A fifth unit, of 38MW capacity, is being added to the 110MW plant. The new unit is to be in service in 2012, and the plant would then be largest on the river, the company has said.

The plant was built in 1978 near Baden Baden and generates approximately 740GWh of electricity per year.

Work on site was expected to start last year but final planning approvals were only received at the end of last month though early preparatory works had already commenced on site. According to the initial schedule, the new turbine was to be commissioned by mid-2010.

The plant is operated by Rheinkraftwerk Iffezheim, which is owned jointly by equal partners EnBW and Electricite de France (edf). EnBW is leading the expansion project.

EnBW said just over two years ago, when calling for expressions of interest in the expansion projects, that a 40MW Kaplan unit was being considered. However, the unit is to be 38MW, which is the same size as detailed in early project information.

The project, approved in late 2005, calls for the powerhouse to be enlarged and also installation of a new penstock and tailrace.