A wind turbine transmission system is described wherein mechanical power directly from the slow rotation of the shaft of a large wind turbine rotor is carried over to electrical power through a synchronous generator via the circulation of a high pressure gas running in a closed circuit. In the most straightforward mode of operation, power is injected into the gas circuit via special low-speed nearly-adiabatic compressors with very high isentropic efficiency and is extracted using an expander that is also nearly-adiabatic with relatively high isentropic efficiency. In other operating modes, it is possible to exploit the temperature changes arising naturally from adiabatic compression or expansion of gas so as to put energy into storage or recover energy from storage. This paper explores some of the design rationale behind such a power transmission system and uses exergy analysis to explain and evaluate its operation.
Garvey, S. D., Pimm, A. J., Buck, J. A., Woolhead, S., Liew, K. W., Kantharaj, B., …Brewster, B. D. (2015). Analysis of a wind turbine power transmission system with intrinsic energy storage capability. Wind Engineering, 39(2), 149-173. https://doi.org/10.1260/0309-524X.39.2.149