The greatest energy savings available to larger airports can be generated from a facility’s existing chiller plant operation, where even small tweaks can result in significant improvements. Today’s web-based monitoring systems can be an effective tool for the analysis of large chiller plants and district cooling systems. Built on open standards, they offer networked solutions that collect and format data in real-time and defined timeframe increments, monitor operations and equipment errors, and deliver oversight via web-based alerts and alarms. Based on the information generated, engineers are able to track performance and remedy any malfunction in order to optimize energy efficiencies.
Initial analysis
The monitoring process starts with an initial analysis of chiller plant operations. In most cases, industrial measurement devices are installed and existing equipment tested for accuracy. The data from the various systems is pulled together in one platform with data routed to an automation system and pushed to the web every five minutes via ftp. Once all of the accurate data collection is complete, an evaluation is done to understand how all chiller plant components are working and to determine the most efficient method of operating the plant.
By analyzing chiller operations, the monitoring engineers are able to establish a matrix that selects the most efficient/cost-effective chiller configuration as an airport’s cooling load increases. Optimization steps might include redoing the sequencing of cooling towers, balancing the amount of energy consumed by different pieces of equipment, and allowing chilled water to be generated at the best efficiency and lowest cost. Other cost-saving measures can be implemented by callibrating temperature sensors and the building automation system, eliminating inefficiencies in heat exchanger performance, lowering condenser temperatures when appropriate, and ensuring that flow through the plant and chillers meets the design tonnages recommended by the equipment manufacturers.
Once the initial reconfigurations have been achieved, the web interface enables continuous remote monitoring of a plant to ensure optimum operation is maintained on a continous basis. Monthly reports are submitted to the airport’s operating team suggesting necessary system enhancements or improvements.
Monitoring-based commissioning
With new airport facilities, generating ongoing energy savings can be achieved through a comprehensive monitoring-based commissioning (MBCx) process to ensure that all building systems remain “in tune.” It is common knowledge that buildings rarely perform as intended. That’s why MBCx is beginning to emerge as an important new approach to keep buildings operating at maximum energy efficiency. Complementing other energy savings strategies, it refers to the “soft” process of verifying performance and design intent and correcting deficiencies through a continuous web-based monitoring program.
MBCx incorporates three components: permanent energy information systems and diagnostic tools at the whole-building and sub-system level; retro-commissioning based on the data this generates; and ongoing commissioning that ensures efficient building operations and measurement-based savings accounting. Traditional commissioning is a process designed to ensure that all building systems perform interactively according to the design intent and the owner’s operational needs. It involves the participation of an owner’s representative, architect, and engineer of record as well as independent third-party commissioning specialist. The commissioning specialist works with the entire project team to verify that the design, construction, and start-up of all equipment results in a facility that is achieving the owner’s stated project requirements upon initial occupancy and protecting the owner’s assets for the future.
Here’s where monitoring-based commissioning takes over. Even the most technologically sophisticated facilities will experience equipment variables that result in diminished energy efficiency. The reasons why buildings typically do not perform as planned might include poor control of chilled water distribution to air handlers, badly sequenced chiller operation, or poor VAV zone control. The ability to verify performance and design intent on a regular basis and immediately correct inefficiencies presents an effective way of keeping a building’s long-term energy use on track. This is especially significant in an airport setting, where utilities are system-critical and various buildings are likely to run on multiple power sources with chiller plants that need to be integrated effectively.
Already there is plenty of anecdotal evidence out there showing the value of monitoring-based commissioning in identifying savings opportunities that would not otherwise have been found. A recent study prepared for the California Energy Commission by Lawrence Berkeley National Laboratory stated: “On a portfolio basis we find MBCx to be a highly cost-effective means of obtaining significant portfolio/program-level energy savings across a variety of building types. MBCx helped identify a very wide range of deficiencies. Anecdotal evidence shows the value of monitoring in identifying savings opportunities that would not otherwise have been identified.”
IAH: A case in point
George Bush Intercontinental Airport in Houston services over 40 million passengers annually. Chilled water at the airport is provided to over 50 buildings by a chilled water plant with installed capacity of 23,000 tons. TD Industries, a utiliVisor licensee that operates the plant, was tasked with reducing energy costs at the airport. To achieve this objective in a verifiable manner, the plant operators needed a way to view performance on a real time basis.
The utilivisor/TD Industries project team began the process by verifying the accuracy of the plant’s energy measurement devices so that performance, as well as the energy cost to generate chilled water, could be monitored holistically. Technicians found that a number of sensors and energy meters were malfunctioning and needed to be replaced in order to receive accurate data. The measurements from all these devices were then routed through multiple automation systems that push the data to the web, providing the operating engineers with a complete picture of energy consumption at the plant, with updates every five minutes.
By adding utility rates to the equation, the team was able to determine the real-time cost to operate the chiller plant. An analysis of chiller plant performance under a variety of operating scenarios and load conditions was performed, leading to the implementation of several no-cost energy conservation measures. These included: plant equipment sequencing; providing an ongoing energy balance between the gas consumption, steam production and chilled water production; recommissioning and reprogramming sequences on the hot gas bypass and inlet guide vanes of the existing chillers; reconfiguring water treatment pumping schedule to reduce pumping kW; and sequencing chilled water pumps based on needed flow thresholds.
Energy conservation measures for the first quarter of 2011 showed verified savings of over $200,000. Based on the plant load required during the remaining nine months of the year, annual energy savings are expected to eclipse $1 million with a payback on the project of 1.5 years.
For airports looking to get a better handle on their existing energy costs and new facilities seeking to maximize their investment in sophisticated chiller equipment and building automation system technologies, remote energy monitoring offers a cost effective means of realizing greater energy efficiencies and lowering operating costs over the life cycle of a facility. Monitoring offers an important risk-management strategy leading to verifiable and durable energy demand reductions for any size airport.
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By Ken Scheeper is an Applied Systems & Energy Advisory Services Consultant with TD Industries, Dallas and can be reached at (972)888-6760; and Timothy Angerame, director of business development for UtiliVisor, New York, and can be reached at (212) 260-4800, ext. 224.
