February 20, 2007

What Can Nano Do For You?

By: by Amethyst Cavallaro, Online Editor, Power Engineering


Most of us have heard of the mind-boggling things that nanotechnology can do to change how we live our lives -- it's being used to improve and invent new electronics, textiles, medical equipment and even food. But what can nano do for power generation? Researchers are discovering that seemingly endless possibilities exist in how nanotechnology can improve the way we make power.

Nanotechnology refers to materials on the atomic or molecular scale. It's the understanding and control of matter at dimensions of about 1 to 100 nanometers, where special properties enable unique applications. To give an idea of scale, a sheet of paper is about 100,000 nanometers thick, according to the National Nanotechnology Initiative, a federal R&D program.

Researchers can manipulate how atoms self-assemble to form stronger structures, resist erosion and corrosion, and result in lighter weight components. In turn, those attributes can be used to improve steam turbine blades, boiler tubing, solar panels, fuel cells and wind turbine blades to name just a few power applications.

Nanostructured Coatings
The National Energy Technology Laboratory (NETL) has announced a new research initiative to develop advanced metals with a special coating designed at the nano scale. Electric Power Research Institute (EPRI) will work with NETL and with its partners Southwest Research Institute, Foster Wheeler North America Corp. and Applied Films.

David Alman, NETL research group lead, explained that under high magnification, metals can be seen to be composed of grains, which are crystal structures in different orientations. Where the metal grain crystals come up in different orientations, a grain boundary affects the metal's properties. Most metals have their grain structures on a micrometer level. Nano-scale materials are metals that have their microstructures on a nanometer scale and, consequently, they have some unique mechanical properties.

Those characteristics include unique properties such as enhanced toughness, strength, erosion resistance and resistance to spallation, Alman said. The finer microstructure can also facilitate a faster diffusion of metals like chromium or aluminum to the coating's outer surface, improving corrosion resistance.

The research will focus on modeling solutions to the technological challenges associated with heating these special metals. A structural change occurs to the coatings when they are heated to high temperatures. The nanometer scale microstructure can thus revert to a micrometer scale microstructure. This will cause the benefits of the nanostructure to be lost.

Researchers are looking specifically at how to retain the nanostructured coating at elevated temperatures to engineer a superior product that can be used in a variety of coal-fired and other power plant settings.

Nano-engineered Materials
In mid-January, GE Global Research, the principal research organization of the General Electric Co., announced a breakthrough in nanotechnology that provides a direct pathway to making nanoceramic materials from polymeric precursors that retain their nanostructure up to 1,400 C.

"Nanostructure engineering in high temperature ceramics is extremely challenging because of the limited number of options available at the high temperatures usually needed to make these materials," said Dr. Julin Wan, who worked on the process as a part of a cross-disciplinary team.

Ceramics are an attractive material because they are extremely heat resistant. However their brittle structure prohibits their use in harsh environments. The research team developed a simple synthesis for the polymeric precursor, which enables an efficient path toward ordered non-oxide ceramic nanostructures. Non-oxide ceramics have increased toughness and retain their intrinsic heat-resistant properties. The unique aspect of the invention is that the desired composition and the ability to form ordered nanostructures are built in. No external template is needed and the process is said to be simple and robust.

GE said these nanoceramic materials could have broad applications for the company's gas turbine and other businesses in achieving new levels of efficiency, reliability and environmental performance.

Optimized Renewable Technologies
The Energy and Environmental Technology Applications Center (E2TAC) in the College of Nanoscale Science and Engineering at the University of Albany specializes in some interesting areas of renewable energy nanotechnology.

Expensive silicon-based materials have dominated the photovoltaic industry. E2TAC researchers are working to change the high cost of advanced solar cells by integrating nanocrystalline materials into thin film and polymeric materials.

Photovoltaic development is currently focused on three research areas: Copper-indium-galium-selenide (CIGS) based solar cells are flexible and achieve conversion efficiency of over 15 percent; Dye sensitized solar cells absorb solar light as it passes through an electrically conductive glass electrode. The dyes then emit an electron which is conducted away by titanium dioxide, converting solar energy into an electric current that passes through an external circuit.; And organic plastic solar cells achieve a 5 percent power conversion using composites of high aspect ratio single wall carbon nanotubes and semiconductor nanocrystals of cadmium-selenide in conjugated polymers.

In addition to solar, the E2TAC lab works on next generation fuel cells to improve electrodes, coatings and membrane electrode assemblies for PEM-based fuel cells. Research also focuses on cathodes with improved power density, enhanced durability and electrical conductivity for solid oxide fuel cells.

As wind blades grow larger, researchers have found efficiency improvements will slow or stop as weight increases with size. According Tom Ashwill, who leads Sandia's blade research efforts and who just completed the new STAR blade design, the current challenge in wind energy is to develop new concepts that reduce the rate of turbine weight growth. Wind energy stands to benefit from advances in composites that use nano-scale dispersion to make them lighter and more durable.

"Incorporating nanostructures into wind turbine blades as composite materials can enhance their mechanical strength considerably and allow these blades to be built with longer spans, increasing the power delivered from each wind turbine," said Pradeep Haldar, director of E2TAC.

Nanotechnology is a widespread technology that provides a platform to develop new materials, and power generation is one area of application. Advanced materials could result in reduced downtime, increased efficiency and a lower probability of major mechanical failures, saving utilities money and time. There's no doubt that a new horizon of technology breakthroughs awaits the power generation industry, and nanotechnology will play a big part in making it happen.