FIDI TOSCANA | MITICO: The CAPSTONE C30 Microturbine Fueled by Vegetable Oils
The MITICO project demonstrated the feasibility of converting a CAPSTONE C30 microturbine to operate on pure vegetable oils and acidic refining oils, aiming to leverage renewable biofuels and reduce the use of fossil fuels in distributed generation. Spike Renewables contributed to the engineering development of the fuel system and the plant modifications required to ensure operational stability, proper fuel atomization, and safety across all operating phases.
Challenges of Vegetable Fuel
Vegetable oils have much higher viscosity than diesel, different thermal behavior, and a higher content of impurities. Oil analyses show how these factors directly affect atomization, evaporation times, and combustion quality. To make the C30 compatible with such fuels, it was necessary to intervene on fuel thermal management, injector geometry, and control logic.
Preheating System and Dual-Tank Circuit
Spike Renewables designed a fuel supply circuit based on progressive oil preheating, maintained within an optimal temperature range using heat recovered from exhaust gases and dedicated electric heaters. This reduces viscosity and allows air-blast injectors to operate under stable conditions. The circuit also includes a dual-tank system with automatic switching: start-up and shutdown always occur with diesel, while oil fueling is activated only once the fuel reaches the ideal temperature. This solution prevents deposits in the conduits and protects the pump and injectors.
Atomization Optimization
Fluid dynamics analysis of the injectors showed that vegetable oil requires smaller droplet sizes than diesel to achieve comparable evaporation times. Theoretical studies based on Lefebvre and Brookhaven correlations identified the optimal fuel temperature range and the required increase in atomizing air flow. Injector geometry was adjusted to improve mixing and promote vaporization before entering the combustion chamber.
Experimental Results
Tests confirmed that the modified microturbine can operate on vegetable oils while maintaining stability and output. At full load, 29 kWe was achieved with a consumption of approximately 11 l/h, corresponding to an efficiency of 27%. Emissions showed a slight increase in nitrogen oxides, while carbon monoxide was lower compared to diesel operation. Correct start-up and shutdown procedures prevented fouling and ensured operational continuity.
A Step Forward for Multi-Fuel Turbines
MITICO represents a pioneering case of integrating microturbines with plant-based biofuels. Spike Renewables’ activities, from fuel circuit design to control logic definition, demonstrate that with proper adaptations, microturbines can efficiently operate on renewable, locally available fuels, opening new opportunities for sustainable distributed generation.