BEMSs that deliver — and continue to deliver
Why is it that so many, if not most, building and energy-management systems fail to deliver. Dr Cedric Rodrigues suggests a host of reasons — and solutions.
Two major system flaws have prevented many building energy management systems from meeting expectations and realising projected lifetime cost and carbon savings. They are inconsistent programming and users with twitchy-fingers tampering with settings, both of which can both lead to suboptimal performance.
The principal intent and expectation of an ‘intelligent’ building energy management system (BEMS) is to control and minimise energy usage, CO2 emissions and costs — whilst maintaining good comfort conditions in buildings.
However building owners often discover that the aspired benefits of their BEMS, so keenly anticipated at the design stage, are seldom realised owing to fundamental problems in the way BEMSs are designed, operated and maintained.
These problems start at the design-to-commissioning phase, get worse in the operational phase and worse still through life owing to lack of preventive maintenance of the BEMS equipment. As a result the original intent or objective of installing a BEMS is rarely achieved.
All building designs call for a controls strategy to deliver optimum building energy efficiency in the form of a detailed written specification. For most BEMSs, this specification has to be translated into a software code to download into the control hardware at the installation phase. It can be two to three years before this happens and the actual system is in use. During this passage of time further controls design changes can occur, including downgrading of the BEMS functionality as overall building project cost cutting often hits the BEMS element the hardest.
During installation, the first problem that arises is that no two controls specialists will program a BEMS in exactly the way specified or, indeed, to a similar standard — leaving significant deviations in the way the hardware operates, which in turn can result in more, not less, energy being used.
There are recommended control strategies from CIBSE and BSRIA, but they are not always adhered to. On complex installations where there is a multitude of energy sources requiring the passing of demands between them, the quality of the programming has to be par excellence to ensure that optimal control strategies are achieved. Owing to time or cost constraints, final refinement or tweaking is left to the on-site commissioning engineer, who is always under pressure to get the BEMS working quickly to meet the building handover programme, as most building projects are late. With little or no time left most of the BEMS control strategies cannot be carefully verified or thoroughly exercised pre- or post-handover — so the BEMS starts life with less than optimal functionality.
Even if a controls system is initially installed correctly, the next reason why a BEMS often fails to deliver its potential is tampering by numerous users. Tampering is a symptom of many causes, from poor building design to comfort preferences or differences between occupants or genders. At the user level, temperature and time set points are fiddled with continuously in the search for optimum conditions. At the plant level, to overcome system deficiencies, changes are made to keep the system operational — often at the cost of extra energy use. The net result is that the intelligent self-adaptive optimisation strategies of a BEMS cannot achieve their goals.
Another hidden problem is the assumption that the critical parts of the BEMS hardware and software will function optimally throughout their design life and require little or no servicing or maintenance. Various diagnostic investigations by the author have shown, for example, that temperature sensors deteriorate and fall outside their calibration accuracy or simply become broken or damaged. Control dampers and valves function incorrectly because of age or wear, temperature deadbands intended to avoid simultaneous heating and cooling are not enabled and free cooling options no longer working, are other problems. Control software can also become outdated, and the high cost of updating the software deters the owner from accessing the latest and best applications, thus exacerbating the situation further.
The net result is that comfort conditions are not met or delivered, with the penalty that energy consumption is increased. After a while the BEMS system no longer serves the intended purpose and is relegated to serving as a glorified time clock — thus failing to deliver the original intention of saving energy, CO2 and cost.
How can these issues be overcome?
First, there is a need to adopt consistent repeatable control strategies from recognised sources such as CIBSE and BSRIA. To avoid specialist programming for every application, all control hardware should be pre-configured and pre-programmed with firmware using recognised strategies. It should be noted that pre-engineered solutions can meet 90% of control applications required for buildings.
Issues arising during commissioning can be overcome using expert, online commissioning tools and remote Internet access or via portable computers. Tamperproof controls will minimise the impact of changes made by users by restoring the system to their optimal settings. Regular diagnostics of systems will identify hardware that is out of calibration, so it can be serviced to restore the equipment to optimal functionality.
The next generation of Internet-based, plug-and-play energy-management systems (such as e-Magine) is with us and can deliver highly flexible control strategies that are tamperproof, repeatable, and are not reliant on programming skills. Fast installation and an ability to commission remotely means less on-site time and cost. Just as important during operational life is the use of online diagnostic tools to quickly identify system malfunctions and refine the control strategies to maintain optimum operation.
With the next generation of BEMSs, there is the added ability of designers, installers and end users to share one common BEMS platform with access to a range of e-apps and the BEMS operating software being the latest version. This ‘one-world’ functionality goes a long way towards eradicating the fundamental issues that prevent many BEMs achieving the primary objectives for which they were specified.
Dr Cedric Rodrigues is an energy consultant and director of Ener-G Controls Ltd.
