Advantages and limitations of sensible, latent, and thermochemical heat storage systems
Description Advantages
Sensible
Latent
Thermochemical
• Efficient heat storage and release without
• High storage density • Temperature stability • Compact system (i.e., smaller weight and volume)
• High volumetric storage
density
changing phases
• Low volume requirement • Long energy preservation duration periods with limited heat loss • Low storage (ambient) temperature
• Easy to load and unload
• Quick to insulate
Limitations
• Cannot store or release energy at a constant • The system is bulky • Requires more storage medium than latent heat systems to store the temperature same amount of energy
• Low thermal conductivity
• Limited reactivity and reversibility of chemical
and stability
• Medium heat of fusion
reactions
• Requirement for harsh reaction conditions • Toxic and corrosive byproducts from reactions
Table 1
heat capacity of 0.48 kJ/kg·K, whereas iron has a slightly lower specific heat capacity of 0.452 kJ/kg·K. These materials are effective due to their ability to absorb and retain heat efficiently (Khatod, et al., 2022) . On the other hand, liquid storage materials contain substances like therminol, engine oil, ethanol, butane, and propane. For example, water has a specific thermal heat capacity of 4.19 kJ/kg·K at 20-100°C, ethanol has 2.4 kJ/kg·K up to 78°C, butanol has 2.4 kJ/kg·K up to 118°C, and engine oil has 1.88 kJ/kg·K up to 160°C. Sensible heat storage mediums made of solid materials have an advantage over liquids due to their ability to handle larger temperature fluctuations. Unlike liquids, solid thermal storages do not change phase, meaning they do not melt or flow, which eliminates the risk of leakage from the storage container. Conventional thermal energy storage methods, such as those using molten salt, have been widely adopted. However, these systems are expensive, have a limited lifespan, and often rely on materials that are harmful to the environment. Latent heat storage, also referred to as phase change heat storage, operates by absorbing and releasing thermal energy during a material’s phase transition. This type of storage has a higher energy density compared to conventional
sensible heat storage due to the substantial enthalpy changes occurring during the phase transition. Typically, latent heat storage systems are lighter and more compact, which can result in reduced costs compared to sensible heat storage systems. Latent heat storage utilising phase change materials has diverse applications, including solar thermal storage, enhancing energy efficiency in buildings, and recycling waste heat. Salt hydrates, for example, have latent heat capacities of 115.5-280 kJ/kg and phase change temperatures of 29-117°C. Paraffin wax stores about 202 kJ/kg of heat and changes phases at 40-45°C. Paraffin C14 has the highest latent heat of 228 kJ/kg. Salt eutectics, which are salt mixtures, have heat capacities of 74-790 kJ/ kg and phase change at 13-767°C. Carbonate salts are used for high-temperature applications, with heat capacities of 142-509 kJ/kg and phase change temperatures of 732-1,330°C. These materials are chosen for their thermal properties to improve energy storage efficiency at different temperatures. Thermochemical heat storage utilises reversible chemical reactions to store and release energy efficiently. Energy is stored as chemical compounds produced by an endothermic reaction. When these compounds
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