Geothermal Power Plant Production Boosting by Biomass Combustion: Cornia 2 Case Study

Abstract

Enel Green Power is dedicated to electric energy generation from renewable energy sources. Although development plans are mostly based on mature technologies, such as onshore wind and photovoltaic solar plants, project portfolio includes innovative hybrid plant configurations, i.e. plants combining more renewable energy sources.
Among them, the idea to boost an existing geothermal power plant using biomass combustion has been studied and recently applied. The scheme used for Cornia 2 project (Cornia 2 is an existing 20 MWe power plant, located in the Southern part of Larderello field) proved to be both technically feasible and economically viable. Before the project, the existing Cornia geothermal power plant, designed according to the standardized geothermal unit configuration with an installed capacity of 20 MWe, showed a production quite lower than the nominal capacity. The standardized units used in the Italian geothermal fleet of Enel Green Power are adaptable to steam inlet pressures from 5 to 20 bar but of course feature different power output when the reservoir makes available a steam pressure near to the lower limit. In this case, the enthalpy of the steam and, in turn, the power output, can be significantly increased by means of steam superheating within the design temperature limits of equipment and systems.
This paper describes the case history of the successful Cornia 2 project, from the initial feasibility studies to the end of the project execution, and highlights the good results of such a configuration in terms of plant efficiency and cost of energy, thanks to the synergy of the two renewable sources in this first-of-a-kind biomass-geothermal hybrid power plant.