We are developing technologies for converting solar energy to electricity efficiently as well as converting carbon dioxide to useful fuels and/or materials by using green plants, microalgae, or artificial photosynthetic systems. We are also conducting research and development into clean coal technology and power generation using geothermal energy.

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 1000 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 convenience. NIRE is particularly concerned with chemical conversion processes. These are among the most effective conversion methods because the substances obtained (e.g. fuels) can be 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.

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 that 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.

The green algae, Botryococcus braunii, fix CO₂ using solar energy and produce abundant hydrocarbons. NIRE has studied continuous uptake rates by this microalga of inorganic nutrients such as phosphorus and nitrogen from 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.

Photosynthesis by living plants and some bacteria can be considered clean solar-energy conversion systems with high efficiency. The first step of biological 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 an algal photosystem 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 way.

A fusion of basic research and utilization technologies

Even now coal plays a primary role in the world energy supply, and there are expectations that it will continue to play an important role in view of its plentiful reserves and stable supply.

In addition to molecular-level elucidation of the structure of coal, which is a complex multicomponent system, and its interactions with solvents, we are working on new advances directed at fashioning innovative coal energy utilization technologies that take advantage of coal's structural characteristics and which are appropriate to the global environmental age. Our main efforts now are analyzing the chemical and physical structure of coal; evaluating the possibilities for practicalizing coal derived liquids; studying generating systems using completely demineralized coal (hypercoal); and conducting basic research on a hydrogasification method that optimizes reaction conditions based on the chemical structures of coal and char.

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.

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 are essential to control drilling operations and to reduce drilling costs, since maximum penetration rate and minimum trouble in wells can then be attained. NIRE is also developing polycrystalline diamond compact (PDC) bits.

NIRE is researching the development of methane hydrate as an energy source. Methane hydrate accumulations are known to exist in marine sediments around Japan. If successfully extracted and used at today's natural gas consumption rates, it is estimated that these deposits 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 methods for mining 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.