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Conservation Calibration

A major milestone on UNC's path to climate neutrality by 2050 is the university's plan to employ low-cost fixes that scale back building energy use-which accounted for more than 90 percent of the carbon footprint in 2007.

By Carolyn Elfland and Chris Martin

In its inaugural National Building Competition in 2010, the U.S. Environmental Protection Agency (EPA) recognized Morrison Residence Hall for achieving the greatest overall percentage of energy reduction of any building entered in the competition. The 10-story, 218,000-square-foot building, located on the University of Carolina at Chapel Hill (UNC) campus, was constructed in 1965 and renovated in 2007. The forward-looking facility includes a solar thermal system, more efficient windows, and upgraded lighting. It also sports a touch-screen monitor in the lobby that allows residents to keep track of their energy consumption.

The project and honor (for details, see sidebar,"The Biggest Loser Emerges as a Winner") reflect UNC's commitments to reducing its carbon footprint, with a plan to reach climate neutrality by 2050. For further evidence of widespread attention garnered by UNC's progress toward its proclaimed goal, see also the sidebar,"Recognizing Ratings and Reductions."

We're pulling out all the stops, complete with plans to totally eliminate coal by 2020. In the meantime, with a formal Climate Action Plan that calls for climate neutrality by 2050, we're working on a number of near-term low-cost strategies to reduce emissions to the 2000 level by 2020. As with many a long-range initiative, methodical attention to detail is producing measurable outcomes.

Cost-effective Carbon Reduction

Serious carbon reduction efforts began in 2007, when we hired a full-time carbon emissions specialist and completed our first greenhouse gas inventory. We found that building energy use accounted for more than 90 percent of the university's carbon footprint. While UNC's Climate Action Plan, completed in 2009, charted the path to climate neutrality by 2050, we concentrated first on 17 near-term initiatives that would give us almost immediate cost savings. Figure 1 depicts the 17 components.

UNC leaders created a program to operationalize each of the Climate Action Plan strategies and track progress. Work is under way on a number of the near-term strategies, including thin clients (computers that have no hard drives or software, but only a single connection to a server that provides programs, data access, and storage); chiller plant efficiency; green buildings; heat recovery chillers that capture waste heat for reuse rather than rejecting it to the atmosphere; landfill gas; 20 percent coal substitute in the cogeneration plant—and low-cost energy conservation measures, the focus of this story. (See www.climate.unc.edu for more information on the commitment, the annual greenhouse gas inventories, the climate action plan, and the climate program.)

Coordinating a Quick Start

At UNC, two separate organizations manage energy supply and demand of campus buildings. The energy services department generates thermal energy—in the form of steam and chilled water—and electricity. They meter each utility at the building level. Energy management, a unit within the facilities services department, manages building energy consumption. Engineers focus on upgrading building performance through commissioning (conducting an intensive quality assurance process) and retrocommissioning (applying a similar process to existing buildings). In a separate energy management control center, technicians manage operation of the HVAC (heating, ventilation, and air conditioning) systems in individual buildings.

As a follow-on to the Climate Action Plan, UNC adopted a comprehensive energy policy in 2009. Its guidelines, which require a campuswide commitment, cover temperature and humidity standards, occupancy schedule standards, lighting, purchasing, and behavioral education. This policy is critical in communicating senior administrator support for energy conservation.

Attempts to standardize temperature and occupancy schedules prior to adoption of the policy had been unsuccessful. Once the formal directive was adopted, the energy management department developed energy conservation measures, a suite of specific engineering measures applied to building HVAC systems to reduce energy demand without the need for behavioral change by occupants. The underlying assumptions were that energy management would have (1) unlimited access to any resources in facilities services, (2) a maximum budget of $200,000, and (3) a goal of reducing energy consumption by 15 percent in three months, starting in June 2009.

