Reviewing resource criticality assessment from a dynamic and technology specific perspective - using the case of direct-drive wind turbines

The recent debate on potential resource constraints for the broad scale implementation of clean energy technologies in future has led to wider concern across the board. This concern, among others, lies behind growing research in the field of so-called resource criticality. This study is a review of existing resource criticality assessment methodologies. It characterizes and analyses existing methods and identifies aspects of concern for the ability of assessment methods to provide proper guidance for strategy making in the field of energy system development. The validity of the identified concerns is, further, demonstrated by applying a case study of resource criticality assessment of the direct-drive wind turbines technology. Two key concerns are identified. The first is the need for a dynamic perspective on the supply risk dimension. This study reveals that the geological reserve estimates and geographical location of supply change significantly over time, implying that the static supply risk assessment provided by many methods gives misleading guidance. The second concern is the ability of methods to properly account for the vulnerability of the studied system to a supply disruption of the resource in question. Through the case study, the options for resource substitution are elaborated for wind turbines by applying a holistic design approach looking at all levels of design substitutions from the level of materials and components to subassemblies and whole-product concepts. This approach reveals that the dependence of substances like neodymium and dysprosium is not strong, and that they are not essential to the wider implementation of direct-drive wind turbines in general. This technology specific and product design based approach is new, and questions the ability of existing methods to properly address the impact that the risk of supply disruption of a given resource really has on the technological and economic development of a system or technology under study.