A unique solar and biomass-based system for integrated production of electricity, heat, freshwater, hydrogen and ethanol

Abstract

Renewable energy sources are expected to replace fossil fuels to hinder global warming. In order to use these sources more effectively, multigenerational integrated systems where they produce multiple useful outputs with the same input(s), are necessary. This study proposes a novel solar and biomass energy-based integrated system to produce electricity, heating, freshwater, and ethanol. Food waste is anaerobically digested to generate biogas which is then upgraded to biomethane by high pressure water scrubbing. Simultaneously, solar energy is absorbed by parabolic trough solar collector farm to generate power in an organic Rankine cycle and desalinate seawater in a multi-effect desalination unit. A part of the produced electricity is used to obtain hydrogen through an alkaline electrolyzer which is then converted to ethanol by the direct carbon dioxide hydrogenation. The system is modeled and analyzed to present the energy and exergy efficiencies of each subsystem, as well as the overall system. The useful outputs are calculated as 1672.8 kW electricity, 3846 kW heating, 2.06 kg/s freshwater, and 0.02813 kg/s ethanol. The overall energy and exergy efficiencies of the proposed system are found as 53.4 % and 41 %, respectively. It is demonstrated that coupling several subsystems in a conceptually correct manner is important to make them thermodynamically more sound, environmentally more friendly and sustainably more appealing.