Offshore wind power: Keeping costs in check

The reduction of costs in offshore wind is making more and more projects viable

By Alok Kumar
Published: Monday 25 November 2019
Photo: Getty Images

The cost of offshore wind power has historically been higher than that of onshore wind generation, but costs have been decreasing rapidly in recent years. The investment cost in Europe has fallen from €4.41 million/MW in 2013 to €2.45 million/MW in 2018. 

The designs of offshore wind turbines are more technically challenging as it faces both hydrodynamic and aerodynamic loads. Mainly the foundations, electrical infrastructure and installations are more technically tedious than that of onshore wind. Foundation design and its construction play a major role in the working of an offshore wind farm and the foundation’s cost component could be up to 40 per cent of total cost.

However, there has been a lot of focus on turbine design in the recent years. DNV GL is currently involved in concept design of a 20 MW turbine model. We find that laws of physics remain same even though the size increases, and hence there is no technical barrier in continuously increasing the size and capacity of wind turbine model. However, there will be potentially an upper limit, largely dictated by logistics in terms of manufacturing, shipping and installation. 

It is likely that the additional cost at some point will not be fully compensated by gain in the additional resources due to extra height and large rotor areas. Historically, two bladed turbines fell out of favour mainly for onshore applications as they are slightly less efficient than three-blade machines, and need to rotate faster to realise peak efficiency. They also experience relatively higher fluctuating dynamic loading than that of three blade designs. However, two bladed turbine designs are now being reconsidered as they will reduce overall cost and time across the manufacturing, transportation and installation stages. 

Besides turbine size and foundation design, there are other innovation areas for offshore wind. For example, LiDAR as an offshore wind measurement tool has seen significant research and development in recent times. We know that meteorological mast measurements for offshore are very expensive, and with more advancement in LiDAR technology, it is being more widely accepted as bankable data for wind resource assessment. 

The other area of innovation is direct drive technology and medium speed gearboxes. A way to reduce maintenance cost for offshore wind is to eliminate high moving parts. The other areas of innovation are high temperature superconductor generator and magnetic gearbox. Because of physical isolation between the input and output shafts, magnetic gearbox has advantages, namely: minimum acoustic noise, free from maintenance, improved reliability, precise peak torque transmission and inherent overload protection.

The author is country manager India, Advisory at DNV GL–Energy

This was first published in Down To Earth's print edition dated 1-15 November, 2019

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