Analysis of Weather Windows and Impacts of Time to Repair on Device Availability at Two Wavepiston Deployment Sites

Abstract

The levelized cost of energy (LCoE) for wave energy converters (WECs), involving capital and operational expenditure, annual energy production, and the deployment lifespan, is a key metric for evaluating lifetime wave energy generation costs, influenced by several factors, including device availability. WEC availability depends on both device reliability and deployment site accessibility for maintenance or repair activities, where accessibility is determined by maintenance vessel operating criteria and site met-ocean conditions. Extended maintenance waiting periods, between weather windows that allow safe operation and maintenance (O&M) activities, reduce availability and annual energy production, resulting in an increased LCoE. Therefore, accurate estimates of O&M weather windows and overall site accessibility are essential for improving LCoE assessment.

Typically, wave height and wind speed are considered when deciding whether O&M vessels can access WEC sites. However, seasonal variations in wave height and wind speed can cause higher device failure rates during certain seasons and lead to longer maintenance waiting periods and increased downtime. Additionally, in the early stages of marine renewable energy projects, maintenance operations are often limited to daylight hours, and this restriction should be factored into statistical estimates of wait times between O&M weather windows.

This study develops a comprehensive weather window analysis of met-ocean data to support robust estimates of annual site access levels and maintenance waiting periods, based on realistic O&M vessel constraints. It focuses on two deployment sites, at Wavepiston’s current full-scale demonstration site off the east coast of Gran Canaria and at a commercial site off the north coast of Gran Canaria. The analysis explores the impact of seasonal variations and daylight maintenance requirements on weather window assessments, focusing on the persistence of weather windows and duration of wait times between windows. The distribution of wait times and seasonal variations are derived from historical wave height and wind speed data, both with and without the daylight requirement. This approach allows an assessment of the impact of seasonal variations in met-ocean conditions and daylight maintenance constraints on site accessibility and device availability.

By incorporating realistic maintenance constraints into weather window analyses, this study aims to reduce uncertainty in device availability estimates, supporting a more accurate LCoE assessment of a Wavepiston farm. By doing so, this study aims to support Wavepiston development towards a higher technology readiness level, ultimately advancing the commercialization of wave energy technology. This research is funded by Horizon Europe under the SHY project (Seawater Hydraulic PTO using dynamic passive controller for wave energy converters).