Follow the development of the sand battery

Here, we gather information and images detailing the progress of our work with the sand battery. Feel free to reach out if you would like to learn more!

Ceramic insulation materials

10 juni 2024

Ceramic insulation materials are exceptional in their ability to withstand extremely high temperatures, over 2000 degrees Celsius.

The purpose of using these materials is to minimise heat loss and thereby increase energy efficiency.

Additionally, ceramic insulation materials protect the fan motor and surrounding components such as mounts, extending their lifespan and improving operational reliability in high-temperature environments.

Photo: Susanne Kindblad

A sand battery is hardware, but this hardware needs surprising amounts of software

June 4th 2024

This software needs to ensure that the sand battery is efficiently operated and enable the owner to monitor and control its operation.

One of the first aspects we have had to solve is how to control the temperature in the sand battery radiator array when we have determined that it’s a good time to start heating the sand. We generally want to put heat down in the sand as quickly as possibly, which means we want the air to be as hot as possible. However, if the air becomes too hot we may damage or destroy components.

Granted application from the Swedish Energy Agency

May 30th 2024

We have been informed that our application for funding from the Swedish Energy Agency has been granted. This means that we will work with experiments using high temperature heat pump technology in the sand battery prototype.

It also means that we will be able to work more intensively with the further development of the sand battery during the project period 1 June - 30 September 2024

Many thanks to the Swedish Energy Agency!


April 27th 2024

Our team has successfully completed the metalwork preparations for the installation of the upgraded heating system for the sand battery.

The metalwork, which involved precision welding and steel processing, is a crucial step in ensuring the durability and efficiency of our energy storage system. With this step completed, we are one step closer to implementing a groundbreaking solution for heating indoor air and hot water in houses, townhouses, and public buildings.

Photo: Susanne Kindblad

Energy Conference in Eskilstuna 

April 12th 2024

Today, Pontus and Susanne had the great honor of participating as speakers at a conference on the topic of energy storage, organised by the Energy Evolution Center in Eskilstuna.

Our contribution to the conference was very well-received, and the questions from conference participants seemed endless. We hope that photos from our presentation will eventually appear on this link.

Photo: Susanne Kindblad

Preparations for upgraded heating system  

April 8th 2024

Preparations are underway here for a welding job where a piece of cast iron will be processed to manufacture a tool.

Here, Christoffer, Maria, and Marcus are involved in preparations for welding in cast iron to manufacture a new tool. The tool will be used to shape a sheet metal detail to be used in the improved heating system 2.0 of the sand battery.

Photo: Susanne Kindblad

Balancing of fan system 

April 2nd 2024

The fan system used to rotate the air in the sand battery undergoes an inspection aimed at reducing the vibrations that occur.

We have also upgraded to a more efficient fan motor.

Photo: Susanne Kindblad

New warning signs

March 23rd 2024

We have ordered warning signs for the shed where the sand battery's heating unit will be located, and today we received delivery.


Photo: Susanne Kindblad

Optimisation of the Sand Battrery heating unit

March 8th 2024

The testing and exploration of the possibilities of the sand battery heating unit continues. The purpose is to increase the heating rate in order to increase the performance of the sand battery.

Here, Pontus and Christoffer are preparing the heating unit for connecting a high-temperature heat pump.

Photo: Pontus Kindblad

The most beautiful shed in the world?

March 7th 2024

During the winter, the sand battery has been disconnected, waiting for sunshine and reasonable electricity prices. We have worked on other projects and interspersed this with further developing the optimisation of the heating system and constructing a fireproof shed where the heating system and fan system will be stored.

Now we can't wait to plug in and test the improved heating system!

Photo: Susanne Kindblad

Paus in heating up of the sand battery 

November 21st, 2023

We switch off the heating and let the sand battery go into hibernation. Since we do not yet have any self-produced electricity from solar panels connected to the sand battery and since it is hardly financially justifiable to buy electricity at this time of the year, we have chosen to disconnect the sand battery over the winter.

In the spring, our plan is to start installing solar panels so that we can recharge the sand battery during the summer. During the winter of 2024, the heat from the sand battery will heat indoor air and hot water in the house if everything goes as we have planned.

See you again in the spring of 2024!

Photo: Susanne Kindblad

Application for additional project funds

October 31st, 2023

The construction of a prototype for a sand battery project has been in progress since June 1st. Currently, our focus is on preparing a comprehensive report and submitting an application to the Swedish Energy Agency for ongoing project financing.

