District cooling

The boulevard Mabourc stretches gently from the Hotel Des Invalides towards the Seine. There is no special noise or steam release indicating the existence of a huge refrigeration facility in that neighborhood. However, Clinespace company has built a cold water storage tank with a capacity of 13,000 cubic meters from the beginning of 1999, twenty-five meters below the surface of the boulevard. Mr. Raid Massy, responsible for the production and expansion of cool water in Paris, states: “The coordination of such facilities with the urban environment is one of the important privileges.” And “this tank does not have any complications or negative effects on the boulevard surface and does not cause any damage in terms of sound pollution or visual pollution to the surrounding environment”.
The criterion of harmony with the environment has been considered by Climespace from the beginning. The main problem is to install equipment of this importance in the center of Paris while respecting the restrictions caused by maintaining the standards of urban architecture.
“This is the first of its kind in the world,” Mr. Raid Massy says excitedly. And “such a storage tank has never been built”. The experts who worked on this project did not rely on the same information and experience. This project was put into operation in the fall of 1999 and since June, it has provided 17.5 MV of cooling. In addition to the fact that despite these facilities, the construction of a cold water production center with a similar capacity was avoided, this reserve source has improved and strengthened the reliability coefficient of the cold water network of Climespace.
* A tank with thirteen parts, each of which has a volume of 1000 cubic meters.
Mr. Raid Massy explains that “this tank is not a multi-story type with a high height. Because with this type of tank, a height of 15 meters is required to have the desired capacity. This tank, which is built on the sixth floor of the basement of a parking lot, has a length of 135 meters, a width of 14 meters and a height of 7.5 meters, and the whole tank consists of 13 parts, each part having a volume of 1000 cubic meters. A volume equal to 1000 cubic meters (one part) is permanently kept empty so that the transfer of water from each part to this part is possible. Mr. Raid Massy explains that this method prevents cold water and hot water from mixing. In this way, cool water storage is possible and the maximum capacity of the tanks is used. This design allows cold water to be stored at a temperature between +1°C and +5°C and hot water at a temperature of +8°C and +15°C.
Several purposes have been considered for the construction of the Mabourg storage tank. At first, it was intended to create additional power for the entire network. The temperature of cold water that is currently stored is +40°C, which will be reduced to +20°C by the end of next year. As a result of this action, the cold storage capacity of the facility will reach 23 megawatts. With this storage method, peak consumption hours are transferred to off-peak hours. As a result, the average pumping cost is reduced because the system works continuously. Cold water is stored in the reservoirs during daylight hours (midnight) and is ready to be directed to the network during peak hours. According to Mr. Raid Massy’s estimate, the investment cost of the Mabourg station is 30% less than the investment for the construction of an equivalent cold water production center. Although the performance of this water storage station is completely different from the performance of a cold water production center, on the contrary, it has the advantage of being a reliable support for emergency energy storage, especially if its location on the network is well chosen.
* A complex system of valves
However, while designing these facilities, there have been many problems that have been left behind. In order to obtain the maximum capacity, the discharge pumps are installed at the same level as the tanks, where the problem of suction pressure (NPSH) is raised. In order for the tanks to be emptied correctly, it is necessary to predict the water branching point and the special device to prevent the vortex (rotation). On the other hand, a complex system of valves had to be considered in order to establish a balance between the input and output flow rates. In fact, the Zahir system is open and under atmospheric pressure, and this is what makes it more difficult to manage the amount of flows. Mr
Raid Massy emphasizes that the amount of water storage and the size of the discharge pumps have been determined accordingly. In addition, replacing one tank with another tank may stop the water flow. In this regard, it is necessary to explain here that this problem has been solved by adding a buffer tank and auxiliary pumps.
Another hydraulic limitation is that the reservoir is located on the sixth floor of the basement below the Climespase distribution network at street level, which has a volume of 20,000 cubic meters. In this way, there is a risk of draining the water in the network. To prevent the accidental transfer of water, various technical options have been adopted, which include materials and materials (valves, pumps, …) to the way of implementation. Among these new factors, the most important one is the expansion of the Climespase company’s network to the left side of the Seine River. While projects are underway to improve the local centers of cold water production in an auxiliary way along the river, there are also studies that consider the connection of cold water reservoirs to the network. In addition to the feasibility of the Mabourg reservoir, investigations and studies have been carried out, which will undoubtedly provide valuable help in expanding the network to new locations.