Researchers at Berkeley Lab reported breakthroughs in phase change materials that will increase the affordability of thermal energy storage. Phase change materials can be added to the walls and automatically keep the building cool or warm according to the ambient temperature. (Source: Jenny Nuss/Berkeley Lab)

Can a can of ice or hot water become a battery? Yes! If a battery is a device for storing energy, then storing hot or cold water to power the heating or air-conditioning system of a building is another type of energy storage. The technology known as thermal energy storage has existed for a long time, but it is often overlooked. Now, scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) are working together to take thermal energy storage to a new level.

In order to overcome some of the limitations of traditional water-based thermal energy storage, scientists at Berkeley Lab are researching and developing next-generation materials and systems that can be used as heating or cooling media. They also created a framework for cost analysis and a tool to compare cost savings. In a series of papers published this year, researchers at Berkeley Lab reported important advances in these areas.

"It is very challenging to decarbonize buildings, especially heating," said Ravi Prasher, deputy director of the Energy Technology Laboratory at Berkeley Lab. "But if you store energy in the form of end-use, that is, heat, rather than in the form of energy supply, that is, electricity, cost savings can be very dramatic. Now with the framework we have developed, we will be able to weigh thermal energy storage versus The cost of electricity storage, such as lithium batteries, was impossible before."

In the United States, building energy consumption accounts for 40% of total energy consumption. Of these, almost half is used for thermal loads, including space heating and cooling, and water heating and cooling. In other words, one-fifth of all the energy produced is used for the heat load of the building. By 2050, with the phasing out of natural gas and more and more electricity for heating, the demand for heat load on the grid is expected to increase sharply.

"If we use thermal energy storage, where the raw materials are more abundant to meet the demand for thermal load, this will relax some of the demand for electrochemical storage and release the battery to places where thermal energy storage cannot be used," the person in charge of the Thermal Energy Group at Berkeley Laboratories Sumanjeet Kaur said.

Berkeley Lab scientists Ravi Prasher (left) and Sumanjeet Kaur are leading an effort to develop thermal energy storage to decarbonize buildings. (Source: Thor Swift/Berkeley Lab)

As our society continues to electrify, the demand for battery storage energy is expected to be huge. By 2030, the annual output of batteries is expected to reach 2 to 10 terawatt hours (TWh) from the current 0.5 TWh. In the foreseeable future, lithium-ion batteries will become the main storage technology. A key constraint is the limited supply of raw materials, including lithium, cobalt and nickel, which are the basic components of today's lithium batteries. Although Berkeley Labs is actively working to address this limitation, alternative forms of energy storage are also needed.

"Lithium batteries are now facing tremendous pressure on the supply of raw materials," Prasher said. "We believe that thermal energy storage can be a viable, sustainable, and cost-effective alternative to other forms of energy storage."

Thermal energy storage can be deployed at various scales, including in a single building—for example, in your home, office, or factory—or at the district or regional level. Although the most common form of heat energy is the use of hot or cold water in large tanks, there are other types of so-called sensible heat storage, such as the use of sand or rocks to store heat energy. However, these methods require a lot of space, which limits their applicability in residences.

To solve this limitation, scientists have developed high-tech materials to store thermal energy. For example, phase change materials absorb and release energy as they transition between phases, such as from liquid to solid and back.

Phase change materials have many potential applications, including thermal management of batteries (to prevent them from becoming too hot or too cold), advanced textiles (think of clothes that can automatically keep you warm or cool, thereby achieving thermal comfort, and at the same time Reduce building energy consumption) and dry cooling of power plants (to save water). In buildings, phase change materials can be added to the walls, just like thermal batteries in buildings. When the ambient temperature rises above the melting point of the material, the material undergoes a phase change and absorbs heat, thereby cooling the building. Conversely, when the temperature drops below the melting point, the material undergoes a phase change and releases heat.

However, a problem with phase change materials is that they usually only work within a temperature range. This means that two different materials will be required in summer and winter, which increases costs. Berkeley Lab set out to overcome this problem and achieve the so-called "dynamic tunability" of the transition temperature.

The figure shows two different ways of integrating thermal energy storage in a building. Thermal batteries (powered by phase change materials) can be connected to a building's heat pump or traditional HVAC system (left), or phase change materials can be incorporated in the wall. (Credit: Berkeley Lab)

In a recent study published in Cell Reports Physical Science, researchers took the lead in realizing dynamic tunability in phase change materials. Their breakthrough method uses ions and a unique phase change material to combine thermal energy storage and electrical energy storage, so it can store and supply heat and electricity.

"This new technology is truly unique because it combines heat and electricity into one device," said Gao Liu, co-corresponding author of the study and head of the Applied Energy Materials Group. "It functions like a thermal battery and a battery. More importantly, because the melting point of the material can be adjusted according to different ambient temperatures, this ability increases the heat storage potential. This will significantly improve the utilization of phase change materials. ."

