Value Proposition: Car park lighting

The client intends to refurbish the surface finishes of a 24/7 multi-storey car park. This will include a new lighting installation, replacing the existing fixtures which have gone beyond their rated life and are performing below the original design parameters.

He's willing to invest further in a lighting scheme that delivers a higher performance, provided the costs can be justified.

The client also has ambitions to win the ‘Park Mark’ accreditation, hoping to draw more customers to a car park that looks and feels a safer space.

The proposition

The existing wiring has been thoroughly tested and can be retained, meaning that the lighting improvements can be dealt with on the basis of a one-for-one replacement. The existing fluorescent fixtures can be replaced with more efficient LED luminaires.

The existing surface decorations are tired and the lighting is dull. Two important features of the Park Mark scheme are the colour of the surface finishes and the quality of the lighting. The scheme recommends that walls are best painted white or a very light colour, while the lighting installation should provide even and consistent illumination, reducing shadows and making it easy for users of the car park to recognize other people in the vicinity.

Colour rendition should be good, thus supporting the CCTV system. Generally speaking, illuminance levels providing an average of 75 lux across the parking floors are sought, with higher levels on ramps, corners and intersections.

This design exercise compares the existing luminaire, which uses a single 58W T8 fluorescent tube, with an LED luminaire of similar physical size, but which has a higher light output and longer quoted lamp life. We've based our figures on a typical 100m2 floor area with five luminaires.

 

EXISTING: 58W T8 fluorescent                                PROPOSED: 23W LED
                                       

 

 

 

CAPITAL COSTS

FLUORESCENTLUMINAIRE COST: £35 x 5 = £175

Cost of installation: £35 x 5 = £175

Total cost of installation = £350
LEDLuminaire cost: £120 x 5 = £600

Cost of installation: £35 x 5 = £175

Total cost of installation = £775

 

RUNNING COSTS

FLUORESCENTENERGY PER 100M2 
272W TOTAL LOAD PER 100M2
ANNUAL RUNNING (8760 HOURS) @£0.10/KWH

ENERGY COST PER 100M2 = £238 PA
LEDENERGY PER 100M2
115W TOTAL LOAD PER 100M2
ANNUAL RUNNING (8760 HOURS) @£0.10/KWH

ENERGY COST PER 100M2 = £101 PA

MAINTENANCE COSTS

LEDs maintain their light output better than their fluorescent forebears, but fittings need to be kept clean regardless of source and at some point the light sources will need to be replaced. And while we're used to the idea of a fluorescent lamp failing and having to be replaced, the myth around the LED source is that maintenance is not required. This is not true.

Based on a 24/7 operation, fluorescent lamps should be changed on a bi-annual basis, which means an amortised annual cost  of  £40 per 100m2.

The electronics of the LED have a longer life, but performance will degrade over time. The figures here suggest that the LED array and driver will need to be replaced after eight years. Again, that means looking at an amortised annual cost of around £45 per 100m2.

As regards cleaning, that needs to be done regardless of light source if the lighting levels of the car park are to be sustained. It's a cost-neutral component when we look at cost comparison.

 

LIGHTING CONTROLS

We've made an assumption for the figures given above that there is no lighting control strategy. The car park is open 24/7, so the lighting works continuously at 100 per cent , but it doesn't have to be like this.

Lighting controls can be used to manage the use of energy across all floors of the car park, reducing energy spend when floors are closed during quiet periods and when there are no customers on the decks. The usual approach is to use controls that reduce the light output to an acceptable background level that supports CCTV surveillance and which then increases when sensors pick up customers entering the deck.

It's difficult to quantify the extent of savings as this will be determined by establishing customer patterns and developing a control strategy accordingly.

 

VERDICT: The LED option's annual running cost saving of £137 (per 100m2) compared to the fluorescent will pay the additional capital cost off in 5.5 years. 

 

  • Technical data supplied by Dextra Lighting. Installation costs supplied by EC Electricals.