**2. Ultra-micro-gas-turbines**

Ultra-micro gas turbine generator, that is a power device with high power density, is analysed in this chapter. This generator, although the covered power range oscillates between 100 and 500 W, is characterized by reduced overall dimensions. Design issues and realization of the mechanical components is considered. The economic impact of these devices depends on the performance levels and the manufacturing costs, both of which have yet to be proven. Competitiveness of ultra-micro gas turbine generator with conventional machines in a cost per installed kilowatt is discussed.
