Nanotechnology is one of the frontier material techniques of today. Infact, it is an advanced material engineering. Nanotechnology could affect us all, beyond nanoparticles, critical length scales and nanotools. The word ‘nano’ is a Greek word which means ‘dwarf’ and mathematically, nano means size of order 10-9 meter. Nanotechnology has been emerged from the branch of science termed as “Nanoscience” which is defined as the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a bulk scale. Bulk materials (the ‘big’ pieces of materials we see around us) possess continuous (macroscopic) physical properties for e.g. the material (gold) at the nano scale can have properties (e.g. opti cal, mechanical and electrical) which are very different from (and even opposite to!) the properties the material has at the macro scale (bulk) as can be seen in figure 1.
Internationally, nanotechnology is defined as the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nanometer scale (The nanometer scale is conventionally defined as 1 to 100 nm). Therefore, nanoscience and nanotechnologies deal with clusters of atoms of 1 nm in at least one dimension. Further, the principles of classical physics are no longer applied for the nano scale materials, in fact, it has to adapt quantum mechanics. Nanostructured materials solids or semi-solids (e.g. hydrog els, liquid crystals) characterized by a nano-sized inner structure. They are defined as nano structured materials; the spatial order is at the nanoscale, which lies between the microscopic and the atomic scale. The size of the nanostructures and the scale order within them in the solid impacts the properties of a material. Examples of nanostructured materials are nanoporous, nanocrystalline, nanocomposite and hybrid materials.
Methods for fabricating nanomaterials can be generally subdivided into two groups: topdown meth ods and bottom-up methods as shown in figure 2. In the first case, nanomaterials are derived from a bulk substrate and obtained by the progressive removal of material, until the desired nanomaterial is obtained. A simple way to illustrate a top-down method is to think of carving a statue out of a large block of marble. Bottom-up methods work in the opposite direction, the nanomaterial, such as a nanocoating, is obtained starting from the atomic or molecular precursors and gradually assembling it until the desired structure is formed.
Problems faced by power system
As power system is broadly categorized in three pillars namely generation, transmission and distribution. Each plays a vital role in the socio-economic and technological development of every nation. The shortage of power has been a great barrier for commercial and domestic usage in many countries. Many countries are facing with acute electricity problems, which are hindering its development notwithstanding the availability of vast natural resources. Industries and household have tremendously engaged in using generating set, so as to cover for this short coming in power supply. Incomplete combustion of the fuel in generating set leads to production of carbon monoxide, which is emitted to the atmosphere; these increase the amount of greenhouse gases, which are linked to climate change and global warming.
(i) Generation
Electricity generation faces the following challenges: Inadequate generation availability, inadequate and delayed maintenance of facilities, insufficient funding of power stations, obsolete equipment, tools, safety facilities and operational vehicles, inadequate and obsolete communication equipment, lack of exploration to tap all sources of energy from the available resources and low staff morale. As per the generation is concerned, fossil fuels are getting limited, emphasis have been shifted to renewable sources like solar, wind, geothermal, hydro, etc. That to solar energy is in great demand due to the abundant sun energy that can be converted to electricity for generation. One such technology used with the help of solar cells which are called photovoltaic cells. These cells are made out of semiconducting material, usually silicon. When light hits the cells, they absorb energy though photons. This absorbed energy knocks out electrons in the silicon, allowing them to flow. By adding different impurities to the silicon such as phosphorus or boron, an electric field can be established. This electric field acts as a diode, because it only allows electrons to flow in one direction. Consequently, the end result is a current of electrons, better known to us as electricity.
Conventional solar cells have two main drawbacks: they can only achieve efficiencies around ten percent and they are expensive to manufacture. The first drawback / inefficiency, is almost unavoidable with silicon cells. This is because the incoming photons, or light, must have the right energy, called the band gap energy, to knock out an electron. If the photon has less energy than the band gap energy then it will pass through. But if it has more energy than the band gap, then that extra energy will be wasted as heat. Second drawback is they are expensive to manufacture.
(ii) Transmission & Distribution
Copper / aluminum conductors used in transmission and distribution are having less electrical conductivity, less flexibility, less elasticity and weak tensile strength. These factors are mainly responsible for the poor performing of current overhead power lines. These wires have the heating losses which degrade the efficiency of power carrying capability to the load centers.
Power transformers have service lives that exceed 25-50 years, but when they fail prematurely, the result is often a dangerous explosion. Monitoring the condition of these transformers is critical to maintain the nation’s energy infrastructure. Further, the use of transformer oil for high voltage insulation and power apparatus cooling is also a problem with both its dielectric and thermal characteristics. Presence of particulate matter in the transformer oil leads to decrease in the breakdown strength.
High voltage ceramic insulators which are integral part of the power system suffer from the problem of environment contamination and thus, prematurely fail due to surface flashover phenomenon.
