Investigation of new renewable energy-based multigeneration systems for Saudi Arabia

Abstract

This thesis explores three hybridized, large-scale solar thermal energy multigeneration systems: System 1 combines solar thermal energy with biomass, System 2 with geothermal, and System 3 with a petroleum coke and biomass blend. Each system provides power, heating, desalination, and other commodities. The thesis aims to develop energy system flowsheets integrating multiple technologies and assess their exergetic and economic benefits through case studies in KSA. Although the systems are of different kinds and scales, their economic parameters are found to be similar in terms of payback periods. System 1 achieves energy and exergy efficiencies of 50.4% and 45%, respectively. It generates annually 1040 GWh of electric power, 860 GWh of cogenerated heat, 80 GWh of refrigeration, 1100 tons of hydrogen, 26000 tons of chlorine gas, 11,600 tons of concentrated aqueous sodium hydroxide, 11,300 tons of ammonia, 1740 tons of aqueous urea, 905,000 m3 of fresh water. System 2 generates 700 GWh/year of power, 1200 GWh/year of heating, 27,100 tons/year of methanol, 130 million m3/year of fresh water, 42,500 tons/year of oxygen with efficiencies of 22% energy and 30% exergy. System 3 generates 1200 GWh/year of power, 690 GWh/year of heating, 12,700 tons/year of hydrogen, 19,300 tons/year of dried dates, 290,000 m3/year of fresh water and 80 GWh/year of cooling. The energy and exergy efficiencies of System 3 are 83.2% and 64%, respectively. For all systems, the chemical reactors are modelled using the Aspen Plus, which helps determine the best oxygen-to-biomass fraction in the gasifier as 15% at the turbine inlet temperature of 1500°C for System 1, the optimum methanol synthesis temperature in the range of 250°C-300°C for System 2, and results in 1.5 H2/C as the best molar ratio in hydro-gasifier to enhance the synthetic methane production rate for System 3. The thesis study underscores the potential of multigeneration and hybridization in improving the economics and ecology of renewable energy systems and offering insights applicable beyond the case studies explored.