Turbines |
Bulgarian experience In Bulgaria NEK is working hard on a rehabilitation
programme for modernisation of its hydro facilities. At the beginning of 2024, a large-scale rehabilitation of the largest hydropower cascade in Bulgaria, Belmeken-Sestrimo-Momina Klissura (with a total installed capacity of 735MW in generating mode and 104MW in pumping mode) was completed. Then in December 2024, NEK successfully finished
rehabilitation of unit 2 at the Chaira pumped storage hydropower plant. From the outset, the scale and complexity of this project is described as exceeding the usual engineering challenges, and as such, innovative approaches and non-standard solutions were required. Implementation of this solution took 12 months of intensive activities on a three-shift basis by the teams of the contractor consortium and NEK staff. Throughout 2025, two further hydro units will
Above: Penstocks leading water into the Vamma hydropower station in Norway. Photo by ANDRITZ
Below: Downstream view of Vamma hydropower station. Photo by ANDRITZ
Bottom: Inside of the power station and Vamma’s unit 11. Photo by ANDRITZ
be repaired in parallel at the Chaira site. In January, NEK signed a contract with Toshiba Corporation of Japan for the repair of unit 1. As the designer and original equipment manufacturer of the plant, Toshiba Corporation’s expertise will ‘ensure the best technical solution for the facility’, according to NEK. The hydro unit is in its original condition and no rehabilitation work has been carried out on it since its commissioning in 1995. Contract works will commence as soon as possible and the unit is expected to be back in operation in 2026. NEK also signed a contract with the Austrian consortium Voith-ABB for the repair and rehabilitation of hydro unit 3. For this, a special engineering solution will be developed and implemented, similar to the one implemented for the rehabilitation of hydro unit 2. Preparatory works for the repair of hydro unit 3 are underway, and NEK has already completed dismantling of the generator section of the hydro unit. NEK says such signed agreements underline the importance of long-term partnerships and innovative solutions in the energy sector, which play a key role in ensuring the security of the electricity system.
Portable turbines The increasing need for reliable, decentralised energy
solutions in remote and off-grid locations, where access to traditional power infrastructure is limited or unavailable, is driving the development of portable power sources, new research claims. In such areas, where conventional energy sources
are either impractical or too costly, micro hydropower systems, particularly the Archimedes screw turbine (AST), are said offer a promising solution. These turbines can efficiently generate power from small streams,
irrigation channels, and wastewater flows, even in low- head, low-flow conditions, without the need for complex installations or large-scale infrastructure. Portable hydropower turbines are turbines with a scale below 5 kW and which can be easily carried by hand from one place to another due to their light weight. A recent study published in Scientific Reports evaluated the potential of AST as an improved portable hydropower turbine. The turbine in question, as researched by Khan et al, was manufactured from stainless steel material according to design parameters and installed in the laboratory. Experimental testing was performed at different discharges and different angles of inclination of the screw shaft to measure power outputs and overall efficiencies. The maximum overall efficiency obtained was 70% at a flow rate of 0.5 ft3/s and at an angle of inclination of 30°. The power output at maximum overall efficiency was 42 watts and hydraulic efficiency was 75.5%. At the flow rate of 0.3 ft3/s and an angle of inclination of 55°, the turbine produced a minimum power output of 22.8 watts and an overall efficiency of 39.4%. Experimentation revealed that the flow rate and inclination of the turbine shaft affect the turbine power output and overall efficiency. The portable AST offers substantial scalability
potential, particularly in off-grid rural communities. The compact and transportable nature of the turbine allows for easy deployment in various environments, providing a versatile solution for sustainable energy generation in diverse settings. Its ability to operate in low-flow conditions further enhances its scalability, making it suitable for a variety of water sources which may not be suitable for traditional hydroelectric turbines. ASTs require regular maintenance to address wear, corrosion, and sediment buildup, especially in remote or harsh environments. Looking to the future, the authors say logistical challenges with a portable AST include transportation to remote areas with limited resources, while environmental conditions such as water flow variability and ecosystem impact must be carefully considered during deployment. And although 3D printing offers a promising solution to address manufacturing imperfections in the development of such portable turbines, its feasibility for large- scale production, particularly in low-resource areas, requires careful consideration. Factors such as material costs, production speed, and the availability of 3D printing technology may limit its practicality in such contexts. The authors add that further research and experimentation are needed to assess whether 3D printing can be effectively scaled for broader implementation in these low-resource areas.
References
Development of a sustainable portable Archimedes screw turbine for hydropower generation by Nouman Khan, Muhammad Kaleem Sarwar, Muhammad Rashid, Hafiz Kamran Jalil Abbasi, Saif Haider, Muhammad Atiq Ur Rehman Tariq, Abdullah Nadeem, Muhammad Ahmad Zulfiqar, Ali Salem, Nadhir Al-Ansari Abdelaziz M. Okasha, Ahmed Z. Dewidar & Mohamed A. Mattar. Scientific Reports | (2025)
15:5827.
https://doi.org/10.1038/s41598-025- 90634-8
24 | April 2025 |
www.waterpowermagazine.com
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