H2REF-DEMO aims to further develop and scale up by a factor of 5 the innovative compression concept developed in H2REF, in order to address large vehicle refuelling applications requiring hydrogen to be dispensed at rates of hundreds of kg/h, such as bus fleet refuelling every evening at the bus depot, truck refuelling, and train refuelling. Thanks to demonstrating the process during one year for commercial 35 MPa refuelling of trucks, the project will bring to TRL7 the disruptive compression technology previously developed in the H2REF project and already validated for 70 MPa refuelling of light duty vehicles. Along with capacity scale-up, H2REF DEMO will focus on process optimisation, cost reduction and further durability testing, Full optimisation will be achieved by first developing a digital twin of the scaled-up process. Use of accumulators with shells in hoop wrapped steel (Type II), a suitable technology for 35 MPa refuelling, will allow to optimise costs. A thorough accelerated testing approach involving at least 500 hours of continuous operation, will allow to verify durability of the accumulators and the compression stages over the full range of operating conditions. The demonstrated system is expected to provide a peak dispensing capacity of 150 kg/h, amounting to 1200 kg/d with 8 hours of daily operation, with a targeted cost of 1200 €/(kg/d). The process is expected to reduce electricity consumption to 3.5 kWh/kg of dispensed hydrogen, from production on site at 2 MPa to vehicle tank at 42 MPa. The knowledge gained will allow subsequent development to focus on commercial product development for short term commercial deployment. A multi-disciplinary team, composed of 4 industrial companies and 3 RTOs, combining expertise in hydraulic power supply, in bladder accumulator, in process simulation, modelling process digital twins, in H2 refuelling and distribution stations is gathered in the consortium to reach the targeted KPIs of H2REF-DEMO.