A fast and painless route to cutting carbon emissions

Any organisation seeking to reduce its carbon emissions should first take a closer look at its building energy management system (BEMS), says Sean Brook, Energy & Support Solutions Manager at Trend Control Systems Ltd.

Owners and tenants of non-domestic buildings are under mounting pressure to cut their energy usage and carbon emissions. They are faced by the prospect of higher utility prices and ever more stringent legislation, not to mention public and stakeholder demands that they show high standards of corporate social responsibility. At the same time they are being constantly bombarded with information about products that will reduce their energy consumption.

So what should be the first priority for hard-pressed energy and facilities managers? The logical answer is that they should focus on those areas where large energy savings can be made quickly and easily. This will often mean looking no further than their building energy management system.

The principal role of a BEMS is to regulate and monitor heating, ventilation and air conditioning – and often lighting too. It typically controls 60-80% of a building’s energy usage. By applying a range of control and monitoring routines – both simple and sophisticated – it is capable of operating the building services in strict accordance with demand, thereby avoiding unnecessary use of energy. But for various reasons many BEMS are out of synch with their environment and are thus not working to their full potential.

Where does waste occur?
In new buildings loss of energy performance can begin almost immediately. The main reason for this is that BEMS are generally commissioned prior to occupation. A further contributory factor is that commissioning is often the final act before the building is handed over and the BEMS supplier may thus be working to an exceptionally tight time schedule, some might say impossibly tight.

When people move into a building they bring with them a variety of heat-emitting equipment, such as photocopiers and vending machines – and all too frequently these are positioned close to system temperature sensors. In consequence the BEMS increases the flow of chilled air to the area around the equipment, which then leads to overcooling of the surrounding space, resulting in a classic ‘heating fighting cooling’ situation. So within days or even hours of the building opening for business its energy performance is in decline.

As time goes by other factors can cause performance to deteriorate further. For instance, the building occupation times entered into the BEMS may no longer reflect reality. These may have been extended to allow for a longer working day or weekend shifts, but then not readjusted when the normal working pattern is resumed. This far from uncommon occurrence results in the building services being operated at full capacity at times when the premises are empty, which is hugely wasteful of energy.

In addition, many buildings undergo regular repartitioning, usually without any thought for how this will affect control of space temperature. What may well happen is that some areas become overheated and people compensate by opening windows, while other spaces are overcooled – a common remedy for which is to use even more energy by plugging in fan heaters. A similar effect can be produced by the simple act of covering over sensors with posters and wall planners.

Large and immediate savings
The examples described above illustrate how easily energy efficient control can be lost. Fortunately, such problems are just as easily rectified, for little or no cost. However, it is first necessary to carry out a thorough review of the situation in the building and assess what needs to be done to optimise control by the BEMS, a job that is best left to an energy control specialist. Trend, which offers an energy audit service to users of its system, has carried out many such surveys. It has found that energy consumption can be cut by as much as 25% as a result of corrective actions taken during the review visit. The monetary savings that result are typically several times greater than the actual cost of the service.

A survey might also identify how further savings could be made by carrying out more significant changes or additions to the BEMS – like fitting variable speed drives on air handling plant. However, any proposal for additional work needs to be presented as a fully costed business case, with predicted savings and payback on investment.

If energy savings are to be maintained then it is necessary to closely monitor consumption, which will highlight any tendency for energy performance to once again decline. Tools such as Trend’s iMAT on-line monitoring and targeting package offer a one way of achieving this. It is able to continually compare actual and expected usage (taking into account other data such as temperature conditions) and automatically generates a report when the difference is too great.

Maintaining good performance
If necessary, other means can be deployed to quickly diagnose the exact cause of energy overuse. For this purpose Trend recently introduced its IQEYE web-based BEMS performance tool. This is able to check the functioning of the system – including its control loops and sensors – and can also highlight events such as valves becoming stuck open, controls being manually overridden and other potential sources of energy waste.

Used in tandem, iMAT and IQEYE can allow a problem to be identified, diagnosed and rectified in a matter of hours and thus avoid months or even years of energy over-consumption. The earlier example of a photocopier sited beneath a sensor would quickly come to light when using the two tools in concert. While iMAT would spot the excessive energy use, IQEYE would show that a control loop was failing to reach its setpoint – suggesting a fault with the sensor or something else affecting it. A visual inspection would immediately reveal the cause.

Energy and facilities managers are now offered everything they need to get the performance of their BEMS back on track – and then keep it there. Importantly they are able to achieve both a quick win on savings and a long-term reduction in their buildings’ energy consumption and carbon footprint.  Other approaches to cutting carbon emissions should not of course be disregarded, but few if any are likely to have such an immediate effect or make a bigger impact (the payback period for a wind turbine could be well over 50 years). And it is not just older sites and BEMS that will benefit from an energy audit. Since performance decay tends to be most pronounced early on in the life of a building, it is almost never to soon to consider the value of system optimisation.