Advanced Materials and Smart Grid Technologies
Smart Grid Cabling and Novel Conducting Materials
SF6 Elimination and New Dielectrics
Power Electronics for the Smart Grid: New Devices and New Materials
Distributed Energy Storage Technologies
As the current generation of power grids approach the end of their useful life, public and private institutions are calling for the construction of new grids--a Smart Grid that incorporates new technologies to allow for affordable and efficient power supply and the integration of power generated from renewable energy sources. The vision of the Smart Grid, as defined by the U.S. Department of Energy in its Grid 2030 vision, is "a 21st century electric system that connects everyone to abundant, affordable, clean, efficient, and reliable electric power anytime, anywhere."
Meeting the many and varied expectations for Smart Grids in the next ten years will mean the development of new kinds of cable, cable dielectrics, power electronics, cable insulators, and energy storage devices. For this to happen, Smart Grids will have to utilize a variety of new materials ranging from gallium nitride to superconductors to carbon nanotubes. The task is even more urgent given that, according to many observers, investment in electricity grids has lagged in the U.S. and other nations, creating an urgency to upgrade.
Thus the opportunity being discussed here is more than just a response to what may be just hype; all the fuss over Smart Grids, some of which may be more politically motivated than motivated by real needs. As a result of both genuine needs and the massive capital expenditures that are expected to be made on Smart Grids in the next decade (especially in the U.S.), NanoMarkets expects to see unparalleled opportunities for manufacturers of advanced materials and specialized power devices and cables. These will help enable new grid architectures as well as enhance power system control and reliability, improve power quality and equipment lifetimes, and reduce costs.
Advances in material science have always been applied to the grid conceptually, but have historically not had much impact on grid development. A couple of decades ago, for example, superconductors were touted as likely to change the face of grid technology, but they didn't live up to their promise. It is often noted in the industry that Thomas Edison would have felt quite at home with today's grid technology and materials. And it is almost certainly the case that most managers and engineers who deal with electricity grids on a day to day basis think of it at the material level as being made up of "just wire," as one of them put it to us.
What has changed is that there is a new focus on advanced materials as an area of engineering that can produce business opportunity. This is often talked about in terms of the rise of "nanotechnology," although this designation is a bit crude in the sense that much more than "small tech" is involved. The new interest in advanced materials is a much larger trend than one that simply impacts the power industry, but it does potentially impact this industry in many different ways.
For now, we note only that, while in the past, improvements in materials and components for the grid would have been largely incremental, today's materials development is at a point that makes possible orders-of-magnitude improvements in performance. According to the U.S. Department of Energy's National Energy Technology Laboratory (NETL), achieving a next-generation power grid will require the development of several "critical" technologies. These include advanced conductors; high temperature superconducting materials and equipment; large- and small-scale electric storage devices; distributed sensors, smart controls, and distributed energy resources; and power electronics.
The most obvious way in which new materials can impact next-generation grids is through advances in conductive materials. By increasing conductivity it becomes possible to move toward an ideal where power is generated where it can be created at the lowest cost and then shipped to where it is most needed. Consider for example the scenario in which energy was generated cheaply in Nevada using solar thermal technology and then shipped--also at low cost--to Minnesota. This is still a long way from being a possibility at the present time, but would require cables made from new materials that would be incorporated into a Smart Grid to enable hundreds of Gigawatts of electricity to be shipped over thousands of miles.
There are (at least) three developments in advanced materials that are important in this context. Composite conductors are the most conventional of these and these are already in use throughout the existing grid. Composite cabling systems most often utilize aluminum and they are said to double amperage limits with little change in the requirements for line support or towers.
More revolutionary is the use of superconductors. As we have already noted, the first wave of interest in this area ended in disappointment. However, there is some limited use being made of 1G (first generation) superconductor wire in the power industry today; they are being used in short line segments as exits from congested substations or in urban areas and as fault current limiters. 2G superconductor wire and high-temperature superconductors (HTS) can be made in limited quantities today and have the kind of spectacular performance requirements that may be just what the Smart Grids of the future need. As an example of the renewed interest in HTS for Smart Grid applications, we cite the announcement in October 2009 by American Superconductor Corporation (AMSC) that its high-temperature superconductor wire have been chosen for the Tres Amigas Project. This is a "multi-mile, triangular electricity pathway capable of transferring and balancing many GigaWatts of renewable power between three power grids."
