Ilinca Julian, Heikki Ojanen, Juha - Matti Lukkari

 Higher and steadier wind speeds.  Usually installations unvisible from land.  Their noise cannot be heard from land.  More demanding environment than for onshore.  More expensive maintenance costs.

 Rotor diameter 90 m now commonplace.  Designed to withstand vertical wind gradient and also athmospheric turbulance.

 Monopile, for < 20 m depth  Jacket, used already in oil industry  Tripod, for < 20 m depth  Tripile, up to 50 m depth  Gravity, been used up to 10 m depth  Floating, for deep waters  At least monopile and tripod cannot be used on a stony sea bed.

 Trend is to locate wind farms close to eachother.  Knowledge of wind profiles is key importance  Knowledge of composition of seabed sediment layers is essential.

 Has effect on project performance, size and cost  Legal, regulatory and geophysical reasons  Spacing between turbines aligned in a row is on the order of 5 to 10 rotor diameters, and spacing between rows is between 7 and 12 rotor diameters.

 Affects on organisms and habitats.  Data gathering far from simple.  Many planned wind farms close to fishery sites in North Sea.

 Collection system  Medium voltage grid within the wind farm  Connects the wind turbines to the offshore substation  Offshore substation  Transmission system  Between the offshore and onshore substations  High voltage AC or DC

 Usually a string cluster configuration  Several turbines in every string  Each WT with a step-up transformer  Generation voltage 690V  Grid voltage typically around 30kV  The grid must carry all the generated power in the string  Limited by the size of the step-up transformers

 Lines of the collection system meet here  Substation based on a platform  Power transformer  Rated power up to several hundred MVA  Limited by the weight of the transformer  Steps up the voltage to a transmission voltage Power electronics (In case of a HVDC link)  Rectifier and filter units

Nysted wind farm (Denmark) Lillgrund wind farm (Sweden)

 Distance to the on-shore substation  Reactive losses (AC) vs resistive losses (DC)  d < 50km  AC  50km < d < 80km  AC or DC  d > 80km  DC  HVDC technology more expensive  Newer technology  Requires more components & space

 The cost of cable connection from the farm to the onshore grid.  Foundations costs.  Operation and maintenance costs.  Protection from corrosion due to saltwater.

 Competition  2012 work was carried out on 13 wind farms.  Development growing and encouraged  Government support Off-Shore wind developers’ share of grid connected capacity from 1 st January to June 30 th. Source: EWEA

Source: EWEA

Initiative to build larger turbines. Currently demand outstrips supply for the significant global requirements. Full capacity for a larger fraction of the year. Price of power.

 Solid and continues to grow  Trust -Suitable funding structures -non-resource financing

 Capital costs, maintenance costs and operation costs  Annual Cost  leveled costs are expected to decrease Source. C: Howland, Caitlin M., "The Economics of Offshore Wind Energy" (2012). Honors College. Paper 60.

 High and predicted to increase  Macroeconomic reasons  Supply and Demand!  Forecasting improvement  Competition

 Turbines contribute most to the cost  Materials  Costs of different base structures have the second largest impact on the finance  Cost efficiency may be grater in deep water farms  stable energy production