The PWC Tower – Where Environmentally Friendly Design and Superior HVAC Systems Reside.

The success of a project is measured by the result. In the case of the iconic PWC Tower design in Midrand, Gauteng, the goal was to create a building deserving of the highly sought-after Leadership in Energy and Environmental Design (LEED) Silver Certification. This environmentally-friendly building would need to be modern, practical and “green” from HVAC to waste, adhering to the rating systems of LEED.

Commercial buildings have historically been greedy beasts; costly to build and to maintain with inordinately large carbon footprints and an insatiable appetite for power. The idea behind designing and constructing “green” buildings is to ensure the best possible environment for healthy occupants while using fewer resources and creating less waste. This means shifting the focus from what looks good, to what is environmentally friendly and practical.

Having said that, the PWC Tower is both beautiful and practical, and a testament to the dedication of the design team who have managed to create something remarkable.

The Challenges of Heating and Cooling the PWC Tower

Of course, the Heating, Ventilation and Air-Conditioning (HVAC) systems needed special consideration, and Carrier was thrilled to be part of this noteworthy build.

However, the design of this building created challenges at the start. For example:

• The building consists of 27 storeys, five parking levels and an additional annexe made up of conference facilities, meeting rooms, kitchens and canteens – spread over a vast 48 000m². Each of these areas has its own unique climactic requirements.
• This building rises out of the ground and twists upwards, completing a 30° turn at roof level. This means that each office or floor with a window experiences the heat or cold of the day differently, depending on their position in the tower.

In addition, the South African climate offers scorching summers and icy winters, with a healthy dollop of humidity depending on the month. Add the element of water scarcity and the erratic and often limited electricity supply, and the challenges become clearer.

WSP, the consulting engineers on the PWC Tower project, worked closely with specialist professionals to develop an environmentally-friendly HVAC system which worked harmoniously with other essential “green” elements.

Environmentally-Friendly HVAC Solutions

The design criteria were stringent. Guy Steenkamp, a director at LYT Architecture notes some of the key points:

• Commercially economical.
• High operational efficiency, and high coefficient of performances (COPs) of the cooling and heating systems.
• Good occupancy comfort.
• Good thermal zoning.
• Simple to maintain and operate.
• Good service access to all HVAC equipment.
• Low electrical and water consumption.
• Relatively high fresh air rates to occupants.
• Good HVAC system reliability.
• Long service lifespan.
• High filtration efficiency.
• State-of-the-art chillers.
• Integrated heating and cooling recovery.
• High-performance glazing.
• Automated internal blinds system.
• CO and CO2

Of course, the Carrier team were excited to roll up their sleeves for this project, and the final product selection and setup was certainly fit for purpose.

In his technical article on the PWC Tower, Pieter De Bod (PR Eng.) says, “The air-conditioning system comprises a central cooling and heating system. Chilled water is generated on site by a combination of two state-of-the-art high-efficiency water-cooled Carrier screw chillers, plus three multifunctional air-cooled chillers and one heat pump chiller.

“These six chillers work in combination to provide the best energy efficiency and lowest water consumption, depending on the cooling demand and the ambient temperature conditions.”

The Carrier Evergreen 23XRV chiller, the world’s first integrated variable-speed, water-cooled screw chillers are known for their reliability and efficiency.

Their brag sheets are impressive, and include:

• Their ability to conserve energy by reducing speed and optimising operation to match building load, regardless of ambient temperature
• The tri-rotor compressor features balanced rotor geometry and shorter screw lengths, resulting in vastly reduced compressor bearing loads, and unmatched reliability.
• Product Integrated Control (PIC III), a direct control solution which links into the Carrier Comfort Network (CCN) for impressive functionality and flexibility.

De Bod comments further; “Most of the AHUs in the building incorporate a night-time flushing mode to allow internal spaces to be ventilated with outside air.

Night-time flushing is normally implemented to cool the internal space when outdoor temperatures and humidity conditions are appropriate. This energy-saving feature allows the free night-time cooling to remove the heat that was built up in the structure during the daytime; therefore, the chillers will have to work less hard the next morning to cool the building.”

Read the full technical brief from Pieter De Bod here.

There’s no doubt that environmentally friendly buildings are the face of the future, and Carrier is a proud advocate of constant design and research into more sustainable HVAC systems.  And if the PWC Tower is an example of things to come, then we eagerly anticipate what’s next.