Open-access content Tuesday 17th May 2016
19 May 2016 | By Dr Andy Lewry
Energy control in buildings is generally poor, despite the availability of a range of well-tested systems, as guidance is perceived to be overcomplicated, says Andy Lewry
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 use 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, at least turning them down. Energy accounts for about 40 per cent of the running costs of a building in its lifetime. Anything that can be done to help manage this effectively is a benefit to owners and occupants. Any decision on what to specify should be based on life cycle costs, not short-term thinking about the initial capital cost.
Controls can be applied equally to new or refurbished buildings. A growing trend is greater integration, which can best be achieved through products using open communication protocols such as BACnet, KNX, LON, Modbus and M-Bus. Remote access is also now possible, allowing an FM or service engineer to interrogate the system remotely to diagnose snags. It may even allow for the plant to be switched on or off remotely for special events. Within energy management systems, the FM should address the following issues.
1. Specification breaking
This is normally a cost-cutting exercise with the temptation to cut capital costs. Standalone controls are cheap, in the order of £250 installed, but several will be required.
Pre-programmed BEMS have an installed price of about £1,000. But to fully realise the potential savings from energy efficiency, you could need a programmable BEMS, which costs in the range of £3,500 and £5,000 installed.
2. Occupancy patterns
Knowing how the building is used improves the estimation of savings and, following installation, allows commissioning of the controls to fully realise those energy savings. These range, for offices, from a potential of 34 per cent for zonal controls to 54 per cent for a fully programmable BEMs.
Technology soon gets old 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 use and can be upgraded to benefit from tech and software advances.
4. Monitoring & targeting
Energy manage-ment relies on the adage 'if you cannot measure it, you cannot manage it'. This means that the control system (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.
To justify business cases it's vital 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.
6. Setup and process
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. But 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 is only as current as the last person trained so, like commissioning, it should be a continuing process to ensure that facilities staff, the FM contractor and other users know how to use the system properly.
8. Maintenance: planned upgrades
This runs alongside ongoing commissioning, requiring the hardware to be monitored and upgraded as appropriate. This is especially true of sensors where the system will still run if they are damaged or have drifted owing to old age, but not at optimal performance.
9. Management reporting
For energy management to be effective, the data has to be presented in a concise manner and in a form suited 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 each month. Board reports need to be concise and should highlight any issues.
10. Proper function
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 article is based on a briefing - Energy Management And Building Controls. Download it free at: www.bre.co.uk/energyguidance.
Dr Andy Lewry is a principal consultant at the Building Research Establishment