Can you use crypto-mining energy to heat your home?

July 31, 2018
Chris Wheal

So, you’re determined to build a high-powered mining rig. You’ve done the calculations, and you’re convinced that you’re able to recover the cost of the kit and the electricity in an acceptable period. How about recovering it a little sooner? By turning your rig into a mini-heater, could you save on your heating bill?

This article looks at how to build a mining rig that can heat at least part of your home. You won’t be mining bitcoin if you’re building your own rig, of course, because all the smart money there is in ASIC miners, which takes some serious industrial-strength buying power.

Instead, we’ll concentrate on graphical processing units (GPUs), which are good for memory-hard algorithms such as Litecoin’s scrypt, or (for the time being) Ethereum’s Ethash.

These GPUs typically use consume a lot of power when running full bore on gaming graphics or, in our case, proof of work algorithms. Most of the power they consume is turned into heat, which gets captured by fans and blown out of the side of the box. Instead, a hobby PC builder could create a unit that directs heat to warm a room.

Using computers to provide heat

We know that computers can heat rooms, and in some cases, water, because companies have done it before. Some firms do it on a large scale. As early as 2008, IBM was taking the water from its data centre in Switzerland and using it to heat the local swimming pool.

More recently, some companies have taken this concept down to the individual home level, doing away with the datacenter altogether. Nerdalize puts its ‘cloud boxes’ directly in peoples’ homes and uses them to crunch cloud-based analytics jobs for its clients. The boxes generate enough heat to warm water in the home to 55 degrees centigrade.

Nerdalize pays for the cost of that electricity, effectively giving the homeowner free heat. It eliminates the cost of leasing or building data centre space and passes some of that saving on to its customers, improving its competitiveness.

Graphcal Processing Unit.

A GPU card generates lots of extra heat

The company even uses its management software to distribute the computing load around its customer base according to their heating needs. If you’re cold, then it can shunt more computing jobs to your house. Neat.

Radiative heat

We’re not doing anything that grandiose, but the principle is the same. Let’s start by simply warming a single room using radiative heat.

When you’re cooling a desktop PC, you have two main options. The first is a heat sink – a big, square unit with blades that sits atop the processing units (the chips) to draw up and dispel the heat. Those are the less efficient option, especially when you’re dealing with high-powered equipment like mining rigs.

The second option is water cooling. This takes cold water directly to the processing unit, running it through a water block attached to the chip to extract the component’s heat. It then typically goes to a radiator with a fan built in. The heated water will pass through the radiator, which will already expend some of its heat. The air from the fan will do the rest, pushing the heat out into the room.

Water cooling systems

Ideally, you’ll want a closed-loop water cooling for this, which keeps the water inside a sealed system. The alternative, an open loop system, pipes the water in from a reservoir and allows you to build complex systems of pipes and coolers that pass around several units at once.

These would be effective, but they’re more expensive and have a big downside, in that you must replace the water every few months to avoid external pollutants bunging up the system.

The size of your room and the size of your rig should correspond. A 1000-watt electrical heat would work well in a 125 square foot room, whereas a 1500-watt rig would adequately heat a 175 square foot room, but a lot depends on how efficient you are at getting heat out of the rig.

This experiment used a 940 watt mining rig to heat a ‘bedroom-sized’ room by 10oC. But what if you’d like to create a water heater instead?

Heating water

You might do this for two reasons. Firstly, to heat your room with a water radiator, or secondly (and more ambitiously), to heat water for your plumbing system. Ethereum-powered showers? Yes please.

We know that both these concepts are doable, because we’ve seen them. PC builder enthusiast site Linus’ Tech Tips tried the former approach, taking an old radiator and pumping water directly from it to an open-loop cooling system on the PC. It worked – kind of.

The radiator got nice and hot, but the combination of a dirty old radiator and an open-loop system quickly introduced pollutants that reduced the cooling efficiency, causing thermal throttling in the PC. That makes the GPUs stop working as hard because they’re getting too hot, which is the opposite of what you want in a mining rig.

Heat exchanger

One way to solve this problem would be to use a water-to-water heat exchanger. The exchanger contains two water streams that never meet. One loops between the heat exchanger and the radiator, while the other loops between the heat exchanger and the PC’s cooling system.

In the heat exchanger, each loop runs in channels past the other. These channels are separated by a wall that stops contaminants from crossing between the two water loops but does allow for the exchange of heat.

A heat exchanger would enable your mining rig to heat up a nice-looking old radiator while still keeping your cooling loop clean, but it would still take maintenance. You’d have to replace the water every few months.

Heating your water tank water would work on the same principle, but you’d want around 1000-1500 watts of power flowing through your rig.

Regulation concerns

Beware the regulations in your area if building a water tank heating system of your own, though. In some areas, for example, you’d need to use a double-walled heat exchanger to reduce the risk of contamination because your hot water tank water is still seen as potable water.

In any case, you’d want to work with a qualified plumber before messing with your plumbing system, lest you make a mistake and either start a fire with a leak or overload your pipes. That kind of project is not for the faint-hearted.

Heating your room by a few degrees would be a satisfying way to pay a portion of your heating bill while also generating extra income, but the devil is in the detail.

Cost benefit analysis

In homes using gas heating, where gas costs far less than electricity, the benefits would be less obvious. It’s unlikely that you’d ever recover the cost of the electricity from your heating bill, but if you’re going to mine anyway, it’s a neat way to make things more efficient while creating a fun talking point for fellow nerds.

Bear two things in mind, though. Firstly, depending on your climate you may find your room getting too hot for comfort in the summer. Secondly, while the options for compute-intensive proof-of-work mining will probably always be there, they’re shrinking.

Ethereum will move to proof of work at some stage, for example. But if you’re prepared for these eventualities, this would make a fun summer project.

Post written by Chris Wheal
Chris Wheal is editor of OpenLedger's news and features service. An award-wining business journalists himself, he runs a team of freelance journalists from across the UK and north America.

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