As energy, raw materials and labour become more expensive, staying competitive can be helped by saving in ways that do not harm the quality of production or services provided. One of the areas where it is possible to find significant savings is lighting.
Depending on the type of lighting fixtures in use, up to 80 percent of electrical energy can be saved. It is especially important to save energy where there is a lot of lighting and it is used for several shifts or all day, in production facilities, warehouses, greenhouses, logistics centres and shopping centres.
First step – a lighting project
When building or reconstructing a structure, a separate project is done for the lighting. Before preparing the project, criteria are defined for the lighting project. The main parameters are the Colour Rendering Index (CRI), the level of lighting (lx), the longevity of the light source, its compatibility with lighting management systems, efficacy requirements (lm/W) and a multitude of smaller, but no less important parameters.
Having specified the right criteria, it is possible to survey suppliers or announce a tender. Lighting projects are usually prepared by the companies offering lighting solutions. The companies choose the most appropriate lighting fixtures, taking into account the survey or tender conditions.
When specifying the criteria for the lighting project, it is necessary to pay attention to three main things: the type of light source, the construction of the lighting fixture and its electronic component.
Type of light source
In order to analyse all the most popular types of light sources, we will use the method of reasonable process of elimination, leaving at the end only those light sources which, with respect to technical parameters, are the most appropriate to use for industrial lighting.
Colour Rendering Index
Because in this article we discuss indoor lighting first, the first parameter which we should evaluate is the Colour Rendering Index.
The Colour Rendering Index expresses the quality of light. For example, many people have noticed that under ordinary yellow lighting in the street, it is impossible to identify colours. This is because the high-pressure sodium lamps used for street lighting radiate light in a very narrow spectrum which lacks the full range of colours. Objects lit by such light become colourless.
Below we see a comparison of how coloured objects lit by an incandescent or halogen lamp (1), a high-pressure sodium lamp (2) and a metal-halide lamp (3).
1) 2) 3)
Below we present the light source classification according to Ra values:
Sodium lamps and high-pressure mercury lamps are categorised as light sources having a poor colour rendering index, therefore they are appropriate for use only in street lighting and open spaces.
One of the main parameters determining one’s selection is undoubtedly efficacy, which is measured with a relative index, lm/W. This parameter specifies how much light is produced using one watt of electricity. In the table below, we compare the efficacy of the most popular lighting sources.
It is obvious that incandescent/halogen and compact fluorescent lamps are inappropriate for industrial lighting due to their low efficacy. They are more appropriate for use in households, where lighting is used for only several hours a day.
Output and service time for a given level of light
A very important parameter when choosing industrial lighting is the output and service time for a given level of light, because that is directly connected with the expense of servicing the fixture. In very many cases, changing “faded” (or “settled”) or burned-out lamps in manufacturing companies is a significant problem. In some cases, it is even necessary to halt operations in order to reach the lighting fixtures located above installed equipment at great height.
* service time until 10% malfunction.
** light support as a percentage of initial, after the indicated service time has passed.
Although metal-halide lamps for a long time were the most popular light source in industry, their short service time and rapid decrease in light yield during their first hours of service are the main reasons why metal-halide lamps are now rapidly losing ground to other solutions as a light source in industrial lighting. Metal-halide lamps are especially unsuitable for use with motion and light sensors.
Start-up time and the property of dimming are two of the main parameters determining the possibility of using a light source together with modern-day lighting-management systems: motion and light sensors.
*Starts instantaneously, but needs to heat up prior to attaining full light output.
The start-up time for high-pressure discharge lamps is very long, 10 or more seconds, and, in addition, not all of them can be dimmed. Ceramic metal halide lamps have a particular flaw: in case of an interruption in the flow of electricity, their re-start-up time is 15 minutes. Therefore, they are absolutely unsuitable for use as industrial lighting.
Because of all these disadvantages, generally speaking, the use of high-pressure discharge lamps as industrial lighting can no longer be considered a rational decision.
So, having analysed the various properties, we can see that of all the types of light sources we have considered, the most appropriate light sources for industrial lighting are LED and fluorescent lamps. Each of them has its own advantages and disadvantages, but the differences are not so large and depend more on the quality, price and manufacturer of the solution chosen, therefore it would be best to discuss them with the lighting specialist offering a particular solution.
Below we present a brief comparison of all the main parameters, dividing LED as well as fluorescent lamps according to their types.
*Starts instantaneously, but needs to heat up prior to attaining full light output.
Structure of the lighting fixture
The next step in selecting a suitable lighting solution is to choose an appropriate structure for the lighting fixture. The structure of the lighting fixture determines the uniformity and effectiveness of the lighting. Diffusers are often used in low-hanging ceiling fixtures, while large reflectors or optic lenses are used in high-hanging ceiling fixtures. Both are made to regulate the light output.
The selection of a suitable light fixture structure directly influences the number of light fixtures necessary to achieve the desired lighting level, and that directly affects electricity usage. In the diagrams presented below, we can see how different structures of light fixtures having the same output and in the same quantity influence the lighting level.
One of the main elements of the structure of a light fixture is the reflector or the lenses. The function of both a reflector and the lenses is the same: to concentrate and direct in an appropriate direction the light produced by a light source. The use of reflectors and lenses increases a light fixture’s efficacy by 50 - 70 percent.
However, there are two sides to the coin. The use of large reflectors and lenses significantly increases the price of the light fixture. Therefore, the primary task of the designer is to select the optimal variant, taking into consideration the price and efficacy of the light fixture.
All light fixtures may be categorised according to the height of the facilities in which they will be placed: facilities of low height (2-4 m), medium height (4-8 m) and especially high heights, up to 25 m.
The electronic part of the light fixture
The heart of every light fixture is its electronic starter, popularly known as “ballast.” The selection of a suitable starter is no less important than the light source or the structure of the light fixture.
In industrial lighting, where light fixtures hang in hard-to-access places and at great heights, the electronics of the light fixture must be especially reliable and serve at least as long as the light source is designed to serve. Among other things, it is important to understand that the electronic starter directly affects the service life of the light source itself.
Below we present several of the most important technical characteristics, which should be kept in mind when selecting a light fixture.
This function is necessary when light fixtures are often turned on and off, e.g., in offices or when used together with motion sensors. Without this function, lamp service life dramatically decreases. The pre-heating function is used only in fluorescent lamp starters.
In industrial sites, voltage fluctuations are quite frequent; therefore it is necessary to consider the indicated supply line voltage. It is important to remember that the starter experiences the greatest loads when there is low voltage, therefore the lower limit is especially important. The recommended parameters are 200 - 260V.
Maximum permitted temperature Tc
This parameter specifies the maximum permitted temperature of the starter’s body. If Tc exceeds the permitted norm, the starter’s service life rapidly decreases. In industrial lighting, the recommended Tc parameter is 65 - 75 degrees.
Some starters from the better manufacturers have overheat protection. In this case, the starter is automatically turned off, so that the system can cool. Regulated (DALI or 1-10V) electronic starters, in case of overheating, do not turn off, but dim the light source until the system cools.
This parameter specifies the power factor of the electronic starter. A low power factor means larger electricity losses and electricity usage. The recommended value is > 0.95.
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