by Emil Morhardt
If your wind turbine isn’t going fast enough to meet the demands of the grid, blow on it a little harder: that’s the general idea suggested by Sun et al. (2014) [Shouldn’t somebody named Sun be studying solar rather than wind power?] The concept is a little like a hybrid electric vehicle; if the internal combustion engine isn’t going fast enough, give it a little boost from the electric motor connected to it. Except in this case, it’s that if the wind turbine isn’t going fast enough, goose it with a little compressed air. You might be envisioning a compressed air nozzle pointed at the turbine blades, but there’s a better way: use a motor driven by compressed air to speed up the turbine. One novel aspect to this study is that the device envisioned as a compressed-air motor is something called a scroll expander, or scroll-type air motor, a new type of pneumatic drive, but that doesn’t seem to be central to the idea—any suitable air-driven motor should work. The main point is to have it integrated with the wind turbine so that when needed, it can help out in the short term.
To function, it needs a source of compressed air, but where that might come from isn’t dealt with in the paper. It could be generated by the same wind turbine using excess electricity to run an air compressor, but maybe there are other sources as well, and I think the authors envision a centralized source of it—rather than one compressor per wind turbine, one compressor per field of turbines, all connected with air hoses. The authors created a test rig in the lab that simulated all aspect of the system, and conclude that 55% of the energy used to compress the air could be expected to be returned from the boosted wind turbine, which is fairly good for pneumatic motors, and the wind turbine itself was much better at providing steady reliable power with the compressed air device than without. The photo above has nothing to do with this study, but it looks terrific anyway, so I linked to it.
Sun, H., Luo, X., Wang, J., 2014. Feasibility study of a hybrid wind turbine system–Integration with compressed air energy storage. Applied Energy DOI: 10.1016/j.apenergy.2014.06.083.