Scientists from Aalto University and Technical Research Center of Finland explored how future national data-centers will be able to integrate into municipal heating systems and whether they can play a realistic role in carbon emissions reduction.
The plan is to build data-centers for 100 MW and 21 MW in two Finnish cities – Espoo with circa 310 thou residents and Seinajoki with circa 66 thou residents respectively – by 2030. At the same time, according to the calculations made by the researchers, the heat from Espoo facility theoretically could help fully to give up coal, and from Seinajoki – partially to substitute for peat, one of the most carbon-intensive fuels.
To check these forecasts and to assess economic and environmental feasibility of the projects, the scientists developed detailed computer simulations. They took into account hourly electricity tariffs, the cost of fuel, tax regimes and temperature graphs, as well as the heat distribution network equipment profile. This allowed to assess the heat generation dynamics, CO₂ emissions and financial performance under different operation modes of data-centers and utility infrastructure.
The cooling systems operation became one of the key factors. A data-center operator can either use a cooling tower, which is emitting heat into the atmosphere, or to engage a heat pump sending heat into the system. However, the heat pump has very high energy consumption rate, so it is launched only when it is economically feasible. In its turn, the heating system purchases heat only if it cheaper than the in-house generation – bio-fuel boiler houses, gas-fired plants or electric boilers in the hours of low prices for electricity.
It is this divergence of interests that leads to the situation, when heat pumps do not operate on a permanent basis even under tax incentives. The simulation outcomes showed that only 60-70% of heat from the data-center was successfully utilized in Espoo, and in Seinajoki – only about half of all the heat. At the same time, the maximum reduction of CO₂ emissions is achieved only in the scenarios, where the heating system can purchase all the generated heat: in Espoo this reduces the total annual CO₂ emissions from 155 down to 140 kt, and in Seinajoki – from 12 down to 4 kt. However, such operating modes are unstable: during the periods of peak electricity prices the data-center switches to using the cooling tower, but this is exactly when the heating system needs additional heat and is forced to launch its in-house plants, which are more carbon-intensive.
At the same time, in Espoo the investment into heat pump for the data-center may pay back approximately in seven years – an acceptable period for the infrastructure facility. On the contrary, in Seinajoki low purchasing prices for heat make the project a low-return one: the payback period is 25 years and exceeds the equipment service life. As a result, the heating systems are the ones who benefit the most from connecting the data-centers, but the optimal operating mode of such systems does not coincide with the terms, which are the most profitable for the data-center operator to utilize the heat pump.
That is why the researchers concluded; just one tax incentive is not enough for such an ambitious project. To utilize all the potential of using heat, long-term contracts between data-centers and heating companies are required providing for the forecastable sales of heat and compensating for the periods, when operating heat pump is not economically feasible. Only such joint model allows for counting on meaningful and steady reduction of CO₂ emissions
