Energy
Solar Energy
There are solar panels in the Bullitt’s array, which spreads out like the canopy of a tree to capture solar power for the building. The 14,000 square foot array, comprised of 575 individual panels, is fastened to a steel substructure that parallels the western slope of the site. The building receives its energy from photovoltaic solar panels, which can produce around 230,000 kilowatt-hours a year, and supply its needs for heating, cooling, and electricity (Nelson 2013).
Normally panels are set to face south, at the angle of the latitude so that they can collect sun in the winter. However, the designers realized that in Seattle, most of the sun is received in the summer, and the shallow-angled winter sun would not provide much benefit behind the blanket of clouds. The decision was made to optimize for summer, using the electrical grid as a battery to store power in the summer, and draw power from in the winter. In order to “store” the summer’s surplus, the Bullitt Center uses Seattle’s electrical grid, pushing electricity onto the grid in the summer months when production is high. The building then takes electricity from the grid in the winter months when production is low. To achieve its “net zero energy” goal, the summer production surplus must meet or exceed the winter production deficit.
The Bullitt Center is projected to use almost 70% less energy than a new building that meets Seattle’s rigorous energy code. A typical office building operates at 92 EUI. If the Bullitt Center had an EUI of 92, it would have needed an 82,000-square foot solar array on the roof to generate all its energy from the sun. Instead, with the integration of energy saving systems, such as passive ventilation, ground source heating, and natural daylighting, along with the help of tenant energy budgets, the Bullitt Center will be able to operate at an EUI of 16. With such a small EUI, the 14,000 square foot rooftop array is able to provide for all the electrical needs of the building.
The scale change of PV array
Triple-glazed Windows & Automated Blinds
Energy saving features rely heavily on daylighting, including triple-glazed windows and passive climate controls. The windows and shading systems do the bulk of the work for the daylighting and ventilation, as well as assisting in the thermal comfort of the building. Integrated system of triple-pane glazing and deployable exterior shades helps maintain interior temperatures. Operable windows move straight out to maximize ventilation.
The outermost layer of the skin is the deployable stainless steel shades. Designed by Warema, the system sits about 12 inches away from the windows. In the summer, when solar heat gain can be a challenge, the shades deploy to scatter direct rays before they hit the glass. In the winter, the shades are designed to maximize natural daylight in the office spaces, while still protecting against direct glare on workstations.
Each window unit weighs 168 pounds and is specifically designed to eliminate thermal bridging between the interior and exterior. Two inches and three panes of glass keep the hot air out and cool air in during the hot summer days, and the cold air out and warm air in during the cold winter days. When the conditions are right, these windows can push straight out, drawing in air from all sides around the window pane.
Window and shading systems
Integrated Energy Use
Below is the comparison of energy consumption by typical building and Bullitt Center. We can see that the Bullitt Center uses almost 75% less energy than a typical building. Among it, the tenant contribute to 10% energy saving. The largest energy-consumption item is Misc, which occupied 13%.
The figure below shows the path to net zero energy of Bullitt Center, the energy-saving on heating and cooling shows the largest contribution on the path, the cooperation of tenant is also a significant factor in achieving the aim of net zero energy.
After analyzing the energy features in Bullitt Center, we can know that the PV panels, underground heat pump system, triple-glazed windows, automated blinds and the efforts of tenant are integrated to achieve the goal of net zero energy.
Comparison of energy consumption
The path to net zero energy