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The pursuit of modern-day technologies means that new energy storage solutions are being sought. As it stands, most efforts tend to focus on small-scale energy storage, such as the electrochemical Li-ion battery. However, thermochemical batteries are becoming an increasing interest in large-scale energy storage solutions.
Thermal-based batteries have traditionally featured higher energy densities than electrochemical batteries but have been less stable, hence the rise of the electrochemical battery. Many thermal batteries have higher energy densities than electrochemical batteries, and focus has now turned to hybrid thermochemical batteries (which take principles from both thermal and electrochemical batteries) to provide a middle ground between stability and higher energy densities.
Thermochemical batteries have a higher theoretical energy density than Li-ion (and other electrochemical) batteries and are now commercialized. In recent news, a partnership between SaltX Technology and Sumitomo has been announced to commercialize nanocoated salt batteries focusing on large-scale energy storage for use in industrial settings.
Large Scale Commercialization of Thermochemical Energy Storage
The aim is to create a solution using SaltX Technology’s nanocoated salt battery technologies with Sumitomo’s fluidized bed technology to store energy on a large scale.
The batteries have already been developed by SaltX and are composed of calcium oxide materials enhanced with nanocoatings. The batteries are scalable because the storage tanks used within the batteries do not require any advanced or expensive materials, and they can be integrated with existing technologies.
Sumitomo has designed a fluidized bed reactor that can act as a discharge point for the batteries when the salt releases heat. A new 100 kW reactor has now been developed by the companies that combines the nanocoated salt batteries' energy storage potential with the large-scale potential of the fluidized bed technology.
The primary mechanism of the battery developed by SaltX is that energy is stored chemically by separating salt from water, which is then later released by combining them again. This is usually carried out on a small scale. The fluidized bed reactor mixes the salt and water vapor effectively on large scales, meaning that the energy storage (and release) reactions can be performed on much larger scales and used for large-scale energy storage.
The pilot is being commissioned at the beginning of 2021, and the plan for the near future is to scale up to discharge levels of 1 MW of thermal power. This article will look at the technology behind the batteries themselves and why they have the potential to be scaled up and store up to ten times more heat energy than other large-scale energy storage mediums.
Video Credit: SaltX Technology/YouTube.com
Nanocoated Salt Batteries
The nanocoated salt batteries bridge both electrochemical and thermal battery principles. As mentioned, electrochemical reactions occur within the battery system, producing heat. This heat is then stored as energy, which can be released as and when needed.
SaltX uses different metal oxide salts within its batteries (although calcium oxide salts have been touted for the scale-up project) and are functionalized on the surface with nanocoatings.
Different metal salts are used because they all have different properties. For example, some release lots of energy at high temperatures, whereas others use low temperatures to charge. All have different energy densities, and there is a range of materials that can be tailored to the intended application.
The salt nanocoatings are essential as they prevent corrosion and accumulation—the latter of which is vital in the working mechanism of these batteries as it allows low-cost metal salts to be used. The metal salts can also be charged and discharged thousands of times without degrading.
The nanocoating prevents the salt from becoming ‘sticky’ and enables them to maintain their original single crystal form. The salt crystals could enlarge after only 50 cycles if they were not coated, making them unfeasible for energy storage devices.
The industrial energy storage system is charged by heat or electricity. Regarding the specific mechanisms of SaltX batteries, the battery charges by heating the salt and storing energy. For discharge, these salts are reacted with water, releasing heat.
In the case of calcium oxide for the larger systems, the calcium oxide reacts with water during the discharge, releasing heat and creating calcium hydroxide. When the battery is charged, the calcium hydroxide absorbs the heat and decomposes back into calcium oxide and water vapor. The industrial systems used by SaltX utilize different tanks—one for storing charged salt and another for uncharged salt. This can be altered based on application requirements, hence it has been developed from the ground up to form a scalable system.
Why Release Heat?
After being charged with either heat or electricity, it can be released as heat up to 450 °C and heats water to produce steam.
The direct discharge of heat, rather than electricity, has many advantages and makes it a versatile energy storage medium for several applications. For example, heat/steam can be used to heat buildings (especially large-scale industrial buildings), but it could also be passed through a steam-turbine generator to produce electricity. The heat can also be used in district heating and cooling applications.
One of the appealing aspects of the batteries beyond scale and energy density, particularly if they are used on a wide scale, is that they can be charged easily from renewable energy sources, making them a very sustainable and green solution. Power from wind turbines and photovoltaic cells can all be used, as well as any steam generated from existing heating sources (such as industrial heating) and concentrated solar power, making the energy storage process much more circular and environmentally friendly.
SaltX technology has produced impressive small to mid-scale nanocoated salt batteries with high energy densities. However, the technology's ability to be scaled-up using Sumitomo’s fluid bed reactor could see the high energy densities being realized on a much larger scale.
By using existing technologies, the scalability is much more feasible than a completely new approach so there is a lot of potential for large-scale energy storage. This is important because as our energy demands get greater, we are going to need better (and more sustainable) ways of storing and using it.
Video Credit: SaltX Technology/YouTube.com
References and Further Reading
Business Wire [Online] Sumitomo SHI FW fluidized bed technology – upscaling thermochemical energy storage to a commercial level. Available at: https://www.businesswire.com/news/home/20201201005933/en/Sumitomo-SHI-FW-fluidized-bed-technology-%E2%80%93-upscaling-thermochemical-energy-storage-to-a-commercial-level
SaltX Technology [Online] Available at: https://saltxtechnology.com/
SaltX Technology. [Online] Technology. Available at: https://saltxtechnology.com/technology/
SaltX Technology. [Online] Energy Storage. Available at: https://saltxtechnology.com/energy-storage/
Sumitomo [Online] Sumitomo SHI FW fluidized bed technology – a solution to upscale thermochemical energy storage to a commercial level. Available at: https://www.shi-fw.com/2020/12/01/sumitomo-shi-fw-fluidized-bed-technology-a-solution-to-upscale-thermochemical-energy-storage-to-a-commercial-level/