How the New York City steam system works | Hacker News Reader

How the New York City steam system works

untappedcities.com

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which serve as a cleaner source of energy than oil or coal to over 1,500 buildings.

What does this even mean? Cleaner than burning coal or oil inside a building? In NYC that steam is still generated by fossil fuels. Steam is not a source of energy at all; it's a transfer medium.

You can create steam using resistive heating. However, can you also create it using a heat pump?

Yes. There are heat pumps capable of producing steam up to 200C. They are meant for industrial applications, and I think they're a relatively new development so not much used yet.

The efficiency goes down significantly with those temperatures, given that most sources of waste heat are low-temperature (such as datacenter heating water, waste water, etc - places where it makes economically and ecologically sane to extract heat).

That's the problem even in district heating where temps are ~115C (like in Helsinki). Sadly, reducing the temperature is not an easy task, since many buildings have heating systems designed for higher temps.

Even lowering those temps to 80C would improve efficiency of the heat pumps a lot. But it's a big project to get it done and will most likely take a decade or more.

Some cities do use big heat pumps in district heating systems, so probably it could be used for steam too.

I think steam is somewhat antiquated, it has needlessly large temperature differential to the environment which leads to excess transfer losses compared to normal district heating using hot water.

> What does this even mean?

The passage means that it's cleaner to burn the fuel once in a very efficient power plant than to have hundreds of smaller furnaces burn the same total amount of oil or coal. More complete combustion means better and cleaner energy. It also means there's no risk of carbon monoxide poisoning in those buildings.

> Steam is not a source of energy at all; it's a transfer medium.

By this argument, the fossil fuels you mentioned aren't an energy source either, but just a (very inefficient) transfer medium from hydrogen fusion in our sun into chlorophyll, then about 20 more steps and several million years.

If you can extract useful work from it, it's an energy source. Everything else is just a question of degree.

> If you can extract useful work from it, it's an energy source. Everything else is just a question of degree

No, this is ridiculous. If humans have to put in more energy than you get out of it, it’s just a transfer mechanism. What you’re saying is no different than claiming your outlet is an energy source.

Geothermal steam vs steam generated by burning coal is qualitatively different in multiple critical ways. Trying to muddy that is nothing more than pro-fossil fuel propaganda.

> If humans have to put in more energy than you get out of it, it’s just a transfer mechanism.

Fusion of atomic nuclei can't yet be done by humans at better than unity. Is fusion not a power source just because we can't do it yet? If so, the sun has news for you.

I’m talking about usable energy by humans today. This is by far the most critical thing to our society and the climate crisis.

Steam generated by burning coal is in no way a clean energy source while steam generated by geo thermals is. It’s just boiled water either way. Take some time to consider why that difference is relevant.

> What you’re saying is no different than claiming your outlet is an energy source.

Correct. And when heating the house i can decide between the energy source of steam or energy source of electricity.

It seems like a productive consideration for this discussion is a systems barrier. If you think in macro energy systems, everything would appear to be transport. In micro energy stems everything is sources.

False dichotomy conveniently paves over the climate crisis.

So we could also apply everything you said to electric cars?

Yes, an electric car’s energy source is absolutely not it’s battery you’re looking at the global energy system. It’s wind, solar, nuclear, hydro, fossil fuels, or some other minority energy source.

The thing is, a large scale fuel burn plant can do a lot better exhaust filtering for the stuff that is not CO2. The exhaust treatment stacks of a power/heat plant are insanely complex... you have particulate scrubbers that filter out soot and other particulate matter, sulphur scrubbers, NOx catalytic converters, after-burn stages for carbon monoxide, activated charcoal filters for organic residues. Unfortunately the Wikipedia article is only available in German but it gives a pretty good rundown (https://de.m.wikipedia.org/wiki/Rauchgasreinigung).

Your average small-scale boiler has nothing of that.

the centralized plants combine heat and electricity production. instead of a cooling tower or a cooling river they heat a city. thus whichever primary energy medium they use, the are (much) more efficient.

Steam can actually be waste heat from electricity generation, so mostly free.

Thought this was interesting:

> A co-generation plant uses just one fuel source and produces both electricity and steam, making it a very efficient mode of energy production. “ConEd steam service has the lowest carbon emissions intensity per unit of energy delivered compared to all other options available to the buildings of Manhattan,”

Cogen is also known as "combined heat and power": https://www.energy.gov/eere/amo/combined-heat-and-power-basi...

A lot of our modern use of energy is inefficient-by-design: the system is designed to 'use as much energy as possible'. Why don't we have more cogeneration systems, where the waste heat is used instead of released?

