Solar Magazine – Water Boards: production of green hydrogen in wastewater treatment plants as an alternative to increasing the electricity grid

This is what Pondera Consult states in the research report “The wastewater treatment plant (WWTP) as a smart energy hub”, written on behalf of the Union of Water Boards.

Limited power grid capacity
One of the main obstacles to the energy transition is the limited capacity of the electricity grid. This is why the Union des Régies de l’Eau commissioned research on options for using wastewater treatment plants to help solve this problem locally.

With the 325 wastewater treatment plants in the Netherlands where various energy flows of a substantial size meet, the idea was born to study the possibility of the wastewater treatment plant as a smart energy hub.

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

A wastewater treatment plant is a large consumer of energy with a relatively continuous use pattern and many options for energy conversion and flexibility. For example, biogas can be converted as fuel into heat, electricity or green gas, additional conversion and / or storage systems such as an electrolyser or battery can be installed and the cogeneration plant (CHP) can be stopped in the event of a sustainable overproduction of energy. Thanks to these measures, the electricity grid can be relieved and the wastewater treatment plant can function as a smart energy hub.

2 cases
Pondera examined 2 cases for the report, namely Harderwijk wwtp and wwtp Kampen.

In both treatment plants, grid congestion is an obstacle to sustainable energy production, but the location offers an opportunity for achieving sustainable electricity production. For the Harderwijk wastewater treatment plant, the existing physical opportunities for optimization both on the wastewater treatment plant and on the electricity grid were examined. For the Kampen wastewater treatment plant, the possibilities of producing green hydrogen have been further explored.

Green hydrogen
In particular, the analysis concerning the production of green hydrogen with an electrolyser provided interesting information for the Kampen wastewater treatment plant. The researchers said, “Combining a 2.5 megawatt electrolysis system with a 4.8 megawatt wind turbine and a 1.0 megawatt peak solar farm is cost effective. With these systems, around 95% of the sustainably produced electricity can be used. Without an electrolysis system – or other applications with which electricity is used, stored or converted – about 44 percent of the sustainably produced electricity would be lost through reduction. ‘

Without an electrolyser, 7.59 gigawatt hours are reinjected into the electricity network. With the electrolyser, this can be limited to 2.30 gigawatt hours. The electrolyser which produces green hydrogen also places less strain on the electricity network. “According to the estimate of the Drents Overijsselse Delta Water Board, there is space available for an electrolysis system at almost all wastewater treatment sites within the waters ”, concludes Pondera.

100 to 150 megawatts of space
The Harderwijk case has shown that local optimization and coordination of generation and consumption can help alleviate the load on the electricity grid. This can create additional space for more sustainable production.

The researchers: “A conservative estimate of the impact of an average wastewater treatment plant as an energy hub comes down to around 0.5 megawatt of physical space on the grid connection which is made available in a flexible and flexible manner. can be used to relieve network congestion. In the Netherlands, where there are 325 wastewater treatment plants, this could mean that 100 to 150 megawatts of physical space will become available on the grid connection. A multiple of this can possibly be achieved in coordination with other large users. ‘