Ilinca Julian, Heikki Ojanen, Juha - Matti Lukkari.
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Transcript of 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.
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
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
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
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.
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