Taking control of wasted energy

For a variety of reasons, many building operators are looking for quick win energy saving solutions that require minimal capital investment but deliver a reduction in energy consumption within a short space of time and with a fast payback. Upgrading the lighting, either by retrofitting new light sources to existing fittings or by replacing fittings, is an obvious thing to consider. However, it needs to be done properly, and the lighting needs to be controlled effectively if the maximum benefits are to be achieved.

For many end users the main driving force is the rising cost of energy, and this may be further reinforced if they qualify for participation in the Carbon Reduction Commitment Energy Efficiency Scheme. In the latter case they will, effectively, be taxed for any energy they waste.

Or they may be undertaking a refurbishment and are required to introduce energy-saving measures under the consequential improvements imposed by the Building Regulations Part L 2B. Again, making the lighting more efficient in other areas of the building will help to achieve this. And, of course, they may have a commitment to reducing environmental impact as part of a Corporate Social Responsibility strategy.

On top of these considerations is the obvious imperative that the coalition government has confirmed it intends to support the previous target of an 80% reduction in carbon emissions by 2050, compared to the 1990 baseline. If this is to be achieved considerably more needs to be done to improve the energy performance of our existing building stock. In fact, it will be more important to take these energy saving measures even further than in the past, because we are continually adding to the building stock and we need to be sure we’re not adding to our problems at the same time.

Furthermore, with the growing use of technology in homes and businesses, we are putting more pressure on our electrical generation capacity. In fact, if we don’t get the demand under control pretty soon, we could be struggling to meet that demand by as early as 2015.

Reduce consumption

So there are many reasons for reducing the electricity consumption of existing buildings and it makes sense to ensure that any such measures deliver their full potential. On the lighting side, one of the dangers that needs to be addressed is the perception that switching to a newer lighting technology is sufficient to bring about significant savings.

Which is certainly true in many cases, but that isn’t the same as ‘job done’. It’s rather like leaving a hot water tap running because if lighting is on at full output when it’s not needed, energy is being wasted. So control is of the essence and while this is addressed in the Building Regulations for new buildings there is no such compulsion for existing buildings, unless a major refurbishment is involved.

For example, it may be possible to replace a 35W halogen spotlight with a 7W LED lamp and certainly there will be an immediate reduction in installed electrical load. However, failing to control that LED source is still wasting energy, albeit there is less wastage than failing to control a halogen lamp.

At the same time, given the quick win scenario, it will often be necessary to ensure that any such control is easy to fit, inexpensive and simple to operate. The simplest form of control is to train staff to turn the lighting off when it’s not needed but we all know in reality that doesn’t work on its own. However it’s also very simple to introduce occupancy control or daylight control to a space and achieve up to 60% energy savings, compared to on/off switching as the only form of control.

In these cases, the lighting tends to be controlled in relation to a particular space, but a building is really just a collection of spaces, so by applying the same principles to each space the whole building can be controlled through very simple measures.

Here, the key is to understand the lighting requirements of each space to get it right.

Thus an open plan office may benefit from daylight control at the perimeter (perhaps combined with occupancy control) and occupancy control on its own at workstations deeper into the space. In contrast, corridors can combine dimmable light sources with occupancy sensors so the lighting is dimmed to, say, 10% or 20% of full light output when the corridor is unoccupied and ramped up to full output as soon as presence is detected.

However, local control in individual spaces won’t suit all building operators as they may have a need for a centralised lighting management system capable of interrogating individual luminaires or groups of luminaires via a network. This enables monitoring of key performance data such as lamp hours run, as well as providing the opportunity to test emergency lighting automatically. Such systems can also be used to reconfigure lighting without changing the hard wiring.

Converging controls

Taking this principle a step further, it’s possible to introduce even greater convergence by linking lighting with other services – such as heating, ventilation and air conditioning – through a building management system. Such convergence recognises that all of these services have the potential to impact on each other, so joined-up control needs a joined-up approach.

For instance, a control system may operate automatic blinds to reduce solar heat gains and minimise the operation of the air conditioning system. Reducing natural daylight, though, will increase the demand for artificial lighting so there is a balance to be achieved and a central system will enable this to be monitored and controlled effectively.

Understanding actions

Returning to the concept of lighting retrofits, if halogen lamps are replaced with LEDs there will be an immediate reduction in heat output from the lighting system. This may increase the demand for space heating in the winter and reduce the demand for comfort cooling in the summer. So it’s important to understand the implications of such actions.

Clearly, then, a central control system offers a number of benefits but it’s important to future-proof the system and not get bogged down with proprietary systems. It’s far better to opt for an open network protocol such as TCP/IP KNX or LON to ensure future flexibility. In our experience, TCP/IP protocol offers the maximum flexibility.

In parallel, when retrofitting light sources (and switching to LED from halogen or fluorescent is very popular at the moment) it’s vital to consider the light distribution. The photometrics of an LED light source are very different to those of a fluorescent lamp, so it’s important to understand the differences and ensure that any LEDs that are specified are properly designed and engineered. In this way light distribution is controlled more effectively as well as how long the lighting is used for.

Bringing all of these factors together, with efficient light sources and photometrics and sensible controls, there is great potential to address the electricity consumption of our existing building stock. Building services engineers have an important role to play in ensuring that end users get the best solutions.