Building Energy Management Systems (BEMS)

By R.W. Hurst, President, The Electricity Forum

Building Energy Management Systems (BEMS)
Building Energy Management System

Building energy management systems (BEMS) are energy management computer control systems that both control and monitor a building’s known as "outstations" around the building, back to the central BEMS computer where building operators can control the building's energy system.
Energy Management Software provides control functions, monitoring, alarms and also allows the operators to optimize building performance. BEMS are a critical component to managing energy demand, particularly in large complex buildings and multi building sites.

Analog and digital input signals tell the Building energy management system what temperature, humidity etc. the building is running at. Inputs might also include whether equipment like pumps, fans and boilers are running or not. Analog/ digital outputs then send signals from the central supervisor PC to valves, pumps fans etc to control their settings or to switch things on and off, resulting in changes to comfort conditions. BEMS can be used to control almost anything and it is becoming increasingly used to control lighting and to monitor critical systems.

This allows the operator to program when things automatically turn on and off and what setting they operate at e.g. temperature, humidity. A BEMS is really a tool for controlling and monitoring the building and a good operator can use the BEMS to optimize settings to minimize energy consumption without compromising comfort and services.

As a core function, a building energy management system would control boilers, heating system, pumps and then locally control the mixture of heat to achieve the desired room temperature. In air-conditioned buildings BEMS would control chillers, cooling systems and the systems that distribute air throughout the building (for example by operating fans or opening/closing dampers). BEMS can also control lighting or any other energy using equipment and can also be used to log energy meters.

Modern systems have distributed intelligence in the outstations and also allow multi-site control with remote monitoring via the telephone network, wireless and satellite systems. They are increasingly becoming connected to hand held devices like palm top devices and mobile phones with alarms that tell on-call staff of problems in the building.

Building energy management systems can significantly improve the overall management and performance of buildings, promoting an holistic approach to controls and providing operational feedback. Energy savings between 10 and 20 percent can be won by installing a BEMS, compared with independent energy controllers for each system. However, these systems cannot compensate for badly designed systems, poor management or incorrect electrical/mechanical maintenance.

Multi-building sites

Building energy management systems are ideal for getting control of multi-building sites and large complex buildings. They are also used by large organizations to control buildings spread across wide areas like whole local authorities, health trusts and even buildings across the whole country. Modern systems have intelligent outstations that can be interrogated locally in a plant room to track down local problems. They can also have wireless connections to some devices to reduce or avoid cabling. A BEMS needs to be well specified and engineered, with good documentation and an intuitive user interface if it is to be used effectively.

In very small buildings it is possible to achieve reasonable control using stand-alone controls for heating, lighting etc and this may be a cheaper option than a full BEMS. However, costs of controls has come down such that mini systems are now competitive and hybrid systems that interconnect a series of local controllers are also available. So, building energy management systems can be considered for controlling almost any size of building but the improvement in management really becomes apparent in large distributed and complex sites/buildings.

Ensuring good user interfaces with a building energy management system is essential. Modern building energy management systems can be accessed in a number of ways (see Fig. 3) for example, through web browsers via the internet, through hand-held tablets and laptops or through palm devices and smart mobile phones. Providing convenient access routes allows building operators to use the BEMS in a way that fits their role and the way they work and encourages them to utilize the system as a building optimization tool. Poor access or a lack of feedback normally result in facilities managers leaving the BEMS sat ignored in a corner of the operations room as a silent controller rather than a window into the building’s performance.