Implementing heat recovery provides savings opportunities at BC Hydro dam facilities

In 2012, Prism began providing engineering and project management services for the implementation of retrocommissioning recommendations at both the Seven Mile and Kootenay Canal hydro generating stations. The projects were based on the implementation of measures from reports completed by Prism in 2012.

The large generators at these dams produce heat due to mechanical and electrical losses inherent to the system.  This heat must be removed from the generator enclosure, which is often accomplished by circulating reservoir water through cooling coils.  By using the reservoir’s water for cooling, it can no longer be used for generating purposes.  The resulting water and energy losses in the system provided an opportunity for a creative way to save energy.

Dam facilities need large volumes of air to ventilate tunnels and equipment in the power plant building.  The studies for both stations identified ways to capture some of the generator heat loss to be used for space and ventilation air heating.  By pre-heating this ventilation air with waste heat from the generators, less energy is required for the up-front heating process. Installing new dampers, actuators and direct digital controls allowed warm generator air (45°C – 60°C) to be diverted to preheat ventilation air or be routed to specific levels of the powerhouse for space heating.  These solutions provided savings by replacing the use of electric heaters in the powerhouse and saving water in the reservoir to be used for power generation.

Results

From all measures implemented at generating stations:

  • Seven Mile: 684,000 kWh or $60,000
  • Kootenay: 226,000 kWh or $19,800