LEDs are more than just a little bit of light. Many lighting equipment manufacturers have adjusted their product portfolios very quickly in the direction of LEDs, and traditional types of lighting equipment are increasingly being pushed backstage. One of the most important markets for LED lighting devices is the industrial sector. Here, the competition is fierce. The huge industrial plant, with extensive production, scheduling and storage areas, is expected to bring many attractive businesses.
Lighting in industrial environments must improve safety and productivity. It must also improve employee happiness, especially one thing to keep in mind: efficiency. However, in the face of such demanding requirements, how can lighting design succeed? Where is the stumbling block? Is the technical data provided by the supplier sufficient to meet this requirement?
Lighting concept
The basic concept of lighting for large industrial facilities mainly includes horizontal surface lighting. In this way, the minimum requirements of “Workplace Technical Regulations” or related standards (such as EN 12464-1) can be met, while the number of lighting equipment can be kept as low as possible.
In high-bay warehouses, the preference is to choose a concept that can ensure good vertical lighting at the front of the shelf and the distance between the lamps should be as large as possible. For this reason, many manufacturers provide various illuminators with different light distributions due to lenses and mirrors. The wide beam of large surface, the medium beam downlight which overcomes the height of the hall, or the narrow beam of overhead lighting. In addition, depending on requirements, it is also possible to choose between a single luminaire or a continuous row arrangement.
Now back to the core argument supporting LED lighting: efficiency. Marketing statements such as LED solutions using LEDs can save up to 50% of the energy required by traditional lighting equipment, which has taken root in the minds of many designers. It is related to terms such as combined use efficiency and amortization time. But is there a clear and unified definition of these arguments? Are these arguments convincing? Needless to say, LEDs are one of the most efficient light sources and we cannot imagine without them. Nevertheless, it is worth studying some product details carefully, especially for specific applications. Before deciding whether to support the LED lighting concept, what information do we need to know about the luminaire?
Luminous efficacy
For the designer, the light distribution curve (LDC) and luminous flux (lm) of the luminaire are the main parameters of his work. Low power consumption (W) of course also makes lamps interesting. Usually, the luminous efficiency (lm/W) will receive attention. We should study it carefully. Unfortunately, there are many products that do not provide lighting effects, but provide module effects of LED chips, or mix these two values together. The situation will become clearer if we consider the photometric data that can be used in the light calculation program for lighting data recording.
lifetime
In addition, when calculating amortization, life (Lx By) is usually considered. This does not indicate the time when the LED luminaire completely fails, but we have obtained information about the percentage (y) of the LED luminaire whose performance has fallen below the x percentage of luminous flux. L80 B10 = 50.000 h means that after 500,000 hours of working time, the luminous flux of 10% of the LED lamps is statistically lower than 80% of the initial value.
Please note that this only applies to an ambient temperature of +25°C and does not indicate a failure rate. These figures also do not indicate to what extent the above-mentioned 10% luminous flux actually drops. In addition, the luminaire is considered as a whole. This means that, in this case, the visually perceptible failure of a single LED module in the luminaire is evaluated as a decrease in the overall luminous flux of the luminaire, which is not a failure in itself.
It is important to know that the indicated life span is not based on measurement results during actual working hours of up to 500,000 hours, but on calculated results. IES TM-21-11 describes the procedure for extrapolating the lifetime of LEDs measured according to LM-80-08. The data is based on the number of at least 10 test subjects, which have to withstand at least 6,000 hours of running time.
In addition, the manufacturer can choose the threshold value of the luminous flux (x) and the percentage share (y) of the module, which can be changed a lot, such as L80B50: 40.000 h or L70B10: 30.000 h. Therefore, comparison between products is more difficult.
What role do environmental conditions play?
The ambient temperature of +25°C has already been mentioned. Relative to this temperature, all detailed information about the luminous flux of the luminaire is provided, whether it is conventional technology or LED technology. However, it is in industrial facilities that environmental conditions deviate from these values. Depending on the type of production, high ambient temperatures (even higher than +60°C) may occur. In some areas where lighting is installed, it is impossible to prevent the lamps from being seriously polluted by dust particles, oil vapor or chemical substances. What does this mean for new lighting fixtures with LEDs?
High-performance LEDs generate a lot of heat when they are turned on and must be released. If the cooling body is contaminated and the ambient temperature is high, the heat cannot be reliably released into the surrounding environment. This inevitably leads to a decrease in the luminous flux of the luminaire. Many manufacturers try to compensate for the loss of luminous flux caused by pollutants by providing comprehensive housing solutions, and to make the design of the luminaire body meet these requirements.
Therefore, a specially designed heat sink can ensure air flow through the lighting equipment. We often talk about the so-called stacking effect. However, even this system does not always work. The lubricant film emitted from the oil vapor in the environment will inevitably be deposited between the heat sinks and damage heat dissipation. Since the space in the structure is very small, this type of system is also difficult to maintain.
Even a well-thought-out lamp design cannot prevent, for example, an increase in the temperature of the housing. In addition, it contaminates the light-emitting surface itself. Despite all claims to the contrary, LED lamps also require maintenance.
But how big is the actual impact of ambient temperature? The figure below clearly shows that the luminous flux of the LED high-bay luminaire directly reacts to small fluctuations in the ambient temperature.
Conclusion: Be cautious about broad statements.
Luminous efficiency and lifetime are important indicators of the efficiency of LED luminaires. However, especially when it comes to the lighting of industrial facilities, it is impossible to point out the standard value of cost savings. The decision to adopt LED technology does not automatically mean that energy consumption will drop by 50%. Environmental conditions have a great influence on the luminous flux of the luminaire and the subsequent luminous efficiency.
If the luminous flux drops, the required minimum illuminance may no longer be reached. As a result, the number of luminaires must be increased or maintenance intervals must be shortened. This means increased purchase and maintenance costs, and longer amortization time for investment in lighting equipment. Here, the most important thing is that the designer must be familiar with the hotel’s environmental conditions and consider its impact on the selected LED lamps.
