It's hammer time

NETHERLANDS: Dutch company Fistuca is about to begin testing a radical new piledriver for offshore monopile foundations that aims to cut noise and installation costs.

(pic: Mark Horn/Fistuca)

The Blue Hammer is designed to install large monopiles for 6MW-plus turbines. Fistuca will start testing it in the port of Rotterdam in September, before driving an offshore monopile in early 2018.

Produced by heavy-construction equipment specialist Huisman, the hammer is a 10-metre wide, 30-metre high pressure vessel that is manoeuvred by a crane over the monopile, which is lowered into the water and held in place by a gripper on the craft. Once the vessel is placed on top of the monopile, water is fed into it.

A combustion cycle created by a gas mixture pushes the column of water into the air, after which it falls back on the pile, delivering a "blow" while creating noise levels 20 decibels below those of conventional hammers.

"In the construction of German wind farms, noise mitigation accounts for 15% of installation costs. This technology is expected to remove that cost completely," says Jasper Winkes, who founded Fistuca in 2008.

The technique can also reduce installation times, and costs, because the pile can be shipped to the site pre-assembled. No stiffeners are needed to reinforce the pile.

Foundations typically account for 20-25% of the cost of constructing an offshore wind farm. "We expect to reduce costs by 10%. No noise mitigation expenditure, no transition pieces required in the monopile, these are just some of the areas where savings can be made."