I happened to get a tour of our geothermal district heating building last week, it was really interesting.
The entire neighbourhood of about 2200 houses is heated and cooled by this installation.
About 60% comes from the heat pumps that get their water from two well pairs, about 40 and 80 meters deep. It's not a closed system and the ground water flows about 50-100 meters to either pair.
The remaining capacity comes from a gas turbine that generates electricity to sell back to the net, and the residual heat is captured and used to heat the district. If the demand isn't there, it's pumped back into the ground for future use.
The third method is what amounts to basically a giant electric kettle, which has the worst COP factor, but there are times here in The Netherlands when energy prices are negative, and that's when they shut down the gas turbine and use the electric heater instead.
There are three pipes going to every house in the district, one with hot water, about 70 degrees and used for both floor heating and hot water, one with cold water for cooling in the summer, and a return pipe.
It removes a lot of infrastructure from your house, the hot water goes directly in your floors, so no boilers or furnaces. There's a small heat exchanger that warms the tapwater for showers, and you have zero maintenance.
That's too bad. What is known here as geothermal and ground heat are completely different. What should actual geothermal (nuclear decay heat) then be called in the USA?
From what I understand geothermal itself refers to heat of the earth (crust) while geothermal energy refers to energy generated within the earth mainly but not exclusive, nuclear decay. Calling ground heat geothermal is therefore correct, calling it geothermal energy is not.
(see: https://education.nationalgeographic.org/resource/geothermal...)
Yea, there’s also leftover energy from the earth’s formation. Nuclear decay + moon + sun (tides and sunlight) + residual heat together all contribute to the amount of available energy.
That's pretty amazing. Is floor heating enough in the winter? Can you turn up the temperature if needed? In the house I am in right now the floor heating is not enough, they had to add radiators. All electric.
That is amazing. I would have made a special trip to see that - I just got back from NL. How involved is it there to get the new pipes into those homes? If you could supply any URLs or geo clues I’d appreciate it!
Edit: was this a new from scratch development or a retrofit? I realize my plumbing question might be irrelevant.
Two heat exchangers, one big for the hot water, one smaller for the heating. Heat comes in the form of water at 10bar/75°C. Everything is packed in a box having the a size of 1m (H) x 50cm (L) x 30cm (D). Isolated delivery pipes are all under the city block.
We have that at home, this is great. No noise, no maintenance, no emissions. The only downside is that you are "locked in" with a single heat provider.
My best friend family built a house 15 years ago, when the tech was new-ish, and the pipes are under the cement and inaccessible without huge costs. Then their house settled a little over the years and it lead to maintenance issues.
I suppose new installation don't have the issue, but for stuff I'll use for a long time (basically house, computer and car), if I don't know how to repare it, I prefer old tech.
Wouldn't you need pipes anyway for regular plumbing? That would have lead to issues anyway, right? Also I doubt somewhat the tech was new 15 years ago, it's quite common in germany to use district heating, especially if there's a source nearby you can use or it's a bigger city. So I am pretty sure district heating is very old-tech, just geothermal source is new. German wikipedia says:
> About 9 % of the total heat demand in Germany is covered by heat grids today and 14 % of the demand for residential buildings.
It's less efficient than lower temperatures, but this district is built without gas lines to the houses (as is normal in The Netherlands till recently), and it's more efficient than everyone having an electric boiler in their house.
The pipes are well insulated and apparently the energy loss quite manageable.
The efficiency mostly comes from _moving_ heat that already exists, instead of creating new heat.
Depending on the specifics, that's often about 5x more efficient.
Counterintuitively - the "heat" source doesn't have to actually be hot. In theory as long as it's above absolute zero it can be used as a heat source to heat up the inside of your home. It's the same for cooling - even if it's hot indoors and really hot outdoors, you can still use a heat pump to make it even colder inside the hosue.
I feel that it is wrong to conflate "ground source heat pump" with "geothermal".
Ground source heat pumps use the soil or ground water as a low temperature mass to draw heat from. Surface soil follows air temperature, with a lag because of its high thermal mass. Below a meter or so this lag becomes so large that it just stays at the annual average of the air temperature. So the heat is not coming from the earth below!
I would reserve the word "geothermal" for projects that actually access high temperature sources, where the heat does actually "come from below".
To clarify for those who don't feel like reading: New Apartment building will use geothermal heat pump to reduce heating and cooling energy use [and cost]. Some people may read the title and think the building is generating its own electricity from geothermal energy... This is not that.. that would require profoundly deep boring and other sophisticated technology.
There seems to be some confusion as to whether this is "true" geothermal energy or not. Conceptually anything that taps underground heat sources is geothermal energy [1], but the technology used and the possible applications depend significantly on whether we are talking about a geologically active part of the crust (higher than normal temperatures) such as those found near tectonic plates boundaries, volcanoes etc. The technical term is high enthalpy versus low enthalpy sources. [2]
It would be really cool (pun) if the much more widely available low enthalpy option could produce electricity but it seems that this in not possible (yet?). High enthalpy plants have a range of complications as the fluid being used is full of chemicals.
Not geothermal in the sense you might be thinking (tapping into geysers); rather, it is taking advantage of underground temperature remaining constant around 55F, essentially using the soil underground as a giant and consistent heat sink / heat source.
