31 Jul 2014

Enabling sustainable power plant developments along the Elbe River

Hydraulic modelling to support planning and approvals for prospective power plants

We used hydraulic modelling to support planning and approvals for prospective power plants in Hamburg, Germany. 

The tide-influenced part of the Elbe River just downstream of Hamburg has experienced low oxygen conditions, which negatively impact the fragile ecosystem. With new power plants planned along the river, several concerns were raised related to cooling water discharge from the power plants into the river and the consequent impact on the aquatic environment. 

The operation of new plants along the river would likely impact the fragile ecosystem. As such, harsh oxygen conditions needed special consideration when planning new developments because power plants utilise cooling processes which generally involve uptake from and discharge to the river. During the cooling water passage, the water is heated and a considerable amount of the plankton dies. The discharged water provides more material (detritus) for bacteria to mineralise and lower oxygen concentrations further. 

To address these concerns, the adjacent federal states decided to develop a heat capacity plan. The plan was used to document temperature changes as well as the ecological effects (such as changes in dissolved oxygen) in the Elbe Estuary. 

We developed an ecological hydraulic model of tidal Elbe that helped calculate temperature and oxygen changes with respect to ebb and flood tides as well as the time required for mineralisation of algae. The model encompassed all relevant biological and chemical processes which have an influence on dissolved oxygen such as nutrient cycling, primary production, and the mineralisation of dead organic matter. 
We carried out comprehensive oxygen and temperature studies for some existing power plants using our MIKE 11 (one-dimensional models), MIKE 21 (two-dimensional models) and ECO Lab software. Our model focussed on controlled modelling of all single cooling water channels and variables such as maximum heating temperatures, oxygen saturation and plankton mortality. 

With the help of our modelling studies, it was possible for authorities and power plant operators to outline optimal dimensions for the usage of cooling water from the Elbe River with respect to ecological resilience. This in turn will help them sustainably plan new power plants and other developments along the Elbe River without causing further damage to the aquatic environment.