• Energy Research
• 11. Sustainability close
• 6. Clean water close
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AbstractA simple experiment for capillary sealed trap shows that leakage would occur only from the weakest point in the trap. As an extens ion of this concept, the sequestrated and accumulated CO2 in the structural high may happen to leak from the unexpected weak point near the top of sealing layer. On the other hand, if CO2 were sequestrated into the flank of tilted aquifer, CO2 in separate phas e would migrate upward within aquifer with no CO2 leakage into the sealing layer above and leaving some residual amount behind. According to this concept, the best location for sequestration of CO2 could be the flank of the structure rather than the top.

Abstract To achieve the sustainability for green energy generation, carbon dioxide (CO2) has selected as a working fluid to run in Rankine cycle system. The high pressure and temperature state, supercritical CO2 drives turbine for electric energy generation with Rankine cycle, in which geothermal heat absorption by a newly designed heat pipe (thermosyphon) for the energy resource is introduced in detail. The heat pipe is installed for absorbing the low-temperature heat energy from the geothermal reservoir by using methanol as a working fluid. The design of heat pipe is based on a double pipe with the methanol pool at the geothermal reservoir side, and a CO2/methanol heat exchanger is set on another side of the pipe. Working fluid, methanol, absorbs heat from the geothermal reservoir (bottom side), then turns to be the gas phase, which flows upward to the CO2/methanol heat exchanger at the top end of the pipe. After the high-temperature gas phase methanol exchanges the heat with CO2, methanol is condensed and turned to the liquid phase, and flows downward through outer pipe by gravity force to the bottom reservoir. In this study, the analytical is conducted for the system performance in heat absorption and energy production. The basic model of heat pipe is constructed for the visualization experiment in view of flow characteristic. The results show the feasibility of utilization in low temperature geothermal reservoir by using methanol as working fluid in heat pipe. The heat from geothermal reservoir can be transferred to the surface by heat pipe with the efficiency of heat absorption being higher as 80 %. The geothermal heat pipe (with Rankine cycle system) can achieve the sustainable energy generation, that is not required to feed the water up to the surface to generate electric power compared with the ordinary geothermal power plant.

AbstractThe technical feasibility of CO2 storage in aquifers has been proven and demonstrated by the successful experiences in numerous EOR projects all over the world and the commercial practice in Sleipner. Previously, Tanaka et al (1995) had estimated the aquifer storage capacities as 91.5 Gt- CO2 in Japan. Research Institute of Innovative Technology for the Earth (RITE) in cooperation with Engineering Advancement Association of Japan (ENAA) conducted the estimation of CO2 storage potential in Japan which was one of the main objectives of this national research funded by the Ministry of Economy, Trade and Industry of Japan (METI). The revision research included storage categories, calculation methods and re-estimated geological storage capacities in Japan. The CO2 aquifer storage potential was estimated as totally 146 Gt- CO2 in Japan.

AbstractThe hydrothermal treatment (HT) has demonstrated the ability to improve fuel characteristics of biomass. On the other hand, the liquid by-product, which potentially contains solubilized nutrient, is being poorly utilized. This paper presents an investigation on HT of empty fruit bunch (EFB) on both solid and liquid product characteristics. In this work, the effects of HT on EFB were investigated at the HT temperatures of 100, 150, 180 and 220°C with the holding time of 30minutes. The results showed that HT can increase the carbon content, remove up to 55% of ash content from EFB, lowering the potassium and chlorine contents down to 0.84% and 0.18%, respectively. Moreover, maximum of 37% of nitrogen, 65% of potassium and less than 10% of phosphorus in EFB were dissolved into the liquid product which positively correlated with the HT temperature. These results demonstrate the possibility of employing HT for producing solid fuel as well as nutrient recovery from EFB.

Abstract This study develops an approach for optimizing the size/scale of microgrids used in electricity sharing around each residence by considering the uncertainty between the electricity supply from photovoltaics and electricity demand. Uncertainties are quantified using simulations that consider actual daily variations in supply and demand. The developed approach is applied to microgrid optimization in Sumida-ku, Tokyo, Japan, and results suggests that large-scale microgrids are required in central districts but small microgrids are sufficient in old residential areas. Results also show the statistically significant effect of optimizing microgrids to enhance energy self-sufficiency.

Abstract As a representation of smart and green city development, bike-sharing system is one of the hottest topic in the fields of transportation, public health, urban planning, and so on. With the development of Mobility as a Service (MaaS), emerging technologies such as mobile data mining give some new solutions for optimizing bike-sharing system and predicting the emission reduction. Here, we propose a bike-sharing layout optimization and emission reduction potential analysis structure under the concept of MaaS. A human travel mode detection method and a geometry-based probability model are proposed to support the particle swarm optimization process. We implement a comparison study to analyze the computational efficiency. Taking Setagaya ward, Tokyo as the study case with about 3 million GPS trajectories, the result shows that with the increase of station number from 30 to 90, the adoption of bike-sharing system can reduce about 3.1-3.8 thousand tonnes of CO2 emission.

Abstract In the current pursuit of eco-city development in China, energy efficient residential neighborhood development becomes one of the focuses. While current codes and practices have been paying attention to green building design, building energy is influenced by not only building design, but also complex urban form at a larger spatial scale, which was not well discussed. At the same time, neighborhood design is always regulated by residential zoning codes, which restrict the density measures for economic considerations and layout to ensure safety, privacy, fire prevention and sunlight. What neighborhood design can achieve high energy performance under those regulations becomes a critical question for urban design practices. This study explores three questions: How density influences residential building energy efficiency? How different building heights affects building energy? And how different neighborhood layouts impact the building energy? Those questions are examined by computational simulation experiments on parametric design scenarios in the case study of a hypothetical neighborhood in Shanghai. The comparisons of the simulation results suggest that density and energy performance has a complex relation with a threshold density that has the best performance, and building height and energy use have a segmented relation with the same density due to elevator design codes. The energy performance ranges with the same FAR and with the same number of floors show the great impact of the building height and limited influence of neighborhood layout on building energy use. The simulation results also suggest the optimal design with best energy performance with different density settings. The findings can inform urban designers and policy makers on more energy efficient residential neighborhood design under current zoning regulations.

AbstractThis study evaluates the potential environmental impacts of deployment of carbon capture and storage (CCS) for pulverized coal power plants in Japan by using LCA, focusing on selected environmental impact categories including global warming. The LIME (Life-cycle impact assessment method based on endpoint modeling) method is used to assess and compare the environmental impacts between three cases, a typical ultra-supercritical pulverized coal-fired power generation system (case 1) and two CCS systems, one comprised of CO2 capture with monoethanolamine (MEA) solvent, compression, seafloor pipeline transportation and below seafloor storage (case 2) and the other case was the same as case 2 except that CO2 transportation by ship was used (case 3). The life cycle GHG emissions for case 1 were 0.89 kg-CO2 (eq.)/kWh. GHG emissions for case 2 and case 3 were 20% and 29%, respectively, of emissions for case 1. However non-GHG emissions increased for case 2 and case 3, especially emissions of NH3 from the CO2 capture process and ethylene oxide from the MEA production process. The results for the 3 cases at the endpoint level, which estimated the damage on four safeguard subjects (human health, social asset, biodiversity and primary production), showed that for case 2 and 3, damage to biodiversity and primary productivity increase by 40% respectively caused by increased feed coal to meet energy consumption on CO2 capture process while the damage to human health decreased by approximately 60% due to the large reduction in CO2 emissions. The increased damage to social assets caused by NH3 emission and increased energy consumption due to CCS is similar with the reduction in damage due to reduction of CO2 emissions.