On 20 December, EGEC commented on the Commission draft Delegated Act that sets out a reporting scheme to rate the sustainability of data centres in the EU. The Delegated Act stems from the recast Energy Efficiency Directive (Directive 2012/27/EU), which introduces a requirement to report on the energy performance and sustainability of data centres.
We welcome the EU’s ‘Fit for 55’ ambition to ensure energy efficiency in all areas of the energy system and in all relevant sectors and, in particular, to establish a common Union rating scheme for data centres.
Every summer several EU cities are already experiencing problems linked to the overload of the electricity grids due to the widespread use of inefficient cooling devices at building and industry (including data centres) levels. This rapid deployment of a new electricity, heating, cooling and hot water need in many buildings requires an integrated approach to ensure the deployment of cooling systems does not impede the European energy efficiency target and actively contributes to the European targets on renewable energy sources.
In this context, geothermal (free and active) cooling technologies represent a solution which is renewable, efficient and cost-competitive and can cool even intense sources of heat1. Data centres are gluttons for energy, requiring an immense amount of power not only to generate the computers, but also to cool them down.
In the case of geothermal energy, passive cooling works by circulating the water and refrigerant mixture (brine) through the pipework buried in the ground (known as ground collectors or ground arrays); the brine is cooled by the lower temperature of the ground before being circulated to a heat exchanger which further reduces the temperature, providing chilled water. The water is then distributed to cooling fan coil units. This system is also called free cooling.
Active cooling, on the contrary, requires the circuits to the evaporator and condenser to be swapped. This allows heat energy to be taken from the circuit which usually provides heating and transfer it into boreholes or water via the ground collectors.
The role of geothermal energy in cooling data centres
Thus, geothermal energy is often the solution chosen to this purpose, as shown in the following examples:
In the new Euronext Data Centre, the cooling system uses ground water extracted from redundant wells and sent to redundant heat exchangers. The piping system serving each data room is made with 4 lines with a quarter of the total Computer Room Air Handler (CRAH) connected to each line. Using groundwater as the main cooling energy source enables Euronext data centre to reduce energy waste. The main advantage is having a constant temperature of the water which, at groundwater level, remains at around 9°C all year round. On completion of the cooling process and with no chemical alteration, the water is returned to the ground, thus excluding any environmental impact. More information here.
Two geothermal doublets (2 boreholes + 2 discharges) ensure that the facilities continue to operate. Free cooling is based on the direct use of the subsoil as a source of coolness, without the need for a heat pump, and provides exceptional energy efficiency, reaching levels of 50/1, i.e. 50 kWh of cold production for 1 kWh of electricity. This performance is unmatched by other energy systems, and means that the environmental impact of the project is kept to a minimum. More information here.
The importance of thermal storage
However, we would also like to highlight that in the Commission draft Delegated Regulation on the first phase of the establishment of a common Union rating scheme for data, the importance of thermal storage is not sufficiently underlined.
Since a data centre’s energy system is a large electricity and cooling consumer, reducing its demand is a key element for improving the data centre’s overall energy efficiency. Integrating underground thermal energy storage (UTES) in a data centre’s cooling system can help cutting the data centre’s energy demand drastically2 with a seasonal thermal storage. Therefore, we suggest the following: