* nothing obvious at https://www.nationalgrideso.com/news * minutes from a 2011 meeting suggest that ESO was talking to Beacon Power at the time: https://www.nationalgrideso.com/sites/eso/files/documents/18... * http://credenceturbine.com/business/flywheel-energy-storage-... mentions Beacon Power providing a frequency regulation flywheel in 2014 for a 20 MW plant * "Techno-Economic Assessment of Energy Storage Technologies for Inertia Response and Frequency Support from Wind Farms" 2020 July 02, https://www.mdpi.com/1996-1073/13/13/3421/pdf discusses some details