For background details regarding this teleconference, and access to other segments, click here.
Presenter: Chip Bullock, HDR
click to enlarge
C-NES lab, north elevation. All images courtesy of HDR Architecture Inc. and the Gilbane Co. |
|
Our project is the Georgia Tech Carbon Neutral Energy Solutions laboratory, also known as C-NES. This is a design-build project with integrated project delivery. We are partnered with Gilbane Building Co.
The project is a 42,000-ft2 research laboratory and is currently under construction, located in Atlanta. The total project budget is approximately $24 million, and programmatically the facility consists of high-bay space, mid-bay (intermediate height) space on the ground level, and offices that that are located on the second floor.
While we are pursuing a LEED Platinum rating, the broader goal for the project from the beginning has been a net zero energy building, or NZEB. Georgia Tech has always placed an emphasis on developing its campus in a way that supports the development of a sustainable campus community by having a distinctive architecture and open spaces. In particular on this project, they wanted to place a very ambitious goal for this project: "carbon neutrality or net zero energy use."
Now, this is an ambitious goal for most building types let alone trying to apply this goal to a laboratory. In terms of the research that is planned for the building, it is actually linked in a very distinctive way to the goal of the project. The interdisciplinary research is energy research, and the building is designed to allow for a variety of research programs that require various scales of space, ranging from large-scale high-bay space to bench-top pilot scale. In fact one of the research groups is looking at how to capture carbon from various fuel streams.
So, as we began to look at this type of research, there was a real paradox in that the building was trying to be energy-neutral, but some of the research itself is very heavy in terms of its energy use. So the challenge for this type of lab building was even greater.
The overarching concept for the project was to approach it as a case study for how future NZEB projects could be developed. The project was intended to express its mission very simply, very directly, and with an honest "no-frills" design approach. We wanted the project to have a clear rational basis to justify everything that we were doing in the building, and each component had to be compatible with the vision and mission of net zero energy use.
click to enlarge
First floor plan. |
|
Through a series of analyses of carbon-neutral buildings, as well as very simple pre-industrial structures and the establishment of the working definition of net zero site energy use, we began our process. Our design-build team created a series of four alternative building concepts, and our process called for these concepts to be critically evaluated through energy modeling to determine which of the four options were the most viable. At the same time we also developed the initial energy savings strategies to pursue in the further development of the project.
Georgia Tech is a very savvy facility owner with a large stake in sustainable design, and we collaborated very closely with them to develop our initial concepts and schematic design. We also developed a rigorous value-management process that resulted in a matrix of energy savings options. This allowed us to evaluate options and look at first cost, life-cycle cost and carbon savings for each element. Our process allowed the entire project team to make very rational decisions about what really made sense for the project and what didn't.
A great example was our evaluation of the use of ground-source heat-exchange. We initially thought that we would need to use ground source for the project; however, we used the energy model to also evaluate the use of a very high efficiency, magnetic-bearing chiller. In the end, when looking at the cost and energy savings, the ground-source system came with a premium of $500,000 with an energy savings that was slightly less that the magnetic-bearing chiller system. In the end we opted to go with the chiller.
So using this method, we could evaluate a broad array of options and narrow the field down to the options that were the best for energy savings, cost, facility management, and long-term operations and maintenance.
click to enlarge
Second floor plan. |
|
To reach our goal of being a NZEB, we first chose initially to drive our energy demand to as low a state as possible by tuning the building passively to conserve energy. The goal was to start from the standpoint of being successfully structured to use less energy. We placed the high-bay space on the north and wrapped it with a translucent skin to take advantage of north diffuse light. We thought that by doing this we could reduce the need for artificial daylight during the day, and after evaluating this through daylight modeling we've been able to achieve that goal.
