As we continue to face the challenges of climate change, one of the most pressing issues is finding ways to reduce our energy consumption and greenhouse gas emissions. Small Planet Supply and WaterDrop Systems are tackling this problem head-on by using a revolutionary technology in a new system that has the potential to transform the way we heat and store water in multi-family buildings.

At the heart of this new system is phase change material (PCM), a substance that can store and release thermal energy as it changes from a solid to a liquid state. When integrated into a water heating system, PCM can help reduce energy consumption and carbon emissions while providing a more efficient and sustainable alternative to traditional electric resistance water heaters. One of the key benefits of PCM is its ability to store thermal energy during periods of low demand, such as overnight or during non-peak hours. This stored energy can then be used to supplement the heat produced by the water heating system during periods of high demand, reducing overall system load on the electric grid.

It was this highly intriguing proposition that piqued the interest of the WaterDrop team and project lead investigator Hayes Zirnhelt with Whole Systems Energy Consulting.  Last year the project received a grant from CleanBC Building Innovation Fund.  Their familiar heat pump water heater skid system is being modified to use a combination of heat pump water heaters and a mixture of hydrated salts to create a more efficient and sustainable heating system for commercial buildings. By pairing a heat pump water heater with a PCM storage tank, WaterDrop Systems can take advantage of the heat pump's efficiency while minimizing the impact of hot water recirculation issues due to colder than ideal return temperatures and the reliance on electric resistance to buffer that problem.

WaterDrop Systems' partner Hayes Zirnhelt explains how the system works. "We take the electric resistance water heater out of the equation entirely and replace it with a heat pump water heater array that heats the PCM storage tank. The PCM acts as a thermal battery, storing the heat until it's needed." This boosted energy storage is thanks to sensible and latent energy storage that a PCM provides.

Sensible energy storage occurs when a material's temperature changes due to the transfer of heat energy. When a PCM is heated, it absorbs thermal energy, and its temperature rises until it reaches its melting point. At this point, the PCM begins to undergo a phase change from solid to liquid, which is the latent energy storage process. The PCM continues to absorb heat energy as it melts, but its temperature remains constant until all the material has melted. This is because the heat energy is being used to break the bonds between the molecules of the material, rather than increasing their kinetic energy (i.e., their temperature).

The latent energy process provides a boost when the PCM solidifies, allowing the heat energy to be released back into the surrounding environment. This is a useful property for thermal energy storage, as it means that PCMs can store large amounts of energy in a relatively small volume without experiencing significant temperature changes. WaterDrop takes advantage of this process by transferring the thermal energy contained in water into the PCM by running it through an arrangement of pipes routed through our blend of hydrated salts, storing energy when it isn’t in demanded, and releasing it when it is needed. The process is much like a battery, but instead of storing electricity, we are storing thermal energy directly.

By using PCM as a thermal battery, WaterDrop Systems can achieve a higher storage density than traditional water heating systems. Initial results show up to twice the energy storage as the same volume of water. Due to the latent energy, this means that they can store more thermal energy in a smaller space. This also gets rid of the necessity of a stratified storage tank, which results in a tall skinny configuration that can be hard to fit in some cases. Reconfiguring the primary storage to different shapes will result in reducing the overall system footprint and making it easier to integrate into existing buildings.

The benefits of this technology are clear. By reducing energy consumption and carbon emissions, WaterDrop Systems is helping to create a more sustainable future for us all. And with the potential to reduce operating costs and increase energy efficiency, it's a smart choice for businesses looking to cut costs and improve their bottom line. The initial round of component level testing is complete and shows that our initial modeling numbers are in line with real world performance. Next is a full-scale testing station under load, which has been completed building.

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