|
|
| Fig. 1: Carbon Nanotubes. (Source: Wikimedia Commons) |
Nanoscience is the result of interdisciplinary cooperation between physics, chemistry, biotechnology, material sciences and engineering toward studying assemblies of atoms and molecules. More than in other domains, nanotechnology requires the integration of many scientific, engineering and technical disciplines and competences and it can have huge impact on energy as it can be applied at every stage of the energy value chain.
Nanotechnology makes the conversion of primary energy sources more efficient and environmentally friendly. Producing electricity through the conversion of sunlight, known as solar photovoltaics, is a field where nanostructured materials and nanotechnology are contributing greatly. [1] The use of a layer of quantum dots which is the tiny blobs of one semiconductor grown on the surface of another, added behind the conventional multi-layer compound, is being investigated. [2] Also, thermoelectric energy conversion using nanostructured semiconductors helps to utilization of waste heat. A heat engine turns some of the flow of heat from a hotter body to a cooler body into useful work, and the maximum efficiency at which it can do so is the Carnot efficiency with assuming discharge to a reservoir at 25 degree celcius. The Carnot efficiency depends on the temperatures of both colder and hotter reservoirs and thus the efficiency at 523 degree celcius will be 63.8%. [3]
In practice, however, the Carnot limit doesn't apply even theoretically. For engineering convenience, the steam will be allowed to expand as nearly is entropically as possible, as part of a so-called Rankine cycle, and this expansion will do work by spinning the turbine blades. According to the research by NASA, the Rankine cycle is considerably less efficient than even the Carnot cycle and nanostructured semiconductors can actually help increasing this efficiency. The potential list of other ways that nanomaterials might help reduce sources from production processes is long. It is known that catalytic processes can be improved and made more selective via the use of particular kinds of nanomaterials and thus could potentially improve a whole series of production processes related to chemicals. Nanomaterials could start replacing the need for toxic heavy metals in some processes. [4]
Using nanotechnology in the manufacture of batteries offers numerous benefits. First, it reduces the possibility of batteries catching fire by providing less flammable electrode material. Also, mainly nanotechnology can increase the available power from a battery and decrease the time required to recharge a battery. [5] These benefits are achieved by coating the surface of an electrode with nanoparticles. This increases the surface area of the electrode thereby allowing more current to flow between the electrode and the chemicals inside the battery. This technique could increase the efficiency of hybrid vehicles by significantly reducing the weight of the batteries needed to provide adequate power. [2] Furthermore, using nanomaterials can increase the life of a battery by separating liquids in the battery from the solid electrodes when there is no draw on the battery. This separation prevents the low level discharge that occurs in a conventional battery, which increases the shelf life of the battery dramatically. [5]
Nanotechnology can help reduce the extreme losses experienced when power is distributed. The extraordinary electric conductivity of nanoparticles, such as carbon nanotubes (See Fig. 1), can be applied in the manufacture of electricity cables and power lines. Researchers in Stanford University are developing techniques to surround silicon nanoparticles with graphene cages. Researchers have also grown silicon nanowires on a stainless steel substrate and demonstrated that batteries using these anodes could have up to 10 times the power density of conventional lithium ion batteries. [5] These researchers found that while the silicon nanowires swell as lithium ions are absorbed during discharge of the battery and contract as the lithium ions leave during recharge of the battery the nanowires do not crack, unlike anodes that used bulk silicon.
There is every reason to believe that nanobased technologies offer real opportunities for helping to achieve positive environmental objectives through improvements in technologies that might help reduce our dependency on fossil fuels, such as fuel cells or solar cells. Developing a way to store energy-rich gases can help our energy systems. Metal organic frameworks are highly porous organic matrix substances that can store hydrogen or natural gas. The cubical nanostructures consist of an organometallic framework, whereas the interior of the cube contains numerous nanometer- size pores in an interconnected structure. [4] The nanopores have high surface area. These structures might also be used for energy sources for many devices, such as laptops. Tiny fuel cells could serve as a rechargeable storage medium. Furthermore, currently huge amounts of energy are used in the operation of lighting in our homes and workplaces. More efficient lighting technologies based on nanotechnologies would have enormous environmental benefits. It has been estimated, for example, that improving the efficiency of lighting in the United States by 10% would ultimately reduce carbon emissions by some 200 million tons per year. [4]
Nanotechnologies provide the potential to enhance energy efficiency across all branches of industry and to economically leverage renewable energy production through new technological solutions and optimized production technologies. In the long run, essential contributions to sustainable energy supply Energy Energy change distribution and the global climate protection policy will be achieved. Nanotechnological innovations are brought to bear on each part of the value-added chain in the energy sector. Within this broad arena, nanotechnologies are poised to play a significant and positive role.
© Dahee Chung. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] L. Goldman and C. Coussens, Implications of Nanotechnology for Environmental Health Research (National Academies Press, 2005).
[2] "Nanotechnology and Energy," Department of Science and Technology, Republic of South Africa, February 2011.
[3] J. V. Sengers, R. S. Basu, and J. M. H. Levelt Sengers, "Representative Equations for the Thermodynamic and Transport Properties of Fluids Near the Gas-Liquid Critical Point," U.S. National Aeronautics and Space Administration, May 1981.
[4] L. Zang, ed., Energy Efficiency and Renewable Energy Through Nanotechnology (Springer, 2011).
[5] S. Li, "Nanobattery Overview," Physics 240, Stanford University, Fall 2010.
