The Marilyn green datacenter

Datacenters consume a lot of energy. Over and above computer servers, whose consumption can be optimised, the generation of heat caused by servers is significant. Current IT centres consume energy to produce cooling in order to limit room temperature.

The PUE (power usage effectiveness) ratio is used to determine the productivity of datacenters. The PUE is defined as: the global consumption of the site / consumption of IT equipment over 1 year of operation. Several actions are undertaken by market actors in order to reduce the PUE. In the Marilyn project, an innovative and efficient approach is proposed to provide solutions.

Marilyn is the first high-density environmentally friendly datacenter in France and an emblematic site of the Cité Descartes, the sustainable development centre of Grand Paris.

Optimised electrical consumption

In the average site in France today, the PUE is 2.5, according to recent studies. New projects today target ratios of 1.8, or even 1.6. A recent study undertaken in the USA demonstrates disparities in this ratio of between 1.34 and 3 for functioning datacentres.

The target electricity consumption set for the Marilyn datacenter is a target PUE (productivity) of 1.3. Therefore, the Marilyn concept is aiming for a very high energy output.

Several technological choices exist to reduce electricity consumption:

  • Innovative “all air” architectural design to cool a high-density datacentre without producing chilled water
  • Use of ambient air (“free-cooling”) 80% of the year
  • Recycling heat generated by the machines used to heat offices
  • Invoicing electricity consumption of each source for each client

Environmentally friendly choices on all levels

To reduce the datacentre’s overall carbon footprint, alternative solutions have been put in place:

  • Refusal to use (lead) batteries for flywheel inverters
  • Refusal to use copper for a fibre optic cabling on 100% of the site
  • Implementing recycling of materials

Aeration-exterieure Baies-datacenter

The various operating methods of Marilyn free cooling

In Marne-la-Vallée, as in many areas of France, the climate is favourable to free-cooling using ambient air. Minimum temperatures reach below 20 °C every day, and reach higher than 32 °C only 2% of the time.

Humidity is moderate, which is useful for this cooling method, as the acceptable levels for IT servers require a certain degree of humidity. The CELESTE Marilyn datacenter operates using automatic registers according to different modes, which are determined by the weather.

The 3 cooling modes

  1. Cold mode
    If the temperature is lower than 23 °C, which equates to roughly 80% of the time, cool air is filtered and injected directly into the building without air conditioning.
  2. Hot mode
    If the temperature is higher than 35 °C, or if humidity is above a set value, or if smoke is detected in the external air, the building goes into total recycling mode: the air discharged by the servers is air conditioned and reinjected. This mode is used 5% of the year.
  3. Intermediate mode
    In all other cases, external air is used after an initial cooling.