“Waste water treatment accounts for 30% of energy consumption in many municipalities. » Faced with skyrocketing energy prices, elected officials are battling imaginations to try to lower the bill. This is the case in Laillé, south of Rennes, where Rennes Métropole is conducting an unprecedented experiment: the wastewater treatment plant is now equipped with solar panels to connect to clean and cheap energy from the sun. .
Follow the path of the sun
The station purifies waste water for 5,500 resident equivalents. It works with the activated sludge purification technique. In large round basins, the water gradually becomes clearer. Once cleared of pollutants, it can be released into the natural environment. “The largest consumable, it is the turbine that moves the water to aerate it, explain to the technicians. It alone accounts for 60% of the site’s electricity consumption. » Or 197,000 kWh last year.
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The turbine that brews the wastewater (in the foreground) now runs on solar energy. © Western France
To find an alternative solution, two companies from the Rennes basin brought their skills. They are known for their know-how. OK Wind for solar trackers and Purecontrol for artificial intelligence. Thanks to integrated motors, the two huge solar panels, each 117 m², follow the path of the sun to be even more efficient. “Those two currently cover 30% of the water treatment plant’s consumption”describes Louis Maurice, CEO of the OK Wind group.
Thanks to motors integrated into the masts, the trackers follow the course of the sun to be even more efficient. © Western France
Amortized in five or six years
There is increasing demand for his company. “ Half of the calls we receive are from manufacturers or farmers concerned about rising energy costs. » These two solar trackers, the largest extras in the catalog, represent an investment of €100,000, amortized in just five or six years. “It is very economical for the future”admit the managers of Rennes Métropole, who want to develop this solution in other equipment.
The town of Laillé has also installed shade houses with photovoltaic panels on the car park, near the multipurpose room. © Western France
The process will be further improved. Currently, 68% of the energy produced by the two trackers is consumed, “through peaks and troughs” because it is necessary to take into account the sunshine, the times of the day when the turbine starts, etc. Optimizing the installation is the task of the company Purecontrol. “We link classic automation to artificial intelligence, describe those responsible. Based on the collected data, the algorithm will make it possible to optimize energy consumption, with savings of 15 to 20% on the energy bill. »
The Territorial Air and Energy Climate Plan (PCAET), initiated by Rennes Métropole, has set itself ambitious targets, with a reduction in energy consumption of 40% by 2030 and 60% by 2050. Work carried out in all directions . In the 43 municipalities of the metropolis, this concerns sanitary facilities, but also public lighting. There is also a major project for the thermal renovation of buildings.