California utility’s HQ building produces renewable energy
Sustainable architecture and engineering meet at the San Francisco Public Utilities Commission (SFPUC) headquarters in San Francisco. The municipal utility provides its customers with water, power and sewer services. The HQ facility, which opened July 2012, has been described as one of the greenest office buildings in the U.S.
Roof-mounted solar arrays and integrated wind turbines on the structure’s high-performance building envelope generate up to seven percent of the building’s energy needs. The sleek 13-story Class A building features high-efficiency mechanical systems, including HVAC technology with Daikin Magnitude chillers, natural ventilation and daylight harvesting.
Inside, shading devices control glare and minimize heat gain. Light shelves reflect daylight into the building. Innovation is also found in the SFPUC building’s grey and black water recycling system that treats the building’s wastewater on-site. The technology is leading-edge for a public agency that provides the city’s retail drinking water, wastewater services and wholesale water for three other Bay Area counties.
“SFPUC’s goal was to be an example for building smart, efficient and sustainable buildings in response to the dwindling natural resources,” says Masoud Vafaei, SFPUC project engineer.
To meet the building’s energy-performance requirements and goal of achieving the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) Platinum certification, the air conditioning system had to satisfy every operating scenario efficiently, especially at part load, which occurs frequently in the mild San Francisco climate.
“There’s always demand for cooling. You have the data center in the lower level and other areas that require cooling every day,” says Ron Yaffe, senior sales engineer at Norman S. Wright Mechanical Equipment Inc., manufacturer’s representative for Daikin Applied.
“An analysis had to be made in non-biased conditions to determine the type of efficiencies each chiller manufacturer could achieve,” says Kreyne Sato, principal engineer at SJ Engineers. SFPUC selected two
Daikin Magnitude chillers at 500- and 250-ton capacities, featuring magnetic bearing oil-less compressors and integral variable frequency drives which yield 40 percent more energy efficiency than standard centrifugal compressor chillers. “In addition to efficiency, the compact footprint, weight and electrical service of the Daikin chillers were factors in their selection,” Sato adds.
“The Magnitude chillers are inherently efficient,” says Alex Brown, senior engineer with SJ Engineers. “We also included other efficiency features, such as a chilled water economizer which allows the chillers (in photo above) to ramp down to their minimum capacity before shut-off.”
The building’s HVAC design is based on a traditional four-pipe system. The assembly also includes two rooftop-cooling towers for the chilled water system, two large variable air volume (VAV) custom air handling units, heat exchangers and an underfloor air-distribution system (also known as a raised floor plenum) that conserves building space and minimizes ductwork.
The system also enables personal control of airflow. If a window is opened, for example, the building automation system shuts off the flow of conditioned air through the underfloor system to the corresponding zone. The underfloor system reduces the building’s operating and maintenance costs, according to the manufacturer.
The building design exceeded ASHRAE 90.1 requirements for energy efficiency for HVAC in new office buildings by 51 percent, according to the manufacturer. The Magnitude chillers support the building’s ongoing energy conservation and are operating smoothly. “The chillers are extremely quiet,” says Mark Lawn, chief engineer for the SFPUC building. “That’s important because the chillers are located in the space directly above the executive offices on the thirteenth floor.”
“It’s very unusual to see a large, high-rise public project like this push the envelope of energy efficiency and sustainability in so many ways. It’s a testament to San Francisco’s level of commitment to protecting our resources, while providing a comfortable and enjoyable work environment,” concludes Mike Rubio, senior vice president at Norman Wright.
The SFPUC building at 525 Golden Gate earned the LEED Platinum certification for new construction in 2013.