Monday, April 13, 2015


Linear Fluorescents have largely been superseded by LED's,
but are still a good option in terms of efficiency. Ballast losses
are higher for older electromagnetic designs.
Factories are too diverse and complex for there to be meaningful benchmarks in terms of the contribution of lighting to overall energy consumption. In general however, except for very light industry (no pun intended), the proportion of a site's total energy that is employed for lighting tends to be small. Despite this fact, I always include lighting assessments when reviewing energy usage on any industrial site. My main reason for doing so is that this is often an area heavily laden with low hanging fruit from an energy efficiency perspective.
Often the basket of lighting opportunities identified has a payback of under 2 years, with many individual lighting solutions having an almost immediate payback. Of course one wants short paybacks for lighting projects, given that lighting retrofits will not have the lifespan of other larger investments. Savings with regards to lighting are about far more than lighting retrofits however, so be sure to include options such as work practice changes, maintenance and operational improvements when seeking to reduce lighting costs.
There is a huge amount of detail associated with the rigorous analysis of lighting opportunities, and I won't get into that here. What I want to highlight in this post is how simple it can be to identify and implement sustainable lighting savings. Firstly, the cost of lighting has to be appreciated along with the drivers of operating cost. The energy used for lighting is a function of input power to the lighting / luminaires and the operating hours involved. It is quite a simple exercise to carry out a lighting inventory which outlines, preferably on a "room-by-room" basis, the number of lights, their individual power consumption levels and their hours of operation. This can then be converted to an annual  energy value (in kWh), and then, depending on applicable tariffs, an annual energy cost can be calculated for each individual room. This is a simple enough exercise - don't forget to include ballast losses. It is also important to appreciate that lighting often contributes to maximum demand, and hence an apparent power value for individual lighting options must be determined. You might need to consider power factors should the site concerned not have a correction system in place, but to keep it simple, perhaps just take the power factor of individual fittings as unity and add the apparent power levels to assess the contribution to site demand. Ignoring demand can make a large difference to the estimated operating cost of lighting.
Once you have this inventory, you can set about identifying relevant solutions for each area. The plethora of modern lighting solutions can make this a minefield as you consider issues such as lumen output, lumen depreciation, lifespan, colour rendition, efficacy, lighting and installation costs, disposal considerations, human health impacts etc. The key point I want to convey with this post is that while the temptation often is to pursue the latest innovations in lighting technology, there are very simple ways that lighting costs can be reduced. Before embroiling yourself in cost benefit analyses for individual lighting technologies, take some time to apply some common sense to the matter of finding savings. Questions I often ask as I evaluate individual areas include:
  • Are there any obviously inefficient options in place e.g. mercury vapour lamps, T12 fluorescents with magnetic ballasts, incandescent lights etc? If so, what can they be replaced with? - there is no standard answer here, and it depends on the individual installation and characteristics of the room e.g. roof height, reflective surfaces etc.
  • Is there too much light available on working surfaces (as measured with a light meter) when the lights are on? This would be wasteful, and often savings are possible through a simple reduction in the number of luminaires. It is sometimes also possible to modify existing luminaires e.g. the control gear for mercury vapour lamps can be bypassed and the existing fittings can be used to house compact fluorescent lights. Be sure to adhere to regulatory lighting standards as a minimum.
  • Are daylight harvesting opportunities available? This may result in lights being switched off during the day, or to a reduction in the number of lights used during the day. Existing lighting may require supplementation with options such as transparent roof sheeting for example.
  • What are the switching arrangements? It is not uncommon to find a single switch for a large area, but with only part of the area used regularly. By applying a zoning strategy, lights can be switched on selectively, saving large amounts of energy. Switching options can also be used to provide flexibility in terms of the number of lights switched on e.g. all lights on dull days but only a few on typical sunny days.  
  • What are occupancy levels for individual areas? Motion sensors can be a useful solution when paired with the correct lighting types.
  • Are windows, roof sheeting and lamps themselves cleaned regularly? If not, can a simple cleaning regimen be easily implemented?
These simple solutions are every bit as important as the deployment of efficient lighting technologies, and most often cost very little to implement, if anything.
Copyright © 2015 Craig van Wyk, all rights reserved