This is what Bondera Consult states in a research report entitled “Wastewater Treatment Plant (WWTP) as a Smart Energy Hub”, which was drawn up on behalf of the Water Boards Consortium.

Limited capacity of the power grid
One of the main obstacles to the energy transition is the limited capacity of the power grid. This is why the Federation of Water Boards is undertaking research into options for using wastewater treatment plants to contribute locally to solving this problem.

With 325 wastewater treatment plants in the Netherlands where different energy flows of high volume congregate, the idea arose to investigate the potential of a wastewater treatment plant as a smart energy center.

4 items
An energy hub is a node in an energy system where different energy carriers come together and coordination between supply and demand, storage and transfer is possible. The concept has 4 important components: sustainable energy production such as wind and/or solar energy, consumption, storage and infrastructure in the form of an electricity grid.

A sewage treatment plant is a huge energy consumer with a relatively continuous usage pattern, numerous energy conversion options, and flexibility. For example, biogas as a fuel can be converted into heat, electricity or green gas, additional conversion and/or storage systems can be installed such as an electrolyzer or battery and the installation of heat and power (CHP) can be stopped in the event of sustainable energy overproduction. Through these actions, the power grid can be mitigated and the sewage treatment plant can act as a smart power hub.

2 cases
Bondera examined two cases for the report, Harderwijk wwtp and wwtp Kampen.

In both wastewater treatment plants, grid congestion is an obstacle to sustainable energy generation, but the site provides an opportunity to achieve sustainable electricity generation. For the Harderwijk wastewater treatment plant, existing physical opportunities for improvement on both the wastewater treatment plant and the power grid were examined. For the Kampen wastewater treatment plant, further research has been carried out on green hydrogen production capabilities.

green hydrogen
In particular, the analysis related to green hydrogen production using the electrolyzer has yielded interesting insights for the Kampen WWTP wastewater treatment plant. Combining a 2.5 MW electrolysis system with a 4.8 MW wind turbine and a 1.0 MW solar park is cost-effective, the researchers said. With these systems, approximately 95 percent of the electricity produced can be used sustainably. Without the electrolysis system—or other applications through which electricity is used, stored, or converted—nearly 44 percent of sustainably generated electricity would be lost through downsizing.

Without the electrolyzer, 7.59 GWh is returned to the power grid. With the electrolyzer, that can be limited to 2.30 GWh. An electrolyzer that produces green hydrogen also puts less stress on the power grid. Bondera concludes, “Based on the estimate provided by the Drents Overijsselse Delta Water Board, there is space available for an electrolysis system at virtually all wastewater treatment sites within the Water Board.”

From 100 to 150 megawatts of space
The Harderwijk case showed that optimization and local coordination of generation and consumption can contribute to reducing the burden on the power grid. This could create additional space for a more sustainable generation.

The researchers: “A conservative estimate of the impact of an average wastewater treatment plant as a power hub is reduced to approximately 0.5 MW of physical space on network connectivity that is flexibly provided and can be used to relieve congestion in the network. In the Netherlands, where there are 325 wastewater treatment plants, this may mean that 100 to 150 MW of physical space will be available on the network connection. Complications of this can be achieved when coordinating with other key users.