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Geothermic power plant Grünwald

Jerome Marot

Well-known member
Grünwald is a (rich) city south of Munich, Germany. Population: about 11000 people. As is often the case in Germany, the city is heated by a central system, meaning there are hot water pipes running under the streets delivering heat to the individual homes. This centralised system has the advantage that the central heat source can be optimised to save energy. Some power plants burn waste, generate electricity and distribute the heat generated. In Grünwald, they chose to pump heat generated by our planet. There is an aquifer running down the alps under the whole of south Bavaria, manifesting itself by hot springs in Erding north of Munich, for example. Deep under Grünwald, the water runs at 130°C. This is a general view of the station:

2603


What you see here are the exits of the inlet and outlet pipes. The pipes go down 4km to the aquifer. They pump hot water out (130°C) and, after the heat has been used, reinject it down at about 50-60°C. The pump is 600m below the surface. The station pumps about 140l/s. The whole complex produces 40MW of heat.
 
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Jerome Marot

Well-known member
This second view is from another angle to the left of the picture above.

2604

The pipes lying down to the right are replacement pipes for the down hole. The twin chimneys are for the generator producing the energy for the pump (2 MW electric, waste heat is reinjected into the system). They are also used for a backup classical heating system. In case the pump breaks, they need back up or the whole city would freeze.
 
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Jerome Marot

Well-known member
The water from the aquifer is brought to a set of heat exchangers where it heats the distribution circuit. These are the heat exchangers, inside the building with the two chimneys:

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The heat exchangers are the black elements at the center of the picture. The green-blue liquid to the right is adblue (urea) for depollution of the power generators.
 
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Jerome Marot

Well-known member
The heat exchangers and the whole circuit of aquifer water needs to be carefully treated and designed to avoid scaling. The aquifer water is charged in minerals that will easily precipitate and clog the system otherwise:

2606
 

Jerome Marot

Well-known member
The second circuit for distribution is several km long. To protect it, demineralised and deoxygenated water is used. These are the pumps feeding that second circuit:

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Jerome Marot

Well-known member
As I said, the whole system is mainly used to generate heat. Warming homes is one of the main contributors to CO2 production in Germany, more than private transport for example. The temperature of the aquifer is ideal for that use. Nevertheless, when heating is not used, electricity is produced. It happens there:

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To the right of the picture, the massive cooling system of the generator. Because of the relative low temperature of the heat source, an organic Rankine turbine is used (basically, a steam turbine where water is replaced by a fluid with a lower boiling point, isobutane is used here). From the ~40 MW, only 3.5 MW can be produced. The turbine itself is in the small building to the left, in front of us the steam generator.
 

Jerome Marot

Well-known member
The whole station was built for 13,9 Mio € in 2012. Drilling the two holes 4km under surface cost 26,8 Mio €. The electricity organic Rankine cycle installation added another 11,3 Mio €. This station is linked to a second one in Unterhaching by a 20 MW and 5,3 km heat transfer pipe, built for 7,4 Mio €.
 

Asher Kelman

OPF Owner/Editor-in-Chief
Is the technology fixed or is it designed with the idea of updates to increase efficiency and durability or will this be replaced in say 30 years time?

Asher
 

Jerome Marot

Well-known member
Is the technology fixed or is it designed with the idea of updates to increase efficiency and durability or will this be replaced in say 30 years time?
They can replace elements, for example the pump which sits 600m underground. But the largest investment is in drilling the down holes and laying 100km of pipes to distribute the heat. Replacing this investment means starting anew.
 

Jerome Marot

Well-known member
Has anyone calculated the savings to the users for this heating system as opposed to natural gas?
I don''t really understand. It needs to be cheaper to the end users, there is no obligation to connect to the system and citizens of Grünwald can still chose to run a gas, oil or wood heating. The price list for the service is here: http://www.erdwaerme-gruenwald.de/Startseite/Fuer-unsere-Kunden-Interessenten/Preisgestaltung/Waermepreise/E1135.htm but you would need to compare the prices in the Area for other heating systems.
 

Asher Kelman

OPF Owner/Editor-in-Chief
Thanks! But in terms of helping the environment, even if it’s much more expensive, then the planet is still better off. Is tgatcright.

