LARGE-SCALE OFF-SHORE WIND POWER

Ilinca Julian, Heikki Ojanen, Juha - Matti Lukkari

Wind power at sea

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.

Turbines

Rotor diameter 90 m now commonplace. Designed to withstand vertical wind

gradient and also athmospheric turbulance.

Foundations

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.

Placing

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.

Off-Shore wind farms in europe

Layout of Turbines

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.

Environmental effects

Affects on organisms and habitats. Data gathering far from simple. Many planned wind farms close to fishery

sites in North Sea.

Electrical system overview

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

Collection system

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

Offshore substation

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)

Transmission system: HVAC vs HVDC

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

Off-shore wind farm with HVAC

Off-shore wind farm with HVDC

Comparison to on-shore wind

The cost of cable connection from the farm to the onshore grid.

Foundations costs. Operation and maintenance costs. Protection from corrosion due to saltwater.

Developers

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 1st January to June 30th. Source: EWEA

Current Construction

Source: EWEA

Grid connection Costs

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.

Finance

Solid and continues to grow Trust

-Suitable funding structures-non-resource financing

Private Costs

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.

Capital Costs

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

Turbines and Structures

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

Thats all folks