Since electricity generated by wind power and other renewable sources fluctuates significantly, their extensive use requires energy storage technologies. This study analyzes life cycle CO2 emission (LCCO2) of power generation systems combining wind turbines with energy storage equipment, focusing on four types of hydrogen storage, i.e. compression hydrogen (cH), liquid hydrogen (LH), metal hydride (MH), and organic hydride (MCH) as well as three types of battery, i.e. lead-acid (PbA), redox flow (RF), and sodium-sulfur (NaS). In order to appropriately compare the two different types of system, the functional unit is defined to meet customers' demands of electricity and heat, because this study assumes that hydrogen is finally converted into electricity and heat using a fuel cell at consumption sites. The analysis revealed that, in general, LCCO2 of battery systems is smaller than that of hydrogen storage systems, not depending on characteristics of customers (e. g. heat-to-power ratios, load curves) and the patterns of wind power, when wind turbines are away from consumption sites. However, when wind turbines are located at consumption sites, LCCO2 of cH and MH systems is almost equivalent to that of battery systems for a customer who has a relatively large heat demand such as a factory, hotel and hospital.
This was a study to pursue new sustainable sources of power in Malawi and other developing countries of Sub-Saharan Africa by investigating a novel approach for biodiesel production via ethanolysis of pretreated oil feedstock with calcium hydroxide using thermal pretreatment with glycerol. 0.5 g of Groundnut (Arachis hypogaea) oil feedstock premixed with glycerol and Ca(OH)2 was thermally pretreated at 100 °C and stirred at 1000 rpm for 1-3 h. The triglycerides (TG) decomposed into diglycerides (DG) and monoglycerides (MG), which are reactive intermediates of the ethanolysis. This effect of pretreatment was investigated in comparison with the effect of other catalyst. Then, the pretreated oil was reacted under the following conditions: 100 °C, 12-to-1 ethanol (EtOH)-to-oil molar ratio, stirring at 1000 rpm, catalyst load of 2 wt%, time from 0.5-2 h. Thermal pretreatment with glycerol achieved a significant fatty acid ethyl ester (FAEE) yield of 76 wt% (comparable to the yields obtained with calcium oxide (h-CaO) and surface-modified calcium oxide (s-CaO)). In tests on the reuse of the Ca(OH)2 catalyst in repeated reactions, the yield did not decrease sharply with repetitive use. Given that all of the materials tested in our experiments are available renewably in Sub-Saharan Africa, we believe that biodiesel production via ethanolysis has the potential to provide a sustainable source of power in that region.
China has already become the second largest oil consumption country following the United States in the world. Furthermore the Chinese oil demand keeps increasing at the annual growth rate larger than ten %. The oil import dependence of China is forecasted to be 64.5% in 2020. It will be inevitable that China with rapid increase in demand and Japan with about 100% import rate of crude oil become competitors in energy secure field, especially oil. However, the future cooperation is expected in the areas of conservation of energy, new energy development and energy related environmental conservation. Because the energy related technologies such as desulfurization in the coal and oil combustion/conversion, coal liquefaction, energy conservation in the mining and manufacturing, traffic transportation and construction areas, the reduction of carbon dioxide emission, new and atomic energy development and so on are advanced fields of Japan and the related technologies and know-how are accumulated in Japan, not only the simple technology transfer to China, but also business opportunity for a Japanese enterprise will increase through cooperation in the above areas.