My first thought was whether heat demands would overwhelm the capacity of the ground, but I read that soil has a thermal mass about 1/5th of water so a rule of thumb might be that you don’t have to worry unless more than about 15% of the total volume underground is replaced with heat pipes, which it is definitely not (first concrete numbers I could find suggested 10cm boreholes spaced 5 meters apart, which is less than 1% of ground volume).
FYI: You can actually deplete the ground temp over time, but drilling further down helps as does storing excess heat in summer to raise the temp below a bit (yay! free cooling!). There's a ton of research on this and these kinds of systems are very common in Europe. They go very well with floor/ceiling (i.e. radiant-based) heating systems as opposed to the more common air-based heating systems used in the US. It's also _way_ more energy efficient.
Interestingly, mixed over/underground tunnel systems like the London Underground effectively pumps heat back underground (the trains heat up from both the sun and braking etc., and radiate that heat into the tunnels) to the point where the clay surrounding the London Underground tunnels is many degrees hotter now than when the London Underground opened. Cities with underground systems might effectively have a lot of excess heat available to pump out. There's some feasbility study being done on reusing waste heat from ventilation, but I don't know if there's been any work done on to what extent the London Underground heating of the ground in the city centre does to the efficiency of ground source heat pumps.
Yeah, that was my though as well. If every building in Brooklyn tried to do this I'm not sure what would happen to the foundations of the buildings and I think the ground would just converge on some temperature that was just high enough to keep using the system but not that practical either.
While this may be novel in residential buildings in the U.S. there are a number of college campuses that have been going this route (providing a large number of buildings with heating/cooling/hot water via a centralized system that leverages heat pumps and the earth's thermal mass) for awhile. See for example: https://energynews.us/2022/02/07/colleges-see-untapped-poten...
I was kind mad I didn't know about geothermal when my house was built. I would have definitely gone with it. Installing it would have been cheap as the ground was all dug up already.
I wonder if this is because of the NYC law that was passed prohibiting gas connections to buildings.
It says the swimming pool will be heated with geothermal energy. Would not that make the temperature cold? It would be better to use solar power to heat the pool.
Heat exchangers should be given a heavier role here. Heat emissions from the refrigerators plus air conditioners should heat the central water heater and boilers.
They must be using a heat pump (from the ground source) for the pool, otherwise yes it would be way too cold.
I have often thought about the idea of using heat from refrigerators but I think that would be more trouble than it's worth for small domestic fridges. But definitely if they have this ground source system, they use that as a shared heat reservoir that the heat pumps air conditioning apartments in summer reject heat into and the heat pumps heating hot water draw from.
I've only heard of ground loops being used for when heat pumps have to operate in absolutely frigid temps (like < -20F). What's the efficiency improvement over using ambient air? NYC doesn't get too far below freezing, even in the dead of winter, and I hear modern refrigerants are pretty dang good.
1. You get passive cooling in the summer
2. The greater the temperature difference is the more efficient the pump becomes so they are more efficient even in not so cold weather
3. The maintenance costs of the system are significantly less. You need to clean and replace blower fans. Cleaning has to be done yearly or twice yearly depending on environment. Ground source, you only need to maintain the pump and coolant which needs replacing cca once every 20-30 years.
It's not entirely passive, you have to have a pump that moves the water through the loop, but it can cool the house without running a heatpump, with just passive heat exchange. Or with the heatpump running at a minimal level because when it is really hot outside, the ground is relatively comfortably cold.
So they will invest probably hundreds of thousands of dollars into a tech that will make them use a lot less electricity for heating and cooling, only to stop using that technology 5 years later and pay for expensive energies? Or will they completely uninstall the heat pumps?
The thing with this kind of investment is, it's cash heavy at the beginning and then lets you save a lot of money. It makes no sense to ditch the installed technology once it's working for you and saves you money.
I believe a government grant paid for the system. The article neglected to mention that. It’s conceivable that there may be other things that went unmentioned in the article.
I live down the street. Here’s what the developer’s website has to say:
> Lendlease acquired $4 million in support from the New York State Energy Research and Development Authority (NYSERDA) to build a geoexchange system at 1 Java Street.
Probably because people will steal the heat pumps.
There are apartment buildings going up in NYC with one-pipe steam heat, steel pipes, and cast-iron radiators, because there is nothing outside the boiler room worth stealing.[1]
The heat pumps are located where the boiler room would be ;-) so... they're about as easy to steal as a boiler. Size is also similar - not that easy to stuff into your pants and walk of whistling.
The entire neighbourhood of about 2200 houses is heated and cooled by this installation.
About 60% comes from the heat pumps that get their water from two well pairs, about 40 and 80 meters deep. It's not a closed system and the ground water flows about 50-100 meters to either pair.
The remaining capacity comes from a gas turbine that generates electricity to sell back to the net, and the residual heat is captured and used to heat the district. If the demand isn't there, it's pumped back into the ground for future use.
The third method is what amounts to basically a giant electric kettle, which has the worst COP factor, but there are times here in The Netherlands when energy prices are negative, and that's when they shut down the gas turbine and use the electric heater instead.
There are three pipes going to every house in the district, one with hot water, about 70 degrees and used for both floor heating and hot water, one with cold water for cooling in the summer, and a return pipe.
It removes a lot of infrastructure from your house, the hot water goes directly in your floors, so no boilers or furnaces. There's a small heat exchanger that warms the tapwater for showers, and you have zero maintenance.