Projektinformation

In the northern Hessian city of Kassel, a versatile water supply system supplies high-quality drinking water to around 200,000 residents and numerous companies. Various extraction methods are used for this - from the spring areas in Habichtswald and Kaufunger Wald to deep wells in Simmers hausen and a groundwater recharge system along the Fulda. This means that the water supply in Kassel can be operated in a particularly adaptable and reliable manner.

But new challenges are emerging:

• Climate change is bringing with it longer dry periods and more frequent heavy rainfall events.
• Heavy rainfall events impair the water quality in spring areas due to turbidity - the water is temporarily unusable.
• Water availability is decreasing, while consumption is increasing.

At the same time, the energy transition is changing the framework conditions:
The increasing share of renewable energies is leading to fluctuations in the amount of electricity in the power grid. On windy and sunny days, there is an oversupply - with falling or even negative electricity prices.

However, these developments also present opportunities:

• Innovative, membrane-based treatment technologies now allow the cost-effective treatment of raw water that was previously not considered for drinking water supply.
• Flexible consumers, such as pumps and aerators, could be operated specifically when a particularly large amount of electricity from renewable sources is available.
• This would enable a cost-efficient and climate-friendly water supply - while at the same time relieving the strain on the electricity grids.

This is precisely where Flexilienz comes in:

By linking water and energy systems, Kassel's drinking water supply will become more robust against the consequences of climate change - and at the same time become an active part of the energy transition.

Core components of Flexilienz:

• Filtration technologies ensure that spring water remains usable even after heavy rainfall or is discharged in a targeted and time-limited manner.
• A pilot electrolyser produces green hydrogen from rinsing water - a sustainable dual use.
• Forecasting models link the electricity requirements of the water supply to stock market electricity prices and the renewable energy supply.

The Kassel real-world laboratory serves as a test environment for transferable solutions that can also be used in other regions - to conserve resources, reduce emissions and increase security of supply.

(Work package 1)

The aim is to provide clean drinking water at all times, even under changing climatic conditions. The focus is on two measures:

• Forecasting model for water quality:
  An early warning system is being developed with the help of data on volume flows and turbidity values. It enables the water supplier to detect contamination caused by heavy rainfall at an early stage and to activate alternative supply routes in good time.

• Innovative filtration technologies:
  New ultrafiltration modules are being tested that remove even the finest turbidity without using a lot of energy. This means that even sensitive springs such as the one in the Habichtswald can be used in the long term.

(Work packages 2 & 3)

The project shows how hydrogen production can be intelligently linked to the water supply:

• Pilot electrolyser in the waterworks:
  A water electrolyser is to use backwash water from drinking water treatment to produce hydrogen in order to save raw water and conserve resources.
• Forward osmosis instead of energy-intensive desalination:
  A new type of membrane system is designed to produce ultrapure water directly in the electrolyser and would therefore be a sustainable alternative to conventional processes.
• Cascade use of by-products:
  The oxygen produced during electrolysis is to be used to deferrize the well water and the waste heat used to heat the building.
• Grid compatibility:
  The electrolyser should preferably run on electricity from the waterworks' own solar system or atlow exchange electricity prices, thus helping to stabilize the electricity grid.

(Work package 4)

In Kassel, water has to be pumped over large differences in altitude into elevated tanks - an energy-intensive process. By analyzing the storage potential of the elevated tanks, it will be determined whether this energy consumption for water pumping and treatment can be shifted to periods with low electricity prices without jeopardizing the security of supply.

This work package includes

• Creation of a digital image of the supply network:
  In a pilot zone, the entire water network with pumps, compressors, storage tanks and consumption data is modeled virtually.
• Intelligent load shifting:
  Based on available weather, production and consumption data as well as the electricity exchange price, it is then determined whenenergy consumption in the water supply system can be shifted in time.
• Electricity market-driven control:
  In a simulation environment, consumers are automatically operated according to exchange electricity prices (day-ahead & intraday market). This results in daily updated schedules that can both reduce costs and relieve the electricity grid.