“From the outset, our client was determined that its new home be as sustainable as possible, so we knew the Exploratorium would be a perfect match with our own corporate commitment to green values,” says Project Manager Joseph Wenisch, who then adds that other factors have also spurred Integral’s enthusiasm for the project.
“While it is exciting and gratifying to work on a project that will leave a huge and lasting mark on the entire Bay area, the Exploratorium is also a very cool institution that occupies a prominent place in the cultural and educational life of San Francisco,” he continues, noting that the museum draws 500,000 visitors annually and another 26 million to its website. Attendance at the new site is estimated to exceed one million.
The Exploratorium’s current home at the Palace of Fine Arts in San Francisco’s Marina District was erected nearly a century ago for the 1915 Panama-Pacific International Exposition. “No heating, no air conditioning, no ventilation, poor lighting,” Wenisch marvels. “Yet they still have managed to build a very successful space that has revolutionized museums around the world. Their signature participatory exhibits can be found in 80 percent of the world’s science centers.
“But they’ve outgrown it, and are now in a position to address the building issues they have struggled with for decades.”
At the heart of San Francisco’s waterfront, the newly renovated facility at Pier 15 offers a compelling contrast in terms of breathtaking vistas, visitor amenities and an impressive assortment of architectural and engineering innovations. Built 1931 and vacant for a number of years, the more than 800-foot-long pier has undergone a gut renovation, including major structural repairs to its pilings to make it earthquake-safe for the next century.
Completed at the end of 2012, the massive construction project will yield approximately 330,000 square feet (sf) of indoor and outdoor space. A new mezzanine level will house classrooms, conference areas and offices. The finishing touch is an all-glass observatory that anchors the back of the new complex at the end of the pier’s 800-foot projection into the bay.
All these upgrades and alterations were done within strict historical-preservation guidelines with the idea of returning the building to its original look. As a consequence, certain architectural aspects, such as the façade and many of the windows, could be repaired and cleaned but otherwise left unchanged. Some alterations, such as the addition of solar panels to the roof, won approval. Others, such as insulating the walls to prevent heat loss or gain, were disallowed. “Historical preservation was a factor in virtually every design decision we made,” says Wenisch.
When the Exploratorium becomes fully operational in the spring of 2013, its goal is to become the largest net-zero energy museum in the United States, if not the world. True to the spirit of the Exploratorium — and the nature of net zero — achieving such an ambitious degree of energy efficiency will require monitoring and tinkering over time. The entire undertaking will be a real-time education exhibit, with live energy use and photovoltaic (PV) production on public display.
Defining 'net-zero energy'
The new Exploratorium will generate as much electrical power through its rooftop array of photovoltaic solar panels as it would have purchased from the local electric utility in one year. The panels will not generate electricity at night, of course, but they will generate excess electricity during the day—enough to offset usage at night.
The building may need to buy more electricity than it can produce during the winter months when there’s less sun. But this imbalance will be offset during summer months when the Exploratorium will sell excess electrical energy to the grid.
“This project combines an effort to both innovate and think critically about the impact science can have on the world,” says Exploratorium Executive Director Dennis Bartels, Ph.D. “Our net-zero goal is, in part, a way to reduce our global footprint and help improve the community we’ve been a part of for more than 40 years. Net zero is a process—and an opportunity for the public to learn with us.”
Targeting LEED Gold certification, the new Exploratorium will have many notable green features, including:
- — Solar power: The building’s entire annual electrical consumption will be fully offset by a 1.3 megawatt-AC, PV solar-panel system erected on the rooftop of the Pier 15 structure.
- — Bay water radiant cooling system: Even without the photovoltaics, the renovated facility is projected to be 57 percent more efficient than the ASHRAE 90.1 baseline standard for a typical U.S. museum, thanks in part to its innovative use of water from the San Francisco Bay. Depending on the season, the latter will function as either a heat sink or a heat source for a radiant heating and cooling system that covers approximately 90 percent of the floor space.
The job of raising or lowering the temperature of that bay water to meet comfort demand will be handled by eight, 50-ton water-to-water heat pumps. These electric chilled heaters feed a four-pipe system that carries either hot or chilled water to a 200,000-foot network of crosslinked polyethylene (PEX) tubing. The tubing is embedded in concrete slabs on two levels and spanning 82 different heating-cooling zones. Each zone has a control valve and a thermostat to switch between heating and cooling.
No other type of water-heating equipment is used in the building, nor is there any use of fossil fuels except for highly limited cooking purposes in a small restaurant—thus, the net-zero carbon designation.
“We did not wish to sacrifice comfort for energy savings on this project, and radiant is a premium comfort system,” says Wenisch. In addition, almost half of the Exploratorium is open exhibit space with 30- to 40-foot-high ceilings. “Radiant allows us to heat and cool at the floor level where the people are, rather than attempting to condition such a large volume of air in those high-ceiling rooms,” he says.
- — Dedicated OA system: Integral engineers did not eliminate forced air altogether, but created a dedicated outdoor air (OA) system for displacement ventilation that exceeds ASHRAE requirements by 30 percent. By creating separate systems—radiant for heating and cooling and an OA system for natural ventilation—they were able to specify ductwork half the size it would have been in an all-air variable air volume (VAV) system.
- — Multifaceted water savings: The Exploratorium is committed to saving water as well as energy, with a goal of cutting annual consumption of the former by up to 60 percent. Waterless urinals and dual-flush toilets are projected to save an estimated one million gallons annually. Meanwhile, the use of bay water for the heating and cooling system should save an additional two million gallons by eliminating the need for conventional cooling towers to absorb heat during the cooling process. Cooling towers inevitably entail losing large quantities of potable water through evaporation.
