Thermal Battery Technology: Overview & Applications
Thermal battery technology offers a fresh approach to energy storage and to the key challenges in our power systems. These devices store energy as heat, rather than electrical charge, opening up new possibilities for managing resources efficiently.
Thermal batteries can capture excess heat from various sources - storing energy that can later be converted back to electricity or used directly for heating, making the technology versatile and potentially very efficient.
As renewable sources become more common, the need for effective energy storage grows. Thermal batteries could play a significant role here, helping to balance the intermittent nature of wind and solar power with our constant demand for electricity.
Thermal battery technology represents a promising and versatile energy storage and management approach. By storing thermal energy, this technology can enhance the performance of renewable energy systems, improve industrial efficiency, and provide a reliable resource for critical applications. For this reason, thermal battery technology will be key in transitioning to a more sustainable and efficient future.
Let's explore how this technology works and where it might make the biggest impact, starting from the basic principles of heat exchange.
Understanding Thermal Battery Technology
A thermal battery is based on thermal energy storage instead of electrical storage. The concept of a thermal battery involves capturing heat from various sources, such as solar power, waste heat from industry, or even the combustion of fossil fuels and storing it for later use.
Thus although we speak of "batteries", we are dealing with a different topic from the EV batteries we dealt with until now in our blog and the issues associated with an EV battery cooling system.
Thermal energy storage can be used as a source to extract heat, provide heating, generate electricity, or drive industrial processes.
A thermal battery operates using materials with high capacity and conductivity, such as phase change materials (PCMs) or molten salts. High thermal capacity materials have the function to absorb and store heat during a phase transition, such as melting, and release it when they solidify.
The heat transfer fluid circulates through the system, transferring heat to and from the storage medium. The working fluid is fundamental for efficient thermal energy transfer, ensuring minimal losses and optimal thermal performance throughout.
A Little Bit of Physics of Thermal Batteries
The basic principle of a thermal battery can be expressed mathematically as:
Q = m c ΔT
where:
Q is the amount of heat stored or released (in Joules)
m is the mass of the medium (in kg)
c is the specific heat capacity of the medium (in J/kg·K)
ΔT is the change in temperature (in K)
For PCMs, an additional term is added to account for the latent heat of fusion:
Q = m [c_s ΔT_s + L + c_l * ΔT_l]
(where c_s = specific heat capacity of the solid phase, ΔT_s = temperature change in the solid phase, L = latent heat of fusion, c_l = specific heat capacity of the liquid phase, and finally ΔT_l = temperature change in the liquid phase).
Types of Thermal Batteries
In this section, we will shortly review the main types of thermal batteries.
Phase Change Material (PCM) Thermal Battery
During melting and solidification, PCMs absorb and release thermal energy. PCM batteries leverage this property to store and release large amounts of thermal energy.
Common PCMs include lithium chloride and various organic and inorganic compounds. These materials are selected based on their melting points, thermal conductivity, and capacity to match specific application requirements.
Other Types of Batteries
Molten salt batteries store thermal energy using salts that melt at high temperatures.
Salt systems can operate at temperatures exceeding 500°C, making them suitable for high-temperature applications like industrial processes and combined heat and power (CHP) systems.
Molten salt systems are particularly effective for waste heat recovery and solar thermal energy storage.
In sensible heat thermal batteries, energy is stored by raising the temperature of a solid or liquid without changing power density or its phase. Common materials include water, oil, and concrete. The amount of storage is directly proportional to the temperature change and the material's heat capacity. The energy storage capacity (Q) can be calculated using the Q = m c ΔT equation.
In thermochemical heat storage, heat is stored through reversible chemical reactions. In an endothermic reaction, energy is stored by breaking chemical bonds and released when reversed. The general equation for thermochemical heat storage is:
A + Heat ⇌ B + C
Applications of Thermal Batteries
In this section, we will review some of the main applications of thermal batteries, starting from renewable energy integration.
Thermal batteries are critical in integrating renewable energy sources like solar and wind power into the grid. A thermal battery stores excess thermal energy generated during peak production times, providing a consistent supply, even when the Sun isn’t shining, or the wind isn’t blowing! Of course, constant supply capability enhances the reliability and stability of renewable energy systems, reducing our dependence on traditional sources.
.jpeg)
Industrial Processes
Thermal batteries can be used in industrial facilities to recover waste heat. The thermal battery captures heat generated by steel manufacturing or chemical production and stores it for later use to preheat materials, generate steam, or drive other industrial processes, improving efficiency and reducing operating costs.
Combined Heat and Power (CHP) Systems
CHP systems use thermal batteries to store excess heat generated during electricity production. The stored heat can be used for space heating, hot water, or additional power generation. CHP systems achieve higher overall efficiency than traditional power generation methods.
