Retro-Commissioning Projects at UConn

Transcription

1 Retro-Commissioning Projects at UConn UConn currently has plans to retro-commission 34 buildings on the main campus. These buildings will be investigated in three phases by four different engineering firms. The twelve buildings of phase I are currently being investigated. So far, recommendations for four of these buildings have revealed the possibility of $145,000 in annual energy savings with only a five year payback period. The payback period is likely to be even less than this because the University will recoup up to a half of its costs through the Connecticut Energy Efficiency Fund (CEEF) in the form of a rebate. These projects are being funded by the renewable energy credits (RECs) that the University has received from operating the highly efficient natural gas cogeneration facility for its electrical and steam needs. Retrocommissioning is considered a priority recommendation in the University s Climate Action Plan (CAP). The four buildings so far investigated will save the same amount of CO 2 emissions as removing 89 cars from the road. What is Retro-Commissioning? Commissioning a building refers to the process of improving how a building operates. Specifically, it is the testing and fine tuning of a building s equipment and systems so that they function optimally and efficiently, or as designed. This can either be done to a new building or an existing building. When an existing building is commissioned, the process is called retro-commissioning. Retro-commissioning is not the same as retrofitting. Retrofitting involves the replacement of existing equipment with newer, more efficient equipment. Because there is much overlap in how the building is investigated in both processes, retro-commissioning and retrofitting are often performed at the same time. Both procedures have the potential to make meaningful reductions in long term building operation costs. Retro-commissioning begins with a planning step. During this time, a retro-commissioning provider speaks with the building owner and inhabitants to find out what they need their building to do. For example, a server room will not have the same energy and cooling needs as a kitchen. The provider also speaks with the staff responsible for maintaining the building to see what their capabilities and requirements are. It is also important to know what the owner s goal is. If available, the building s asbuilt design drawings and specifications are reviewed to understand how the building s systems were supposed to operate when constructed. Common sustainability goals include LEED for Existing Buildings: Operations & Maintenance and Energy Star certification. Investigating the building s systems may include benchmarking and energy audit phases. During a benchmarking phase, the typical energy and resource (such as water or natural gas) profile is made for the building of interest. This profile is compared to similar buildings (i.e. similar size, occupancy and use, climate, etc). This also allows for operational savings to be quantified so that the building owner can understand the effectiveness of the improvements and the importance of maintaining them. An energy audit provides suggested changes on how to improve the energy efficiency of a building.

2 Often, certain changes are immediately made. These include low- to no cost changes (less than $500) and changes that have a short payback period (usually less than a year). 1 These changes are typically very simple, such as moving objects that may be blocking an air vent, replacing worn out seals on a leaking pipe junction, or even just reviewing the schedule for a thermostat to make sure it turns on and off at the right times. The costlier and harder to recoup costs may or may not be done depending on a variety of factors. Besides the owner's discretion, rebates are one of the largest factors. Some retrocommissioning projects are eligible for rebates from utility companies. For example, in 2009 nearly three-fourths of the cost of retro-commissioning the 55 West Monroe building in Chicago was covered by a utility company rebate. In Connecticut, utility company rebates, often as high as % of the costs of retro-commissioning, are offered through the Connecticut Energy Efficiency Fund (CEEF), which is administered by electric utility companies. For retro-commissioning projects at 34 UConn buildings, begun in 2010, Connecticut Light & Power has reviewed, or will review, all specific proposed implementation measures and is developing letter agreements verifying which measures are eligible for reimbursement under the CEEF. There are also nonmonetary benefits to take into account with some changes, such as improvements in indoor air quality. After system adjustments have been finalized, providers educate the facility personnel in how to use and maintain the systems. Failure to do so will lead to degradation in the building systems. This would return the building to a below optimal and inefficient state. Monitoring software may also be installed in the building systems so that the provider can continue monitoring the building remotely. Some providers will continue working with the building personnel for as long as a year after the last improvement to ensure that optimal conditions are maintained. Providers train the building personnel to commission the building themselves to adjust for occupancy changes or other conditions that cause a change in system performance. Retro-commissioning is a very promising way of reducing a building s environmental impact and saving money. In 2009 Facebook announced that it had retro-commissioned two of its data centers and was able to prevent 2,055 metric tons of carbon dioxide emissions a year, which is equivalent to taking 727 cars off of the road each year. This process, which primarily involved changing fan speeds and air handling temperatures, will save the company $503,000 a year for these two data centers. A Retro-Commissioning Project at UConn: The Student Union One of the buildings undergoing the retro-commissioning process is the Student Union (SU), located at the heart of the UConn Storrs campus. In September 2010, the SU was studied by Sebesta Blomberg Associates, Inc. (the retro-commissioning provider). Presently, a report has been submitted by the provider that enumerates a number of retro-commissioning measures the University can take in the SU as well as a number of other energy conservation measures (ECMs) that the provider noted during their investigation. 1 From Retrocommissioning: Big Savings for Big Buildings in Environmental Building Services, October 2010.

