One of the prime sources of frustration for the facility manager who arrives at work before the arrival of staff, is finding that all the lights have been left on. Despite the repeated assurances of the building automation contractors, the frequency of this event presents a major cost burden in managing a tenancy.

Ironically, the technology designed to eliminate this sort of waste has already been in existence for some years.

Modern electronic ballasts are capable of being connected directly to a control system which, independently of the BAS (Building Automation System), can detect the presence and absence of motion and implement 'daylight harvesting' to reduce the energy and maintenance cost of any modern tenancy.

The major problem in the implementation of the system for the facility manager is in presenting a substantial cost benefit or return over the expected tenancy fit-out life to the management board.

Whilst the investment in a typical energy saving controllable ballast is only around $50, plus the cost of a few minutes labour to install it in the fixture, and the return from each ballast around $20 or more per year, the problem is their placement into the ceiling. The installation and wiring of the ballasts involve major labour costs from the deployment of qualified tradespeople and the associated cleaning costs that go with them.

The solution to the problem has arrived in the form of a wireless remote controlled ballast. This technology has already been implemented in electronic transformers for halogen lamps and ballasts for the smaller metal halide lamps, such as those used in reception areas and podium areas.

By simply changing the ballasts in the existing fixtures, installing a small interface module called a 'bus coupler' into the lighting section of the switchboard and plugging sensors into selected fixtures, it is possible to transform an energy hungry tenancy into an inherently 'smart' and flexible system operating independently from the more rigid BAS system. The sensors are capable of automatically detecting the presence and absence of motion, the amount of usable light already available and also incorporate infrared remote control input points, which act as replacement light switches.

These sensors are configured to interact with the lighting fixtures in the different zones of the tenancy to implement a range of pre-programmed functions. Near the windows, for example, a strategy known as 'daylight harvesting' can be implemented, whereby if there is sufficient natural light streaming through the windows, the rate of energy usage can be drastically reduced. In 'back of house' areas such as archive rooms, lunchrooms and filing areas, presence sensing can ensure that lighting is only active when necessary.

A time clock incorporated in the bus coupler manages the various states that the system will experience over a typical week; namely 'daytime', 'afternoon', 'cleaner' and 'security'.

As well as automatic control, there is a manual over-ride control panel for each wing of each floor. This control panel has 4 push buttons, labelled DAY, AFTERNOON, CLEANER and SECURITY. Pressing one of these buttons will select the initial settings of the lights for these times of day regardless of the current time clock schedule (eg working on Sunday). Control through individual computers is also possible via system tray icons.

Daytime operation

When the DAY preset is selected (either by time clock or manually), the lights fade to pre-programmed initial levels. After a short delay, the PE (photo-electric) function of the sensors will strive to maintain a lighting level that delivers exactly the right amount of light for workers, with minimum energy use. This is achieved by measuring the amount of light in the workspace, and adjusting the lights to deliver the optimum light level.

Afternoon operation

At the end of the normal working day, the timeclock will select the AFTERNOON preset. This preset will initiate a very gradual fade of the lighting towards off in most areas and a basic low level in circulation areas. At the same time the PIR (passive infra-red motion detect) function of the sensors will be activated, ensuring that lights left on in unoccupied areas will switch off automatically. Conversely, the PIR function will prevent lighting from turning off in areas where staff are still present. Areas can be cross linked in such a way that sufficient lighting is left on in circulation areas and lift lobbies to provide a comfortable and safe environment for staff who choose to work beyond normal office hours.

Cleaner operation

The CLEANER preset provides a basic lighting level in circulation areas only and activates the PI function in all other areas. As the cleaners move through the building, the lights will automatically switch to full output in occupied areas while the cleaners are working. The lights will automatically switch off again after a few minutes delay when the cleaners leave each area.

Security operation

The SECURITY preset is similar to the CLEANER preset, except that the lights will switch to a low level rather than full when the presence of a security guard is detected. The lights will switch off again, after a short delay, after the security guard leaves each area. In areas where cameras are fitted, lights will be set to levels sufficient for visual monitoring.

By implementing the 'rules' for the various states, it is possible to reduce the effective energy consumption of the lighting fixtures by up to a third in a well-managed tenancy, and by an even greater amount in a tenancy with no previous control system at all.

Energy savings can be achieved firstly because the ballasts themselves are electronic types and therefore more energy efficient that the traditional low loss iron ballast. For example, a typical fluorescent light fixture in an office (a troffer) contains two nominal 36W lamps and two iron core ballasts. The power consumption of the ballasts and lamps combined is in the region of 91W, if standard ballasts are used. The electronic ballast, on the other hand, only needs to deliver 72W of power to the same lamps to deliver an additional amount of higher quality light. This is an improvement of 19W, or 25%. Lamp life is also extended by around 50%, further reducing cost.

A typical working year, including allowances for early arrivers, late leavers and cleaners, is in the region of 3,500 hours. It is a relatively straightforward exercise to restrict the active hours of lighting use so that the average reduction is in the order of one to two hours per day. Assuming 1.5 hours, a further saving of 12% is achieved. In addition to this, incorporating the presets in daily work practices should deliver a further 10% in savings, giving a possible yield of 47%.

In the scenario above, the fixture with a standard ballast and no control system costs $38.22 per annum, for electricity alone. Our improved system costs $20.25 per year, a saving of around $18.00 per fixture, per year. In other words, the investment returns a positive yield after three years. This is only part of the story.

To the cost savings of an energy management system can be added the productivity and worker comfort gains delivered by the system. In addition to salary and benefits, the real cost of accommodating a staff member includes the cost of the actual office space, company infrastructure and depreciation. The total cost of sitting the staff member at their desk can be several times the staff member's given salary.

In return for this, the employer receives their staff's attendance for approximately 2000 hours per year. It is therefore critical that an optimum working environment is provided and that the staff member is protected against any negative environmental factors, which may have an effect on their productivity. These include headaches and eye strain caused by the constant 100Hz flicker generated by standard ballasts and inappropriate lighting levels for the task at hand.

A rigid BAS controlled lighting system that turns all of the lights off at 5:30 every day, with the inconvenience of phoning the engineering department in order to have them turned back on again, would discourage any staff member from putting in valuable extra hours. Similarly, a 'dumb' presence-sensing system which leaves a staff member alone in a small pool of light, late at night, could be quite threatening.

Wireless networking control systems address these and other problems by giving control of the environment back to the staff members. By providing intelligent presence sensors, local control panels, system tray icons, personal infra-red remote controls and flexible cross-linking of controlled areas, the automatic functions of the system can be temporarily over-ridden by staff at any time and lighting levels easily adjusted to suit the taste of each user.

The initial outlay invested in a wireless networking control system is more than offset by the "comfort" benefits to staff, productivity benefits to the management and the energy savings that can be made.

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