Rain has delayed many matches over the years at Wimbledon, home to the world’s oldest Grand Slam tournament. But not anymore. Now it’s game, set and match with a bespoke air conditioning solution that comes in to play when the new retractable roof over No.1 Court is closed.
A total of 26 super quiet chillers and 12 very low noise air handling units (AHUs) were specified. Noise levels were a major consideration as 20 of the chillers and the AHUs were being positioned at a high level within the stadium. They had to be extremely quiet as spectators in the higher tiers sit very close to the plant rooms which are located above the seats.
The uniqueness of the project, the location of the venue – surrounded by housing – required considerable planning and innovative designs. Building on the success of their Centre Court involvement, Aermec’s customised approach addressed an unusual combination of criteria, as Graham Turner, Aermec’s Technical Director describes:
“Aermec is continually motivated to design solutions that meet clients’ expectations no matter how challenging. We engineered a solution that addressed a unique set of criteria; noise, comfort of spectators, safety of the players and the moisture levels of the grass to prevent players from slipping.”
Prototypes were designed and built at Aermec’s manufacturing and purpose-built test facilities near Verona in Italy. Once satisfied Aermec could meet the specifications and criteria, the AELTC were invited to witness testing and sign-off the units for manufacture.
In addition to performance levels testing, extensive acoustic tests were carried out in Aermec’s climatic chamber, which enabled site conditions to be simulated.
“Our labs are AHRI and Eurovent certified and we provided extensive acoustic testing under ‘witness’ conditions enabling AELTC to see at first hand performance levels and that acoustic criteria were being met,” says Paul Lawrence, Aermec UK’s Managing Director.
Once production units were completed, further testing was carried out to ensure peace of mind for the customer. A similar process was adopted for the 12 very large bespoke AHU’s. Each unit was designed with an air volume of 12m3/s. As spectators would be sitting underneath the plant rooms, Aermec’s solution had to ensure that there would be no breakout noise from the bottom of the units, detracting from the matches and causing a nuisance for spectators. The AHU’s were fully performance tested at design conditions, which was only possible again due to Aermec’s investment in climatic chambers.
Aermec tested various acoustic materials over many months to ensure there was no breakout noise from the units. Once they had achieved the desired results, Aermec embarked on the construction of substantial steel frame work at the factory, which would enable the AHU’s to be positioned 1.8 metres above the ground and sound measurements were then taken from underneath the units in situ.
Because of the AELTC’s location within a residential neighbourhood, sound levels were crucial. Extensive testing was carried out through the night to ensure that no background noise would be emitted.
The chillers were delivered in phases and were super low noise slim chillers each with a capacity of 300kW and fans capable of 320Pa ESP (External Static Pressure).
There were a number of logistical constraints. As well as sound criteria, sight lines for neighbours in the area were to be maintained where possible, so careful consideration was given to height of any roof top plant and aesthetics.
Six of the chillers were located in the basement and access was facilitated underneath Courts 14 and 15 when the new underground facilities for the Ball Boys and Girls and media were constructed.
The other 20 chillers were designed to fit within physical constraints of the court. To address the acoustic requirements, they were enclosed in five special acoustic pods, each containing four chillers in a 2×2 double-deck arrangement on the north side of the court and directly above spectators. The pods were designed to accommodate air intake on one side only.
EC direct drive fans were used to ease commissioning and set design air volumes without the need for pulley and belt changes. Inverter pumps were also used with varying pressure control to ensure a constant flow rate as the quantity of chillers in operation increases and decreases.
The AHUs were arranged within custom-designed steel framework. Acoustic housings were unnecessary as the AHUs were designed appropriately to meet the noise specifications. Each unit has 50mm thick panels with mineral wool insulation 100kg/m³ and 1.2mm thickness galvanised steel internally and externally. The fan section has 150mm panels of extra insulation to reduce the radiated noise of the fan.
Four AHUs were situated on the east side of the court, four on the west side and four on the south side. The units were installed on the roof in sections and Aermec carried out the final connections once all sections were in place.
The retractable roof takes between eight and 10 minutes to close and the AHUs start up as soon as the roof is closed. Depending on the conditions, the air conditioning can take minutes to acclimatise the climate within the bowl and allow matches to restart.
One of the key challenges for Aermec working on such a unique project, was ensuring that the required levels of temperature and humidity could be met and the grass could also be insulated from moisture, preventing players from slipping during play. Sensors are embedded in the edge of the grass court and further sensors are located in the roof trusses to monitor moisture and temperature levels.
When the roof is closed, the system drives down the humidity level to around 50% RH to ensure no condensation can occur on the grass playing surface or on the roof structure. The priority for the system is the grass and to ensure the air movement does not interfere with the movement of the tennis ball. All this has been modelled using computational fluid dynamics.
Aermec worked with the AELTC and ME Engineers, who designed the full M&E services for the No.1 Court redevelopment, having also been involved with the Centre Court project. The close collaboration of all parties successfully ensures that play on No.1 Court will continue no matter the weather.