• Energy Research
• other engineering and technologies close
• 13. Climate action close
• Hyper Article en Ligne close

Abstract This paper presents a comparative study of greenhouse gas emissions due to different wall compositions in accordance with their lifespans. The assessments carried out take into consideration the construction, maintenance and end of life of the walls, for a specific tropical climate site. The energy spent for heating and cooling during the utilization phase of the building was made equivalent for all calculations, in order to isolate the study on the evaluation of the performance of each technical solution. Initially, the methodology is described by choosing technical solutions to the building envelope, determining the corresponding service life for each solution and finding the corresponding GHG index from an appropriate database. Then, the evolution of this indicator is calculated within a given time for the four different technical solutions: Concrete Block; Solid Clay Brick; Cellular Concrete Block; Multicell Clay Brick. Brazilian national standard materials lifespans were adopted. A building lifespan of 150 years was considered. The results of this analysis suggest and quantify the important impact of the lifespans of both the materials and the building itself on greenhouse gas emission indicators. The numerical results presented point out the need to revisit the current life cycle analysis practices.

Abstract This article presents numerical simulations of the distribution of climate parameters within a ventilated tunnel tomato greenhouse during variable outside conditions. The simulations were performed using a computational fluid dynamics (CFD) code that solved the transport equations in a 3D domain, including the greenhouse and its crop stands, the surrounding ambient air and the soil located directly under the greenhouse. Radiative heat transfers were modeled using a bi-band discrete ordinates (DO) model, and the crop was considered to be a porous medium. Sensible and latent heat transfer between leaves and the surrounding air were determined based on the energy balance that included longwave and shortwave radiation fluxes in each crop control volume. The climatic boundary conditions were determined using experimental measurements, and the sun position was calculated for each time interval that was considered. The temperature distribution in the soil was determined based on a preliminary CFD determination of the conductive heat transfer in a 1D soil column. Simulations in the entire 3D domain were then performed, and 1 h time step and boundary conditions were updated prior to each calculation procedure. Results are presented for the spring equinox and summer solstice. These results highlight the combined influence of sun position, wind direction and intensity on the greenhouse microclimate and especially on the evapotranspiration rate of the crop at the leaf level. We discuss the possibility of using CFD code integration as a conceptual tool for designers or in association with a control climate model for farmers.

Abstract Concrete is the most widely used manmade material in the world with an annual production of about 10 billion tons globally. Its use outpaces that of historically important materials such as wood or stone in modern urbanism. Concrete is closely tied to the energy transition. As a structural material, concrete is used in multiple sectors, including energy. Because the concrete content of a power plant varies depending on the technology, the energy transition is expected to impact future demand for concrete. At the same time, concrete production is known to be highly polluting as one of its major components is cement, produced by an industry that is one of the main emitters of carbon dioxide worldwide. This dual aspect explains the aim of this study: understanding concrete (and therefore cement) demand under the energy transition policies described in the IEA’s 2017 Energy Transition Policy (ETP) report and quantifying CO2 emissions from cement production for the energy sector. Based on a simple model, the study is looks at global and regional levels to take into account potential local disparities. The results demonstrate that the decarbonization of the power sector will have a limited impact on global cement demand, but that it could be more challenging for some regions where the new power production mix would require large concrete structures. This model could be a useful decision-making tool in assessing the relative impact of any public energy transition scenarios on raw materials such as cement at the highest level of disaggregation, as well as enabling better sub-sectorial screening.

AbstractLimestone pore structure strongly influences dissolution and associated reactive transport. These effects are critical in limestone diagenesis and but also in engineering operations such as carbon capture and storage (CCS). However, detailed studies on how CO2‐enriched (acidic) brine changes this pore structure at relevant reservoir storage conditions are very limited. Thus, to provide further quantitative information and more fundamental understanding about these key processes, we studied the dissolution patterns of a homogeneous, a fractured, and a vuggy limestone when flooded with CO2‐saturated brine at representative storage conditions. The pore structured of these limestones showed drastically different responses to the acidic brine flood. As such, preferential channels surrounded by branched channels were formed in the homogeneous sample, while fractures became the main flow path in the fractured sample. In contrast, only one dominant channel formed in the vuggy sample, which resulted in a sharp permeability increase. These dissolution patterns reflect the associated Damköhler number, which significantly lower in the homogeneous, representing uniform dissolution. However, after injecting sufficient reactive fluid (1,000 PV), this uniform dissolution pattern transformed into a single preferential channel growth. Moreover, we conclude that increasing complexity of the pore geometry leads to more nonuniform dissolution. These dissolution patterns indicate the effect of initial pore structure on preferential channel growth and reaction transport. Our work provides key fundamental data for further quantifying limestone dissolution patterns in CCS, indicating that the CO2 injection may cause the reactivation of geological faults and damage around wellbore, thus aids in the implementation of industrial‐scale CCS.

In this paper, a newly developed heat and moisture transfer model for green envelopes is integrated in a transient building simulation program (TRNSYS) in order to investigate its dynamic performances coupled with a multizone building code. On the one hand we focus on the understanding of the coupled heat and mass transfers between green envelopes and the building; and on the other hand we study the model accuracy to assess the vegetation impacts together with building design. At first, the model reliability is verified through experimental comparisons during a summer period. Then, the developed simulation tool is used to assess the impacts of green walls on building energy performance. Since this model involves different hygrothermal transfer phenomena, the detailed numerical model results are analyzed to determine the weight of each phenomenon: evapotranspiration, shading effect and additional thermal resistance of green roof or wall. The results highlight the thermal benefits in summer and winter, especially for the west walls. The analysis of the different transfer mechanisms show that the foliage shading reduces the surface temperature variation whereas the evapotranspiration ensures the passive cooling when the water availability is sufficient.

4 p. In the last decade, a few papers have analysed the consequences of achieving the greenhouse gas concentration levels necessary to maintain global temperature increases below 2 degrees Celsius above preindustrial levels. Most models and scenarios assume that future trends in global GDP will be similar to the growth experienced in the past century, which would imply multiplying current output nineteen-fold in this century. However, natural resource and environmental constraints suggest that future global economic growth may not be so high. Furthermore, the environmental implications of such growth depend on how it is distributed across countries. This paper studies the implications on GHG abatement policies of different assumptions on global GDP growth and convergence levels. A partial equilibrium model (POLES) of the world´s energy system is used to provide detailed projections up to 2050 for the different regions of the world. The results suggest that while low stabilisation is technically feasible and economically viable for the world in all the scenarios considered, it is more likely to occur with more modest global growth. Convergence in living standards on the other hand places greater pressures in terms of the required reduction in emissions. In general we find that there are major differences between regions in terms of the size and the timing of abatement costs and economic impact.

Solar pyrolysis of pine sawdust, peach pit, grape stalk and grape marc was conducted in a lab-scale solar reactor for producing fuel gas from these agricultural and forestry by-products. For each type of biomass, whose lignocellulose components vary, the investigated parameters were the final temperature (in the range 800°C–2000 °C) and the heating rates (in the range 10–150 °C/s) under a constant sweep gas flow rate of 6 NL/min. The parameter influence on the pyrolysis product distribution and syngas composition was studied. The experimental results indicate that the gas yield generally increases with the temperature and heating rate for the various types of biomass residues, whereas the liquid yield progresses oppositely. Gas yield as high as 63.5wt% was obtained from pine sawdust pyrolyzed at a final temperature of 2000 °C and heating rate of 50 °C/s. This gas can be further utilized for power generation, heat or transportable fuel production.