We aspire to secure the opportunity to further advance the project by constructing a full-scale microgrid installation. This installation will incorporate solar panels alongside a connected sand battery, complemented by traditional batteries for short-term electricity storage.

As we await feedback, we are actively continuing temperature measurements. This ongoing effort allows us to draw conclusions regarding the efficiency and storage capacity of the sand battery

Looking for investors

October 23rd, 2023

We have completed a market analysis for the business around sand batteries. The analysis shows good opportunities for business development around the innovation and we are now looking for one or more investors who want to help us with financial muscles to be able to market the sand battery as quickly as possible.

Are you an investor or do you know someone who you think might be interested in investing in our company? Contact us and we'll talk some more!

Commissioning of the heating system

October 21st, 2023

The heating system and fan system have been switched on and the heating of the sand battery is in full swing. We measure and document how quickly it is possible to heat up 24m³ of sand. Our goal is for the sand battery to reach a temperature of 600 - 650 °C.

Did you know that around 2/3 of a villa's energy consumption is used for heating and hot water? This electricity is normally consumed when the load on the public electricity grid is greatest, which means peak loads for electricity producers and higher electricity costs for consumers. Through the sand battery, electricity can be stored in the form of heat for a long time. The heat can then be used for heating houses and hot water, and in this way the public electricity grid is relieved while the cost for electricity consumers drops.


Photo: Susanne Kindblad

Bye bye, sand battery!

October 20th, 2023

Now the entire three meter deep pit is filled up. In the spring, we will plant grass seeds in the entire area where the sand battery is located and where the excavated masses have been.

We have a vision of building a greenhouse on top of the sand battery to take advantage of any waste heat that will seep up through the ground. Unfortunately, it does not fit within the framework of this project, but in the spring we hope that we will have time and money to build a greenhouse. Come and visit us and see how things are going!

är hela den tre meter djupa gropen igenfylld. Till våren kommer vi att plantera gräsfrön på hela området där sandbatteriet är placerat och där schaktmassorna har legat. 


Photo: Susanne Kindblad

Closure of the insulation

October 18th, 2023

We have got the insulation layer on the top of the sand battery in place and now the closure is underway so that the sand battery is kept watertight.

We use a heat-insulating foil called Alu-Pap to keep the heat inside the sand battery while keeping the moisture on the outside. The foil consists of a three-layer laminate consisting of paper, LDPE polyethylene and aluminium. The foil provides a re-reflection of heat while keeping moisture away from the sand battery. To get tight joints, we use aluminum tape generously.

Photo: Susanne Kindblad

The work with the sand is finished - the pipe system is buried

October 16th, 2023

The pipe system where the hot air will circulate is in place in the sand battery. A couple of tons of sand had to be removed from the pit and then put back. Our backs are tired but the satisfaction is great that the pipe system and the sand are in place.

The next step will be to insulate the top of the sand battery, first with ceramic fiber cloth, then with approximately 20 bags of perlite and finally everything must be sealed with a layer of the aluminum foil Alu-Pap to keep the moisture away. A layer of construction boards is placed on top to prevent gravel and stones from damaging the waterproof layer. Finally, we will cover the sand battery with gravel and soil.

Photo: Susanne Kindblad

Sensors for measuring temperature and humidity

October 13th, 2023

Sensors for measuring temperature and humidity have been placed in various spots in and around the sand battery. To know if the prototype works as well as our calculations show, we need to measure how fast the heating goes, how long the heat can be maintained, and the degree of penetration of moisture.

We measure not only inside the sand battery, but also in and just outside the various insulation layers. In this way, we can determine how much waste heat the sand battery emits.

If it turns out that the sand battery releases a lot of waste heat, we will come up with a solution for how this heat should be used in the best way. For example, a greenhouse can be placed on top of the sand battery and the waste heat can thus be used for winter cultivation.

Photo: Susanne Kindblad

Sketch up for web application

October 10th, 2023

We are currently working on the specification for the web application that will be built to overview the heat in the sand battery and to control the extraction of heat.

The work includes developing a list of requirements of the highest priority functions in the app and to ensure that we get the functions that are most in demand, we have put together a small focus group consisting of as many men as women.

The list of requirements will be the basis for the production of the app at a later stage.

The heating unit

October 9th, 2023

We put the finishing touches on the heating box, which after a lot of tests and improvements is now ready for connection to the sand battery.

