In the two previous episodes, we had the opportunity to talk about storing electrical energy in different forms: in episode 01, in chemical form using hydrogen, and in episode 02 in the form of kinetic energy using flywheels. Today, we are addressing the storage of energy in the form of heat. It seems to me that the subject is less visible than hydrogen or renewable energies these days. Nevertheless, without much research effort, we will find that the field does not lack quite diverse projects and experiments. One example is the Crescent Dunes Solar Thermal Power Plant project in Nevada, where the solar concentrator can heat molten salts up to 600°C. These salts are stored in a thermal-insulated tank to vaporize water that supplies an electric turbine, even after dark. Further experiments are being carried out to store energy in the form of latent heat or phase changes. These technologies often remain complex and immature.
That said, the most common and simple way to store heat is well known to everyone: water. Many of us use a tank water heater. The water is heated, often at night, and then we use it throughout the day. Some companies, such as HoCoSto in Holland, offer to store excess energy in large in-ground pools. The stored heat can be used later, during the cold seasons. Armand Menargues, the founder of WATINTOO, has taken the idea of geothermal energy and liquid energy storage a step further, as we will discover. He’s got plentiful ideas. Do not imagine that he is dispersing himself, he is very clear on the orientations of his project. Armand, could you introduce us to Watinyoo?
The basic idea is to store energy in water to regulate the needs of a building. On the other hand, as you well know if you have a cellar, the temperature in the ground is relatively constant. We can therefore use it to exchange heat between our water supply and the ground, or to evacuate or recover calories if necessary. In concrete terms, we install a water loop at a depth of 1.5m. It is a tube with a diameter of about 25cm. We use water-to-water or water-to-air heat pumps to exchange energy between the building and the water loop. Let’s take the example of an air conditioning need, we can store the excess energy in the water loop. And vice versa in case of heating. The objective of the WATINYOO system is to control the temperature of the loop so that it remains within an interesting range for the user’s needs.
What is the difference with a geothermal heat pump that uses an underground collection network to recover heat?
The idea is the same, but with WATINYOO, we look at the problem from all angles. It is therefore possible to combine several needs, connected together on the same loop. This makes it possible to exchange energy within the same building or between buildings.
Could you give us an example?
Of course, let’s take the case of a hotel: these establishments have very high domestic hot water needs. In general, they also have significant needs in air conditioning and heating. They can also have a Spa or an outdoor pool that needs to be heated. We can recover the heat produced by the air conditioning exchangers to inject these calories into the water loop. These calories can be used to heat the pool or domestic hot water. I can give you another example: a campsite that has a restaurant under a verandah and a swimming pool. They had to install air conditioners to cool their restaurant and a heating system for the pool, all of which represents a very significant operating cost. With our water loop, we could recover heat from the air conditioners to inject it into the pool and drastically reduce operating costs. In general, any system that allows heat exchange can be used with our system, such as under-roof water circulation or a greywater heat recovery system. (Note: Grey water is hot water from drainage, for example hot water used for showers).
However, space is required to install the water loop. Is your solution really ideal for a single-family home?
There is a threshold effect. The investment is probably too high for a single-family home. It is more interesting to consider a building as a hotel or hospital or a subdivision of several houses. The configuration of the ground is essential for the installation of the loop, which requires free space. We can add geothermal baskets to the water loop. These are coils in which water circulates and which exchange calories with the ground. These baskets are buried at a depth of 4 or 5m. A one metre diameter borehole is required to install them. The addition of baskets to the water loop makes it possible to multiply the exchange zones and thus, possibly, to reduce the size of the loop. The geothermal baskets are controlled by small valves that are controlled by the system.
To optimize the system’s operation, you have developed a control command system called WATeBOX. What are the technologies embedded in the WATeBOX?
The WATeBOX allows you to control the system and regulate the flow in the water loop. This is an IoT sensor set for each element exchanging with the loop (air conditioning/heating, geothermal baskets, indoor and outdoor temperature sensors, etc.). The central box contains an algorithm that takes into account the system’s needs by integrating current and future climatic conditions as well as the building’s consumption history to optimize energy flow management. We are also developing a server that will allow data recovery to improve system management and optimization over time. You can think about buying or selling heat with your neighbour in the future.
Like in an energy exchange! However, in practice, it is more difficult to exchange heat than electricity. How do you plan this?
I prefer to talk about the thermal Smart Grid. It is easy to imagine neighbourhoods in which one or more loops connected together by highly efficient plate exchangers would be installed. In this case, we could exchange heat between several actors connected to this network of loops. For example, a supermarket that essentially needs cooling could resell the heat injected by its cooling units into the loop to another user such as a college or subdivision that has heating needs. Our system will integrate blockchain technologies to enable these exchanges in a secure way.
What are you looking for for the rest of your development?
Today, we have signed our first orders and we need to organize our supply chain. We would like to start recruiting 2 to 3 engineers very quickly in order to continue this dynamic. The objective for 2019 is to validate a demonstrator in each identified market segment (residential, health, education, tertiary, retail, industry, etc.). We are already present in the export market where we have several projects. We are looking for financial support to cover these development needs.