Ice storage air conditioning is the process of using ice for thermal energy storage. This is practical because of water's large heat of fusion: one metric ton of water (one cubic metre) can store 334 megajoules (MJ) (317,000 BTU) of energy, equivalent to 93 kWh (26.4 ton-hours).

Cryogenic energy storage (CES) is the use of low temperature (cryogenic) liquids such as liquid air or liquid nitrogen as energy storage. Both cryogens have been used to power cars. The inventor Peter Dearman initially developed a liquid air car, and then used the technology he developed for grid energy storage. The technology is being piloted at a UK power station.

Sensible heat of molten salt is also used for storing solar energy at a high temperature. It is termed molten-salt technology or molten-salt energy storage (MSES). Molten salts can be employed as a thermal energy storage method to retain thermal energy. Presently, this is a commercially used technology to store the heat collected by concentrated solar power (e.g., from a solar tower or solar trough). The heat can later be converted into superheated steam to power conventional steam turbines and generate electricity in bad weather or at night. It was demonstrated in the Solar Two project from 1995-1999. Estimates in 2006 predicted an annual efficiency of 99%, a reference to the energy retained by storing heat before turning it into electricity, versus converting heat directly into electricity.^[12][13][14] Various eutectic mixtures of different salts are used (e.g., sodium nitrate, potassium nitrate and calcium nitrate). Experience with such systems exists in non-solar applications in the chemical and metals industries as a heat-transport fluid.

The salt melts at 131 °C (268 °F). It is kept liquid at 288 °C (550 °F) in an insulated "cold" storage tank. The liquid salt is pumped through panels in a solar collector where the focused sun heats it to 566 °C (1,051 °F). It is then sent to a hot storage tank. With proper insulation of the tank the thermal energy can be usefully stored for up to a week.

A common approach to thermal energy storage is to use materials known as phase change materials (PCMs). These materials store heat when they undergo a phase change, for example, from solid to liquid, from liquid to gas or from solid to solid (change of one crystalline form into another without a physical phase change).

The phase change “solid-to-liquid” is the most used, but also solid-to-solid change is of interest. These materials can be used as an effective way of storing thermal energy (solar energy, off-peak electricity, industrial waste heat). In comparison to sensible heat storage systems, the latent heat storage has the advantages of high storage density (due to high latent heat of fusion) and the isothermal nature of the storage process. The heat of fusion or the heat of evaporation is much greater than the specific heat capacity. The comparison between latent heat storage and sensible heat storage shows that in latent heat storage storage densities are typically 5 to 10 times higher.

NASA’s Game Changing Development is taking on a technology development and demonstration effort to design, build, and test the next generation of Phase Change Material Heat Exchangers (PCM HXs) on the International Space Station. The primary objective of the task is to develop a PCM HX that operates through numerous freeze and thaw cycles without risking the structural integrity of the heat exchanger.