Friday, June 29, 2012


A Mercury Vapour (MV) security light on an industrial site.
My post on electrical energy saving garnered a lot of interest, so I thought I’d get into a little more detail on the types of areas I typically investigate when looking for electricity savings on industrial sites. 

This is the first in a series of posts which will each explore how to approach energy conservation in individual areas at industrial facilities. In this post I’ll look into the issue of lighting, but stay tuned for future posts which will feature electricity-saving insights in other generic areas where electricity is used as an energy carrier.

Lighting generally incurs a significant cost for industrial sites, principally because industrial sites are large in extent. It is also often a surprisingly overlooked area in terms of electricity savings, probably because process energy requirements are typically believed to be far higher than lighting requirements. If your site operates a battery of induction furnaces, don’t expect lighting to make up a big proportion of your bill, but for light industries (no pun intended), lighting could easily be responsible for up to half of the total electricity bill. The proportion is however not important, it’s the absolute cost. Remember also that in many instances, lighting contributes to maximum demand and you need to consider this in assessing potential savings.

As with all electrical energy consumption, it is useful to think in terms of "kWh" when considering the energy aspects of lighting. The “kW” portion refers to the amount of power consumed by the lights concerned, while the “hrs” portion pertains to the running hours for the lights. Reducing either one of these aspects of energy consumption reduces the amount of energy used, the costs of this energy and the emissions associated with lighting on your site.

Reductions in” kW” (i.e. the power consumption of lighting) are achieved through the use of energy-efficient technological options and the complete elimination of unnecessary lighting, while reductions in “hrs” are arrived at by asking simple questions regarding whether lights could be used for fewer hours in the day. If you think of reducing lighting energy requirements in these terms, you can be logical about things and can generally find low-hanging fruit through a simple plant walk-through. As with all sustainability issues, lighting opportunities will involve a combination of technology, behaviour, work practices, applied standards and other inputs, but never technology only. 

It is of course vital that you ensure that no matter the solution chosen, the minimum lighting levels (as measured at the work surface) required to operate safely are achieved. The colour rendering capabilities of the light provided are also important in some industrial environments, for example where plant operators need to be able to clearly discern changes in colour e.g. for product quality checks.

The first thing I typically do when assessing lighting opportunities is to measure lighting levels throughout the site (using a hand-held light meter) and to conduct an inventory of the lighting solutions that are currently in place. This inventory should include:
  •  The type of lights in place;
  • Their number and location (including spatial arrangements) in each area;
  • The contribution of light sources such as windows and skylights – these do not consume energy, and  should always be your first choice option in terms of alternative lighting;
  • Switching arrangements for all light sources – I am constantly surprised by how often this obvious opportunity is ignored, with huge areas unnecessarily being lit up simply because the work area actually needed is operated with the same switch as for other areas;
  • The power consumption of the individual electrically-powered light sources – remember to include the  power consumption of ballasts for light sources such as fluorescent lamps and mercury vapour lamps;
  • The design output (in lumens) of the various light sources;
  • The condition of the lights i.e. are they clean, are there visible differences in light output for individual luminaires? etc;
  • The conditions experienced in the area e.g. is it a dusty environment, is it wet etc? I recently did some work in an industry involving extensive stacking of materials, which led to widely varying light conditions depending on where material was stacked relative to light sources.  Here wall-mounted light-sources are inappropriate, for example.

If you do the above assessment, you will be in a position to conduct an evaluation of the energy consumption associated with each area annually, based on power requirements and time of operation, noting also which areas need to operate under varying conditions e.g. during the day and at night, in which case your measurements should be done under these conditions also.

With this baseline in hand, you can now begin to assess alternative solutions, which could entail:
  • Behaviour change, encouraging the use of lights only when needed – my advice is to look at the issue holistically. For example,  I was once told by a plant operator that the only reason he left the 400W Mercury Vapour lamps on during the day in his work area during winter was because the lights provided a source of warmth - there were deficiencies in the building envelope which encouraged this behaviour;
  • Minor technological change e.g. motion detectors (be sure to only use these with the appropriate lights e.g. fluorescent lights will have a shortened lifespan if constantly switched on and off), and/or changes to switching arrangements;
  • Use of daylighting as far as possible – I’m often amazed at how little this is done in a sunny country such as South Africa, even at factories that run in the daytime only. Transparent polycarbonate sheeting is not very expensive, can be made to order in terms of dimensions and can be used for roofing and other parts of building envelopes to provide natural light;
  • A reduction in the number of lights used (this may mean rearranging existing lighting) or their individual light output where lighting levels are excessive;
  • Employment of higher-efficiency alternatives (this is an area in constant flux, so you may want to do some research of your own or consult a few specialist vendors to understand the landscape before you make choices regarding solutions)

Generally a combination of these approaches is required to arrive at the optimal solution for a site.

The issue of technology tends to be quite interesting given how dynamic the lighting sector is, and in practice I see many sites that feel compelled to adopt the newest options available when making lighting changes. This is not necessarily the best way forward, and in my humble opinion it is far better to use tested technologies. Given that lamps are basically consumables, this is one area in which you really do need to look at life cycle costs, and here I’m not necessarily talking about externalities, but simple life cycle economics. You need to choose the right lights for the right applications so that you don’t shorten lamp life, and be very aware of the lifespan of the lamps concerned when they are employed in design conditions, since the costs of regular replacement can very easily wipe out the energy efficiency gains.

One last comment about lighting is that taking a “big bang” approach can be risky due to the potential for a large financial outlay for technologies which may not perform to your requirements. Making carefully considered changes in individual areas over time is a good way to assess different lighting options and ultimately make better future choices. It is also possible to make incremental improvements using existing light fittings, which reduces the costs of implementation significantly. For example, CFL replacements for mercury vapour lamps are now readily available (you will need to assess light output of the CFL's to ensure sufficiency, and also bypass the control gear on the MV fittings) as are replacement fluorescent tubes with higher lumen output and lower energy requirements than older models, but which can be used with older fittings. You can therefore take a portfolio approach to lighting upgrades, minimising your risks while achieving meaningful savings should you wish to get your feet wet before taking the plunge.