[Wolfhart Willimczik (OP)]

Hi all together,
I am taking the liberty to present you my newest invention.
"Ultra deep hydroelectric/geothermal power plant"
https://hardballsite.wordpress.com/ [nofollow]

ABSTRACT

This invention consists mainly of a long sloped tunnel, a deep hydroelectric/geothermal power plant and hot rocks transforming water into steam. Advanced tunnelling machines are able to reach lengths and depths never possible before with the old drilling method.
The drop height of the water for the hydroelectric power plan is for instance over 10 km and the gained water pressure over 1000bar feeding special high pressure water turbines or big hydraulic water motors driving again generators. After passing the water turbines the water is pressed with a rest pressure of about 250bar into hot rocks generating high pressure overheated steam for steam turbines in a range of gig watts. Then the steam rises up in the sloped tunnel as in a chimney, cools down, condensate to water and starts the entire process again. That’s all.
This circulation for generating electrical energy deep under ground is sustainable, even during an ice age with a minimum of human intervention. It is most environmentally friendly and can be build in any country making them more independent from oil.

Referring to FIG 1, there is shown a schematic cross section of the entire creation, but the drawing is not true to scale.
There is a 50 km long tunnel 1 like the Gotthard tunnel, but with a slope of 30°.
At a maximal deepness of about 20 km – depending on the local temperature – is a power plant with many turbines in horizontal tunnels 2 and 3. Even deeper is a smaller branch 4 of the main tunnel made by remote controlled tunnel machines. The region 13 of the pores hot rocks is un-cooled over 800° C , but will get cooler if pressure water is injected through the pipe 14 and an array of nozzles 9. The hot pressurized steam is collected in the lower portion of the tunnels 1 and 4. A heavy cover 19 separates the hot steam from the rest of the tunnels. Water will fill up a portion of the tunnel over the cover. This helps to lock the cover down against hot steam of about 200bar pressure. At a thickness of 2 km water would be a balance. There is a pipe connecting both deep sees for spill over. All 3 water bodies have the same level. To lower the water level there is an extra pump 24 to press the water into the hot pressurized region back in the circulation. This pump runs only if needed. The condense water from above has enough pressure to penetrate the hot rocks even with the detour over the water turbines 8.
The power plant can go on generating electricity only with the water in the own deep sees. If the condensation in the long tunnel is complete, no water from above is necessary any more.
The process is very simple. Firstly clean water from a river 6 is getting through a screen 5 and runs without any pump through an about 50 km long pipe 7 gaining gravitational pressure of about 2000bar at a deepness of 20 km feeding the high pressure water turbines 8 or water hydraulic motors (Wolfhart Principle). With a rest pressure of about 250bar the water is running through the pipe 14 and is injected with nozzles 9 into hot rocks 13 where the water is changed into steam and collected under the cover 19. A pipe 18 feeds the steam turbines 12 with about 170bar at 580° C - each generating about 250 MW electricity like the SST900 from Siemens. They are 11 m wide and fit in the tunnels. They drive down on a rack railway very slowly. Good brakes are essential, otherwise the heavy load will run down in the hot rocks and never seen again.
The workers or intranauts respectively must work in the beginning under 2bar pressure and in a hot environment. They look like astronauts in their cooling suits. They must be brought slowly back to the surface like divers from a 20 m water depth or they stay in the deep “hotels” for days. There are cooled areas with normal pressure in the horizontal tunnels, but there will be a steamy and wet ride back home on the rack trail in cabins. To stop the steam production would mean to shut down the steam turbines. Therefore, a second tunnel could be made or one tunnel will be divided in sections for water, steam and people.
After passing the steam turbines the steam rises up in the tunnel and cools down. At last it will condense in a heat exchange system 10 close under the surface of the earth 11. The condense water will be collected and runs down again a long pipe and feeds first the water turbines again and then it is changed into steam again. In the best-case scenario no water from the river is necessary any more. It is a closed sustainable circulation as in nature. The deep tunnel has it’s own weather system. There are no big pumps necessary.
Not 100% of the water can be recaptured under the heat exchanger 10, but in different heights other water collecting stations can be installed. For instance the water from a 10 km height runs down in an extra pipe and enters an extra turbine still running with 1000bar instead with 2000bar static pressure.
The air pressure down there is about 2bar – like in a tire of a car or 20 Meter under Water. Therefore, strong hermetic doors 17 close the horizontal tunnels up. There is only a small tunnel connecting both for the intranauts going around the sloped tunnel. It could be made also only one horizontal tunnel, but 2 are better for redundancy.  A comfortable climate is made behind these doors. Temperature and pressure are lowered. The electrical power cables are placed inside the cool water pipes for cooling purposes in the hot regions. All walls are cooled by fresh water in pipes 16 from above. A small see 15 holds fluctuations in temperature down. There is even a kind of hotel “Deep View” 20 for intranauts – contrary to astronauts - with a view of the bright illuminated small see and another “hotel” called “hot rock” 21. It is also a shelter for the workers in an emergency with all live supporting things. It can be extra hermetic closed. For redundancy every important installation is doubled. In time most work is done by robots or remotely.
If the tunnelling machine is driven by water hydraulic motors and everything is totally water-cooled it can drill in hot layers – even under water. The tunnelling machines 22 and 23 remain on the grounds of the tunnels and go further if needed and still running.
The predictions are made after about 100 years experience with this technology. It will work already at much lower deepness, but not that efficient.
The simplest way would be to let the water run down permanently and let the steam come up to the power station on the surface of the earth as it is done in smaller versions without tunnelling. Some heat loss will occur for the steam in the wide long tunnel. For injecting the water in the hot rocks there is no water pump necessary, because the tunnel brings the low air pressure to the rocks below. There is building up a low-pressure zone in the rocks surrounding the tunnel or shaft.

