• Energy Research
• 2021-2025close
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Abstract A novel combined cooling and power (CCP) system integrating a supercritical carbon dioxide recompression Brayton cycle with an ejector transcritical carbon dioxide refrigeration cycle (E-TCRC) is proposed to realize the effective utilization of nuclear power. In the proposed system, a portion of CO2 exiting the pre-cooler is used to drive the E-TCRC for generating cooling and recovering partial waste heat of sCO2 turbine exhaust. The mathematical model and economic model of the proposed system are established under steady-state conditions. Besides, the exergy efficiency and total product unit cost of the system are selected as the main criteria to evaluate system performance. Parametric analysis is applied to study the effects of four key parameters on the system performance. The CCP system, conventional separated cooling and power (C-SCP) system and ejector separated cooling and power (E-SCP) system are optimized by single-objective and multi-objective optimization. Single-objective optimization reveals that the exergy efficiencies of the CCP system are up to 1.08%pt (percentage point), 0.80%pt and 0.47%pt higher than those of the C-SCP system at the corresponding evaporation temperatures (−20 °C, −10 °C and 0 °C). Besides, the CCP system performs better than the E-SCP system at lower turbine inlet pressures. The multi-objective optimization shows that when the evaporation temperature increases from −20 °C to 0 °C, the total product unit cost of the CCP system decreases from 10.087 $/GJ to 9.668 $/GJ, and exergy efficiency increases from 59.25% to 60.97%.

Abstract Thermoelectric (TE) parameters provide indispensable data for the optimal design, accurate modeling, and performance assessment of off-the-shelf TE modules. However, the lack of unified characterization methods for these nonlinear data creates challenges for the design of large-scale TE systems. This paper aims at a thorough exploration of the accuracy, efficiency, and applicability of five typically reported characterization methods in terms of temperature-dependent material-level TE parameters (Seebeck coefficient, thermal conductivity and electrical resistivity). A common test setup was built and specifically improved for the convenient and high-precision measurement of heat rate. The four methods except for the Buist’s modified Harman method can characterize the satisfactory material-level TE parameters only if the thermoelectric generator (TEG)’s irreversible factors are considered including the thermal resistances of substrates and interlaminar contact resistances. The applicability of each method in a large temperature range is discussed by simulation beyond their inherent limits of adopted setups in this paper. Most methods show significant deviations at high temperatures due to their inherent parametric spatial-independence assumptions. From the perspective of their theoretical feasibility and practical accuracy, the quasi steady-state method is more advantageous than others. This research can guide the employment of characterization methods and assist the design and optimization of large-scale TE systems.

Combining CO2 electrochemical reduction (CO2R) and biomass gasification for producing methanol (CH3OH) is a promising option to increase the carbon efficiency, reduce total production cost (TPC), and realize the utilization of byproducts of CO2R system, but its viability has not been studied. In this work, systematic techno-economic assessments for the processes that combined CO2R to produce CO/syngas/CH3OH with biomass gasification were conducted and compared to stand-alone biomass gasification and CO2R processes, to identify the benefits and analyze the commercialization potential of different pathways under current and future conditions. The results demonstrated that the process that combined biomass gasification with CO2R to CO represents a viable pathway with a competitive TPC of 0.39 €/kg-CH3OH under the current condition. For all the combined cases, electricity usage for CO2R accounts for 36–76% of total operating cost, which plays a key role for TPC. Sensitivity analysis confirmed that the process that combined biomass gasification with CO2R to CO is sensitive to the price of electricity, while both CO2R performance and prices of stack and electricity are important for the processes that combined with CO2R to syngas/CH3OH. Validerad;2024;Nivå 2;2024-04-15 (hanlid);Full text license: CC BY 4.0