Thermal energy storage

Depletion of traditional fuel reserves and the exacerbating effects of human-induced climate change through greenhouse gas emissions have sparked unparalleled global interest in renewable energy sources. One promising avenue in this burgeoning field is the harnessing of solar energy for electricity generation. This conversion process can be achieved either directly through photovoltaic cells or indirectly through concentrated solar power (CSP) plants. The vast, inexhaustible, environmentally friendly, and renewable nature of solar energy necessitates its effective utilization to bridge the widening gap between escalating energy demands and finite conventional resource supplies.

Packed-bed sensible Thermal Energy Storage Systems (TESs) store heat by alternately heating and cooling solid particles using a heat transfer fluid (HTF) flowing through the beds. These TESs offer numerous advantages, including cost-effective storage materials, a broad working temperature range, direct heat exchange between the HTF and storage material, and high chemical stability with minimal degradation and corrosion. Consequently, there is significant value in the development of efficient high-temperature packed-bed thermal energy storage systems to address the heat requirements of various industries.

Thermal energy storage (TES) systems have been introduced as an attractive way to store solar energy. TES systems could be utilized in building air conditioning systems and solar domestic hot water (SDHW) systems. Generally, three forms of storing energy in TES systems could be applied: sensible, latent, and thermochemical. Among these three categories, latent thermal energy storage (LTES) systems are preferred due to their high energy storage capacity and low temperature variation during the charging and discharging process. For the same volume, latent TES using Phase Change Materials (PCMs) can store 5–14 times higher energy than TES using sensible storage materials. As a result, the PCM systems have gained much attention in solar energy storage-recovery applications, waste heat recovery, and energy savings in buildings.

Although PCMs have high energy storage capacity, their poor thermal conductivity is a major challenge, especially in solidification, where the conduction heat transfer is mainly dominated, and natural convection is less effective. Therefore, novel techniques and optimized designs could be used for an improved melting and solidifying performance of the PCMs.

Thermal management and phase change heat transfer for electronics cooling

Recent advancement in communication and electronic industries has led to the introduction of higher power for electronic chips while having more compact size. Operating temperature range has been identified as a critical factor for efficiency in integrated circuit, therefore the design of cooling devices is crucial in excessive heat removal. Effective thermal management is vital to keep the temperature of electronic device below their maximum allowable operating temperature to increase the lifespan of electronic device and to prevent sudden shutdown. In light of the overheating issue in electronic devices, an efficient and novel cooling technology is deemed necessary.

Incorporation of PCMs into heat sinks is an efficient method, used for controlling the temperature of electronics specially, when facing intermittent heat fluxes or thermal shocks. High thermal storage density of PCMs is an advantage that allows the compact design of a passive LHTMS (latent heat thermal management system). Weak thermal conductivity is the crucial drawback of PCMs, on the other hand. Therefore, novel techniques should be applied to overcome this drawback. 

Boiling and condensation heat transfer and two-phase flow patterns

Two phase flow (condensation or evaporation) in tubes occurs in many operative engineering processes such as condensers, evaporators and air-conditioning processes. For optimal design of condensers and evaporators, it is crucial to obtain knowledge about two phase flow patterns and convective heat transfer characteristics. Significant energy saving can be achieved by maximum enhancement of heat transfer and minimum increment of frictional pressure drop in industrial applications, such as air-conditioning and refrigeration systems.