3 Sebesta Blomberg gave retro-commissioning recommendations primarily in regard to how the air and ventilation systems are programmed. They presented a number of ways in which these various systems can be reprogrammed to save energy. Most simply, each air unit has a schedule signaling it when to turn on and off as well as how hard to work when it is on. Each unit also has temperature set points that tell it to start and stop working. It is important that these units are programmed to work as a system because some units are more efficient at certain temperatures than others. Sebesta Blomberg s first set of recommendations were in regards to the SU s air handling units (AHUs). Air handling units are a combination of systems that heat, cool, and circulate air throughout an area of a building. A total of four suggestions were made. 1. Reprogram the AHU schedules. Some of the units were on when the area they serviced were not in use. 2. Reprogram temperature set-points. Temperature set-points tell the units when they need to heat and condition air brought in from the outside. Adjusting it the set-points for seasonal differences would decrease the amount of conditioning done to the incoming air. 3. The equation used by the AHUs to determine when to use outside air was rewritten to be more efficient. Previously, the decision was only based on temperature. In some circumstances, cooler outside air may cause warming in the building due to differences in humidity levels. The new equation takes this into account. 4. A number of systems relating to the AHUs were found to be working improperly. Some AHUs received restricted air flow through the building infrastructure, meaning that the AHU would have to work harder. Also, many of the units had lost contact with the building automation system (BAS) so they worked on the same setting all the time. This sometimes caused units to overshoot heating and cooling set-points, requiring the unit to perform the opposite action. Overall, these recommendations were estimated to cost $70,000 and would have an annual savings of $60,000. After only 14 months, the University will have saved enough to cover the costs of the retrocommissioning. In additional, the provider would be programming the building automation system to send an alarm to the building staff if the units ever encounter the problems described above. A number of other suggestions were made regarding other ventilation systems in the building. These suggestions are all rather similar to the ones noted above for air handling units. In part, this is because the suggestions are mostly for make-up air units (MAUs), which are essentially AHUs that solely take in outside air and condition it before sending it to the AHUs, and the heating, ventilation, and air conditioning (HVAC) system, which is an umbrella term that includes both AHUs and MAUs. There were four additional energy saving retro-commissioning suggestions. 1. It was suggested that the scheduling for HVAC be reprogrammed because there were times when the system ran, even though the areas it serviced were unoccupied. 2. Temperature set-points would be reset in such a way that would decrease the demand for ventilation. Carbon dioxide detectors would be installed and a set-point would be set for CO 2 concentration. Pressure sensors would also be installed as well as a pressure set-point set.

4 3. An occupancy sensor would be installed in rooms that are only intermittently occupied throughout the day. Heating and cooling set-points would be set at lower and higher temperatures, respectively, when the rooms are not occupied. The set-points would return to normal when the rooms become occupied. 4. An exhaust control system would be installed in the exhaust hoods at the kitchen for the food court. This control system would monitor whether or not cooking was occurring and, if so, would determine the appropriate fan rate for ventilating all of the cooking gases. Currently, the exhaust hood fans constantly operate at full power. All eight of these energy saving retro-commissioning suggestions would cost a total of $435,000 but would save the University $120,000 a year. At that rate, the savings would pay for the cost in only 3.5 years. There were additional suggestions made. Some are retro-commissioning suggestions not pertaining to saving energy and others are retrofitting recommendations. 1. Recalibrating building sensors. Many were found to be improperly reporting. 2. Install additional occupancy sensors to control lighting in rooms that are only intermittently used. 3. Upgrade the water pump for the building. The current pump works at full capacity at all times to maintain water pressure in the building. The upgrade would install a variable fan drive (VFD), which would allow the pump to operate at different power levels to maintain the building water pressure. 4. There were some places were building insulation could be upgraded. 5. The ballrooms and numerous meeting rooms have very large windows, which can have drastic effects on the heating and cooling loads for those rooms. Installing a tint to these windows could have various benefits on the temperature regulation of these rooms. The costs and savings of this project were not quantified. An Overview of Retro-Commissioning At UConn UConn currently has plans to perform retro-commissioning on 34 buildings. These buildings are being investigated in three phases. Over three million square feet (i.e., about one-third of the Storrs campus) are represented by these projects. UConn has contracted with four retro-commissioning providers to evaluate many of the buildings on campus and to implement favorable changes. These contractors are Strategic Building Solutions (SBS), Sebesta Blomberg and Associates, Inc., Dome Tech, Inc., and van Zelm Engineers. Three buildings that were recently investigated have shown great promise for the program. These three buildings would only cost about $180,000 to retro-commission and would save over $25,000 a year on electricity. This equates to a 6.8 year payback period. These costs will likely be partially defrayed by rebates through the CEEF. These results can also be tied directly to the environment. This reduction in electricity use would require the central utility plant to burn less natural gas each year. Specifically, 88 metric tons of carbon dioxide would be prevented, which is the equivalent of removing 17 cars from the road each

5 year. These three buildings represent only about ten percent of the buildings (and building space) included in the investigation. The estimated costs of these projects are based on worst-case scenarios. In reality, the costs are often much lower. Utilities and the government often offer rebates and other incentives (such as tax credits) to building owners for retro-commissioning their buildings. Utilities and the government often also offer monetary incentives for retrofitting and other energy efficiency projects, which are likely to be investigated alongside with retro-commissioning. UConn is working closely with Connecticut Light & Power, which provides purchased electricity to the University, to determine which of its energy conserving measures are eligible for rebates through the CEEF. The University Climate Action Plan identified retro-commissioning as a priority recommendation for reducing its greenhouse gas emissions. Of the four buildings specified above, about 500 metric tonnes of CO 2 equivalence can be prevented, which is the equivalent of removing 89 cars from the road. In addition, retro-commissioning is a financially sustainable process as it causes cost savings after a certain number of years. The retro-commissioning projects at the University are also being funded due to other emissions reducing projects on campus. Namely, these changes are occurring because of the University s RECs, which it gets by operating the highly efficient cogen facility. Overall, the University stands to improve the quality of occupancy space in its buildings while also reducing energy costs and its impact on the environment. While it may be a confusing and at times an abstract concept, retro-commissioning is a promising method of creating an energy efficient environment at UConn.