In the era of rapid renewable energy development, dealing with intermittent power supply has become a major challenge. As the core of thermal energy storage (TES) technology, phase change materials (PCM) are becoming an important breakthrough in solving this critical problem due to their efficient energy storage and release capabilities. Such materials cannot only meet the needs of district heating, but are also suitable for various industrial applications.
In this article, we will focus on analyzing phase change materials for thermal energy storage and discuss how they can contribute to improving energy efficiency and the wide application of renewable energy.
Table of Contents
What are Phase Change Materials (PCM)?
Phase Change Materials (PCM) are a class of materials capable of absorbing or releasing large amounts of heat during a phase change process (e.g., from a solid to a liquid). These materials are characterized by a high latent heat capacity, which enables them to store energy efficiently in a relatively small space. In addition, due to their excellent energy storage capacity, PCMs are currently used in a wide range of applications such as district heating, thermal energy management in industrial environments and renewable energy storage.
Types of phase change materials
Phase change materials (PCMs) can be divided into the following categories based on their composition and properties. Each type of PCM plays a unique role in different thermal energy storage scenarios due to its specific physical properties and temperature range.
- Inorganic systems: These include salts, salt hydrates, and metal alloys. These materials have high energy storage density and good thermal conductivity and are commonly used for high temperature thermal energy storage.
- Organic compounds: common ones include paraffin wax and fatty acids. These materials have good chemical stability and are non-corrosive, and they are well suited for low and medium temperature thermal energy storage applications.
- Polymers: A representative example is polyethylene glycol (PEG). This material is both flexible and adjustable, making it ideal for special energy storage needs.
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How phase change materials work in thermal energy storage
Phase change materials store and utilize thermal energy by absorbing and releasing latent heat. Understanding how it works is therefore crucial to selecting the right phase change material. In thermal energy storage (TES) systems, the working principle is mainly reflected in the following two aspects:
Heat transfer method
- Direct contact: the PCM is in direct contact with the heat transfer fluid to realize heat exchange, and the thermal conductivity efficiency of this material is high. However, it is worth noting that it is necessary to prevent material mixing and contamination.
- Macroencapsulation: The PCM is encapsulated in a larger container made of neutral material. This approach facilitates storage and handling while preventing leakage and chemical reactions.
- Microencapsulation: Encapsulating the PCM through tiny shells allows for more even distribution. In addition, it can be mixed directly with the matrix material, making it ideal for thermal energy storage in precision equipment.
Thermal Stability and Encapsulation Requirements
- The melting and solidification process of PCM directly affects the efficiency of thermal energy storage and release. It also determines its operating temperature. Therefore, an in-depth understanding of this process is essential. You need to select a phase change material with a phase change temperature that matches the expected operating environment based on your specific thermal energy storage needs.
- Another thing is that it must be encapsulated. This is because effective encapsulation prevents leakage or contamination of the PCB during use. This can enhance the service life and reliability of the system to a certain extent.
Advantages and disadvantages of phase change materials
Advantages
- Higher energy storage density: PCM can store more energy as latent heat than traditional hydrothermal storage methods. Compared to water, it can store more heat per unit volume of mass and has a higher thermal storage efficiency.
- Smaller temperature difference between storage and release: The temperature remains relatively constant during the phase change process, which improves the stability and efficiency of thermal energy storage and release.
- Versatile operating temperature range: Different types of PCMs are available to cover a wide range of needs from low temperatures (-20°C) to high temperatures (over 100°C).
- Cyclability: The material can support thousands of melting and solidification cycles, making it particularly suitable for energy storage systems that are used repeatedly over a long time.
Disadvantages
- High initial investment: PCM materials are relatively expensive to develop, manufacture, and integrate into systems, which may limit large-scale deployment.
- Low thermal conductivity affects the rate of heat transfer: PCMs typically have low thermal conductivity, which results in slower rates of thermal energy storage and release.
- Limited Operating Temperature Range: The effective operating temperature range of PCMs is limited by their phase change temperature, which needs to be precisely selected for the specific application, making them less flexible.
- Encapsulation and Leakage Issues: PCMs are prone to leakage in the liquid state, especially inorganic salt materials that can corrode storage devices. Special encapsulation techniques are therefore required to prevent leakage.
- Storage efficiency affected by environment: PCM is sensitive to ambient temperature fluctuations. For example, when the high or low temperature is out of the phase transition range, it cannot take advantage of the energy storage.
The role of TES technology and PCM in decarbonization
TES technologies and PCMs are critical in low-carbon energy systems. Such systems can effectively avoid the problem of intermittency by storing and releasing heat rationally.
Coping with intermittent power
Renewable energy sources, such as wind and solar, have intermittent power generation processes, which can lead to unstable power output. PCM, combined with TES technology, can efficiently store waste heat and excess thermal energy and release it during peak periods. This greatly enhances the power supply capacity of the power plant and effectively solves the problem of intermittent power.
Reduced Energy Consumption and Increased Efficiency
By storing thermal energy through PCM, power plants can balance the supply and demand of thermal energy during power fluctuations and maintain efficient operation. This is because thermal energy storage technology effectively conserves heat that would otherwise be wasted in various forms. This energy is then released when it is needed, extending the plant’s operating capacity. This design maximizes efficiency.
At Trumonytechs, we can provide thermal management solutions tailored to specific needs. We also specialize in the research and application of PCM technology. We are committed to providing advanced thermal management solutions for electric vehicles, energy storage systems and heat transfer.
FAQ
The salts, salt hydrates, and paraffins we mentioned above are particularly suitable for heat storage. Of these, paraffin and salt hydrates are suitable for low and medium temperature building heat storage needs, while salt materials such as nitrates are more suitable for high temperature heat storage.
The most economical is water, while molten salts or metals can be heated to higher temperatures and have better energy absorption.
PCB materials release and absorb large amounts of energy externally by melting and solidifying.