Does “more money spent” have any carbon print?

I don’t think so, but I don’t know the economic theory or the math.

Asher
 

James Lemon

Active member
Newton’s Law of Cooling states that the rate of change of the temperature of an object is proportional to the difference between its own temperature and the ambient (or surrounding) temperature. The cooler the interior of your home gets (relative to outside temperature), the slower the heat loss. In other words, your home loses heat energy more quickly at 72°F than it does at 62°F because heat transfer slows down as the difference in temperatures gets closer to thermal equilibrium. This includes structures in the home like fireplaces and interior walls of house that act as thermal masses that store infrared heat and release it overtime.

Knowing this will save you money and use less energy regardless of the type of heating system used.




James
 
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Asher Kelman

OPF Owner/Editor-in-Chief
Newton’s Law of Cooling states that the rate of change of the temperature of an object is proportional to the difference between its own temperature and the ambient (or surrounding) temperature. The cooler, [my emphasis], the interior of your home gets (relative to outside temperature), the slower the heat loss. In other words, your home loses heat energy more quickly at 72°F than it does at 62°....
James,

You have explained it somewhat backwards. To clarify in winter it’s cold. So we heat the interior. You put the heat on. It can’t become cooler as you suggest. It’s say 5 degrees warmer now. It is now 67 degrees inside and still 62 degrees outside.

Let’s measure the total heat loss at X Joules per hour.

Now we go that extra 5 degrees to 72 and measure, and after many hours, measure the total heat loss once more.

The result would be 2 X Joules/hr as heat lost increases proportionally as the indoor difference in temperature increases!

So heat loss increases proportionally to the increases in inside temperature.

I think that’s what you were trying to say!


Asher
 

James Lemon

Active member
James,

You have it backwards. In winter it’s cold. So we heat the interior. You put the heat on. It can’t be cooler!! It’s say 5 degrees warmer now. It is now 67 degrees inside and still 62 degrees outside.

Let’s measure the total heat loss at X Joules per hour.

Now we go that extra 5 degrees to 72 and measure, and after many hours, measure the total heat loss once more.

The result would be 2 X Joules/hr as heat lost increases proportionally as the indoor difference in temperature increases!

So heat loss increases proportionally to the increases in inside temperature


Asher
Asher

If you want to argue with Newtons Law of cooling that is up to you but heat travels toward the cold,simple.
 

Asher Kelman

OPF Owner/Editor-in-Chief
Asher

If you want to argue with Newtons Law of cooling that is up to you but heat travels toward the cold,simple.
Not arguing at all. Just respectfully quibbling about the explanation’s language. Your own understanding of Newton is unquestioned!

Asher
 

James Lemon

Active member
I understand that the less you heat your home, the less money you spend. True, but it was obvious before Newton was born.
Jerome

That is not the point. Many people believe that by maintaining a consistent comfortable temperature in their home has less load on their heating system even while they sleep or are away from home for a long period of time. However the opposite is true by lowering your heat at night your system will work less and hold the heat for a longer period of time. Bringing the heat back up to a comfortable temperature is less work on your system than most people think. I can control my heat at home from my phone so that I can crank up the heat just prior to arriving so it's nice and cozy when I get their. I can program it to do whatever I want it to do depending on my routine. No point in keeping the heat cranked up while cooking or sleeping or while your at work.
 

Jerome Marot

Well-known member
Your point might be true, but is not proven by Newton. It depends on factors like the losses in the heating system when increasing temperature, which may be higher than when maintaining temperature constant.

In a first approximation and when using electric heaters (which are not what is pictured here), what you say is generally true.
 

James Lemon

Active member
Your point might be true, but is not proven by Newton. It depends on factors like the losses in the heating system when increasing temperature, which may be higher than when maintaining temperature constant.

In a first approximation and when using electric heaters (which are not what is pictured here), what you say is generally true.
Jerome

If it was 40 below outside and your temperature is set a 20 Celsius inside and you then turned off the heat, it would dissipate at a much faster rate than a setting of 16 Celsius regardless of how many losses in the system. That’s the point!

James
 
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