Metals Tech

A whispering gallery is an acoustic phenomenon that architects have used already centuries ago when building cathedrals. Sound waves travelling around the curved walls of a dome, such as the one in St. Paul’s Cathedral in London, allow a person standing near one part of the wall easily hears a faint sound originating at any other part of the wall.

Similarly, but much more recently, researchers have built whispering galleries for light, which are nowadays found in applications ranging from sensing, spectroscopy and communications to the generation of laser frequency combs or to boost the performance of solar cells.

Yet another – but nanoscale – electronic analogue of this classical wave effect has been created in graphene to act like a circular wall of mirrors for electrons in graphene. These whispering galleries for graphene electrons opens the way to building devices that focus and amplify electrons just as lenses focus light and resonators (like the body of a guitar) amplify sound.

In new work, reported in Applied Physics Letters (“Contactless exploration of graphene properties using millimeter wave response of WGM resonator”), a research team from O.Usikov Institute for Radiophysics and Electronics, Kharkiv, Ukraine and Institute of Bioelectronics (ICS-8), Forschungszentrum Jülich, Germany, report the experimental results of studying the response characteristics in a millimeter wave band whispering gallery mode sapphire resonator to single-layer graphene at different distances of graphene from the resonator.

Instead of whispering words (vibrations with a frequency range of 200-600 Hz), the scientists used this millimeter-sized whispering gallery to send out electromagnetic waves of rather large frequencies (about 40GHz) and excite the whispering gallery modes (WGM) in sapphire disks.

“Interestingly, we found that the evanescent field of the resonance system is extremely sensitive to the environment, surrounding materials and disk coatings,” Dr. Dmitry Kireev, one of the paper’s authors, tells Nanowerk. “A series of experiments showed that such WGM resonance can be used to detect the conductivity and thickness of the materials deposited on top and/or can even be used for advanced biosensing.”

In order to test the level of detection, the scientists decided to explore single-layer graphene material using the WGM technique.

The scientists found that the resonator system is indeed responsive to the presence of graphene. Moreover, resonance dumping is more pronounced when the graphene is in direct contact with the system and less pronounced when the graphene is slightly apart from the resonator.

“This confirms that parts of the resonance energy is absorbed by graphene,” explains Kireev. “A series of experiments confirmed that the contactless WGM resonant technique allows detecting the electrical conductivity of graphene with precision comparable to a standard DC conductivity measured through steady state electrical measurements.”

This means that the resonator technique can be used to reveal the conductivity/sheet resistance of graphene in the millimeter wave band in a contactless and noninvasive way.

Moreover, the demonstrated WGM resonator technique paves the way for contactless studies of other one-atom-thick materials in a wide range of wavelengths including sub-millimeter waves.

Utility operators face a rapidly changing operational and business climate due to increasing regulatory compliance requirements and demands for security. In addition, they need to be able to consolidate and manage the growing variety of information and communications that form the “central nervous system” of power delivery.

At the same time, utility operators must not only maintain, but also increase the reliability of the power delivery system. Utility operators also must plan for new operations such as the integration of renewable energy sources to meet legal and regulatory mandates. All of these challenges must be met in the extremely demanding physical environment of the power utility substation.

Regardless of geographic location, the strategy utility companies have been rapidly turning to is the “smart grid,” an intelligent communications infrastructure that can efficiently integrate all supply and demand elements connected to the electric grid.

The world’s most advanced companies and government agencies are now focused on using new technologies to create lasting change. The entire ecosystem – from power gen through transmission/distribution to end-user — can be made smarter, faster, more agile, resilient — and most importantly, more secure. New technologies that are now available, from generation to consumption, are enabling the electric grid to increasingly become all of the following:

• Observable – Full determination of grid state means deep situational awareness.
• Automated – Leveraging pervasive sensing the ability to automatically respond to conditions and events beyond traditional protection and controls will become mainstream allowing more refined control of an increasingly diverse and stochastic electric system.
• Intelligent – Global energy networks are increasingly evolving, and will continue to do over the coming years, in ways that help to enable a large diversity of energy supply and a more responsive load.
• Sophisticated – Analytics, coupled with advanced distributed control schemes, enable adaptive tele-protection and intelligent operational systems to manage inherently unstable systems.
• Transactive – As the Internet of Things converges with the electrification of everything, hundreds of millions of energy-smart devices can interact with energy markets, leading to trillions of microtransactions.

