Wind Power Generation
Non-mechanical steering of coherent Doppler wind lidar enables 3D wind measurements in a compact package.
Compact 3D Wind Sensing Using Liquid Crystal Polarization Gratings (LCPGs)
Wind sensing coherent Doppler lidar measures distributed wind speeds along multiple lines-of-sight (LOS) to provide a 3D picture of wind fields. This information is critical to monitoring airfields, optimizing wind turbine placement and use, and studying the atmosphere. Most 3D wind sensing platforms use motorized scanners or multiple telescopes to point along different LOS. Alternatively, LCPG beam steering can non-mechanically direct large aperture telescopes to several widely spaced angles with only a few transmissive layers, all while maintaining the low wavefront errors required for efficient coherent Doppler lidar. The low size, weight, and power (SWaP) requirements of LCPG beam steering make it especially suited to nacelle-mounted and spaceborne wind sensor packages.
Many optical sensor technologies bring stringent technical requirements that are challenging for other non-mechanical beam steering technologies. The simplicity of the LCPG steering lets us benefit applications where other technologies fail.
Superior SWaP for Pointing Optical Sensors
There is an increasing interest in integrating 3D atmospheric sensing measurements into small SWaP-constrained platforms, such as wind turbine nacelles, drones, and satellites. For this purpose, eliminating motorized optical systems and redundant telescopes is critical.
Current large angle beam steering methods rely on mechanical components (e.g., gimbals, Risley prism pairs). Large moving optics are bulky, power-hungry, slow, constrained by inertia, and do not provide random access within a scene. The mass and power requirements for mechanical solutions make them impractical for many platforms and limit the sensor area coverage rates. For example, an 8-inch gimbal can typically be > 20 kg and use > 300 W (excluding the control system) to achieve a full-scale deflection time > 400 milliseconds. The equivalent BNS LCPG steering architecture can have a coarse steerer mass of ~0.4 kg using ~0.5 W to provide a full-scale deflection time of < 10 milliseconds. This represents an order of magnitude improvement in weight, two orders of magnitude improvement in performance, and three orders of magnitude improvement in power.