The heating technology is based on inductance, but we choose not to reveal exactly how the heating technology is constructed. It may become the subject of a patent application in the future and then it is important that we have not revealed too much about the technology underlying the heating of the sand battery.

Now we are anxiously waiting to see if everything works as expected when we connect the heating box and fan system with the sand battery.

Photo: Susanne Kindblad

The pipe system is in place - soon we will connect the heating

October 6th, 2023

The pipe system where the hot air will circulate is in place in the sand battery. The pipe system needs to be buried a bit and we will work on that during the weekend.

Come by if you are keen to help! We have plenty of shovels and we treat everyone who helps us to coffee! 😜

Photo: Susanne Kindblad

Similar project in Jämtland

October 3rd, 2023

In Salsån in Jämtland, Katerina and Kenneth Nordin are building a huge silo to be filled with 60 tons of granite macadam. The idea seems to be the same as our sand battery, except that Kenneth and Katerina have chosen to build their battery above ground, just like the Finnish company Polar Night Energy.

See the news clip from SVT Jämtland at:

Construction of heating system

Oktober 2nd, 2023

The construction of the heating system and the fan system for the rotation of the hot air is going on in parallel with the work in the pit.

The work places high demands on heat resistance as the air to be rotated in the system will maintain a temperature of up to 800°C.

We have received some help to get started with welding work and construction of an extra heat-resistant fan.

Photo: Pontus Kindblad

Free work out session! 

September 29th, 2023

We are still working on the backfilling of soil and other excavated materials in the space outside the outer container of the sand battery.

Are you keen to help? We have plenty of shovels but unfortunately the budget for excavator hire ran out a long time ago...

Come and help us dig for a couple of hours and we'll treat you to coffee!

Photo: Susanne Kindblad

The Sand is in place!  

September 27th, 2023

With some assistance of an extra large crane truck, we finally got the sand in place in the sand battery. Out of a total of sixteen cubic meters of sand, twelve are now in place and we are now working on connecting the pipe system that will rotate air for heating the sand battery.

Sand weighs quite a lot so it was very helpful that we were able to get the second delivery via a crane truck that could place the sandbags directly into the pit. We continue to work with the refilling of slag masses in the space outside the sand battery itself.

If you want a free, meaningful and guaranteed sweaty workout, you're welcome to help us move chess pieces back more into the pit around the sand battery! We have plenty of shovels, so just show up at Sigfridsdalsvägen 11 in Hässelby

Photo: Susanne Kindblad

Ceramic insulation fabric

September 20th, 2023

The inner container in the sand battery is insulated with a ceramic insulating fabric that can withstand temperatures up to 1260°C.

We chose an environmentally approved insulation fabric where the fibers are biodegradable and therefore less harmful to health and our climate.

We consistently have high standards in our material choices in the sand battery. Our goal is not only to create a product that saves energy in the form of heat, but the end product should also contribute to a positive climate transition. We work for this by choosing the materials that are most gentle on the climate and by only benefiting producers who produce sustainable raw materials.

Photo: Susanne Kindblad

The containers for the sand battery in place in the pit

September 15th, 2023

With the help of the excavator, both containers for the sand battery have now been lifted into place.

The outer, larger container has been insulated with a heat-resistant and waterproof material. We then filled it with the insulation material Perlite. Once that was done, the smaller container was lifted into place.

The heat development was not to be trifled with when the sun was shining and Perlite is a material that dusts tremendously when the bags are opened and the contents are distributed in the container. The next step is to fill an inner container with sand and with the pipe system that has been designed to circulate hot air in the sand battery.

Photo: Marcus Nordgren


September 11th, 2023

Perlite is volcanic rock that expands greatly when heated. Therefore, it has one of the market's best insulation values, a low climate footprint and it can withstand exposure to very high temperatures.

We have chosen to insulate the sand battery with perlite because it has good climate properties, a low climate footprint and because it is a material that can withstand very high temperatures without the risk of ignition.

The outer container is filled with approximately 50 cm of perlite before the inner sand container is lifted into place. Next, the sides will be filled with perlite so that the inner container is surrounded by perlite.

Photo: Dan Widegren

Insulation with heat-insulating foil

September 5th, 2023

The outer container of the sand battery is covered with a heat insulating foil called Alu-Pap to retain the heat inside the sand battery while keeping the moisture on the outside of the sand battery.

The foil consists of a three-layer laminate consisting of paper, LDPE polyethylene and aluminium. The foil provides a re-reflection of heat while keeping moisture away from the sand battery. To get tight joints, we use aluminum tape generously.

