Taller wind turbines drive growth but raise reliability risks, experts warn

Advances in wind power technology will open up new project opportunities but operators must tackle growing size and site climate challenges to minimize costs, North American wind experts said at the Wind O&M Canada 2018 conference.

In North America and Europe, wind power developers face increasing cost pressure following the removal of subsidies. Wind suppliers have responded by developing larger, higher efficiency turbines to create new market openings.

Last month, GE unveiled a new 5.3 MW onshore wind turbine which is more than double the average capacity of turbines installed in the U.S. in 2017. The turbine incorporates 77-meter blades and hub heights of up to 160 m.

Taller turbines can access higher wind streams and system innovations have improved energy conversion. Set for commercial launch in 2019, GE's 5.3 MW design increases annual energy production (AEP) by up to 50% compared with GE's 3 MW turbines, according to the company. The turbine also incorporates a two-piece blade design for on-site assembly, improving transportability and access to site.

Onshore turbine dimensions will continue to grow in the coming years and hub heights and rotor lengths could hit 200 m in the near future, Ken Young, Chief Operating Officer of Apex Clean Energy, a major renewable energy developer, told the conference on November 12.

"I'm excited about where the technology is enabling the business to go. We are developing projects in places that we never could have conceived of 10 or 12 years ago," he said.

          US wind development sites in 2017

                              (Click image to enlarge)

Source: National Renewable Energy Laboratory (NREL)


Extended in 2016, the U.S. 10-year wind Production Tax Credit (PTC) falls by 20% per year to provide $13.8/MWh [60%] for projects started in 2018.

Technology improvements will outweigh PTC reductions to present further wind project opportunities in the coming years, Young said.

"We see that outside of a few very tight projects, we can make it work…The 80% PTC is a winner and we continue to drive on. We've already looked at 2022 delivery for 60% PTC-- those projects also work in certain cases," he said.

Operations challenge

The continuing drive towards lower wind capex costs could reduce long-term operational reliability, creating new challenges for operations and maintenance (O&M) teams, experts told the conference.

"We are cutting into the design margins, we are putting up equipment that is less costly but that could potentially have a longer term impact for those of us in operations," Ian MacRobbie, Vice President- Operations at Liberty Power, the renewable energy subsidiary of Algonquin Power & Utilities, said.

                                 Average US wind O&M costs 2000-2017

                                                                 (Click image to enlarge)

Source: Lawrence Berkeley lab's Wind Technologies Report, August 2018. 

Maximizing lifespans is key to reducing the levelized cost of energy (LCOE) and many operators are already making major component decisions to extend the lifespans of operational assets.

Larger towers and rotors will impact major components, experts warned.

Increased stress on generators "requires more vigilance and more competence in our core skills," Young said.

Site conditions are also generally more demanding than those that in the past, offering lower wind levels-- requiring a larger rotor-- or higher levels of turbulence and wind shear, MacRobbie noted.

"We are starting to see the impact of that on the equipment," he said.

Proactive measures are required to mitigate higher levels of leading-edge erosion, MacRobbie noted.

"Tip speeds, those environments that we are putting them in...I think a lot of people are seeing elevated levels," he said.

Shorter stops

Rising turbine capacities have increased the importance of minimizing downtimes and suppliers are continuing to adapt designs to aid operational efficiency.

GE's latest turbine incorporates more robust manufacturing processes, includes a larger nacelle platform to facilitate up-tower repairs, and accommodates the latest data analytics and predictive maintenance systems.

New logistics solutions are also being developed. Dutch firm Mammoet has developed a crane for onshore wind farms which uses the turbine’s tower as a point of support to lift and lower heavy components. The crane has a capacity of 250 metric tons and the maximum lifting height of the crane is "virtually limitless," according to the company.

Vestas and Maersk Supply Service, a major marine and logistics group, are also jointly developing a Vertical Installer wind turbine crane. The companies are developing associated lifting tools and handshaking solutions for onshore and offshore applications.

"The amount of capex in the total solution is significantly lower than existing methodology requires," Niels Neergaard, project lead for Vertical Installer at Maersk Supply Service, told New Energy Update in September.

Joint effort

As wind turbine capacities continue to rise, O&M companies will have to adapt and respond rapidly to develop solutions that minimize operational costs.

Despite the challenges, Young remains optimistic about projects going forward.

"It takes efficiency from all of the main cost drivers," Young said.

"If we continue to focus as an operating community, find better angles to increase production, continue to focus on our core business, I think there is a great opportunity for the next five years and beyond,” he said.

New Energy Update