4 ms·

Most electricity is generated by using steam to turn turbines, right? So it definitely seems more efficient to just use the steam directly, instead of convertin

Most electricity is generated by using steam to turn turbines, right? So it definitely seems more efficient to just use the steam directly, instead of converting it to electrical energy and then converting it back to heat.

proee 2y ago
Except you can ONLY use steam for heating and transporting it over distance is not efficient. If you turn steam into electricity you can use it for ANYTHING and transport it over long distances efficiently.
- dietr1ch 2y ago
  It also means that at the local scale it might be better to distribute steam. Think about future residential nuclear plants. It might not be worth investing into steam distribution on top of electrical as electrical is more flexible, but there might be steam that's residue otherwise that could be used on heating.
  - abeppu 2y ago
    > future residential nuclear plants What does this mean? Are you imagining a future where individual houses have their own nuclear plants? Or where nuclear plant workers live on-site? I'm get the argument that we should have more nuclear power, and that some future reactors may be small, but I don't understand the expectation that they would be close enough to residences to pipe steam.
    - wafflemaker 2y ago
      In many places in the world people don't live on ranches or in 1000 m² houses, but in 80-150 m² twin houses or even flats. In such tighter conditions, you can easily have enough inhabitants per km² that it would justify building small mobile nuclear reactors. Who would like to live next to a reactor if it can melt down? Well, you have reactors using fuel pellets locked in marbles that due to their diameter can never meltdown.
    - dietr1ch 2y ago
      There has been a couple small scale nuclear power projects for a while now, - https://newatlas.com/energy/oklo-aurora-nuclear-microreactor-idaho/ https://newatlas.com/energy/oklo-aurora-nuclear-microreactor... - https://www.popularmechanics.com/science/a33896110/tiny-nuclear-reactor-government-approval/ https://www.popularmechanics.com/science/a33896110/tiny-nucl... - https://www.nuscalepower.com/products/nuscale-power-module https://www.nuscalepower.com/products/nuscale-power-module They target from home to residential scale. I hope they are eventually a thing.
- vdnkh 2y ago
  Steam in NYC is also used for cooling https://en.wikipedia.org/wiki/New_York_City_steam_system https://en.wikipedia.org/wiki/New_York_City_steam_system
perihelions 2y ago
That reasoning isn't enough on its own, because on the clients' end, electric heat pumps can be more efficient than direct steam heating. Actually their "efficiency" is far above 100%, https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance
- virtue3 2y ago
  And their efficiency plummets starting at 40F and below.
  - nebolo 2y ago
    The efficiency of modern cold-climate heat pumps plummets to 200-300% at 40F and perhaps 175% at 5F.
    - Brian_K_White 2y ago
      But 5f is still high. This is actually terrible and supports their point. Heat pumps are not sized as if they were running at a mere 100% or less, they are sized for the btus they normally produce, and aim to run close to 100% of the time, meaning they will be too small and not be able to do the job when they drop below 200-300% efficiency, unless they are grossly oversized. That leads to short cycles which makes condensation and moisture in the summer and wear and tear all year and less electrical efficiency because starting a pump and blower costs more than running it. Current inverter types that can run slow do allow them to be oversized but it's still not great. Those are more expensive and have more failure points in electronics too.
    - whatevaa 2y ago
      So at -20 and below they are basically very, very expensive resistive heaters. Good for medium climates, bad further north. Also either need very expensive oversizing or backup heat sources to compensate reduced heat output, even if you get occasional cold spikes. Unfortunately nothing in life is as simple as it first seems.
a1371 2y ago
That's not true. Except for nuclear and solar collectors, all renewables, especially hydro, have nothing to do with steam.
- outworlder 2y ago
  What isn't true? > Most electricity is generated by using steam to turn turbines That is true. It is also true that renewables usually do not use steam. But they don't answer for "most electricity". That's natural gas, coal and other types of thermal plants, including nuclear.
  - bluGill 2y ago
    Renewable power is 30% of the world grid. Gas combined cycle power plants get part of their power from gas in the turbine directly, and part of it from steam cycles. I can't figure out what % over of power comes from which part, and not all gas power plants are combined cycled. It seems reasonable to say that most electricity is not generated by steam turbines. However I'm not sure how to find the real data to verify this. (and pedantically the gas in a gas turbine is mostly steam)
- kibwen 2y ago
  Geothermal plants also use steam (not to be confused with geothermal heating/cooling, which is just a heat pump with the heat exchanger underground rather than in the air).
bluGill 2y ago
Where I live most electricity is generated from wind. Solar also has a large share of some grids. Your location may be different but it should have a significant renewable share by now.
paxys 2y ago
There's no single efficienty number for "steam". Steam turbines in large power plants for example are >90% efficient when considering just the thermodynamics. There are a hundred other variables involved.
- m4rtink 2y ago
  I'll note that powerplant steam turbines are often pretty cutting edge & supported by essentially a special plant to achieve this levels of efficiency and reliability. Stuff like hydrogen cooling the generator bit: https://en.wikipedia.org/wiki/Hydrogen-cooled_turbo_generator https://en.wikipedia.org/wiki/Hydrogen-cooled_turbo_generato...
mikepurvis 2y ago
I believe in the NYC case, the steam is also not right off the reactor— it's waste steam that has already been through a turbine and so is still hot and under some amount of pressure, but is no longer economically valuable in a power plant context. So it's run into the city as an alternative to just venting it into the atmosphere.
lincon127 2y ago
The inefficiencies come from infrastructure. Transferring electricity is so goddamn cheap, that city planners and developers hardly consider it a footnote. Water, sewage and drainage on the other hand are much, much more expensive. They require much more space, and oft times need to be pressurized. Imagine that with steam pipes where the steam on top of all that, needs to be heated too. Sure, hooking up to an existing steam main probably doesn't cost too much, but building new mains can't be worth it, even in the long run, as infrastructure constantly needs to be upgraded.

