In 2008, Sandia National Laboratories in New Mexico was awarded LEED-NC (new construction) certification by the U.S. Green Building Council for five major buildings, more than any other entity in the state. Not only do the more than 600,000 square feet in these five buildings represent more than 10 percent of the square footage in the 700 buildings under Sandia's management; these buildings are unlike most LEED-rated buildings.
The MESA Microsystems Fabrication (MicroFab) Facility, for example, is the nation's first microchip fabrication facility to achieve a LEED certification. "For the MicroFab, as for most of the buildings at
Sandia, it's a challenge to use the LEED rating system because the LEED system was designed mostly for commercial type buildings," said Sandia environmental planner Jack Mizner. "Our buildings are pretty complicated, with laboratories and, in the case of the MicroFab, a semiconductor fabrication facility with very unique energy and water uses."
Two of the five LEED-certified buildings are light laboratory/office buildings: The Joint Computational Engineering Laboratory and the Center for Integrated Nanotechnologies. The other three, comprising the Microsystems and Engineering Sciences Applications (MESA) complex -- and the largest consumers of water and energy -- include:
- The MESA MicroFab facility
- The MESA Microsystems Laboratory, with facilities for research and development of microelectromechanical systems (MEMS) components, rapid prototyping and testing of integrated systems
- The MESA Weapons Integration Facility.
Water
These three buildings consume 28 percent of all the water used at Sandia. The biggest single user of water is the MicroFab, which uses up to 200 gallons of water to make a single silicon wafer. The water needs to be ultra-pure. Because the water, which is drawn from an underground aquifer, has a high alkalinity and silicon content, all of the chemicals need to be removed from the water so it becomes an electrically resistant rather than a conductive substance.
The MicroFab had an existing ultra-pure water plant. Instead of building a new one, the existing one was retrofitted to double its capacity and integrate new efficiencies, especially in the reverse osmosis unit (in which feed water from the aquifer is pressurized against a semi-permeable membrane, purifying the usable water of solids and salts and producing wastewater high in solids and salts).
Sandia installed a High Efficiency Reverse Osmosis (HERO) system, increasing the efficiency of the de-ionization system from about 65 percent to 95 percent. HERO uses additional steps before osmosis to do a better job of removing dissolved solids and other contaminants.
Sandia also began recycling water used in the fabrication process and putting it back through the HERO for re-use. "By starting with used pure water, you don't have to treat it as much, and that uses less energy," Mizner said.
If the ultra-pure water plant had been built with normal reverse osmosis, according to Sandia figures, the MicroFab would require 160,000 gallons of feed water annually and would produce 44 million gallons of wastewater. With the HERO system, it requires just 116,000 gallons annually and produces just seven million gallons of wastewater.
Beyond the functional and green benefits of the HERO system, it saves $195,000-$200,000 annually over normal reverse osmosis, Sandia estimates.
"At the same time, we took the wastewater that came out of the process, which was still pretty pure, and used that in our cooling towers," Mizner said. "The result was that we were able to double our capacity for ultra-pure water while drawing the same amount as before from the aquifer."
Further water savings in the new buildings were achieved through measures such as low-flow faucets and toilets and water-efficient landscaping with native plants and drip irrigation.
Energy
MicroFab energy use is higher than that of typical building spaces because of the manufacturing processes. In the "clean rooms," for example, a technology actually invented at Sandia in the 1960s, positive pressure has to be maintained in rooms where sensitive electronics are processed in order to prevent contaminants from entering. That requires an high-enough air flow into a clean room to achieve a couple hundred air turnovers per hour versus perhaps 20 times for HVAC systems in an office building. That air has to be driven through filters on the way in, and the HVAC system must keep the labs within narrow temperature limits. Acidic and caustic vapors from the semiconductor fabrication process have to be removed from existing air by passing through scrubbers.
Sandia tackled the energy challenge not just in the MicroFab but also in the labs and offices of the other four new buildings by means of specifying high-efficiency fans, chillers and pumps; using variable air volume flow; increasing the efficiency of the central HVAC plant; daylighting in the offices and other improvements.
Energy performance was assessed using two eQUEST energy simulation models: one for the MicroFab and one for the same building (the "Budget Building") as it would be if it had been "built to, but not exceeding ASHRAE 90.1-1999, according to the modeling report." ASHRAE 90.1 (90.1-2004 in LEED-NC - Version 2.2) is the standard to meet for LEED energy efficiency points.
The MicroFab was found to use less energy than the Budget Building in most building features.
For fan energy, the building feature with the most impact, the simulation showed the MicroFab as using approximately half the fan energy required by the LEED-standard Budget Building.
Second most important in magnitude of its energy impact was electricity for space cooling. Space cooling in the MicroFab requires just 25 percent of electricity required by the Budget Building. Lighting energy density was noted as having the third greatest energy impact, and the simulation showed annual lighting energy usage in the MicroFab as being just 47 percent of that in the Budget Building.
Such achievements are just a few among many green measures taken at the MicroFab and other LEED-certified buildings at Sandia. One of these is to use outdoor air for cooling instead of having to turn on chillers, especially during the transitional periods of spring and fall, through heat exchangers that draw water from the facility's cooling towers. A campus-wide energy software system manages fan controls and dampers in real time to adjust the contributions of chillers and outside air.
"We changed our specs about 10 years ago to reflect green products," Mizner said. "Carpets that emit less VOCs and concrete with recycled content are a couple of examples of what we specify for every building."
During construction of the new buildings, waste was recycled. And, local materials and materials with recycled content were used where possible. All of Sandia's buildings are metered for electricity and gas. Sandia gathered LEED credits for measures ranging from motion sensors and dimming for building lights and heat recovery on exhaust systems to bicycle storage areas and bus stops near buildings.
Two other building projects at Sandia are now registered in the LEED-NC system, and Sandia plans to LEED-certify one or more buildings each year. By: Robert Ebisch
