Speaking at a session on how larger turbines will affect operations and maintenance (O&M) cost and strategies, Smith said 4-5MW turbines would be taller with larger and heavier components, meaning costs to change gearboxes could be up to 70% higher per turbine than the current 2-3MW range.
Generator replacements could also cost up to 53% higher per turbine, Smith added.
However, larger turbines will mean fewer turbines so ultimately the costs across an entire project could go down, panelists agreed.
Neil James, a director of site operations at developer Apex Clean Energy, said fewer turbines means less risk, so the move to larger 4MW-plus onshore turbines should be welcomed in the US.
At the American Wind Energy Association's Windpower 2018 conference, German manufacturer Senvion announced two new 4MW turbine models for the North American market.
Smith also said O&M providers should place greater focus on condition monitoring. "Condition monitoring becomes more important in larger turbines. If one turbines goes down you notice it more," he told delegates.
To help simplify O&M, senior vice president of operations at Pattern Energy Chris Shugart, considered the re-emergence of direct drive turbines as onshore machines grow. "It hasn’t won that argument yet [against geared], but as turbines get bigger then it could come back", he said.
Smith, and E.on vice president of regional operations Gerrud Wallaert, said a lot of O&M strategies and techniques could be learned from the offshore sector.
"We’ve already done large machines so there are lessons to learn," Smith said.
Shugart also said the communication between construction and operating teams is essential.
If a large turbine component needs replacing a few years in to the project’s lifetime, then operating units need to know if any special measures were put in place during construction for the delivery of the component, such as turning areas.
Many developers give land back to the landowner after construction phase to minimise the impact of the project.
Brian Hayes executive vice president of asset operations at EDP Renovaveis, said the developer maintains a strong relationship with landowners, so they can place in turning areas, for example, if the need arises. "You can put a turning area in pretty quickly," Hayes said.
The American Wind Energy Association (AWEA) is holding its Windpower 2018 conference and exhibition in Chicago (7-10 May). Windpower Monthly will bring all of the coverage from the show across the week. www.windpowermonthly.com/awea-2018