Solar Gate is a sundial that uses solar alignment to mark significant times and dates in Hull. The super-light innovative two-shell structure is place-specific, responding to pivotal historic events and to the cultural context of its location in Hull’s Queens Gardens adjacent to the ancient site of Beverley Gate.
Tonkin Liu won an international art competition to create the artwork in Hull’s town centre. The architects collaborated with structural engineers at Arup and worked with Hull City Council and local fabricator Pearlgreen to deliver the artwork in the year in which Hull celebrated its status as the UK City of Culture.
The sculpture stands at a height of 10 meters but is made from miraculously thin 4mm plates. At the centre of the 4 meters wide plan the sculpture is just 1 meter deep, tapering to 100mm at the two open edges. From these edges visitors can see how the structure is formed. Two curving and corrugated surfaces join, without the aid of any additional supporting internal structures.
All of the structural strength is inherent in the sculpture’s shell form. The biomimetic technique is called Shell Lace Structure, invented by Tonkin Liu and developed in collaboration with Arup over the past 8 years. Structural lessons from mollusc shells are utilised, whose curvature, corrugation and distortion provide a direct correlation between form and strength, doing away with excess structure where it is not needed. The single surfaces of the structure are tailored out of flat sheets that are curved and joined to make rigid forms.
Solar Gate becomes an illuminated timepiece at night, with a controlled in-ground lighting system installed inside and outside the sculpture. Designed by Tonkin Liu, the lighting sequence has been programmed to alternate between outside and inside, transforming the sculpture into near-transparency.
Around the sculpture a ring of perimeter lighting turns on and off in a clockwise direction, to herald forthcoming events and festivals, including a Hull-wide art event referred to as the “Golden Hour.” Through the exploration of “time,” Solar Gate speaks of the past, makes viewers aware of the present moment, and anticipates future moments in time.
Solar Gate uses advanced digital tools to align exact sun angles from particular times and dates to pairs of large apertures on its surfaces. When a beam of sunlight passes through an aligned pair of apertures, it lands on a corresponding disc on the ground, a disc that reveals a significant event for the set of time and date. 16 reveal dates have been selected to celebrate Hull’s history and world events.