Flywheel energy storage systems use the kinetic energy stored in a rotor; they are often referred to as mechanical batteries. On charging, the fywheel is accelerated, and on power generation, it is slowed. Because the energy stored is proportional to the square of the speed, very high speeds are used, typically 20,000–100,000 revolutions per minute (rpm). To minimize energy loss due to friction, the rotors are spun in a vacuum and use magnetic bearings. The rotors today are typically made of high-strength carbon composites. One of the main limits to fywheels is the strength of the material used for the rotor: the stronger the rotor, the faster it can be spun, and the more energy it can store.

The cleanliness of hydrogen and the efficiency of fuel cells taken together offer an appealing alternative to fossil fuels. Implementing hydrogen-powered fuel cells on a significant scale, however, requires major advances in hydrogen production, storage, and use. Splitting water renewably offers the most plentiful and climate-friendly source of hydrogen and can be achieved through electrolytic, photochemical, or biological means. Whereas presently available hydride compounds cannot easily satisfy the competing requirements for on-board storage of hydrogen for transportation, nanoscience offers promising new approaches to this challenge. Fuel cells offer potentially efficient production of electricity for transportation and grid distribution, if cost and performance challenges of components can be overcome. Hydrogen offers a variety of routes for achieving a transition to a mix of renewable fuels.

Catalysis is the essential technology for chemical transformation, including production of fuels from the fossil resources petroleum, natural gas, and coal. Typical catalysts for these conversions are robust porous solids incorporating metals, metal oxides, and/or metal sulfides. As efforts are stepping up to replace fossil fuels with biomass, new catalysts for the conversion of the components of biomass will be needed. Although the catalysts for biomass conversion might be substantially different from those used in the conversion of fossil feedstocks, the latter catalysts are a starting point in today's research. Major challenges lie ahead in the discovery of efficient biomass conversion catalysts, as well as in the discovery of catalysts for conversion of CO2 and possibly water into liquid fuels.

In many industrial countries, road transportation accounts for a significant portion of the country's energy consumption. In developing countries, the use of energy for transportation is on the rise. The recent increase in petroleum prices, expanding world economic prosperity, the probable peaking of conventional petroleum production in the coming decades, and concerns about global climate changes require efforts to increase the efficiency of the use of, and develop alternatives for, petroleum-based fuels used in road transportation. The energy efficiency of a vehicle could be improved in several ways: lightweighting the vehicle structure and powertrain using advanced materials and designs, improving the efficiency of the internal combustion engine, reducing tire rolling resistance, and hybridization. Each of these efforts will require improvements in materials and processes.

Aviation accounts for about 3% of the current global energy consumption of 15 terawatts (TW). The global annual growth of energy use in the aviation sector is likely to be around 2.15% and will exceed that in other transportation sectors, although land transport will continue to consume the largest amounts of fuel. Figure 1 displays the historical improvements in energy efficiency in the aviation sector. Fuel use is determined by both operational and technological factors. The former includes the passenger load factor, ground efficiencies, taxi procedures, take-off and landing paths and circuitry (actual distance traveled versus a great-circle distance), and changes in the mixture of old and new aircraft and propulsion systems with time. Technology factors, focusing on materials issues, are described in greater detail herein.

Materials advances could help to reduce the energy and environmental impacts of buildings. Globally, buildings use about 20% of primary energy and account for 20% of atmospheric emissions. Building energy consumption emanates from a variety of sources, some of which are related to the building envelope or fabric, some to the equipment in the building, and some to both. Opportunities for reducing energy use in buildings through innovative materials are therefore numerous, but there is no one system, component, or material whose improvement alone can solve the building energy problem. Many of the loads in a building are interactive, and this complicates cost/benefit analysis for new materials, components, and systems. Moreover, components and materials for buildings must meet stringent durability and cost/performance criteria to last the long service lifetimes of buildings and compete successfully in the marketplace.

The environmental sustainability of materials used in construction applications is driving a requirement for the quanti-fcation of performance attributes of such materials. For example, the European Union (EU) Energy Performance in Buildings Directive will give commercial buildings an energy rating when rented or sold. The Code for Sustainable Homes launched by the U.K. Government's Department for Communities and Local Government (CLG) in January 2007 sets out the requirement for all new homes to be carbonneutral by 2016. In addition, homes in the United Kingdom will need to signifcantly reduce water consumption from today's average 160 liters (1) per person per day to less than 801 per person per day. Similarly stringent targets are required for waste, materials, and other factors. Such environmental and energy standards are complementing characteristics such as strength, stiffness, durability, impact, cost, and expected life with factors such as “environmental profle,” “ecopoints” (a single unit measurement of environmental impact arising from a product throughout its lifecycle that is used in the United Kingdom), “carbon footprint” (amount of CO2 produced for the lifecycle of the item), “recycled content,” and “chain of custody” (a legal term that refers to the ability to guarantee the identity and integrity of a specimen from collection through to reporting of test results).

Sharp Corporation is making a concerted effort to reduce environmental impacts to the greatest extent possible at its production facilities around the world, and it is applying its own original evaluation criteria to recognize those plants having an extremely high level of environmental performance as “SuperGreen Factories.”

Our Kameyama plant, the frst such factory to be so recognized, is an integrated, start-to-fnish production facility for liquid-crystal display (LCD) televisions (TVs), from fabricating the LCD panel to assembling the fnished TV set (see Table I). Given that large amounts of energy are consumed to operate production equipment and to power air conditioning, we focused particular attention on environmental measures intended to reduce global warming and introduced an energy supply system that combines environmental friendliness and operational stability. As shown in Figure 1, this system is based on integrating different types of large-scale distributed power sources and consists of a gas-fred cogeneration system, a fuel cell system, and a photovoltaic power generating system. The power output of this system covers about one-third of the total electrical needs of the plant.

Electricity generation is the main source of energy-related greenhouse gas emissions and lighting uses one-fifth of its output. Solid-state lighting using light-emitting diodes (LEDs) is poised to reduce this value by at least 50%, so that lighting will then use less than one-tenth of all electricity generated. LED lighting will provide reductions of at least 10% in fuel consumption and carbon dioxide emissions from power stations within the next 5–10 years. Even greater reductions are likely on a 10–20-year timescale.

Nearly one-third of the world's energy consumption and 36% of its carbon dioxide (CO2) emissions are attributable to manufacturing industries. However, the adoption of advanced technologies already in commercial use could provide technical energy savings in industry of 27–41 exajoules (EJ), along with a reduction in CO2 emissions of 2.2–3.2 gigatonnes (Gt) per year, about 7–12% of today's global CO2 emissions. Even more significant savings can be attained on the supply side if fuel switching and CO2 capture and storage are considered. However, such changes must start in the coming decade to have a substantial impact by 2050.