Moving forward with low carbon
As we pass the first major deadline for the CRC Energy Efficiency Scheme the focus for many organisations is continued energy-performance improvement. Ant Wilson explains how the building-services engineer can get involved.
In theory, every organisation required to participate in the CRC Energy Efficiency Scheme has by now submitted figures for its carbon emissions and has a good understanding of their energy consumption. And even those that missed the deadline will have to ‘get their act together’ relatively soon if they are to avoid significant fines.
So the next phase, armed with that enhanced knowledge of how the buildings are performing, is to implement measures that will achieve ongoing improvements in energy efficiency. It is here that building-services engineers can play a key role — not just through the traditional service of improving system efficiency but also by taking an holistic view of the whole issue.
Many organisations will now be looking for a combination of quick wins that will deliver results in the next 12 months, combined with longer-term strategies. The latter will be those that require more planning and investment, so they will kick-in during subsequent years.
One of the quickest wins will be behavioural change, essentially making the people who use the buildings more aware of energy issues. This is an old drum that has been banged for many years, but it still needs to be played.
Innovative measures can also be taken with spaces occupied by people with varying needs. In a supermarket, for instance, there will be shoppers dressed for the outside, shelf stackers carrying out physical work and checkout staff sitting still. If the space temperature is set to the suit the customers, the shelf-stackers can be given light clothing and checkout staff issued with fleeces.
One might think that these behavioural issues have nothing to do with building services, but, in fact, there are strong links between behaviour and the configuration of control systems.
A key area to address in this respect is the tendency to over-deliver certain services. For instance, many people working with computers are perfectly comfortable with an illuminance of 200 lux on the working plane. Thus, rather than lighting everything to 500 lux, perhaps we should be looking at a lower illuminance as standard with individual control to increase levels where required, maybe using task lighting. Where this level of control cannot be achieved with existing lighting, it may be cost-effective to retrofit new lighting, especially where there are long hours of occupancy.
Another area is that of controlling services in relation to occupancy. Historically, the tendency has been to base such control on presence which, staying with the lighting example, can often bring lighting on in a room when it is not needed. In contrast, absence-based control enables people to turn on lighting if they feel they need it, and turns the lighting off when people leave the space. In this way, the control strategy becomes more closely aligned to demand.
Another obvious example is that of ventilation. Many older buildings with relatively low occupation density are over-ventilated, which can be addressed by introducing demand-orientated control based on CO2 levels and using variable-speed fans. Reducing fresh-air volumes will also reduce fan power consumption, as well as heating and cooling to temper the air.
All these energy-saving measures require a good understanding of how the building is being used — a key consideration is arriving at a sensible energy-saving strategy. One very quick win would be to open buildings only during core hours, such as 8 a.m. to 6 p.m. Such opening house will hardly going to be acceptable to the majority of businesses, so the strategy often has to achieve a sensible compromise between business needs and environmental ideals.
In terms of business needs, return on investment will also play a significant role. Consequently, understanding the pattern of energy consumption in fine detail is very important.
For example, in a supermarket that consumes 60% of its energy consumption in food refrigeration and 0.5% in running the tills at checkouts, it will be far more cost and carbon effective to achieve a 1% energy saving on refrigeration than a 10% energy saving on the tills.
The key metric, and a good guide to prioritising works, is the cost per kilogram of CO2 to be saved. Very often, these priorities are already flagged up in the high, medium and low impact recommendations in Display Energy Certificate and Energy Performance Certificate reports.
At the same time, it is vital to consider the impact of any proposed measures on the core business. Schools and universities have extended periods of low occupation where major works can be carried out with very little disruption. Hospitals and 24 hour supermarkets, on the other hand, offer very limited windows of opportunity for major works.
These are some of examples of how a building-services engineer can add real value by ensuring that services and the way they are controlled is closely aligned to building usage. Designing flexible, controllable systems, therefore, is essential to achieving ongoing improvements in energy efficiency.
Ant Wilson is director of building engineering with AECOM.