Anticipated LEED Rating:
Outside Dew Point:
Radiant System Installer:
A third major contributor to water savings is a rainwater recapture system covering roughly a third of the roof area, despite all the real estate occupied by the PV system. The rainwater is routed from the roof to underneath the pier and into a large “storage tank” that is actually part of the building’s structure. “A pile cap beneath the pier, constructed to resist earthquakes, contains a large cavity where the rainwater is stored until it is needed to flush toilets,” says Wenisch, who estimates that the recapture system will save roughly 300,000 gallons of water annually.
How the System Works
Bay water will be continuously pumped in and out of the building. First, it moves through low-pressure microscreen drum filters to sift particles larger than 30 microns. Then it circulates through an ultraviolet-ray sterilizer that keeps the system free from plant growth.
The filtered water is then transferred to a 4,000-gallon concrete tank beneath the pier before moving to a pair of titanium heat exchangers. Each exchanger is designed to handle half the load during normal operations and two thirds during maintenance periods. Depending on the need for heating or chilled water, the bay water exchanges heat with the “condenser water” circulating on the opposite side of the titanium units. Variable-speed pumps then move the condenser water to the eight Multistack chiller heaters and to the 82-zone, PEX tubing network embedded in the floors throughout the building.
The bay water never moves beyond the heat exchangers. That’s because salt water would corrode the heat pumps and other mechanical components in just a few months. Once the heat exchange process is complete, the bay water returns to its source—completely unchanged and with no chemical treatment, as stipulated by the local permitting authorities. All of the above is accomplished in a single space inside Pier 15, called the Bay Water Mechanical Room, whose operations will be available for viewing by museum visitors.
The system operates differently at various times of the year, based on the comfort needs of the building and the temperature of the bay water.
In the colder months, when space heating is needed, the bay functions as a heat source. The eight heat pumps use the 50 F bay water to heat the hot-water return from 90 F to 100 F before it returns to the PEX tubing network. A valve at each of the 82 manifolds automatically controls flow into a zone, depending upon the ambient temperature of the space.
In the warmer months, when cooling is required, the bay serves as a heat sink. Now functioning as chillers, the heat pumps lowerthe temperature of the water—from around 65 F to the 60 F required for cooling—before it circulates to the 82 cooling zones.
—Free waterside economizer months:
When the temperature of the bay water is below the building chilled-water return temperature, the system operates in what Integral calls its “waterside economizer mode,” explains Wenisch. “For roughly six to eight months a year, the bay water is around the optimum cooling temperature. That allows us to cool the building chilled-water loop, either partially or fully, bypassing the heat pumps.”
Integral expects that the waterside economizer mode will yield the bulk of the cooling system energy savings by keeping the heat pump chillers idle. “In San Francisco, we are very fortunate in that we have very few days over 80 degrees,” Wenisch notes. But even when the heat pumps are operational, “the chiller plant runs more efficiently because we designed the building to use a higher water temperature.”
Radiant also reduces the amount of energy normally expended to blow air. “Radiant has a lot of secondary benefits, and in this project we’re trying to take full advantage of all of them to minimize energy consumption,” Wenisch remarks.
The dryness of the San Francisco climate also obviated the need for dehumidification in all but the most heavily trafficked areas, such as the theater and the retail store inside the old pier and, most especially, the Observatory, which houses a cafeteria-style restaurant on the lower level and an exhibition and event space above. These areas are also equipped with radiant slab cooling, but when occupancy rises to several hundred people on a warm day, water-to-air heat pumps will activate to dehumidify the spaces.
“The radiant system is designed to operate on 55-degree chilled water, which is not likely cold enough to handle peak loads, especially when 500 people are gathered in the restaurant or the event room,” says Wenisch. “Rather than lower the system temperature, we opted for the water-source heat pumps. But radiant allowed us to use heat pumps one or two sizes smaller than they would have been if they were handling the spaces themselves.”
Success the Second Time Around:
|Exploratorium: Projected Energy Use Breakdown
Measure: Annual Annual Electricity Usage (kWh)10
Source: Integral Group
|ITEM||ASHRAE 90.1 BASELINE||EXPLORATORIUM|
|Lights - Interior||853,143||375,300|
|Lights – Exterior||49,100||49,100|
|Domestic Hot Water||112,154||105,600|
|Process Exhaust Fans||59,439||59,439|
|“Almost all of our savings over the ASHRAE baseline at the new Exploratorium will be derived from interior lighting and space heating and cooling,” says project manager Joseph Wenisch. See red-highlighted numbers in the above chart.|
The new Exploratorium is distinctive and even unique in many ways. But it is not the only renovated pier on The Embarca-dero to employ radiant slab heating and cooling. Nor is it the first to attempt to save water and energy by using bay water with such a system.
Completed in 2001, the renovation of Pier 1 also employed these cutting-edge technologies. Unfortunately, while the building’s heating and cooling systems have continued to function properly, there were problems with the use of bay water at the outset.
“They ended up replacing the bay water system with a cooling tower,” says Wenisch, who also acknowledges that the Pier 1 situation “had an impact on the planning of the Pier 15 renovation a decade later. We had to fight through the negatives associated with that earlier project.”
But Integral believes that the bay water-driven radiant slab system at Pier 15 will avoid the problems of its counterpart a half-mile away down The Embarca-dero, on its way to becoming “a great and long-lasting example of how to do green design.”
Uponor Inc.is a leading supplier of plumbing, fire safety, and radiant heating and cooling systems for the residential and commercial building markets in the United States. Uponor, Inc. employs 380 people at its North American headquarters in Apple Valley, Minn. For more information, visit www.uponor-usa.com or call (800) 321-4739.
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