proee 2y ago

Except you can ONLY use steam for heating and transporting it over distance is not efficient. If you turn steam into electricity you can use it for ANYTHING and transport it over long distances efficiently.

dietr1ch 2y ago
It also means that at the local scale it might be better to distribute steam. Think about future residential nuclear plants. It might not be worth investing into steam distribution on top of electrical as electrical is more flexible, but there might be steam that's residue otherwise that could be used on heating.
- abeppu 2y ago
  > future residential nuclear plants What does this mean? Are you imagining a future where individual houses have their own nuclear plants? Or where nuclear plant workers live on-site? I'm get the argument that we should have more nuclear power, and that some future reactors may be small, but I don't understand the expectation that they would be close enough to residences to pipe steam.
  - wafflemaker 2y ago
    In many places in the world people don't live on ranches or in 1000 m² houses, but in 80-150 m² twin houses or even flats. In such tighter conditions, you can easily have enough inhabitants per km² that it would justify building small mobile nuclear reactors. Who would like to live next to a reactor if it can melt down? Well, you have reactors using fuel pellets locked in marbles that due to their diameter can never meltdown.
  - dietr1ch 2y ago
    There has been a couple small scale nuclear power projects for a while now, - https://newatlas.com/energy/oklo-aurora-nuclear-microreactor-idaho/ https://newatlas.com/energy/oklo-aurora-nuclear-microreactor... - https://www.popularmechanics.com/science/a33896110/tiny-nuclear-reactor-government-approval/ https://www.popularmechanics.com/science/a33896110/tiny-nucl... - https://www.nuscalepower.com/products/nuscale-power-module https://www.nuscalepower.com/products/nuscale-power-module They target from home to residential scale. I hope they are eventually a thing.
vdnkh 2y ago
Steam in NYC is also used for cooling https://en.wikipedia.org/wiki/New_York_City_steam_system https://en.wikipedia.org/wiki/New_York_City_steam_system

