I would have parsed the article as saying that the facility could provide 10MW power for about five hours, so with a total capacity of 50MWh... this is terrible

I would have parsed the article as saying that the facility could provide 10MW power for about five hours, so with a total capacity of 50MWh... this is terrible reporting. Hydrostor own website confirms your figures: https://www.hydrostor.ca/goderich-a-caes-facility/ https://www.hydrostor.ca/goderich-a-caes-facility/