Chapter Eleven - Commonly Used Installation Methods

Abstract

The method of installation of both foundations and turbines influences the staging port layout, size, and location to the offshore wind farm site. Manufacturers and contractors have developed specific strategies and working procedures for all of the different types of foundations and turbines. This chapter focuses on the various installation methods used for offshore wind farms. In general the industry prefers working with four types of foundations, which include gravity-based, monopile, jacket, and tripod foundations. The installation of a gravity-based foundation is largely carried out using three pieces of equipment, which include a large floating crane, a very large barge, and a tugboat or group of tugs that can tow either the barge, or both barge and crane. Monopiles are indeed easy to install, provided that the equipment, method statements, site preparations, and soil data are well defined and chosen. The main pieces of equipment used for the installation of monopiles include installation vessel, preferably jack-up; large hydraulical hammer for the pile-driving process; pile handling tool; grouting equipment; and if required, a drilling rig. The installation of the jacket foundation is fairly straightforward where the jacket stands on four anchor piles, which are fitted to the jacket using the so-called pile sleeves. The connection between the anchor piles and the jacket is established by means of grouting or casting the anchor pile in place by using high-tension concrete. Due to the size of the foundations, the wind farm owner should consider whether it will be possible for the manufacturer to deliver directly at the offshore position, which can prove to be more cost-effective for the owner.