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Abstract Redox thermochemical reactor model integrated concentrating solar power technology is finding increased interest due to the enormous advantages of storing renewable energy into high-temperature heat flux and clean transportable fuel. From the perspective of designing a scalable direct solar irradiated receiver, the reactor optimum design and solar thermochemical energy storage performance have been investigated. Numerical models combined with experiments were developed for the analysis of engineering design parameters affecting the reactor efficiency. The shape of the cavity receiver including the size of the glass-covered target radiant received surface and reactor volume, especially the axial length of the heat-storing medium can be considered as important design issues for improving thermochemical energy storage efficiency. The reactor efficiency of storing sunlight with safer operating conditions is reported to 85.27% ± 0.85% during thermal charging up to 1787.725 K ± 30.58 K and 76.9% ± 0.11% during thermal discharging step at 1315. 16 K ± 7.53 K. Increasing heat losses via receiver insulation layer significantly affects the reactor thermal performance. This study demonstrated that the solar-driven thermochemical process has the potential of achieving high-temperature storable heat and solar fuel production. Appropriate geometric parameters were provided for the scalability from the perspective of industrial implementation.

Abstract The production of valued added fuels and chemicals via photocatalytic carbon dioxide reduction has attracted increasing attentions in recent years. Based on the traditional twin reactor configuration, a novel bubbling twin reactor is proposed to improve the conversion of carbon dioxide to methanol in this work. The multiphysical model for the bubbling twin reactor is developed and numerically simulated. The variations of the methanol production with the gas inlet flow velocity and gas inlet number are obtained. The results show that the bubbling twin reactor has a higher carbon dioxide conversion efficiency than the traditional one. Moreover, the methanol production subsequently increases as the gas inlet velocity increases. With the constant inlet gas volumetric flow rate, the production of methanol can be improved by increasing the gas inlet number.

Abstract CH 4 –CO 2 replacement method can not only recover methane from natural gas hydrate, but also implement CO 2 geological sequestration. The effect of CH 4 –CO 2 replacement with gaseous or liquid CO 2 from natural gas hydrates, and the stiffness evolution during the stages of CH 4 hydrate formation, free methane gas release, gaseous or liquid CO 2 flooding, and CH 4 –CO 2 replacement were experimentally investigated by in situ measuring the compressional wave velocity of hydrate-bearing sediments. The measured results showed that the P-wave velocity and amplitude of the hydrate-bearing sediments behave in the same way and decrease slightly because of the dissociation of CH 4 hydrate when free CH 4 gas was released and CO 2 gas was injected. At the stage of CH 4 –CO 2 replacement, methane hydrate may be coated by newly-formed hydrate which prevents CH 4 or CO 2 molecules passing through. Both the P-wave velocity and the amplitude gradually decrease with the increase of replacement percentage owing to the different properties between CH 4 hydrate and CO 2 hydrate. The elastic modulus of hydrate-bearing sediments was found to decrease with the dissociation of CH 4 hydrate and the formation of CO 2 hydrate, indicating the CH 4 –CO 2 replacement may weaken the rigidity of the sediment skeleton. However, the fluctuation of bulk stiffness is at a low level and the stiffness of hydrate-bearing sediments can still be maintained.

Abstract This paper reports on an algorithm for hourly simulation of ground-coupled heat pump (GCHP) systems. This algorithm integrates the newest analytical models for COP of heat pumps and for heat transfer of ground heat exchangers (GHEs). These analytical models make the algorithm computationally fast and efficient. The algorithm comprises 7 independent equations for solving 7 system variables, thus including C 14 7 = 3432 simulation scenarios. The algorithm is applied to hourly 50-year simulations of a GCHP for illustrating the computation efficiency of the algorithm. The simulation cases show that the COP and seasonal COP of GCHPs depend heavily on the mutual-cause coupling between the ground-side load and the temperature field in the ground. This coupling effect renders the high-resolution simulation highly necessary.

Abstract Post-refining of crude biomass liquefaction-derived polyols (biopolyols) to remove undesired carbonyl compounds is essential to improve the quality of biopolymers. One of the dominated carbonyl compounds in the crude biopolyols, butyl levulinate (BL), was hydrogenated to γ-valerolactone (GVL) over Cu-modified NiCoB amorphous alloy catalyst to explore a high-efficient hydrogenation upgrading catalyst. Cu0.5Ni1Co1B catalyst with metallic Cu particle size of 10.2 nm and the highest BL conversion of 74.6% was supported on the acid-activated attapulgite (H+-ATP) material. The synergistic effect between acidic and hydrogenated active centers in Cu0.5Ni1Co1B/H+-ATP catalyst was proved by NH3-temperature programmed desorption (NH3-TPD) to promote the conversion of carbonyl compounds compared to unsupported Cu0.5Ni1Co1B catalyst. Reaction temperature also showed a positive effect on the removal of carbonyl compounds especially for the acids and their esters. Under the optimum reaction conditions (140 °C, 1.0 MPa), the relative content of carbonyl compounds in crude biopolyols showed an obvious decrease of 10.3%, while the hydroxyl number of biopolyols increased by 140 mg KOH/g. Gas chromatography–mass spectrometry (GC–MS) analysis results indicated that the conversion of ethylene glycol condensation products and their monoesters or diesters of acetic acid and propionic acid was the major reaction during the process of hydrogenation upgrading of crude biopolyols. Cu0.5Ni1Co1B/H+-ATP catalyst also exhibited well stability for the aqueous-phase hydrogenation of crude biopolyols without deactivation in five times run.

We present performance studies of an earth air tunnel cum greenhouse technology in terms of instantaneous thermal efficiency. Analytical expressions have been obtained for heating/cooling conditions of a greenhouse. The results are in accordance with the experimental results obtained for the same system in Greece.

Abstract Rising penetrations of variable renewable generation in electric power systems can raise operational challenges. One is that renewables can increase the need for dispatchable generation with fast-ramping capabilities. This can be costly, because in many instances flexible generators can be more expensive than baseload units that have slower ramping capabilities. If ramping capacity is not available, renewable curtailment may be needed. An alternate solution to this need for ramping is to use energy storage. A question that this raises is how renewable and conventional generators and energy storage would interact in a market environment, and whether certain asset-ownership structures would result in more efficient coordination. To this end, this paper presents a multi-period market-equilibrium model of interactions between these different types of market agents. The impacts on renewable integration of conventional generators having limited ramping capabilities are studied through an illustrative case study. We also examine a variety of structures for the participation of energy storage in the market. We find that co-ownership and co-operation of renewable generators and energy storage brings about the best results from the perspective of alleviating market inefficiencies. Having energy storage directly controlled by the market operator or participating as an independent profit-maximizing firm is less efficient.