Wind farmers may soon be using swarms of drones to solve the headache of downstream wind turbulence and identify the most efficient places to plant wind turbines, thanks to a team of researchers from Switzerland.

On and offshore windfarms seem likely to be part of the mix of future global energy production, but to be sustainable, large-scale multi-megawatt windfarms need to be rendered as economically efficient as possible.

Working out where to place the turbines within a wind farm is currently a major headache for managers and financiers due to a phenomenon known as "the wake effect." As the wind moves through one turbine, the air stream decreases in power, spreads out and creates turbulence (like the wake of a boat). This can decrease the power outputs of downstream turbines by up to 40 percent and cause wear and tear on parts.

The key challenge is to place turbines in locations within an available area that will minimize the impact each turbine has on the other's capacity to produce power. At the same time, the costs of infrastructure such as electrical cables must also be minimized – so turbines need to be spaced as closely as possible within the constraints of the wake effect.

Until now, wind farm managers have had to rely on mathematical formulas, wind tunnel tests and computer modeling to guide the placement of individual wind turbines. But of course, a wind tunnel can't capture the intricate behaviors of wind on an actual plot of land over time.

To achieve maximum efficiency, there's an urgent need for tools that can be used to make precise measurements and create accurate simulations of different wind turbine placements.

View from the field testing in a wind farm of the Swiss team's novel instrumented drone fitted with a suite of sensors. Subramanian, et al.

With this challenge in mind, an interdisciplinary team of hardware and software experts with specialties in aerodynamics, atmospheric flow physics, energy technology and materials science from Swiss Federal Institute of Technology has developed a novel drone with a suite of sensors that can gather precise field data on the complex terrains and airflows in individual windfarms.

The researchers are the first to develop and field test an instrumented drone that can measure, in detail, the airflow near and downwind of a wind farm.

"These measurements shall accelerate the development of simulation tools that can be used to optimize the placement of wind turbines in onshore and offshore wind farms," said lead researcher Dr Ndonga Chokani.

At this stage, the drone works as a seven sensor, fast-response aerodynamic probe that can make time-resolved wind measurements. It is based on measuring technology already used in conventional power plants, which was originally developed at the Swiss Federal Institute of Technology.

Now that the researchers have proved the concept they hope to extend the drones' abilities. Their next step will be to test multiple instrumented drones flying in a swarm to make simultaneous measurements.

The research was discussed at the 69th Annual Meeting of the APS Division of Fluid Dynamics in Portland, Oregon, earlier this week.

Source: American Institute of Physics via AlphaGalileo