Daniel McKelvie 2015-11-12 17:02:05
As the fifth-busiest airport in the world, Los Angeles International Airport (LAX) serves nearly 70.7 million passengers a year with one-quarter of the total going to or coming from international destinations. To stay competitive with other global airports, LAX began a multibillion-dollar program that includes construction of the new $1.9-billion Tom Bradley International Terminal. This project, also known as “Bradley West,” opened to the public in 2013. It provides 18 new gates that accommodate new-generation aircraft such as the Airbus A380 and Boeing 747-8. The terminal also encompasses a large hall for dining, shopping and other passenger amenities, and bigger customs and immigration and passenger security screening areas. The Bradley West project not only added to the number of gates, but also increased the heating and cooling requirements on the old Central Utility Plant (CUP) serving the airport. Constructed in 1961, this CUP had been updated several times, most recently in 1983 when combined heat and power (CHP) was added, and the chiller plant was upgraded. By 2008, the CUP’s capacity was exceeded by the increase in terminal heating and cooling demands, its efficiency was well below current standards, and the system was further taxed by the addition of Bradley West. As part of the overall airport modernization, a replacement CUP was required. In February 2011, a $423.8-million construction project was launched to replace the old CUP with a new one. Centrally located in the heart of the Central Terminal Area (CTA), west of the iconic LAX Theme Building, the new CUP was designed to be an efficient, state-of-the-art facility that would meet LEED (Leadership in Energy and Environmental Design) Silver certification standards and serve LAX’s current thermal and power needs with some additional capacity for future growth. Creating a New CUP The new CUP site is located directly west of the Federal Aviation Administration (FAA) air traffic control tower within the CTA. The project’s small footprint posed unique design challenges. For this reason, new cooling towers were placed above a newly constructed maintenance building adjacent to the site and not on the roof of the new CUP. Another challenge was to increase the chilled and heating hot water temperature differential (ΔT) at each terminal in order to significantly reduce energy usage, increase efficiency, and optimize the system performance. A further objective of the project was to install as much heating and cooling capacity as physically and economically possible to serve future growth and mitigate or delay the need for an additional utility plant in the future. Architecturally, the new CUP building is four stories tall with a total floor area of approximately 64,000 square feet. The CUP contains new equipment, including cogeneration, chillers, boilers, heat exchangers, pumps, water treatment, and other systems necessary for serving the power and thermal needs of the airport. The new chilled-water system is very energy efficient and employs variable-flow pumping on both the chilled-water and condenser-water loops. Similar to the old CUP, the new facility is also a hybrid plant, utilizing both electric and steam turbine-driven chillers. One large technological enhancement is the chilled water thermal energy storage tank located west of the CUP. The storage tank is made of insulated steel with a capacity of 1.53 million gallons of water, equating to 15,500 ton-hours of cooling capacity at designed operating temperatures. The purpose of the thermal energy storage tank is to store chilled water created by the electric chillers during off-peak periods when electric rates are low and an electric chiller can be dedicated to filling the tank. The tank saves approximately 2 MWh of electricity for every peak hour it operates at design conditions, since it replaces a good portion of one electric- driven chiller. Hot water remains the heating medium for the airport, but it is delivered at a lower temperature (220°F) than the old CUP (280°F) and is, therefore, more energy efficient. Maintaining the same temperature differential permitted the existing piping network sizes to be retained. The steam is the primary source of heat that is delivered from the combustion turbine generators and the heat recovery steam generators (HRSGs) to two shell-and-tube heat exchangers that generate low-temperature hot water. A New Cogeneration System Two Solar Turbines Mercury 50 natural gas-combustion turbine generators provide 4,179-kW output, each at 4,160 V during peak operating conditions. Furthermore, each turbine generator provides 12,900 pounds-per-hour output of 150 pounds-per-square-inch (psig) steam from the downstream heat-recovery steam generator in an “unfired” mode. The steam load requirements of a single-steam turbine-driven chiller was matched to the output of one unfired combustion turbine generator so that the CTG’s waste heat may be used year round. With the new CUP in operation for more than a year, it has become apparent there is a greater need to provide heating (more heating load) during the summer than originally thought, due to simultaneous heating and cooling occurring in the airline terminals. Therefore, the steam chillers will have less operating hours than originally assumed, since operating electric-driven chillers is more economical than the supplemental firing of the HRSGs to run steam chillers. The new CUP’s electrical distribution system allows the CUP to consume generated power directly. This is distinctly different from the design of the old CUP. A Los Angeles Department of Water and Power (LADWP) electrical network station was considered initially, but was not economically justified at the time. A network station would have allowed the Los Angeles World Airports (LAWA) to redistribute power from the CUP, and thus allow the combustion turbine generators to operate at 100% capacity so that all the power could be used internally at the airport