Evaluation framework for energy security is discussed in this paper. Today, consideration of four factors, energy security, economic efficiency, environment and safety, is required for research on future energy. With regard to energy security, evaluations tend to be qualitative since method to estimate the cost of energy security has not been established. Based on the assumption that the security risk is relaxed to an acceptable degree by the fuel stockpile, we propose the evaluation framework to estimate the cost of energy security from any energy mix. Utilizing this framework, present and future energy mix is studied. It is found that the configuration of thermal power assumed by 2030 to be almost the same configuration giving the minimum total cost when CO2 value reaches the range of $60-80/t-CO2. It is also suggested that it will be difficult for coal fired power generation to contribute to minimize the total cost including power generation, CO2 and energy security if CO2 value exceeds $160/t-CO2.
Sugarcane bagasse is one of the biomass wastes which have a high thermal value (HHV) when dried and can be converted into energy by physical, biological or thermochemical process. Carbonization behavior of sugarcane bagasse and heat transfer properties were studied with superheated steam and nitrogen gas. In the carbonization experiment, char yield, HHV and carbon losing rate of superheated steam showed the same trend as that of nitrogen heating at the treatment temperature between 491 and 702 K. It means that no special oxidation occurs in superheated steam carbonization and the pyrolysis by superheated steam was the same as nitrogen gas. In the heat transfer properties, temporal change in the sample temperature attained a good agreement between calculation and experiment for superheated steam and nitrogen gas. The sample temperature in superheated steam atmosphere reached the set carbonization temperature faster than that in the nitrogen atmosphere due to the superior heat transfer property of radiation in addition to heat convection. As described above, superheated steam carbonizes the sugarcane bagasse with no additional oxidation as well as nitrogen pyrolysis and has better heat transfer property than nitrogen heating, which leads to conclusion that superheated steam is one of the useful carbonization tools of biomass.
To understand the properties of coking coal and coke during carbonization process, changes in stacking structure of carbon and carbon aromaticity were estimated using the XRD and NMR measurement techniques for the different four kinds of coking coals thermally treated at various temperatures. In the XRD measurement, the comparison of the diffraction patterns of the coal samples with and without decalcification indicated the proposed method could successfully eliminate peaks from ash components in the diffraction patterns. After thermal treatment, the average number of stacking layers in all the samples increased around temperature of 400-500 °C and slightly decreased around 500-700 °C. In addition, the average number of stacking layers of each sample tended to be larger for sample with higher carbon content. In the 13C-NMR measurement, the carbon aromaticity became larger for higher thermal treatment temperature, and the order of the carbon aromaticity almost corresponded with that of coke contraction ratio.
Number average molecular weight (Mn) of saturates (CL), which recovered from Cold Lake oil sand bitumen by column chromatography (JPI-5S-22-83), was estimated from a chromatogram obtained by gaschromatographic distillation (GCD, ASTM D 7169), and compared with Mn measured by cryoscopy and gel permeation chromatography (GPC). When Mn is estimated from a chromatogram obtained by GCD, the following conditions should be satisfied. The first, a chromatogram returns to baseline, and the second, the correlation between boiling point and molecular weight was known prior to the estimation. The second condition is filled with good linear correlations between the boiling points and the logarithm of the formula weights for alkanes and alkylbenzenes, respectively. For CL, the first condition was regarded to be filled because the chromatogram returns very close to the baseline. The Mn was estimated to be 400 using a calibration curve based on alkylbenzenes, because its H/C atomic ratio (1.78) was closer to alkylbenzenes than to alkanes. Cryoscopy is a more basic method for Mn measurement, because no calibrations are required. Here, the Mn was measured by cryoscopy using about 10 mL of p-Xylene solution with the concentrations of 17.2, 8.63, and 1.57 g/kg. As a result, Mn was calculated to be 370. In addition, a conventional gel permeation chromatography (GPC) method was performed, and the Mn was estimated to be 490. Comparing those three methods, GCD method is the most convenient when a sample meets the conditions described above. However, only saturate fraction can be applicable at a moment. Cryoscopy is applicable for any fractions in principle, but it requires relatively large sample amount (c.a. 150 mg), and it is available for a sample with Mn up to about 500. Mn obtained by GPC using polystyrene standards was most inaccurate among the methods described here. It is necessary to adopt new standards other than polystyrene for more reliable molecular weight measurement.
Although OTEC has good characteristics as a base load power supply, from view point of stability and resource amount, it has not been put to practical use because of its high power generation cost. In our previous paper1), the OTEC generation cost was shown to be reduced to 43.4 ￥/kWh, with 1.25 MW output capacity facility by optimizing the system with water intake and generation equipment. However, it is still much higher than the value, 5 - 10 ￥/kWh, of the coal fired power generation cost. It causes the difficulty of commercial application of OTEC system. The major factor of the high generation cost is low temperature of hightemperature side heat source. In this study, we conducted a conceptual design on the non-concentrating type solar heat collecting system as a low cost auxiliary equipment of the high-temperature side heat source in OTEC. We also optimized the total system by optimizing of the power generation equipment to fit to the temperature range, and estimated its power generation cost for larger scale system. By the calculated results with Kume island conditions, optimum high-temperature side temperature was 95 °C, and generation costs were 11.3 ￥/kWh for 10 MW, 7.0 ￥/kWh for 100 MW and 4.6 ￥/kWh for 1 GW output for each. These figures are comparable or even cheaper than the cost of other renewable systems, and it suggests the competitivity of OTEC to coal fired plant. Although this power generation system is a combination of the past technologies, we found that this kind of technology fusion among many fields in different industries remarkably contributes to the cost reduction with cost engineering and optimization. Additionally selecting the site blessed with solar radiation is expected to reduce the generation cost dramatically. Worldwide there are many sites suitable for this power generation method, suggesting that it will lead to full - commercialization of renewable energy as a base load power supply.