Innovation in Global Power - Parsons Brinckerhoff

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Thermal – Achieving New Efficiencies, Reducing Carbon Emissions http://www.pbworld.com/news_events/publications/network/ Changes to Chiller, Boiler and HVAC Lower Energy Consumption at a University Campus By Damee Choi, New York, New York, 1-212-613-8835, choiD@pbworld.com New York State has a goal of cutting energy use in schools and other government facilities by fifteen percent by 2015. Our work at the State University of New York campus in Brockport illustrates how PB is helping the state meet this goal. Improvements to the boiler system and other energy saving measures resulted in a six percent reduction in energy consumption. Acronyms/Abbreviations AC: Air conditioning ECM: Energy conservation measures HVAC: Heating, ventilation, air conditioning LED: Light-emitting diode NYPA: New York Power Authority SUNY: State University of New York VAV: Variable air volume VFD: Variable frequency drive Related Web Sites: • http://www.brockport.edu/ • http://www1.eere.energy.gov/ femp/ • http://www.astm.org/ • http://www.nyserda.org/ programs/state.asp PB’s power specialists have been working with New York Power Authority (NYPA) for more than a decade to undertake energy conservation designs for college campuses, municipality buildings and state office buildings throughout New York State. At the State University of New York (SUNY) campus at Brockport, New York, we developed improved systems and plant that reduced energy consumption, enhanced the reliability of campus systems and increased the comfort and safety of building occupants. Some of the key features of this work included: • Introducing a distributed chilled water loop that linked individual chillers in various buildings to increase part-load efficiency • Linking boilers in individual buildings to improve their use and extend boiler life by reducing cycling. Getting Started The Brockport campus is comprised of 40 buildings, most of which are 30 to 50 years old. We assessed these buildings and their chiller, boiler, and heating, ventilation and cooling equipment for potential energy conservation measures. Our team conducted an extensive data collection on the campus equipment to perform cooling and heating load calculations. An economic analysis (life-cycle cost analysis) was performed using Building Life-Cycle Cost (BLCC) 5.2 software, which was developed by the National Institute of Standards and Technology under the Federal Energy Management Program (FEMP). The software methodology complies with American Society for Testing and Materials (ASTM) international standards related to building economics as well as FEMP guidelines for economic analysis of building projects. We developed a number of energy conservation measures (ECMs) that were subsequently ranked based on payback and client preference. The college approved seventeen of them, and PB provided the detailed design and construction management for the work. Distributed Chilled Water Loop A key energy savings was obtained on the chiller system providing air conditioning (AC) for the buildings. The campus had eight electricity-driven water-chillers located in individual buildings. Many of the chillers were either oversized or inadequate for the required duty. By their nature, constant speed chillers operate most efficiently when the cooling load is close to the chiller capacity. They become less efficient in part load use, which is the majority of the cooling season. We designed an underground chiller water loop running in concrete tunnels to connect the individual chillers into a distributed chilled water plant. This technique, normally adopted only in centralized plant systems, improved utilization of the installed capacity and increased the seasonal efficiency. Fewer chillers run during partial load conditions, so the lives of individual machines will be prolonged and efficiency increased. System redundancy improved also, and it was possible to install additional air handling units without the addition of new chillers. Installation of underground piping is always a challenge and this case proved to be no exception. Although we had the campus underground utility records, we asked the contractor to investigate pipe routing with ground penetration radar. We had to confirm that we would not encounter abandoned asbestos piping that was not shown on any drawings, gas distribution lines that were not active, or stone foundations of old houses along the way. PB Network #68 / August 2008 18
