The discussion revolves around the comparison between district heating systems and electricity generation from incineration plants. Participants explore the efficiency, economic viability, and practical implications of both approaches, considering factors such as temperature requirements, heat loss in distribution, and local energy demands.
Participants do not reach a consensus; multiple competing views remain regarding the efficiency and practicality of district heating versus electricity generation. There is ongoing debate about the implications of heat loss, economic factors, and the specifics of different systems.
Limitations include varying definitions of district heating systems, the dependence on local conditions for efficiency assessments, and unresolved questions about empirical data versus theoretical models.
According to this article, Norway is already exporting 10% of its generated electricity. Perhaps those in charge didn't see a need for more? Perhaps the cost of a steam turbine was too much? Perhaps there's no guarantee that garbage is going to be so plentiful in the future, and a turbine would have been a waste of money?TSN79 said:... Are there facets with the electricity-idea that makes district heating the absolute way to go?
Yes: district heating is much more efficient then electricity generation (around double).TSN79 said:My city has large district heating system, where the heat is generated at an incineration plant. I'm personally not a fan of district heating, and I would rather see the plant generate electricity through steam instead. I don't know if that was ever considered when the plant was built. Are there facets with the electricity-idea that makes district heating the absolute way to go?
I was under the impression that garbage burning plants operated at really high temperatures, as there's lots of potentially nasty stuff in there, and only high temps will break it down. I'm pretty sure these plants aren't just some guys throwing garbage into 55 gallon drums.Keith_McClary said:Efficient steam electric generation requires a high temperature. If they are just burning trash it may not get hot enough.
Since the efficiency of the plant is fundamentally limited by the ratio of the absolute temperatures of the steam at turbine input and output, efficiency improvements require use of higher temperature, and therefore higher pressure, steam.
Measured how? Do you have a source?russ_watters said:Yes: district heating is much more efficient then electricity generation (around double).
Thermodynamic efficiency, and this is pretty fundamental. Think of it this way: if you are making steam either way, you can either use it as-is for heat at near 100% efficiency (if you return the condensate) or you can run it through a thermodynamic cycle at 30-50% efficiency to make electricity. Heck, you can burn the gas in a gas turbine to make electricity and still get more heat than electricity from it. Here's an example, offering 65KW of electricity and 150kW of heat (model c65):pbuk said:Measured how? Do you have a source?
Yes, I would expect that heat loss is a lot higher than electricity loss in distribution, but I don't know how much. But I doubt it is half of the heat.pbuk said:Ah, so you are measuring at the point of generation. Unfortunately much of this gain can be lost in distribution in a district heating system and also in excess supply.
In the Arctic, but not so much in Florida.pbuk said:Agree that co-generation is the right way to go though in most situations.
In this report the average was exactly half, with the maximum in 2 cases out of 11 being 66%. Even taking an optimistic 25% gives a net 2.0 x 0.75 = 1.5 = 50% gain over electricity rather than the 100% you quote. And that's before taking surplus supply factors into account (what are you going to do with all that heat in the summer?), as well as excess demand issues (how do you meet demand in a cold snap, burn fossil fuels?)russ_watters said:Yes, I would expect that heat loss is a lot higher than electricity loss in distribution, but I don't know how much. But I doubt it is half of the heat.
That paper is hard to read (there isn't much detail on the systems), but it appears to be talking about hot water as a distribution medium, not steam. It isn't all that surprising to me that the loss is that high for a hot water distribution system, where the quality of the heat is much lower than steam. I would hope steam distribution is much better.pbuk said:In this report the average was exactly half...
Just turn it off. You end up with the default for the power plant, which is just dumping the heat into the atmosphere. Unless you can use the steam to run absorption chillers.And that's before taking surplus supply factors into account (what are you going to do with all that heat in the summer?)
It would depend on the type of system. If it's primarily a cogen system, yes, you could supplement it with natural gas fired boilers on top of the natural gas fired generators. The overall generation efficiency would drop a little, but not much. And the distribution loss will go down as load goes up....as well as excess demand issues (how do you meet demand in a cold snap, burn fossil fuels?)
Depending on the local weather (all year) and electricity prices heat supply alone might be economically better than cogeneration or electricity generation.TSN79 said:Are there facets with the electricity-idea that makes district heating the absolute way to go?
I have seen you post on a number of topics Russ, and generally have a great deal of respect for what you say and the way you say it. So why the hand-wavy stuff here?russ_watters said:... I would hope steam distribution is much better.
... The overall generation efficiency would drop a little, but not much.
We don't need the adversarial attitude please.pbuk said:So why the hand-wavy stuff here?
That is also hand wavy, and cites no source, nor is it specific enough to fact check.pbuk said:In the UK at least, district heating has a very bad reputation
You are right, on both counts. @russ_watters please accept my apologies.anorlunda said:We don't need the adversarial attitude please.
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That is also hand wavy, and cites no source, nor is it specific enough to fact check.