Offshore wind and wave power rigs. Systems description by:

Vegårshei,Aug 2011, Gunnar Ettestøl 1

Offshore wind and wave power rigs.

Systems description by:

Gunnar Ettestøl, ETTE Elektro,

4985 Vegårshei, NORWAY


Offshore wind and wave power rigs.

• The wind and wave rigs must be designed for survival.• Rigs with only wind turbines can be built rigid. 6 or 14 MW rigid rigs must be built to withstand wave heights from 30

to 45m• Wave energy pickups in combined rigs must be lifted up before they

are hit by dangerous waves. Usable wave height, max 10m.• The use of 2 contra rotating wind turbines in combined rigs must give

necessary vertical load for the wave energy pickup system.• Combined wind and wave rigs must be built to withstand movements

within the construction, with the use of plastic bearings in the rig joints. Max wave height 30 m.

• A small model of a combined wind and wave rig has been built in 2009. This rig will undergo further testing in 2011.

• The model was built in 1:3 size of the 4.6 kW unit shown here.



• 4.6 kW test rig for wind- and wave energy, front view.

• The rig shall first be tested with the wave energy pickups installed.

• The rig shall be equipped with 2 units of contra rotating wind turbines of 2 kW at 9 m/sec wind speed.

• Up to 6 units of wave energy pickups of minimum 100W at 50cm wave height.


• Deck for 4.6 kW wind and wave energy rig.

• Construction of sheet steel or aluminium profiles.

• Demountable construction for easy transport.

• The rig can be tested without wave energy pickups, but then with direct drive permanent magnet generators, PMGs, on the wind turbines.


• 4.6 kW test rig for wind and wave energy, side view.

• Pitch regulated wind turbines connected to water pumps or PMGs.

• Wave energy pickups connected to single acting or dual side piston water pumps.

• The water is sent to pressure reservoir and from there to feed the wind turbine pumps .

• The pressurized water drives a small pelton turbine with a generator for the rig power supply.


Wind turbine system with PMG for floating rigs.


• 4 - 6 kW test rig for wind energy only, front view.

• The rig shall be equipped with 2 contra rotating wind turbines of 2kW at 9 m/sec wind speed.

• Digital 1:2:4:8 controlled hydraulic motor and electric generator.

• Max 2 m wave height.


• 4 to 6 kW test rig for wind energy only, side view.

• Pitch regulated wind turbines attached to rotary hydraulic pumps.

• Digital 1:2:4:8 controlled hydraulic motor and generator.

• Max 2m wave height


Hydraulic system for small wind turbines


Wind turbine high capacity STAR rotary pump

• Example of a large capacity quad closing wheel impeller type hydraulic ’star’ pump.

• Direct drive star configured piston pump may be an alternative.


Large offshore floating wind turbines:

• Rigs with 2 pitch controlled contra rotating wind turbines.

• The small 4 - 6kW model can be enlarged to small models for inshore use, then in sizes 6 to 60 kW.

• The construction can be brought further, to large rigid and stable floating offshore wind rigs that can be built in sizes from 6 to 14MW. The rigs must be built to withstand wave heights from 30 to 45 m.

• Rigs with 2 wind turbines can use 2 oil pumps, rotation type, and 1:2:4:8 hydraulic motor and generator


• Low cost 6 MW wind turbine rig, front view

• Stable, rigid construction

• 2 contra rotating 3 MW wind turbines

• Machinery: 2 oil pumps and 1:2:4:8 hydraulic motor and generator.

• Side-thrusters and ballast regulation in rear legs.

• Max wave heights: 45m top-bottom.


• 6 MW wind turbine rig, side view

• Rigid construction• 2 contra rotating 3

MW wind turbines• Machinery: 2 oil

pumps and 1:2:4:8 hydraulic motor and generator

• Side-thrusters and ballast regulation in rear legs.

• Max wave heights: 45m top-bottom.


Hydraulic system for 5 legs floating rigs.TP1 and TP2 are wind turbine pumps. HPT is high pressure tank. LPRT is oil return tank. PTR is pressure tank

for oil return from RPH return pump and motor MRH. M1 and M2 are hydraulic 1:2:4:8 motors for drive of generators G1 and G2. MT is thrust motor for direction control of the rig. MP1 and MP2 are pitch control motors (no reverse control in drawing). MP3 and MP4 are ballast pump motors for rear legs. Backup electric drive MEL

or diesel drive MD. Double throw valves are drawn for motor control, mvp1..4 and mvp1..4r.


Floating rigs with 2 vertical axis wind turbines

• Vertical axis wind turbines (VAWT) can be an alternative for use on rigid, combined wave and wind energy rigs, in particular for desalination plants.

• Large rigs: 300 kW to 3 MW, with or without wave energy pickups. Large rigs of this type can only be placed in waters where max wave height is moderate, or up to 15m p-p for 2-3 MW solutions.

• Advantages with the use of VAWT:

Pumps or generators can be placed on deck level.

Cheap, straight wing profiles.

High starting torque with use of an effective pitch mechanism.

• Disadvantages with the use of VAWT:

Vertical axis wind turbines are top-heavy as the rotating mass for a secure design becomes 4-5 times higher than for horizontal axis wind turbines, when the generators or pumps installed on deck level.


• FRONT VIEW OF A DESALINATION SYSTEM

• 2.6 MW wind and wave energy rig for production of fresh water with reverse osmosis.

• 2 contra rotating vertical axis wind turbines, 1MW each, hydraulic pitch control.

• 6 units of foil type 100kW wave energy pickups.

• Concrete/steel trimaran body.


• SIDE VIEW OF A DESALINATION SYSTEM

• 2.6 MW wind and wave energy rig for production of fresh water with reverse osmosis.

• 2 contra rotating vertical axis wind turbines, 1MW each, hydraulic pitch control.

• 6 units of foil type 100kW wave energy pickups.

• Concrete/steel trimaran body.

Documents

Offshore wind and wave power rigs. Systems description by: