As Bitcoin mining continues to flourish in the US, miners will continue to seek out and utilize cheap or stranded energy. Many miners have found opportunities in West Texas, but the harsh environment brings many challenges, namely how to deal with the heat of the harsh landscape. Up to this point, miners have found clever ways to continue hashing in the peak of hot Texas summer including underclocking the machines, lowering the power usage and heat generated, and also we’ve seen big investments in immersion cooling.
While underclocking and immersion have their pros and cons, I hope to outline a new possibility in mining in the harsh desert environment: enter geocooled mining. The high-level idea is to create a closed-loop air circuit underground and use the soil as a heat exchanger to cool the air. This would require burying hundreds of feet of concrete pipe, however, the long-term maintenance and upfront cost could make up for the headache of plumbing the pipes.
Understanding the baseline thermals
Let’s set the baseline for this proposal. We will use the following infrastructure and assumptions:
- (100) Bitmain S19j Pro 100t
- Bitmain S19j Pro 100t cost $5,000
- Factory Firmware
- BTCUSD $20,000
- $0.04 kWh
With these assumptions let’s now break down how this might work. For this model, we will assume a wall of 10×10 S19j Pros mounted inside the shipping container.
To calculate the required airflow needed to cool a wall of 10×10 S19j Pro miners, we need to consider several factors such as the thermal output of the miners, the ambient air temperature, and the desired operating temperature range.
Assuming that the ambient temperature is 25 degrees Celsius (77 degrees Fahrenheit) and the desired operating temperature range for the miners is between 60 to 75 degrees Celsius (140 to 167 degrees Fahrenheit), we can estimate the thermal output of a single S19j Pro to be around 3,000 watts.
For a wall of 10×10 S19j Pro miners, the total thermal output would be around 300,000 watts (10 x 10 x 3,000). To calculate the required airflow to cool this wall of miners, you can use the following formula:
- Airflow (CFM) = Thermal Output (W) / (1.08 x Temperature Difference (°F))
- Where 1.08 is a constant representing the specific heat of air at standard conditions.
Assuming a temperature difference of 20 degrees Celsius (36 degrees Fahrenheit) between the ambient temperature and the desired operating temperature range, the required airflow can be calculated as:
- Airflow (CFM) = 300,000 / (1.08 x 36) = 7,870 CFM
In this scenario, we would need a minimum of 7,870 cubic feet per minute (CFM) of airflow to cool a wall of 10×10 S19j Pro miners.
Laying the pipe
From this point, we need to understand how many feet and what diameter of concrete pipe would be needed in order to cool the closed loop setup.
- Each S19j Pro miner generates approximately 3,000 watts of thermal output.
- The desired operating temperature range is between 60 to 75 degrees Celsius (140 to 167 degrees Fahrenheit).
- The ambient temperature is 25 degrees Celsius (77 degrees Fahrenheit).
- The thermal conductivity of the concrete pipe is approximately 1.7 W/(m*K).
- The specific heat of air is 1.005 kJ/(kg*K).
- The density of air is 1.225 kg/m^3.
- Calculate the total thermal output of the miners in the closed loop setup. For example, if you have 100 S19j Pro miners, the total thermal output would be 300,000 watts (100 x 3,000).
- Calculate the required cooling capacity to maintain the desired operating temperature range. For example, if you want to maintain an operating temperature range of 60 to 75 degrees Celsius (140 to 167 degrees Fahrenheit), you would need to remove heat from the system at a rate of 300,000 watts.
- Calculate the mass flow rate of air required to remove the required cooling capacity. For example, using the specific heat and density of air, the mass flow rate of air would be approximately 308 kg/s.
- Calculate the heat transfer rate from the air to the concrete pipes. This can be calculated using the heat transfer equation:
- Q = UAdT
- Q is the heat transfer rate in watts.
- U is the overall heat transfer coefficient in W/(m^2*K).
- A is the surface area of the concrete pipe in m^2.
- dT is the temperature difference between the air and the concrete pipe in degrees Celsius.
Assuming a temperature difference of 10 degrees Celsius (18 degrees Fahrenheit) and a heat transfer coefficient of 10 W/(m^2K), the heat transfer rate would be approximately 1,700 watts (10 x pi x L x D x dT).
- Calculate the required length of concrete pipe to remove the required heat transfer rate. For example, if the heat transfer rate is 1,700 watts and the thermal conductivity of the concrete pipe is 1.7 W/(mK), the required length of concrete pipe would be approximately 1,000 meters (1,700 / (1.7 x pi x D x dT)).
- Calculate the required diameter of the concrete pipe. This will depend on the flow rate of air and the velocity through the pipe. Assuming a flow velocity of 5 m/s, the required diameter would be approximately 1.1 meters (4 x mass flow rate / (pi x air density x velocity^2)).
Based on these assumptions, you’d need around 1,000 meters of concrete pipe with a diameter of 1.1 meters to cool the air in this closed loop. This does not account for fans to push the air, but I assume the assistance of fans would be necessary and assist in the cooling of the air.
How does this add up?
Would this make sense for a (100) asic farm? Hell no. Here are some VERY rough numbers.
- S19j Pro miners: 100 x $5,000 = $500,000
- Concrete pipes: 1,000 meters x $200/meter = $200,000
- Fans: 10 x $2,000 = $20,000
- Transformers: 10 x $1,000 = $10,000
- Pump: $5,000
- Plumbing and installation labor: $50,000
- Electrical installation labor: $20,000
- Shipping and handling: $30,000
Total estimated cost: $835,000
It’s important to note that these are just estimates, and actual costs may vary depending on several factors such as the supplier, shipping fees, taxes, labor rates, and other local factors. Additionally, ongoing maintenance costs such as electricity and replacement parts should also be considered.
I mean the (100) miners would only yield around $364 per day in profit, but if you could scale this model up to (300) S19j Pro, things suddenly look MUCH more profitable. We’re talking like $19k per day.
This setup would require expertise in earthmoving, a good electrician, and an engineer who could actually run the numbers on the pipes. This setup could allow miners to plant flags with lower infrastructure and operating costs.
- This has WAY fewer moving parts than immersion cooling.
- This has a much lower capex over immersion cooling.
- This has a lower opex cost over immersion.
- Closed-loop setup means clean, cool air for the miners.
Look, I’m not an engineer. ChatGPT did all the math. But I can’t stop thinking about mining, and this might just be viable. If you are reading this, I am actively looking for a sugar daddy to drop some angel investor funds on me so we can prove this and scale it. For everyone else, go try it? Or not. Maybe someone else has tried this, and I will get verbally assaulted for recycling some other pleb’s BRILLIANT idea. Grand hashing.