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Abstract Carbon capture and storage has attracted attention as a feasible solution to global warming caused by anthropogenic emissions of greenhouse gases. The injection wells and well cement provide the wellbore integrity necessary for the long-term storage of carbon dioxide (CO 2 ). To date, ordinary Portland cement (OPC) has been used in injection wells, and its survival has been questioned as it is unstable in CO 2 -rich environments. Therefore, an experimental study was conducted to study geopolymer (G) as well cement and sandstone (S) as formation material. The sub- and super-critical CO 2 permeability of geopolymer, sandstone and G–S composites were studied using the high pressure triaxial set-up in the Department of Civil Engineering, Monash University. The undrained triaxial experiment was conducted at confining pressures from 14 to 26 MPa, and inlet pressures from 6 to 20 MPa to study the sub- and super-critical CO 2 permeability of wellbore materials. Based on the experimental results, the apparent CO 2 permeability of sandstone (0.8–30 μD) is approx. 1000 times higher than that of geopolymer (0.002–0.02 μD). The increase in pore pressure reduces the permeability of geopolymer, sandstone and G–S composite materials, and this is related to Klinkenberg's slip flow. In addition, the apparent permeability of CO 2 reduces due to pore volume shrinkage caused by the increase in confining pressure. The percentage permeability reduction (per 1 MPa increase in downstream pressure) of geopolymer, sandstone and G–S composite materials reduces with increase in pore pressure, and the reduction is significant from sub-critical to super-critical CO 2 pressure conditions. This observation shows the significance of super-critical CO 2 pressure conditions for effective and leak-free storage of CO 2 in deep underground reservoirs.

Abstract This paper uses an aggregate modelling approach to assess the impact of taxes on refined petroleum products on the Philippine economy. The effects of removing the 48% tax on premium and regular gasoline and the 24% tax on other refined petroleum products on prices and quantities are examined. For example, the consequences of a complete elimination of refined petroleum product taxes would be an increase in output by all producing sectors of about 3.7% or about 2.65 hundred billion Philippine pesos, a rise in the consumption of goods and services by about 13.6% or 4.2 hundred billion Philippine pesos, a rise in lower tax revenue for the government of 62.4% or 2.8 hundred billion Philippine pesos. When subjected to sensitivity analyses, the results are reasonably robust.

Abstract A statistical analysis of light water reactor power plant capital costs that uses a data base that is larger and of higher quality than that used in a previous study. The data span six years, and include virtually all U.S. LWR power plants presently in commercial operation. During this period average capital costs increased at the rate of about $140/k We (1978 dollars) per year, and average construction time increased at the rate of about 4 months per year. Significant economies of scale, either in construction time or capital cost, were not detected. Other findings were that plants built in the Northeast continued to show higher average costs than those in the rest of the country, the experience of the architect-engineer is a factor in reducing costs, and the costs of plants with cooling towers could not be distinguished from those without.

International audience

Abstract Selection of optimum process parameters is often regarded as an effective strategy for improving energy efficiency during computer numerical control (CNC) turning. Previous optimization methods are typically developed for specific machining configurations. To generalize the energy-aware parametric optimization for multiple machining configurations, we propose a two-stage knowledge-driven method by integrating data mining (DM) techniques and fuzzy logic theory. In the first stage, a modified association rule mining algorithm is developed to discover empirical knowledge, based on which a fuzzy inference engine is established to achieve preliminary optimization. In the second stage, with the knowledge obtained by investigating the effects of parameters on specific energy consumption covering a variety of configurations, an iterative fine-tuning is carried out to realize Pareto-optimization of turning parameters for minimizing specific energy consumption and processing time. The simulation results show that the method has a high potential for enhancing energy efficiency and time efficiency in turning system. Furthermore, compared with three heuristic optimization techniques, i.e. Genetic Algorithm, Ant Colony Algorithm and Particle Swarm Algorithm, the proposed method demonstrates certain superiority.

Abstract Earth-sheltered buildings use dramatically less energy than conventional designs, as is shown by a computer study of single and two storey residences. Various insulating techniques are discussed for windows, and for roofs, walls, and floors of earth-sheltered houses and for basements of conventional houses.

Abstract The reliability and availability considerations are introduced in the exergoeconomic investigation of a combined cycle power plant in which an organic Rankine cycle is employed to recover the waste heat from a GT-MHR (Gas Turbine Modular Helium Reactor) power plant. The SPECO (specific exergy costing) theory is employed to investigate the exergoeconomic performance of the system and assess the specific cost of the output power. For the reliability analysis, however, the SSM (state-space method) along with the probabilistic analysis of Markov processes is employed. After conducting a parametric analysis, the performance of the cycle is optimized with respect to the specific cost of output power, with and without reliability considerations. The effects of the system failure and repair rates are examined on the cost of power and availability of the combined cycle by the sensitivity analysis. The optimization results show that, the specific cost of output power for the combined cycle is around 12% lower than that for the stand alone GT-MHR. However, availability of the combined cycle is lower than that of the GT-MHR as the former has more components and a complicated system.

Abstract In this work, the possibility of steel slag as an effective and low-cost catalyst for the decomposition of biomass pyrolysis tar has been explored based on the high content of iron oxides for sustainable syngas production from biomass. By simple calcination treatment at 800 °C, the loose structure of the steel slag was formed with the main chemical composition of Fe2O3 and MgFe2O4. The steel slag exhibited good catalytic activity on the cracking of biomass pyrolysis tar, and even higher tar conversion efficiency can be obtained by reusing the steel slag, leading to the increase in syngas yield. The presence of additional steam can further promote the tar reforming reactions, leading to the significant increase in H2 and CO. At 800 °C, the tar conversion efficiency reached 94.1% with a high gas yield of 493.5 mL/g. The interaction between steel slag and reductive gases resulted in the reduction of iron oxides into Fe3O4, and more pores were formed for the spent steel slag, which can enhance the contact between active sites and reactants. These characteristics indicate that steel slag has the potential to be used as an efficient catalyst with excellent stability in the long-term biomass tar removal applications.

Abstract Ammonia–water mixtures have been used as working fluids in absorption–refrigeration cycles for several decades. Their use as multi-component working fluids for power cycles has been investigated recently. The thermodynamic properties required are known or may be calculated at elevated temperatures and pressures. We present a new method for these computations using Gibbs free energies and empirical equations for bubble and dew point temperature to calculate phase equilibria. Comparisons of calculated and experimental data show excellent agreement.