The interest in the carbon footprint of Data Centres (DCs) has become more urgent with the rapid increase in Cloud computing, High-Powered Computing, and the vast growth in Internet use, and of DCs as key enablers of this paradigm. However, whereas energy efficiency is necessary to reduce ecological impact of DCs, it is not enough. In addition, the carbon emissions of DCs are greatly influenced by the energy sources used, the operation of the DC, the connection to energy infrastructures in our cities and integration of Renewable Energy Sources (RES). Planners, managers, investors, owners and designers of DCs lack the necessary tools capable of evaluating the environmental performance and the share of RES in the emerging concept of Net Zero Energy DCs.The main objective of the RenewIT is to develop a simulation tool to evaluate the energy performance of different technical solution integrating RES in several European climate regions. The public RenewIT tool will be implemented in a user-friendly web interface helping actors from both the energy and IT sectors to reduce the carbon footprint of planned DCs in the horizon of 2030. The tool is based on selected meta-models extracted from advanced dynamic simulation models of challenging energy concepts for renewable energy supply of DCs.A set of challenging energy concepts will be developed in the framework of the project under an holistic approach integrating the following technical solutions: management of the IT load following "green" objectives, low-energy air-conditioning systems, solar cooling, interaction with district heating and cooling networks, re-use of heat, optimal use of heat and cold storage, and integration in smart grids. The technical systems emerging from the energy concepts are modelled in dynamic simulation tools creating a family of new components which will be integrated in the Green DC library of components as an exploitable output of the project. Harmonised metrics able to rank the energy performance of DCs will be developed and implemented in the software tools as a result of co-ordinated work with relevant standardisation organisations, industry bodies, and other European projects. In addition, these harmonised metrics will be part of a high-quality monitoring system to monitor DCs integrating renewables.A validation process will be developed, in close collaboration with four DCs in Southern Europe and four DCs in Northern Europe, which will exchange continuous feedback with the technical developers throughout the project. The validation process will be based on built case studies for live DCs as the means of testing the robustness and the end-user applicability both of the developed technical energy concepts and of the simulation software tools.The project outputs will be widely disseminated throughout the project lifetime, through scientific and industry publications, web site and social media, and attendance at relevant conferences and industry forums.