Next generation smart hot water tanks with integrated latent energy storage

Water heaters (WH) have long been an indispensable part of our homes, and now chances are they can take part in the green transition by storing and distributing energy in an even smarter way. Traditional water heaters (WH) heat up the water and store the heat until you start tapping. As you spend water, the tank is replenished with cold water, which is continuously heated again. But what if you could postpone heating to a more favorable time, for example, when the electricity price is low? In this project, WH are equipped with phase change materials (PCM), which are substances capable of absorbing and releasing large amounts of energy during a phase change, typically from a solid to a liquid state. In practice, this means that when the WH heats up the water, a portion of this energy is stored in the PCM by changing its state. The innovation lies in the ability to store larger amounts of energy over a longer period and at a lower temperature than in traditional heaters. When hot water is needed, the release of this stored energy is triggered by initiating a phase change in the material. The result? A more energy-efficient and reliable source of hot water, generated by previously stored energy. Better storage capacity and lower heat loss will be key properties facing the new EU Eco design directive. The strain on the power grid can be reduced by utilizing stored energy during periods of high demand. This helps smoothening fluctuations in energy consumption and reduces the need for additional power production. Secondly, costs can be saved by acquiring energy when the electricity price is low. IPN InterLES, a collaborative project between the water heaters manufacturer Høiax (owner) and SINTEF Energy Research, is driving forward the evolution of water heating technology. Led by SINTEF and supported by the Norwegian Research Council (6.7 MNOK), alongside an equal investment from Høiax, totaling 13.4 MNOK, InterLES aims to revolutionize conventional water heating methods.

InterLES aims to increase the energy storage capacity and reduce the energy loss of the next generation hot water tanks (HWT) by integrating latent heat storage. Innovative integrations of phase change materials (PCM) and smart control algorithms reduce electricity costs for consumers, enhance grid stability, and minimize energy losses. The outcome of the project will pave the way for more energy efficient HWTs and outphasing of gas-fired water heaters. Through the project we will design and test three integration ideas for PCMs in HWT systems: PCM filled in (1) macroencapsulation and (2) cylindrical containers within the water in the tank, and (3) a cylindrical sleeve with PCM around the HWT as part of the insulation. Multiple PCMs with increasing melting temperatures from bottom to top will be tested in the HWTs to ensure complete melting of each PCM within the stratification temperature profile, which varies across the height of the HWT. Each integration concept will undergo laboratory testing and computational modelling to evaluate its potential for mass production based on eco-techno-economic analysis to identify the most promising concept for further development. InterLES aims to develop a 200L combined water/PCM smart storage hot water tank with an increased storage capacity of 3 kWh / 30% and reduced heat loss of 7 W / 10 %. This solution could potentially be adapted to HØIAX's range of products, from small to large scale HTWs. If half of households in Norway adopt this smart storage unit, this would increase the total energy storage capacity with 4 GWh and increase the annual energy saving with 80 GWh. In the European market, this solution has the potential to increase the total energy storage capacity by 0.3 TWh and reduce the yearly energy loss by 6.2 TWh. HØIAX estimate they can more than quadruple their present sales volume if they are ahead in this development.