A novel biomass-driven cogeneration system for zero-energy buildings

This study proposes and evaluates a new cogeneration system for zero-energy buildings. Zero-energy buildings are those in which the net electrical energy exchange between power grid and building equals zero. The proposed system is comprised of a biomass gasifier, an internal combustion engine, a double-effect lithium bromide-water absorption chiller, a backup boiler for hot water production, a gas storage tank, a hot water storage tank, and two heat exchangers. The system is supposed to provide the building with the electricity, hot water, heating and cooling requirements over the year. Besides presenting a functional strategy for the proposed system, this study evaluates the sensitivity of the objectives of the system (i.e., fulfilling the electricity, hot water, and heating and cooling requirements) to some main decision variables, including the capacity of engine, chiller and boiler, the volume of hot water tank, the start-up time of the internal combustion engine. The results indicate that the proposed system is able to support a zero energy building. The results also demonstrate that an increase in the input power of the engine helps to achieve the goal of zero-energy buildings. Moreover, it is observed that the system is most economical when the cooling capacity of the absorption chiller approaches the heating and cooling demands of the building. The results also indicate that the start-up time of the combustion engine would be more influential in the case of high electricity demand conditions.