[evan_au]

At a maximal deepness of about 20 km

I understand that the typical temperature rise with depth is about 25C per km.
So as you say, a very deep tunnel is needed to obtain high temperatures for electricity generation (ie expensive).

So it is usually more economical to find locations where there is a magma body at shallower depths, so the thermal gradient is greater (eg Iceland or New Zealand).

Then the steam rises up in the sloped tunnel as in a chimney, cools down, condensate to water and starts the entire process again.

The amount of energy you can extract from a heat source (like geothermal energy) is determined by the difference in temperature of the heat source and a cold sink.

Shallower rocks start off at a lower temperature than deep rocks. But rocks have fairly poor thermal conductivity, so as soon as you try and put heat into them, they heat up; when the temperature matches the heat source, you generate no more power.
           - It is more efficient to have your cold sink on the surface - eg evaporation towers or the ocean

runs down again a long pipe and feeds first the water turbines again

In theory, Electricity output really doesn't matter where you put your generators - on the surface or deep underground

But operating costs are radically different between the surface and deep underground.
          - At elevated temperatures and dripping water deep underground, the generators will always be breaking down
          - the electrical conductors will be arcing over
          - Engineers and Technicians can't easily reach the equipment to service it, because the access tunnel is full of hot water.
          - It's much better to put the active equipment on the surface, where it can be air-cooled, and accessible for maintenance

[Wolfhart Willimczik (OP)]

At a maximal deepness of about 20 km

I understand that the typical temperature rise with depth is about 25C per km.
So as you say, a very deep tunnel is needed to obtain high temperatures for electricity generation (ie expensive).

So it is usually more economical to find locations where there is a magma body at shallower depths, so the thermal gradient is greater (eg Iceland or New Zealand).

Thank you for your replay. I will try to answer everything. 20 km is indeed the worst case scenario. I choose this to show that every country on earth can get a strong and cheap energy source – to avoid political tensions as occur with oil.
I think in most cases are 10 km good enough. The simple rule is: One has to dig until it is hot enough. Some places are better – some worse.

Then the steam rises up in the sloped tunnel as in a chimney, cools down, condensate to water and starts the entire process again.

The amount of energy you can extract from a heat source (like geothermal energy) is determined by the difference in temperature of the heat source and a cold sink.   -right

Shallower rocks start off at a lower temperature than deep rocks. But rocks have fairly poor thermal conductivity, so as soon as you try and put heat into them, they heat up; when the temperature matches the heat source, you generate no more power.
           - It is more efficient to have your cold sink on the surface - eg evaporation towers or the ocean

There is practical a cooling tower (10 km high) with a heat exchanger on the surface. Do you see?
To enlarge the surface of the hot rocks many smaller tunnels and Fracking is employed as it is made already. Don’t forget the water has already at 10 km 1000 bar – free of charge! This opens up all the cracks in the rocks. (Today are used about only 100 bar)

runs down again a long pipe and feeds first the water turbines again

In theory, Electricity output really doesn't matter where you put your generators - on the surface or deep underground  right

But operating costs are radically different between the surface and deep underground.
          - At elevated temperatures and dripping water deep underground, the generators will always be breaking down
          - the electrical conductors will be arcing over
          - Engineers and Technicians can't easily reach the equipment to service it, because the access tunnel is full of hot water.
          - It's much better to put the active equipment on the surface, where it can be air-cooled, and accessible for maintenance

This is a great thing that electricity don’t loose power up or down, but the steam looses energy.
You are perhaps an engineer and you want everything on the surface – understandable, but there are great disadvantages also.
In Scientific America there is a strong argument against deep geothermic power plants:
„…This looses at least a third of the available power.”
For efficient power generation, you need several hundred degrees C of temperature difference. up to 600 or 800 degrees C is good.
Ergo, the turbines must be there where the hot steam is.
There are not many workers (intranauts) down and the control station is on the surface, but a second one down there in case the one on the surface is bombed or the like.
I would like also a second tunnel for the intranauts, the Gottard has actually 2 tunnels.
Down there the machinery has the same climate as on the surface – or better. In south Africa a 5 km deep shaft is cooled with ice – 15 t per hour. I see even better ways. Think on the free water pressure of 1000 bar. There is a lot, what you can do with it, for instance build a huge cooling system…

Do you know that in Germany there are protestors on the fence to geothermal power stations?
The operating company would love it, if everything could disappear on the surface  and only a cable comes out of the earth – even if it cost money.