The idea is based on that of the solar updraft tower [link], but instead of producing the heat with solar collectors, bring together the hot air from all of the chimneys of the homes and businesses of a town.

An insulated underground "waste heat sewer" would run underground, and connect to each home or buisness, and would take the place of the normal chimeny of that building. It would lead to a single really tall chimney / updraft tower for the entire town.

The inside of the air sewer would be at low pressure (like the bottom of a solar updraft tower), which would prevent the hot air (which would probably contain carbon monoxide and other pollutants, which would normally go up individual chimneys) from leaking out. As an added safety feature, check valves would prevent air from it from entering any building it's connected to it.

Thermostat controlled valves would prevent excessivly cool building air from entering the air sewer and slowing the whole thing down.
-- goldbb, Jan 22 2009

Solar Tower Video http://www.youtube....watch?v=0tWlP0knKQU
When are the Ozzy's going to finally build this thing? [Wily Peyote, Jan 23 2009]

Solar updraft tower http://en.wikipedia...Solar_updraft_tower
The encyclopedia definition [goldbb, Jan 25 2009]

I think you'll need fans (power input) to drive this 'sewer'.

It's called low grade heat for a reason.
-- Texticle, Jan 23 2009


Urban "Solar Tower" variant?

As a fan of the Solar Tower, my first thought was "how do we keep this thing lit?". Your idea's heat energy comes from the waste heat of chimneys which go UP for a reason. Giving the chimney a u-turn and driving the exhaust down into the sewers is like, potential energy wise, moving the rock from the mountain down into the valley. Why would the fires want to stay lit? The path of least resistance for smoke would be to by-pass the chimney-cum-sewer system altogether, and just fill the house. (Would an above the house venting system be more feasible?)

But, let's assume for the moment that the solar tower is started artificially with, say ... a giant spark plug, or something. Now we have negative pressure in the pipeline, chimney fires work, and with the one-way check valves that you mentioned: Utopia. All exhaust pollution is vented at one point (to be dealt with as seen fit).

But this begs the question: would just covering the whole city with glass (ala Buckminster Fuller), but with the solar tower addition, just be simpler? Many of the ideas mentioned in the Halfbakery could be utilized: heat from black asphalt roads would be a bonus, etc. Or maybe a combination of both chimney venting system and greenhouse glass cover?
-- Wily Peyote, Jan 23 2009


[+] I'm pretty sure this would work just fine siphonically, once it got going. It would provide one central location for pollution mitigation (scrubbers, electrostatic precipitators, or whatever), or, failing that, it could be used to route the pollutants further away from the population of the city.

// would just covering the whole city with glass (ala Buckminster Fuller), but with the solar tower addition, just be simpler? //

That would trap the pollutants in with the people, though whether that would be worse than current smog, or whether the updraft would outweigh the trapping, is not immediately obvious. I think it would necessarily also make the city warmer overall, regardless of the effectiveness of the updraft.
-- notexactly, Apr 23 2019


This is actually not such a stupid idea.

I don't know how much heat is lost through chimneys. I'm guessing a modern central heating boiler vents a few hundred watts when it's running. Coal or wood fires probably vent a lot more (unless they're new high-tech ones), but there are fewer of them. So, maybe a year- round average of 200W per household.

On the other hand, the cost of installing this for a neighbourhood would be huge, and there are probably more efficient ways to recover heat from chimney outputs.

And another thing: the airflow through any one house is going to depend on things like how leaky the house is (since the air has to get into it somehow), and on the total heat being vented by everyone else connected to the same system. I can envisage some poor sod freezing his arse off because everybody else's waste heat is sucking cold air through his house.

So, OK, maybe it wasn't actually not such a stupid idea.
-- MaxwellBuchanan, Apr 23 2019



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