The electric losses in electric generators cause an increased temperature, which reduces the efficiency and may damage the machine. Cooling air flow is therefore applied. The air flow is mostly driven by the rotating parts, but since the generators are not designed for optimal air flow it contributes with about 30% of the total efficiency reduction. It is also important that the cooling is applied where it is needed, to give a uniformly distributed temperature. With the new large-scale intermittent energy production facilities, the variation in the power output in time will increase, which yields damaging temperature fluctuations.
Electric generators have been built for more than 100 years, and the cooling is mainly based on experience. To further reduce the losses and temperature variations, new knowledge is needed on the details of the air flow, and new design methods are needed. We are therefore developing and evaluating numerical (CFD) and experimental (PIV, rapid prototyping) methods that can be used for detailed studies of the air flow in electric generators.