(iii) Energy Storage
Substation batteries are important for loadleveling peak shaving, providing uninterruptible supplies of electricity to power substation switchgear and for starting backup power systems. Smaller and more efficient batteries will reduce the footprints of substations and possibly the number of substations within a ROW.
The ability to store energy locally can reduce the amount of electricity that needs to be transmitted over power lines to meet peak demands. Energy storage allow downsizing of base load capacity and is a prerequisite for increasing the penetration of renewable and distributed generation technologies such as wind turbines at reasonable economic and environmental costs. Suitable energy storage is critical to the increased use of renewable energies, particularly, solar and wind. However, the storage capacity of battery is limited and takes more time for charging thereby, reducing the overall efficiency.
Remedial measures through nanotechnology
(i) Nanotech Solar cell for electricity generation
Nanotech solar cell is unique both for its energy efficiency and cost effectiveness. It is used in a printing process to deposit a thin-film, copper indium gallium diselenide CIGS-based PV semiconductor to create an efficient, durable solar cell. This semiconductor was 100 times thinner than a silicon wafer and the printing process is 10 times faster than the conventional thin-film process of high-vacuum deposition. The uses of copper indium gallium diselenide-based PV thin-films had reached sunlight-to-electricity conversion efficiencies of about 19.9 percent in laboratory tests. This is far superior to other thinfilm technologies and even better than most crystalline silicon technologies, using monocrystalline silicon, is able to convert the most sunlight into electricity, about 20 percent per panel, but the cost of the silicon was much greater than that of thin-film cells.
Less costly quantum dot (nano crystal) technologies are also making important contributions to improving the efficiency of solar energy systems. Examples of some of these potential nanotechnology-enabled improvements are highlighted below:
High-performance semiconductor nano crystals (nano dots) that are active over the entire visible spectrum and into the nearinfrared have been combined with conductive polymers to create ultrahigh-performance solar cells. The solar cells have improved efficiencies because the nano crystals harvest a greater portion of the energy spectrum. Solar roofing tiles using quantum dots that are based on metal nanoparticles are expected to be commercialized within the next several years.
Highly ordered nano tube arrays have demonstrated remarkable properties when used in solar cells. Researchers explain that the nano tube arrays provide excellent pathways for electron percolation, acting as “electron highways” for directing the photogenerated electrons to locations where they can do useful work. Research results suggest that highly efficient solar cells could be made simply by increasing the length of the nano tube arrays.
(ii) Nanotech Transmission Nanotechnology will help to improve the efficiency of electricity transmission wires. There are numerous nano-materials and other nanorelated applications relevant to electricity transmission. Aluminium conductor steel reinforced (ACSR) wire is the standard overhead conductor against which alternatives are compared. Carbon nanotubes are one such nanomaterial which has potential to impact the energy transmission system. A carbon nanotube (CNT) is a type of fullerene (carbon-only) molecule (Fig. 3) that is formed when atoms of carbon link together into tubular shapes. A special type of single walled CNT named as armchair Carbon Nano Tubes (CNTs) exhibits extremely high electrical conductivity (more than 10 times greater than copper) and also possessing flexibility, elasticity, and tremendous tensile strength, have the potential, when woven into wires and cables, to provide electricity transmission lines with substantially improved performance over current power lines.
Also, the current wires can be replaced with nano-scale transmission wires, called quantum wires (QWs) or armchair QWs, which can revolutionize the electrical grid. The electrical conductivity of QW is higher than that of copper at one-sixth the weight and QW is twice as strong as steel. A grid made up of such transmission wires would have no line losses or resistance, because the electrons would be forced lengthwise through the tube and could not escape out at other angles. Grid properties would be resistant to temperature changes and would have minimal or no sag. Reduced sag would allow towers to be placed farther apart, reducing footprint and attendant construction and maintenance impacts.
(iii) Other Electrical Transmission & Distribution Infrastructure
Nanotechnology applications will help to improve other components of the electric transmission infrastructure, thereby potentially reducing environmental impacts. The examples below pertain to transformers, substations and sensors.
a. Transformers: The widespread use of transformer oil for high voltage insulation and power apparatus cooling has led to extensive research work aimed at enhancing both its dielectric and thermal characteristics. A particularly innovative example of such work is the development of dielectric nanofluids (NFs). These materials are manufactured by adding nanoparticles suspensions to transformer oil, with the aim of enhancing some of the oil’s insulating and thermal characteristics. Fluids containing nano-materials could provide more efficient coolants in transformers, possibly reducing the footprints or even the number of transformers. Nano-particles increase heat transfer and solid nano-particles conduct heat better than liquid. Nano-particles stay suspended in liquids longer than larger particles and they have a much greater surface area, where heat transfer takes place easily. Using nano-particles in the development of High Temperature Superconductors (HTS), transformers could result in compact units with no flammable liquids, which could help increase it flexibility.
