Phase change materials technology for storing thermal energy, solar electricity in buildings – pv magazine international

NREL scientists have unveiled a storage system based on a phase change material that can store both thermal energy and electricity in a single device. According to the researchers, the new technology could be used to store excess electricity produced by on-site solar or wind operations in large-scale buildings.

A research group at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has developed a dynamically adjustable phase change material (PCM) that can be used to store both thermal energy and heat. electricity if applied in buildings.

PCMs are substances that absorb and release thermal energy when they change phase and are able to store and release large amounts of latent heat over a defined temperature range. In the construction sector, by combining building materials with PCM is an effective way to improve the thermal energy storage capacity of building elements.

“However, one problem with phase change materials is that they generally only work within a range of temperatures,” the scientists said. “This means that two different materials would be needed for summer and winter, which increases… the cost.” In order to solve this problem, the NREL team modified the transition temperature (Tm) of an MCP using ions with very modest voltage requirements. The transition temperature is the minimum temperature at which a material changes its crystal structure to another.

A double ion battery (DIB) was used electrochemically alter the salt concentration in the MCP and, therefore, change its Tm reversibly and dynamically. In a DIB, a PCM with a high initial salt concentration and a low Tm serves as an electrolyte for the device, ”the scientists explained. “The electrochemical charge stores cations and anions in negative and positive electrodes, respectively. “

The PCM, salt and electrodes have been optimized so that the DIB works as a dynamically adjustable device. “It works as a thermal and electric battery,” said corresponding research author Gao Liu. “In addition, this capability increases the potential for thermal storage due to the ability to adjust the melting point of the material based on different ambient temperatures.

The proposed technology is supposed to reduce storage costs, as the same material can be used all year round instead of just half. “If we use thermal energy storage, in which raw materials are more abundant to meet the demand for thermal loads, it will release some of the demand for electrochemical storage and free up batteries for use where the storage of thermal energy cannot be used. said research co-author Sumanjeet Kaur.

Full details of the storage technology can be found in the study Dynamic tuning of transition temperatures of phase change materials using ions for thermal energy storage, which was recently published in Physical Sciences Cell Reports. “In large-scale building construction, this combined thermal and electrical energy storage capacity would allow the material to store excess electricity produced by on-site solar or wind operations, to meet both thermal (heating and cooling) and electric, ”the academics concluded. .

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