Life cycle assessment of MHP (Mobile Hydrogen Powersupply), an off-grid system to charge battery electric vehicles

Abstract

PurposeThe paper introduces MHP (Mobile Hydrogen Powersupply), an off-grid fuel cell electric system to recharge (stranded) BEVs, and discusses MHP from the life cycle perspective. The LCA shows the effects of system architecture, charging efficiency, hydrogen supply routes, and the predicted electric vehicle recharging demand on global warming potential and energy consumption and further gives recommendations to optimize the assessed environmental impact.MethodsDemand scenarios of mobile recharging assistances due to BEVs, stranded with an uncharged battery, are predicted for Austria and the greater Vienna area. The introduction of MHP follows the discussion of system architecture, operation strategy, and energetic charging efficiency. The LCA follows the guidance of the ISO 14040 standard and applies the Circular Footprint Formula. The functional unit is 1 kWh of electrical energy, balanced at the charging interface. The system boundary includes raw material extraction, production, transport of resources and products, use, and end of life management. The hydrogen supply is modeled representatively for Austria. The selected impact categories are global warming potential and cumulated energy demand. The data originate, among others, from GEMIS Austria, GREET2, and ProBas.Results and discussionEnvironmental impacts vary between 0.40 and 1.58 kg CO2eq/kWh-el and 4.95 to 7.68 kWh/kWh-el in the life cycle. In production and end of life processes, the hydrogen storage system leads to the highest weight-specific GWP and CED of MHP sub-systems due to the large share of CFRP. The efficiency of the MHP system is directly reflected in the use phase’s environmental impacts. The impact of MHP cooling efficiency, charging efficiency, and operation strategy on GWP and CED is below 12%. The CED primarily originates from hydrogen production. If the hydrogen supply route is mostly renewable and generates minor GWP, the MHP efficiency has only a small impact on the life cycle’s GWP and the production and end of life processes gain importance.ConclusionsOptimized material selection and lightweight construction reduce the life cycle impact. Further, the paper demonstrates that hydrogen supply significantly affects MHP’s environmental impact. Therefore, besides optimizing the production and end of life processes, implementing a renewable hydrogen infrastructure and providing renewable energies and fuels must be strongly accelerated.