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Abstract Canada has numerous climatic and geographical regions and the Canadian housing stock (CHS) is diversified in terms of vintage, geometry, construction materials, envelope, occupancy, energy sources and heating, ventilation and air conditioning system and equipment. Therefore, strategies to achieve net zero energy (NZE) status with the current stock of houses need to be devised considering the unique characteristics of the housing stock, the economic conditions and energy mix available in each region. Identifying and assessing pathways for converting existing houses to NZE buildings at the housing stock level is a complex and multifaceted problem and requires extensive analysis on the impact of energy efficiency and renewable/alternative energy technology retrofits on the energy use and GHG emissions of households. A techno-economic analysis of retrofitting renewable/alternative energy technologies in the CHS to reduce energy consumption and GHG emissions was conducted to develop strategies to achieve or approach NZE status for Canadian houses. The results indicate that substantial energy savings and GHG emission reductions are techno-economically feasible for the CHS through careful selection of retrofit options. While achieving large scale conversion of existing houses to NZEB is not feasible, approaching NZE status is a realistic goal for a large percentage of Canadian houses.

Abstract The need for improved fuel economy, while meeting more stringent global vehicle emission standards, continues to grow with the increasing demand for environmental protection and rising fuel prices. A new generation of catalytic converters, designed and patented by Vida Fresh Air Corp., offers emissions reduction while improving fuel economy. In this design, a thin layer of insulating material is placed inside the ceramic honeycomb channels, creating a multi-chamber catalytic converter. The improvement in performance of the catalytic converter is attributed to the change in both the flow distribution and the controlled heat diffusion from the inner to the outer chambers. On engine performance tests have shown significant improvements in both fuel economy and emissions, however, the theory of operation of this design needs to be validated for potential design improvements to achieve an optimum performance. In this study both experimental and numerical investigations are carried out in order to understand the flow through the catalytic converter, using different monolith cell densities. A dynamically scaled-down model for a typical flow through catalytic converter was utilized for this study. Detailed experiments were conducted using hot air as the working fluid in order to evaluate the thermal and fluid flow characteristics of the new catalytic converter technology without the effect of chemical reactions. The measurements were performed at a Reynolds number of 43,000 with a free stream temperature of 177 °C. These conditions were selected in order to achieve thermal and hydraulic similarity to actual flow conditions for a typical catalytic converter. Numerical modelling of the flow through the setup under investigation was found to adequately replicate the experimental measurements for temperature, velocity and turbulence intensity within ±3%, ±5% and ±8% respectively. The use of a new design of the catalytic converter found to improve the thermal performance by 18% and the hydraulic performance by 5% without a significant increase of the pressure drop across the catalytic converter.

Deposits formation on heat transfer surfaces is one of the main problems associated to biomass co-combustion. It reduces plant efficiency and availability and increases maintenance costs. It is obvious that an increasing amount of low-temperature melting components in fuel ash accelerates and aggravates this process. Research is done to evaluate the validity of thermal analysis methods to characterise fusion of biomass and waste ashes. Laboratory ashes from a set of biomass and waste fuels are leached in successive steps. The original and the leached ashes are analysed by Thermo-Mechanical Analysis (TMA). Traces obtained from TMA show to be promising ash fingerprints to classify deposition tendencies. Additionally Simultaneous Thermal Analysis (STA) is performed on selected samples. Furthermore, improved chemical equilibrium calculations are proposed to predict the proportion of melted species resulting from combustion of biomass fuels. The model takes into account the reactivity of the inorganic matter in the fuel as issued from ash leaching.

Abstract This paper describes the development of generalized relationships for single- and two-phase intersubchannel turbulent mixing in vertical and horizontal flows, and lateral buoyancy drift in horizontal flows. The relationships for turbulent mixing, together with a recommended one for void drift, have been implemented in a subchannel thermalhydraulics code, and assessed using a range of data on enthalpy migration in vertical steam–water flows under BWR and PWR diabatic conditions. The intent of this assessment was to optimize these relationships to give the best agreement with the enthalpy migration data for vertical flows. The optimized turbulent mixing relationships were then used as a basis to benchmark a proposed buoyancy drift model to give the best predictions of void and enthalpy migration data in horizontal flows typical of PHWR CANDU 1 reactor operation under normal and off-normal conditions. Overall, the optimized turbulent mixing and buoyancy drift relationships have been found to predict the available data quite well, and generally better and more consistently than currently used models. This is expected to result in more accurate calculations of subchannel distributions of phasic flows, and hence, in improved predictions of critical heat flux (CHF).

