The cooling system is an essential part of the infrastructure of a Bitcoin mining farm because it controls the temperature of the mining equipment, prevents overheating, and guarantees peak performance. In order to mine Bitcoin, ASIC miners produce a lot of heat, and if the temperature is not controlled, the hardware may be damaged and mining productivity may suffer.
In order to keep the temperature within the mining farm stable, the system typically consists of a combination of air conditioning, ventilation, and fans. The ventilation system aids in circulating the cool air and removing hot air from the room while the air conditioning system lowers the room’s ambient temperature. To help the ASIC miners maintain a consistent temperature, fans have been installed close to the mining machinery.
This post is focused on airflow management-related design aspects of Bitcoin mining farms.
Though they are outside the purview of this post, water cooling and dielectric immersion cooling are also growing in popularity.
Table of Contents
Why is Cooling So Important?
When hashboard temperatures rise too high, ASIC miners are programmed to throttle hashrate and eventually shut down to protect the miner. Furthermore, research from Braiins has demonstrated that better cooling can increase mining efficiency (Joules/Terahash) by as much as 30%. Assuming a constant hashrate, the efficiency is shown to change from 24 J/TH at 20°C to 34J/TH at 75°C. Optimal ventilation also minimizes equipment damage caused by condensation and lowers the need for air filter maintenance.
Also, prolonged high temperature operation will reduce the lifespan of the mining machine.
Bitcoin mining is a competitive business. Running an efficient mining operation through good design is critical for minimizing downtime and repair costs thereby increasing profitability.
How to Design Optimal Airflow for Antminer S19 Mining Rigs
For the management of airflow during Bitcoin mining, we go over best practices and things to think about in this guide.
Sizing Air Exhaust & Intake
The hashing calculations carried out by ASIC miners require electricity. As a result, thermal energy is transferred from the ASIC chips to the heat sinks. This process transforms electrical energy into thermal energy. ASIC miners cool the heat sinks using a combination of air intake and exhaust fans.
Most ASIC miners don’t require expensive air conditioning because they can operate in ambient air that is less than 100 °F. Around 130 to 180 °F is the typical range for the miner’s hot exhaust air. The air intake must be kept from receiving this hot air in a backflow. Having enough exhaust airflow out of the building is essential for preventing overheating of the mining facility. This exhaust airflow volume must match the total amount of exhaust airflow produced by all miners.
To provide enough airflow to the ASIC miners, mining facilities need air intake openings. To keep driving rain or snow from entering the facility, air intake openings are equipped with louvers and/or awnings. To further prevent bugs, dust, pollen, and other foreign objects from entering the facility, the openings must be equipped with screens and filters. The total air intake area can be calculated using the tool on the right.
Direct Evaporative Cooling (DEC), a form of evaporative cooling, is a cooling technology that uses water to cool the air. In DEC, hot air from the mining machinery is passed through a wet filter, which cools the air as the water evaporation lowers the air’s temperature and lowers the mining farm’s temperature.
Why Evaporative Cooling?
The majority of ASIC miners are made to function when the intake air temperature is below 100°F. However, a lot of mining facilities are situated in warmer regions, where summertime temperatures can rise to 120°F. The ASIC miners need to cool this hot ambient air before using it. Using evaporative cooling, intake air can be cooled by 15–30°F.
How It Works
Hot, dry outside air is drawn through water-soaked cooling pads using the principles of evaporation. The heat in the air is absorbed and water evaporates as the air is forced through these pads, lowering the air’s temperature. More cost-effective and energy efficient than compressor-driven mechanical cooling found in air conditioners is cooling intake air using the adiabatic effect of water evaporation. In fact, operating expenses may be as much as 80% lower. By clearing the air of dust and pollen, evaporative cooling offers additional filtration advantages.
Effectiveness and Caveats
The efficiency of evaporative cooling is greatly influenced by the humidity and temperature of the air because the cooling effect is produced by removing heat from the air by evaporating water. The most evaporation occurs in hot, dry air, which is cooled most efficiently by doing so. For coastal climates and during periods of rainy weather with high humidity, evaporative cooling is ineffective. The mining operations in the orange and yellow regions of this map of the US would gain the most from evaporative cooling.
To avoid condensation damage, ASIC miners require an intake air relative humidity of 90%. When using evaporative cooling, it is especially crucial to carefully monitor air humidity levels because it will increase the relative humidity of intake air. Even in hot, dry areas, evaporative cooling should be reduced in cold and rainy weather.
Separating Hot & Cold Air
The best intake air temperature for ASIC miners is cold, so it’s crucial to avoid having hot exhaust air recirculate into the miner’s intake. Air barriers made of insulation materials can be used to stop this backflow. The term “hot aisle containment” refers to this method, which is frequently used in place of foam board insulation, which is readily available in home improvement stores. The R-value and thickness of an insulation material are not particularly significant because convection, not conduction, is the main mechanism of heat transfer with air mixing.
