Polish company CEDI is working hard to enhance its presence in the small hydro industry at home and further afield. In doing so it has established a close working relationship with local Cracow University of Technology and clearly voices its belief that technological innovation is the way forward for small hydro.


CEDI was established in 2007 in the outskirts of Cracow in southern Poland. As an engineering company its focus was on innovative technology within the hydropower, oil and gas sectors, but its oil and gas activity was later sold and CEDI has since focused on small hydro.

The founder of CEDI, Mads Grahl-Madsen, is a graduate of The Norwegian University of Science and Technology and majored in the design of hydraulic turbines, pumps and turbo machinery. He has 30 years’ experience both as an academic and as a practising engineer.

CEDI presently has 11 employees, all with MSc or PhD qualifications covering areas such as mechanical, electrical, civil and environmental engineering and hydrology. The company has developed a close relationship with Cracow University of Technology, and some of CEDI’s employees have their main position at the university, working part-time with CEDI. This ensures CEDI access to updated technology and continuous research and development within core technologies such as control systems, power electronics and electrical machinery. This arrangement is beneficial to both parties. CEDI’s cooperation with the university allows them access to lab facilities, while the university benefits from using CEDI’s test equipment as part of their curriculum for students.

The part-time employment of university staff in CEDI also brings practical experience into the education of future engineers and at the same time gives CEDI the opportunity to recruit engineers with competence in core technologies relevant to the hydro industry. Similar models of cooperation between industrial companies and universities have been used for many years in Norway, and have been instrumental in several Norwegian companies’ success within the oil and gas sector. Experience has shown that such cooperation creates a competitive edge in a fast developing industry.

Technological development

CEDI was instrumental in the establishment of the Norwegian company Turbinova which held a patent for an innovative low head turbine where the turbine was integrated in the generator. As a consequence CEDI was given the contract of developing this turbine, which operates under variable speed.

Initial tests were carried out at Wroclaw University of Technology and Cracow University of Technology. On behalf of Turbinova AS, CEDI designed, manufactured, installed and commissioned two 75kW turbines in Biala Nysa in the south of Poland. The plant is located at an altitude of 250m, 600km from the Baltic Sea and utilises a head of 3m.

Although southern Poland has the Beskids and Sudetes mountains as a border against the Slovak and the Czech Republics, Poland is a flat country dominated by relatively small rivers running northwards. Power plants without or with only very small reservoirs will continue to be instrumental in the future development of Polish hydro power potential.

Such installations are characterised by relatively large fluctuations in flow and head and traditional technology such as Kaplan, Bulb and S-turbines will consequently suffer from significant variations in efficiency, as their performance is sensitive to such variations. If they are of a complicated design with heavily loaded mechanisms and bearings this can often create operational problems. CEDI and Turbinova’s concept, where the turbine is operated under variable speed, does not have the same disadvantages. The variable speed adds a degree of freedom in the same way the adjustment of the runner blade does in Kaplan, Bulb and S-turbines, but removes the performance dependency of the head. The use of a permanent magnet generator, developed by the Italian manufacturer Soga, likewise removes the need for heavily loaded thrust bearings as the integrated generator itself to some degree acts as a magnetic thrust bearing.

The variable speed concept also avoids operation outside the envelope where draft tube surges tend to be dominating and where pulsations can limit the operational area of traditional turbines. The turbines installed in Bila Nysa have been operated as low as 5% of nominal flow without occurrence of pulsations.

As always everything comes at a price. The variable speed concept is dependent on power electronics in order to supply a current of constant frequency to the grid. However, this in turn eliminates the installation of flywheels which in many small hydro plants is a necessity in order to get enough rotating mass to prevent variations in frequency due to changes of load. CEDI and Turbinova’s variable speed technology therefore will be very well suited in environments where the turbine has to be operated in isolated grids, or in rural areas where little electrical infrastructure are present.