A growing number of utilities are investing in the creation of end-to-end, resilient, and secure communication infrastructures. The aim is to support and manage their smart grid deployments. European-based utilities are among those undertaking these moves.

Firstly, how to define “smart grid?” A smart grid exists wherever the electricity delivery system, from point of generation to point of consumption, is integrated with communications and information technology – and where it is delivering enhanced grid operations, better customer services, and positive environmental benefits.

For a smart grid to work well, it requires some key working elements that can be synchronized:

• Interoperability across multiple vendors.
• Protection of data & system integrity.
• Support for many types of media.
• Rapid collection and analysis of massive quantities of data.
• Connectivity to and from millions of devices.
• Rapid response to “bursty” event–related message data.
• Convergence of multiple existing networks.

A smart grid enhances both power distribution and power management by providing distributed intelligence — and enabling a measure of control. The end result is more cost-efficient delivery of power, based on true demand.

Smart meters are deployed precisely because they can provide the basis for real-time measurement of customer demand. Integrated networking technologies and security features bring that information securely onto the grid — forming a backhaul communication network.

Demand information, since it is so vital, is shared with the local utility, which in turn can leverage local generation sources (or power storage) to meet demand fluctuations. Operation analytics tools make it possible for these same utilities to better manage the network, and to integrate distributed generation sources.

Importantly, home automation controls and commercial facility automation can both be connected to this same network. They can be designed in such a way that they respond to demand management requests, which become especially important as the load on the grid increases.

As more granular information is shared between and among the local and primary utility operation centers, power generation needs can be more effectively managed – which results in reduced costs for electricity.

The sharing of demand and supply information among utility providers and with their data centers (ideally operated as a ‘federation’) allows decision-making to be distributed throughout the network. This provides resilience to attacks on the grid, and it enables a faster response to prevent outages.

Such deployments can utilize the network as the platform to intelligently bring together disparate sources of a smart-utility’s information.

Leveraging a broad set of technologies, solutions, services and partners, the smartest utilities empower smart grid initiatives with advanced communications networks. When executed well, the result is to create space for new business models and new operational models, enhancing physical security and cyber security, while providing energy consumers a wide range of benefits.

The reasons why different countries invest in smart grids are as varied as their national geographies and political systems are different:

United States – During the Obama years, the American Recovery and Revitalization Act (ARRA) provided for a total of $4.5B for smart grid initiatives. Of that, $3.9B was administered by the US Dept of Energy (DoE) for investment and research and development programs. The remaining $600M was for worker training and interoperability work undertaken by the US National Institute of Standards and Technologies (NIST). During the two Trump years the US Administration has dropped the ball, doing little in practical terms — although the words coming from the DOE have been favorably inclined towards smart grid.

China – The State Grid Corp of China (SGCC) has been deploying extensive fiber-optic networking throughout China high-voltage substations. This network now totals many millions of kilometers of fiber-optic channels. According to one SGCC spokesperson, there will be “a lot of business opportunities for smart grid relevant industries,” such as the firms supplying smart metering systems, power storage devices, telecommunication devices, and software.

Australia – The national government announced plans to invest large sums – in one instance committing hundreds of millions of dollars, in partnership with the energy sector, with all of it focused on developing a national energy efficiency initiative. This initiative supporting the installation of Australia’s first commercial-scale smart grid. The national government, along with some of the key state governments, now have a variety of programs underway – with millions of smart meters rolling out to homes and businesses.

During the 2019 calendar year, some national governments and regional agencies will act in ways that further the smart grid. The hope is that the rest of the world will follow their lead.

Industrial giant Siemens is the latest corporation to make moves in the blockchain space. The company has announced it intends to use the technology to bring innovation to the energy sector and give more power to the people – you know, the usual yet-to-be-proven decentralization rhetorics.

For the time being, the company is limiting its blockchain experiment to two divisions only: Energy Management and Power Generation Services. With this move, Siemens hopes to find new ways to store energy and develop a more efficient management system for energy networks.

“Siemens aims to proactively shape the future of blockchain-based, transactive energy applications, new prosumer-centric use cases as well as business models around operation of distributed energy systems, microgrids and financing,” the company said.

“Ultimately, block-chain-based [sic] applications and business models could help increase the overall efficiency of future energy networks and enable new forms of asset and project financing,” Siemens added.