perihelions 2y ago

That reasoning isn't enough on its own, because on the clients' end, electric heat pumps can be more efficient than direct steam heating. Actually their "efficiency" is far above 100%, https://en.wikipedia.org/wiki/Coefficient_of_performance https://en.wikipedia.org/wiki/Coefficient_of_performance

virtue3 2y ago
And their efficiency plummets starting at 40F and below.
- nebolo 2y ago
  The efficiency of modern cold-climate heat pumps plummets to 200-300% at 40F and perhaps 175% at 5F.
  - Brian_K_White 2y ago
    But 5f is still high. This is actually terrible and supports their point. Heat pumps are not sized as if they were running at a mere 100% or less, they are sized for the btus they normally produce, and aim to run close to 100% of the time, meaning they will be too small and not be able to do the job when they drop below 200-300% efficiency, unless they are grossly oversized. That leads to short cycles which makes condensation and moisture in the summer and wear and tear all year and less electrical efficiency because starting a pump and blower costs more than running it. Current inverter types that can run slow do allow them to be oversized but it's still not great. Those are more expensive and have more failure points in electronics too.
  - whatevaa 2y ago
    So at -20 and below they are basically very, very expensive resistive heaters. Good for medium climates, bad further north. Also either need very expensive oversizing or backup heat sources to compensate reduced heat output, even if you get occasional cold spikes. Unfortunately nothing in life is as simple as it first seems.

a1371 2y ago

That's not true. Except for nuclear and solar collectors, all renewables, especially hydro, have nothing to do with steam.

outworlder 2y ago
What isn't true? > Most electricity is generated by using steam to turn turbines That is true. It is also true that renewables usually do not use steam. But they don't answer for "most electricity". That's natural gas, coal and other types of thermal plants, including nuclear.
- bluGill 2y ago
  Renewable power is 30% of the world grid. Gas combined cycle power plants get part of their power from gas in the turbine directly, and part of it from steam cycles. I can't figure out what % over of power comes from which part, and not all gas power plants are combined cycled. It seems reasonable to say that most electricity is not generated by steam turbines. However I'm not sure how to find the real data to verify this. (and pedantically the gas in a gas turbine is mostly steam)
kibwen 2y ago
Geothermal plants also use steam (not to be confused with geothermal heating/cooling, which is just a heat pump with the heat exchanger underground rather than in the air).

bluGill 2y ago

Where I live most electricity is generated from wind. Solar also has a large share of some grids. Your location may be different but it should have a significant renewable share by now.

paxys 2y ago

There's no single efficienty number for "steam". Steam turbines in large power plants for example are >90% efficient when considering just the thermodynamics. There are a hundred other variables involved.

m4rtink 2y ago
I'll note that powerplant steam turbines are often pretty cutting edge & supported by essentially a special plant to achieve this levels of efficiency and reliability. Stuff like hydrogen cooling the generator bit: https://en.wikipedia.org/wiki/Hydrogen-cooled_turbo_generator https://en.wikipedia.org/wiki/Hydrogen-cooled_turbo_generato...

mikepurvis 2y ago

I believe in the NYC case, the steam is also not right off the reactor— it's waste steam that has already been through a turbine and so is still hot and under some amount of pressure, but is no longer economically valuable in a power plant context. So it's run into the city as an alternative to just venting it into the atmosphere.

lincon127 2y ago

The inefficiencies come from infrastructure. Transferring electricity is so goddamn cheap, that city planners and developers hardly consider it a footnote. Water, sewage and drainage on the other hand are much, much more expensive. They require much more space, and oft times need to be pressurized. Imagine that with steam pipes where the steam on top of all that, needs to be heated too. Sure, hooking up to an existing steam main probably doesn't cost too much, but building new mains can't be worth it, even in the long run, as infrastructure constantly needs to be upgraded.