The National Gallery in central London houses one of the greatest collections of Western European paintings in the world and is on show 361 days a year. To replace inefficient R22 chillers, Airedale has designed a highly efficient and reliable bespoke chiller solution to meet stringent footprint and energy performance criteria of this heritage building.
The Gallery contains over 2,300 works dating from the 13th to the early 20th-century, including many famous masterpieces. Tight control of temperature and humidity in the 72 galleries is critical and maintained by air handling units in the gallery space.
Airedale has drawn on its ability to provide a bespoke chiller solution integrating new technologies, modern refrigerant and design criteria and increased control into a special TurboChill unit that reduces energy and matches the existing rooftop space and connections.
Says National Gallery Head of Technical Services, Steve Vandyke: “The existing R22 chillers had to be discontinued by 2010. They were very costly and not performing. Airedale designed a bespoke TurboChill unit to the existing footprint in the restricted space of the plant area, and supplying chilled water to a primary circuit. This feeds to a secondary distribution infrastructure which in turn feeds the satellite plant rooms containing the air handling equipment to both the main building and the Sainsbury Wing. From here the conditioned air is fed to the various galleries.
“The TurboChill is giving us enhanced reliability and energy performance. The first chillers installed have saved us approximately £16,000 over the last year compared with the R22 chillers. The compressor is maintenance-free and since there is no oil in refrigeration circuit, the chiller itself requires far less maintenance.”
Four TurboChill chillers are already installed and optimising the performance of the building. Two more TurboChill units will be operational in 2011. A bespoke sequencing scheme designed by Airedale Controls specialists will then integrate the six TurboChill units into a single, highly efficient operating system.
In designing the bespoke unit, Airedale has met some challenging criteria. The dehumidification process of the air handling units requires chilled water to be supplied at 6°C instead of the typical design of 7°C. The bespoke TurboChill is designed for 35°C ambient compared with the R22 chiller ambient of 29°C. In addition, the standard seven metre footprint of the TurboChill has been shrunk to fit the six metre footprint of the R22 chillers. Yet by adjusting the refrigeration balance, the bespoke TurboChill maintains the full load 650kW at design conditions and has an EER1 of 2.82 compared with the R22 chiller’s EER of 1.5.
Given Airedale’s in-depth knowledge of oil-free centrifugal compressor technology integrated with the partial load benefits of EC fans, flooded evaporator and interactive head pressure setpoint management giving the best energy balance for all operating conditions, part load efficiencies are giving a 25% ESEER2 rating condition of 5.87.
The bespoke TurboChill incorporates an Energy Manager which, when combined with the differential pressure transducer can continuously calculate unit cooling and EERs.
The oil-free operation of the compressor allows infinitely variable speed operation, giving exact capacity match and using substantially less power at part load. The TurboChill has a very low starting current and during any mechanical cooling, gives excellent part load efficiencies.
Mechanical consultants working for the National Gallery is Troupe, Bywaters and Anders. Project Engineer Martin Goswell says: “We undertook an independent study of the market place and Airedale was the only one that ticked all the boxes in terms of footprint, build quality, new technology such as the centrifugal compressor, and high efficiency. Some of those considered could meet efficiency but not footprint.
“The National Gallery is a high user of energy because of its large areas of air conditioned space. The Gallery’s goal is to reduce energy consumption and Airedale’s TurboChill assists that.
“The TurboChill is an excellent product. There were some teething problems at the outset but Airedale never walked away from them. The quality of the TurboChill was demonstrated when we looked at competitors’ products. We are very pleased with the quality of manufacturer and service provided.”
A factor influencing selection of Airedale was its transparency and facility to witness test. Airedale has a £2.5 million state-of-the-art test centre in which customers can witness-test products to verify duty and energy performance to ensure they will meet operational requirements.
Adds Steve Vandyke: “Airedale tested a prototype TurboChill for a year before it was launched onto the market. We prefer working with a UK manufacturer who is carrying out product development work and can give us support and reassurance throughout. We have warmed to Airedale and are happy with Airedale’s build and quality.”
Systems equipment was installed and commissioned by Capri Mechanical Services. Cranage presented a big challenge but the R22 chillers were removed and four TurboChill have been installed without disrupting normal operations of the Gallery.
Director John Uwins says: “On visiting Airedale for the witness testing we were greatly impressed with the way Airedale go about things. They have a dedicated workforce and it was evident that Airedale has a lot of interest in the technical performance of the product.”
The TurboChill is a highly efficient chiller. To make sure its full efficiency is realised, the Gallery has taken out a ChillerGuard maintenance Service Plan. This ensures the chillers do not move from the optimum parameters programmed during the commissioning stage and enables the customer to achieve maximum savings thereafter.
1 EER: Energy Efficiency Ratio
2 ESEER: European Seasonal Energy Efficiency Ratio