Will the home energy storage system from Chojnice revolutionize our thinking about energy self-sufficiency?

With the systematic transition to renewable sources, we begin to think about energy in a different way than before. However, simply giving up energy from fossil fuels and using wind or solar does not solve the problem. More and more often in the discussion there are notions that become crucial for the construction of new, self-sufficient energy systems: energy saving and energy storage. While energy saving itself does not require much justification, its storage - both industrially and at the level of individual houses or other infrastructure elements - becomes as important as its production. The concept of "energy storage" is by no means new, and experiments and trials are underway around the world to improve and optimize them for various needs. Terraen, a small company from Chojnice in Poland, also participates in these works. A slightly different approach to the subject may make the completely self-sufficient and ecological storages proposed by Terraen to recover energy in the case of single-family houses and more.

A simple and effective idea

– Terraen is our associated company – says Krzysztof Kosiorek-Sobolewski, President of the Management Board of Zremb-Chojnice. He says that Terraen came from the experience of several people, and its first project has already been formally submitted to the Patent Office. Although the process is still ongoing, Kosiorek-Sobolewski estimates the chances of obtaining a patent at "close to 100 percent". And this is because no one has yet thought of such an energy storage solution.

The idea behind the Terraen's energy storage is simple. So simple that one of the scientists specializing in thermodynamics, with whom the project was consulted, cursed profusely in appreciation.

All over the world, experiments are underway with energy storage, the basic principle of which is to heat something when the production of energy is too much, and then take this heat away when the production is too little. Attempts go in different directions - both in terms of heated substances and the scale of the storages themselves. The working principle of the Terraen's energy storage is exactly the same. An innovation that no one has come up with before, however, is the use of surplus energy to heat its walls, which allows to reduce heat loss.

However, the concept of "energy storage" is very capacious and can mean very different solutions. Terraen - as the name suggests - focuses on the ground. The storage is created by digging a sufficiently large hole in the ground and digging the walls and floor of the storage into it. The resulting and secured hole is then backfilled with the same soil that was dug. This soil, separated from the surroundings by walls and a bottom, is then heated for a period of time when there is enough energy from a renewable source. However, there are a few details about this design that make it unique.

Prototypes and conclusions

The first prototype Terraen's energy storage was built near Chojnice, near the forest. It was constructed on the basis of theoretical calculations and met the expectations. The next two prototypes were less provisional. They were used to draw further conclusions and make further corrections.

– After these experiences, we came to another storage, which is located in Zremb-Chojnice company – says Krzysztof Kosiorek-Sobolewski. – We started heating it at the beginning of this heating year, it is now about 60% full. We put it in front of the paint shop and it will give off heat to it. We're still learning from it.

Another storage is being built next to a single-family house under construction. The last two are now the focus of the developers' attention, because they will give the most answers. Based on them, Krzysztof Kosiorek-Sobolewski describes in detail how they work.

– It is not difficult to dig a pit, make some insulation, lay glycol lines and heat the ground. The trick is to skilfully manage the accumulated heat and optimize the losses of the stored heat – he points out. This is what became the starting point for Terraen.

The warmth is in the details

As we already know, everything starts with digging a hole. In it, the internal walls of the warehouse are placed modularly, in which there are pipes with a heat-transfer substance. They are insulated with energy coming from a solar collector, in this way the ground in the warehouse is heated. The warmer it is, the more energy has been stored in it. But the challenge is to maintain a high temperature of the earth battery constructed in this way. This is helped by the outer walls of the storage, insulating from the unheated earth, which - unlike the projects of other companies from around the world - are also equipped with pipes with a heat-transfer substance and are heated through them. The difference is that heating the external walls, which will inevitably cool down faster due to contact with the cold soil, uses energy that would otherwise simply be wasted.

– The heating of this warehouse starts around April. The ground, which is directly below the surface, then has a temperature of 6-7 degrees. The liquid heated by the solar collector circulates and heats the storage. By August, with the appropriate size of the solar collector, we will heat the storage to 90 degrees – describes Krzysztof Kosiorek-Sobolewski.