Military and Aerospace Applications for Thermal Battery
Thermal batteries have been used in military and aerospace applications for decades, particularly in powering systems that require long shelf life and high reliability.
Their characteristics make them ideal for use in:
Spacecraft: They are used in various space missions, powering critical systems during launch, re-entry, or emergencies.
Missiles: examples are guidance systems and other electronic components.
Emergency and backup systems: In military aircraft and naval vessels, they serve as reliable backup power sources.
They can operate in extreme conditions, including high G-forces, extreme temperatures, and high altitudes. They provide a maintenance-free and robust solution for critical applications, with the ability to remain dormant for long periods and activate quickly when needed. Their high power density and rapid activation (typically in milliseconds) make them particularly suitable for these applications. Their long shelf life, often exceeding 20 years, ensures readiness even after extended storage periods. Recent advancements have focused on their miniaturization, making them even more suitable for modern military and aerospace systems where space and weight are at a premium.
Grid Stabilization and Load Leveling
Thermal batteries can help stabilize the electrical grid by storing excess energy during low-demand periods and releasing it during peak demand.
The equation representing load leveling is
P_net = P_generation - P_demand ± P_storage
where P_net is the net power on the grid, P_generation is the power generated, P_demand is the power demanded, and P_storage is the power stored or released by the thermal battery.
Thermal batteries can be integrated into building heating and cooling systems storing thermal energy during off-peak hours and releasing it during peak demand, reducing strain on the grid.
The potential savings (E_savings) can be estimated using:
E_savings = E_peak - E_off-peak
E_peak is the consumption during peak hours, and E_off-peak is the consumption during off-peak hours.
Advantages of Thermal Batteries
This section will shortly review the main advantages of thermal batteries.
Higher Efficiency and Lower Cost
Thermal batteries offer high efficiency in storing and releasing thermal energy, with minimal performance degradation over time.
The relatively significantly lower cost compared to electrical batteries makes them an attractive option for large-scale energy storage applications.
Scalability and Versatility
Thermal battery systems can be scaled to match the energy storage needs of various applications, from small residential systems to large industrial installations.
The battery versatility allows them to integrate existing facilities and infrastructure, providing a seamless transition to more efficient energy use.
Sustainability and Clean Energy
Thermal batteries provide a clean solution that supports the transition from fossil fuels. By facilitating the use of renewable sources and improving the efficiency of systems, they also contribute to sustainability and the reduction of greenhouse gas emissions.
Long Lifespan and Low Maintenance
Thermal batteries typically have a longer lifespan than electrochemical batteries, often lasting for decades with minimal degradation. The absence of complex chemical reactions reduces the need for regular maintenance, lowering operational costs.
High Energy Density
Thermal batteries, especially those using PCMs, can store large amounts of energy in a relatively small volume - this is the concept energy density (ρ_E) of a thermal battery, that can be calculated using ρ_E = Q / V where V is the volume of the storage medium.
Challenges and Future Prospects
What are the main challenges and prospects for thermal batteries and thermal storage?
Material and Design Optimization. The performance of thermal batteries heavily depends on the materials' properties and the system's design.
Ongoing research aims to develop new materials with higher thermal capacity and conductivity and optimize the design of heat transfer fluids and thermal storage and mediums to enhance efficiency and reduce costs.
Integration with Existing Technologies. Integrating thermal battery technology with existing systems and infrastructure presents opportunities and challenges. Developing standardized solutions and ensuring compatibility with various processes and renewable energy systems is vital for widespread adoption.
Market Adoption and Regulatory Support. Widespread adoption of thermal battery technology requires market acceptance and supportive regulatory frameworks. Policies that incentivize the use of clean energy technologies can accelerate the deployment of thermal batteries and drive innovation in this field.
Conclusions
Thermal batteries are versatile tools that provide a balance between intermittent energy generation and consistent demand. We have reviewed how these systems utilize basic principles of heat transfer and thermal energy storage to offer a cost-effective approach to storing and utilizing energy across various applications.
The ability of thermal batteries to integrate with renewable energy sources, improve industrial efficiency, and provide reliable power for critical applications positions them as a key technology in the transition to a more sustainable energy future. Their advantages include scalability, long lifespan, and relatively low cost, making them an attractive option for both small-scale and large-scale energy storage needs.
However, the widespread adoption of thermal battery technology still faces challenges. Ongoing research and development efforts are needed to optimize materials, improve system designs, and enhance efficiency. Additionally, integrating thermal batteries with existing infrastructure and developing supportive regulatory frameworks will be crucial for their successful implementation.
We can expect thermal batteries to become an increasingly integral part of our infrastructures, contributing significantly to our sustainability goals and overall security.
