OFF DESIGN STUDY OF AN INTEGRATED CSP - MGT - ORC COGENERATING PLANT

One of the most important challenges for small scale power plan ts is the optimization of the thermodynamic cycle based on the thermal energy source, whether it is an externally fired com bustor, solar energy collectors or waste heat from topping processe s. The choice of the most favourable working fluid is also an im portant objective. Moreover, a crucial goal is the search for optimized plant configurations ensuring the best energetic results while being characterized by reasonable costs, so more suita ble for the widespread diffusion of distributed energy systems. In particular, this paper deals with the study of a combined cycle CHP plant mainly consisting of a topping micro-gas turbine a nd a bottoming ORC system. Furthermore, a hybrid thermal energy s upply is considered, combining th e use of biogas with thermal power from a solar field. In order to pursue low-cost objective, classical similarity criteria have been used at first to estimate the adaptability of a radial flow turbine equipping down-sized turbocharged engine to an orga nic working fluid. Then, a CFD validation has been carried out also allowing the determination of the characteristic curves of the radial flow turbine. The av ailability of the characteristic maps of the rotating components allowed to reliably estimate the off-d esign response of the integrated system, thus verifying its regulation capability needed to match variable heat and power demands from possible users and to face changes in the solar radiation intensity incident on the on the parabolic trough collect ors. Finally, a CFD analysis of the reacting flow through th e mGT combustor has been conducted