Understanding the key issues
The control of energy in buildings is generally poor, despite the availability of a range of tried and tested systems, with guidance perceived to be over complicated explains Andy Lewry of the Building Research Establishment.
Building controls, whether stand-alone units or full building energy management systems (BEMS), are designed to provide a comfortable climate for building occupants while consuming the lowest possible amount of energy.
Controls can be used to manage heating, cooling, air-conditioning and lighting systems, blinds, fire and security systems and lifts. They can also be used to collect and display data from meters. Energy information can then be displayed on the BEMS; having good-quality data about actual energy consumption is the key to achieving an energy-efficient building.
Demand-based control is the most energy-efficient approach, which means turning systems off when not needed or, if this cannot be done, then at least turning them down. Energy can account for about 40% of the running costs of a building over its lifetime (Fig. 1). Anything that can be done to help manage this effectively is a benefit to building owners and occupants. Any decision on what to specify should be based on lifecycle costs, not short-term thinking about the initial capital cost.
Controls can be applied equally successfully to a new or refurbished building. A growing trend is greater integration, which can best be achieved through products which use open communication protocols such as BACnet, KNX, LON, Modbus and M-Bus. Remote access is also now possible, allowing a facilities manager or service engineer to interrogate the system remotely and diagnose problems. It may even allow for the plant to be switched on or off for special events without the need to be on site.
The author of this article has previously published a guide — ‘Understanding the choices for building controls’ [1] — that provides simple explanations of various types of controls, what they can do, and where and why they can and should be used — the pros and cons, and how to achieve an effective solution in practice. The process underpinning this can be broken down into the following steps.
1. Understand what controls you already have. [1]
2. Determine your business needs. [1]
3. Determine the functionality required of the controls. [1]
4. Select an appropriate servicing strategy. [1]
5. Match these against a class of BS EN 15232. [2]
6. Ensure the chosen class has the required functionality. [1]
7. Produce a comprehensive specification. [1]
8. Ensure the 10 key issues listed below are addressed.
9. Engage an expert(s) at the stage where internal capabilities are exceeded; this is not something you can learn as you go along.
There are ten key issues to address.
• Specification breaking — procurement routes and ’value engineering’
This is normally a cost-cutting exercise with the temptation to cut capital costs. Stand-alone controls are cheap, in the order of £250 installed, but several will be required. Pre-programmed BEMSs have an installed price of around £1000. But to fully realise the potential savings from energy efficiency, you probably need a programmable BEMS which costs in the range of £3500 to £5000 installed.
• Occupancy patterns — schedules and density
Knowledge of how the building is used improves the estimation of potential savings and, following installation, allows commissioning of the controls to fully realise the potential energy savings. These range, for offices, from a potential of 34% for zonal controls to 54% for a fully programmable BEMs.
• Future proofing — flexibility and upgrades
Technology soon becomes dated and to ensure that your system does not become redundant it needs to be programmable. A programmable system is likely to be flexible enough to take into account changes in usage and can be upgraded to benefit from technological and software advances.
• Links to monitoring and targeting (M&T) — optimisation systems
Energy management relies on the old adage, ‘If you cannot measure it, you cannot manage it.’ This means that the control system (i.e. the BEMS) needs to be linked to the metering, so that all the monitoring and targeting M&T functions can be carried out in the same place, thus allowing management to be instantaneous.
• Verification/certification
To justify business cases it is increasingly important for the performance of new assets, including control systems, to be verified. A fully integrated system can allow collection and analysis of this data, thus allowing this step to be simple and relatively painless.
• Commissioning — initial set-up and an on-going process [3]
It is essential to understand your business and building(s) when producing a servicing and controls strategy. The next step is to ensure that the controls are installed and commissioned to achieve this strategy. However, it is an unending process to resolve operating problems, improve comfort, optimise energy use and identify retrofits for existing buildings and central plant facilities.
• Training [3]
Training is only as current as the last person trained, so, like commissioning, should be an on-going process to ensure that facilities staff, the facilities management (FM) contractor (if you have one) and other users know how to optimise the use of the system. If knowledge is lost, the temptation is to use default systems which leads to inefficiencies and defeats the object of having a customisable programmable system.
• Maintenance requirements — planned upgrades [3]
This runs alongside ongoing commissioning, requiring the hardware to be monitored and upgraded where appropriate. This is especially true of sensors where the system will still run if they are damaged or have drifted due to old age, but not at optimal performance. The likely result is far higher running costs.
• Management reporting
For energy management to be effective, the data has to be presented in a concise manner and in a form appropriate to the audience. What is required for management of the system will be far more detailed than that required for the financial department to reconcile the bills on a monthly basis. Board reports need to be concise and to highlight any issues.
• Additional functionality — critical services/alarms
When managing services you need to ensure that they are delivering the right amount at the right time. Modern systems can be set up to alert key staff by email when services fail to switch off when expected, use more energy than expected or when communications go down. This minimises risk to the business in terms of uncontrolled usage and possible damage to the asset.
Dr Andy Lewry is a principal consultant at the Building Research Establishment and author of a new briefing note ‘Energy management and building control’, on which this article is based. The full publication is available as a free download from the link below.
References
1. Lewry, Andrew J. Understanding the choices for building controls. BRE IP 1/14. Bracknell, IHS BRE Press, 2014.
2. BSI. Energy performance of buildings — Impact of building automation, controls and building management. BS EN 15232:2012. London, BSI, 2012.
3. Lewry, Andrew J. Operating BEMS – A practical guide to building energy management systems. BRE IP 2/14. Bracknell, IHS BRE Press, 2014.
