Sensible Heat Storage | Methods, Key Features, and Disadvantages

Introduction

The simplest method for storing heat is through sensible heat storage. This involves increasing the temperature of a liquid or solid to store heat and releasing the heat by lowering the temperature when needed. To store energy on a global scale, huge volumes are required. The materials used for sensible heat storage should have a high heat capacity and a high boiling or melting point. Although this method is currently less efficient for heat storage, it is the simplest and least expensive compared to latent or chemical heat storage.

Thermodynamics Perspective:
From a thermodynamic standpoint, sensible heat storage relies on increasing the enthalpy of the material, which is usually a liquid or solid. The result of this process is a temperature change. The amount of heat stored can be calculated using the following equation:

Q = m ⋅ c⋅ ΔT

where:

• Q is the stored heat.
• m is the mass of the material.
• c is the specific heat capacity of the material.
• ΔT is the temperature change.

Sensible Heat Storage (SHS) Method

Sensible Heat Storage (SHS) is the most traditional and widely used Thermal Energy Storage (TES) method. It is simple to operate and reasonably priced. However, it has a lower energy storage density than Latent Heat Storage (LHS) and Thermochemical Heat Storage (TCHS). In SHS, energy is stored by raising the temperature of a storage medium (such as water, oil, sand, or rock). When needed, the power is released by lowering the temperature of the medium.

Key Features and Benefits of Sensible Heat Storage

1. Simple Operation: Easy to use and manage.
2. Repetitive Use: The charging (storing heat) and discharging (releasing heat) cycles can be repeated without any issues.
3. Material Properties: Utilizes materials with high specific heat capacity and density, like water, which can store a significant amount of heat.
4. Storage Capacity: The amount of heat stored (Q) depends on the mass (m), heat capacity (c), and temperature change (ΔT) of the storage material. Water, for example, has a high specific heat and density, making it an effective storage material. For instance, water can store up to 250 MJ/m³ for a temperature change of 60°C.
5. Practical Applications: SHS is widely used in solar applications, such as

• Solar Water Heaters
• Space Heating and Cooling
• Greenhouse Heating
• Solar Cooking
• Waste Heat Recovery Systems

6. Performance Factors: Key factors affecting the performance of SHS systems include:

• Thermal Conductivity: Influences how quickly heat is transferred in and out of the storage material.
• Thermal Diffusivity and Flow Rate: Important for efficient charging and discharging cycles.
• Thermal Stratification: Helps maintain temperature layers within the storage medium, enhancing energy quality.

Sensible Heat Storage Materials (SHSMs)

Various reviews on Thermal Energy Storage (TES) solutions look at commonly used Sensible Heat Storage Materials (SHSMs) properties. These reviews compare different factors such as physical, chemical, thermal, environmental, and economic aspects to meet construction or industrial needs. SHSMs can be either solid or liquid.

Common SHSMs

• Liquid Storage Materials: Water, oils, pure alcohol, and its derivatives.
• Solid Storage Materials: Rocks, stones, bricks, concrete, dry and wet soils, wood, plasterboard, and cork.

Classification of Solid SHSMs

According to Fernández et al., solid SHSMs can be classified into:

• Metals and Alloys
• Ceramics and Glasses
• Polymers and Elastomers
• Hybrids

Properties and Considerations of Sensible Heat Storage

• Thermophysical Properties: Table 4 lists the thermal properties of commonly used SHSMs.
• Longevity Factors: SHSMs must have thermal and chemical stability, meaning they should maintain their properties without decomposing or degrading, even with many charge/discharge cycles.
• Material Requirements: According to Klein et al., ideal storage materials should conduct heat well, have high specific heat and density, operate within a suitable temperature range, and be cost-effective.
• Advantages and Disadvantages
• Water: The most commonly used SHSM due to its availability, non-toxicity, low cost, and high specific heat capacity.
• Liquid SHSMs: Have a higher specific heat capacity but face challenges like storage infrastructure costs, heat exchanger costs, leak risks, and large tank requirements.
• Solid SHSMs: Face issues such as low density, high investment costs, and long-term self-discharge risks.

Research and Developments

• Almendros-Ibáñez et al. reviewed techniques for storing solar energy in particle beds, highlighting packed and fluidized beds.
• While liquid SHSMs have higher specific heat, their practical use is limited by the infrastructure and costs associated with their storage.

In summary, while SHSMs, especially water, are widely used and effective, some challenges and limitations must be addressed for optimal performance and cost-efficiency in different applications.

Advantages of Sensible Heat Storage

1. High Efficiency: Especially with high thermal stratification.
2. Inexpensive Materials: Uses readily available materials like water.
3. Scalability: Can be scaled to meet large energy storage needs.

Disadvantages of Sensible Heat Storage

1. Low Energy Density: Requires large volumes of material to store significant energy.
2. Self-discharge: Some energy loss over time.

Frequently Asked Questions (FAQs)

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