A case study of an hybrid solar-sugar cane biomass power plant

Mariana Fonte Boa Rodrigues¹; Mario Siqueira¹

¹ Universidade de Brasília

doi:10.20906/CPS/COB-2015-1105

Resumo

The recent and ongoing Brazil energy crisis along with environmental concerns urge for solutions that can increase the offer of dispatchable renewable energy. In this work, a case study of a hybrid solar-sugar cane biomass power plant was investigated. The motivation to do so is that in co-generation systems based on the sugar-cane biomass (left-over after cane juice is extracted), a system adopted in several ethanol-sugar mills, the power block is loitered in between harvest seasons (four to five months). The concept is that a concentrated solar power (CSP) field, able to generate high pressure water-vapor needed for power production and industrial processes of the mill, could be deployed in parallel to biomass boilers during intense direct normal radiation (DNI) periods, such that biomass could be stored for periods when DNI is not available. A study-case of a real sugar-cane mill located in the state of Goiás was performed. The mill has a 40MW power block installed as part of its co-generation system, which generated a mean value of approximately 20MWh per month during last harvest season (April to November). Simulation of solar field performance was done using the freely available System Advisor Model (SAM) developed by USA National Renewable Energy Laboratory (NREL). The CSP technology of choice was central tower. This choice was due to the fact that water-vapor temperature in excess of 500oC is required for the newer sugar-cane mill power plants. Additionally, no thermal storage is required given that biomass is readily available for low-DNI periods. So, direct steam generation in the receiver was chosen for water-vapor production in the simulations. Hourly solar resource and meteorological data collected in Brasília as part of SONDA project was used in the calculations because no high-quality data was available for the exact location of the mill. Preliminary results showed that the solar field thermal output was highly variable during the year with the highest over 20700MWh in August and lowest around

Palavras-chave: Renewable energy; solar energy; sugar-cane biomass; Cogeneration