RETROFITTING EXEMPLARS

A simple retrofit at King’s Cross Station was rejigged to save energy. Pennie Varvarides finds out why

One of London’s most used train stations is being refurbished. Everything is getting a facelift – including the lighting. Last year, work started on modernising King’s Cross Station and the project will be completed over the next three to four years.

The station was designed by architect Lewis Cubitt and opened in 1852. It is the oldest of London’s great stations. Working on a Grade 1 listed building means extra care had to be taken with the infrastructure.

The new lighting had to be sympathetic to the architecture, but high standards had to be met.

Using 3D solid modelling and careful design, Holophane came up with a lighting scheme for two sheds at King’s Cross Station that does both, while cutting energy use by a projected 60 per cent compared with the original design.

Efficient luminaires have been positioned for optimum effect, so smaller lamps can be used to achieve the required light levels. This, combined with advanced lighting control, helped reduce energy consumption by 56 per cent.

Holophane’s development manager Chris Sowerby says: ‘We had to overcome the Network Rail standard of 150 lux at all parts of the station where rolling stock is present. We simulated the location of trains in the platform areas and calculated the correct levels of illuminance. ‘The problem is, trains might cast shadows as they pull in. We had to make sure that didn’t happen.’

Meeting the standard

Initially, the design for the barrel-roof train sheds called for the installation of 160 450W Prismpack luminaires, using the original mounting points. After the 3D modelling of the space carried out by the design team, Holophane realised that the original mounting positions – in two rows of 40 in each shed – were not ideal to light the platforms.

By rearranging the luminaires into four rows of 20 per shed, 320W Prismpacks could achieve an even light distribution and maintain illuminance. The four mounting rows were in line with the four catwalks already in place for maintenance, where lighting can be accessed through trapdoors.

However, the client was uncomfortable with the proposal to use 320W Prismpack because the lamps were only available from one supplier. It opted instead for the more widely available 400W lamps.

This has resulted in a reduction in installed electrical load of about nine per cent after control gear losses are taken into account.

Holophane cut energy use by a projected 60 per cent


Controls were introduced to ensure the 400W lamps will be under-run when full power isn’t necessary, keeping energy consumption to a minimum. Holophane’s Optimised Lighting Operating System (Holos 2) enables lamps to be dimmed while still delivering the required light output. As the lamps age and lumen output begins to fall, the illuminance levels will be maintained by increasing power to them.

The digital command system works both on a timer and with daylight, dimming the lamps automatically. Photocell readings of daylight and artificial lighting are taken, and as daylight increases the metal halides adjust accordingly.

Daylight dimming

Sowerby says: ‘If there is enough daylight, the lamps switch off. They go from 100 per cent down to 30.’

At 1am, when the station is deemed to have closed, the controls are set to reduce lighting to a third of the standard level. This is considered adequate for general maintenance. The lights resume full power at 4am when the station reopens.

‘We’ve made sure there is an override button, so the supervisor can boost levels back up in case a train is running late, to welcome passengers to a well-lit and welcoming station,’ Sowerby explains.

‘When lighting a station, as with all public spaces, it’s important to focus on safety, security and make sure it’s fit for purpose. The lighting must provide a pleasant and welcoming environment.’

The scheme is saving almost £30,000 a year compared with the original design. The project started as a potential point-for-point retrofit, but by looking deeper at the possibilities available thanks to technological advances since the last scheme was installed, the client has saved huge amounts of money.

By working with the structure already in place in the shape of the four catwalks, the building didn’t have to be modified to access the mounting points.

As the refurbishment project continues over the next three to four years, installation staff will be working overhead, hidden by a rolling roof in place to guard staff and passengers from any drops or mishaps. The work is being rolled out from the south end of the station.

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