District heat is such a foreign concept to me. Are there just miles and miles of pipes holding hot water, actively losing energy as they cool? The effect of long runs of hot water lines is...
District heat is such a foreign concept to me. Are there just miles and miles of pipes holding hot water, actively losing energy as they cool? The effect of long runs of hot water lines is noticeable on the scale of a single home or small building; it must be a massive consideration when you're talking about entire cities.
Well, the bigger a pipe is, the more efficient it is. As the diameter goes up, the volume increases far higher than the surface area of the pipe where you experience losses. Bigger heating systems...
Well, the bigger a pipe is, the more efficient it is. As the diameter goes up, the volume increases far higher than the surface area of the pipe where you experience losses.
Bigger heating systems in general are a lot more efficient than smaller ones, so while you will lose some energy delivering heat to houses, in many cases you make up for that loss by having one big, efficient furnace that stores heat very well, and eliminate the need to go door to door to deliver fuel.
It blew my mind the first time I saw actual steam coming out of the street in New York and realised it wasn't just some cinematic trope to set the atmosphere! On that basis alone I can confirm...
It blew my mind the first time I saw actual steam coming out of the street in New York and realised it wasn't just some cinematic trope to set the atmosphere! On that basis alone I can confirm that they really are piping hot water/steam around cities, but I couldn't guess what the losses are like or how well the insulation manages to work.
But cities are dense, so it's not that far from the heating plant. There are a ton of them here in Berlin, and as far as I know they operate more efficient than individual heating systems per...
But cities are dense, so it's not that far from the heating plant. There are a ton of them here in Berlin, and as far as I know they operate more efficient than individual heating systems per building.
A couple of other points ... heat pumps can be designed to be much more efficient, when they can count on a steady source temperature. Residential heat pumps (most of 'em) are air-to-air,...
A couple of other points ... heat pumps can be designed to be much more efficient, when they can count on a steady source temperature.
Residential heat pumps (most of 'em) are air-to-air, extracting heat from outdoor air and moving that heat indoors ... but the outdoor temps (obviously) vary significantly. The Mannheim pump is using water from the Rhine as its source heat, where the water temp will only vary by a few degrees. That gives the engineers the opportunity to design a much more efficient heat pump.
The other thing I don't think has been pointed out ... the Mannheim project is replacing an existing coal-fired district heating system. In other words, they were already pumping hot water (or steam?) thru miles of pipes t/out the city ... the piping system is already there. They're just replacing the system that heats that water.
Honestly, reading about all the ways they can improve the efficiency and flexibility with these industrial-sized heat pumps, it's actually surprising they didn't start using them decades ago. Once they're up and running, it'll probably end up being a lot cheaper than the old coal-burning systems.
Like, literally, even burning coal to make the electricity to run the heat pumps would have been a lot cheaper and more efficient (and even more environmentally friendly) than just burning coal for heat.
Historically it was miles of steam pipes which to my knowledge was actually trickier to manage. That said, steam comes into a building at a really high temperature so I think it was about having...
Historically it was miles of steam pipes which to my knowledge was actually trickier to manage. That said, steam comes into a building at a really high temperature so I think it was about having high energy density delivered to high rise buildings to reduce the need for that onsite heat generation. But steam networks have a ton of maintenance overhead and struggle with efficiency because every small leak is wasted energy. However, leaks for that big a system are also inevitable. Hot water is easier to manage because the system can run at a lower pressure. The flip side is that it's at a lower temperature so you can't swap a steam system to a hot water system very easily.
You don't have to move hot or cold water though for a district loop. You can actually move relatively neutral temperature water (65-75 °F) and then use a heat pump in each building to adjust the temperature to where you want it. This gives you the option of running one loop and buildings being able to use the loop for either heating or cooling. With a known, steady temperature you can design a system that almost always is running at its design point which is much more efficient. At least compared to an air-source heat pump (like a typical home AC unit or heat pump) that is subject to variable outside air temperatures.
District heat is such a foreign concept to me. Are there just miles and miles of pipes holding hot water, actively losing energy as they cool? The effect of long runs of hot water lines is noticeable on the scale of a single home or small building; it must be a massive consideration when you're talking about entire cities.
Well, the bigger a pipe is, the more efficient it is. As the diameter goes up, the volume increases far higher than the surface area of the pipe where you experience losses.
Bigger heating systems in general are a lot more efficient than smaller ones, so while you will lose some energy delivering heat to houses, in many cases you make up for that loss by having one big, efficient furnace that stores heat very well, and eliminate the need to go door to door to deliver fuel.
It blew my mind the first time I saw actual steam coming out of the street in New York and realised it wasn't just some cinematic trope to set the atmosphere! On that basis alone I can confirm that they really are piping hot water/steam around cities, but I couldn't guess what the losses are like or how well the insulation manages to work.
But cities are dense, so it's not that far from the heating plant. There are a ton of them here in Berlin, and as far as I know they operate more efficient than individual heating systems per building.
A couple of other points ... heat pumps can be designed to be much more efficient, when they can count on a steady source temperature.
Residential heat pumps (most of 'em) are air-to-air, extracting heat from outdoor air and moving that heat indoors ... but the outdoor temps (obviously) vary significantly. The Mannheim pump is using water from the Rhine as its source heat, where the water temp will only vary by a few degrees. That gives the engineers the opportunity to design a much more efficient heat pump.
The other thing I don't think has been pointed out ... the Mannheim project is replacing an existing coal-fired district heating system. In other words, they were already pumping hot water (or steam?) thru miles of pipes t/out the city ... the piping system is already there. They're just replacing the system that heats that water.
Honestly, reading about all the ways they can improve the efficiency and flexibility with these industrial-sized heat pumps, it's actually surprising they didn't start using them decades ago. Once they're up and running, it'll probably end up being a lot cheaper than the old coal-burning systems.
Like, literally, even burning coal to make the electricity to run the heat pumps would have been a lot cheaper and more efficient (and even more environmentally friendly) than just burning coal for heat.
Historically it was miles of steam pipes which to my knowledge was actually trickier to manage. That said, steam comes into a building at a really high temperature so I think it was about having high energy density delivered to high rise buildings to reduce the need for that onsite heat generation. But steam networks have a ton of maintenance overhead and struggle with efficiency because every small leak is wasted energy. However, leaks for that big a system are also inevitable. Hot water is easier to manage because the system can run at a lower pressure. The flip side is that it's at a lower temperature so you can't swap a steam system to a hot water system very easily.
You don't have to move hot or cold water though for a district loop. You can actually move relatively neutral temperature water (65-75 °F) and then use a heat pump in each building to adjust the temperature to where you want it. This gives you the option of running one loop and buildings being able to use the loop for either heating or cooling. With a known, steady temperature you can design a system that almost always is running at its design point which is much more efficient. At least compared to an air-source heat pump (like a typical home AC unit or heat pump) that is subject to variable outside air temperatures.