Project Profile

Location: The Earth Centre, South Yorkshire

Building: Trapezoidal frame

Timber: Indigenous softwood

Frame cost: 225,000

Architect: Feilden Clegg Bradley Studios

Awards: RIBA Award 2002

Solar Canopy, The Earth Centre

At the time of construction the solar canopy was the largest solar collector in the UK. It spans 1,300 square metres, containing 250 photovoltaic panels in generating 80,000 kilowatts of electricity per year.


 

About

The concept for the canopy was an ‘abstracted’ tree. It is trapezoidal in form; it is this irregularity which adds to its beauty. The structure is a geometrically complex space frame constructed of larch poles joined by steel nodes, of which no two nodes are identical.While it was commented that a regular space frame would have been significantly less interesting, if more economic, the cost for the frame was £225K, only marginally more than steel equivalent.

The challenge was to erect this top heavy structure while ensuring traceability of 1021 unique components. Since access to the structure would always be problematic, requiring complex rope access and working while being suspended in mid-air, the focus was on doing as much of the assembly on the deck as possible. The architects had envisaged the canopy going up as an obvious series of five trusses, however our eventual solution was to sub-erect three much larger sections resting on a scaffold cradle, which we then lifted by two large cranes. Such rationalisation of the erection methodology cut this section of the work schedule by half, to one month, whilst the total erection took six weeks.

 

Frame Design

  • The irregular form of the structure meant that each of the 800 larch poles had unique measurements, as did the 221 galvanised steel nodes.
  • Each node was fabricated on specially constructed jigs because of the very high accuracy needed for the canopy’s triangulation to work.
  • A high degree of three dimensional tolerance was required, a mere 20mm over the entire structure, and since each of the poles had its individual features drilling to a tolerance of 2mm over individual connections was needed.