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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.

AbstractThe densities of CO2-deionized water were investigated by a magnetic suspension balance (MSB) at the practical conditions of CO2 geologic sequestration with pressures range from 10 to 18MPa, temperatures from 333.15 to 413.15K, and C02 mole fractions up to 0.0126 according to the solubility of CO2 in water. The experimental results of CO2-free deionized water and C02-deionized water with different CO2 mole fractions revealed that the density of deionized water in contact with C02 is higher than that of pure water. The density of the CO2 aqueous solution increases with increasing pressure and CO2 concentration almost linearly, while decreases with increasing temperature. And the slope of the density curves is almost the same for different concentrations at the same temperature within experimental error. The slope of the density versus CO2 mole fraction decreases from 0.442 to 0.257 as the temperature increases from 333.15 to 413.15K. The slope will be zero or negative value at about 510K for the system of CO2-water according to this trend. In other words, the density values of CO2- deionized water may be lower than C02-free deionized water at about 510K. According to this trend, the mixture solution will migrate upward due to buoyancy-driven at about 510K, which is not benefit to CO2 geologic sequestration. Therefore, the density of CO2 aqueous solution has an important effect on the safety of CO2 sequestration. An empirical model for the densities of liquid CO2-deionized system was developed on the basis of measured densities. The average deviation (AD) between the model and the experimental data is 0.00001%, the maximum deviation is 0.018%. The empirical model could accurately represent the experimental data and be appropriate for assessing the CO2 geologic sequestration.

Abstract The introduction of a heat source water network system using heat from hot spring and drainage water for hot water supply in accommodation facilities in hot spring areas is expected to contribute to increased energy efficiency. In this study, the relationship between the temperature of the heat source water and the energy efficiency of heat pump water heaters introduced in hot spring facilities connected to a single-loop heat source water network was analyzed. The primary energy consumption of the heat source water network system was compared with that of a centralized heat supply system by conducting a dynamic simulation using Modelica in the Dymola environment. The yearly average coefficients of performance of the proposed heat source water network and centralized heat supply systems were estimated to be is 4.56 and 3.24, respectively. The seasonal performance of the proposed system was also investigated based on measurement data. In December, it was estimated that the heat source water network system would achieve a 17.6% reduction in primary energy consumption in comparison with the centralized heat supply system. However, in August, it was estimated that the primary energy consumption of the heat source water network system would be 8.9% higher than that of the centralized system.

AbstractIn this study, numerical simulations are conducted to predict the long-term behavior of CO2 injected into a deep saline aquifer composed of alternating sandstone and shale layers. We carried out a base-case simulation with a conceptual model broadly based on the geological structure underlying the Tokyo Bay area and sensitivity analyses of key parameters. The results show that alternating layers of moderate permeability and capillary pressure without a structural trapping also has considerable capacity of CO2 storage and seal.

AbstractThe field test of CO2-ECBM was carried during 2003 to 2007 in order to evaluate technical feasibility of injecting CO2 into the coal seam while producing CH4 at Yubari City, Hokkaido, Japan. It aims to resolve global warming and to develop a system for injection and sequestration of CO2 into coal seams. The targeted coal seam is located about 900 m below the surface. The absolute pressure at the bottom hole is approximately 15.5 MPa and the CO2 temperature is about 28 ∘C before the injecting into the coal seam. Thus, CO2 is injected in liquid phase to the coal seam and supercritical condition of CO2 has not been satisfied due to heat loss along the deep injection well. Replacements of usual tubing pipes with thermal insulated tubings were applied, however the temperature at the bottom hole was still lower than the CO2 critical temperature. The project had a problem about decreasing injection rate after starting injection CO2. It was evaluated by analysing the field test data that the maximu m decreasing ratio of the coal seam permeability was 0.065 and permeability around injection well was became 6 times larger than the original one. We assumed that its reason is caused with swelling of the coal seam around the injection well by liquid CO2 injection. Present study has focused on the keeping supercritical CO2 in the tubing because viscosity of supercritical CO2 that is 40% smaller than that of liquid CO2. The CO2 temperature has been successfully predicted in order to keep CO2 in supercritical condition from the surface to the bottom for various CO2 injection rates and electric heater power. The minimum injection rate has been presented in order to keep CO2 in the supercritical condition at the bottom hole of the injection tubing. Injected CO2 is expected to be super critical over 12 ton/day of injection rate without any heating in the tubing.