Molten carbonate fuel cells to improve the perfomance of CHP in wastewater treatment facilities

Description

The concern about environmental sustainability brought about by global warming in the last decades along with the scarcity of fossil fuel resources has fostered the research in renewable energies, high efficiency power generation systems and carbon dioxide capture and storage opportunities. The present work shows the performance of a system closely related to these three research areas. It focuses on a hybrid system composed by a reciprocating engine set (ICE) fuelled with biogas (BG) and a bottoming molten carbonate fuel cell network (MCFC) for active CO2 capture purposes. The proposed hybrid system constitutes the cogeneration unit of a wastewater treatment plant (i.e., driven by renewable energy) where electricity is generated efficiently and environmentally harmlessly thanks to the smart integration of two dissimilar subsystems in one of which CO2 is captured. In addition, the system has the potential to be economically interesting for various reasons. First, it is possible to enjoy more favourable market conditions (special regime in Spain) by using the heat rejected by the ICE to generate additional power and control the production of biogas. On top of this, there is a new business opportunities in the International Emissions Trading Market where CO2 can be traded. Despite these gains, there are also important economic drawbacks to be considered, mostly due to the added investment costs of the MCFC and the corresponding operating and maintenance costs: timely overhauls and the need to back up the fuel cell with a certain amount of natural gas (NG) limited to 10% of the annual heat input from fossil fuels.

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