Challenge
One of Australia’s leading food companies was seeking to reduce energy consumption at its plant in New Zealand by using heat pump technology to recover heat generated during its manufacturing processes. The complex water-to-water heat pump project was the product of a collaboration between Trane and the system designers.
The food producer has numerous manufacturing sites across New Zealand and produces a wide range of high-quality dairy, baked and grocery items. The company commissioned the project to boost sustainability, reduce boiler consumption and end dependence on fossil fuels at one of its key plants.
Solution
The designed system includes two Trane RTSF heat pumps using the low-GWP refrigerant 1234ze. One of the biggest challenges was that the processes involve a very wide Delta T which most systems would not be able to handle. However, Trane’s RSTF units are very flexible making them an ideal choice for the new system.
Wastewater produced during the manufacturing processes – which was previously directed to a cooling tower with the heat rejected into the atmosphere – is now channelled into the new system, at a temperature of around 25°C. It is returned to the factory at a temperature of 57°C.
The heat pump plant comprises a hot water supply tank, serviced by the two Trane RTSF heat pumps which each provide 450kW of heating capacity. Key heat pump system energy efficiency optimization includes recovery of the chiller condenser water. This is used as load for the heat pump evaporators and also to provide pre-heating on potable water entering the heat pump condensers – effectively free heating and cooling. Each heat pump has a condenser isolation valve that allows potable water into the condenser and an evaporator isolation valve to allow warm condenser water into the heat pump evaporator via a duty/stand-by pump. There are also three air compressors available to be used for heat recovery, adding to the heat generation achieved by the system as a whole. Each heat pump has its own power meter provided and installed, communicating to the respective Symbio800 on-board controllers.
Results
The end customer is very satisfied with the solution which is already continuously generating all the plant’s secondary hot water requirements.
The switch to the new system has gone exceptionally well and is set to meet all the cost-saving targets. The system is providing heating COP of 6 and a combined cooling/heating COP of 10 - 12. At the heart of the Trane Heat Pump/Chiller Plant Control Application is the Trane SC Tracer® which controls the chillers, valves, pumps, flow, tank level control hot water to the field and remote dial-in. Tracer SC+ provides a web-based digital controller that can be accessed with PCs, tablets and smart phones. The system controller includes powerful, factory-engineered applications that are designed to provide the perfect balance of energy efficiency and user comfort.
