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The Cornell EMCS is the result of an evolutionary development that began in 1964 when a manual monitoring and control system was installed to oversee the newly constructed central chilled water system and the several buildings it served. During the next decade, additional building systems were added and the chilled water plant operators, who also manned the EMCS, were able to monitor and control the on/off status of several hundred fans and pumps in about a dozen buildings. The manual system was computerized in 1975 through the addition of an IBM System/7 mini-computer. In 1977, an upgraded computer allowed, for the first time, access to digitally-encoded analog information (temperatures, pressures, flow rates, etc.) from both building and utility systems. The new computer was also user-programmable and permitted us to begin to develop our own application software. We began to use the computer to monitor chilled water data in 1980.

The "modern era" really began in 1984 with the installation of our first direct digital control (DDC) system in one of the dormitories. This was quickly followed by the replacement of the IBM system with a DEC MicroVAX which eventually evolved into the VAXcluster that remains the heart of the EMCS today. Through the years, support was added for numerous DDC types and today the system concurrently supports nine distinct communication protocols, all accessible through a common user interface.

Hardware Architecture

Here is a summary of the EMCS field hardware deployed in 130 buildings:

Device Type Devices Points
BACnet 5708 339268
DSC-8500 9 1298
FP-93 166 1758
CIU 2 340
DX-9100 13 254
EthernetIP 10 4062
Historian 2 4317
Metasys 83 108072
MODBUS 40 277

This conglomeration of field equipment supports access to approximately 110,000 sensors, actuators and software parameters viewable via nearly 700 graphic displays. Because the EMCS is a node on the Internet, it can be accessed remotely by any authorized user with appropriate software.

Software Architecture

The VAX computers run Compaq's VMS which is a secure multiuser, multitasking operating system. The core application is called the Condition Processor (CP). CP schedules the execution of various tasks based on the occurrence of time- or event-based conditions. These tasks perform field I/O for data logging and alarm evaluation and system self-diagnosis to ensure reliable operation of the EMCS as a whole.

EMCS Functions

The primary functions of the EMCS are metering, monitoring, and interactive control. Although the EMCS meters some steam and electricity, these utilities are still mostly tracked via meters that must be physically visited and read. The EMCS is, however, the primary means of tracking chilled water production and distribution. We currently collect steam, electricity and chilled water data from 83 locations around the campus and, for many of these locations, have readings on-line that go back 17 years. This information is fed into our Utility Data System in order to bill the responsible campus departments and for performing various energy analyses. Monitoring is done both passively, by routinely observing system operation on an occasional basis, and actively, by responding to any of the more than 3,000 computer-generated alarms that are currently defined. In addition, operators can interactively make adjustments to binary and analog parameters (setpoints, alarm limits, schedules, interlocks, etc.), DDC programs, and physical output points that control motorized fans, pumps, dampers and valves.

The Future of the EMCS

The next generation of EMCS will be based on a more distributed computing and networking architecture and the use of web-based technologies for user interaction with the system. The distribution will involve developing a set of "front-end" processors that will each communicate with a dedicated set of field hardware using that hardwares communication protocol. These processors will carry out the routine polling of field equipment status and the collection of time-based metering data. They will also respond to change-of-value notifications and pass them on to the central EMCS computer for further evaluation. The various front-end processors will communicate with the central computer via the Internet Protocol. Future field equipment will either use an existing protocol or the new ASHRAE standard protocol BACnet, developed, in part, by Cornell personnel. The new EMCS will feature a dedicated, secure web server that will meet most user access needs.