Latent Heat Essay

Latent Heat

Latent heat thermal storage is an alternative to the sensible heat system. This system operates by making use of the ability of the material to store energy through its ability to phase change from solid to liquid or liquid to solid. (Sharma, Tyagi, Chen, & Buddhi, 2009). The process relies on the chemical properties of the chosen material where heat is absorbed or release as the material undergoes a phase change from solid to liquid or vice versa. (Sharma, Tyagi, Chen, & Buddhi, 2009). The process starts when the temperature reaches the required temperature-phase change temperature- and stays constant until the whole process change is finished. Most of the latent heat thermal storage systems are currently based on solid to liquid transition.

The graph below shows the heat storage for a latent heat system in the case of a solid-liquid change.

Figure 1: heat storage as latent heat for a solid-liquid phase change (Mehling & Cabeza, 2008)

The thermal storage capacity of a latent heat system for the case of material undergoing a solid-liquid phase change can be seen below (Portaspana, 2011):

Q= ∫_(T_i)^(T_m)▒〖m. C_p dT+ m.∝_m.∆h_m+∫_(T_m)^(T_f)▒〖m.C_p.dT〗〗

A latent heat system has two main advantages over a sensible system:

It allows large amount of energy to be stored with only small changes in temperature thus allowing the system to have a high storage density.

The phase change process occurs over a long period with allows any temperature change to be controlled properly.

Ice based technology

Ice based technology also known as ice storage air conditioning is the process of using ice to store energy. This method is used in order to decrease the energy usage cost by transferring the energy consumption from high ...

... middle of paper ...

...o turn it back into a high pressure gas. The gas is then used to turn a turbine and a generator to produce electricity (Liquid Air Energy Netwrok, 2012).

Below is a representation of how the cryogenic energy storage operates.

Figure 4: representation of cryogenic energy storage system (Highview power storage, 2011)

A pilot plan was set up in Slough, United Kingdom with the aim of producing 300kW by using the liquid air cycle. The results obtained were promising with a process efficiency of 50-60% being achieved through the recycling of thermal energy produced during power recover process (University of Birmingham, 2013). The system may still lag behind in terms of efficiency if compared to some batteries but it possesses the advantage of having an almost unlimited amount of charge and discharge cycle without any loss in storage capacity (Lombardo, 2013).