Researchers have investigated transformer oil-based NFs using magnetite nanoparticles from ferrofluids. The research showed that a transformer oil-based magnetic NF could be used to enhance the cooling of a power transformer’s core. Electrical breakdown testing of magnetite NF found that for positive streamers the breakdown voltage of the NFs was almost twice that of the base oils during lightning impulse tests. The lightning impulse of increased transformer oil breakdown strength with the addition of conducting nanoparticles for two common transformer oils (i.e., Univolt 60 and Nytro 10X).
Power transformers have service lives that exceed 25-50 years, but when they fail prematurely, the result is often a dangerous explosion. Monitoring the condition of these transformers is critical to maintaining the nation’s energy infrastructure. One of the most reliable ways to predict premature failure within a transformer is to monitor the levels of hydrogen gas in the insulating oil. As the oil deteriorates, hydrogen gas levels increase. Applied Nanotech Inc has created a palladium alloy nanoparticles sensor that is as small as a square millimeter. This sensor can offer continual monitoring of hydrogen in the oil at levels as small as 4 parts per million. The sensors can monitor increases in hydrogen levels as well, allowing utilities to monitor the pace of oil deterioration. The devices work by the expansion and contraction of the palladium allows within a dielectric substrate. The palladium allows act like switches, turning on as they expand when in contact with hydrogen. Because they only turn on when expanding, they consume no power under normal operation. Prior to the advent of these devices, oil deterioration and hydrogen levels had to be monitored with expensive and timeconsuming gas chromatography. Current research has expanded upon these properties to create thin film-hydrogen sensors. These new sensors could be vital to future transportation infrastructure once hydrogen is scalable as a store of energy.
b. Sensors: Nano-electronics have the potential to revolutionize sensors and power-control devices. Nanotechnologyenabled sensors would be self-calibrating and self-diagnosing. They could place trouble calls to technicians whenever problems were predicted or encountered. Such sensors could also allow for the remote monitoring of infrastructure on a real-time basis. Miniature sensors deployed throughout an entire transmission network could provide access to data and information previously unavailable. The real-time energized status of distribution feeders will speed outage restoration; phase balancing and line loss would be easier to manage. Also help to improve the overall operation of the distribution feeder network.
c. Insulators: Nanostructured hydrophobic coating can mitigate the problem of surface flashover phenomenon of high voltage insulators. It will not only increase the reliability but also increases the durability of the whole power system network.
(iv) Energy Storage
Nanotechnology plays a role in distributed generation and substation through the development of cost-effective energy storage batteries and capacitors.
a. Batteries: Carbon Nano Tubes (CNTs) have extraordinarily high surface areas, good electrical conductivity and has a linear geometry that makes their surface areas highly accessible to a battery’s electrolyte. These properties enable CNT-based electrodes in batteries to generate an increased electricity output as compared to traditional electrodes. This ability to increase the energy output from a given amount of material means not only that batteries could become more powerful, but also that smaller and lighter batteries could be developed for a wider range of applications.
The battery technology utilizes 25-nm nanostructured lithium titan ate spinet (a hard, glassy mineral) as the electrode material in the anode of a rechargeable lithium-ion battery, replacing the graphite electrode typically used in such batteries and contributing to performance and safety issues. The new battery offers vastly faster discharge and charge rates, meaning that the time to recharge the battery can be measured in minutes rather than in hours. The nano-structured materials also increase the useful lifetime of the battery by 10 to 20 times over current lithium batteries and provide battery performance over a broader range of temperatures than currently achievable, over 75% of normal power would be available at temperatures between −40°C and +67°C.
b. Supercapacitors: Characterized by fast charge and discharge capabilities over hundreds of thousands of cycles, supercapacitors serve in a wide range of commercial power storage applications, including light-rail regenerative breaking systems, load leveling in electric and hybrid electric vehicles, as well as in utility-scale power grids.
Applied Nanostructured Solutions (ANS) is set to enable supercapacitors with significant improvements in performance characteristics:
Up to 200 percent improvement in specific capacitance
Three-fold boost in high-rate capability
At least a 15 percent improvement in lowrate capability
Three- to four-fold enhancement of throughplane conductivity
ANS’s new technology can infuse substrates in a continuous, high-volume manner with highly crosslinked matrices of carbon nanostructures (CNS). The resulting paper-like CNS supercapacitor material works in both organic and aqueous solutions. ANS is now exploring commercial development with major power.
Conclusion
Nanotechnology holds a lot of promises in terms of potential applications and products for power system. Whatever the exact definition, key features in this field are:
• Combining different sciences and technologies
• Enhanced or new properties new applications all at very small dimensions.
Based on the information discussed in this paper, it is worthy of note that in order to tap into the nanotechnology solution to electricity generation, transmission, storage and distribution, basic requirement is to have the complete knowledge of power system, and according to the papers regarding nanotechnology appropriate solutions can be found to the problems facing in power system. The people should also be informed about the technology and possible adaptation to electricity generation. Further, we have sophisticated tools to build, characterize and utilize structures at the nanoscale, across a breadth of disciplines. Also, the researchers should work more on this new profitable technology that is useful in many facet of the economy.
