The project Hybridation of geothermal energy with flow batteries for the air conditioning of tertiary buildings of zero energy, hereinafter GeoBATT, aims to develop a new energy technology that supplies the systems of air conditioning of buildings based on the hybridisation of the energy use of the subsoil (low enthalpy geothermal energy) with the storage of electric energy by means of flow batteries, in order to obtain buildings with almost zero energy consumption, with application in both developed and developing countries. This objective responds to the Challenge in Safe, Sustainable and Clean Energy, since it will reduce the consumption of buildings by 80 %, in addition to guaranteeing the security of supply to critical facilities without the need for generators. This is fundamental in developing countries, where supply assurance is a pressing problem. The increasing consumption of energy by the human being is causing changes at the planetary level whose consequences are alarming and evident. The construction sector is responsible for 40 % of energy consumption, so the European Commission is promoting measures and policies that lead to the development of new technologies to increase the efficiency of buildings up to near-zero consumption. Currently there is no solution that alone can cover the total consumption of buildings, and the integration of different technologies is necessary. In this context, SACYR Industrial, PVH Energy Storage, UPM (Dpt. of Fluid Mechanics and Aerospace Propulsion), UC3M (Fluid Mechanics Group) and IMDEA Energy, have decided to join efforts to develop a technology that hybridises geothermal air conditioning with energy storage in flow batteries with the following benefits: —The geothermal use of the land will allow to achieve energy efficiencies far superior to those achieved with other energy sources; and it will reduce the energy supply to a single type, electricity, simplifying the energy management of the building. —The use of flow batteries will allow disconnecting the electricity supply from its subsequent consumption, ensuring uninterrupted operation of the building. In addition, it will allow to effectively take advantage of energy from renewable sources, such as solar and wind, given its intermittent nature. In addition, the synergy between both technologies will reduce investment and operation costs, revalue the thermal energy that would otherwise be lost in the flow battery and optimise the operation of the same. To achieve this objective, it will be necessary to develop advanced models of the geothermal air conditioning system, integrating non-linear parameters (COP or variable flow rate); a zero-dimensional model of the technical room; and flow and mixing models for flow batteries and electrolyte deposits. These models will allow to optimise both technologies, which will crystallise in the development of a prototype and the implementation of a pilot demonstrator on a real scale. In parallel, possible deployment scenarios will be analysed and an economic study will be carried out, which will be validated with pilot data. The scope of this project is both national and international given the growth of the construction industry in regions such as Asia, the Middle East or Latin America. The internationalisation capacity of this technology is guaranteed both by the growing interest in an increase in the energy efficiency of buildings, as well as by the strong worldwide presence of the SACYR and PVH group, as well as the contacts of the UPM, UC3M and IMDEA Energy in scientific and academic circles.