Multi‐objective optimization of a novel biomass‐based multigeneration system consisting of liquid natural gas open cycle and proton exchange membrane electrolyzer

Abstract

In the present study, multi-objective optimization has been conducted to optimize a novel multigeneration system that is based on biomass energy, and uses the cold energy of the liquid natural gas as a heat sink. The designed system is an integration of combined gas-steam cycle, a cascade Rankine cycles, a lithium bromide-water absorption refrigeration cycle, a proton exchange membrane electrolyzer, and a liquid natural gas subsystem. The proposed system aims to produce power, cooling, natural gas, and hydrogen. Following thermodynamic and exergoeconomic analysis, two conflicting objectives, that is, total product cost rate and exergy efficiency, are selected for the optimization process. The genetic algorithm is used to optimize the system and the Pareto front plot is achieved. The obtained results for this system reveal that the final optimization point has an exergy efficiency of 39.023% and a total product cost rate of 1107$/h. This point is a trade-off between thermodynamic and thermoeconomic single-objective optimization cases. In addition, the biomass gasification-gas turbine cycle, organic Rankine cycles, and proton exchange membrane have the highest exergy destruction rates, respectively. Finally, it is shown that the liquid pressure ratio of the natural gas pump and inlet temperature of the steam turbine have the most important effects on the balance between the selected objective parameters.

Thermodynamic design, evaluation, and optimization of a novel quadruple generation system combined of a fuel cell, an absorption refrigeration cycle, and an electrolyzer

“…Furthermore, the SOFC stack and the electrolyzer unit need auxiliary equations to simulate their electrochemical reactions. The resulted equations are solved using the Engineering Equations Solver (EES) software, and the following assumptions are used as well 3,22 : The system is in a steady‐state condition. The inlet air contains 79% nitrogen and 21% oxygen. The inlet fuel of the SOFC system is natural gas. All gases obey the ideal gas law. The cathode and anode outlets are at the same temperature as the fuel cell stack. Ambient conditions are = 101.3 kPa and = 25°C Heat loss to the environment is negligible. Contact resistances are negligible in the SOFC stack. Potential and kinetic energy and exergy changes are ignored. Refrigerant leaving the evaporator and condenser is saturated. The frictional pressure drops in the pipes, mixer, and GAX heat exchangers are neglected. The output streams from the generator and the absorber are in equilibrium. The approach temperature at the ends of the GAX heat exchanger is zero. …”

“…The second solution researchers have put forward is the usage of system's waste energy or stream in other cycles and design co/tri/multigeneration systems to increase system outputs, efficiency, and profitability and reduce pollution 2 . Solid oxide fuel cell (SOFC) is a high‐temperature fuel cell that many researchers have considered in various integrated schemes, such as cogeneration, trigeneration, or multigeneration systems 3 …”

“…2 Solid oxide fuel cell (SOFC) is a hightemperature fuel cell that many researchers have considered in various integrated schemes, such as cogeneration, trigeneration, or multigeneration systems. 3 Jia et al 4 studied the performance of a new combination of a SOFC, a biomass gasification unit, a gas turbine, and an absorption chiller to produce power, heating, and cooling. They concluded that increasing the air flowrate into the biomass gasifier and decreasing biomass moisture have positive effects on the system efficiency.…”

Multi‐objective optimization of a novel supercritical CO 2 cycle‐based combined cycle for solar power tower plants integrated with SOFC and LNG cold energy and regasification

“…Similar to specific exergy costing (SPECO) method, a cost value is assigned to every exergy stream of system, and the cost, exergy, and supplementary relations are employed for all system components. The thermoeconomic balance for a control volume at a steady state could be stated as below 57 :…”

Integration of biodiesel internal combustion engines and transcritical organic Rankine cycles for waste‐heat recovery in small‐scale applications

“…[9][10][11] Among the available technologies, internal combustion engines (ICE), 12,13 and organic Rankine cycles (ORC) 14,15 are in the spotlight of the industry and research community. 16,17 Particularly, the internal combustion engine is a well-known and reliable technology with the prospect to maintain a preeminent role in the next future. 18 Consequently, it is essential to continue developing this energy system, primarily increasing efficiency, and Acronyms: AB, auxiliary boiler; CHP, combined heat and power; COP, coefficient of performance; HRVG, heat recovery vapour generator; ICE, internal combustion engine; LMTD, logarithmic mean temperature difference; NPV, net present value; ORC, organic Rankine cycle; PBT, payback time; PES, primary energy saving; P-HEX, plate heat exchanger; RED, renewable energy directive; TES, thermal energy storage; TORC, transcritical organic Rankine cycle; WHR, waste heat recovery; WVO, waste vegetable oil.…”