Kaur, who is also a co-author of the paper, added: “From a larger perspective, this helps reduce storage costs because the same materials can now be used all year round, not just half a year.”

In large-scale building construction, this combined thermal and electrical storage capacity will enable the material to store excess electricity generated by on-site solar or wind energy operations to meet heat (heating and cooling) and electricity needs.

Another Berkeley Lab study earlier this year solved the problem of supercooling, which is super cool in some phase change materials because it makes the material unpredictable because it may not be the same every time Change phase at temperature. The research was led by Drew Lilley, a graduate assistant at Berkeley Lab and a PhD student at the University of California, Berkeley, and was published in the journal Applied Energy. It demonstrated for the first time a method for quantitatively predicting the supercooling performance of materials.

The third Berkeley Lab study published this year in Applied Physics Letters describes a method for understanding phase change at the atomic and molecular scale, which is essential for the design of new phase change materials.

"So far, most basic research related to phase change physics is computational in nature, but we have developed a simple method to predict the energy density of phase change materials," Prasher said. "These studies are important steps to pave the way for the wider use of phase change materials."

The fourth study just published in "Energy and Environmental Science" developed a framework for direct cost comparisons between batteries and thermal energy storage, which was not possible before.

Kaur said: "This is a very good framework for people to compare-Apple vs. Apple-batteries and thermal storage." "If someone comes to me and asks me,'I should install Powerwall (Tesla used to store solar Lithium battery systems) are still thermal energy storage systems, and there is no way to compare them. This framework provides a way for people to understand the cost of storage over the years."

The framework was developed with researchers from the National Renewable Energy Laboratory and Oak Ridge National Laboratory, and it takes into account life cycle costs. For example, the installation capital cost of the thermal system is low, the service life of the thermal system is usually 15 to 20 years, and the battery usually has to be replaced after 8 years.

Finally, a study conducted by researchers at the University of California, Davis and University of California, Berkeley demonstrated the technical and economic feasibility of deploying HVAC systems with phase-change material-based thermal energy storage. First, the team developed the simulation models and tools needed to evaluate the energy cost savings, peak load reduction, and cost of such systems. The tool will be open to the public and will allow researchers and builders to compare the system economics of HVAC systems with thermal energy storage and all-electric HVAC systems with and without electrochemical storage.

Spencer Dutton, project leader at Berkeley Lab, said: "These tools provide unprecedented opportunities to explore the economics of practical applications of HVAC with integrated thermal energy storage." "Integrated thermal energy storage allows us to Significantly reduce the capacity and cost of the heat pump, which is an important factor in reducing life cycle costs."

Next, the team continued to develop a "field-ready" prototype HVAC system for small commercial buildings, which uses cold and hot batteries based on phase change materials. Such a system transfers cooling and heating loads from the grid. Finally, the team is deploying a residential-scale live demonstration, focusing on household electrification and the transfer of household heating and hot water loads.

Noel Bakhtian, Executive Director of Berkeley Lab’s Energy Storage Center, said: “If you think about the way energy is consumed around the world, people will think it is consumed in the form of electricity, but in fact it is mainly consumed. Consumed in the form of heat." "If you want to decarbonize the world, you need to decarbonize buildings and industries. This means you need to decarbonize heat. Thermal energy storage can play an important role there."

The research was supported by the Building Technology Office of the Energy Efficiency and Renewable Energy Office of the Department of Energy.

Lawrence Berkeley National Laboratory was established in 1931. It firmly believes that the biggest scientific challenge is best solved by the team. Lawrence Berkeley National Laboratory and its scientists have won 14 Nobel Prizes. Today, Berkeley Lab researchers develop sustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and explore the mysteries of life, matter, and the universe. Scientists from all over the world rely on laboratory facilities to carry out their own discovery science. The Berkeley Laboratory is a multi-project national laboratory managed by the University of California for the Office of Science of the Department of Energy.

The Office of Science of the US Department of Energy is the largest supporter of basic research in the physical sciences of the United States, dedicated to solving some of the most pressing challenges of our time. For more information, please visit energy.gov/science.

– Kiran Julin contributed to this article.

In order to promote solutions and partnerships around specific challenges facing the United States in the future of energy storage, Berkeley Lab is holding a National Energy Storage Summit. The National Energy Storage Summit, which kicks off the future of energy storage in the United States, will be open to the public from March 8-9, 2022.

Contact: [Email Protection] | 510-486-5183

A Better Battery Market | November 17, 2021

Healthy buildings help stop the spread of Covid-19 and increase worker productivity CNBC | November 6, 2021

The Climate Crisis, in Numbers: A Guide to Humanity’s Greatest Challenges Buzzfeed | November 5, 2021

U.S. Department of Energy National Laboratory

Questions and Comments Privacy and Security Statement