Seattle City Light's new Denny Substation is, in the utility's own words, "not your typical substation.” It is unusual both in its design and its location, which is in the middle of Seattle’s historic Cascade neighborhood.
The design represents two years of work by City Light and its design team, and reflects the input of area stakeholders and the guidance of the Seattle Design Commission. While the substation meets the functional power needs of supporting and serving the expansion and growth of the area, it is also an environmentally-friendly, visually appealing and neighborhood-conducive asset.
While the majority of the site is utilized for substation operations, the design reflects community priorities, such as scenic open spaces and sustainability. The project includes over 44,000 square feet of open space, on-site solar power, a heat recovery system that provides 100 percent of the required heating for many facilities within the substation and a number of other sustainability features.
The substation features sloped enclosure walls that decrease the size of the facility at the pedestrian level, creating a friendlier urban environment along the perimeter, and the walls include metal cladding and translucent glass panels that emit a soft glow at night.
In addition, as part of the terracing, an elevated pedestrian walkway wraps the edge of the substation. This elevated zone is fully accessible, with gentle slopes to allow for views into the substation as well as the surrounding cityscape. The substation itself is open in its design, in that it has no roof. However, most of the substation equipment is hidden from public view within buildings.
Other features of the substation grounds include open public spaces, an off-leash dog area, an event zone, and a community space for events, meetings, and lectures, including art displays.
The substation itself includes:
- four bays of 115kV gas insulated switchgear (GIS)
- three 115-13.8kV power transformers
- one 115kV line reactor with integrated GIS
- one 13.8kV switchgear building
- two 13.8kV capacitor banks
- three 13.8kV grounding banks
- connecting cables