Earlier today I looked for information about boilers that can run on anything: wood, coal, oil, etc. I guess this was inspired by talking to my neighbor, who was waiting for his wood delivery yesterday. I don't know if he's hooked up to natural gas, but his fireplace gives him the option to not be dependent on the gas system for keeping warm. I was also looking at a hybrid boiler/heat pump systems, where the heat pump can be supplemented. The same neighbor told me his former employer's ground-source heat pump system did not work very well at all, on account of the ground loop making ice cubes out of the groundwater (or something like that).

> A lot of our modern use of energy is inefficient-by-design: the system is designed to 'use as much energy as possible'.

Obviously not. Systems are generally designed for lowest total cost of ownership. If fuel is cheap and capital expensive, it can make sense to 'waste energy', counterintuitive as that may sound, if that enables lower capital costs.

Of course, what goes into the TCO is also a question of debate. Including externalities like pollution and climate change, and suddenly the optimal point might shift considerably.

> Why don't we have more cogeneration systems, where the waste heat is used instead of released?

Because cogeneration systems, or rather the district heating networks, are capital and maintenance intensive and make sense only in relatively densely built areas with significant heating demands. Where they make sense they are awesome, though.

Service story about NYC steam heating (2014), https://heatinghelp.com/blog/nyc-one-pipe-steam/

> The call came in on a day when a no-mercy wind whipped out of the northwest, as it often does during a New York City winter. No heat.

> Since the ancient but newly renovated apartment building was still under warranty, the folks down at New York City's Department of Housing Preservation and Development passed the call on to the installing heating contractor. He immediately sent a man out to get the burner started.

> There was a problem, though. The burner was no longer attached to the boiler. In fact, the burner wasn't even in the building. Now as you know, one of the first rules of troubleshooting states that If It Ain't There, You Can't Fix It, so the serviceman began scratching his head, wondering what to do next.

The author of that piece has a long lecture about NYC steam heating at https://www.youtube.com/watch?v=nkgM0qCy5o4 . Very interesting!

Thanks for the video pointer!

> Mr. Holohan was an established speaker and in high demand on the seminar circuit, having taught more than 200,000 people prior to his retirement in January 2016 ... He is well known throughout the heating industry for his entertaining, anecdotal style of speaking. Dan Holohan began his love affair with heating systems in 1970 by going to work for a New York-based manufacturers' representative that was deeply involved in the steam- and hot-water heating business. He studied hard, prowled many basements and attics with seasoned old-timers, and paid close attention to what they had to say. Mr. Holohan founded HeatingHelp.com in 1997. His daughter, Erin Holohan Haskell, now owns and operates this tremendous resource.

Mid-2007 I walked into Grand Central, clueless and exhausted after having worked over the entire previous night, I only half-registered that it wasn't very crowded. However I needed stuff at the Rite-Aid before going home. No one was at the register. Then no one was at the register at the other entrance to the Grand Central Rite-Aid store either.

I put everything down. Left the store and noticed that there were no other people in the station at all. Nope. I'm out. Second time in six and a half years that I just walked home.

I'm sure that somewhere there's surveillance video of me looking like Mr. Magoo wandering into evacuated region of the city after a steam tunnel had exploded.

https://en.wikipedia.org/wiki/2007_New_York_City_steam_explo...

The article mentions but does not list other steam systems around the country. There are apparently at least a dozen in the United States and many others around the world: https://en.wikipedia.org/wiki/District_heating#United_States

They're very popular at universities in the U.S. (although possibly on the way out). The linked Wikipedia article has a big list of universities

There’s a great book called The Works: Anatomy of a City that has fascinating diagrams and explanations for NYC infrastructure. I highly recommend it.

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?

> 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

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.

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).

But it's far less efficient to create the steam in the first place. And the lack of pumping is not free, the energy comes from the steam itself.

Sure for the end users point of view it might seem more efficient but as a net hot water is far far more efficient.

The trend in district heating systems is towards lower temperatures. Lower temperatures means that more of the waste heat in the power plant can be extracted, lower heat losses in the piping, and also if using heat pumps then lower temperatures can give a big efficiency boost. But yes, the downside is higher massflow, but this is certainly an optimization problem that engineers have calculated the optimal point for, given the available technology.

Steam heating is an ingenious invention, but it was also made in a world where pumps, the electricity to run them, PID controllers and whatnot, were expensive. That's why you tend to find it in the oldest district heating grids around.

No -- for one example, Copenhagen has just finished replacing the old steam-based district heating system with one based on hot water.

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.

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.

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…

The Boston Museum of Science has a 1906 Rollins steam engine in its basement [0]. It used to be powered from the Boston steam system, turning about once every five seconds (which was about a tenth of its rated speed). Unfortunately, at some point the steam supply switched to a lower pressure, and it was no longer enough to keep the engine turning.

[0]: https://commons.wikimedia.org/wiki/File:Museum_of_Science,_B...

I remember seeing it as a kid. It wasn't until I was a student many years later that I appreciated the design of the governor.

Hence the term "Running balls out."

