Author: Anders Moeller Telephone: Company: Densit ApS Origin: Denmark

Transcription

1 Efficient offshore wind turbine foundations Author: Anders Moeller Telephone: Company: Densit ApS Origin: Denmark

2 Efficient offshore wind turbine foundations Introduction l l For centuries mankind has used wind resources for sailing. Today the use of wind includes power production from offshore wind turbines.

3 Headlines Turning offshore Offshore wind turbine foundation structures Monopile structures (75% of all installations to date) Dimensions Installation methods and tools Transition piece, grout seal and grout method Grout types and properties Installation vessels and jack-ups New methods and solutions for foundations at deeper water Closing

4 Turning offshore In 1990 the first offshore wind turbine was installed in Nogesund Sweden, 1000 feet off the coast and at a water depth of 20 feet. The turbine was a 210 KW Wind World stall regulated machine. Foto: Mats Nying Svante I

5 UHPC Offshore wind turbine foundation structures Rock drilled monopile Driven monopile with grouted transition piece Gravity foundation

6 Monopile structures - Dimensions Principle of driven monopile with grouted transition piece Grout pipe with three inlets Transition piece with tower flange Brackets with hydraulic jacks msl Grout seal Monopile Pile sizes: 3-5,1 m ( inch) Overlap: 1,33 to 1,6 x pile outer diameter Annuli: mm (2-5 inch) Water depth: 4-25 m (13-75 feet) Penetration: m ( feet depending on soil)

7 Installation methods and tools A2SEA - Sea Jack Jack-up crane barge loaded with monopiles and transition pieces

8 Installation methods and tools Hammer size and drive force The German manufacturer Menck is offering hydraulic hammers for driving big monopiles in the below classes. Pile in drive gate with hammer in place MHU Energy Weight Length (KJ) (t) (m) (feet) 550S S S

9 Installation methods and tools Drive drill drive Two different applications for drilling inside the pile in order to drive the pile to final depth

10 Installation methods and tools Installation of transition piece

11 Installation methods and tools Connecting the grout hose from the pump at the batch mixing station to the inlet at the transition piece

12 Installation methods and tools Levelling of transition piece Position for hydraulic Jack

13 Transition piece, grout seal and grout method The most common grout seal for these applications has been a lip type rubber seal. The company MT Hojgaard has tested and patented a solution which has performed outstanding. The grout is led to the bottom of the transition piece and normally distributed to 3 inlets placed just above the grout seal.

14 Grout types and properties The most commonly used grout type is the ultra high performance Ducorit S5 with a mean compressive strength of psi (130 MPa)

15 Grout types and properties Grout material, strength development Ducorit S5 & D % Relative property Elasticity Flexural strength Compressive strength Days Duration factor (= 1 AT 20 C) Temperature C

16 Grout types and properties Densit versus good quality reference concrete

17 Installation vessels and jack-ups Seacore A2SEA A2SEA HSS HSS A2SEA MPI

18 New methods and solutions for foundation at deeper water Tripod for the German project Alpa Ventus designed for 30 m water dept. Tripod Design Study where center transition piece is connected with high performance grout and thereby increasing capacity of welded joints.

19 New methods and solutions for foundation at deeper water New patented concept developed by the German company Bard Engineering. The three pile structure with a connecting structure grouted to the piles is designed for a 5 MW wind turbine

20 New methods and solutions for foundation at deeper water Piles installed for the three pile structure.

21 New methods and solutions for foundation at deeper water The connecting structure is designed for a 5 MW wind turbine.

22 New methods and solutions for foundation at deeper water The connecting structure in place ready to be grouted

23 New methods and solutions for foundation at deeper water For deeper water a steel structures like OWEC Jacket Quattropod (OWEC Tower AS) can be selected as the foundation. The Jacket is secured with pile/sleeve connections.

24 Closing The offshore wind turbine part of the market is still only a fraction of the onshore installations. Until now approximately MW have been built or are under construction. Looking at the forecast for Europe this number will be passed by far during the next decade. When moving to greater water dept. (30m+), it is important that all parts of the structures are made more cost effective. Alternatively new cost efficient methods are developed for deeper waters in order to make the offshore installations competitive. Furthermore the wind turbines need to be more reliable because it is very costly to service and repair the turbines offshore.