What can specifiers of lighting equipment learn from a cruise ship operator? We spoke to DPA Lighting Consultants about its work to study lighting on board – and the wider issues of energy use at sea. Martin Tomlinson reports

Crystal Cruises operates luxury cruise ships with one eye on the environmental impact of its operations. When it needs advice on energy consumption for lighting, the company has for many years turned to DPA Lighting Consultants. DPA not only designs the lighting for newly refurbished areas of the company’s two vessels, it also studies the ongoing lighting and energy issues for both ships.

Recently, Crystal commissioned DPA to examine possible energy savings that could be achieved economically without any detrimental effect on the atmosphere of the liners. DPA already conducts a ‘lighting health check’ service for many of its clients.

As a result of the health check, DPA identified a number of energy-saving options. Some involved physical lamp changing and others were changes in the way the two liners operate. The savings achieved are significant and they involve no capital cost or extra salaries.


Like many of DPA’s clients, Crystal used a large number of 50W low voltage tungsten halogen MR16 lamps with a variety of beam angels.

To ease maintenance and procurement difficulties – particularly for an installation that is constantly travelling around the world – DPA worked out a way to cut the number of beam angles used on the vessels from four to two – 10 and 36 degrees.

Also, to make an immediate energy saving, but with no capital costs, DPA suggested that all the 50W lamps could be replaced with 35W infra-red reflective coating (IRC) MR16 equivalents (see Tech Briefing, page 96). Less heat escapes from the IRC lamps, so the filament burns hotter and more efficiently.

Cost to light two guest circulation areas

A saving of 30 per cent has been achieved at a stroke. The capital cost of the IRC lamp, when bought in bulk with only two beam angles, is virtually the same as the older non-IRC version. Both ships have full-time engineering teams that were able to replace the lamps as part of their normal duties, so there were no installation costs.

It is difficult to establish the total potential energy saving across both vessels. Some areas used MR16s without dimming for 24 hours a day, while others used dimmed lamps for only part of the day. But it was a simple decision to replace the thousands of 50W lamps because the capital cost of retrofitting was virtually nothing – except management time and professional fees.

There is an added benefit. The replacement lamps generate less heat, so energy consumption for air- conditioning was reduced.

Calculation 1 illustrates the savings made in two guest circulation areas where the lighting is switched on 24 hours a day.

There is an ongoing study that will review new light sources such as retrofit LEDs to find out if further energy savings are possible with reasonable capital expenditure and payback times. This study will be concluded in the near future but with light sources changing so quickly this is a constantly moving target.


Like many landlubber hotels, cruise ships typically have many decorative lamps in bedside lights and free-standing lights. GLS lamps of differing ratings are used in these applications as the quality of the emitted light has always been considered the best.

But DPA proved through on-board trails that modern retrofit compact fluorescent lamps with high-frequency gear – when used in shaded lights – could not be considered detrimental to the ambiance of a room.

A large number of 60W GLS lamps have been replaced with 15W (including gear losses) compact fluorescent lamps. The energy-saving calculation is again difficult to fix because of the varying hours of use and dimming of lamps throughout the vessels. Calculation 2 was used as a base position and then estimates for consumption in particular areas could be interpreted from this.

From the calculations you can infer the savings from non-dimmed lamps operating less than 24 hours a day. The calculation for lamps that are dimmed will be less favourable because more energy will be saved when dimming the tungsten than when dimming the compact fluorescent. Compact fluorescent dimmable lamps are also more expensive than their non-dimmable equivalents. The cost of the tungsten is the same, dimmed or non-dimmed.

Again, there is also an ongoing study reviewing new light sources such as retrofit LEDs.

(Note that the ship’s engineers advised that the effect on the air conditioning load is 60 per cent of the lamp load of a GLS light source.)


DPA made a number of observations of shipboard operations during its lighting health checks, and the consultants suggested several policies to save energy.

First, all room lighting in staterooms and suites should be turned off after the room is made up in the morning.

Second, only a reduced amount of light should be left on after evening turn-down service.

Third, on embarkation days, rooms were historically made up in the morning with new guests arriving at about 3.00pm. Lights were left on at make-up time, however. The new policies directed the team to turn off the lights when the room was made up and turn it back on at about 2.30pm before guests arrived.

Fourth, policies have been created to turn lights off in many spaces when there is adequate daylight and turn off lighting altogether in spaces that have periods of downtime, such as cinemas, show lounges, library and private dining rooms.

GLS vs CFL in typical application


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