Page 65 - Energize January 2022

TECHNICAL

already higher than the global weighted average in 2010.
A lower range of capacity factors in China can be explained by Chinese
projects being located closer to shore, in shallow waters and with lower wind
speeds, using smaller turbines. This resulted in a 33% capacity factor in China,
compared to 44%, 50% and 52% capacity factors in Germany, Denmark and the
UK, respectively. Ongoing RD&D activities drove the improvements in turbine
ratings, hub heights and rotor diameters that directly helped to increase capacity
factors through energy output. In 2019, the global weighted average of a deployed
turbine was around 6 MW, which doubled from 3,1 MW in 2010.
An increase in wind turbine size increases their cost competitiveness,
resulting in fewer (and more efficient) turbines, which in turn would require
fewer maintenance visits and improvements in health and safety, reduced
installed and O&M costs, and have a positive impact on the environment.
Turbines deployed in 2019 had sizes between 3 MW and 8,4 MW, while turbines
deployed in 2010 had sizes between 2 MW and 5 MW. In 2019, the smallest wind
turbine, at 3 MW, was built 1,5 km from the shore in water 18 m deep, while the
largest turbine, at 8,4 MW, was built 98 km from the shore in water 40 m deep.
Compared to that, in 2010, the smallest wind turbine, at 2 MW, was built 8,5 km
from shore in water 4 m deep, while the largest turbine, at 5 MW, was built 56
km from shore in water 30 m deep.
To reach the strongest and most consistent wind, RD&D activities have
driven wind farms farther from shore and into deep waters. Most new offshore
wind farms after that were built in waters between 11 m and 40 m deep, with
the number of farms growing from six in 2010 to 24 in 2019. In the latter year,
offshore wind farms were built as far as 145 km from shore and in water as
deep as 40 m. In 2010, offshore wind farms were built much closer to shore,
at a maximum of 56 km out, but in water as deep as 37 m, which is almost the
same water depth as in 2019. A technical potential of over 13 TW can be reached
in waters beyond 50 m, with an economically attractive option being floating
offshore wind (ESMAP, 2019; IRENA, 2019).
This can unlock potential in countries with large seabed drops, allowing farms
to be located at a greatly increased distance from shore (e.g., in Japan, China, the
USA and Europe). Capacity factor improvements have in large part been driven by
RD&D activities contributing to improvements in technology. Examples of this are
in the hub height and rotor diameter of offshore wind turbines. Rotor diameters
experienced a 40% increase in the ten years from 2010 to 2019, growing from 112
m to 157 m in size, while hub height grew by 30%, from 83 m in height in 2010
to 108 m in 2019. In line with growing turbine dimensions, wind farms also kept
growing, with an increase from 83 MW recorded in 2011 to 254,5 MW in 2017.
The past ten years also saw an increase in RD&D activities in the design of
the foundations deployed at different depths of water. The designs used the most
were: monopile; jacket; a combination of monopile and jacket; gravity; and an
emergence of new foundation designs, such as multiple, suction bucket, tripile/
tripod (referred to in Figure 3 as ‘others’, as there were fewer projects of these
types). Monopile foundations are simple, well proven and dominated installed
capacity in waters between 20 m and 40 m, for which they are most suited. Jacket
foundations dominated water depths beyond 40 m, as they are particularly suited
for deep water and/or high waves. Gravity foundations saw a boom in shallow
water in 2010, 2013 and again 2016. In 2017, their deployment was seen in water
10 m to 20 m deep, while in 2018, it was seen in water 20 m to 30 m deep.

This is an edited extract from Irena’s report: “Tracking the impacts of innovation –
offshore wind as a case study” Click here to download the full report
Figure 3: Share of installed capacity and water depth by
Send your comments to rogerl@nowmedia.co.za foundation type (2010-2019)

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