As the use of data increases, the consumption of electricity in data centres also grows, with estimates from the International Energy Agency suggesting that digital infrastructure accounts for around one per cent of global electricity demand at present. At the same time, data centres produce a significant amount of heat, driven by the vast array of computing equipment needed to process and store data.
An excess amount of heat, however, presents a number of problems for a data centre facility. Computing equipment that overheats could cause downtime, loss of data, or even a complete system meltdown – all negative effects in an industry that thrives on reliability.
Usually, data centres deploy an array of cooling methods to regulate temperatures within their facility. In Finland, however, telecommunications company Telia has partnered with an energy company, Helen, to connect Telia’s data centre in Pitäjänmäki to the district heating network. Using a heat pump, the heat collected from the data centre will be used to heat homes in Helsinki, at a rate of 1.3 times the heat that it consumes as electricity.
The district heating system in Helsinki is undergoing a transition from centralised heat production towards a distributed system where customers can act as consumers and producers. Data centres are excellent sources of heat as they produce it evenly throughout the year, and district heating networks are a good platform for new carbon-neutral solutions such as waste heat recycling.
In a statement about the project, Eija Pitkänen, Telia Finland Oyj’s vice president of corporate responsibility, said: “The central location of the data centre is ideal for delivering waste heat into the district heating network for the needs of a growing Helsinki. The carbon-neutral district heat produced by the data centre in Helsinki can be used for heating up to 20,000 dwellings, replacing the use of fossil fuels as an energy source. This also supports Telia’s ambitious environmental targets, and we are striving for zero emissions by 2030 throughout our value chain, from subcontractors to customers. We also aim to reduce our waste to zero within a circular economy.”
Infrastructure and cost challenges
Despite how simple it sounds, the practicalities in terms of infrastructure and cost are not straightforward. Joni Solakuja, production manager for cooling and automation at Telia Finland, says that, in Finland, the average PUE is already low thanks to a climate that allows for relatively long free cooling periods. Waste heat, on the other hand, needs to be processed to meet the market demand, which usually means using compressors to increase the temperature by roughly 50 degrees centigrade (°C).
The multi-lift heat pump process, continues Solakuja, is technically demanding and absorbs more electricity than what is saved with free cooling, meaning that implementing a heat recovery system increases the total energy consumption of the data centre.
“Chillers and heat pumps are technically very close relatives,” comments Solakuja. “One is optimised to produce chilled water with an extremely stable flow and temperature, while the other is optimised to produce a maximum amount of heat energy, sometimes sacrificing stability in the process.
“However, in the case of district heating, the required temperature lift is so high that it cannot be acquired with the same technical solutions. Typical data centre cooling systems deal with temperature drops of between ten and 15°C. This means that the cooling system is simpler, and requires only one temperature drop, whereas the heat recovery system most likely requires two temperature lifts, leading to more complex processes.”
As a result of this disparity, heat recovery systems are likely to cost between 1.5 and two times more than a comprehensive cooling system. And, in any case, the district heating network might not always be able to receive all of the heat that a data centre may have available, meaning that a cooling system is a necessity in any facility, even if used as a backup.
Waste heat recycling in more temperate climates
While that may be the situation in a country such as Finland, where the climate facilitates long periods of free cooling, waste heat recycling may be a more attractive proposition in other countries which do not have access to such readily-available free cooling.
Erik Barentsen, senior policy officer at the Dutch Data Center Association, says that, from a data centre perspective, it makes sense to provide residual heat to off-takers, provided the facility has sufficient capacity in terms of the amount of energy that is required. This is because, assuming a reasonable return on the initial capital expenditure, it is possible to reduce the operational cost of electricity and water usage while the data centre is participating in district heating. A cooling system, Barentsen argues, would not need to be used simultaneously, and would only be in use should the demand for heat reduce, or there is a system failure.
However, another challenge that Barentsen points out is that, for the district heating operator, the business case only makes sense if they have sufficient off-takers, and they are reluctant to foot the costs of the initial infrastructure project without guarantees of return on their investment.
“In the Netherlands, we have a plan to subsidise the investment and provide a buffer to soak up the initial losses of such a system,” explains Barentsen. New legislation has been promised to tackle funding for new heating infrastructure, including district heating, but that has been delayed in the Dutch parliament, pending discussion on how such legislation should be implemented.
“Everyone knows we need to do something, but we are also paralysed by the fact that this law will soon be passed and we do not know how that will affect heating infrastructure projects, so we are just waiting around to see what the new laws will look like,” says Barentsen. “We need clarity, and we need to speed up the process.”
Of course, there are plenty of other considerations for operators looking to participate in district heating schemes, including the impact on their environmental footprint. An increase in electricity consumption might add very little to a data centre’s Scope 3 emissions if the grid is supplied by a wealth of renewable energy sources, but will have a much bigger impact in countries with a high supply of fossil fuels.
Nevertheless, district heating is considered an integral part of the drive to decarbonise the heating sector by the 2050 deadline, as set out by the Paris Agreement. With digital infrastructure proliferating at a rapid pace, it could play a crucial role in making a zero-carbon heating industry a reality.