We spent two weeks developing the energy conservation measures, which consisted of six types of actions:

• Implement supply-air reset schedules. The goal was to dynamically modify supply temperature to keep the air as warm as possible without overheating the spaces or causing high humidity.
• Implement occupancy schedules. This was done by either turning off the HVAC equipment or allowing space temperatures to float during unoccupied times.
• Reprogram terminal boxes. Operating with lower air flow would allow greater system turndown.
• Eliminate simultaneous heating and cooling at air handlers.
• Implement space-temperature standards.
• Optimize air-side economizers and heat recovery systems.

The project focused on buildings with operations funded by state appropriations, about 60 percent of the campus. The team did not include buildings smaller than 5,000 square feet.

We developed a detailed communication plan to inform the campus community of the efforts, the potential impacts, and ways to support the initiative. The campus student daily newspaper and the employee semimonthly newspaper both printed detailed stories. The energy management staff sent information to all building managers via e-mail and met with each building manager just prior to commencing work on the particular manager's facilities.

Facilities services committed eight full-time employees to the program and divided them into two-person teams. Whenever possible, the HVAC maintenance mechanics joined the teams working in their assigned buildings. A one-page data form was used for each building, with details of the specific work recorded. As the work progressed, two of the six measures—optimization of economizers and heat recovery systems, and elimination of simultaneous heating and cooling—proved to take much longer to implement than the others. We made the decision to create a second phase of the project for these items.

The scope of the second phase ultimately was expanded to include calibration of all actuators and sensors on each air handler. This was important to ensure that freeze protection devices were operating properly, since maintenance personnel expressed concern that enabling economizers might expose chilled water coils to freezing temperatures. Verifying operation of such safeties was important to ensuring confidence in the program.

On-site Monitoring

The implementation steps for each building included a one-day walk-through with the building manager and the HVAC maintenance mechanic. These on-site reviews had three purposes: (1) identify maintenance actions required to be completed before energy optimization (these were performed by the implementation team or, for more complicated tasks, by the maintenance staff); (2) afford an opportunity for detailed discussion with building managers about schedules, allowing the schedules to be fine-tuned if needed; and (3) allow managers to determine the specific methods for applying the energy conservation measures.

Following the walk-through, team members reprogrammed the HVAC system as directed by the team lead. The teams were not constrained by the original design intent, as would be the case with retrocommissioning, but rather used their education and experience to define the optimal situation for each building. Finally, monitoring and iteration were required to tune building system performance to meet the required environmental conditions and optimize energy.

Building-level metering for each utility (electricity, steam, and chilled water) proved invaluable in this effort. Since each building is individually metered and provides dynamic, real-time usage data for steam and chilled water, the teams were able to see immediately the results of each implementation step of the conservation plan. This provided the unplanned benefit of educating the maintenance staff in realizing the direct impact of each action they took on the building systems.

Monthly tracking of energy consumption was also necessary to monitor the performance of each building and the total program. Initially, we did this by comparing each building's total monthly energy consumption to the average of the previous two years' consumption of the given utility for the same month.

During implementation of the energy conservation measures, however, variation in outside air temperature was much greater than it had been in previous years, and we needed to develop another method to correct for weather extremes. Plotting energy consumption against average monthly temperatures for several prior years, we established a baseline average and conducted a regression analysis to determine accuracy of the fit to the data. Then for a given building and a given month, comparing the average monthly temperatures of the current and the aggregated prior years allowed us to predict future energy consumption, compare it to the actual energy used, and calculate the savings. 

Representative Results

Figure 2 shows the results of the energy conservation program on steam consumption in one UNC building, Bondurant Hall. We implemented the program in this building in August 2009, and steam consumption for the month dropped 53 percent compared to August 2008.

Here is a snapshot of key results realized from the implementation of the energy conservation measures in FY09–10.

Average building completions—2.5 per week.

Cost savings—$3.9 million.

Energy saved-chilled water, 15.1 million ton hours; steam, 188,891 thousand pounds; electricity, 9.5 million kWh—for a total of 413,179 million BTUs.

