It is amazing what you can learn when you keep your eyes and ears open, provided you can find the time to use them. That is what I experienced during the POWER-GEN Europe conference and exhibition in Milano, Italy on 21-23 June, 2016. There were quite a number of interesting presentations on decentralized energy technologies and applications. Especially highlighted were the new features of decentralized systems with respect to a rapid response to required load changes, quick starting and fast ramping up and down of the output. Decentralized energy is very suitable to efficiently and economically fill the gaps between electricity production and consumption that baseload power plants leave, and that wind and solar-based generators especially create. This must be nothing new to you, our readers; for me it was a welcome confirmation of our common belief.
Usually obligations keep me from attending the sessions on generators, but this time the organizing Chair asked me to join one. Four panellists discussed the effects leading to wear and aging of synchronous generators. I always took the generator for granted when analyzing and discussing the dynamic behaviour of decentralized electricity generating units. Designing and drawing a generator was one of the tasks for my first degree in engineering. I did all the calculations on, e.g., magnetic flux, the gap between rotor and stator, electrical resistance and mechanical strength. However, I never took into account the stress on the machine resulting from temperature gradients during a rapid change in load. In practice, during and immediately after a fast increase in load, the windings and the surrounding material do heat up rapidly, but it takes a while before the rest of the machine reaches its equilibrium thermal situation. One panellist revealed that the additional stresses during a ‘normal’ startup results in some 30 equivalent hours of running. However, during very rapid loading or unloading, much higher stresses might occur. Consequently, generator design must also be adapted to allow dynamic operation without suffering excessively from wear. I always ignored this when promoting the flexibility of decentralized generation units. Even experienced engineers can see certain elements in a system as a ‘black box’ without considering the contents. Personally, I should have known better, since a few years ago I was asked to find the root cause of frequent damage to a large synchronous motor. It appeared then that thermal stresses during extremely rapid loading by the operators created an unusual shape of the shaft of the motor, resulting in destructive contact between stator and rotor. I hope that this magazine can soon receive an interesting article on generators that can reliably accept fast load changes.
Another eye-opener occurred at the exhibition when I met two representatives of a company that produces plastic inserts for exhaust gas ducts. Cogeneration installations that apply condensation of exhaust gases to capture the latent energy can have a fuel efficiency close to 100% based on the lower heating value of the fuel. However, corrosion of the stainless steel ducts downstream of the condenser sometimes takes place. That means traces of nickel and chromium end up in the condensate stream, which has negative consequences for the environment. The gentlemen told me that they could produce any size of insert so that corrosion could be prevented. They promised to write an article for our magazine.
These are just a few illustrations of how useful it can be to attend an event such as a POWER-GEN conference and exhibition. Just sitting behind your desk and hoping that the necessary information will automatically come to you will never work. Networking, and open ears and eyes, are required for that.
Dr Jacob Klimstra, Managing Editor