AGICO is a steel and fabrication service supplier in China. Besides standard steel plates and pipes, we also supply steel fabrications covering wind tower foundations and steel wind towers. Since renewable energy sources such as solar power and offshore wind power are playing an increasingly critical role in the green energy structure. As wind turbine tower technology matures and costs continue to decline. Among the various foundation solutions in offshore wind, the monopile foundation stands out as the most widely adopted foundation type due to its simple structure, quick installation, and cost-effectiveness.
Here AGICO leads you through the complete construction process of offshore wind power monopile foundations, showing you how these giant wind turbine towers are firmly rooted on the seabed.
What is an Offshore Wind Power Monopile Foundation?
A monopile usually refers to a giant steel pipe pile used as the foundation for an offshore wind turbine. It is driven directly into the seabed using specialized pile-driving equipment. Utilizing the friction between the pipe pile shaft and the surrounding soil, along with the support from the soil layer at the pile tip, the monopile function is to withstand the immense weight of the wind turbine generator and the complex loads generated by wind, waves, and currents. The monopile is the key foundation member to ensure the stability of wind turbine foundation.
AGICO supplies monopile fabrication service suitable for sea areas with water depths ranging from 15 to 30 meters. Due to its fast construction speed, controllable costs, and strong adaptability, it has been widely adopted in offshore wind farm projects around the world.
6-Step Construction Process of Monopile Foundations
The construction process of a monopile foundation for an offshore windmill can be separated into 6 steps; here are the details of how monopiles are installed step by step:
1. Pre-Construction Preparation
Preparatory work for monopile foundation includes 3 aspects: transportation equipment, pipe piles and accessories, and construction plan according to weather. These are the keys for the smooth monopile driving progress.
- Transportation and Pile Driving Equipment: The monopile installation requires key equipment for transportation and driving, which needs to be mobilized, including large floating crane vessels (with sufficient lifting capacity and resistance to wind and waves), high-performance hydraulic hammers (selected based on seabed geological conditions to ensure penetration through different soil layers), and precise positioning guide frames or pile grippers (used to control the entry position and verticality of the pile accurately).
- Transport of Construction Materials: Monopiles manufactured at specialized factories must undergo strict quality inspections before being transported to the site. During maritime transportation, meticulous anti-corrosion and anti-collision measures must be taken. Upon arrival at the construction site, a secondary inspection is necessary to ensure they are in perfect condition before use.
- Weather of Site Environment: Before construction commences, it’s essential to fully analyze information about tides, waves, currents, wind speed, and visibility during the planned construction period. Based on this data, detailed construction plans and emergency response plans can be formulated to ensure operational safety.
2. Guide Frame Installing
The guide frame is installed before the monopile driving. It acts as the ruler, ensuring the monopile is driven accurately onto the seabed. The guide frame structure is precisely lifted and placed at the predetermined seabed location by a floating crane, then fixed and leveled. If customer uses the pile gripper solution, it needs to be pre-installed on the floating crane vessel or specialized equipment, preparing to guide and hold the pile later.
(Image: Schematic Diagram of a Monopile Guide Frame)
3. Positioning the Foundation Pile
(Image: Monopile Transportation and Positioning)
The steel pipe pile (monopile) is transported from the barge and positioned under the main hook of the floating crane. Using the vessel’s dual-hook lifting system, the horizontally lying pile is slowly and smoothly upended into a vertical position. This process requires precise control of lifting points and speed to ensure even stress on the pile. Once vertical, the monopile is slowly lowered and accurately inserted into the pre-installed guide frame or pile gripper, where it begins to penetrate the seabed under its own weight (known as “self-penetration”). During this process, the monopile’s descent speed and attitude are closely monitored, with fine adjustments made if necessary.
4. Monopile Hammer Driving
(Image: Monopile Driving Operation)
Once the monopile is stable after self-penetration, the crane vessel lifts the massive hydraulic hammer and places it onto the pile head, commencing hammer driving. This is the most powerful step in the entire process. The hammer’s energy and frequency are adjusted in real-time based on geological conditions and the pile’s penetration feedback. The typical approach is “heavy hammer, light blow,” starting with low energy to test the geology and gradually increasing energy to drive the monopile to the predetermined depth. Driving ceases when the monopile reaches the design elevation and meets the final “stop-hammer criteria” (e.g., the average penetration per blow for the final set).
5. Guide Frame Removal
(Image: Guide Frame Removal)
After monopile driving is complete and the installation is verified as qualified, the guide frame shall be removed. A floating crane or other lifting equipment lifts the entire frame away, then transports it back to shore for maintenance or to the next turbine location. The removal of the guide frame shall not impact the newly installed monopile or the surrounding environment.
6. Subsequent Construction
The installed monopile needs to be protected through anti-corrosion and scour protection; transition pieces, flange and cable lines need to be installed and positioned properly for the tower installation later.
- Foundation Protection: Anti-corrosion treatment is applied to the exposed parts of the monopile (especially the splash zone), which usually uses high-performance coatings along with corrosion protection systems, to resist long-term seawater erosion.
- Scour Protection: Use materials (like rock armor) or under-base mattresses are placed on the seabed around the pile base for scour protection, this is to prevent currents and waves from eroding the soil around the pile, ensuring long-term stability.
- Integrated Secondary Steel Installation: Transition pieces (or flanges) are installed for connecting the tower body, also other secondary steel parts are installed in advance: cable ducts, boat landings, ladders, etc.
- Electrical Cable Line: Submarine cables are laid and terminated, preparing for future turbine power generation and grid connection.
Wind Turbine Monopile Construction Rules
The monopile construction is a large-scale project requiring heavy equipment and installation technology; any failure can lead to an accident with huge costs. Each step shall be completed according to 3 principles:
- Safety: Workers shall strictly adhere to operating procedures, closely monitor sea state changes, and ensure the safety of personnel and equipment.
- Quality Control: Each installation step requires strict inspection and documentation to ensure the installation quality, which is key for the monopile foundation to meet the design service life.
- Environmental Protection: Analyze and predict the marine environment in advance, adjust construction plans promptly, and minimize the impact on the marine ecological environment as much as possible.
Monopile – Best Option For Offshore Wind Power
As the global demand for wind energy continues to grow, offshore wind power is facing unprecedented opportunities. As a mature, efficient, and economical foundation type, the monopile will undoubtedly continue to play a key role in future deep-water and far-offshore wind farms, as well as in integrated development with other marine industries (such as marine ranching and offshore energy hubs), forming a clean and low-carbon wind energy system.
AGICO offers flexible foundation solutions for onshore and offshore wind farms, specializing in anchor cages and monopile foundations. Our product line includes high-strength anchor bolts, wind turbine bolts, and tower bolts. Beyond steel components, we also provide comprehensive fabrication services for both lattice and tubular steel towers, catering to diverse wind tower construction needs.