The third material that presents an opportunity for new levels of conductivity for the Smart Grid is carbon nanotube-based wires. The suggestion that carbon nanotubes could be used in this way was first made by the late Richard Smalley, and much of the work in this area is still being carried on at Smalley's old university, Rice University. According to researchers there, CNT wires "can theoretically conduct 100 million amps of current over thousands of miles without much loss in efficiency." This compares to today's wires, which conduct around 2,000 amps of current over hundreds of miles, with about 6 percent to 8 percent of the electricity lost in the form of heat. In a paper published in July 2009 in Nano Research, researchers at Rice University also described a method for making bundles of single-walled carbon nanotubes centimeters in length that could eventually yield CNTs of unlimited length. However, of the three developments in Smart-Grid-related conductive materials, CNT wires is by far the furthest from actual commercialization.
Dielectric materials are used primarily in the power grid for cable insulators (they are also used in capacitors). As with conductive materials, the expectation is that the evolution of the Smart Grid will produce a need for enhanced performance from dielectrics; that is better dielectrics will be needed to support the other changes in electricity grids that Smart Grids are expected to bring in their wake. However, in this case there is an environmental consideration as well, namely the need to replace sulfur hexafluoride (SF6). SF6 is an excellent dielectric that is widely used in high-voltage circuit breakers, switch boxes, and transmission lines. But it is also a major greenhouse gas. There is obviously a misfit between the Smart Grid concept as a way to improve the environment and the widespread use of a material said to promote unwelcome climate change.
In terms of performance, nanomaterials are likely, once again, to be important in the dielectric space. One much touted opportunity for nanotechnology in dielectrics can be found in the area of nanofillers. These are said to provide breakthrough performance in voltage endurance and breakdown strength. Nanocoatings could also enable improved dielectrics, although these will be used initially in combination with traditional fiberglass materials for insulators. The transition to exotic new conductors using superconductive and nanotube materials may well require entirely new forms of dielectrics; the current generation of dielectrics may be entirely inappropriate to their level of performance.
Much the same can be said of power electronics for the Smart Grid. Power electronics devices for the traditional grid--devices that include static VAR compensators, solid-state circuit breakers, and solid-state transformers--have been made using conventional silicon processes. Once again, there is a growing belief that these conventional devices do not have it in them to meet the requirements of the Smart Grid in terms of voltage, switching speed and thermal resilience.
This has created opportunities, both for power electronics devices made out of new materials and for new kinds of power electronics devices. As far as the new materials are concerned, the two that are at or near commercialization are silicon carbide and gallium nitride. These potentially provide significantly higher breakdown strength, lower switching losses and higher tolerance of high junction temperatures than silicon. Other materials that have been touted for next-generation grid power electronics include zinc oxide and even diamond. In a separate but related development, a new generation of power electronics devices are also appearing that will make electricity control processes in the Smart Grid easier to manage and more efficient. These include in particular unified power flow controllers, solid-state transfer switches and dynamic brakes.
Another interesting class of device--AC/DC inverters--represents, of course, an entirely mature technology in its current form. However, new and improved materials are expected to bring these inverters to a point where large areas in Smart Grids may be able to operate using DC.
Distributed energy storage is a key part of the Smart Grid concept, enabling improved efficiency of the grid as a whole as well as better load-leveling and backup for emergencies and grid outages. In addition, high-quality energy storage is a key requirement associated with alternative energy sources, because these newer sources of energy are intermittent in nature; photovoltaics produce no energy at night, for example.
In theory, almost any kind of conventional battery system can be used in Smart Grids, but new storage technologies are now appearing that are aimed specifically at the Smart Grid market. Areas where these new technologies are appearing include pumped hydro, compressed air, flywheel, chemical storage, ultracapacitor and superconducting magnetic. However, NanoMarkets believes that the most exciting opportunities in Smart Grid storage will come from materials and systems applications of chemical batteries and ultracapacitors.
Chemical batteries and ultracapacitors offer a compelling value proposition compared to other solutions as they are the most economical solutions for electrical storage and are not limited to certain geographical locations. They also have an extremely small carbon footprint, and offer significant potential applications today as well as a roadmap to deeper market penetration as materials improvements and manufacturing improvements/cost reductions evolve over the next decade.
Smart grid storage can be categorized into short-term storage for load leveling and quality uses (less than a minute) and longer-term storage for peak shaving/load shifting applications (storage for minutes or hours). Ultracapacitors are well suited to load leveling and quality applications as they have an extremely fast discharge and charging response, have a high current capacity and can be cycled hundreds of thousands of times without degradation to their storage ability. Chemical batteries are ideal candidates for peak shaving applications as they have higher energy densities and in many cases long service lifetimes.
Source: Smart Grid Sparks Opportunities for Advanced Materials
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