We also evaluated the space program. And we challenged the Georgia Tech facility staff to look at alternative temperature and humidity ranges that would be assigned based on space type. So the high-bay, mid-bay, and offices each have their own set-points, which allowed us to tailor systems based on specific space types and function instead of a one-size-fits-all approach and trying to accommodate every worst case. We also opted early on to carve a continuous north-facing clerestory between the high-bay block and mid-bay/office block to bring natural light into the middle of the building.
Within the other more functional laboratory spaces and offices, we've incorporated a daylight control system, which allows us to minimize the need for artificial light during the day as well as meet the light levels required for functional needs. We have also adopted the strategy of providing LED task lighting to minimize the need for higher uniform lighting levels throughout the office spaces.
When considering high-performance buildings, two key things are important from the start. One is orientation and the other is the building envelope. At the beginning we looked at several factors related to the location of the program pieces on the site and how things like site access affected our ability to passively tune the building. In the end we were very prescriptive about needing to have a true long east-west orientation, and we've reduced the amount of glazing on the east and west facades by placing enclosed spaces along those edges.
We are utilizing a cool roof and a very well-insulated metal panel system along with high-performance curtain-wall on the north and south facades. Additionally, the south exterior skin is combined with crystalline PV panels that are used in a rain-screen application.
In terms of the other sustainable design strategies, we've incorporated the use of solar energy which will be provided by a total array size of 293 kWs (about 21,000 ft2).This system consists of PVs on the building rooftop, the southern façade, a canopy that runs along the south facade and a covered parking array. This has allowed us to get the most possible output out of what is otherwise a very constrained urban site.
click to enlarge
Building components for sustainability. |
|
To further minimize demands on the building, we've been able to optimize the cooling system in the project by using rainwater collection. This provides the source for process cooling water as well as recharge water for the chilled water cooling towers. This water will also be used for all non-potable water needs including a grey water system for flushing the toilets. To get there, we've got a 20,000-gal rainwater harvesting system, which captures all the rainwater from the roof.
So, as a team we challenged everyone to think outside of the status quo approach. This allowed us to change the way the HVAC was configured and to choose alternatives like naturally ventilating the high-bay space while including all the requirements for safety. By doing this, a completely different energy-reducing solution was possible. Additionally, in the high-bay we are using two large circulating fans to help introduce air movement in lieu of conditioning the space, and we are also using radiant slab heating in the high-bay for the winter months. As far as the mid-bay lab spaces are concerned, the exhaust rates were evaluated and were lowered to the minimum requirements, and we also settled on limiting the number of fume hoods to three at start up and 12 at the full build-out. Georgia Tech has been a very supportive partner in helping to balance the anticipated program growth with the vision and goals of this project to make this possible.
In the offices, we are using an under-floor air distribution system as well as a general displacement ventilation strategy of recirculating warm air back down to the under-floor during cold months.
With respect to building controls, everything in the building is being monitored, including airflows, water flows, temperature and power-comparison assumption. In addition to the ability to monitor the building, the outputs will be collected and studied by Georgia Tech’s building research community.
With respect to achieving our goal of net zero site energy use for the project, right now we are tracking at 370,000 kWh of annual PV output, so we're just short of being net zero by about 30 kWh/yr. We are currently at a 91% reduction in the total buildings energy use.
Ellen Sisle, KlingStubbins: What technology specifically did you use at the fume hoods themselves besides just limiting the number of them?
Bullock: The strategy is for using low-flow variable air volume fume hoods. The control and monitoring strategy is to use VAV controls with modular centrifugal high-plume exhaust fans that are on variable frequency drives and are capable of ramping up or down. Also, we have only installed the exhaust capacity that is needed at the present time. So until the time program growth generates the need for more hoods, we have no more and no less than justified.
Due to the funding source the following statement is provided as required by the US Government's American Recovery and Rehabilitation Act: The project and effort depicted is sponsored by the Dept. of Commerce under the grant from the National Institute of Standards and Technology. The content of the publication/presentation does not necessarily reflect the position or the policy of the US government, and no official endorsement should be inferred.
