[gligorot]

Honestly first time I’m hearing that a city is heated like this…I mean it’s logical, but over here they heat water and then pump it out, which for some reason always felt very wasteful. This _feels_ better.

But what do they do to the steam once it gets to the top of a building? Is it just released into the atmosphere or the water is somehow cycled back down?

[greenyoda]

> But what do they do to the steam once it gets to the top of a building?

There are return lines that bring the hot water back to the plant. But the steam from the central system never gets to the top of a building. The heat from that steam gets transferred to the building's own closed system through a heat exchanger. The process is described here: https://en.wikipedia.org/wiki/District_heating#Heat_distribu...

A diagram can be found here: https://en.wikipedia.org/wiki/File:District_heating.gif

[reaperducer]

Honestly first time I’m hearing that a city is heated like this

Lots of American cities have district steam, and sometimes district cooling, too. Usually is limited to dense downtown areas.

Chicago and Houston come to mind. I think Seattle has steam.

[ars]

Hot water is more efficient - heating something to 500F just to then use it to heat air to 70, or a shower to 130 is thermostatically not favorable (the bigger the difference in temperature the less energy is transferred). It's better to heat water to 180 and pump that - the initial transfer of heat from the flame is much more efficient.

Releasing the steam would be a huge waste - but of energy, not of water. The water is quite minimal.

[userbinator]

Steam is more efficient specifically because it is very hot; you don't need as much of it to transfer the same amount of energy as water, nor does steam need pumped (which also takes energy).

[bombcar]

You can build a one-pipe system where the steam goes up and water goes down the same exact pipe. Takes some skill but it works and it is bog simple.

[doctor_eval]

apparently, FTA,

> Steam rises naturally, so it enabled buildings to get heated without using additional energy to get the heat to rise up.

But I’m not so sure about that…