and not exported to LADWP’s electrical grid. Without the network station, the electrical output of the CTGs is limited to the power demanded by the CUP (chillers, pumps, fans, lights, etc.) and Central Terminal Area (street and parking structure lighting). If the electrical loads of the CUP and CTA fall below 50% of full load, then either the surplus electricity is exported to the LADWP electrical grid, or the CTG is de-energized. The current rate of compensation by LADWP for the CUP’s exported power is unfavorable and the CUP will export power only as needed for stable and continuous operation. Facility Monitoring and Control System The Facility Monitoring and Control System (FMCS) was required to integrate legacy controls (JCI Unity and NEXSys) from each terminal/building into a common monitoring system. This was accomplished using dedicated computers located in the pump rooms of each terminal/building that collect all the legacy trunk information and send it over the FMCS optical fiber network to a dedicated server in the CUP server room. The servers then convert the data into BACnet protocol, which is accessible by Wonderware, for overall monitoring and control purposes. The FMCS is highly scalable and will facilitate future initiatives to integrate, centrally manage or monitor building-wide systems throughout LAX. There is currently an “FMCS Extension” integration effort underway—separate from the CUP project—that will integrate the building automation system (BAS) equipment from several systems and buildings that were not available for integration at the inception of the CUP project. Significant Energy Savings Annual operating cost savings for the new CUP are estimated to be about $7 million, or 25% more efficient than the old CUP, based on the 2014 load base prior to connecting Bradley West to the new distribution system. The savings are from a combination of improved equipment efficiency, as well as the economic advantages of CHP implementation over the old CUP since LAWA can currently generate power more economically than purchasing from LADWP. Maintaining efficiency levels into the future will depend greatly on achieving high chilled-water and heating hot-water temperature differentials (ΔT). Actual ΔT from the terminals must be maintained at or near the chilled water design ΔT of 16°F and heating water design ΔT of 50°F to preserve plant capacity and minimize pumping and overall CUP energy costs. Overall ΔT improvement to the chilled-water and heating hot-water system has been good so far, but room for improvement remains. Actual success in several terminals has been excellent, and there are notable increases from the old CUP operation due to the upgrades to the terminal pump rooms and FMCS/BAS. Terminal renovation projects continue to replace existing air handling units, coils, control valves, and actuators that will further improve the system ΔTs. These future projects are encouraged to select equipment with even larger ΔTs to benefit the global system performance. Completion of an electrical network station connecting the new CUP to the entire airport electrical grid is eagerly awaited. An electrical feeder from the CUP combustion turbine generators to the network station would enable the generators to run fully loaded so maximum efficiency and energy-cost reduction is achieved. The greater attention that ΔT obtains, the greater potential the new CUP has to achieve its design output capacity and mitigate or prolong the requirement for any future heating and cooling plant implementations at LAX. In December 2014, the Los Angeles Board of Airport Commissioners awarded a $961-million design-build contract for the new Midfield Satellite Concourse (MSC). Distribution piping will be extended west from Bradley west to serve the MSC, which will add new cooling and heating demands to the new CUP. Like any large vibrant airport, LAX will continue to expand and evolve to satisfy the growing needs of millions of domestic and international travelers. The new CUP will continue to satisfy the airport’s energy needs for many years to come. Team Members AECOM served as program and construction manager on behalf of Los Angeles World Airports. From the outset, the CUP replacement project was designated to be delivered using a design-build method of construction. Syska Hennessy Group (including Adamson Associates Architects) was engaged via Hatch Mott MacDonald to prepare the project criteria—architectural, mechanical, plumbing, controls, and electrical bridging documents—that would be incorporated into the request for proposal (RFP). Four design-build teams responded to the RFP and after a three-step qualification process, the joint venture of Clark Construction Group LLC and McCarthy Building Companies Inc. (Clark/McCarthy, a joint venture, aka CMAJV) was awarded the project in early 2010. The CMAJV design-build team was composed of the following organizations: • ARUP, engineer of record for mechanical, plumbing, electrical, communications, structural, and civil engineers • Gruen Associates, architect • Capital Engineering Consultants Inc., commissioning authority • Murray Company, mechanical contractor • SASCO, electric contractor • W.A. Rasic Construction, underground utilities contractor • KDC, low-voltage contractor • Johnson Controls Inc. (JCI), controls contractor Manufacturers’ Information 1) Chillers: York electric drive and steam turbine drive centrifugal chillers 2) Gas Turbines: Solar Mercury 50 3) Heat Recovery Steam Generator: Rentech Boiler Systems—single pressure, single evaporator 4) Pumps: B&G 5) Cooling Towers– CCS 6) Main Switchgear– GE 7) Facility Monitoring Control System/Building Automation System: JCI–Metasys, Wonderware, Allen Bradley Programmable Logic Controllers 8) Thermal Energy Storage Tank: CB&I Dan McKelvie, P.E., is an executive with AECOM’s transportation group and has led many business practices and major programs during his 26-year career with the company.
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