This research presents the modelling and simulation of an innovative small-scale power system composed of a downdraft gasifier, an externally fired gas turbine (EFGT) and an Organic Rankine Cycle (ORC) as a bottoming unit for increasing the electrical energy generation. Olive tree pruning (217 kg/h) was the biomass used, producing more than 200 kWe and an electrical efficiency of 20.7%. The producer gas achieved suitable mole composition (H-2: 14.8%, CO: 19.5%, CH4: 2.2%, CO2: 9.3%, H2O: 12.0% and N-2: 41.5%), lower calorific value (4.53 MJ/kg) and gasification efficiency (89%). The hot producer gas was burnt directly at atmospheric pressure in an EFGT, producing 150 kW(e) and exhaust gases at 290 degrees C. Five ORC working fluids were studied to maximize the electricity generation: isopentane, benzene, cyclohexane, R113, R245fa. Isopentane was the most suitable fluid, reaching 57.1 kW(e) and 20.45% of ORC thermal efficiency. On the other hand, despite R113 gave minor electricity production (49.1 kW(e)), this allowed to generate thermal power for CHP applications. (C) 2017 Elsevier Ltd. All rights reserved.