Lighting is one of the large energy consumers in hospitals, just as in many other kinds of utility buildings. Various studies have shown that some 20% of the total energy consumption in a hospital is accounted for by the lighting installation.
When it comes to the energy savings that can be made on lighting, these can be divided into two main categories, each of which is discussed below.
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Smart switching
The fastest savings can be achieved with “smart switching” of the lighting. Lighting is frequently switched on unnecessarily when e.g. there is sufficient daylight or there is nobody in the room. With hand operated systems especially, lights tend to be left burning needlessly.
The advice is therefore to make the greatest possible use of automatic light regulating equipment.
- Daylight sensors
- Presence sensors
- Connection to the building management system (BMS)
- Timers
Efficient lighting
Fluorescent tube lighting (TL) is used a great deal in hospitals. Fluorescent tubes are not only efficient but also provide a good quality of light. Semi-conductor light sources or LED’s are expected to be even more efficient than fluorescent tubes in future, but at the moment fluorescent tubes still reign supreme in tends of light colour, colour preservation and efficiency.
Magnetic ballasts still tend to be used widely in hospitals that are more than 5 or 10 years old.
The second factor that influences the energy consumption is the light fitting, in particular the optics, with the degree of reflectivity of the optics playing an important role. The higher the reflectivity of the fitting, the higher the light emission and the greater the efficiency.
Examples of these are given in the following case study.
Case 1: Replacing conventional magnetic ballasts
Introduction
The hospital in this case is a medium-sized institution with most of the lighting consisting of fluorescent tubes. However, there is no overview of the total energy consumption of the lighting. This makes it difficult to arrive at a precise calculation, but the potential savings can nevertheless be estimated on the basis of reference data.
Present situation
An estimated 70% or so of the lighting is currently equipped with obsolete, conventional magnetic ballasts. As already explained, such magnetic ballasts are responsible for considerable energy losses (around 20%).
Proposal
By using energy-efficient light fittings with electronic ballasts, the ballast losses can be reduced and energy can be saved on the lighting.
Estimated savings & investment
There is no overview of the number of lighting fittings or the energy consumption of the lighting installation. However, based on data from previous studies and from the literature it is estimated that in an average hospital lighting accounts for some 20% of the total energy consumption. For the hospital in the case study this means that some 2 400 MWh of the annual electricity consumption is due to lighting. This value was first verified on the basis of the total floor area, by determining the installed power per m² per 100 lux, which confirmed the estimate.
The savings potential was then calculated as follows:
The percentage of conventional fluorescent lighting fittings with conventional ballasts is around 70%. It was further assumed that 90% of the total lighting consists of fluorescent tubes. The majority of the fittings have white enamelled reflectors.
| Total energy consumption of the lighting : | 2 400 MWh/year |
| Power consumed by fluorescent tube lighting (90%) : | 2 160 MWh/year |
| Losses in conventional ballasts : | 20 % |
| Percentage of light sources with conventional ballasts : | 70 % |
| Estimated number of fluorescent light sources with conventional ballasts, on the basis of 58 W per tube : | 4 000 |
| Total energy consumption of conventional fluorescent lights | 1 780 MWh/year |
| Potential savings by fitting electronic ballasts and efficient optics | 26 % |
| Total savings potential | 462 MWh/year |
The annual energy savings amount to 462 MWh/year, or a financial saving of €37000 per year. From this it can be seen that considerable savings can be made on lighting, although the investment costs are very high.
If the investments have to be repaid solely on the basis of the lower energy consumption, then we arrive at a payback time of between 6 and 9 years, assuming that the existing light fittings are replaced by new ones.
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Edvard Csanyi
Hi, I'm an electrical engineer, programmer and founder of EEP - Electrical Engineering Portal. I worked twelve years at Schneider Electric in the position of technical support for low- and medium-voltage projects and the design of busbar trunking systems.I'm highly specialized in the design of LV/MV switchgear and low-voltage, high-power busbar trunking (<6300A) in substations, commercial buildings and industry facilities. I'm also a professional in AutoCAD programming.
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i want to more energy efficicent light sysytem in chemical opearion plants
I’m all for energy effiency, however I wouldn’t be so quick to write off magnetic ballasts solely on their higher energy consumption, which can be as low as 3 watts more than an electronic version. We do a lot of maintenance on electrical installations and we have observed a noticeable difference in the failure rates of electronic ballasts over magnetic ballasts, with the electronic having the larger failure rate. I believe this is down to their narrow voltage tolerance (no evidence to support this other then observation). Currently I would be slow to replace functioning magnetic ballasts with electronic version just as an energy saving measure, when repairs due to ballast failure may erase any overall cost saving.
Also, I currently have a preference of adsence over presence as a means of lighting control as this requires a person to actually bring on the lights themselves rather than it coming on simply because they’re in the room. This means that a persons quick in and out of a room to retrieve something doesn’t result in the lights running for 20mins