Building Automation/Introduction

Chiller plant automation - User interface

A Building Automation System, also referred to as BAS or Building Management System (BMS), is a combination of software and electronic, electric and mechanical devices, meant to automate the operation of a building.

At a very high level, it can be described as a system that collects information about the building status and the factors that affect it (like the weather), processes it, stores it, informs the operators, makes decisions (based on current, historical and forecasted information, plus the operators input), and acts to control the building electromechanical equipment.

Operation

The Building Automation System actions are usually intended to maintain the building safe, healthy and comfortable for its occupants, while minimizing the energy use and extending the equipment life.

The information collecting, processing and decision making is in most cases distributed among different devices, which can be interconnected for coordination. Some of these devices can be factory mounted (or embedded) in the mechanical equipment they control, while others are installed in the building.

A device that makes decisions is usually called a controller. Its biological equivalent is a brain. The devices that collect information are called sensors, which are equivalent to the senses. The devices that act to control the equipment are called actuators, which are equivalent to muscles. The information from the sensors to the controller and from the controller to the actuators travel over communication channels, which are usually wires but can be fiber optics, radio signals or complex networks. Such communication channels are equivalent to the nerves.

The sensors and actuators can sometimes be embedded in the controller. An example of a simple controller with embedded sensor and actuator is a bimetallic room thermostat. It senses the room temperature, compares it against what the occupants set as comfortable, and then switches On and Off heating or cooling equipment to maintain the temperature acceptable without damaging or wearing unnecessarily the equipment. A more sophisticated thermostat would also keep track of time and detect if the room is occupied to then use different setpoints, and even sense and control humidity.

Subsystems

A Building Automation System can be subdivided in several subsystems, which in a large buildings may be provided by different companies. Some of them are:

Building Monitoring System (BMS) – Collects information, process it, stores it and reports it to the building operators.
Building Control System (BCS) – Usually integrated with a Monitoring System in a BMCS or SCADA, allows the operators to remotely control devices.
Building Automation System (BAS) – Usually including the BMCS, it makes decisions using current, historical and forecasted data, as well as the operators input. The decisions may be taken by devices as simple as bimetallic thermostats or as sophisticated as extensive software running in servers outside the building.
Building Energy Management System (BEMS) – Defines high level strategies meant to reduce the building energy use. These strategies usually involve the coordination of multiple pieces of equipment, as in Load Shedding, Energy Storage Management, Demand Response, Free Cooling, and Scheduled Setback.

Another way to subdivide a Building Automation System, is by the systems it controls. For example:

HVAC Automation –Maintains healthy and comfortable indoor temperature, humidity and air quality.
Lighting Controls –Maintains the illumination levels required for the activities and occupation level of each area.
Fire Detection and Suppression – Detects, reports and suppresses unwanted combustion events in the building.
Access Controls – Limits access to different areas of the building only to authorized people, as well as detects and reports intrusions.
CCTV controls – Responsible for identifying the relevant video feeds, then showing them to security staff as well as storing them.
Elevator & Escalators Controls -