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Technologies to Minimize Environmental Burden and Maximize Resource Utilization, Part I: New Energy Sources |
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We are developing technologies for converting solar energy to electricity by using photovoltaic cell, windmills as well as for fixing carbon dioxide as useful fuels and/or materials by using green plants, microalgae or artifical photosynthetic system. R & D for clean utilization of coal and for power generation using geothermal energies are being conducted.
Light from the sun has created an ideal environment for plants and animals
to live on Earth and supports the generation of energy from fossil fuels,
water, and wind. The amount of solar radiation reaching Earth is equivalent
to 180 million power stations operating at 1,000 megawatts (MW), although
the energy density is less. Therefore, enhancement of direct and indirect
utilization of this abundant energy source will be a key technology for
solving future energy and environmental problems.
Solar energy can be converted into other forms of energy for greater efficiency and convenience. NIRE is particularly concerned with chemical conversion processes. These are among the most effective conversion methods because the substances obtained (e.g., fuels) are conveniently stored, transported, and chemically modified. Since photochemical conversion of carbon dioxide (CO2), for example, will contribute to both utilization of solar energy and reduction of the greenhouse effect, NIRE is developing catalysts and other new materials necessary for this process.
[Global Warming Control Department]
Biomass is a general term for all organic matter, which includes not only crops, wood, and marine products, but also organic wastes such as sewage sludge. Biomass is the only renewable organic resource which fixes atmospheric CO2 by photosynthesis and does not break the CO2 balance on a global scale. As one of the most abundant resources, biomass is an attractive and environmentally compatible energy source.
1. Recovery of Hydrocarbon from Microalgae
Green algae, Botryococcus braunii, fix CO2 using solar energy and produce abundant hydrocarbons. NIRE has studied continuous uptake rates of inorganic nutrients such as phosphorus and nitrogen by this microalga in secondarily treated sewage. We have successfully obtained liquid fuel from algae cells by the process of thermochemical liquefaction. This process can also be applied to other forms of organic wastes, such as sewage sludge, which is liquefied at high pressure and temperature without a catalyst into oil that is nearly equivalent to "C-grade" heavy oil. This process can help environmental preservation.
[Global Warming Control Department]
2. Biological Production of Electricity
Photosynthesis by living plants and some bacteria can be considered a clean solar-energy conversion system with high efficiency. Light energy activates the biological photosystem. The first step of photosynthesis is absorption of this light energy by an organism, with subsequent photolysis of water, which generates high energy electrons and releases oxygen. These electrons are used to reduce carbon dioxide and produce carbohydrates.
NIRE has developed a technology to convert the excited electrons generated by alga photo system into electricity. This technology also allows conversion of electrons generated by oxidative degradation of carbohydrates accumulated within algal cells into electrical energy. The efficiency of this technology is higher than that of biomass incineration, since electrical energy is generated directly by conversion from plant cells, with no intermittent steps and resultant loss of energy along the path.
[Global Warming Control Department]
NIRE is developing an environmentally friendly system for coal utilization. Coal, widely distributed in deposits around the globe, including Japan, is expected to continue to play an important role as a global energy resource. Fluidization of coal, through processes such as liquefaction and gasification, can potentially expand coal utilization. At NIRE, research is being conducted to develop these processes and extend new coal utilization technology in environmentally friendly systems around the globe.
Advanced technologies, such as coal/oil co-processing, flash hydropyrolysis, ultra-fine coal liquefaction and chemical coal conversion, are being studied to develop a new coal conversion process for liquefaction. Published data about coal gasification plant operations around the world have been collected and entered into a data base. Using this data base, theoretical equations have been derived and evaluations of empirical data from the actual gasification process are now being performed: A fundamental study of the hydro-gasification process, which produces methane and BET surface area (BTX) from coal, is also being performed to determine the optimum gasification conditions based on the chemical structures of coal and char.
[Energy Resources Department]
Since geothermal power plants emit much less CO2 and other potential pollutants than fossil-fuel plants, geothermal energy is preferable as a "clean" energy source. It is estimated that 10% of the world's geothermal energy reserves are in Japan. Development and utilization of domestic geothermal energy is, therefore, thought to be an important means to resolve future energy and environmental problems. NIRE is conducting comprehensive research and development programs for unconventional and unused geothermal resources such as hot dry rock, high-temperature geothermal reservoirs in deep formations, very-high-temperature formations adjacent to magma, and magma itself.
[Mining and Geotechnology Departmen]
New Drilling Technique for Geothermal Wells
To develop geothermal resources, hot water and steam must be recovered from a reservoir by geothermal well drilling. The cost of geothermal well drilling may account for more than 50% of the total cost of geothermal resource development. Therefore, efficient and economical drilling techniques are desirable.
Methods for estimating rock strength and bit wear while drilling have been studied based on information such as bit weight, torque, and penetration rate. These methods will be polycrystalline diamond compact(PDC) bits. An incorporated into an automated drilling system is being designed to drill geothermal wells more efficiently. NIRE is also developing polycrystalline diamond compact (PDC) bits.
[Mining and Geotechnology Departmen]
Divelopments of Methane Hydrate
NIRE is researching the development of methane hydrate as an energy source. Methane hydrate accumulations are known to exist in marine sediments around Japan. It is estimated that these deposits, if successfully extracted and used at today's natural gas consumption rates, would serve us for the next 100 years.
Methane hydrate is a solid material composed of methane and water molecules. At low temperatures and high pressures (e.g., deep-ocean conditions), water molecules form a "cage" which entraps the methane molecule. Methane hydrate can be dissociated by increasing temperature and/or releasing pressure.
Fundamental research on the development of new mining methods for methane hydrate is currently underway at NIRE. Examples include a process control system of formation and dissociation of methane hydrate, fluid flow dynamics of dissociated gas and water in marine sediment, and disposal of CO2 by its substitution into methane hydrate.
Fig:Researches on the developments of methane hydrate
[Mining and Geotechnology Departmen]