Gas District Cooling Plant 4

Gas District Cooling (Putrajaya) Sdn. Bhd. planned to establish plants which has capabilities to accommodate the rising cooling demand requirement of the Core Island of Putrajaya.  Prior to the intended construction of Plant 4, Plant 2, was then basically a chiller-based plant which has the capability to dispatch a cooling capacity of 22,000RT.  However, over a short span of time coupled along with the rapid Putrajaya’s expansion, there was an immediate need for an additional cooling capacity of 10,000RT and a foreseeable rising need in the near future, hence the additional plant, Plant 4. Gas District Cooling (Putrajaya) Sdn. Bhd. had the intention to build Phase 1 of Plant 4 as primarily a Thermal Energy Storage (TES) facility rather than an outright conventional Chilled Water (CHW) Plant with Chillers.

The plant is significant in many ways mainly because of its size. It is possibly one of the biggest, if not the biggest prestressed concrete Thermal Energy Chilled Water Storage Tank in the world.  This project also carries a significance in the engineering field because it has been conceptualised and designed very much jointly between the Structural and Mechanical Engineers, to optimise the design so as to achieve a competitive and superior technical feature that won the Design and Build bid.

These significant achievements in terms of design and implementation features would in general be:

• Very Large Post Tensioned Concrete Tank
• Stratified Thermocline
• Internal rather than External Insulation
• Diffuser Support
• Seamless Future and Infra Interfacing
• Future Plant Controls at Current Phase
• Operational Flexibility

Technical Description

EDP Consulting Group Sdn. Bhd. provided consulting engineering for Civil Infrastructure, Structural and Geotechnical Services for the Phase 1 of Plant 4 which consists of a 41m external diameter x 33.7m height Post Tensioned Concrete Tank and a 2-storey plant room. The foundation system of the large water tank is a raft supported by 400mm x 400mm reinforced concrete square pile. The 33.7m height thermal energy storage (TES) tank is designed in a circular shape by using 750mm thick concrete wall with 4 numbers of buttresses at four quadrant of the circle to anchor the circumferential post-tensioning tendons. A Floor-Wall Hinged Base joint is introduced in order to mitigate the large wall base moment. The wall sits on a rubber bearing strip and the gap in between the wall and base is grouted after circumferential prestressing and prior to filling up the tank. A steel truss is designed to form the dome roof and at the same time serve as the support for top diffuser.

Project Highlights, Achievement and Recognition:

• The biggest Thermal Energy Chilled Water Storage Tank in the World, 2013
• Engineering Award 2015 in recognition of the significant contribution in the field of infrastructure, Bronze Award – The Association of Consulting Engineers Malaysia (ACEM)