Sand battery is a revolutionary advancement in the field of energy storage that not only solves the problems of solar and wind energy storage but is also ushering in a new era in the energy sector. According to modern scientific research, sand battery is actually an advanced Thermal Energy Storage (TES) system that uses desert sand or other silica-based materials as a medium for energy storage. This system is so effective that it can store energy at temperatures of 500-600°C for weeks and even months, while conventional batteries can only store energy for hours or at most a few days. The basic scientific reality of sand battery is based on the physical properties of heat. When sand is heated to high temperatures, it stores a large amount of heat within itself. This heat is then slowly released when needed, which can be used to heat water or generate electricity through Stirling engines. This capability of sand battery can not only revolutionize the use of renewable energy but can completely change our thinking in the energy sector. In recent years, Finland’s company Polar Night Energy has made remarkable progress in this field. They introduced the first commercial sand battery in 2022 and by 2025, activated the world’s largest sand battery in Pornainen, Finland, with a capacity of 100 MWh. This project has reduced district heating network emissions by up to 70%, equivalent to 160 tons of carbon dioxide annually. The importance of sand battery lies in the fact that it solves the problem of seasonal energy storage. Excess solar energy obtained in summer can be stored for winter, when solar energy availability is low. This capability can play an important role in increasing the use of renewable energy.

The physical foundations of sand battery are based on ancient principles of thermal energy storage, but modern engineering has taken it to a new level. According to physical principles, when sand particles are heated, they store heat very efficiently within themselves. This property of sand is related to the structural mechanics of its particles and the space between them. To understand the physical principles of sand battery, we first need to understand the basic methods of heat transfer: conduction, convection, and radiation. In sand battery, all three methods play important roles. Through conduction, heat transfers between sand particles; through convection, hot air circulates in the sand pile; and through radiation, heat is emitted in the form of infrared waves. The structural properties of sand particles play a key role in heat storage. Each particle acts as a small heat reservoir. When sand is heated, each particle absorbs heat and increases its temperature. The size, shape, and density of sand particles affect their heat storage capacity. Modern research shows that each sand particle’s ability to store heat depends on its volume, density, and molecular structure. Silica sand (SiO2) has the best heat storage properties due to its crystalline structure.

The history of sand battery invention has evolved rapidly in recent years, but its basic concepts are several decades old. During the 1970s energy crisis, initial research began on thermal energy storage systems. However, the technology of that time was insufficient to make it commercially viable. Finland’s company Polar Night Energy achieved the first practical success in this field, introducing the first commercial sand battery in 2022. This was the first time the concept of sand battery moved from the laboratory to the practical world. Since then, this technology has developed rapidly and by 2025, the world’s largest sand battery was activated in Pornainen, Finland, with a capacity of 100 MWh. Polar Night Energy was founded in 2018 by Markku Ylönen and Tommi Eronen. They began research on the concept of sand battery during their work at VTT Technical Research Centre of Finland. In initial experiments, they found that sand could prove to be an extremely effective source of heat storage. In 2020, they built their first pilot plant in Kankaanpää. This pilot plant had a capacity of 8 MWh and proved that the concept of sand battery could work practically.

The working mechanism of sand battery is amazingly simple, but its utility is very high. Its basic design consists of a large insulated silo filled with sand or other silica materials. This silo contains a system of heat exchangers that perform heat transfer. When the sun is shining or the wind is blowing strongly, the extra electricity obtained from it is converted into heat through resistive heating. This heat is then transferred to the sand pile through hot air, which stores temperatures up to 500-600°C. The resistive heating system converts electric currents into heat energy, the same principle used in electric heaters. The design of heat exchangers for heat transfer is extremely important. These heat exchangers usually consist of steel pipes installed in a grid pattern in the sand pile. When hot air passes through these pipes, heat is transferred to the sand through the pipe. The size, material, and layout of pipes affect the efficiency of heat transfer.

The scientific properties of materials used in sand battery are the foundation of this technology’s success. From ordinary construction sand to materials like crushed soapstone and high-purity silica sand are suitable for this purpose. The most important characteristic of these materials is their high thermal capacity, which enables them to store large amounts of heat. Thermal capacity means how much heat a material can store within itself, measured by the scale of specific heat capacity. The specific heat capacity of silica sand is approximately 830 J/kg·K, which makes it suitable for heat storage. Additionally, these materials can withstand temperatures above 1000°C without any chemical changes. This stability makes them ideal for long-term energy storage. Materials like crushed soapstone have even better thermal retention properties, further improving sand battery efficiency.

