A small size combined system for the production of energy from renewable sources and unconventional fuels

Nowadays, the development of new power plants capable of effectively using non-conventional energy sources is strongly desirable in order to obtain a significant reduction in costs of energy. In this regard, this paper proposes a new small scale (about 100 kW) combined cycle plant which can be fired externally by any kind of biomass. Particularly, the research activity presented here is concerned with the preliminary design of this innovative plant, which will be built, by means of a project funded by “Apulia Region”, at the LabZero Research Centre of Polytechnic University of Bari in the south of Italy. The goal of the paper is to demonstrate the effectiveness of the plant in terms of energy efficiency and availability and reliability of its components. The plant is mainly composed of a centrifugal compressor and a centripetal turbine of an automotive turbocharger, with the working fluid (clean air) being heated in a high temperature heat exchanger (HTHE) by using hot flue gases produced in an external combustion chamber burning biomass. The clean hot air expands in the turbine and then feeds the combustion chamber, where biomass is burned. In order to increase the efficiency, the flue gases exiting the HTHE are delivered into a heat recovery steam generator to generate water steam which can finally expand through a rotary actuator. Two configurations, employing an open Rankine cycle and a close one respectively, are analysed, and the use of biomass is compared with methane.