The recent slow down in the domestic economy, coupled with the increase in fossil fuel costs, have given new emphasis to utility costs. Facility managers are becoming increasingly aware of the impact that electric utility deregulation and higher energy prices can have on the bottom line. A savvy manager realizes the need to develop strategies that can lower energy costs and improve operational efficiencies. HVAC energy use is typically the largest variable electric load in a building. With the increased application of microprocessor based controllers on mechanical equipment, additional operating information has become available to use in optimizing the operation of these systems. Benchmarking of system operation and energy use is the first step in the process of optimizing the operation of a building's HVAC systems.

HVAC CONTROLS IN THE INFORMATION AGE

For those of you that measure your experience in decades, rather than years, it is not too hard to recall a time when controls consisted of a series of electro-mechanical devices or pneumatic-powered systems sequenced by time clocks. It wasn't until the early 1990's that the cost of microprocessors dropped enough to allow their use on individual HVAC components. The state of technology today provides for operating information from each component to be accessible over LAN -based information systems.

In its entirety, the amount of information that is available through these networked control systems is often overwhelming. The operation and maintenance of these systems is typically the responsibility of the building operators. Most often, historical operating information is used for troubleshooting maintenance problems. This ignores the opportunity to utilize this information to improve the overall operation of the HVAC system through long term trending.

BENEFITS OF BENCHMARKING

Facility managers are charged with assuring that all equipment operates at peak performance and efficiency levels. Through the implementation of a benchmarking program, real-time operating information can be utilized to improve the decision-making process in the evaluation of potential capital projects.

Baseline Energy Use
In an increasingly competitive marketplace, costs are a critical driver of corporate performance. A primary objective of a benchmarking program is the establishment of a baseline of system operations and energy use. The goal is to identify the components that use energy, and to summarize when and how much energy they use. With HVAC energy use being the largest variable electrical load in a typical commercial building, maintaining an annual benchmark of usage will become very useful information as the nation's electric utilities move toward deregulation.

Continuous Commissioning
Commissioning is a process by which an operator is assured that systems are operating at peak performance and efficiency levels. In addition to collecting energy use data, a properly configured monitoring program will also identify the critical factors that can impact system energy use. This information can be used to continuously fine-tune system operations, uncovering existing problems or even make the systems work for the first time. According to the Oregon Office of Energy, studies on commissioning programs show average energy savings of 15% to 30%. Real-time operating information can be used as an energy management tool to optimize performance, improve efficiency and lower energy consumption.

Developing Energy-Saving Projects
Just as commissioning assures that systems are operating as they were originally designed, advancements in technology may offer opportunities for system upgrades to improve efficiency. This is particularly true for HVAC control systems. Adding control points and changing sequences of operation are relatively low cost items, and can have a profound effect on the operating efficiency of a system. Using information provided through a monitoring program, energy management strategies can be developed that can lower energy costs and improve operational efficiencies. From simple retrofits and upgrades to system modifications and replacements, cost-saving measures can be self-funding, paid for over time from the energy savings delivered.

Real-Time Modeling
Evaluating the impact of proposed energy projects has always been a challenging effort. The model developing process requires a technical understanding of the functions of building operation. A key skill for the model builder is the ability to identify the important factors that simplify a complex technical reality. The best way to verify the accuracy of a model is to compare it to known data. In a typical case, the only known data for a building is the monthly utility bills. A building model would have to include all energy using components in order to use the utility bill data to validate the model accuracy. This validation method would be of limited value, except on the largest retrofits, due to the relatively small impact most modifications would have on overall energy use. Engineers are then left to calculate energy savings with no method of model validation. This can result in wide swings in estimated savings, depending on the assumptions made about the building operation. This, in turn, lowers confidence in the results of the analysis, and raises the required return on investment to compensate for the higher risk.

This is not the case in a building with a benchmarking program. Actual operating information from building components can be used as the basis for modeling operational and equipment changes with a very high degree of accuracy. Using hourly data, cost savings can be estimated precisely, even in areas with highly complex utility rate structures.

Savings Verification
Another benefit to benchmarking is the ability to verify actual energy savings from operational and equipment changes. Operational information can be used to assure projects are implemented correctly, or to identify reasons for not achieving the estimated savings. This feedback can be utilized to build confidence and support within the organization for funding of additional capital projects.

GOALS OF THE BENCHMARKING PROJECT

An important benefit of monitoring HVAC control systems is the establishment of a benchmark for plant operations. Facility managers can use this information to identify O & M changes and capital projects to reduce energy costs. The accuracy of energy savings calculations is greatly enhanced with models developed from benchmark information. These recommendations should be evaluated using life cycle costing techniques including installed costs, changes in maintenance costs, and system service life. The monitoring program can then be used to measure and verify the impact of these changes on the plant operating characteristics. Many of these opportunities would not be uncovered without the information provided through the benchmarking project. It is a low cost method to gather data with which can be used to reduce rising utility costs.

SHORT FORM BIO

A graduate of Carnegie-Mellon University, Mr. Watson is a professional engineer with over 20 years of practical experience in all facets of the HVAC industry. In his position as project engineer for E3 Designs, he is responsible for overseeing HVAC monitoring projects throughout North America. He can be reached via e-mail at jwatson@e3designs.com. and would welcome any feedback.