Heat is essential for everyday tasks, from staying warm in winter to doing laundry.
However, as we face climate change, the rising energy consumption of buildings is becoming a significant problem.
Currently, heat is mostly produced by burning fossil fuels like coal, oil, and gas. To shift to clean energy, we need new ways to produce and store heat.
Researchers at Georgia Tech’s George W. Woodruff School of Mechanical Engineering are developing more efficient heating systems that don’t rely on fossil fuels.
They found that combining two common salts can help store clean energy as heat.
This stored heat can then be used for warming buildings or combined with a heat pump for cooling.
The research, led by Assistant Professor Akanksha Menon, was published in the Journal of Energy Storage.
The study focuses on a simple reversible chemical reaction for heat storage: one reaction absorbs heat and stores it, while the reverse reaction releases the heat for use.
Professor Menon has been passionate about thermal energy storage since her Ph.D. work. When she started the Water-Energy Research Lab at Georgia Tech, she aimed to develop storage technology and materials and find ways to integrate them into buildings.
She wanted to understand the fundamental material challenges to create better storage solutions.
The key to their research is salt. Each salt molecule can hold water molecules within its structure. To store heat, researchers dehydrate the salt, causing it to release water vapor. To release the stored heat, they hydrate the salt, which makes the salt structure expand to accommodate the water molecules. This expansion and contraction process, however, can stress the salt and eventually cause it to fail, similar to how lithium-ion batteries wear out after many charge-discharge cycles.
Professor Menon and her Ph.D. student, Erik Barbosa, experimented with combining different salts to improve this process. They tested six salts over two years and found that magnesium chloride and strontium chloride worked well together. Magnesium chloride absorbs too much water and fails quickly, while strontium chloride hydrates very slowly. Together, their strengths and weaknesses balance out, improving heat storage.
Their next step is to develop containers for these salts for heat storage. They plan to demonstrate a system where salts are packed in a drum. Hot air will flow over the salts, dehydrating them and storing energy like a battery. To release the stored heat, humid air will be blown over the salts, rehydrating them and releasing heat for use in buildings.
This technology could provide climate-friendly energy solutions. Unlike expensive alternatives like lithium batteries, salt is cheap and widely available, making its implementation fast and cost-effective. Salt-based thermal energy storage could significantly reduce carbon emissions, playing a crucial role in combating climate change.
