MIT team tests turbine controls in pressurized wind tunnel, with field gains still unproven

An MIT research team says pressurized wind tunnel experiments show that a turbine’s best rotation speed changes when the wind meets it at an angle. The finding could help operators refine turbine controls, but the team’s estimate of tens of thousands of dollars in extra annual revenue per turbine has not been demonstrated at an operating wind farm.

The team used a model turbine 15 centimetres across and increased the air pressure around it to reproduce important features of the airflow experienced by much larger machines. In tests lasting several weeks, researchers varied the turbine’s alignment with the wind and its blade tip speed relative to wind speed. They reported that changing tip speed alone could produce a new maximum in power output when the model was misaligned.

Why alignment changes the calculation

A turbine cannot remain perfectly aligned with a wind direction that keeps changing. According to MIT’s account of the research, many prediction models assume that the rotor faces the wind directly, even though real turbines adjust their angle gradually. The experiments were designed to isolate how power output responds when the wind arrives from another direction and the blades rotate at different speeds.

Lead author John Kurelek, an assistant professor at Queen’s University, described the central result this way in MIT News: ‘The big output of the experiments was clearly showing that new power maximums can be achieved when the turbine becomes misaligned with the wind through only changes to the tip speed.’ That observation suggests a control setting chosen for a well-aligned turbine may leave power untapped after the wind shifts.

What the revenue estimate means

MIT News says the researchers estimate that adjusting turbine alignment, blade pitch and tip speed together could bring tens of thousands of dollars in additional revenue per turbine each year. Blade pitch changes the angle at which air meets the blade. The reported figure is a potential outcome of optimised operation, not money earned during the tunnel tests or a measured annual gain at a commercial site.

The accessible account does not give a verified full-scale trial of this combined strategy. Nor does it establish an annual energy gain or show how the revenue estimate would vary with electricity prices, weather and the equipment at a particular farm. Those questions matter to operators deciding whether a change in controls would deliver a practical benefit.

A separate field precedent

There is field evidence that turbine controls can affect production, though it comes from a different approach. In a 2019 commercial wind farm study led by Paul Fleming, researchers deliberately changed turbine alignment to steer the wake of an upstream machine away from another turbine. They measured about 13% more energy from the downstream turbine over a 10-degree wind-direction sector. That was a result for a limited sector and one downstream turbine, not an annual gain across the farm.

The 2019 researchers said the combined output of the two turbines was in line with their earlier predictions and examined the influence of atmospheric stability. In a separate account of that campaign, the US Department of Energy said simulations suggested wind plant controls might raise annual energy production by 1% to 2%. That estimate concerned wake steering; it cannot be applied to the new tip speed strategy.

Fleming said in the Energy Department account that changing atmospheric conditions affect how well wake steering works and should be included in improved control models. The same real-world variability helps explain the value of controlled experiments and the need for later field testing. A tunnel can reveal the effect of one adjustment at a time, while an operating wind farm must respond to weather that researchers cannot set in advance.

The next test

Howland said the immediate value of the new work lies in improving and validating models used for turbine controls. He also sees pressurized experiments as a faster way to test proposed designs and operating strategies. The study brings a laboratory measurement closer to conditions relevant to large turbines, but operators still need evidence from full-size machines before treating the projected revenue as an achievable return.