Prototype- and Demonstration Projects
The Sand Battery Technology is being developed by the company Grounded Heat. The work is currently in a development phase where we step by step test, improve, and verify the technology through practical projects and prototype installations.
The projects presented here are part of this ongoing development. Through pilot installations and collaborations with various partners, we gather experience in construction, operation, and system integration. These projects provide valuable knowledge that helps make the technology more robust, efficient, and scalable.
In the near future, we plan to offer support in the construction of sand batteries as well as the supply of selected components and parts. We will target homeowners, housing companies, municipalities, farmers, and industries that want to develop the possibilities of thermal energy storage.
The first prototype of the Sand Battery was built in Hässelby in Stockholm as part of the development project Microgrid with Sand Battery. The project received funding from the Swedish Energy Agency and gave us the opportunity to design and test the first working version of the technology in practical operation.
The prototype was developed to investigate how sand can be used as a medium for thermal energy storage and how such a heat storage system can be integrated into a local energy system. Through testing and measurements, we were able to collect valuable data on temperature distribution, heat transfer, and operating strategies.
We later received additional funding from the Swedish Energy Agency in the project High-Temperature Heat Pumps for Thermobatteries. This project made it possible to continue the development work and deepen our understanding of how sand batteries can interact with other energy systems.
Since the first prototype was built, the technology has been improved in many ways. The experiences from Hässelby have formed the basis for further development of design, material selection, sensors, control systems, and system integration in later prototypes.
Through tests in our first prototype, we continuously collect data on temperatures, energy flows, and operating conditions in the sand battery. The measurements are carried out using a network of sensors that monitor how heat is stored, distributed, and released over time.
The collected data is used to analyze the system’s efficiency and compare real-world operation with our calculation models. The results provide valuable knowledge that makes it possible to adjust the design, control systems, and material choices in future versions.
In this way, we can step by step verify the performance of the sand battery and continue developing the technology toward higher efficiency and operational reliability.
The first Sand Battery Prototype has primarily served as a platform for learning and technical development. Through practical tests in real operating conditions, we have been able to gather valuable knowledge about how the system works and how different components interact.
During the course of the work, several parts of the installation have been rebuilt, adjusted, and replaced. Heaters, fan systems, electronics, and control systems have been updated in several stages in order to test new solutions and improve performance and operational reliability.
The prototype has also been started and stopped countless times during the development work. This means that operation has not always been continuous and that data collection has therefore varied over time.
This iterative development process has been an important part of gaining a deeper understanding of the technology. The experience from the prototype has laid the foundation for the improvements that are now being implemented in the next generation of sand batteries.
The first sand battery prototype has been more than just a test object. It has served as a platform for innovation and experimentation. By testing different components and operating configurations, we have been able to identify both the strengths and limitations of the system.
The prototype contains approximately 15 cubic meters of sand and is designed to supply heat for a typical single-family home. It has allowed us to test new materials, adjust the fan and heating systems, and develop electronics and control logic under real operating conditions. Through repeated start-up and shutdown cycles, we have been able to collect data under many different scenarios, creating a broad understanding of the system’s behavior over time.
The insights from the prototype are now being used to optimize the design, improve energy efficiency, and increase operational reliability in future sand batteries. The first prototype therefore serves as a key resource for all continued technology development.
The work with the first Sand Battery Prototype in Hässelby has provided us with important insights into how thermal energy storage systems function in practice. Through repeated testing and reconstruction of components such as heaters, fan systems, and control systems, we have gradually improved both the design and the operation.
The data collected during the tests has been crucial for developing the next generation of sand batteries with higher performance and better operational reliability.
The prototype has also given us a deeper understanding of how temperatures are distributed within the storage medium and how different operating strategies affect the system’s performance. These experiences have been of great importance for the design of later prototypes and for the continued development of the technology.
Following the experience gained from the first Sand Battery Prototype in Hässelby, development is now taking the next step in Eskilstuna. Here we are building our second prototype, where several of the lessons learned and improvements identified in earlier tests are implemented in a new and more advanced design.
The project is funded by the Municipality of Eskilstuna and represents an important step in the effort to develop and demonstrate sand battery technology in practice. Construction of the facility began during the winter of 2025/2026.
In the Eskilstuna project, we are testing improved material choices, expanded sensor capacity for measuring temperature and moisture, as well as new solutions for heat transfer and system control. The installation functions both as a testing environment and a demonstration platform where we can collect data, evaluate operation, and continue developing the technology for future installations.
By building and operating a larger and more highly instrumented prototype, we gain the opportunity to study how the system behaves under different operating conditions and over longer periods of time. The knowledge gathered in Eskilstuna will form the basis for further technical development and future sand batteries in both small and large energy systems.
In our work with Prototype 2 in Eskilstuna, we are testing several new design solutions based on the experiences from Prototype 1. Through improved material choices, upgraded support structures, and optimized placement of sensors, we are creating a more robust and efficient Sand Battery.
These changes provide more stable operation, better temperature control, and safer handling of insulation layers and heating pipes, and they represent important steps toward future installations in both residential and larger buildings.