Greenhouse gas reduction—41,419 metric tons of carbon dioxide equivalents.

Water savings—27.2 million gallons (from reduced consumption in chiller plants).

Energy reduction—17 percent.

Number of air handlers calibrated and tested—346.

We achieved all this at a total cost of $212,222, which included materials and contracted labor. Internal labor hours expended by the energy management teams amounted to 6,133.

We realized other benefits, in addition to lowered energy consumption. One was a reduction in calls reporting buildings that were too hot or too cold. This seemed counterintuitive given the recalibrations that were done, but apparently resulted from improved system performance that allowed increased airflow, lower noise, reduced downtime, and lower maintenance costs. 

The team continues to monitor the buildings to make sure they operate efficiently. We continually add new buildings, as owners of revenue-supported buildings opt to become part of the program. A powerful incentive for them to pay to join the program is that UNC's energy rates allocate fixed costs based on relative consumption, so as state-funded buildings conserved energy, owners of other buildings saw their costs rise. (State appropriations-supported buildings do not pay fees related to the energy conservation program; receipts-supported buildings pay on a fee-for-service basis, which is usually calculated on hourly rates that vary depending upon the type of service received).

Can Coal Be Far Behind?

The largest component of greenhouse gas emissions from buildings comes from the use of coal at UNC's cogeneration plant, which produces all the steam and about one third of the electricity consumed by the campus. While the energy management teams continue to implement additional conservation measures, eliminating the use of coal is critical to achieving carbon neutrality.

In contrast to many peer institutions, UNC has a cogeneration plant that is relatively new, having come on line in 1990, with decades of useful life remaining. The near-term (2020) climate plan includes substitution of a renewable fuel for 20 percent of the coal use, and the 2050 plan includes four alternatives for substantially reducing or eliminating coal consumption: plasma gasification of municipal solid waste, a new large-scale biomass plant, 100 percent coal substitution in the existing plant, and a mix of 50 percent natural gas and 50 percent coal. Adoption of some of these technologies would require the replacement of the existing plant.

In 2009, the Sierra Club's Campuses Beyond Coal campaign targeted 60 U.S. campuses that were still burning coal, including UNC. The Sierra Club urged these campuses to lead by example, cut their pollution, and end burning coal as soon as possible. UNC's Sierra Student Coalition led a Coal-Free UNC Campaign to call for the end of coal use at UNC by 2015. In response, Chancellor Holden Thorp appointed a total of 10 students, faculty, trustees, and community members to a task force to make recommendations before the end of 2010 to reduce Carolina's carbon footprint. The task force recommended implementation by 2020 of the 100 percent coal substitute option in the climate action plan, with use of biomass sourced from certified sustainably managed forests as determined by third-party verification. This recommendation was accepted.

The energy services department had already scheduled biomass testing to begin in fall 2010 to meet the original plan for 20 percent biomass substitution by 2020. Successful tests of the fuel-handling system and one test burn of woody biomass have been completed so far. Fuel availability has proven to be a major challenge, and the situation in the southeastern United States may not improve absent carbon legislation at the federal level. Thus, the current focus for those on the supply side of the energy equation at UNC is the development of strategies to ensure reliable biomass supplies.

We still have a long way to go to reach energy neutrality. But, we're pleased that our near-term efforts have been effective and are intent on putting more low-cost quick fixes on our to-do list. After all, in the case of our award-winning Morrison Residence Hall, it took only $35,000 to cut more energy use than any other building competing in EPA's nationwide contest. And we can't overlook the unbridled student enthusiasm around this and other UNC energy-reduction projects.

CAROLYN ELFLAND is associate vice chancellor for campus services and CHRIS MARTIN is director of energy management at the University of North Carolina at Chapel Hill. This article is based in part on a more expansive presentation at the UNC Sustainable Energy Conference and Workshop sponsored by the U.S.-Russia Foundation in October 2010.