Home server heats water and saves electricity

Short description

A home server can provide more than just computing power; it can also be used as a source of heat for the room, water heating, and even pool heating. Convection and thermal radiation are the two main ways in which a server can provide heat to its surroundings, with larger and more powerful servers being necessary for more significant heat output. Innovative heat exchangers can also be installed to heat water by taking heat from the server, which can be distributed to homes in a “distributed cloud” model, potentially saving energy costs. A startup in the UK is also implementing a similar model to provide free heat through its distributed network of servers to customers, including public pools.

Home server heats water and saves electricity

A home server is an extremely useful thing in the economy. And not only as a computing machine, but also as a source of heat. No wonder cats love to lie next to the computer.

In addition to heating the room, the server can heat water for the house and even heat the pool, although in the latter case a small mainframe will be needed.

▍ Space heating

Temperature regulation in the room is perhaps the most banal option for using a home server. But to begin with, it is worth deciding what it is all about. Of course, a single-board server or mini-PC in a small case is not suitable for heating a room or an apartment. Although they heat up well under load (for example, Raspberry Pi 4

easily heats up to 80 °C

), but their power and body size are too small to heat a significant volume of ambient air.

Raspberry Pi 4 with heatsink and fan

As you know from the school physics course, heat exchange between the PC case and the surrounding air occurs mainly in two ways: convection and radiation (thermal radiation).

Convection is the transfer of heat through the movement of a liquid or gas. The air is heated, passing through the PC case, and is released outside, giving heat to the surrounding environment.

Thermal radiation

– Heat exchange through electromagnetic radiation (EMI). Thermal radiation propagates even without matter in a vacuum. In our case, a warm device (computer) heats the surrounding air, walls, furniture and other objects through the photons of electromagnetic waves in approximately the same way as the Sun heats the surrounding planets.

Passive cooling is usually enough for single-board devices. There is no fan that drives hot air around the room. Since convection is practically absent, thermal radiation from the small surface of the case remains. This is clearly not enough to heat the room, and sometimes even to cool the mini-computer, which can overheat and freeze under heavy load.

We need a more powerful machine, with a large body and good fans that will ensure good movement (ventilation) of warm air around the apartment.

▍ Home PC in server rack

A good option for a powerful thermocouple in an apartment is a productive desktop or

a home server in a 2U case


Mounting a gaming or work PC in a server rack saves space, as all components are placed there more compactly, including UPS, router, etc.

Instructions on how to remount a standard gaming/work PC to a 2U server rack have been published at the link. In this case, the following components were used:

In addition to the standard server rack, the home server fits into an IKEA side table, which is perfectly sized (19 inches between the legs), although your wife or girlfriend may not be too happy with such a room furniture upgrade.

Servers in IKEA LACK tables for $14.99, source

If you watch the Linus Tech Tips channel, you may remember the Fall 2021 project to move a PC system unit from a room to a 4U server cabinet in the basement, with USB extenders up to 200m, etc.

Frame from the video

In such a large volume, there are no problems at all with the placement of components. There are other difficulties: the case is so large that inside it not all cables reach where they need to go.

▍ Free water heating

Another benefit of a home server is free water heating. For example, the British company Heata develops

innovative heat exchangers

, which heat water by taking heat from the server. The so-called “thermal bridges” (thermal bridge) in connection with proprietary servers are installed on water cylinders with a diameter of 450 mm, which act as a boiler. It takes 30 minutes to install the server and the water tank in the client’s apartment.

In general, such servers with water heaters are logically installed in large data centers to provide water to an entire urban area, like a CHP with centralized hot water supply in Eastern Europe. One large data center can heat water for 11,000 homes, like

Facebook* data center in Denmark


* The goal that owns it is banned in Russia as extremist.

But there is another option – to deliver servers to the homes of local residents. And heat the water right on the spot. It turns out such a “distributed cloud” that receives computing tasks from the center and sends back the result via its 4G channel (like distributed computing projects like Folding@Home). In addition, it also heats the client’s water.

So far, this is only a conceptual project (patent


). UK residents can

Submit an application

to participate in the experiment. According to the contract, the company undertakes to provide free water heating to the client for 4.8 kWh per day (minimum 2.5 kWh). A separate energy meter is installed on each cylinder, and the company itself pays for the electricity of its server.

In the future, such technologies may become more common in order to save energy. Perhaps you can make such a heat exchanger yourself for your home, if you have a couple of kilowatt servers to heat a water tank.

▍ Small mainframe for pool heating

A startup implements a similar business model

Deep Green

which hands out small mainframes the size of a washing machine to customers to cool those computers under load (this particular server computes machine learning and AI tasks, which can be understood by the graphics cards in the photo).

This program has already been subscribed to

seven public pools

in the UK. All of them receive compensation from Deep Green for additional electricity consumption.

The computers themselves use liquid cooling with mineral oil, and their power is enough to maintain the temperature of the pool water at 30 ° C for 60% of the time through heat exchangers.

Typically, server cooling accounts for 30 to 50% of a data center’s total energy consumption. And startup Deep Green gets it for free. Their distributed network of servers (edge ​​cloud) covers 1500 public places in the cities of the country. Such a network can be used for CDN or other infrastructure projects. Hosting there is 50% cheaper than AWS.

In turn, customers receive free heat, which is an even more valuable gift for them, since their electricity bills approach €100,000 a year. An average 25m pool costs £7,000 a month to heat. Including due to rising prices, since 2019, 65 swimming pools have closed in Great Britain, writes the BBC. There is an opportunity to seriously save here. A mutually beneficial deal.

By the way, this is an interesting life hack for owners of houses with a swimming pool.

▍ Energy saving

The whole point of heating water/heat carrier and heating premises in winter from the server is to save electricity, and that’s all. Many countries do not have central heating and have to use electric heaters, which is a significant expense: in European countries it is at least 100-150 euros per month in winter (and in summer in hot countries air conditioners consume the same amount).

Therefore, using “free” heat from the server allows you to save. But this does not mean that we should force the CPU and GPU to maximum power to heat the apartment. Quite the opposite. Power consumption of the server should be reduced as much as possible. For example, here is a simple script to save power on a server that automatically puts it to sleep when there are no current tasks.

The bottom line is that the server is idle most of the time anyway, so you can wake it up only when needed (when you need to make a backup or run Plex). Technically, this is implemented through

Wake on LAN

from a single-payer card that runs Home Assistant 24/7.

One simple script reduces server/desktop power consumption in idle mode from 43 (idle) to 4 W (sleep).

In general, some useful life hacks to survive in our difficult times.

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