There's more than athletics to sports
There's more than athletics to sports
Lighting energy consumption in an indoor sports center was reduced by appr. 70% in a recent retrofit in the Swedish city of Gothenburg. The installation of occupancy sensors accounted for some 35% of the total savings, and the sensors paid for themselves in a little less than a year.
The Valhalla Sports Center in Gothenburg has two equally sized halls (referred to as B and C). In hall B all fixtures were to be replaced, while the fixtures in hall C were replaced about five years ago.
The center's B hall earlier was lit by fifty-four 4x60W electromagnetically ballasted luminaires. In 1991, they were replaced by eighty-eight 2x58W, electronically ballasted luminaires. The installation is furnished with occupancy sensors that shut the light off when no one is using the hall, and with a dimmable control system that can be set to provide light at a constant level.
The old installation provided lighting levels of 110 lux, while the maximum lighting levels of the new installation initially are 540 lux. However, the system is set so that the average constant level will be 350 lux. By using dimmers to keep lighting levels constant, some important advantages are achieved: First, since the light output of a fluorescent tube depreciates with age, lighting systems must be overdimensioned to ensure that lighting levels are still sufficient at the end of a fluorescent tube's life. Without dimming, premises are overlit for a long initial time, with an associated waste of energy.
The dimmers now automatically compensate for the reduced light output by gradually increasing the power output. Second, the control system also responds to the daylight, which furhter reduces energy consumption. Another advantage of the dimmable system is that lighting can be adjusted based on the activity; for example, sports events require higher levels than when the hall is used by school classes. The possibility of more actively reflecting daylight into the hall without creating glare problems is also being examined.
The C hall is lit by a combination of a few very old luminaires in fifty-eight 3x58 W fixtures installed 1988, all electromagnetically ballasted. Lighting levels are regulated manually in two steps by switching on half of the luminaires in each step.
Although the two halls are used for about the same amount of hours there was a 60% difference in energy consumption between them: The C hall used 17 020 kWh over a period of 16 weeks, whereas the B hall only used 6 590 kWh. Due to the occupancy sensors, the B hall showed 35% less running hours. If the running hours of the C hall are applied to the previously installed power of the B hall, energy use would have been 19 680 kWh, compared with the 6 590 kWh after the retrofit, a 66% difference.
"When the system is fully commissioned, I am confident that we will come down to the target of 70% energy reduction," says Anders Kjellström, in charge of the project. "Considering that there are halls with older and worse fixtures than those of the C hall, a reduction in energy consumption by up to 80% or more is not at all unrealistic in many cases."
He says that although the occupancy sensors paid for themselves in a year, replacing fixtures is a more costly strategy, with a payback of some 4-5 years, "but when you are about to change them anyway, you should change to efficient luminaires with electronic ballasts."
A demonstration project is planned, in which hall C will be furnished with new, efficient luminaires, control systems as in hall B, improved ventilation, and a power line information carrier system to allow a computer to monitor and optimize the operations of the whole system.
Nils Borg
For more information, contact:
Anders Kjellström Fax: +46 31 16 80 46
| total inst.power incl ballasts (kW) | W/^m | lighting levels (lux) | comments | |
| B old | 16.2 | 16.3 | 110 | measured lighting level |
| B new | 9.8 | 9.9 | 540 | projected maximum lighting level of new installation |
| B new | 7.2 | 7.2 | 350 | average measured lighting level |
| C full | 19.0 | 19.2 | 500 | . |
| C half | 8.5 | 8.6 | 250 | . |