It’s fitting that the emerging technology of phase change material is a key feature of the innovative new building at Swinburne University: the aptly-named Advanced Manufacturing and Design Centre.
What are phase change materials?
Phase change materials (PCMs) are organic and inorganic products that have been engineered for thermal energy storage, enabling the temporary storage of high or low temperature energy for later use. Offering a range of thermal management solutions, PCMs facilitate the ability to manage demand between energy requirements and usage.
PCMs store and release thermal energy when materials are transitioning from one phase to another: when materials freeze, large amounts of energy are released as latent heat fusion or energy of crystallisation. Conversely, energy is absorbed from the environment as solids melt into liquid.
What types are available?
Water is one of the cheapest and most effective forms of PCM, but the fixed 0°C freezing temperature makes it unsuitable for a majority of applications. Consequently, a number of materials have been engineered to mimic the freeze and melt process of water, in a wide range of temperatures.
These fall into three categories:
1) Eutectics generally take the form of salt solutions in water, with a phase change temperature below 0°C (32°F).
2) Salt hydrates incorporate water of crystallisation during the freezing process, changing phase above 0°C (32°F).
3) Organic materials are polymers with high orders of crystallisation and phase change temperatures above 0°C (32°F).
How are they used?
PCMs store thermal energy to be used at a later date in other locations. The thermal energy absorbed or released during a liquid-solid phase change provides the ability to control the temperature throughout the process. PCMs can also provide thermal barriers or insulation, an application of particular relevance to temperature-controlled transport.
Example: Advanced Manufacturing and Design Centre
Operating since 2014, the PCM system featured in the Swinburne building forms the secondary chilled water system; supplying the chilled beam circuit which services the offices and selected open areas.
Featuring an insulated storage tank with 1300kWh capacity, the tank houses were supplied with approximately 5000 self-stacking HDPE plastic containers, each containing a PCM with a freezing temperature of 15°C.
The rooftop adiabatic cooler chills the water to 14°C overnight, pumping it through the tank to freeze the PCM containers. In daylight operation water is pumped through the tank, cooling it via the heat exchanger to a controlled temperature and providing the first stage of cooling for the chilled beam circuit.
Once the tank can no longer maintain supply at the required temperature, the system automatically switches to a process where the chilled water is supplied by the plant’s chillers; a functional example of PCMs as an emerging technology in the HVAC&R field.
Read more about the Swinburne project here