Bright Lighting Ideas
Many articles on LED lighting technology compare its raw performance with the traditional technology it is attempting to emulate. While this approach may work for many general lighting applications, such as those of retrofit bulbs, it often fails to explore the full benefits and possibilities of LEDs that can yield significant energy and operational savings compared to existing fixtures that seem efficient.
An emerging area in which LED technology can deliver a compelling value proposition is the illumination of industrial facilities, and in particular those often found outdoors in petrochemical and associated downstream industries. The requirements for lighting such facilities can be more onerous than general lighting applications due to the presence of complex structures, equipment and pipe work. The lack of walls and roof space also adds to the design challenge, as few reflecting surfaces exist and there are often limited mounting surfaces on the structure.
In many schemes, a broad brush approach has been used, with lighting design based on spacing tables with little account taken of the exact dynamics of a particular installation. This tends to lead to over-lighting, which is wasteful in terms of energy but also creates the potential for severe light pollution.
The lighting of industrial plants often is defined by national and international codes of practice, which set minimum light, uniformity, glare and color performance requirements related to the task being undertaken within a particular part of a facility. In Europe, this is covered by EN12464-2, which includes reference to the limitation of light pollution in relation to a plant’s location within the wider environment.
The case study being presented here comprises the redesign of an industrial effluent plant in Puerto Rico belonging to Henkel, best known as the manufacturer of Loctite. This plant produces adhesives and sealants serving the transportation, electronics, aerospace, metal, durable goods, consumer goods, maintenance and repair and packaging industries. The main aim in looking for replacement lighting has been to reduce the total energy consumption and improve lighting efficiency.
Industrial Effluent Plant Application
A wastewater treatment plant of this type is classed as a hazardous location. This situation means that equipment used in the area must be approved for such an environment.
The layout of the plant comprises a number of wastewater treatment tanks, around which is an access platform used for maintenance and operation of the facility. The existing lighting scheme in this area uses a total of 16 high-pressure sodium (HPS) lighting fixtures, each with a rated power of 295 W. It must be remembered that the stated lamp wattage—250 W in this case—does not include the control gear losses, which means the real circuit wattage can be around 20% higher depending on the control gear type employed within the fixture.
The existing type of lighting fixture used on the installation is used extensively in the North American market and has been in production for many years.
A polar plot for this HPS fixture gave an indication of the direction in which light is emitted from the fixture—in this case, symmetrically, around 360 degrees. The initial lumen output from the HPS lamp is around 20,000 lumens, which gives an efficacy of 68 lumens per circuit watt. A closer look at the polar plot also showed light being emitted above 90 degrees. This is wasted light and will probably result in light pollution problems.
The SafeSite from Dialight, a new generation of industrial lighting fixture that uses LED technology, directs light in a forward direction, with no light spill above 90 degrees. The SafeSite fixture has a rated wattage of 100 W, which produces a lumen output of 4,300 lumens, resulting in an efficacy of 43 lumens per watt. On first inspection this seems vastly inferior to the existing HPS fixture, but the wider application needs to be understood carefully to validate the complete performance criteria.
Lighting Scheme Redesign
The broad brush approach to lighting design can be avoided by using one of the many lighting design software tools, such as Relux (www.relux.ch), that are commonly available. Manufacturers’ photometric data, sometimes referred to as IES files, can be imported easily and direct comparisons made between different types of fixtures. Using software tools allows the lighting layout to be optimized to achieve good lighting uniformity with the minimum number of lighting fixtures.
A comparison between the HPS fixture and the Dialight SafeSite using a lighting design software tool shows that the HPS fixture has a much wider distribution than the SafeSite fixture, but it is essential to consider just where the light is actually required within a target area.
In this application, the target area is the access walkway and the effluent tanks. The HPS fixture could be better utilized by being mounted centrally, but this would mean having to position above the tanks, which would give maintenance issues. This highlights the difficulties of lighting industrial installations where light going beyond the target area is essentially wasted.
On first inspection, the HPS fixture appears to be much brighter, but this can cause other problems. The lighting objective is not just to achieve the correct light level, but also good uniformity of light across the illuminated surface. The amount of light emitted at high angles can cause glare. The SafeSite has an altogether different forward-facing distribution, with good uniformity of light across the beam.
The result of the lighting redesign is a reduction in the total number of lighting fixtures—from 16 units down to 12 SafeSite units. Combined with the much lower power rating, this means a reduction in total power from 4,736 W to 1,200 W, an approximately 75% reduction.
Although it might be the primary aim in this application, power reduction is not the only benefit of switching to LED technology. HPS light sources have an inherent orange light output, expressed as a low color rendering (Ra 20). This makes it difficult to distinguish between colors, so in industrial applications such as this, personnel can be forced to carry flashlights in order to perform basic maintenance functions such as identifying correct valves or identifying cable colors in electrical repair situations. The SafeSite LED light source has a very crisp white light output (Ra 70) that reduces the need for flashlights and improves the working environment. Figure 1 demonstrates the comparison between the HPS and the SafeSite LED installation in terms of lighting quality.
The SafeSite has a guaranteed minimum working life of five years, with the light source exceeding 50,000 hours of continued operation; this is at least double what can be expected from the HPS source. The life of LEDs does not depend on the number of switching cycles, so further operational benefits and energy savings can be realized by use of occupancy sensing around the installation. This would be difficult to achieve with HPS fixtures, as their lamp life is shortened by repeated switching and the lamps have a significant warm-up time before they provide useful light. In contrast, LEDs produce 100% output from the instant they switch on.
The final major advantage is the reduction of light pollution. The SafeSite has a sharp cutoff optical system that produces no upwardly directed light and minimal light spill outside of the target application area.
For Henkel, the outcome of this installation was better than anticipated as, in addition to achieving the objectives of cutting power consumption and creating a more efficient lighting system, the quality of illumination was vastly improved and overall safety also saw significant improvement.
“The LED lighting looks brighter and more natural—a lot less yellow, so people thought that more light had been added when actually we’ve reduced the number of fixtures by a quarter,” said Henkel maintenance manager Edgar Agront.
A Complete System
LED lighting technology can create a compelling value proposition in the illumination of industrial installations, but fully understanding the lighting requirements and application as a complete system is essential in order to achieve significant savings in energy and improved efficiency from the lower number of fixtures ultimately required.