As the world seeks to meet increasingly ambitious net-zero carbon emissions targets, the need for expansion in the offshore wind sector is clear. Energy generation capacity is forecast to increase eightfold, from 29.1 gigawatts (GW) in 2019 to more than 234 GW in 2030, according to the Global Wind Energy Council (GWEC).
Thus far, virtually all offshore wind energy produced globally has come from turbines located in water shallower than 50 m, where the turbine tower can be directly attached to the seabed. But with demand for wind power growing fast – and suitable shallow-water sites filling up in some places – the industry is now seeking to move into deeper water. However, these environments create a new set of challenges for developers.
Existing monopile or gravity designs typically used for shallow-water windfarms, which involve attaching the tower directly to the seabed, are not as simple or cost-effective to deploy in deep water. As seen in other industries, it can be more cost-effective and practical for deep-water wind turbines to be located on floating structures tethered to the seabed, potentially opening up a lot more of the ocean to windfarm developments.
Despite the advantages of using floating platforms, offshore wind developments remain complex, so obtaining the most accurate data on the metocean conditions at proposed sites is crucial. The wind resource may be plentiful, but ocean conditions in deeper water provide a different set of challenges from those in shallow waters close to shore – and they require different tools and expertise to analyze them.
Robust, longer-range ADCPs for deep-water offshore wind energy sites
For Partrac, one of the UK’s leading metocean survey and geoscience consultancy providers, the rising interest in floating offshore windfarms means the company is increasingly being asked to obtain data that developers can use for site characterization and modeling in deeper water than the norm.
ADCPs have long been a crucial part of Partrac’s toolkit for constructing detailed profiles of current and wave movements around windfarms. These instruments provide highly accurate profiles of water movement using the Doppler effect to measure the shift in sound waves reflected from particles at various depths through a water column; crucially they are also able to measure the wave climate.
But moving to deeper water now requires a longer-range ADCP solution.
Partrac deploys the Signature250 long-range ADCP for offshore wind energy studies
The Nortek team has been well placed to help with this shift, having provided ADCPs and expertise to Partrac over many years.
Historically, shallow-water wind farm feasibility studies have been carried out using Nortek’s higher-frequency, shorter-range Signature and AWAC instruments. But collecting data in deeper waters requires equipment designed to withstand, and measure, extreme wave regimes, while accurately measuring currents from surface to near seabed across a greater depth.
With these challenges in mind, Nortek was able to provide Partrac with its Signature250 ADCP and accompanying subsurface buoy. The instrument allows users to measure currents and directional waves up to 200 m for current profiling, and 150 m for wave height and direction, making it the preferred choice for deeper-water wind turbine sites.
“We needed an instrument for deeper water that could still measure both current profiles and the wave climate. The Signature250 has proven to provide exceptional data thus far,” says Pete Wilson, Operations Director at Partrac.
“We also purchased the new Nortek buoy system to house the instrument, and this has proven to be a valuable addition to our fleet of mooring solutions. We needed it quite quickly and Nortek were able to deliver within our time constraints,” he adds.
When deploying with Nortek’s subsurface buoy, users have the option of housing both the instrument and an external battery canister within the same flotation device. This novel solution is a neat, robust and compact approach that simplifies the mooring design and facilitates deployment in a wider range of sea conditions.