Comparison of Operation and Maintenance of Floating 14 MW Turbines and Twin 10 MW Turbines

Turbine ratings in the past decade have grown unexpectedly fast. In 2021, Siemens Gamesa and GE revealed their new 14 MW turbine models, and it is predicted that this is not yet the rating limit that turbines can reach. Increased turbine ratings can also be achieved by putting two turbines on a single foundation. This study analyzes how operation and maintenance (O&M) would differ if a floating wind farm had twin 10 MW turbines installed on each substructure, instead of a single 14 MW turbine. This study demonstrates how the strategic O&M simulation tool compass can be used to perform this comparison. Assumptions regarding the O&M of twin turbines were estimated with the major floating twin turbine developer Hexicon AB. This study analyzed four cases—a case with 35 twin 10 MW turbines, and three cases with 50 single 14 MW turbines—to understand the potential effect of increased consumable costs, spare part lead times, and maintenance durations. All cases had the same wind farm capacity of 700 MW. The results show that O&M for cases with single turbines is at least 4.5% more expensive than the case with twin turbines. The case with twin turbines also resulted in a higher availability than any other case. Additionally, results showed that operational expenditure (OPEX) for the cases with single turbines is at least 6.0% higher in scenarios with single turbines than in the twin turbine scenario. The biggest cost contributors to the difference between scenarios were craft costs, particularly cable laying vessels and tugs. Due to the higher number of cables required for the scenario with single turbines, there is more frequent mobilization of cable vessels for cable repairs

Life cycle assessment of four floating wind farms around Scotland using a site-specific operation and maintenance model with SOVs

This paper presents a life cycle assessment (LCA) of the International Energy Agency (IEA) 15 MW Reference Wind Turbine (RWT), on floating platforms, deployed in commercial-scale arrays at multiple locations around Scotland in the ScotWind leasing round. Site-specific energy production and vessel operations are provided by a dedicated offshore wind farm operations and maintenance (O&M) model, COMPASS, allowing service operation vessel (SOV) O&M impacts to be assessed with increased confidence. For climate change, the median global warming impact varied from 17.4 to 26.3 gCO2eq/kWh across the four sites within a 95% confidence interval using an uncertainty assessment of both foreground and background data. As is common with other offshore renewable energy systems, materials and manufacture account for 71% to 79% of global warming impact, while O&M comprise between 9% and 16% of the global warming impacts. High-voltage direct current (HVDC) export cables, floating platforms, and composite blades are significant contributors to the environmental impacts of these arrays (by mass and material choice), while the contributions from ballast, vessel transportation emissions, and power-train components are lower. The results suggest that material efficiencies, circularity, and decarbonizing material supply inventories should be a priority for the Scottish floating wind sector, followed by minimizing vessel operations and the decarbonization of vessel propulsion, while avoiding burden shifting to other impact categories

Analysing the effectiveness of different offshore maintenance base options for floating wind farms

With the growth of the floating wind industry, new operation and maintenance (O&M) research has emerged evaluating tow-to-port strategies , but limited work has been done on analysing other logistical strategies for offshore floating wind farms. In particular, what logistical solutions are the best for farms located far offshore that cannot be reached by crew transfer vessels (CTVs)? Previous studies have looked at the use of surface effect ships (SES) and CTVs during the operation and maintenance (O&M) of bottom-fixed wind farms, but only some of them included service operation vessels (SOVs). This study analyses two strategies that could be used for floating wind farms located far from shore using ORE Catapult's in-house O&M simulation tool. One strategy comprises of having a SOV performing most of the maintenance on the wind farm, and the other strategy uses an offshore maintenance base (OMB) instead, which would be located next to the offshore substation and would accommodate three CTVs. This paper provides an overview of the tool and the inputs used to run it, including failure rates of floating wind turbine subsea components and their replacement costs. In total six types of simulations were run with two strategies, two different weather limits for CTVs and two weather datasets ERA5 and ERA-20C. The results of this study show that the operational expenditure (OPEX) costs for the strategy with an OMB are 5%-8% (depending on the inputs) lower than with SOV, but if capital expenditure (CAPEX) costs are included in the analysis and the net present value (NPV) is taken into account then the fixed costs associated with building the offshore maintenance base have a significant impact on selecting a preferred strategy. It was found that for the case study presented in this paper the OMB would have to share the foundation with a substation in order to be cost competitive with the SOV strategy

Comparison of operation and maintenance of floating 14MW turbines and twin 10MW turbines

Turbine ratings in the past decade have grown unexpectedly fast. In 2021 Siemens Gamesa and GE revealed their new 14MW turbine models, and it is predicted that this is not yet the rating limit that turbines can reach. Increased turbine ratings can also be achieved by putting two turbines on a single foundation. This study analyses how Operation & Maintenance (O&M) would differ if a floating wind farm had twin 10MW turbines installed on each substructure, instead of a single 14MW turbine. This study demonstrates how the strategic O&M simulation tool COMPASS can be used to perform this comparison. Assumptions regarding the O&M of twin turbines were estimated with the major floating twin turbine developer Hexicon AB. This study analyzed four cases - a case with 35 twin 10MW turbines, and three cases with 50 single 14MW turbines - to understand the potential effect of increased consumable costs, spare part lead times and maintenance durations. All cases had the same wind farm capacity of 700MW. The results show that O&M for cases with single turbines is at least 4.5% more expensive than the case with twin turbines. The case with twin turbines also resulted in a higher availability than any other case. Additionally, results showed that Operational Expenditure (OPEX) for the cases with single turbines is at least 6.0% higher in scenarios with single turbines than in the twin turbine scenario. The biggest cost contributors to the difference between scenarios were craft costs, particularly cable laying vessels and tugs. Due to the higher number of cables required for the scenario with single turbines, there is more frequent mobilization of cable vessels for cable repairs

Comparison of operation and maintenance of floating 14MW turbines and twin 10MW turbines

Turbine ratings in the past decade have grown unexpectedly fast. In 2021 Siemens Gamesa and GE revealed their new 14MW turbine models, and it is predicted that this is not yet the rating limit that turbines can reach. Increased turbine ratings can also be achieved by putting two turbines on a single foundation. This study analyses how Operation & Maintenance (O&M) would differ if a floating wind farm had twin 10MW turbines installed on each substructure, instead of a single 14MW turbine. This study demonstrates how the strategic O&M simulation tool COMPASS can be used to perform this comparison. Assumptions regarding the O&M of twin turbines were estimated with the major floating twin turbine developer Hexicon AB. This study analyzed four cases - a case with 35 twin 10MW turbines, and three cases with 50 single 14MW turbines - to understand the potential effect of increased consumable costs, spare part lead times and maintenance durations. All cases had the same wind farm capacity of 700MW. The results show that O&M for cases with single turbines is at least 4.5% more expensive than the case with twin turbines. The case with twin turbines also resulted in a higher availability than any other case. Additionally, results showed that Operational Expenditure (OPEX) for the cases with single turbines is at least 6.0% higher in scenarios with single turbines than in the twin turbine scenario. The biggest cost contributors to the difference between scenarios were craft costs, particularly cable laying vessels and tugs. Due to the higher number of cables required for the scenario with single turbines, there is more frequent mobilization of cable vessels for cable repairs