The second Sand Battery Prototype in Eskilstuna serves as the next step in development and continues to be a central platform for learning and technical advancement. Through practical tests in real operating conditions, we can collect detailed data on how the larger and more advanced system functions and how the new components interact.
The building to be heated with the sand battery has an oversized solar panel installation. Surplus electricity from the summer will be stored in the sand battery and used for heating during the winter, demonstrating how energy storage can contribute to a more flexible and sustainable energy system.
In this prototype, we have increased sensor density and improved the construction with new materials and more robust support structures. Data from temperature and moisture measurements, both inside and around the energy storage, provide a detailed understanding of how heat moves and how the system responds over time.
The iterative design process is crucial for developing a robust and efficient solution. The experiences from Prototype 2 build on the knowledge gained from Prototype 1 and lay the foundation for future generations of Sand Batteries.
The second Sand Battery Prototype in Eskilstuna represents a significant step forward in the development of the technology. With approximately 50 cubic meters of sand, it is designed to heat a larger building equipped with an oversized solar panel installation, where surplus electricity from the summer is stored for use during the winter.
The prototype functions as a testing environment for new materials, improved constructions, and increased sensor density. The sensors measure temperature and moisture both inside and around the energy storage, providing a detailed understanding of how heat spreads and how the system responds over time. Pipe systems, fans, electronics, and controls are tested in practice to ensure stable and efficient operation.
All data and experiences from the prototype are used to further develop sand battery technology, improve energy efficiency, and increase operational reliability for future installations. The demonstration facility in Eskilstuna is therefore a central platform for translating theoretical knowledge into practical, scalable energy storage.
The second Sand Battery Prototype in Eskilstuna provides unique opportunities to test the technology at a larger scale and under more realistic conditions. With approximately 50 cubic meters of sand, the building’s surplus electricity from solar panels can be stored and used during the winter months, generating valuable practical experience in energy storage.
In this prototype, we are testing new materials, advanced sensor technology, and improved system solutions for pipes, fans, and control systems. The sensors provide detailed information on temperature and moisture both inside and around the thermal storage, helping us understand how energy moves and how the system responds over time.
These insights are being used to develop more robust, efficient, and long-term sustainable sand batteries. Prototype 2 is therefore an important step towards scalable energy storage solutions for homes, businesses, and public buildings.
Following the experiences from Prototype 1 in Hässelby and Prototype 2 in Eskilstuna, the development of sand battery technology now takes the next step at the demonstration farm Lilla Böslid in Halland. Here, we plan to build our third prototype, where lessons learned and improvements from previous projects will be applied in an even more advanced design.
The project is carried out in collaboration with Hushållningssällskapet Halland and is part of our initiative to demonstrate the technology in practical environments. Construction work is scheduled to begin in September 2026.
In this project, we will test new material choices and develop new techniques for grain drying and greenhouse heating. We also plan to investigate improved solutions for advanced system control. The prototype will serve both as a testing environment and a demonstration platform, where we can collect data, evaluate operation, and continue to develop sand battery technology for future installations.
By building and monitoring the prototype in Halland, we will have the opportunity to study the system’s behavior under real operating conditions and over extended periods. The knowledge gained here will form the basis for continued technical development and future sand batteries for both small and large energy systems.
FERL is a development project led by Hushållningssällskapet in Halland that explores how energy can be stored and used more efficiently at the farm level, with a focus on solar energy. Solar panels do not always generate electricity at the same time that the farm’s operations need it. Therefore, energy storage is a crucial piece of the puzzle.
Agriculture has great potential to produce renewable energy, but to use it more efficiently, some form of energy storage is required. By combining on-site energy production with storage, farms can become more self-sufficient, achieve a more stable energy supply in both everyday operations and crisis situations, and thereby increase overall farm resilience.
The third Sand Battery Prototype, to be built at the Lilla Böslid farm in Halland, takes the development of Sand Battery Technology to the next level. The facility will serve both as a demonstration platform and a testing environment, allowing us to evaluate improved designs, material choices, and system solutions under real operating conditions.
The Sand Battery will be designed to provide heating for greenhouses and grain drying, demonstrating how the technology can be integrated into a dynamic farm environment and contribute to both food production and energy efficiency. Sensors will be placed within and around the thermal storage to collect data on temperature and moisture, providing a detailed picture of heat distribution and system behavior over time.
The project is funded with support from the European Regional Development Fund, making it an example of how cross-border initiatives can promote sustainable energy technologies and practical knowledge sharing. Through this iterative development process, we can continue to optimize the design, operational reliability, and performance of sand batteries while generating valuable experience for future installations at the farm level and in other applications.
Construction of the facility at Lilla Böslid is scheduled to begin in September 2026, and the project will serve as an important platform for both technical development and practical demonstration of sand battery technology.
Continue generating and storing solar electricity during power outages and keep critical equipment running, even without the grid.
Keep heating your home during blackouts and increase your resilience in disaster situations.
Reduce electricity grid charges by monitoring power usage in real time and dynamically shaving peak loads using stored energy and load management.
Reduce electricity grid costs by automatically shifting energy consumption in the building to periods outside tariff intervals, without compromising comfort.
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