Thermal – Achieving New Efficiencies, Reducing Carbon Emissions http://www.pbworld.com/news_events/publications/network/ Improving Kitchen Steam Boiler Operation The original boiler was sized to meet the kitchen load demand, but over time part of the steam kitchen equipment had been converted to direct gas or electric fired equipment, so the boiler had become oversized, resulting in extreme short cycling and a drop in efficiency. We installed a steamto-water heat exchanger up stream of a direct fired gas domestic hot water heater serving the kitchen. The system was arranged to meet the kitchen steam demand first and, if steam was available, to then feed the new heat exchanger. Cold water to the domestic hot water heater passes first through the new heat exchanger and is heated there by the excess steam. It then flows to the direct fired heater. If the available steam is adequate for domestic hot water production, then the heater does not fire. If the steam boiler capacity cannot meet the demand at this moment, then the heater fires and heats the water to the desired temperature. Wide Range of Additional Energy Conservation Measures The following energy conservation measures that we implemented can often be applied to other projects. Water Pump Control. In a number of buildings, we installed variable frequency drives (VFDs) on the water pumps and outside air fans to minimize the water pumping cost and outside air conditioning costs. For example, the Tuttle North building had five constant speed pumps that served the heating system. VFDs were installed at these pumps and the three-way heating coil control valves were converted to operate as two valves to support the variable flow operation. During the occupied hours, the pumps modulate flow to the coil, which reduces power consumption particularly at partial load conditions. When the building is unoccupied, the flow is maintained at 20 percent to avoid coil freezing. CO2 Sensors. The majority of buildings featured air handling units that operated with a fixed amount of fresh air intake that was independent of the building occupancy. This mode of operation, common for building design until several years ago, results in unneeded energy consumption. We introduced CO2 sensors (indoor air quality sensors) that reduce the fresh air intake, and consequently, the heating and/or cooling energy consumption, particularly when the building is only partly occupied. The CO2 sensors are located in the return air ducts of 56 air handling units. They have automatic controls to modulate their outside air dampers and exhaust dampers to suit building occupancy. The CO2 sensor readings fluctuate depending on building occupancy levels. The outside air is set to a minimum rate required for the building minimum exhaust. HVAC Upgrade. At the Metro Center, which has class rooms and lecture halls, the HVAC system was upgraded to include a new variable air volume (VAV) system with summer economizer. This replaced the old high pressure air handling units and window mounted direct expansion (DX) units. Fin tube radiation installed at the building perimeter improved occupant comfort and eliminated the need for costly reheating systems. The chiller was replaced with a new, high efficiency unit. We replaced the constant volume/reheat AC system at the faculty office building, which comprised seven old rooftop units. The new VAV system, which has superior efficiency and provides better air distribution/occupant comfort, will be controlled by the campus building management system. Heat Recovery. Because there are many heat generating HVAC systems on the campus and needs for the heat throughout the campus, we implemented a heat recovery system where it made economical sense. One example is the Tuttle North sports complex, where heat from the computer room A/C condenser was dissipated by a cooling tower. This heat will now be recovered to heat the Olympicsize swimming pool water. Other energy savings at the pool include a roll-over cover to conserve heat when the facility is not in use and VFDs for the water recirculation pumps. Vendor Misers. Lights on the large number of vending machines throughout the campus operated around the clock, as did the compressors for soda vending machines. We introduced vendor-misers, which are proximity sensors that activate the lights on vending machines when approached by a potential user. Shortly after a machine dispenses its product and the buyer walks away, the vendor-miser shuts the power, vastly reducing the energy consumption of the unit. Other Measures. Other measures that contributed to the energy savings and are worth mentioning include: • Replacement radiator steam traps and float and thermostat traps at steam risers in the steam supply mains in several buildings and the elimination of steam leaks • Air-air heat recovery units for building exhaust • A thermal ice-storage system for the sports complex • Water meters • Lighting motion sensors in several locations • Replacement of incandescent lights and T-12 compact fluorescent lights with low wattage compact fluorescent lights and T-8 or T-5 compact fluorescent lights with electronic ballasts • LED-type exit signs • Double-pane windows in the campus library and administrative complex • Improved roof insulation and weather stripping for exterior doors. 19 PB Network #68 / August 2008
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Innovation in Global Power - Parsons Brinckerhoff

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