title: Environmental impacts and emissions reduction potential of floating wind and marine energy in future energy scenarios of Great Britain
Creators: name: Struthers, Iain Andrew
Publisher: name: The University of Edinburgh
Year: 2025
Subjects: subject: Life cycle assessment
subject: Wave energy
subject: Floating wind
subject: Power system modelling
subject: Avoided emissions
subject: Emissions reduction potential

description: Humans are unequally causing environmental harm through consumption of natural materials and energy beyond sustainable limits. Amongst the most severe and cross-cutting human induced pressures on Earth is climate change. This is driven by higher average temperature from increased retention of solar energy via increased atmospheric concentrations of greenhouse gases released by human activities; primarily carbon dioxide (CO₂) from combustion of fossil fuels: oil, gas and coal. This thesis considers the environmental impacts and climate change impacts of novel forms of offshore renewable energy, and assesses how effectively they can obviate emissions from fossil fuel power generation, using the electricity system of Great Britain as a case study. The United Kingdom and its devolved nations have enshrined in law a target to achieve net zero greenhouse gas emissions by 2050 or earlier. Simultaneously, the UK’s oceanic climate and island geography are well placed to host significant installed capacities of offshore wind which will form the backbone of the power system in almost all Net Zero scenarios, and – although to a lesser extent – marine energy (wave and tidal stream). These renewable energies obviously forgo fossil fuels as a primary consumable, but do include non-zero environmental impacts via their construction, operation and disposal. Wave energy remains an untapped source of renewable electricity, with ongoing technological development beginning in the 1970’s. Studies of the life cycle environmental impacts of arrays of new wave energy converter (WEC) devices are uncommon, and a life cycle assessment (LCA) of a novel device – the Blue Horizon – is presented here, deployed in four utility-scale arrays including a substation, highly detailed vessel representation and site-specific energy production, finding a global warming impact of 68.3 to 94.9 gCO₂eq/kWh across the arrays and carbon payback beyond the lifetime of the array when future scenarios of carbon intensity are used. Conversely, UK floating wind deployment is growing. Here, arrays of the International Energy Agency (IEA) 15 MW Reference Wind Turbine (RWT), on floating platforms arranged in commercial-scale arrays at multiple locations are assessed and compared to the wave energy results, finding a climate impact of 17.4 to 26.3 gCO₂eq/kWh, and a payback time of three to twelve years depending on future scenario. Site-specific energy production and vessel operations are provided by a dedicated offshore wind farm operations and maintenance (O&amp;M) model, COMPASS, allowing service operation vessel (SOV) O&amp;M impacts to be assessed with increased confidence. The next aspect of the thesis considers ways of modelling the integration of these life cycle impact assessments with the wider energy system. To permit this, projections for wave and tidal stream installed capacities are developed with discrete geospatial coordinates of potential deployment sites to create three scenarios (low, mid and high) of future deployment around GB. These scenarios are then used with a new power system modelling tool, PyPSA-GB, and Future Energy Scenarios (FES) from National Grid, to consider the emissions reduction potential of marine renewable generation in the future, and how this relates to the static attributional impacts from preceding LCA studies. Accounting for the fleets of generation within the FES finds that carbon payback is almost never achieved for the cases considered, and that complementarity has a limited effect on the technology’s climate change mitigation efficacy, which is simply dominated by the installed capacities in the future scenarios.