A low-carbon multigeneration system based on a solar collector unit, a bio waste gasification process and a water harvesting unit

Abstract

In this study, we introduce and examine a novel multigeneration cycle powered by low-carbon bio-waste and integrated with a solar thermal component. This system is designed to convert sewage sludge into a variety of useful products. The cycle utilizes anaerobic digestion and gasification to produce biogas and syngas. Additionally, it incorporates processes for generating water and hydrogen energy, utilizing the atmospheric water harvesting unit and water/gas shift reaction, sequentially. The system employs a Rankine cycle, a Brayton cycle and two organic Rankine cycles (ORCs) for electricity generation. A significant portion of the heat and electricity in this proposed project is sourced from a waste heat recovery system. This innovative project not only presents a new structure and configuration for product generation but also addresses energy, water and environmental challenges concurrently. The energy system’s performance has been thoroughly assessed in terms of thermodynamics, environmental impact and economic feasibility. The proposed plant is capable of producing an estimated 17 920 kW of electric power, 3207.6 kg/h of hydrogen energy and 5.14 × 10−3 L/s of freshwater. Under these design conditions, the energy and exergy efficiencies of the system were determined to be 35.76% and 40.49%, respectively. Additionally, the exergy sustainability factor, the levelized total emitted carbon dioxide and the unit cost of total products were characterized to be 52.28%, 0.2145 kg per kWh and 0.05219 $ per kWh, respectively.