On November 16th, 2018 a new coalbed methane (CBM) power plant was inaugurated in Yangquan, China.
The output of the plant is 30 MW with 30 gas engines gensets equipped with Leroy-Somer LSA 52.2 alternators. The output power is paralleled with the national grid.
Depending on the CBM quality, the gas engines have been designed for high concentration methane (>30%) and low concentration gas (12%-20%).
Due to the higher cost of the engines, gas generators are mostly used for continuous operations, running up to 6,000 or even 8,000 hours per year. To ensure the profitability of the power plant, the alternators need to match these requirements. With the use of high-grade magnetic steel, top quality copper wire and an industry-leading cooling system, Leroy-Somer alternators features some of the best efficiencies, durability and reliability on the market
Gas engines are more prone to vibration issues than diesel engines because of the instability of the gas flow and its changing quality. The alternators coupled to these gas engines need to withstand higher levels of vibrations.
Thanks to its robust alternator design, years of experience and feedback from the field, Leroy-Somer alternators can meet the harshest requirements. For this project, Leroy-Somer provided shaft drawings at early stage to validate torsional analysis with engine maker. The design has been confirmed to withstand any specified vibration level thank to a reinforced end-shield, oversized bearings and a double-bearing construction.
Gas supply instabilities also result in engine speed fluctuations. The Leroy-Somer Automatic Voltage Regulator (AVR) supplied with the alternators dampen the voltage response to speed fluctuations (derivative function) as long as the speed fluctuation remains within a +/-4% range;
China has the largest coal mining activity in the world. Analysis also indicates that generating electricity from CBM, as with conventional natural gas, has less than half the greenhouse gas effect of coal. If untapped, methane resulting from coal mining activity simply leaks into the atmosphere, where the greenhouse effect of methane (25 times higher than CO2) is applied with full force. Recovery of coal mine methane in advance of mining is then a major opportunity to reduce methane emissions and use an already available energy source.