3 ms·

Operating at such deep levels and high temperatures presents many challenges that can be avoided with lower overall temperatures and shallow wells. Eg: My resi

Operating at such deep levels and high temperatures presents many challenges that can be avoided with lower overall temperatures and shallow wells. Eg: My residential well is at least +32F whilst the ambient outside temperature is -40F. I know this through observation of water flowing out of my tap and an outdoor thermometer. This provides a temperature difference of >72F which can be extracted through simple heat converters and then multiplied by compression to achieve temperatures sufficient for steam production. By exploiting the physical properties of steam condensation vast amounts of energy can be produced during this state change. I understand this report is directed towards large scale energy production with 30 year+ timelines but believe smaller decentralized solutions have many benefits over these large projects. I also do not understand why "Closed-loop" terminology is implying that this system is something new or distinct as all geothermal systems to my knowledge use closed loop systems to prevent environmental damage.(Other than possibly a water wheel at Yellowstone?)

deleted 5y ago
[deleted]
blacksqr 5y ago
>I also do not understand why "Closed-loop" terminology is implying that this system is something new or distinct as all geothermal systems to my knowledge use closed loop systems to prevent environmental damage Large-scale geothermal systems attempted up to now have generally been of the the type where you frack deep underground rock, then dig two wells into the fracked rock field, pump cool water into one and let it heat as it percolates through, then pump it back out the other. This as you mention carries the potential for environmental damage, but has been seen as necessary to overcome the problem of rock's slow thermal recharge rate. The linked paper suggests the rock thermal recharge problem can be overcome by digging not one but several horizontal pipes connecting the two deep vertical wells.
- mojomark 5y ago
  I also was not aware of that open loop scheme. Seems like a simple and lower cost, albeit inefficient, solution. Thanks for sharing.
- sigmaprimus 5y ago
  I was not aware they used such methods, I assumed they would use a glycol type solution to achieve better heat transfer and enable the transfer of heated media within a closed loop system of piping or well jackets. I find it shocking that they have been employing the tactics You described above, especially under the guise of a renewable alternative energy that is good for the environment.
seanwoods 5y ago
Not all geothermal systems are closed loop. I have an open-loop geothermal system at my house on Cape Cod, MA. It uses the same water pump I use for my domestic water, runs it through the heat pump, and discharges back to the aquifer via another well drilled exclusively for this purpose.
- sigmaprimus 5y ago
  Interesting, do you also take advantage of the excess amount of water being pumped through your system with a reverse osmosis system? I would imagine this would be of great benefit if You are already moving the water to heat and cool your home.
mojomark 5y ago
I had the same reaction about the "closed loop" highlight in the title. An open loop system seems very wasteful and hard to maintain. Your comment on decentralized application caught my attention. I agree with you. While there are clear merits to gaining economies of scale, there are often diseconomies of scale that go overlooked - which would make smaller decentralized applications more attractive. The trade largely comes down to lowering require capital expenditure ($/resource generated, e.g. $/kW) in order to gain operating flexibility (which can lower overall operating costs - though those savings are normally excluded from the published $/resource value, hence overlooked). Think of the merits of everyone having a car instead of trying to move people to-and-fro using trains. Sure, you pay less $/mile traveled, cumulative carbon emissions/mile are generally lower, and you avoid wear and tear on your car. BUT, you have to pay for taxis or rental car when you arrive at your destination, so you pay an inflated amout to restore flexibility. The cost for 'last mile' transit certainly isn't reflected in your train ticket cost. As a side study I've been wrestling with this problem in my industry (commercial ship design) for the past decade. One challenge is that it's hard for a corporation investing in the infrastructure to sell these decentralized units to achieve a profit margin competitive with a large-centralized product. The solution, I believe, is to figure out how to evalutate and factor in the cost of loss of flexibility in the $/resource calculation. That hasn't been an easy nut to crack.
noveltyaccount 5y ago
"By exploiting the physical properties of steam condensation vast amounts of energy can be produced during this state change." Can you expand on this, or provide a reference?
- sigmaprimus 5y ago
  https://en.wikipedia.org/wiki/History_of_the_steam_engine#:~:text=In%20the%20engines%20of%20Newcomen,)%2C%20to%20move%20the%20piston https://en.wikipedia.org/wiki/History_of_the_steam_engine#:~....

deleted 5y ago

[deleted]

blacksqr 5y ago

>I also do not understand why "Closed-loop" terminology is implying that this system is something new or distinct as all geothermal systems to my knowledge use closed loop systems to prevent environmental damage Large-scale geothermal systems attempted up to now have generally been of the the type where you frack deep underground rock, then dig two wells into the fracked rock field, pump cool water into one and let it heat as it percolates through, then pump it back out the other. This as you mention carries the potential for environmental damage, but has been seen as necessary to overcome the problem of rock's slow thermal recharge rate. The linked paper suggests the rock thermal recharge problem can be overcome by digging not one but several horizontal pipes connecting the two deep vertical wells.

mojomark 5y ago
I also was not aware of that open loop scheme. Seems like a simple and lower cost, albeit inefficient, solution. Thanks for sharing.
sigmaprimus 5y ago
I was not aware they used such methods, I assumed they would use a glycol type solution to achieve better heat transfer and enable the transfer of heated media within a closed loop system of piping or well jackets. I find it shocking that they have been employing the tactics You described above, especially under the guise of a renewable alternative energy that is good for the environment.

seanwoods 5y ago

Not all geothermal systems are closed loop. I have an open-loop geothermal system at my house on Cape Cod, MA. It uses the same water pump I use for my domestic water, runs it through the heat pump, and discharges back to the aquifer via another well drilled exclusively for this purpose.

sigmaprimus 5y ago
Interesting, do you also take advantage of the excess amount of water being pumped through your system with a reverse osmosis system? I would imagine this would be of great benefit if You are already moving the water to heat and cool your home.

mojomark 5y ago

I had the same reaction about the "closed loop" highlight in the title. An open loop system seems very wasteful and hard to maintain. Your comment on decentralized application caught my attention. I agree with you. While there are clear merits to gaining economies of scale, there are often diseconomies of scale that go overlooked - which would make smaller decentralized applications more attractive. The trade largely comes down to lowering require capital expenditure ($/resource generated, e.g. $/kW) in order to gain operating flexibility (which can lower overall operating costs - though those savings are normally excluded from the published $/resource value, hence overlooked). Think of the merits of everyone having a car instead of trying to move people to-and-fro using trains. Sure, you pay less $/mile traveled, cumulative carbon emissions/mile are generally lower, and you avoid wear and tear on your car. BUT, you have to pay for taxis or rental car when you arrive at your destination, so you pay an inflated amout to restore flexibility. The cost for 'last mile' transit certainly isn't reflected in your train ticket cost. As a side study I've been wrestling with this problem in my industry (commercial ship design) for the past decade. One challenge is that it's hard for a corporation investing in the infrastructure to sell these decentralized units to achieve a profit margin competitive with a large-centralized product. The solution, I believe, is to figure out how to evalutate and factor in the cost of loss of flexibility in the $/resource calculation. That hasn't been an easy nut to crack.

noveltyaccount 5y ago

"By exploiting the physical properties of steam condensation vast amounts of energy can be produced during this state change." Can you expand on this, or provide a reference?

sigmaprimus 5y ago
https://en.wikipedia.org/wiki/History_of_the_steam_engine#:~:text=In%20the%20engines%20of%20Newcomen,)%2C%20to%20move%20the%20piston https://en.wikipedia.org/wiki/History_of_the_steam_engine#:~....