Life Cycle Assessment of a wave energy device – LiftWEC

Abstract

The need to move towards a low-carbon economy has brought about the emergence of various renewable energy sectors, including Marine Renewable Energy (MRE). However, after many years of research and development, the MRE industry still faces challenges in achieving commercial viability, especially regarding wave energy. Whilst it remains possible that successful wave energy technologies exist in the traditional research trend, it is also appropriate to explore alternatives that produce energy by different approaches. Wave-induced lift force devices may be the possibility to move beyond traditional wave energy technologies using diffraction and/or buoyancy forces. In this context arises the LiftWEC, a promising configuration of a lift-based wave energy converter. The LiftWEC device couples with the waves through lift forces generated by two hydrofoils that rotate in a single direction aligned orthogonally to the direction of wave propagation.

To fully evaluate the overall advantages of this new technology, it is necessary to go beyond the techno-economic performance and reliability. While capable of producing electricity from clean sources, MRE devices are not entirely environmentally friendly, since energy is consumed and pollutants are emitted during their various life cycle stages. Accordingly, as the MRE sector expands, it is important to ensure that the technologies prove to be sustainable alternatives in terms of their environmental impact.

Life Cycle Assessment (LCA) is a widely recognized methodology to evaluate environmental impacts by considering the technology’s performance over its life cycle. This methodology complies with international standards ISO 14040, which specify the general framework, principles, and requirements for conducting and reporting this type of assessment.

A “cradle to grave” LCA assessment was applied to the LiftWEC device to evaluate the potential cumulative environmental impacts of the system, complete from the extraction of raw materials until decommissioning. Each stage was analysed within the defined system boundaries, and data on the energy, materials, emissions, and waste products associated were gathered. To allow comparison with other MRE technologies and traditional means of electricity generation, carbon dioxide equivalent emissions per produced electricity (gCO2eq/kWh) were calculated for the study.

Since ocean energy is broadly considered to contribute to a low-carbon energy system, special attention was given to the LCA results on the global warming potential (GWP). Besides a set of 18 impact categories, Cumulative Energy Demand (CED) and Carbon and Energy payback time (CPT and EPT, respectively) were also analysed. The CPT and EPT are important indicators that measure the time required to offset the carbon emission and demanded energy, respectively, accounted across all development phases of the device.

This work included the comparison of LCA findings for other MRE devices reported in the literature to validate the viability of the LiftWEC in terms of carbon and energy footprint. In addition, the assessment analysed alternative materials, locations, and recyclability allowing the identification of potential improvement opportunities regarding the reduction of environmental impacts.