Last month, space history was made when the SpaceX Dragon capsule linked up to the International Space Station with its first human passengers. Anyone who has ever attempted to dock the capsule using the SpaceX simulator, which is an exact replica of the interface astronauts use when lining up the capsule to the station’s port, will understand this is no mean feat.
It’s not as simple as driving the capsule forwards, backwards, or turning. There are six degrees of freedom and concepts like ‘up’ and ‘down’ are relative too in space. On the control panel, you can adjust the capsule’s ‘Roll’, or the movement around the front-to-back axis of the spacecraft. ‘Pitch’ addresses rotation around the side-to-side axis of the space craft. And ‘Yaw’ addresses the spacecraft’s rotation around its vertical axis.
These are all concepts that are used in offshore wind turbine controls as well: in this case, the yaw of the wind turbine rotor can be adjusted to the direction of the wind; and the pitch of each blade can be moved to achieve the optimum blade angle for rotor speeds or power output.
For the NASA crew, getting yaw and pitch right is the difference between a successful docking and a crashed spacecraft. For offshore wind engineers, getting it right is crucial to maximising power production without creating excessive stress/loading and ultimately reducing the final electricity price.
The Offshore Renewable Energy (ORE) Catapult is a partner in one of the biggest European research and innovation projects tackling the control of offshore wind turbine yaw and pitch. The project, TotalControl, is a €5 million four-year project funded by the European Union through its Horizon 2020 programme. It brings together leading wind farm operators, equipment manufacturers (OEMs) and academia.
The project is investigating how operators can revolutionise the control of wind turbine yaw and pitch, amongst other factors, allowing them to increase power at a lower cost of production. At present in a typical offshore wind farm, each wind turbine’s control system operates in near total isolation, adjusting its own individual yaw and pitch. TotalControl is one of the first projects looking to enable the entire fleet of turbines to orchestrate their yaw and pitch in harmony with each other, taking into account the effect one turbine’s operation has on the wind flow coming through to another.
To put it simply: each turbine is currently playing its own tune within a wind farm with limited reference to the other players (turbines). The philosophy being introduced by TotalControl is that the turbines should begin to play together as an orchestra.
Paul McKeever, Head of Electrical Research at the Offshore Renewable Energy (ORE) Catapult said:
“The comparison between the challenges of the SpaceX Dragon and controlling a wind turbine/wind farm is an interesting one. If I had to evaluate which is more complex, docking a SpaceX Dragon or getting offshore wind turbines to play in tune, to the extent that we get the absolute maximum power production at the lowest price, that would create a very interesting debate. However, I would certainly welcome a space programme-sized budget to tackle the offshore wind challenge!”
“The TotalControl approach is built upon a hierarchy of controllers, each reacting at different time scales and control time steps. Yaw, pitch and other controls are being designed to adapt at high speed to the wind conditions, effects of turbines on wind flows and the electrical grid demands whilst taking into consideration power production, load and other O&M and market considerations.”
“The TotalControl group of researchers and engineers will present to industry an alternative approach to wind turbine control. It will be the result of four years of hard work researching a number of factors including the wind interactions that turbines create amongst themselves, and developing faster controllers that can respond at high-speed to sudden events like turbulence gusts. The project is working at the cutting edge of our sector by developing high-fidelity computer simulations and undergoing live experiments in fine-tuning fidelity control tools by using operational assets such as our 7MW Levenmouth Demonstration Turbine.”
All this ultimately comes down to how you control each turbine’s yaw and pitch to make the entire orchestra (wind farm) play the right tune for maximum energy, minimum cost. And thus, two feats of engineering precision and beauty – an offshore wind turbine and the SpaceX Dragon capsule – both come down to a super-fine understanding of yaw and pitch.