The experimental apparatus for storing thermal energy includes a piston applying pressure within the PCM container. The heat source or the heating pads is at the bottom-most part of the apparatus.
A PCM absorbs and releases energy provided to it. PCM apparatus has attracted more attention currently because of the shift towards renewable energy sources from fossil fuels. Fossil fuels are only available intermittently and would exhaust someday or the other. Thus, always require an alternate.
Sunlight is not present at night/cloudy days, and wind speed varies every day (every hour). Thus, we cannot use their energies all the time. Instead, we must store it when created in bulk. PCM can be a storage solution, but its uses are limited to technical challenges.
Researchers say that a thermal storage system contains two main scales. The first scale is energy density, which refers to the energy stored per unit volume/mass. The second one is the power density, which refers to the rate of extracting the stored energy from a system per unit volume/mass.
It is good to have high levels of both scales, but most apparatuses either contain high energy density plus low power density or high power density plus low energy density. An example of this is a block of ice and a metal block.
Till today people are handling these systems by mixing the two apparatuses. Hence, they create composites while keeping some volume fraction as a metal matrix to help conduct heat and good power density. But, because of this, storage material decreases, and energy density is also lost in the process.