Calculations show that in the meantime, in the case of a single-family house, so much energy is generated that it can not only be stored, but also heat water.

– Since April, we do not have to heat ourselves, and even if we had to, we can also direct some energy directly to the heating system. There is one condition – the building must have underfloor heating or another low-temperature heating system. They are the most effective in using such energy – explains the president of Zremb.

So let's go further in the timeline. During spring and summer, energy production is large enough to fill the storage and for the basic needs of a single-family house. When the cold weather comes in autumn, the warehouse begins to release the accumulated energy. With relatively low water consumption in the house, the 150 cubic meter Terraen stprage should, according to estimates, be able to supply energy for a 150 square meter energy-efficient house for the entire winter period.

This is where the previously mentioned heating of the outer walls of the warehouse comes in handy with energy that would otherwise be wasted. Where does it come from?

–If the warehouse has a temperature of, for example, 60 degrees, and in the afternoon the sun does not shine so much and we have a temperature of 40-50 degrees in the solar collectors, if we let it directly into the warehouse, it would cool it down. That's why we put 40-50 degrees on the outer walls of the warehouse – explains Kosiorek-Sobolewski.

Such optimization enables better use of the solar collector's capabilities and more effective maintenance of the temperature in the storage, and thus more efficient energy storage.

Verification ahead

Krzysztof Kosiorek-Sobolewski realizes that calculations are one thing, and reality is another. That is why several storage prototypes have already been built, but soon the first house with an energy storage that will provide valuable data will also be built.

– This year, a model house will be built, where someone who will draw energy from the storage for heating utility water and the building itself will live – explains the president of Zremb. He adds that ultimately all the basic data from this experiment on a living organism will be available in real time on the Terraen website.

The reality may turn out to be different from the calculations, but it is more likely that it will turn out positive. Terraen already has such experience.

– In the initial assumptions, we assumed that from November to the end of February we would not get any gigajoule of energy from the sun. But last year surprised us in a very positive way. It showed that collectors catch some energy even on cloudy days. With this extra heat, we protect the warehouse by heating the walls and direct contact surfaces to reduce the temperature difference between the ground and the warehouse – says our interlocutor.

For houses, greenhouses and Arabs

The Terraen solution was designed with the needs of single-family houses or greenhouses in mind. Krzysztof Kosiorek-Sobolewski says that there will still be time for commercialization, because the creators want to experiment a bit more and refine the solution. The factor that currently affects the functioning of energy storage is, for example, the soil in which it is placed. Clay works best. Sparse soil have much worse properties. But also here the creators of the magazine have room to show off.

– We still have to experiment a bit with different types of soil. We want to thicken it and pour in some water. Water is a great material for this type of experiments, we would like to build a few more different test warehouses to finally come to an optimal design. It'll probably take us a year or two. Then we can think about commercialization – says Kosiorek-Sobolewski.

And people interested in the solution are already talking. However, they have their own, different needs. Potential customers from the United Arab Emirates said that they liked the system very much, but due to different climatic conditions, they needed it to operate at different intervals – it has to accumulate energy during the day and release it at night. One of the representatives of Terraen will also go to Iraq to hold talks on how the energy storage could work. It is possible that the project will also find application in industry.

– A company that deals with production and has surplus energy that it wants to accumulate in order to reuse it reached us. In the production process, the company has to heat the material to about 130 degrees and then cool it down again. This energy goes into the air, and you can think about storing it and reusing it. We will try to offer them a solution – says the president.

Will the Terraen solution find its place on the market and help in the efficient use of energy? Krzysztof Kosiorek-Sobolewski does not want to throw himself at the sun. He talks about the need to refine the product, make a few more prototypes and check various possibilities, but at the same time he sees the potential for the use of storages for both private and industrial use. Time will tell which way this idea will develop and what form it will ultimately take. However, one thing is certain – moving away from energy produced from fossil fuels, we must pay close attention to its storage and optimal management of its use. Terraen can be an important step to give homeowners this opportunity.