planning. A combination of an offshore wind farm with aquaculture, e.g. as proposed already in 2002 by Buck (2002), Buck et al. (2004) and recently for the
Dutch North Sea by Lagerveld et al. (2014), involves both risks and benefits. The
potential risks include technical failures due to corrosion and biofouling; ecological
risks, such as underwater-noise disturbance of marine mammals, disturbance of the
seabed sediments and seabed communities; collision risks to birds and bats above
water, and attraction of invasive species. Benefits of combining an offshore wind
farm with offshore aquaculture can be found in eco-facilitation and in
economic/financial savings. Eco-facilitation refers to the enhancement of biological
diversity and production (e.g. by offering increased food availability and shelter,
thereby attracting flora and fauna). The economic/financial benefit refers to
expected synergy effects through sharing and thus savings on operation and
maintenance costs (Krause et al. 2011).
Section 4.2 provides an overview of relevant offshore O&M activities and an
analysis of O&M costs. Section 4.3 describes the potential for cost savings in a
combined offshore Multi-Use Platform (MUP), based on the example of a virtual
offshore wind-mussel-farm (OWMF), and it also depicts an Asset Management
Control (AMC) model, that could help to manage such a combined business.
The AMC model can, for example, simulate different O&M scenarios of a virtual
OWMF over 20 years. The chapter concludes with lessons learned and recommendations for pilot studies.
4.2 Offshore Operation and Maintenance Activities
4.2.1 Accessibility of Offshore Wind Farms
The offshore marine environment is characterized by harsh conditions. Project
developers of offshore wind farms have to cope with many logistical and safety
issues that developers of wind energy projects on land do not, or at least not to the
same extent. Operation and maintenance costs make up 25–30% of the total costs of
an offshore wind farm (Miedema 2012, cf. Sect. 4.2.5). This is almost as much as
the cost of the wind turbines and about as much as the costs of construction and
installation. Individual offshore wind turbines currently require about five site visits
per year: one regular annual maintenance visit, and three to four visits in case of
malfunction (cf. Noordzeewind website). With technological progress, this can
potentially be reduced to three visits per year. Nonetheless, a future offshore wind
farm consisting of 200 turbines of 5 MW each will therefore need some 3000
offshore visits per year. Operation and maintenance (O&M) visits are carried out by
boat or helicopter, which means that the personnel performing the repair, has to
climb onto the turbines. Especially in rough conditions—helicopters for example
are used at wind speeds of up to 20 m/s—this is a risky undertaking. Systems
need to be developed to ensure the safety of staff and to expand workability.
4 Operation and Maintenance Costs of Offshore Wind Farms …
99
Dutch North Sea by Lagerveld et al. (2014), involves both risks and benefits. The
potential risks include technical failures due to corrosion and biofouling; ecological
risks, such as underwater-noise disturbance of marine mammals, disturbance of the
seabed sediments and seabed communities; collision risks to birds and bats above
water, and attraction of invasive species. Benefits of combining an offshore wind
farm with offshore aquaculture can be found in eco-facilitation and in
economic/financial savings. Eco-facilitation refers to the enhancement of biological
diversity and production (e.g. by offering increased food availability and shelter,
thereby attracting flora and fauna). The economic/financial benefit refers to
expected synergy effects through sharing and thus savings on operation and
maintenance costs (Krause et al. 2011).
Section 4.2 provides an overview of relevant offshore O&M activities and an
analysis of O&M costs. Section 4.3 describes the potential for cost savings in a
combined offshore Multi-Use Platform (MUP), based on the example of a virtual
offshore wind-mussel-farm (OWMF), and it also depicts an Asset Management
Control (AMC) model, that could help to manage such a combined business.
The AMC model can, for example, simulate different O&M scenarios of a virtual
OWMF over 20 years. The chapter concludes with lessons learned and recommendations for pilot studies.
4.2 Offshore Operation and Maintenance Activities
4.2.1 Accessibility of Offshore Wind Farms
The offshore marine environment is characterized by harsh conditions. Project
developers of offshore wind farms have to cope with many logistical and safety
issues that developers of wind energy projects on land do not, or at least not to the
same extent. Operation and maintenance costs make up 25–30% of the total costs of
an offshore wind farm (Miedema 2012, cf. Sect. 4.2.5). This is almost as much as
the cost of the wind turbines and about as much as the costs of construction and
installation. Individual offshore wind turbines currently require about five site visits
per year: one regular annual maintenance visit, and three to four visits in case of
malfunction (cf. Noordzeewind website). With technological progress, this can
potentially be reduced to three visits per year. Nonetheless, a future offshore wind
farm consisting of 200 turbines of 5 MW each will therefore need some 3000
offshore visits per year. Operation and maintenance (O&M) visits are carried out by
boat or helicopter, which means that the personnel performing the repair, has to
climb onto the turbines. Especially in rough conditions—helicopters for example
are used at wind speeds of up to 20 m/s—this is a risky undertaking. Systems
need to be developed to ensure the safety of staff and to expand workability.
4 Operation and Maintenance Costs of Offshore Wind Farms …
99