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Steam Networks

worksinprogress.co

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Re: Steam Networks

#61

Post by walrus01 »

graemep wrote: post #38
walrus01 wrote: post #35

Earlier quoted context omitted.

In terms of thermodynamics, a electric resistive heater is 100% efficient, but if the measurement is how many BTU of heating you can put into a room in a day with a certain amount of watt hours, a modern heat pump will always beat it. Also of course 100% electric.

A heat pump is more than 100% efficient on that measure. I am not sure about "always". Does it not depend on the temperature difference? The use cases for steam seem to be where you need more than room heating though: the first paragraph mentions sterilising medical equipment, humidity control, and washing.

My understanding is that it varies by temperature difference, but there's specialized series of heat pumps which work "okay" with very cold outside temperatures, even down to -25C, which are becoming popular to replace oil tank heating systems in Atlantic Canada. Apparently even when operating at -20C outside air they're still more efficient than electric baseboard heating.

I don't know of any of the customers of the steam system in downtown Vancouver that use it for sterilization purposes, it connects almost exclusively large office towers. There's no hospital or medical facilities connected to it.

Re: Steam Networks

#62

Post by Brian_K_White »

nebolo wrote: post #50
virtue3 wrote: post #49

Earlier quoted context omitted.

And their efficiency plummets starting at 40F and below.

The efficiency of modern cold-climate heat pumps plummets to 200-300% at 40F and perhaps 175% at 5F.

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.

Re: Steam Networks

#63

Post by subpixel »

coryk135 wrote: post #25

This part really caught my attention: > in 1962, the anthracite seam under Centralia, PA – 25 miles to the west of Lehigh County – caught on fire and is still burning today.) That’s crazy to think that for over 60 years there’s been an underground coal mine on fire. I wonder how long the mines will burn for. The pictures on Google are quite interesting.

I've been there. It's where my ancestors are from, and an area of PA where all the jobs and civic like burned up long ago as well. Not a fun region.

Re: Steam Networks

#64

Post by mindslight »

lxgr wrote: post #20
darknavi wrote: post #17

Earlier quoted context omitted.

Pretty sure the steam is ran through radiators and not just dumped directly into the air.

Part of it is definitely dumped directly into the air through an over-pressure valve on each radiator. At least that's been the case in all steam-heated NYC apartments I've ever visited or lived in. But what counteracts this is a loss in humidity caused by the heating of cold air from the radiator itself (cold air warmed up reduces relative humidity), and in my experience, this more than counteracts the little bit of…

nit: The valve is a thermostat that vents the air/steam in the radiator when it's not hot enough, letting new steam come in and replace it. This gets heat to the radiator quicker (over pure diffusion), and provides a mechanism of controlling its individual heat output. Of course, these valves are often broken.

Re: Steam Networks

#65

Post by brnt »

virtue3 wrote: post #49
perihelions wrote: post #42

Earlier quoted context omitted.

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

And their efficiency plummets starting at 40F and below.

1990s called, they want their efficiency back ;)

Sure, you can still find good weather heat pump that crap their pants near or under freezing. However, the majority sold here in Europe still stay well of 200% down to -15C, some even -25C.

Re: Steam Networks

#66

Post by whatevaa »

nebolo wrote: post #50
virtue3 wrote: post #49

Earlier quoted context omitted.

And their efficiency plummets starting at 40F and below.

The efficiency of modern cold-climate heat pumps plummets to 200-300% at 40F and perhaps 175% at 5F.

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.

Re: Steam Networks

#67

Post by paxys »

someuser2345 wrote: post #33
imglorp wrote: post #30

The article cites end-to-end efficiency as 60%. Plus the costs of maintaining steam generators and the pipe network. Electrical transmission systems are roughly 85% efficient to the consumer; together with boring old resistive electric radiators which are 100% efficient. So is there any reason to subscribe to the steam system for new construction?

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.

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.

Re: Steam Networks

#68

Post by Brian_K_White »

lxgr wrote: post #29

My favorite fact about steam distribution systems is that they can be used for cooling, using either a steam-powered compressor or using adsorption refrigeration. At least the former seems to actually have been employed or at least studied as an option by ConEd in NYC: https://web.archive.org/web/20071008014254/http://www.coned....

Similarly propane powered refridgerators.

Re: Steam Networks

#69

Post by [deleted] »

harrison_clarke wrote: post #22
metadat wrote: post #15

How is mildew and mold avoided in the pipeline and interior spaces being heated by steam?

if steam leaks out and gets trapped somewhere, presumably that's a breeding ground for mildew and mold inside the pipe, can much life survive? is there anything to eat in there? has anything evolved specifically to live in NYC steam pipes?

[deleted]

Re: Steam Networks

#70

Post by taurath »

jasonthorsness wrote: post #5

Even Seattle has one of these! And the University of Washington as well. It’s amazing that the economics holds up even today. https://en.m.wikipedia.org/wiki/Seattle_Steam_Company

You can see the steam plant from pike place market and the steam stacks look like there’s some sort of industrial thing going on which now looks very out of place. It was interesting to figure out what the building was for! The biggest customers are the hospitals up on the hill, and the steam is used to sterilize instruments alongside heating.
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