Photo: Susanne Kindblad

Startup 4 Climate

August 30th, 2023

We participate in the Startup 4 Climate competition organized by, among others, Ellevio and GodEl. Startup 4 Climate is one of Europe's biggest innovation challenges aimed at young companies with ideas that can accelerate the energy transition.

We want to encourage everyone to visit their website and vote! Regardless of whether you vote for the sand battery or for one of the other contributions, you are doing a good deed. For each vote, Ellevio and GodEl donate five kronor to Doctors Without Borders.

The first container in place in the pit  

August 28th, 2023

With support from our hired excavator, after a lot of effort and trouble, we got the outer sand container in place in the pit. We had underestimated the labor involved in moving the containers and we were forced to unscrew the outer container and then reassemble it once it was in place in the pit.

Although we had hired a large excavator, the excavator arm was not enough to lift the outer, larger container down.

Now that the container is in place, it is reassembled and insulated with a water and heat insulating film.

Photo: Dan Widegren

The technology receives attention in the Washington Post 

August 24th, 2023

Natural batteries of sand, salt, heat, air and other elements are intended to make it possible to take advantage of the energy from wind turbines and solar panels when the sun does not shine and the wind does not blow, writes the Washington Post.

The price of renewables is significantly lower than the cost of fossil fuels, especially after a Russian fuel backlash has pushed prices across Europe to record highs. But the green energy revolution still faces a major obstacle: the lack of long-term, cost-effective renewable storage.

The Washington Post highlights the Finnish company Polar Night Energy, which has developed a sand battery in the form of a silo above ground.

Read the entire article for free at

Wind in the sails – construction of containers for insulation and sand   

August 17th, 2023

The sand and the insulating material will be placed in large containers to keep them apart and to avoid moisture in the sand battery. The containers will be placed in the pit and filled with sand and insulating material respectively.

We happened to choose really windy days for the construction of the containers. This means that the strength testing is ongoing and that we put a lot of hard work into protecting the containers from blowing apart before they are in place in the pit.

Photo: Susanne Kindblad

Test of sensors that collect data on temperature and humidity   

August 10th, 2023

Testing of the measurement sensors is ongoing to ensure that the data we collect is registered and stored correctly. Based on this data, we will be able to draw conclusions about the heating rate in the sand battery. We will also be able to measure the storage capacity and make adjustments to the processes for inputting and extracting heat in the sand battery.

In the clip, you see Marcus and Pontus measure and record the temperature of ice cream.

Photo: Pontus Kindblad

Insulation of the sand battery

August 8th, 2023

The heat in the sand battery must, to the greatest extent possible, stay inside the sand until it is time to extract the heat for heating indoor air and hot water. To make this possible, the battery needs to be properly insulated.

We have chosen the material Perlite as insulation material. Perlite is a volcanic material which after intense heating becomes white and porous, almost like crumbled styrofoam. Perlite can not only be used as an insulating material but also as a natural soil improver.

Perlite has been chosen as insulation material because it is gentle on the environment and very heat resistant.

Photo: Susanne Kindblad

Sensors for collecting data on temperature and humidity   

August 2nd, 2023

To measure how the heat is distributed in the sand battery, a number of sensors are placed in different places inside the construction. The sensors need to withstand extremely high temperatures so that we can collect measurement data throughout the project.

We will also place sensors that measure the moisture in the sand battery. Will we succeed in building a completely waterproof outer container?

Photo: Dan Widegren

The heat exchange system is beginning to take shape  

July 28th, 2023

In the heat exchange system, the hot air must circulate to heat the sand. The installation of the pipes itself has taken some time, but now the construction is starting to take shape. In the pilot project, we will measure how much energy is required to reach approximately 600 ºC, the time required to reach this goal and we will also measure how long we can store the heat in the sand battery.

Photo: Susanne Kindblad

In Linköping, a heating battery is being built in the bedrock  

July 23rd, 2023

A mountain in Linköping will act as a rechargeable battery to save heat for the winter. The technical works are now carrying out an attempt to make use of waste heat.

In a mountain, under a sheepfold, in Vallastaden in Linköping, heat must be saved for the winter. A short distance away is the waste incineration plant where garbage is burned and district heating is produced there. But during the summer, not all heat is used.

The excess heat heats up the groundwater that circulates in the rock. In this way, the mountain is charged with heat that can hopefully be stored for the winter. The mountain becomes like a thermal battery.

