WoolWorks in Timaru has replaced an ageing six-megawatt (MW) coal-fired boiler with a more efficient eight-megawatt electrode boiler and a 750-kilowatt (kW) CO₂-based heat pump system as part of a large-scale decarbonisation project, supported by New Zealand’s Energy Efficiency and Conservation Authority (EECA).
The refrigeration and heating upgrade was led by Piersons Refrigeration & Air Conditioning, which was responsible for the design, supply, and installation of the high-temperature CO₂ heat pump.
“Traditionally, WoolWorks had used a six-megawatt coal-fired boiler to meet their hot water production needs – quite an old and inefficient process,” said Matt Thomas, Managing Director at Piersons. “The majority of the water is consumed by the wool scouring process, with the dirty wastewater providing an excellent opportunity to recover some waste heat.”
The wastewater, typically between 35–40°C (95–104°F), is collected in a common sump. Heat from the water is first transferred through a self-cleaning, tube-in-tube heat exchanger to an intermediate circuit. This low-grade heat is then upgraded to 90°C (194°F) by the CO₂ heat pump system using a vapour compression cycle.
“This high-temperature hot water is produced at a flow rate of two litres a second, with a COP of more than 3.5,” said Thomas. “This means that for every unit of electrical energy, the heat pump produces 3.5 times that amount in thermal energy.”
Piersons’ Senior Engineer Josh Le Compte, who supervised the installation, described the unit as a customised system designed specifically for the site's needs.
“This heat pump has been designed specifically for this project, and because of that, we’re able to extract every drop of efficiency,” said Le Compte. “Our very user-friendly and visual human machine interface means our technicians are able to commission, diagnose and monitor all aspects of the system, and it can also be accessed remotely.”
The system also includes an air-dryer heat reclaim unit and a flow-down heat recovery system, which further reduce energy demand. These additions help ease the load on the new electrode boiler and allow WoolWorks to operate within its permitted electricity usage threshold.
The project was a joint effort between Piersons, Glaciem Cooling Technologies, and engineering consultant Lumen. Their scope included the full design and build of the heat pump, pump skids, electrical works, field services, and regulatory approvals.