Abstract

In gasification and combustion processes of biomass, the adsorptive mass transport of relevant gases in the porous structure of particles is of most interest, since diffusion can be a limiting factor to the reaction rate during conversion. Therefore, this study presents an experimental data basis for the kinetic adsorption behavior of H2O vapor as one of the three main components in an oxyfuel atmosphere. Considering the implementation of diffusion and mass transport properties in char conversion modeling, a pore-structure dependent kinetic adsorption (PSK) model was previously developed based on kinetic adsorption measurements. After the successful validation using comprehensive kinetic adsorption data sets of O2 and CO2, this work provides new insights into the distinct adsorption behavior of H2O vapor in order to develop the PSK model even further.

Abstract

Conventional biogas-driven distributed energy systems concern the cascaded utilization of thermal energy; however, the chemical energy in the fuel is lost during the combustion process. To solve the problem, this paper designs a solar-and-biogas-fired CCHP integrated with chemically recuperated gas turbine, which is capable to make full use of both chemical and physical energy; also, the issues of high consumption of fossil fuel for biogas digester thermal insulation can be addressed by a novel combination of low concentration ratio of trough solar collectors. By performance comparison, the new design achieves a high net solar-to-electric efficiency of 19.71% which is higher than the optimal power efficiency (~16.00%) of a trough solar thermal power generation system. Besides, the new design can save 116.5 kg/h of natural gas (100%) compared with the conventional one. The new design broadens the possibility of the complementary use of multiple renewable energy sources.

Abstract

water distillation, solar chimney, solar chimney power plant, SCPP

Abstract

Despite numerous appeals, agreements and political measures, greenhouse gas emissions continue to rise worldwide. The increase of GDP is closely correlated with the increase in resources. Local currencies can be used instead to ensure sustainable cycles with a low carbon footprint. The research path goes into the daily routine of a real laboratory to find out which methods and incentives would be effective enough to deliver carbon savings. The climate bonus consists of a double mechanics of payment for the use of ecological goods and incentives to reduce them sparingly. As a result, after three years of the project, CO2-Memissions are clearly above expectations.

Abstract

Natural gas hydrate has attracted worldwide attention due to its huge reserves and clean combustion. The depressurization method is the most economical method to extract gas from hydrate. However, the mechanisms of heat transfer affecting hydrate decomposition rate during depressurization are still unclear. In this study, the gas production flux was controlled at 0.032 mol/min during depressurization, and three heat transfer conditions of hydrate deposit were used to decompose hydrate. The results show that the T-P responses of the thermodynamic system will be eventually parallel to the phase equilibrium line of hydrate during depressurization, which is not affected by the deposit heat transfer. After the deposit temperature is controlled by the thermodynamic properties of hydrate, the extra energy will be used to improve the hydrate decomposition rate under a good deposit heat transfer condition. Furthermore, ice formation during depressurization promotes hydrate decomposition, which hinders the decrease of the pressure and temperature of the deposit. Our findings reveal that the temperature of the thermodynamic system cannot be balanced by thermal energy and provide a new insight for the rate control of hydrate decomposition during depressurization from the perspective of deposit heat transfer.

Abstract

A two-dimensional, multiphase, non-isothermal model is utilized for the design of cathode catalyst layer polymer electrolyte membrane fuel cell (PEMFC) model coupled with a developed homogenous model which considers the catalyst layer (CCL) design parameters. The model is applied to predict the polarization curves for a variety of cathode compositions. It is found that increasing the radius of CCL influential particles including Pt and carbon particles, deteriorates the performance while increasing the ionomer weight percentage in CL enhances the performance of the cell.

Abstract

Seabed methane seepage is a ubiquitous phenomenon in deep-sea environments and on continental margins, affecting the ocean and global carbon cycle. As one of the world’s largest methane reservoirs, natural gas hydrate (NGH) is an important barrier for methane capture. However, the formation of hydrate shells on the surface of CH4 bubbles seeping into the water column may also assist in the migration of methane to the shallow sea and even into the atmosphere. Therefore, it is necessary to reveal the formation characteristics of hydrate film on the surface of CH4 bubble. In this work, the evolution of CH4 hydrate formation on a bubble surface and the dissolved CH4 concentration in the surrounding aqueous phase were simulated in different simulated ocean depth environments by using the suspended bubble method. The results showed that higher subcooling for hydrate formation leaded to smoother initial hydrate film, and the hydrate bubble was prone to flexible collapse due to faster gas consumption. In contrast, for dense and thick hydrate films, the occurrence of pressure difference between the internal and external of the film can lead to brittle collapse of the hydrate shell. The Raman measurement results basically corresponded to the morphological evolution phenomenon. In addition, it was found that the formation of hydrate film on the bubble surface weakened the mass transfer from the gas phase to the liquid phase, making the CH4 dissolution rate almost equivalent in different pressure environments. This work can provide important fundamentals for assessing the flux of methane leakage into shallow water in the marine environment.

Abstract

Wettability is a significant attribute in CO2 geosequestration and CO2 Enhanced Oil Recovery (CO2- EOR) operations, and affects the transport law, capture capacity, sealing capacity and leakage possibility of supercritical CO2 in tight sandstone reservoirs. However, the supercritical CO2-brine-rock reaction leads to wettability alteration of tight sandstone, and the mechanism remains unclear. In this paper, Zeta potential measurement, Fourier Transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used to characterize the surface properties of tight sandstone. Results show that with the increase of reaction time, the mineral composition of tight sandstone changes, the absolute value of zeta potential decreases, the electrostatic force decreases, but the content of hydrophilic uncharged groups increases, the van der Waals force and hydrogen bond force increase, and finally the hydrophilicity increases.

Abstract

We propose new Li2CO3-doped dark CaCO3 pellets. The solar full-spectrum absorption of the new pellets can be as high as 73.25%. After 60 cycles, the energy storage density of the new CaCO3 pellets is still as high as 1671 kJ/kg, and the decay rate of the energy storage density decreased from 56.73% to 4.24% compared with pure CaCO3 pellets. At the same temperature, the average decomposition rate of the new CaCO3 pellets in the first cycle is 2.1 times that of the ordinary dark CaCO3 pellets. Therefore, this new CaCO3 pellets can simultaneously achieve the characteristics of fast heat storage, excellent cyclic stability and high solar absorptance.

Abstract

A global performance analysis with weather conditions from 20 cities is conducted on a solar-driven indoor air carbon capture model to uncover the influence of solar irradiance and ambient temperature on the novel system’s carbon capture performance and cooling energy-saving performance. Results show that solar irradiance significantly affects collected CO2 mass while temperature affects energy-saving amounts. Specifically, for a 40 m^2×2.8 m room with 39 occupants, the proposed system can capture 37.2-41.03 kg CO2 per day and achieves an energy-saving performance between 23.95%-50.66% in different cities. This study sheds light on effectively and renewably capturing CO2 from indoor air worldwide.