Building Automation: A Carefully Orchestrated Symphony
Mechanical engineers have an in-depth understanding of HVAC and plumbing. Electrical engineers understand power systems. And technology engineers intimately understand technology systems. But building automation system (BAS) engineers and integrators understand how all these disparate systems operate in unison to deliver occupant comfort, energy efficiency, ease of maintenance and lower life-cy...
Mechanical engineers have an in-depth understanding of HVAC and plumbing. Electrical engineers understand power systems. And technology engineers intimately understand technology systems. But building automation system (BAS) engineers and integrators understand how all these disparate systems operate in unison to deliver occupant comfort, energy efficiency, ease of maintenance and lower life-cycle costs.
BAS engineers and integrators are charged with harmonizing the functions of discrete building systems. They understand complex interoperability issues associated with building systems.
Beyond simply achieving system interoperability, however, BAS engineers strive to increase simplicity by eliminating duplication of functionality. For instance, a motion sensor that runs the lights can also be used to control the HVAC system.
But before a facility can achieve true automation through systems integration, it is necessary for BAS engineers to lay the groundwork. They begin by first gaining a clear understanding of the owner's project requirements (OPRs). This information is necessary to simplify, synergize and integrate BAS so that its function meets the facility owner's expectations.
Synergy and integration
Achieving synergy and integration spells the difference between a building that works and one that simply boasts a lot of technology.
Integration not only encourages system optimization, but also offers designers a way to beat the energy code—ASHRAE/IESNA Standard 90.1-1999—by 20% to 50%. It's often written into the design intent and can be vital to achieving Energy and Environmental Design (LEED) credentials.
And energy conservation, through well-planned and designed controls and advanced technology, can reduce energy consumption without sacrificing the occupants' creature comforts. It is critical that the BAS engineer achieves the proper balance of comfort and energy efficiency.
The latest functional approach is to integrate various building systems with local area networks (LANs), wide area networks (WANs) and virtual private networks (VPNs) over the Internet. This increases the flexibility and ease with which occupants and operations and maintenance (O&M) staff access and manipulate the building systems.
Using an IT infrastructure or enterprise allows all computers on a network to have limited to full access and control of the various building systems. The advantages of this type of integration are far-reaching, including remote monitoring of systems from home or on the road through web-based access.
Another advantage of integrated BAS is that the training required for operation is greatly reduced when compared to traditional building control systems. Graphically represented monitors and controls use standard browser software packages that offer a more intuitive human-machine interface. Real-time graphical representation of variables also allows simultaneous observation of multiple inputs and outputs.
There is always the issue, of course, of operating protocols. Building systems often use proprietary operating and communication languages. True integration is the proper application of protocols using protocol standards and translators to communicate between the various vendors' equipment. Three of the most common "open" control system protocols for building systems are LON, BACnet and Modbus.
The BAS engineer must fully understand the building systems' interoperability needs with respect to OPRs. Using the OPRs, the engineer should design a consolidated BAS with open protocols so that systems that use proprietary languages may be integrated and may successfully communicate with each other for full interoperability from a single interface. The open protocol of a properly designed control system anticipates advances in technology and allows additional controls and systems to be added and existing systems to be upgraded with minimal effort. They should be integrated with maximum compatibility, even if the manufacturers and software vary.
Consolidated controls design allows the various systems to share data, which improves the interoperability of building systems. For instance, the building access system instructs HVAC and lighting systems when the building is occupied, or fire systems control CCTV systems that are programmed to automatically check and verify the existence and location of a detected intruder or fire. With a consolidated BAS, specific zones may be heated, cooled or lighted depending upon environmental inputs such as temperature, humidity, occupancy or scheduling. The BAS encourages interoperability, allowing systems to exchange information and to adjust their operation accordingly.
The alternative is independent building systems that are unable to communicate with one another, preventing effective building operation. This could mean that cool, north-facing rooms, even though they are empty, might continue to be heated and illuminated. The lack of occupancy sensors integrated into the lighting and HVAC control systems will require that someone must turn a light switch off or dial a thermostat down.
Like the conductor of an orchestra, a consolidated BAS directs its musicians to come together as a unified musical ensemble and perform in harmony.
BACnet Web Services Addendum
Simplifying access to building energy and performance data is the goal of a proposed addendum to the ASHRAE BACnet standard.
The Standard 135 committee proposed Addendum 135-2004c for public review at the ASHRAE 2004 Annual Meeting. The proposed addendum specifies the use of "web services" to provide a means to integrate building automation and control systems with other enterprise computing applications.
Web services provide computer-to-computer applications with many of the same advantages that the World Wide Web provides to human-to-computer information access, according to Bill Swan, committee chair. Potential uses of the technology include simplifying access to building energy and performance data for inclusion in spreadsheets and other management reports; accessing equipment run-time data for use by maintenance management systems; allowing tenant control of space temperature setpoints; and coupling of room scheduling with ventilation and comfort control.
The proposed addendum is in two parts. The first proposes an Annex M to BACnet that defines the BACnet Web Services interface, BACnet/WS. This nterface is intended to be communication "protocol-neutral" in that the defined web services can be used with any underlying protocol including BACnet, Konnex, MODBUS, LON or legacy proprietary protocols. This has been accomplished by defining how to read and write the common elements of all building automation and control systems such as values, schedules, trend logs and alarm information, using services such as "getValue" and "setValue" that use a simple "path" to define the intended data source. An example of such a path would be: "/ABC HQ/Conference Room A/Space Temperature."
The proposed addendum also provides powerful mechanisms for "localization" where certain types of data such as time, date and numbers can be formatted according to local custom and language, according to Swan. Text names and descriptions may also be accessed according to the local language.
The second part of the addendum contains an addition to BACnet's Annex H, combining BACnet networks with Non-BACnet networks, that prescribes how a gateway should be constructed to translate web service requests specifically to and from BACnet messages.