Environmental Engineering Reference
In-Depth Information
energy use and led to more efficient energy management and control tech-
niques. This resulted in the development of modern energy management
systems (EMS) for monitoring energy usage. These systems grew over the
years in both sophistication and scope.
Another product area appeared in the 1980s called building automa-
tion systems (BAS). These systems included historical data, trend logging
and fire and security functions in addition to conventional energy man-
agement functions.
Direct digital control systems appeared in the mid-1980s and dis-
placed older analog closed-loop schemes for temperature control. These
digital systems improved both accuracy and reliability. The earlier sys-
tems were modeled after existing system architectures and did not con-
tain intelligent, standalone field devices. There were numerous interfaces
to the various building systems and the major decisions were made at a
central computer.
Modern Building Automation Systems (BAS) attempt to limit the in-
terfaces used in order to provide a more seamless, integrated network.
Ideally, all of the various components communicate with each other in a
common language.
Several levels of control are generally used with several levels of hi-
erarchy in a distributed architecture. Each level serves its own purpose,
but all levels are interconnected, similar to the operating structure of a
In building control the controlled parameters include basic functions
such as discharge air temperature, space temperature, humidity and fan
control. The benefits of such a control system in an intelligent, integrated
heating and cooling network include repeatable and individual parameter
or area (zone) control. Individual comfort control has been shown to in-
crease employee output and provide an annual productivity gain of over
$1000 per employee.
Networking takes building automation beyond traditional heating
and cooling functions. Intelligent devices can be tied into the network,
allowing data to be collected and energy usage to be measured. A net-
worked system may also manage lighting, fire and access control. If these
systems are fully integrated, then the expanded integrated control func-
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