Background Hydroelectric power accounts for 10% of the total EU electrical power production. Large dams have in the past been used to produce hydroelectric power but for environmental reasons such constructions are no longer tolerated in the EU. There are also a very large number of smaller hydro power weirs in the rivers of Europe, which were constructed to prevent erosion and are characterised by a low turbine head. The main drawbacks of these weirs is that the energy output is not economical and fish are unable to pass through the constructions, which as a consequence has reduced the number of fish and the diversity of species in European rivers. Objectives The Moveable HEPP project aimed to demonstrate the potential of a movable hydroelectric power plant and prove that it can operate economically even at low turbine heads. Pilot actions were to be implemented in existing weirs and expected to create substantial ecological improvements. As an alternative to the existing hydroelectric power plants, the proposed moveable system was anticipated as offering a solution for both economical power generation and a construction which allows fish to pass through. Results This project successfully proved that its new hydropower technology, known as ‘Moveable HEPP’, can operate effectively as a source of renewable energy in a manner which does not adversely hinder the natural ecosystem functions of river habitats. Two test sites were used to introduce full-scale HEPP systems into existing river weirs. These included installing both a complete turbine plus generator at each site. The technology operated as planned with its moveable components being able to work at different heights. Water flowing through the HEPP generated power and water also flowed over and under the HEPP equipment to facilitate free movement of fish. Studies on HEPP’s potential ecological impacts showed no threat to fish populations. Fish were even able to swim through the turbine as it operates at a low rotation speed. No problems were recorded concerning flood problems since no risk of damming occurred by a build up of debris around the HEPP plant. Tree parts and other floating matter simply moved over and past the HEPP plant as they flowed downstream. Gravel and other river bed matter were not affected by the HEPP and noise levels were considered low. HEPP’s economic advantages are attributed to high efficiency, lack of frequency converter, combined turbine and generator on one single shaft, and use of a permanent magnet for the stator which saves the power for electric magnetisation. Furthermore, HEPP avoids costs involved in compensatory measures for managing flood risks or the transfer of river bed matter. Calculations indicated that HEPP could create savings of 16% compared to a conventional plant, plus 11% higher returns (electricity sales) due to better efficiency. Combining these factors led the HEPP team to estimate that their technology could increase the ratio of ‘raw profit per investment sum’ by more than 40% (from 5.18% to 7.36%). Strong demand has been shown in HEPP from the commercial sector and the project’s website offers interested parties a preview of how the technology works in practice via live webcams embedded in working versions of the HEPP technology. The project has been awarded two prizes: the “NEO2010 - Innovationspreis der TechnologieRegion Karlsruhe” as well as the “Umwelttechnikpreis Baden-Württemberg“ (i.e. an environmental award for outstanding and innovative products in environmental technology: Hydro-Energie Roth won the first prize in the category Energy efficiency") in July 2011 Further information on the project can be found in the project's layman report (see "Read more" section).