Heat and cold thermal energy storage systems: An overview

With nearly 48% increase in the world energy consumption projected by 2040, sustainable and efficient utilization of energy becomes the main strategies to reduce the impact of fossil fuel emissions and cut down the dependency on the supply countries. Renewable energy systems such as solar, wind and hydropower technologies are industrially mature and utilize a major part of producing energy in different ways, however their availability is often limited to certain conditions such as time and location. It's commonly accepted today that large-scale renewable systems require a more flexible, reliable, and smarter grid. Similarly, the reliability of non-renewable sources such as fossil-fuel power plants is often limited during peak demand periods which usually occurs when the supply demand, temperatures and solar gain are highest. Thermal energy storage (TES) is the fundamental concept of the smart and sustainable grid for renewable energy systems. For non-renewable, the benefit of TES systems is the improvement of the generation performance by supporting the energy demand during peak hours. Also, TES is often able to improve the system efficiency in a way that is more energy and cost effective. The best-known method for thermal energy storage is by utilizing the latent heat of fusion of energy storage material known as phase change materials (PCM). The phase transition in PCMs from solidto- liquid or liquid-to-solid is advantageous as the transition occurs at a constant design temperature when storing or releasing energy in the form of latent heat of fusion.