The road to efficient lighting
October 1st 2007

The cost of ownership of lighting is influenced by many factors. Steven Henry of Chalmor explains how an independent study on petrol station forecourts demonstrates principles that apply to a wide range of lighting installations

Lighting can generate significant costs beyond its energy consumption, particularly where access to light fittings is difficult and may be disruptive to normal business in the space below.

The Petrol Retailers Association (PRA)carried out a study on petrol station forecourt lighting, its underlying conclusions, however, extend far beyond petrol station forecourts.

As well as providing sufficient illumination for customers to selfserve, forecourt lighting plays an important role in increasing the visibility of the site to passing motorists.An average forecourt produces around 100 tonnes of CO2 emissions per annum and in a 24 hour station the lighting can represent as much as 36% of the total energy consumption.

Regular maintenance is required to provide the required lighting levels consistently but day-time maintenance disrupts forecourt activity and reduces sales, while night-time maintenance is costly.As a result, it's quite common to see forecourt canopies with failed lamps, or lamps that are past their useful life, resulting in a reduced light output.

With higher wattage lamps, where the fittings have to be open to prevent overheating, maintenance requirements are increased further by insects and debris gaining ingress to the fitting.With lower wattage lamps the fittings can be sealed to IP65 ingress protection, which avoids this problem and has the added advantage of allowing pressure washing from below.

Control of the lighting is also an important factor as staff often forget to switch lighting off during the day, and there may also be an opportunity to take advantage of natural daylight.However,when daylight controls are used the lighting may be switched off several times a day.This can be a problem with the commonly used metal halide lamps, which need to cool down before they can re-strike and have an extended warming up period before full light output is achieved again.

In terms of light sources the PRA's research considered 150W metal halide, compact fluorescent (CFL),LED and induction light sources.CFL and LED light sources were considered unsuitable and a number of shortcomings were identified for 150W metal halide lamps.These included the additional 17-27W power consumption of control gear over and above that of the lamp, relatively short lamp life and high failure rates, long warm up and restrike times and a rapid fall-off in light output.The report concluded that these might be an appropriate solution for retailers on tight budgets.

However, any such retailers that fell within the definition of SME (small to medium enterprise) would almost certainly qualify for interestfree loans from the Carbon Trust to help them adopt what the PRA describes as a 'best practice' solution.This includes Chalmor's Endurance fittings (which typically 150W use induction lamps) they were shown to have low failure rates, zero energy losses through the control gear, instant re-strike and, crucially, a lamp life of at least 60,000 hours, three times that of alternative technologies.

"A five year guarantee, coupled with a long life of around 10 years for a controlled, 24-hour forecourt and over 23 years for a controlled 15 hour site make this one of the best canopy lighting solutions available", said the PRA's report.

In this respect, the word 'controlled' is very important and the report considered several solutions to controlling lighting.Basic timers were seen as preventing some wastage from lighting being left on during the day, but retailers were unlikely to programme timers for seasonal variations.Also, this did not provide any scope for exploiting daylight.

Using light sensors to control lighting in relation to ambient light levels caters for seasonal variations and variation in light levels during the day – and this can be combined with a timer if the lighting is not operating 24 hours a day.However, standard daylight sensors do not offer all the features required to maximise efficiency.The tests using Chalmor's Autolux controller showed that using several lighting channels enabled users to operate other site lighting, such as signage and flood lights, independently of the canopy lighting.

The service station that was used to demonstrate the combination of Endurance fittings and Autolux controllers was the Golden Fleece 24 hour station in Carlisle, which reduced its CO2 emissions by 68% and is saving £3355 per annum on lighting costs while the same light levels are maintained.

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