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— by Joseph J. Watson
The recent slowdown of the domestic economy, rising fossil fuel costs and deregulation have
facility executives aware of energy’s effect on a bottom line.
A savvy manager realizes the need to develop strategies that can lower energy costs and
improve operational efficiencies. Although it’s no secret that HVAC systems typically account
for the largest variable electric load in a building, the energy-savings potential those
systems offer is sometimes forgotten.
One of the primary ways facility executives can improve HVAC efficiency is to engage in a
benchmarking program that allows them to establish the existing efficiency of an HVAC system
and then measure how changes to the system improve its performance.
The increased application of microprocessor-based controllers on mechanical equipment has
made available additional operating information that allow facility executives to benchmark
HVAC system operation and energy use.
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
1990s 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 available through these networked control systems
is often overwhelming. As a result, the data is relegated to serve as historical operating
information used only for troubleshooting maintenance problems. Limiting the information to
that use, however, ignores the opportunity to improve the overall operation of the HVAC
system through long-term trending.
Benefits of Benchmarking
The operation and maintenance of these systems is typically the responsibility of building
operators. Facility executives 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 used to improve the decision-making process in the
evaluation of potential capital projects. Benchmarking allows facility executives to embark
on a number of different programs to identify energy use and efficiency improvements in the
HVAC system.
Baseline Energy Use
In an increasingly competitive marketplace, costs are a critical driver of corporate
performance. The primary objective of a benchmarking program is to establish 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 becomes useful information as the nation’s electric utilities move toward deregulation.
Continuous Commissioning
Commissioning assures facility executives 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 affect system energy use.
This information can be used to continuously fine-tune system operations, uncover 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 percent. 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 that 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 to 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 bill. A building
model would have to include all energy-using components to use the utility bill data to
validate the model accuracy. This validation method would be of limited value, except on the
largest retrofits, because of 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 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 used to build confidence and support within the organization for funding of
additional capital projects.
An important benefit of monitoring HVAC control systems is the establishment of a benchmark
for plant operations. Facility executives can use this information to identify operational
and maintenance 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 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 a
benchmarking project. Although the process involves time and some level of expertise,
benchmarking is still a low-cost method to gather data that help reduce utility costs.
Joe Watson is a project engineer for E3 Designs. He is responsible for overseeing HVAC
monitoring projects throughout North America.
Energy Decisions Online
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