Take a Load Off with Phase Change Materials

In a world where energy prices are rising, power grids are being overtaxed, and evolving building codes are pushing for electrification, a greater need for shifting electricity loads is emerging. Thermal Energy Storage (TES) can help by allowing energy to be stored during off peak hours for later use when it is needed most. Shifting energy loads off peak is a strategy that is being implemented by more utilities. It reduces strain on already burdened power grids and allows for energy demands to be met and paired with greener methods when they are available.

Phase change materials (PCM) are quickly being recognized as a great way to utilize this strategy of storing thermal energy and releasing it on demand. A phase change material has a phase transition temperature that can utilize the absorption and release of energy in practical applications. For buildings, this is usually in the range of temperatures that are comfortable for humans. These materials can be incorporated in different applications within buildings, be it space heating or domestic hot water heating, and are becoming more and more available for use by builders and manufacturers.

Storing Latent Heat in Phase Change Materials

The basic principle behind PCMs is to utilize the natural release and absorption of energy in materials as they melt or freeze. This is called latent energy. Water may have a phase transition temperature of 0*C (32*F) to go from liquid to solid or visa versa, but there are many materials that do the same at other temperatures that are more useful to us and have a higher storage density. When a material is transitioning phases, it uses more energy to rearrange the molecules than it would take to change the temperature of the same material outside of a phase change.

Using water as an example, at its freezing temperature of 0*C, it absorbs 334 Jules to convert 1 gram of 0*C water to 1g of ice at 0*C. Conversely, when ice melts to water, it releases that same 334 J/g into the surrounding area. Materials will not begin changing temperature until all of this energy is released, that’s why ice in a glass of water stays at 0*C as it is melting. This changing of phases requires more energy than raising an equivalent mass of the same material by 1*C. For water that is only 4.184 J/g, so you can see that there is vastly more energy stored and released when changing phase than there is in changing temperature.

This property can be harnessed to use that latent energy stored in the materials to change the temperature of the surrounding materials. The same example of ice in a glass of water can be used to see that it only takes a relatively small amount of ice to cool a large glass of water, as the ice is absorbing latent energy from the water as it melts, thus cooling the water. In more practical uses for buildings, different materials are used to take advantage of the effect. Early materials were things like paraffin wax and fatty acids, but ongoing research and development is finding other materials that have much higher storage densities. TES materials can broadly be categorized into 3 types, organic such as paraffin wax, inorganic which includes hydrated salts and metals, and eutectic which are a mixture of 2 or more materials with similar melting points.

Incorporating Phase Change Materials into Buildings

Since PCMs have a much higher storage density than water, they are significantly more effective at storing thermal energy. Of particular interest is the use of eutectic materials that have been tailored to meet specific temperature requirements and have a stable melting point. These materials can be utilized in different ways in buildings, both actively and passively.

Passive use of PCMs would store or release heat only dependent on the surrounding temperature of the building where the PCM is used. These materials can greatly increase the heat storage capacity or thermal mass of the building. Some development is being done to incorporate PCM into furniture or walls. In climates where there is a night and day temperature fluctuation, when temperatures drop during the night, the PCM would “freeze”, releasing latent energy and raising temperatures to be more comfortable. Then during the day when temperatures are higher, the PCM would again melt and absorb energy, helping to lower and stabilize the room temperature. This shifts some of the load off of HVAC equipment and allows for more efficient use of energy.

Active applications of PCM utilize additional equipment to store or release energy. This can be fans or pumps that move a heat transfer medium and can affect the heat transfer coefficient of heat pumps. Space heating and domestic hot water (DHW) are some of the areas of particular focus in this research, as improving the efficiency of heat pumps makes for a more efficient and more desirable system.

 When used as a TES system, PCM products can be looked at more like a battery that stores latent energy rather than electricity. This is useful for shifting the load on energy grids to off peak hours. A system using such a PCM battery would be able to run a heat pump water heater (HPWH) during the night, when demand for energy is much lower. The PCM would then be able to release the energy during the times when it is needed, which lowers the overall impact on utilities.

TES can be paired with demand/response programs that are becoming popular with utility companies, where a company can send a signal to equipment which will shut it off or turn it on depending on demand or availability of alternative energy sources such as solar or wind.

Phase Change Material Research and Development at Small Planet Supply

Small Planet Supply is excited to be researching PCM in our new Richmond, British Columbia WaterDrop Production Plant.  This work is funded with funding from the CleanBC Building Innovation Fund. for which we gratefully acknowledge the financial support of the Province of British Columbia through the Ministry of Energy, Mines and Low Carbon Innovation.

Small Planet Supply is also working in the United States with a Berkley Labs Team on a federally-funded research project. The focus of both projects is on the application of PCM for thermal storage in space heating and DHW. Electrification of our buildings is possibly one of the most impactful ways we can work towards a more sustainable energy model. The importance of efficient and cost-effective systems can bring about greater adoption in single family and multifamily construction. Retrofitting existing multifamily buildings is an important area of consideration as well and brings about its own set of problems to overcome.

Minimizing the overall energy consumption benefits end users and utilities, creating a sustainable future. Reducing the footprint of these systems makes them easier to install in new and old buildings. These considerations can help improve the adoption of these types of systems, making the net impact increasingly greater.

Our commitment to furthering sustainability and bringing the best building products to market is in full force behind this project. When we plan it with the planet in mind, we can bring about a more sustainable future for everyone. To learn more about future developments in the works, sign up for our newsletter if you’re not already subscribed. If your building schedule precludes waiting for this upcoming technologial innovation to evolve, check out other innovative products available at Small Planet Supply that save energy in your new or current home or building project, including Messana radiant panels, Spacepak Air-to-Water Heat Pumps and SANCO2 heat pump water heaters.

*Special thanks to Hayes Zirnhelt for his work as a consultation resource for this article.