Permanent magnet generator for small and medium-scale hydropower: a systematic review

Renewable energy, particularly hydropower, is a key focus in reducing 
reliance on fossil fuels and mitigating environmental impacts. Permanent 
magnet generator (PMG) has emerged as a highly efficient option for 
converting hydro-energy into electricity, offering advantages such as high 
efficiency, compact design, and minimal maintenance. This review explores 
the latest developments in PMG technology, particularly for small and 
medium-scale hydropower applications. A systematic review method was 
used to analyze 617 papers and narrow them down to 20 relevant studies. 
Key findings highlight advancements in PMG design, including modular 
stators, counter-rotating turbines, and cordless designs that enhance 
efficiency and adaptability in low-speed environments. However, significant 
challenges remain, including the high cost of magnetic materials like 
Neodymium Iron Boron (NdFeB), thermal stability issues, and more robust 
control systems to manage variable water flow conditions. The review 
concludes that while PMG holds great potential for hydropower applications, 
Further research is needed to optimize material usage, improve design, and 
reduce costs. Future work should focus on developing new magnetic 
materials and innovative rotor designs to ensure PMG can provide a scalable 
and sustainable solution for global energy needs.