Background A complete transformation of all sectors of the economy is required to mitigate climate change and to limit global warming to the internationally agreed target of 2ºC above pre-industrial levels by 2050. According to the European Environment Agency, the energy sector is the largest single source of CO2 emissions, generating 31% of all EU CO2 emissions. The transition to a low-carbon economy necessarily involves a significant transformation of the energy sector, in particular the electricity system. As part of this transformation, there will be increased generation of electricity from renewable sources, which can be intermittent. The intermittent nature of major renewable technologies such as wind and solar energy is a barrier that jeopardises the achievement of Europe´s objectives of renewable penetration in the medium and long terms. One of the main challenges for renewable energy in Europe is not generation but grid integration and adaptability to fluctuating power demand. Different technical solutions such as smart grids, international grid connections and energy storage facilities play an essential role in enabling the development of a low-carbon electricity system. Energy storage systems in particular could play a key role because they could transform variable and intermittent renewable energy sources into flexible and reliable sources that are able to adjust their power output to match the requirements of the grid. Objectives LIFE ZAESS will demonstrate an innovative zinc-air energy storage technology that can address the needs of intermittent renewable energy. This innovative zinc/air flow battery combines the advantages of metal-air batteries and flow batteries. It offers: increased rechargeability and life span; less energy lost in the storage process; increased total system capacity, making it suitable for grid-scale renewable energy storage; and reduced production costs, because expensive ion-exchange membranes are unnecessary. In particular, the project will: Build and test a demonstration energy storage pilot plant based on novel rechargeable zinc-air battery technology, and assess its scalability; Assess the environmental impact associated to the construction and operation of this type of energy storage facility; and Propose a legal and regulatory framework for the deployment of large-scale energy storage facilities in order to overcome those barriers for future renewable energy market penetration. Expected results: The most important result of the project will be the technical and economic validation of zinc-air technology for grid-scale renewable energy storage. The expected concrete results are: From a technical point of view the demonstration will prove the scalability of the technology from laboratory scale to the range of one to four kilowatt hours; The pilot plant round-trip energy efficiency is expected to be between 60-70%; it is planned to operate the plant for between 1 000 and 2 000 cycles; From an economic point of view, a conceptual engineering study for a MW (megawatt) scale plant is expected to yield capital costs between 2 000 and 3 000 €/kilowatt. This is a commonly accepted cost target for grid-scale energy storage systems in the short to medium term; and A full environmental impact assessment covering the entire life cycle of MW-scale energy storage plants based on zinc-air technology, including detailed environmental and carbon footprint analyses.