Moducel units control air quality for Eden Project
The £74-million Eden Project in Cornwall is home to an abundance of exotic plants and trees where their environment is being sustained with the help of Moducel LKS air-handling units.
Moducel’s air handlers are providing tempered fresh air inside the bubble-like biomes. Where, teams of scientists, engineers and gardeners have recreated the world’s richest environments – the rainforests of the humid tropics with their rubber trees, coconuts and bamboos and the olive groves, orange trees and grape vines of the warmer temperate zone.
Thirty-three LKS air handling units were supplied and installed by mechanical and electrical contractors MJN Colston who needed a crane with a 100 metre reach to lift the units, weighing an average of four tonnes, into place around the biomes.
The gigantic biomes – Dome B, the largest has a total volume of 349,000m³ and a floor area of 18,000m² – feature twin layers of ETFE foil stretched over a hexagonal steel lattice with compressed air pumped between the double membrane to provide thermal insulation.
“At the Eden Project the objective is to let plants grow naturally in a climate designed to mirror nature as closely as possible – even allowing for seasonal variations. All this takes place under the watchful eyes of the Horticultural Management System (HMS) which monitors temperature conditions and the separate humidity control system,” says Geoff Farnham of Ove Arup Partnership, consultants for the Eden Project.
The project uses irrigation systems that draw ground water from the site. The water is disinfected before being ‘misted’ into the space within the biomes. The objective is to achieve 85%RH on a yearround basis and a maximum daytime temperature of 35°C with a minimum of 22°C. Given the sheer volume of space involved, a forced air system was the only practical means of keeping temperatures up to the required levels.
Air from Moducel LKS air handling units is injected into the biomes via ductwork linked to stainless steel nozzles. Tempered and fresh air enters via nozzles around the perimeter, while fresh air only is injected at low level. The throw patterns on the lower nozzles has been designed in such a way that the air flows up the inside of the biome membrane to create optimal air circulation.
To meet the needs of their external location round the biomes, the units have been fully weatherproofed.
The Moducel units provide a combination of fresh air supply and heating duties only and incorporate heater batteries, fans, silencers and filters together with moisture eliminators to deal with the high humidity levels. Low pressure hot water is supplied to the units by district heating lines from a central boiler plant.
Although the majority of LKS units supplied to the Eden Project feature a standard rectangular design, some vertical units have also been produced to meet the need for a smaller footprint where access is restricted. Units vary in capacity from 2.5m³/s to 7.5m³/s.
The air supply system can be set to provide for full fresh air, full re-circulation or any proportional combination of the two with heating as required. When heating is not required natural ventilation is provided via glass louvres at low level in the biomes and through the ‘petals’ which open like giant flowers to provide openings through the top of each dome.