Figure 2 shows a typical existing infrastructure in Poland, which as yet has not been utilised for hydro power purposes. In cooperation with an investor, CEDI has developed a concept where the turbine room is almost invisible and the electrical installation and control system is located above the flood mark. This concept will minimise environmental impacts as the site is situated within a European Ecological Natura 2000 area.

Nominal power is about 115kW with a head of 2.2m. During floods the turbine, due to CEDI and Turbinova’s technology with the integrated runner/generator where the gap between the stator and rotor is filled with water, can be flooded without damage to the installation. Tests have been successfully carried out at Cracow University of Technology, and the test generator has been submerged in water since late 2008. The power cables are connected to the integrated generator by subsea electrical connectors, while as mentioned the remaining electrical equipment is located above the flood mark. The small hydro plant is scheduled to swing into operation during 2013, and will have real time measurement of flow and head in order to continuously optimise performance.


The Polish market for small hydro power is mainly in the area of kilowatts rather than megawatts, and predominately utilises low heads. Focusing on technologies that can contribute to lowering investment and increasing production is therefore necessary in all relevant engineering disciplines. The presence of Green Certificates contributes largely to increasing the short term profitability for the investor in small hydro plants.

In Poland the market place is dominated by two types of investors: the professionals represented by the four major power groups and some non-Polish entities that focus on renewable energy, plus private investors that see there is money to be earned in the business. Hydropower can also be a conservative business and traditional solutions are often selected, and in this context the existence of Green Certificates can hinder innovation and more profitable solutions.

On the other hand, small hydro power would in most cases in Poland not be profitable without Green Certificates. Private investors focus more on low investment than technology production and operational costs of the installation when it comes to electro/mechanical equipment. Strangely enough the same investors frequently over invest when it comes to civil engineering works.

The mixture of ownership along rivers combined with very rigid operational restrictions set by authorities can create difficulties when optimising production within the Polish small hydro business. Although these restrictions are mostly based upon flood considerations and/or considerations in respect to fish migration, the installation of more sophisticated technology could substantially increase production. The technology and infrastructure are mainly there but not put into use. A more coordinated operational strategy would be welcomed.

The major obstacle, regardless of technology, is an unclear interpretation of Polish regulations in respect to renewables. Poland is in the process of developing and changing the Renewables Resources Law, and there is significant uncertainty and discussion in this area. Parliament plans to meet in summer 2012 to move this law ahead.

Due to the relatively long and labourious planning time for a small hydro plant, of which the authorities must take some of the blame, the Polish market will not be sufficient for CEDI to maintain a continuous sustainable operation. CEDI is therefore also focusing on other markets where our technology could have an impact on the development of small hydro power.

Southeast Asia is an area marked with large potential. Together with part-Norwegian owned company Spirit Electricity we are working in Thailand to introduce our technology. Through subsidiaries in the US (the AmNor Hydro group of companies) CEDI is also in the beginning of launching the variable speed technology into the US market.

These two markets differ from the Polish as they are not predominantly based upon low head applications, so CEDI has developed a variable speed Francis turbine solution for low and medium head. As with axial flow turbines there are significant gains in using variable speed technology for high specific speed turbines if the head or flow undergoes relatively large variations. Not only could the production increase substantially, but the variable speed option also enables Francis turbines to operate at very low flows without the occurrence of draft tube surges. Draft tube surges often limit the Francis turbine’s operational window to approximately 40% of the nominal flow. Through variable speed operation fewer aggregates could be necessary and consequently lower the necessary investment for the investor.

The Technical University in Madrid has demonstrated this through a number of publications, and also field investigations carried out in Germany financed by the European Union have shown that variable speed operation in many cases can be economically justified. CEDI has the technology, and believes that through its competence and experience can contribute to the development of small hydro. It is a business that worldwide is shouting out for innovation in order to contribute to the use of renewable energy.

The authors are Mads Grahl-Madsen (M.Sc.Eng), Agnieszka Operacz (PhD) and Joanna Kolodziej (Eng). www.creative-engineering.eu