The SNCU investigated to find another representative case study in France among its members. The test site of Odysseum in Montpellier has been chosen by the SNCU, in order to carry out additional studies and tests in other operational environments for district heating and cooling systems. This site has been selected for his networks in both heating and cooling energies, and the possibility to get a complete real study thanks to a relative small quantity of substations.
1 General description
Montpellier is a city in the South West of France. His district heating and cooling system was created in the 1970s. It is managed by a public-private company, the SERM (Société d’Équipement de la Region Montpelliéraine).
The complete Montpellier DHCS supplies heating and cooling for the city center, consisting in 800’000m² of offices, housings, public equipment and commerce.
In 2000, the SERM DHCS has been extended to the East with the Port Marianne district. Then, this additional Odysseum Hippocrate DHCS is operating in order to fulfill the heating and cooling needs from the climate and technical requirements for a new building area of 190’000 m², mainly divided into a clinic, a skating ring, an aquarium, offices, housings and commercial buildings. Thus, some connected user have specific energy needs profile with a high demand in both cooling and heating on the whole year, and which cannot respect a specific energy label.
This particular extension of the Montpellier DHCS will be the part making the real case study B of this H2020 project. It consists in 2’300m of heating and cooling networks, with 9’160 kW of heating power and 11’040 kW of cooling power needs. The layout of this network can be found in Annex 2. Pipes diameters varies according to the location from DN50 to DN500. 14 substations are connected with exchangers for both heating and cooling networks according to the following diagram:
In 2015, the annual global energy consumptions were 6’600 MWh for heating and 11’300 MWh for cooling (positive cold without the ring skating). In 2017, an important group of buildings will be also connected, adding another 7 substations with 1’200 kW of power heating and 1’500 kW of power cooling needs.
The energy powers used to feed this DHCS are:
• A thermal cooling power capacity of 11720 kW with :
o 2 Carrier CHP plants with a power per unit of 760kW
o 2 Carrier CHP plants with a power per unit of 600kW
o 3 power plants with a power per unit of 3MW
• A cooling system consisting in:
o 4 closed cooling towers with a power per unit of 3MW
o 4 opened cooling towers with a power per unit of 1’500kW
• A thermal heating power capacity of 13’500kW :
o 3 gas boiler plants with a power per unit of 3MW
o 1 heat exchanger from the Port Marianne biomass plant with a power of 4.5MW :
There is no particular thermal energy storage capacity set for this DHCS.
As no need of hot water for sanitary use was required, the hot network has been designed with low supply-return temperatures (60-40°). This level of temperature was also convenient to implement a process of heat recovery on the condensation network for the electrical group of the ice water production. The supply-return temperatures of the hot network respect the fallowing rule:
Regarding the cold network, the design temperatures are constants through the year with 7°C as supply temperature and -13°C as return temperature.
The available energy in the condenser of the groups solicited all year long to produce cold is not sent in the cooling towers, but recovered by heating up the return of the district heating. So, with this CHP system, 60% of the supplied heat is renewable. The additional heat required in the middle of winter was initially produced from gas, but is supplied from the Port Marianne biomass plant since 2014, located at 1 km far.
Eventually, the respecting small quantity of substations in this DHCS can guarantee an easy and complete deployment solution to monitor a whole DHCS. Besides, the low temperatures for heating, the under-zero temperatures for cooling all year long, and the use of a CHP making an interaction in the energy production between both district networks, shows the Odysseum Hippocrate DHCS as an interesting case for this H2020 project.
2 Current state and needs of improvement
As the DHCS is quite recent, the equipment are in very good general conditions. Every cold technical equipment has a “Manufacturer” contract with a specific preventive maintenance and a replacement guarantee. The water quality from the DHCS is monitored and treated. The preventive maintenance for the cooling towers are drastic in order to respect the regulation against the Legionnaires’ disease.
Moreover, the existing DH control system guarantees both a global view of the substations behavior and a post-optimization by monitoring the flowrates and temperatures settings.
However, the efficiency could be even better by monitoring and controlling the real time energy production and supply data, especially by integrating the 14 existing and the 7 significant upcoming substations.