People show interest in the sand battery  

July 22nd, 2023

In the last week, no less than three people unknown to us have contacted us and shown interest in the project.

We are of course very happy when people get in touch, regardless of whether it concerns possible future collaborations, a desire to get involved in the project or just curiosity. We welcome all kinds of thoughts and ideas that can improve the construction of the sand battery.

Do you want to get involved in the project or do you want to know more? Contact us and we'll talk more!

Photo: Susanne Kindblad

Construction of the heat exchange system

July 18th, 2023

We build the parts of the heat exchange system that are placed in the sand battery itself from exhaust pipes. The hot air must circulate in the pipes to heat up the sand and to later extract heat from the sand battery.

Photo: Dan Widegren

Drone images of the pit where the sand battery will be placed  

July 12th, 2023

Thanks to our friend and colleague Martin Kemani, we have received a drone film showing the pit where the sand battery will be located.

Please enjoy!

Recycled material

July 7th, 2023

We try to use recycled materials as far as possible. When we build the scaffolding that will hold the sand battery's insulating layer, we use, for example, old planks that have seen their best days long ago.

The purpose of the sand battery is to combat global warming by storing heat in an environmentally friendly way. We are therefore careful to choose materials that have as little negative impact on the climate as possible. Therefore, it is a good idea to recycle old wood.

Photo: Melker Kindblad

Construction of measuring equipment

July 4th, 2023

In the sand battery prototype, we will collect lots of measurement data to ensure that the heat storage works as intended. We will also measure the temperature in the insulation layers as well as in the soil around the sand battery to determine how much waste heat is produced. Based on the data we collect, we will optimize the isolation of the sand battery.

Work is now underway to design the measuring equipment. Pontus programs microcontrollers and does tests with various sensors for humidity and heat.

Photo: Susanne Kindblad

The pit is ready - now we start building the sand battery!

June 16th, 2023

We buy in insulation material and construction material for the sand battery. Marcus and Susanne have been driving trucks and carrying construction boards and gravel in the heat today.

A lot of time has been spent evaluating different building and insulation materials. We now believe that we have fully planned the details of the construction of the sand battery itself and most of the material is in place. Now many sweaty hours remain so the construction itself will be carried out.

Photo: Susanne Kindblad


June 12th, 2023

Today we excavate the pit where the sand battery will be placed. Our extremely pleasant and competent excavator operator Thomas completed the work in one morning and now we are starting work on constructing the sand battery.

Photo: Susanne Kindblad

Patentability investigation

June 8th, 2023

We have carried out a patentability investigation in collaboration with a patent lawyer. The purpose of the investigation was to ensure that with our sand battery we do not infringe on any existing patent and to clarify whether there is anything in the technology we are developing that can or should be protected through a separate patent application.

Our patent attorney has clarified that we have so-called Freedom to Operate, which means that there are no currently valid patents that we could risk infringing.

He also advised us to reveal as little as possible to our potential competitors. However, we have chosen not to follow this advice, but instead to share our lessons learned and experience with you on this website.

Are you planning to build your own sand battery? Or do you have skills that could be of help to us? Get in touch and we'll talk more!

Project start

June 1st, 2023

The project is officially underway! We take in different quotes, compare materials and prices and order equipment. We study thermodynamics and different insulation materials while we discuss patent strategies with a patent consultant.

Soon we will start the actual construction of the prototype for the sand battery. Follow the work here at and contact us if you want to know more about the project!

Photo: Susanne Kindblad

Funding from the Swedish Energy Agency

May 5th, 2023

The Swedish Energy Agency (Energymyndigheten) has decided to grant support in the form of a grant to K-mit AB for the implementation of the project "Microgrid with sand battery" during the period 1 June 2023 - 31 October 2023.

The project revolves around constructing a prototype of a microgrid for 2 to 10 houses where solar panels and/or wind power generate electricity that is stored in two ways:

  • a common sand battery for storing energy in the form of heat
  • traditional batteries for short-term storage of electricity

Together, these storage methods mean that the houses are to a very large extent powered by self-produced energy. The heat in the sand battery can be saved for months to be used for heating the house and hot water.

Sand is a cheap raw material and the components used for heating and extracting heat are also cheap and gentle on the environment. As a result, our product has a positive climate impact while at the same time lowering heating costs for consumers. The strength of this innovation is that it is durable, cost-effective and that it can be installed in already existing houses.

Get involved in the project!