Wind Turbines with Large Rotors and Tall Towers Provide Double Dividends

Supersized turbines could reduce costs, enhance value of wind energy—and more

Researchers at the U.S. Department of Energy’s (DOE’s) Lawrence Berkeley National Laboratory (Berkeley Lab) analyzed the impact of large wind turbines on grid-system value and illustrated the importance of expanding wind turbine design to focus not only on minimizing direct costs, but also on a broader set of factors that impact the value of wind to the electricity grid. Findings were published in the journal Wind Engineering.

In recent years, significant increases in wind turbine size—nameplate (or rated) capacity, rotor diameter, and tower height—have been driven primarily by a goal of minimizing the levelized cost of energy (LCOE). Previous research by Berkeley Lab suggests that supersized turbines, featuring even larger rotor swept areas (relative to nameplate capacity) and taller towers, might enable further LCOE reduction of approximately $6 per megawatt-hour (MWh). Other research funded by DOE identifies potential solutions to the logistical challenges associated with deploying supersized turbines. But with wind’s LCOE now comparable to that of other electricity-generating resources, design considerations in addition to cost minimization have grown in importance—particularly as wind penetration increasingly impacts the electricity grid and reduces wind’s marginal value to the grid.

Berkeley Lab’s new research addresses that expanded design need. Results demonstrate a possible double dividend—that larger rotors (relative to nameplate capacity) and taller towers might not only reduce LCOE but also enhance the value of wind energy and provide hidden benefits. These benefits largely come from the increased capacity factors that larger rotors and taller towers enable and the fact that such supersized turbines tend to have more consistent output throughout the year.

Specifically, the analysis leverages recent hourly wholesale pricing patterns and hourly wind profiles for wind power plants located in the seven U.S. wholesale markets (i.e., independent system operators, or ISOs). The study finds that in regions where wind penetration has reached around 20%—such as the Electric Reliability Council of Texas (ERCOT) and the Southwest Power Pool (SPP)—supersized turbines could already boost wholesale energy and capacity value by $2/MWh–$3/MWh, on average, compared with turbines deployed in the recent past (Figure 1). Across all regions, the average value boost is $1/MWh–$2/MWh. For specific power plants, the enhancement is already as much as about $5/MWh.

These wholesale market value benefits are augmented by three additional possible advantages of supersized turbines:

• Reduced transmission expenditure because of greater transmission utilization
• Lower balancing costs for the electricity system as a result of lower aggregate wind output variability
• Lower financing costs resulting from less long-term wind output uncertainty.

The analysis finds that these three benefits roughly total $2/MWh, adding to the $2/MWh–$3/MWh energy and capacity value boost observed in regions with higher wind penetrations.

When Berkeley Lab researchers consider all the benefits, the aggregate benefit averages $4/MWh–$5/MWh in higher wind-penetration areas. Moreover, these possible benefits add to the $6/MWh of potential LCOE advantage of supersized turbines assessed in earlier work, yielding total benefits of about $10/MWh. The degree to which these advantages are ultimately realized, and at what point turbine size plateaus, will be determined by future wholesale price patterns, the success of continued design and materials optimization, social acceptance and regulatory hurdles, and the logistical constraints of transporting and erecting even-larger blades, towers, and nacelle components.

More broadly, this analysis illustrates the growing importance of factors beyond plant-level costs in turbine and project design and operations. As wind penetrations increase, the output profile and characteristics of wind begin to impose challenges to the electricity grid. By expanding the analysis scope to consider supplementary factors that influence the system economics of wind—market value, transmission, balancing, and financing—turbine designers, project developers, and wind research and development experts can help ensure that wind power plants of the future seek a balance between minimizing costs and maximizing value.

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