Ammonia keeps Heathrow Terminal 5 cool

By Sabine Lobnig, Jan 08, 2009, 00:00 2 minute reading

One of the world’s largest airports is aiming to become also one of the greenest ones. At the heart of efforts to make the newly opened Terminal 5 virtually HFC-free lies a central ammonia chilling plant. An evening paper on 15 January will explore the chillers’ design, application, and challenges met by the installation.

Handling over 60 million passengers each year and containing a city of 60,000 workers, Heathrow Airport in London, UK, is one of the busiest airports in the world. The construction of its newest terminal, Terminal 5 (T5), provided a unique opportunity to not only make room for 27 million more passengers after April 2008 but also integrate some of the most advanced environmentally-friendly features seen so far. To achieve the ultimate goal of building the greenest airport terminal in the UK, state-of-the-art lighting, heating and cooling solutions were factored into the building costs of £4.3 billion.

To make the vast T5 virtually independent from the use of ozone-depleting and high global warming HCFCs and HFCs, all heating and cooling is done by a dedicated energy centre providing continuous supply of hot and chilled water for heating and air-conditioning respectively. All chillers operate with the non-ozone depleting and non global warming refrigerant ammonia (R717). The natural substance was selected by the airport authority because it was recognised as a future proof solution offering excellent efficiency. A thorough risk analysis and safety review removed last concerns regarding the system design and the installation’s safety and confirmed that ammonia would not pose any greater risk to the public or the airport staff than any other conventional large chiller solution. In fact, large ammonia chillers had been already used before in more densely populated applications without any safety compromises.

The Ammonia Plant

UK manufacturer Johnson Controls / Sabroe supplied Heathrow’s central chilling plant with four energy efficient chillers, each with a cooling capacity of 6.6 mW, or 1,875 tons. The units, powered by high-voltage electricity, use twin compressors ensuring a good part load performance, while the 11 kV motors reduce transformer losses. Safety features include a minimal refrigerant volume through plate heat exchangers, separate sealed compartments, a leak detection system, and an electrical switching outside the compartments. As the large-scale R717 chillers deliver higher efficiencies than smaller local chillers, they are expected to reduce energy consumption by at least 30% and possibly more from the chilled water store benefit. Storing the chilled water reduces the system capacity and takes advantage of night electricity rates.

Case Study explores Ammonia Plant

On 15 January, 2009, Derek Moore, Manager of Sabroe UK, will present an evening paper about the ammonia plant at T5. The lecture, held at the London South Bank University, will provide the following insights:
  • Challenges presented by the increased cooling needs of the Heathrow site since its first opening in 1947
  • Selection and application of chillers for the new terminal and why ammonia was chosen as a refrigerant
  • Design concept, construction and testing employed at the site


By Sabine Lobnig

Jan 08, 2009, 00:00

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