In the last years the total energy demand of data centres has experienced a dramatic increase which is expected to continue. This is why data centres industry and researchers are working on implementing energy efficiency measures and integrating renewable energy to overcome energy dependence and to reduce operational costs and CO2 emissions. The cooling system of these unique infrastructures can account for 40% of the total energy consumption. To reduce the energy consumption, free cooling strategies are used more and more, but so far there has been little research about the potential of thermal energy storage (TES) solutions to match energy demand and energy availability. Hence, this work presents a dynamic energy model able to study the implementation of different energy efficiency strategies and see its effects on the operational conditions, power consumption and ecological footprint. Operational data from a real 125 kW IT data centre located in Barcelona has been used to validate the energy model.