Standard uninterruptible power supply (UPS) systems for radio base stations use lead acid batteries stacks as energy storage device; the fairly short life cycle of such systems, not more than 3 years, together with the presence of highly polluting components make it costly in terms of money and environmental aspects. From these considerations originate the idea to develop an alternative UPS system based on compressed air storage able to replace the battery stacks and to satisfy more restrictive environmental requirements. This work is developed within the European project PNEUMA (PNEumatic Uninterruptible Machine - LIFE 04 ENV/IT/00595) with the final aim to develop some UPS demonstrators for an on site experimentation. In this paper it is described the way followed to set up an air turboalternator with a maximum power of 10.0 kW. Starting from the selection of the turbine, we decided to extract it from an ICE turbocharger because its size and its low cost matches our requirements. First of all, an experimental survey has been realized to test two turbines of different size: expansion ratio, corrected mass flow and efficiency have been measured varying inlet pressure and temperature. This activity led us to select the smaller turbine to develop the first pilot demonstrator; the turbine has been coupled to an high speed alternator (max. 60’000 rpm) by means of an elastic coupling. Some shakedown testing have been performed to verify the mechanical resistance and to test the power conversion system and the control system.

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