Hydrogen is seen as a clean energy carrier that will aid in phasing out fossil fuels, and liquid hydrogen will likely play a role in the global hydrogen economy. However, Life Cycle Assessment researchers and process engineers widely report having insufficient means to accurately assess the environmental impacts of hydrogen liquefaction. This thesis presents an LCA study of hydrogen liquefiers based on current public data and literature. Additionally, a simplified model for hydrogen liquefaction was developed to aid future LCA researchers. An original Life Cycle Assessment of hydrogen value chains incorporating liquefaction is also included. The environmental harm was calculated in the form of direct monetary prevention costs, using the increasingly popular Eco-cost method. The environmental impacts of various sizes and types of hydrogen liquefiers are compared, while hotspots of environmental harm were determined. The main findings indicate that the primary source of environmental impact for hydrogen liquefaction is power consumption, with refrigerant leakage being insignificant as long as hydrocarbons are used for the precooling mixture.

Airborne Wind Energy (AWE) technology provides an interesting re-design for energy generation from the wind. The value of renewable energy systems is their ability to generate electricity with reduced environmental impacts, most crucially being the Global Warming Potential. In this project, it is assessed what the impacts of a potential Multi-Megawatt AWE system would be. Firstly to determine where its impact hot-spots are located and secondly to assess how this new technology would compare to conventional wind energy systems operating in the same farm. The location of the farm is included as a sensitivity parameter to assess the advantages and disadvantages of both systems for operation in various locations under different environmental conditions. The technologies were assessed and compared using a Life Cycle Assessment (LCA) method. The LCA is used to assess the systems for their Global Warming Potentials (GWP) and their Cumulative Energy Demands (CED). The CED is subsequently also used to determine the Energy Payback Time (EPBT) and the Energy Return of Investment (EROI) of both systems. The assessment of the impacts was performed on models that first had to be designed. The many unknowns and variables in both designs meant that modelling accounted for a large fraction of the project. The AWE system is modelled as a Ground-Gen, Rigid-Wing system based on the design of Ampyx Power. The HAWT system is designed to represent an accurate comparison model for the AWE system. It is fully based on various literature sources, primarily on optimisations of the NREL 5MW. It was found that the impacts of the HAWT system greatly depends on environmental conditions at the location for which it is designed. The AWE system does however only minimally depend on the environmental conditions. Thereby, it can be evaluated where AWE would have the largest advantage over HAWT technology and where HAWT technology may be better. The project is carried out in collaboration with Airborne Wind Europe and Ampyx Power. Data was intended to come from Ampyx Power. However, the project started too early into delayed feasibility studies which limited the availability of design data and even concept plans. The report therefore presents the impacts of a potential future 5 MW system. Modelled to the best ability at this time, with an hydraulic drivetrain and a hub-less drum design. Additional focus is placed on the availability of improvement potentials and assessment of design variables. Thereby aiming to further improve general sustainable knowledge within the AWE sector. The AWE system is found to use significantly less materials and to produce electricity at notably lower impacts compared to the HAWT system. AWE is found to be most advantageous for operation at unfavourable environmental conditions, where the wind speed is low, and the HAWT system requires a large hub-height. The Land and Launch Apparatus (LLA) and the Power Generation Apparatus (PGA) subsystems are found to be the largest impact contributors within the AWE system. The largest impact component is found to be the hydraulic accumulator system in the PGA, primarily due to its large mass. Its high impacts are closely followed by the light weight tether and aircraft subsystems that require materials with high specific impacts.