Abstract Conversion of carbon contained in the solid residues (tars + biochar) derived from urban biomass gasification named herein TC would allow enhancing the yield of carbon species (CO/CO2) in synthetic gas. For this purpose, three low cost materials have been tested as possible catalysts: iron species (reduced Fe), bone meal (BM), and ashes (ash) recovered from biochar complete oxidation. The parametric study used the following as variables: air GHSV, onset of reaction temperature, reaction time to optimize CO/CO2 molar ratio and tar content in the produced gas. Results showed an autocatalytic effect of biochar leading to the catalytic conversion of approximately 78% of tars by the native metals contained in TC. The catalytic effect was further enhanced by adding Fe, BM, and extra ash. Addition of Fe catalyst resulted in significant heat generation (temperature increase of ca. 500 °C) and a twofold decrease in reaction time to consume all the carbon. Use of ash and BM as catalysts exhibit heat generation comparable to Fe, along with an improved reaction time, complete tars conversion and a CO/CO2 molar ratio to above 1.3 in the produced gas.

Abstract Natural gas hydrate sampling technology is an important means to study in situ properties. Currently, there are certain limitations in the application of pressure preservation technology, such as poor sealing and low success rates. Hole-bottom freezing sampling technology has the advantages of a simple structure, large sample size, and high fidelity. To solve the problem of low freezing efficiency, the quality of the cold source was controlled by changing the specific surface area of dry ice, ambient pressure, and temperature difference. The experimental results show that the improvement of heat transfer efficiency by the specific surface area and the temperature difference is mainly reflected in the cold source injection process. At the same time, it changes the viscosity of the cold source to make it easier to adhere, which will cause a large amount of dry ice loss and reduce freezing efficiency. The increase in ambient pressure will inhibit the sublimation of dry ice, reduce the heat transfer rate of phase change, and affect the freezing efficiency. Meanwhile, a solid layer will be formed and the cold source cannot be injected. According to the results, granular dry ice was selected to prepare a cold source with a temperature difference of 105K and ambient pressure of 0.1 MPa.

A number of forced gravity drainage experiments have been conducted using a wide range of the physical and operational parameters, wherein the type, length, and permeability of the porous medium as well as oil viscosity and injection rate were varied. Results indicate that an increase in the Bond number has a positive effect on oil recovery whereas the capillary number has an opposite effect. These trends were observed over a two-order of magnitude change in the value of the dimensionless groups. Furthermore, it was found that use of each number alone is insufficient to obtain a satisfactory correlation with recovery. A combined dimensionless group is proposed, which combines the effect of all the three forces. Recoveries from all the experiments conducted in this study show a very good correlation with the proposed group. The exponent of the Bond number in the proposed group is larger than the capillary number suggesting a larger importance for the former. We then show that the same group provides a good correlation for recovery from additional experiments conducted in this study (in the presence of connate water) with that of another set of experiments in the literature.

Abstract Reduction of iron oxide by biomass (a renewable energy) instead of fossil energy can greatly reduce greenhouse gas (carbon dioxide) emissions. In this work, the reduction characteristics and kinetics of iron oxide by lignin (a main component of biomass) were studied, aiming at efficient utilization of lignin as a renewable and highly reactive carbon substitute for coal. The reduction temperature range of iron oxide by lignin was found to be mainly 750–900 °C. It was also observed that the presence of iron could catalyze the pyrolysis of lignin, while the pyrolysis products of lignin promoted the reduction of iron oxide. An increase in the lignin-to-iron oxide mass ratio lowered the temperature at the maximum mass-loss rate determined by TGA. The activation energy varied, increasing first and then decreasing, while increasing the reaction fraction (α), with the turning point at α = 0.4. Compared with CO and coal, lignin appeared to be superior for reducing iron oxide, owing to the formation of nanometer-thickness carbon film in the process. The temperature at the maximum reduction rate was 134 °C for lignin, much lower than that of coal.

AbstractThe integration of solar energy systems into buildings via photovoltaic (PV) and other technologies can curb the amount of greenhouse gas emissions produced by buildings. However, the performance of solar energy systems is highly dependent on climatic and economic conditions. In this regard, the techno‐economic feasibility of building attached PV systems are studied for three scenarios considering three cities of Iran namely Tehran, Tabriz, and Kish Island, which have different climatic conditions. The result shows that the PV systems can annually meet 4.5–20% of the electricity needs for Tehran, 3.0–13% for Tabriz and 2.0–11.5% for Kish Island. Moreover, roof mounted PV systems were found to be a better alternative to envelope attached systems in technical and economic terms. The payback period for the solar energy systems was found to be between 8.7 and 14.3 years for Tehran, 14.2 and 22.6 years for Tabriz, and 11.6 and 21.1 for Kish Island.