Residential heating associated with mining: does it really pay off? Asic cooling methods, economic considerations, and environmental impact.
How can Bitcoin mining heat?
Is it possible to use an Asic, that is, a bitcoin miner, to heat one’s home?
To give a thoughtful answer, we will do a technical and economic analysis of the question, looking at the effects on environmental impact. Commonly referred to as Asic, each of these small processors actually contains as many as hundreds of individual Asics in series, i.e., 1×1 cm chips capable of doing only one task, but doing it very well and very fast: applying the SHA-256 algorithm that is used for bitcoin mining.
This type of chip produces a lot of heat relative to its surface area (as much as 15watts) when compared to the hardware used in traditional datacenters. An Asic miner the size of an air-cooled shoebox can get as much as 3 kWh of electrical energy into heat energy constantly, while a classic datacenter has to fill a few meters of shelves to turn the same amount of energy into heat. The parameter to consider in reasoning about possible benefits is not “how much total heat” is produced, but how concentrated it is relative to the volume from which it is developed. In this case, a lot.
The problems of home air mining
Having in hand what we might for all intents and purposes consider an electric “heater” with very powerful fans, the answer to the initial question from a purely intuitive point of view might seem positive.
Using a classic air Asic, however, implies several compromises: leaving aside for a moment such important aspects as economic and environmental impact, it is not for everyone to be able to run an Asic in the home with fans whistling at 90 decibels h24, with little residual power available for appliances. All this, assuming that hot air can effectively reach all points in the house.
Some miners invest in technical modifications that allow them to dampen the noise of air systems, so they can heat a garage or shed with reduced noise pollution. These are, however, practices reserved for those with a passion for DIY. For those who want to try their hand at it, many guides can be found on the Web.
Specially designed (even in design) air solutions are also becoming popular for heating the living room quite quietly by mining bitcoin. 21energy is an example of an Asic-air heater manufacturer already on the market. However, great attention must be paid to cost management, addressed later in the article.
Environmental impact of home air mining
From the point of view of the polluting effect, the comparison with the impact of natural gas holds up laboriously. Burning, gas (methane for the most part) gives water (steam) and carbon dioxide (CO2) as combustion products. Combustion from methane thus contributes yes to air pollution, but without emissions of particulate matter (pm 2.5-pm10).
The electricity that would be used by the miner can come from a variety of more or less polluting sources. In general, if you already have a system that generates sufficient clean energy (photovoltaic, wind, geothermal, hydroelectric) you might consider free and green heating using an Asic. In all other cases, which are the majority, an Asic would not lower the environmental impact of home heating.
For example, in the case of having a properly sized (very large) photovoltaic system and significant and expensive storage batteries to compensate for the hours of no light, it would become possible to power an Asic with clean energy for heat, but we would always have to take into account the environmental impact due to the type of batteries used (it can take 30 to 50 kWh to store each day for a single Asic, for a total consumption of more than 70 kWh daily) and the fact that those 3 kWh thermal could hardly meet the heating needs of a whole typical family home in winter at European latitudes.
The economic aspect
One of the common denominators is the cost of hardware: the Asic has relatively high prices and that normally accounts for the big chunk of the expense. It is critical to first understand that the daily profitability of a miner is not constant over time, but can vary widely over months, both negatively and positively. Taking into consideration a time frame of a few years, which is the average life of a properly managed and cooled miner, the profitability of any Asic drops steadily by very small percentage values every day. There are many reasons for this, from the increase in the global hashrate (and consequent increase in the difficulty of computation) to the obsolescence of small chips that perform less well than the new models coming out on the market.
Starting a home bitcoin mining facility involves purchasing hardware worth at least a few thousand dollars and obtaining very small fractions of bitcoin on a daily basis. It is likely to expect a window of a couple of years to return on the investment.
The use of air-cooled Asic has also long been a case study for heating barns and agricultural greenhouses, such as the Dutch Bitcoinbloem. The latter chose to replace natural gas heating with solar-powered Asic arrays supplied by the grid, successfully maintaining the optimal temperature of a large tulip crop.
Innovative cooling techniques and heat-sharing possibilities
Recent chip evolutions, now produced with 5-nanometer technologies that allow work/hashrate ratios of less than 20Joule/Terahash, enable more reward for the same energy consumed than previous generations, thus making designs more economically sustainable.
