Hong Kong is iconic for its unique subtropical high rise/high density urban built environment, with a strong demand on air conditioning for the enormous indoor spaces in skyscrapers across the city.

To reduce the overall air-conditioning energy consumption in the 320-hectare new urban development following the relocation of the Kai Tak airport to the city centre, the Hong Kong government has taken the lead in planning a first-of-its-kind seawater district cooling system (DCS). Arup has worked with the Electrical and Mechanical Services Department (EMSD), from concept to implementation for 20 years, bringing one of the most important sustainable infrastructure programmes to the city in order to realise the Hong Kong government’s sustainability vision. 

Planning a ground-breaking climate resilience initiative

In 1998, Hong Kong International Airport was relocated from Kai Tak to Chek Lap Kok. The Hong Kong government planned urban development on the old airport site and surrounding district, covering about 323 hectares. As well as providing a large area of land for a new central business district and homes for more than 110,000 people, the Kai Tak development (KTD) also aims to play a pivotal role in promoting sustainable development and fostering a green environment for future generations. To realise this ambition, the government has taken the opportunity to implement the first-ever DCS in Hong Kong.

Why is air-conditioning key to Hong Kong’s ‘cool’ ambition?

Buildings account for some 90% of Hong Kong’s total electricity consumption, compared to a global average of 40%. This high level of energy consumption accounts for 60% of the city’s greenhouse gas emissions, and the air-conditioning systems in office buildings and malls contribute the highest portion. In planning a mega-size urban development project like the KTD, a DCS is considered to be the most energy-efficient system, consuming about 35% less electricity than traditional air-cooled air-conditioning systems. The DCS will therefore playing a key role in decarbonising Hong Kong.

Realising the sustainability vision

Arup’s involvement in the DCS project began in 1999. Our sustainability, building services and civil engineers initially researched the benefits that could be achieved through a DCS. We were then involved in the installation of electrical and mechanical equipment in the plant rooms, seawater pump house and DCS substation for the buildings. This included the laying of underground DCS pipes, seawater pipes and the associated connections that provide chilled water to the whole development. We have provided further electrical and mechanical engineering services as well as contract administration and construction supervision of the contracts for the final phase.

District cooling in action

The DCS utilises seawater to produce chilled water at central plants and distributes it to consumer buildings in the area through a 40km-long underground water pipe network. The cooling capacity generated is about 284 megawatts of refrigeration (MWr), which serves the non-domestic air-conditioned floor area of about 1.73 million m2, equivalent to a cooling supply for 40 30-storey high commercial buildings. When completed, the project would connect around 50 buildings in KTD to the DCS.

The system has been in operation since 2013 and the whole project is expected to be completed by 2022, realising an annual electricity saving about 85 million kWh, equivalent to HK$96.2 million on electricity bills and a reduction of 59,500 tonnes of carbon dioxide emissions from the development.

Benefits over conventional systems

The DCS offers economic advantages over conventional systems, as the total installed cooling capacity at the centralised plant is less than the sum of individual conventional plants in buildings. It is estimated that savings of about 15-20% on overall installed capacity can be achieved, which will also reduce the material use and plant space in the destination buildings.

By using seawater for cooling, there is a further energy saving and more open space released to the public through the removal of cooling towers. With the intake of seawater to produce chilled water, water flow and water quality of the Kai Tak Approach Channel are enhanced as well. The DCS also helps mitigate the heat island effect by eliminating heat emissions from separate air conditioning systems in individual buildings.

With significant benefits in terms of environment, comfort, operational efficiency, energy conservation, flexibility in planning and superior system reliability, DCS is not only efficient but provides a vital city-level solution to address carbon emission reduction and climate change.