> 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.

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

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.

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.

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.