The use of technical evolutions in cooling and repurposing (energy recoveries) can allow mining to be combined with residential heating, i.e., not exactly “home” heating (one bitcoiner in his home) but referring to groups of houses that share hot water (an activity we can call “heat sharing”) provided by mining units (e.g., containers) especially near waterways, or public or private facilities that need hot water.
A good example is the Bathouse in Brooklin (NY), a Bitcoin-heated spa through oil immersion cooling.
How did they do it?
The point is to understand how well we can manage to transfer the heat we produce. Using air as a fluid to cool the chips is still the technique the most common in some large mining farms, which, by using adiabatic panel cooling systems (which take heat away from the air by evaporating small amounts of water), manage to keep the miners on successfully in very hot and dry climates, such as in Texas.
However, this type of cooling remains less efficient than others developed in recent years: hydrocooling and oil immersion cooling have significantly elevated the effectiveness of heat transfer and transport. It is readily understood that water cools better than air: not for nothing if we need to cool something quickly we put it under running water rather than in front of a fan.
Hydrocooling
Hydrocooling, which involves cooling by running water through metal heatsinks directly in contact with the chips inside the miner, can heat the water and cool the chips optimally. In this way, however, the liquid becomes part of the internal cooling system and requires specific designs for each miner model. In addition, not all electronic parts are protected, only the chips, and at the time of a hardware upgrade one is forced to replace everything.
Dielectric Oil Immersion
The most innovative and efficient cooling system used to heat water through mining is dielectric oil immersion, which is also my field of research. Besides being adaptable to virtually any type of Asic, all the heat is collected down to the last watt. The oil yields the energy to water in water/oil heat exchangers in a closed, continuous loop with the immersion tanks.
The heated water can be piped to any type of residential application with temperatures as high as 60°, and this is precisely the system used to heat the spa mentioned above.
This type of heating application can replace all those that use fossil fuel sources; it can also be powered by natural gas or biogas, thus working together with other technologies to obtain clean energy and/or hot water. Incentives to install renewable energy systems could help introduce these seemingly expensive but very efficient technologies. In addition, since the infrastructure in some areas is not suitable for transporting all the energy produced, problems of overproduction may arise. In that case, mining being an activity that uses energy on site, “working” for Bitcon’s timechain can facilitate the feasibility of many projects.
Is it possible to heat using Bitcoin mining while reducing environmental impact?
Using bitcoin mining also for heating in some cases is cost-effective at the residential level with heat sharing. Generally it is in the primary sector and sometimes in industry, particularly when you have the ability to pay little for energy or produce it yourself, choosing to mine and heat the area at the same time.
This practice could also be seen as a way to decrease the environmental impact of human activities in the case of using a renewable source to power Asic, as in the case of the Dutch greenhouse. The effect would be even better should biogas or gas flaring be used: methane is responsible for 20 percent of the greenhouse effect, much less than the CO2 that also results from its combustion, but over the 100-year time horizon this gas has a Global Warming Potential (GWP) 28 times greater than carbon dioxide, as reported in the IPPC’s fifth assessment report called AR5.
The Global Methane Pledge by the Italian Institute for Environmental Protection and Research, which with the Po Valley can study one of the areas with the worst air quality in Europe, further confirmed that methane has a far shorter residence time in the atmosphere than carbon dioxide (10/15 years vs. thousands), but if present for 20 years it has an 84 times more significant impact.
Moreover, the latest guidance from the recent AR6 Climate Change 2023 confirms the need in the immediate term to prioritize the reduction of methane gas emissions:
4.2 Benefits of Strengthening Near-Term Action.
As methane has a short lifetime but is a potent GHG, strong, rapid and sustained reductions in methane emissions can limit near-term warming and improve air quality by reducing global surface ozone (high confidence).
Bitcoin mining, if applied in a smart way, could make a contribution.
Accomplice also to the gradual adoption of bitcoin, installations of this kind will become increasingly common. Self-sustained home heating with bitcoin mining is possible or smart in only a few cases, and only the future will tell whether these residential forms of “heat sharing” and repurposing in the farming and ranching sector can really help balance environmentally harmful emissions.
As of today, Bitcoin is certainly laying its cards on the table.