So they claim this is the cleanest way to deliver energy, but that’s very unintuitive to me. It seems like there would be a huge transmission loss in piping hot steam through the whole of Manhattan, and I didn’t think steam engines were particularly efficient. So my intuition is failing here.

For those in the know, what makes a steam system like this effective as a clean energy distribution system, and how does it compare on a cost basis?

https://www.esmagazine.com/articles/83622-heating-with-steam...

It looks like it's efficiency has to do with the fact that it's an entirely passive heating system - it doesn't require any infrastructure except laid pipe to operate.

(I went on a Google quest after reading your comment and wondered the same thing. Thought I would share...)

Not to get off topic, but steam engines still drive the whole world; whether nuclear or gas or coal fuel, or concentrated solar power, steam turbines are how heat is turned into motion to make electricity. Modern ones operate very close to the theoretical limit of efficiency (around 40% [1]). The great advance James Watt made in the late 18th century, was a technique to recapture heat from the exhaust and raise practical efficiencies to several percent, with the remainder of the theoretical limit eeked out progressively over the following century.

One of the ways that limit is approached is to use the largest temperature difference the materials can stand; steam for large turbines is hot. The exhaust is still steam, but no longer hot enough to drive things efficiently. Indeed, the cooling loop of many plants run steam-hot, just not superheated-hot. Another common district heating approach (used in NYC) is a small direct gas-fired turbine driving an electric generator, with steam cooling. Combined generation is the use of that waste heat, for other heating purposes, and can raise total system efficiency.

Similarly, Iceland uses a lot of geothermal heating; some directly but much is waste heat from geothermal-electric plants. Since the geothermal taps are not that hot, an enormous volume of fluid is moved and the cold side needs to be quite cool; the output is barely-hot water after going through the cycle. But there's a lot of it. So much so, that they have under-sidewalk heating in Reykjavik and outdoor pools in winter. Most places just throw such heat away without making further use of it. It's traditionally been cheaper (or at least easier/simpler) to distribute and burn fossil fuels than to try and recapture and redistribute low intensity heat.

The pipes are indeed heat-leaky, despite usually being heavily insulated.

[1] https://en.m.wikipedia.org/wiki/Carnot%27s_theorem_(thermody...

> gas or coal fuel ... steam turbines are how heat is turned into motion to make electricity

While steam turbines can be found at natural gas plants, it's typically only for waste heat recovery in combined cycle plants. Primary generation is more commonly done with combustion turbines, which are more like jet engines. They don't use steam.

They're just referencing the earlier claim that the new natural gas boiler is cleaner than the old coal boiler. The sentence is worded incorrectly, and doesn't claim to be a cleaner distribution method either. They said they keep it because it's too difficult to sufficiently upgrade the buried electrical distribution system.

My understanding, as I mentioned in another comment, is that to some degree this steam is waste heat from generating electricity (where does the steam go after it turns the turbines?) so basically free.

Possible I’m misinformed.

Those orange and white steam pipes are something I've wondered about since I was a kid. I NEVER realized what a fascinating system they were hinting at.

This is my first time in New York, I thought those steam pipes were a hack to fix steam build up in the sewer system. I didn't realize it's a separate system. Actually the heat and hot water in the building where I'm staying is very likely steam based, just considering the age of the building and the location.

My college dorm was adjacent to the campus power plant and our rooms were quite toasty in the winter. The radiators in our dorm were older than my dad and still worked!

(I will not comment on whether we found a way into the steam tunnels and what we did when we may or may not have gotten there.)

>Then that goes into either a boiler and one of our more traditional plants, or goes into our Co-Gen system… We add fuel (our fuel is 97% natural gas). We only use fuel oil in the dead of winter if there’s a natural gas shortage or emergency

Halfway down the article I found the answer to my question—what energy heats the water for steam? Natural gas

"Steam Control" was a key phrase in the Tom Wolfe novel "Bonfire of the Vanities".

It was a reference to political influence peddling.

[1] https://www.cse.iitk.ac.in/users/amit/books/wolfe-2002-bonfi...

I remember first learning about their steam system when The Bone Collector with Denzel Washington came out.

> “Con Ed steam system has evolved from using coal to heavy fuel oil to natural gas. We’re really working to continue this effort of greening the system using renewable fuels or renewable technologies.”

Wish they went into more details about this, like how much is from wind and solar.

They don't need to go further into it as they state the answer right there in the article: We add fuel (our fuel is 97% natural gas). We only use fuel oil in the dead of winter if there’s a natural gas shortage or emergency, otherwise we are natural gas all the time

In other words they currently use gas and a bit of oil.

Looking forward to the steam coming from nuclear power plants

There are district heating systems using heat from nuclear power plants in several countries, mostly Eastern Europe: https://en.wikipedia.org/wiki/District_heating#Nuclear_fissi...

2021

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