces would be much larger. This is massive compared to the size of a wood stove. It's amazing what a thousand years of incremental refinement will do.
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- KirinDave 8y agoThese systems do predate mass production of steel, so no surprise there. It is interesting to contemplate what solar or geothermal variants of this system could do. Nearly every home has a crawlspace of those dimensions underneath the ground floor.
- dsfyu404ed 8y agoNitpick: I think you mean cast iron. Steel is kind of tricky to cast and we've only been casting it for ~100yr and even then not for large things in high volume. The largest high volume production (i.e. consumer item sold by the thousands) cast steel thing I know of is steering knuckles on the newest Ford trucks. In contrast we've been casting things of all sizes and shapes our of iron since the 1800s. Considering the mechanical requirements of a wood stove it doesn't make sense to cast it out of steel.
- KirinDave 8y agoYou know, I thought that specific parts being switched to steel was a reason for the uptake of popularity in a wood burning stove, but I see this is only a case in a very specific market of wood burning stoves. Thanks for the correction!
- dsfyu404ed 8y ago
- keeganjw 8y agoIf you want to learn about an ancient solution to the opposite problem, air conditioning, I recommend this: https://en.wikipedia.org/wiki/Windcatcher https://en.wikipedia.org/wiki/Windcatcher
- bliblah 8y agoThanks for posting this, the gallery section left me speechless. I hope tensions die down so I can go visit Iran one day; i'm always impressed by the historical architecture that is present in the Middle East.
- oh_sigh 8y agoYou can go there now as an American, and it may be even safer than going there as a non-American, because you will have a government minder spend every waking moment with you.
- MrTonyD 8y agoI don't have references - but I remember reading that the gently sloped roofs of desert buildings would channel breezes, and that would be combined with narrow passages between buildings to create a more shaded and cool environment. I also remember reading that when Rome extended its control to warmer regions the buildings they built always included a basement for use during the warmer months. I sometimes wonder if a lack of inspired building codes has undermined our entire society. In my mind I imagine buildings created to foster community and encourage good use of resources such as heating, cooling, and food production.
- failrate 8y agoFun fact: even modern Korean condominiums have a modern equivalent of an ondol.
- abrowne 8y agoI wish more housing in cold-winter North America (like here in Minneapolis) had something like that.
- pagutierrezn 8y agoMore info on existing and still in use hypocausts in Spain https://en.m.wikipedia.org/wiki/Gloria_(heating_system) https://en.m.wikipedia.org/wiki/Gloria_(heating_system)
- pseudolus 8y agoIf you're in the UK or visiting the UK the Roman Baths in Bath, UK offer an amazing experience to see saunas heated with hypocausts. https://www.romanbaths.co.uk/ https://www.romanbaths.co.uk/
- agumonkey 8y agoprimitive technology dude built himself a hut with some form of hypocaust (fire tunnel beneath clay tiles)
- billbrown 8y agoThe podcast 99% Invisible had an episode[1] earlier this year that featured some of these passive innovations like India's stepwells[2] [1] https://99percentinvisible.org/episode/thermal-delight/ https://99percentinvisible.org/episode/thermal-delight/ [2] https://en.wikipedia.org/wiki/Stepwell https://en.wikipedia.org/wiki/Stepwell