Give your luminaire a call
Give your luminaire a call
An Irish central-lighting energy-management system lets users have their say - by calling the central computer on the phone!
The system offers a way of centrally switching off lights reliably at the end of normal working hours and providing ambient daylight-level linking, while retaining local control.
The system has been tested in one of the central-management buildings at University College Dublin, with support from the European Union's Thermie Programme.
WIRING COSTS KEPT DOWN
To keep costs down, the system designers deemed it essential that extra wiring for the control of lighting circuits be kept to a minimum. To minimize wiring, each office room had its lighting circuits wired to a local receiver connected to a dual tone multifrequency receiver (DTMF) control station via a simple twisted pair cable.
The DTMF control stations are linked to the existing building energy management system's high-speed network. The DTMF control stations are interfaced directly as extension numbers to the university's telephone network in order to allow users to communicate with the system using their office telephones.
The DTMF station is a compact electronic unit with speech synthesis, to instruct the user by voice, and a decoder that interprets telephone key presses by the user. In the building monitored, the system allows the occupants to switch their lights on or off for a period of 1 to 6 hours, using their telephone. A photocell is used to measure the ambient daylight level, and each office has a threshold light level which, if exceeded, causes the system to switch off the lights in that office. If they wish, users can override this command by using their telephone. The daylight level can also be set to meet individual needs for each office room.
It is claimed that the system can continually optimize the use of natural daylight while still allowing users local control via their telephone. The system also ensures that lights turn off automatically, according to a pre-programmed schedule, following the end of normal working hours. Janitors and other persons that regularly work at night have a code that allows lighting to be turned on in a given zone for a maximum of 2 hours at any given time.
A central computer allows engineers to check and set lighting levels in each zone. But in the event of failure the telephone-system lights can be operated manually. The computer also monitors lighting energy and calculates costs. The DTMF system need not be restricted to the control of lighting. In this project occupants were also able to adjust the temperature of their office ventilation equipment.
ENERGY SAVINGS AND COSTS
Without the use of the DTMF system the energy consumed by lighting in the building was estimated to be about 116000 kWh per year. By contrast, the monitored energy use with the DTMF controller was about 44000 kWh, which translates into a saving in electrical energy of about 72000 kWh per year, or more than 60 percent. This energy saving is equivalent to a monetary saving of ~US$11500 per year, assuming a cost of 16¢ per kWh.
However, such large savings are not typically the result of control systems only, and in many other applications the savings are likely to be less. One explanation is that the test site had no previous control system. "Another explanation is that all offices can take advantage of ambient daylight. And the system also encourages people to decide whether they should have their lights on or not." says Sean Giblin at Cylon controls.
The total capital investment cost of the system was ~$28950, of which the equipment costs were ~$9650 and the installation costs ~$19300.
As there is virtually no maintenance required for the controller, the annual maintenance cost is considered to be zero.
In the demonstration installation, the simple payback time is estimated to be ~2.5 years. However, the equipment cost is based on low production volumes. If the product realizes its marketing potential the unit cost would decrease and so would the payback time.
Although tested on the university administration building, the application is not restricted to office buildings. In fact, project managers claim that the controller can be used in most commercial buildings, including schools, hospitals, colleges, rest homes, and hotels.
It remains, however, to be seen how well the system will perform on the market. Its success will depend as much on the technology itself as on how it will interact with local culture and usage patterns.
Nils Borg
Contact:
Mr. Sean Giblin
Cylon Controls Ltd., Unit 8 IDA Enterprise Centre East Wall Road, Dublin 3 Ireland
Tel: +353 1 836 66 26
Fax: +353 1 836 51 08
Note: This article is based on an article by Mike Trim, Brecsu/BRE, UK.