Moisture Control & Hot Air Recirculation
In mining facilities, high intake air humidity can lead to issues. Snow-covered moisture is readily drawn in by air, especially during winter storms. The air’s moisture content can condense on cool surfaces at high relative humidity levels. As the air temperature drops or the pressure changes, condensation can also happen. Because ASIC miners operate at high temperatures, one might assume that they are immune to condensation; however, at higher relative humidity levels, changes in air pressure inside a miner can lead to condensation. The risk of condensation damage is also increased for any miners who are left idle due to a malfunction. Power distribution units, power supplies, control boards, switchgear, and other equipment are all susceptible to damage from high moisture levels. Rust on air intake fan grills is one of the most common early indicators of moisture issues inside a mining facility.
It is typically advised by ASIC miner manufacturers to run bitcoin mining operations at relative humidity levels under 90%. Since relative humidity depends on air temperature, heating incoming air by combining it with hot exhaust air is one of the simplest ways to lower its relative humidity. For instance, intake air at 60°F and 90% relative humidity will decrease to 75% relative humidity when heated by just 5°F, making it safe for use in mining. Hot air recirculation is the name of this process.
In order to allow for a small amount of hot air to return to the cold side, gaps can be left in the air separation barrier. However, this method warms the incoming air and decreases mining productivity (Joules/Terahash). To avoid condensation and a significant temperature increase in the cold intake air, it is crucial to precisely control the backflow. An automated hot air recirculation system can also be installed, and it can regulate the amount of air that backflows based on the temperature and humidity of the intake air.
Facility Layout & Engineering Design
Wall Exhaust Vents
A wind tunnel’s basic airflow design is similar to that of a mining farm. Cool air enters from one side and exits on the other side after passing through a wall of miners. For the building to avoid becoming overheated, exhaust fans are required. Without the need for fans on the air intake side, the negative pressure produced by ASIC miners and exhaust fans is sufficient to draw cool air in. In small and medium-sized (2 MW) mining operations and shipping container designs, this airflow design is fairly typical.
Roof Exhaust Vents
Larger mining facilities (>5 MW) now frequently feature roof-vented designs, which are steadily growing in popularity. Exhaust fans mounted on the roof move hot air that rises naturally out of the structure. With air intake on both sides, this kind of design enables a higher miner density inside the structure. Roof-vented building designs require more money to construct and maintain, though.
Direct Drive Vs Belt Drive Exhaust Fans
There are two main types of fans: direct drive and belt drive, and each has advantages and disadvantages. In order to make a more informed decision, it is important to discuss both the benefits and drawbacks of each option.
Since there are no sheaves, belts, or bearings to maintain, direct drive fans typically require less upkeep.
For propeller fan sizes greater than 36 Prime, belt drive fans are frequently used. Typically, larger belt-driven fans are more economical. Through the use of a drive package to change fan speed as necessary, they also provide greater performance flexibility.
Although both of these kinds are employed in bitcoin mining operations, direct drive fans are more common because of their easier design and lessened maintenance requirements.
The mining facility may experience moisture issues as a result of air intake openings attracting rain and snow. Louvers by themselves are insufficient for rain protection. Intake louvers and long roof overhangs or awnings are typically used in new facility designs in addition to them to provide rain and snow protection.
High intake air velocity is caused by a small air intake area. As a result, the airflow becomes turbulent, more precipitation is attracted, and frequent filter cleaning becomes necessary. Increasing the air intake area can often solve many of these problems. There are numerous methods for accomplishing this. Filters with thick pleats have a higher free area ratio, more intake surface area, and more.
Multiple parallel rows of awnings mounted on the side wall of the mining facility are one increasingly common method of air intake. The bottom of the awnings has intake openings for filtered air. This awning-based intake design can offer a significantly higher intake surface area when compared to a wall intake design. Additionally, this design is much better at removing dust and pollen because the intake openings are angled downward.
The focus of conventional air handling designs is on discharging hot exhaust air because they assume that it is an inconvenience. Bitcoin miners are currently coming up with inventive ways to recover exhaust heat in their quest to increase profitability and sustainability. A growing number of uses for this heat include drying wood, dehydrating produce, heating water, aquaculture, etc. For miners, additional revenue sources from heat recovery applications can significantly reduce operating expenses. Heat recovery is not a feature of conventional bitcoin mining facilities, so technological advancements in this area will continue to influence how bitcoin mining facilities are engineered and designed.
Filtration keeps the environment in a bitcoin mining farm clean and safe for workers. It avoids the buildup of dust and other particles that could clog mining machinery and decrease productivity.
Mechanical filtration is the most common type of filtration used in bitcoin mining. To remove particles from the air, mechanical filtration uses physical barriers like air filters, screens, or meshes. In Bitcoin mining operations, mechanical filters are frequently employed to efficiently filter out dust and other large airborne particles. Depending on the needs and conditions of the mining farm, various filtration techniques, such as electrostatic filtration, UV-C filtration, activated carbon filtration, and HEPA filtration, may also be used. The most widely used technique for mining bitcoins, however, is mechanical filtration because it is both efficient and effective.
In this blog, we covered various aspects of airflow management, including sizing air exhaust and intake, utilizing evaporative cooling techniques, separating hot and cold air streams, moisture control, facility layout, intake design, heat recovery, and filtration. By implementing these best practices, Bitcoin mining operators can design and maintain an optimal cooling system, leading to enhanced efficiency, improved mining performance, and reduced equipment downtime.