The 170m tower is the UK's tallest publicly accessible building outside of London and offers visitors a unique 'window on the sea' from its three observation decks. Forming the focal point of the Portsmouth Harbour Renaissance Project, the tower is expected to attract thousands of visitors to the area every year.
Main construction contractor Mowlem plc engaged Mark Hensman of Equation Lighting to create the exterior lighting design, which features two distinct elements: the white light projected onto the rear concrete legs andthe lower shaft below the cruciform to the front, and the dynamic coloured light projected within the arcs and to the front of the main spire.
Following a competitive tender, A.C.'s Special Projects Division was awarded the contract to supply, terminate and commission all exterior colour changing architectural lighting fixtures specified by Equation. The company assisted the electrical contractor, Mowlem Engineering, in specifying the show lighting and architectural control systems, then supplied, programmed and commissioned the two systems.
The external show lighting system consists of an Artistic License CommonSense processor receiving and responding to wind speed, tidal and time information and an ETC Expression lighting playback controller (LPC) distributing control via a 'Towerwide' DMX system, to recreate the six show designs.
The show lighting system is operated using two Unison CMEi processors connected to ETC Smart Pack dimmers, which provide the user interface via switch stations on each viewing deck for controlling the show sequence for all fixtures. These switch stations also control the interior architectural fittings at each level.A master Unison LCD control station allows the whole tower to be operated from the Central Control Room.
WYSIWYG was used to pre-programme the system's response to the various inputs of wind, time, and tide, and also to monitor and display the control system's current output, represented as a 'real time' 3D model simulation of the tower on a flat panel monitor.
28 Martin Exterior 600 washlights were installed at various positions around the tower to uplight the front and top of the Spire. A further 22 Martin Exterior 200 short throw washlights provide side fill illumination of the arc inner ribs and three viewing decks. 12 Pulsar ChromaStrip LED fixtures have also been installed inside the viewing deck rooms to provide a low level representation of the exterior show lighting. Fixtures were also installed to provide the white light projected on to the rear concrete legs and lower shaft.
The system's six selectable shows have been programmed to automatically start at 30 minutes after sunset every day, or when selected manually. In addition to straightforward shows which turn all fixtures outside the building to static blue or white, a Time show changes the colouring of the tower over 125 minutes through five-minute intervals. Starting from blue and fading up the tower through red and finally into yellow, when the sequence is complete, the tower fades back to blue and starts again.
For the more complex Wind show, an anemometer feeds wind speed data into the CommonSense, which then outputs MIDI show commands to the LPC. The LPC then alters the colour of the lighting relative to the wind from blue (at no wind), through green, yellow and orange finally to red.
For the final show, A.C. programmed the system with tidal information to enable the controller to fade the tower from blue at low tide to red at high tide, and then back to blue again.
