The integration of intermittent renewable energy into electricity networks is one of the biggest challenges facing countries at present. While energy storage provides a fitting solution, conventional technologies for energy storage are bulky and expensive. Sweden-based SaltX Technology has developed a low-cost solution of storing energy in salt. The nano-coated salt technology is a cyclical thermal energy storage solution that helps remove the intermittency of produced renewable energy so as to meet peak demand. Following small-scale test systems in Sweden, SaltX has now installed a large-scale storage test facility at the Reuter cogeneration plant in Berlin in partnership with Vattenfall. A Renewable Watch team recently attended the opening of SaltX’s pilot project in Berlin, on the sidelines of Berlin Energy Transition Dialogue 2019.
The efficiency of battery-based energy storage systems with respect to space and cost constraints has often been debated. SaltX’s patented nano-coated salt scores high on this point: it has a very high energy density – over 400 kWh per tonne as compared to less than 100 kWh per tonne of flow batteries. It is also known to absorb over 10 times more energy than water. This makes the storage solution compact and thus ideal for integrating into existing power facilities. The heat in the patented salt technology is stored chemically with no losses. The nano-coated salt used by SaltX is calcium hydroxide [Ca(OH)2], which is extracted through environment-friendly processes. The nano-coating provides cyclability to salt molecules and enhances their life so that the same salt can be used for multiple cycles.
The nano-coated salt is heated with the help of electricity, which could be procured from renewable sources of energy during peak generation. This removes the water component, leaving behind calcium oxide. The chemical reaction is reversed when discharging the salt, resulting in excessive amounts of energy being released. At this point, both heat at requisite temperatures as well as steam for industrial processes can be released. For power generation, the steam thus generated could be used for turbine operations akin to conventional power plants. This circular sustainable solution has four primary components, two storage tanks and two reactors. The uncharged and charged salts are stored in respective tanks. One reactor is used for charging while the other is used for uncharging the salt. The reactors can be custom fitted, giving the system the capacity to charge and uncharge the salt according to the power required. Moreover, the storage tanks do not need to be pressurised.
The pilot project at Vattenfall’s Reuter cogeneration plant, Berlin, uses 20 tonnes of salt stored in the tanks. It will feed energy into the Berlin district heating network. One of the objectives of the project is to verify the theoretical process at the district heating level. According to SaltX, the nano-coated salt storage technology can be scaled up for grid-scale and industrial solutions. Since the process does not require advanced, expensive equipment, it can easily be integrated with existing technologies, as demonstrated at the cogeneration plant. Also, with economies of scale, the cost of setting up such a plant would be less than the systems based on other available technologies. Besides the supply end of the spectrum, SaltX’s technology works on the demand-management side, especially for industrial processes. The heat and steam that traditionally come from power-to-heat plants can be provided by modular or captive salt storage solutions for heat-intensive industries. It can be used in conjunction with renewables-based microgrids to provide steady power and heat supply to industrial infrastructure.
What SaltX is trying to achieve could well be the game changer for the renewable energy industry. Grid integration of intermittent renewable power has been a pain point for countries such as Germany, Australia, China and India, resulting in restrictive expansion of the renewable energy technology. With low-cost nano-coated salt technology playing the balancing act for renewables, grid integration might no longer be a challenge, allowing countries to execute their renewable energy expansion plans and assisting them in their pursuit of no-coal power. The technology is still at a pilot stage; therefore, cost economics are not available. Once results of the pilot project are analysed, its scalability, cost competitiveness and process viability as well as challenges and other critical parameters will be determined. For now, SaltX’s nano-coated salt-based energy storage technology might just be the hope for scaling up renewable energy across the globe.