Despite significant advancements in renewable energy generation, we still face a challenge in finding a scalable and flexible method for its storage, particularly for solar and wind energy, which vary greatly depending on weather conditions and daylight hours. Renewable energy holds a central role in the decarbonization strategies of many countries, which aim to achieve net-zero carbon emissions by 2050. This will require tripling the reliance on clean energy sources to accomplish ambitious goals in reducing global warming and mitigating the adverse effects of climate change. Despite the proliferation of renewable energy technologies and their falling prices, a fundamental problem persists — ensuring their availability at all times of the day and throughout the year, including when the wind doesn't blow, the sun doesn't shine, or water levels in hydroelectric dams are low. Current storage of electricity generated from renewable sources primarily relies on massive chemical battery packs, predominantly made of the metal lithium. However, the rising prices of these batteries, their potential environmental impact over their lifecycle from manufacturing to disposal, and the complexities of recycling have spurred a number of forward-thinking companies to develop innovative alternative energy storage methods, moving beyond chemical storage containers and effectively using the stored energy to generate electricity when needed. 
Lithium batteries contain chemicals like manganese, cobalt, and nickel, which are harmful to the environment (Reuters) ## The Environmental Impact of Lithium Batteries Storing energy in lithium batteries offers a range of advantages that could aid in achieving sustainability goals, particularly in terms of energy efficiency. Lithium batteries can store energy from renewable sources like solar, wind, tidal and wave currents, biofuels, and hydropower for extended periods. However, the metals used in manufacturing these batteries, such as lithium, cobalt, and nickel, present new environmental challenges. The processes employed to extract these metals can be highly damaging to the environment and local communities, as mining and purifying battery materials require significant amounts of energy, leading to greenhouse gas emissions. Extraction activities also result in soil degradation, high water consumption, and biodiversity loss due to the clearing of vegetation and trees in mining areas, harming ecosystems. Additionally, lithium batteries contain harmful environmental chemicals like manganese, cobalt, and nickel. If not handled correctly, these substances can leak into water supply systems and cause contamination. Eventually, lithium batteries become electronic waste, often ending up in landfills, or they might be dismantled or burned unsafely to recover valuable small components, posing further risks to human health and the ecosystem. ## What are the Alternatives to Chemical Batteries? Thermal Energy Storage is a cost-effective alternative that stores energy as heat in liquid materials or solid masses like water, oils, or rocks. Currently being actively tested, one method involves storing the heat generated by renewable energy sources by heating up blocks of rocks, bricks, or volcanic ash during peak times to utilize during off-peak hours to operate heat pumps, which can then produce low-cost electricity. While the term "battery" often refers to the chemical type found in cars and electronics, systems that store heat in hot rocks currently store ten times the amount of energy stored in lithium-ion batteries worldwide. These systems were developed leveraging an old invention dating back to the 19th century known as the Cowper stove, massive towers of stacked bricks that absorb wasted heat from smelting and casting furnaces, heating up to approximately 1500 degrees Celsius. This heat is used to warm air streams pushed at high pressure through the bricks, heating the air to 1200 degrees Celsius and pumping the hot air into the bottom of a furnace for its thermal energy to melt raw iron. According to a report published in the journal ACS Omega, a team of scientists discovered that some samples of soapstone and granite in Tanzania are perfectly suited for storing solar heat, featuring high energy density and stability at high temperatures. Granite and soapstone are abundant worldwide, making them preferred materials for thermal energy storage. 
Using natural pebble stones to store thermal energy for intermittent power generation sources like solar and wind energy (Sandia National Laboratories) ## Successful Experiments Several companies are currently producing battery systems that utilize common rocks which can be directly integrated with renewable power generation systems such as wind and solar energy. For instance, in California, the Rondo thermal battery uses electric heating elements (like those in cooking ovens) to convert available clean energy into high heat. When the energy is available, electric heaters glow and thousands of tons of bricks are heated directly by this thermal radiation to temperatures up to 1500 degrees Celsius, storing the energy for hours or days with an extremely low loss rate (less than 1% per day). When it's time to generate power, air flows through the brick heap and is heated to over 1000 degrees Celsius, then the resulting hot air is used to boil liquids, turning them into steam that drives generator turbines to produce electricity. Through its pilot project in operation at a facility in California, "Antora Energy", backed by Bill Gates, plans to ship this technology to early customers by 2025. Antora's thermal battery system keeps electrical energy as heat inside an insulated box, packed with piles of graphite, the black material used in pencils, which upon heating turns electricity into heat. Graphite can then store that heat and release it steadily for up to 50 hours as a beam of heat and light through a window on the side of the container, using this warmth, for instance, to heat up cement-making kilns. Moreover, Sandia National Laboratories in the United States is collaborating with New Mexico-based CSolPower to research and develop using natural gravel as a medium for storing thermal energy for intermittent power sources such as solar and wind energy. Sandia designed a small-scale pilot project capable of 100 kilowatts per hour, which tested a rock bed by charging it with hot air above 500 degrees Celsius, maintaining this temperature for up to 20 hours. The system was successfully discharged, and Sandia reported that the system's performance aligned with modeling and predictions. The manufacturing company intends to make the product widely usable, but first, it will develop smaller versions, which can benefit from other heat storage projects in rock formations for numerous greenhouses in northern New Mexico. ## A Sand Battery and Another from Basalt In a remote town in southwestern Finland, "Polar Night Energy" tested the world's first "sand battery", a thermal energy storage facility capable of storing clean energy for several months at a time. The high-tech storage tank primarily uses cheap electricity from solar and wind energy to heat sand, which then stores heat at about 500 degrees Celsius. This heat can be used for warming local buildings during the winter months when energy is at its peak. A Dutch company also developed a basalt battery capable of storing large amounts of electricity generated by solar panels and wind turbines. Basalt, a very common type of volcanic rock, easily absorbs heat. The system operates by directing sustainably generated electricity through metal pipes, which heat the basalt inside a metal container insulated with a one-meter-thick rock wool layer. Thanks to this insulation, the heat can be stored for several months, even years, and used for heating homes. Additionally, all materials can be easily recycled.
61
previous post