The economic and environmental importance of sand battery makes it unique among current energy storage systems. Economically, the construction and maintenance costs of sand battery are significantly lower compared to lithium-ion batteries. The main reason for this is that the materials used in it are cheap and available in abundance. Moreover, the lifespan of sand battery is much longer than traditional batteries, which makes it suitable for long-term investment. The cost of sand battery is usually between $50-100 per kilowatt-hour, while the cost of lithium-ion batteries is between $200-300 per kilowatt-hour. The operation and maintenance costs of sand battery are also low, as it has no moving parts and requires minimum maintenance. Environmentally, sand battery significantly reduces carbon dioxide emissions. The sand battery installed in Pornainen reduced district heating network emissions by up to 70%, equivalent to 160 tons of carbon dioxide annually. This figure clarifies the environmental importance of this technology.

The stages of sand battery installation and practical application involve several important steps. First, a suitable location is selected where renewable energy sources are available in abundance. Then, an insulated storage tank is constructed that will store sand or other materials. After that, the heating and heat exchange system is installed. The sand battery built in Pornainen is 13 meters high and 15 meters wide, filled with 2,000 tons of crushed soapstone. After that, it is connected to the existing district heating network. After these stages are completed, the sand battery starts its work. Site preparation is the first step in the installation stages. This includes leveling the ground, constructing the foundation, and providing necessary utilities. After that, the construction of the storage tank begins.

The performance and capacity metrics of sand battery distinguish it from other energy storage systems. Modern sand batteries can achieve more than 95% thermal efficiency, making them an extremely effective source of energy storage. The system installed in Pornainen can store 100 MWh of thermal energy, which is sufficient to meet an entire area’s heating needs for one month during summer months. In winter, it can meet heating needs for up to one week. This capability makes this technology ideal for seasonal energy storage. The performance of sand battery is measured by different scales. Thermal efficiency is the most important scale, which tells how effectively the system can store and retrieve heat. Round-trip efficiency is another important scale, which tells how much of the energy input into the system can be recovered.

Several sand battery projects are active worldwide that are proving the practical success of this technology. In Finland, two major projects by Polar Night Energy are operating – one in Kankaanpää and the other in Pornainen. The Pornainen project is particularly important because it is the world’s largest sand battery. Additionally, NREL is engaged in research and development stages in the USA. All these projects are evidence that sand battery is not just a theoretical concept but a practical reality that is already working. The Kankaanpää project started in 2022 and has a capacity of 8 MWh. This project provides heat to a small district heating network. This project proved that the concept of sand battery can work practically.

Although sand battery is a promising technology, it faces several challenges. The biggest challenge is low energy density, which requires large storage volumes. Moreover, there is also the problem of efficiency in converting stored thermal energy into electricity. Potential solutions to these challenges include the use of advanced materials, application of better insulation techniques, and use of hybrid systems. For example, NREL is researching high-purity silica sand that can not only store energy but can also be purified through calcining. The search for materials with higher thermal capacity continues to solve the challenge of low energy density.

The possibilities for future research and development of sand battery are extremely vast. Polar Night Energy is starting a pilot project in Valkeakoski aimed at converting stored thermal energy into electricity. Additionally, research continues on high-temperature thermal storage for industrial applications. NREL’s dual-use system, where silica sand is purified along with energy storage, is another important development. All these efforts reflect that sand battery technology is continuously evolving. Important areas of future research include the development of advanced materials.

The global impacts and international cooperation opportunities make this technology important at the global level. After success in Finland, Polar Night Energy is negotiating with international partners. Additionally, cooperation between companies like New York Power Authority and Homerun Resources with NREL is an example of global cooperation. This cooperation will not only accelerate technology development but will also help spread it globally. The global impacts of sand battery include improvement in energy security. This technology can help countries deal with energy crises. Moreover, it can reduce carbon emissions, which can play an important role in the fight against climate change.

Sand battery is deeply related to the achievement of global sustainable development goals. This technology directly helps in achieving affordable and clean energy (goal 7). Moreover, it promotes industry, innovation and infrastructure (goal 9). Additionally, it presents an effective solution for climate action (goal 13). All these aspects make sand battery an important source of sustainable development. In achieving goal 7, sand battery can provide affordable and clean energy by increasing the use of renewable energy. Moreover, it can improve energy availability, especially in remote areas.

The social and economic benefits of sand battery make it a valuable asset for societies. Socially, it improves energy availability, especially in remote areas. Economically, it reduces energy costs and creates new employment opportunities. In Pornainen, the sand battery not only reduced emissions but also improved energy security. These benefits clarify the social and economic importance of this technology. Social benefits include energy equality. Sand battery can equalize access to energy by increasing the use of renewable energy. Moreover, it can improve health standards, as it reduces the use of fossil fuels.

The future of sand battery is bright and its role in human development can be extremely important. As this technology develops, it will increase the use of renewable energy, reduce carbon emissions, and improve energy security. This is a suitable solution not only for developed countries but also for developing countries. In the future, we can observe further improved performance, lower cost, and wider application of sand battery, which can make it an important pillar of the energy sector. Potential future trends in sand battery include increased scalability. Future systems could be much larger than current systems. Moreover, integration could increase, where sand battery will work together with other energy systems.