Redox Flow Batteries (RFB) are a key enabling technology for the energy transition. Mass market introduction of RFB’s has been hampered by various factors – material scarcity and cost (e.g. vanadium-based RBF), limited catalyst lifetime, membrane costs, system complexity and safety issues. The development of an economically viable, environmentally benign and sustainable redox-flow battery (RFB) storage systems is therefore eagerly awaited. The MEmbraneless LOw cost high DensitY RFB (MELODY) project will develop a sustainable RFB technology that is able to reduce the costs of electricity storage to an absolute minimum, even below the 0.05 €/kWh/cycle by 2030 as set out in the SET plan. MELODY employs a unique triple cost reduction strategy on the conventional RFB concept while tackling all major technical issues in an integrated manner. The three key elements are 1) A membraneless flow battery concept 2) the choice for hydrogen and bromine 3) Simplified system design. This approach will results in the realization and operation technology for a practical membraneless H2-Br2 redox flow battery at industrially relevant scale (based on dedicated Cell, Stack and Balance of Plant development and piloting). Hereby MELODY will improve all elements that will be limiting after successfully eliminating the membrane (Electrode and electrolyte development, sustainability and techno-economic assessments). With an unrivalled low Levelized Cost of Storage MELODY’s solution is best positioned to change storage from a pure cost factor into a valuable business cases and will enable a wider integration of renewables in the European energy mix. To successfully complete all objectives as set out in the call, MELODY brings together a world-class consortium of SME’s (Elestor, PV3 Technologies, Vertech), industry (Shell) and academic leaders (TU Delft, Technion, University of Exeter, ETH Zurich) that has all required know-how and capabilities to complete the project.