Danbury-based FuelCell Energy is celebrating Earth Day with an achievement of a significant clean power milestone.  Their SureSource technology has delivered more than 12 million megawatt hours globally since its first commercial installation. SureSource plants are currently installed and operating on three continents, with many owned by leading utility companies and educational, commercial, and industrial enterprises. As an example, FuelCell Energy officials say they provide value beyond power to Pfizer, delivering on-site power reliability and steam for its Connecticut research and development campus.