Details around this particular use case remain scarce, but Siemens says the solution will be provided by a third-party blockchain developer Energy Web Foundation. According to a white paper published by Energy Web Foundation, the company is running a custom implementation of Ethereum.

The paper claims the solution is about 30 times more efficient than Ethereum itself, but chances are this efficiency comes at the cost of true centralization. Indeed, ignoring the pompous language, Energy Web Foundation’s white paper indicates the company is running yet another permissioned blockchain.

But considering all the regulatory uncertainty around blockchain, can you blame Siemens for opting for a more corporate-friendly solution?

As temperatures drop and winter looms, homeowners and property managers are sweeping chimneys, insulating pipes and swapping screens for storm windows.

They’re also going beyond traditional winterizing by installing smart thermostats and home energy monitors aiming to lower utility bills.

Smart thermostats — which let consumers adjust their home temperatures remotely using any internet-connected device — are among the most popular smart home technologies, generating $1.3 billion in sales globally in 2017, according to Navigant Research. Some models use geofencing technology and multiple sensors placed throughout the house to adjust temperatures in individual rooms when a resident walks in, maximizing comfort and efficiency.

Just how much consumers can save by installing smart thermostats — which generally range in price from $150 to $250 — depends on a variety of factors, but Nest, one of the most popular smart thermostat companies, estimates users can save $131 to $145 on their energy bills per year.

Customers can save more if their local utility offers rebates or discounts for allowing the utility to occasionally turn their thermostats up or down, as long as consumers are willing.

Many utilities are offering heavy discounts on smart thermostats in exchange for enrolling in so-called “demand response” programs, which let utilities periodically reduce customers’ electricity usage so they’re not demanding as much energy from the grid, said Dan Wroclawski of Consumer Reports.

“When you join a demand response program, you usually get some sort of rebates, and the best deals we saw were bill credits that happen annually,” Wroclawski said. “When you agree to these programs you are ceding some level of control. But if it’s bothering you — if you’re too cold or too hot — all you have to do is go up to the thermostat and turn it up or down and the demand response program will essentially just realize, ok, they’re ignoring us.”

Nationwide, nearly 1.4 million customers are enrolled in programs that allow utilities to turn their thermostats up or down, and more than 40 utilities with thermostat programs took advantage and adjusted customers’ temperatures about 8 times per year, according to the Smart Electric Power Alliance. But people sometimes opt out of the programs when, for example, it’s a very hot day and they don’t want their air conditioning turned down; and that’s the exact time utilities need people to stick with the program.

Some utilities have similar programs that allow them to temporarily turn off customers’ electric water heaters, and they find customers are less likely to opt out of those scenarios because they don’t really notice an impact.

Other utilities are offering “time of use” or hourly rate programs, which encourage customers to run dishwashers or other appliances at times of day when electricity rates are cheaper. In Illinois, where the two main utilities offer hourly rate programs, customers save about 15 percent off their utility bills per year, said Sarah Gulezian, senior manager of dynamic pricing programs at Elevate Energy. With the utility ComEd, 24,000 customers saved a combined $19 million over the past decade, and at Ameren, 12,000 customers saved more than $11 million, she said.

Customers don’t need a smart thermostat for the Illinois utilities’ programs, but they do need a smart meter, which is provided by the utility. They can adjust their home temperatures or appliance usage themselves when they get email or text alerts letting them know the electricity price is rising or falling. Such programs benefit low-income households that don’t necessarily have access to smart thermostats and whose electricity bills eat into a larger portion of their household income.

“From our research we’ve found that almost everyone can benefit from this,” Gulezian said. “By taking simple actions, you can help save on your electricity bill and have a positive impact on the environment as well.”

Being able to control electronic systems using light waves instead of voltage signals is the dream of physicists all over the world. The advantage is that electromagnetic light waves oscillate at petaherz frequency. This means that computers in the future could operate at speeds a million times faster than those of today. Scientists at Friedrich-Alexander University (FAU; Erlangen-Nurenberg, Germany) have now come one step closer to achieving this goal as they have succeeded in using ultra-short laser impulses to precisely control electrons in graphene. The scientists published their results in Physical Review Letters.

Current control in electronics that is one million times faster than in today’s systems is a dream for many. Ultimately, current control is one of the most important components as it is responsible for data and signal transmission. Controlling the flow of electrons using light waves instead of voltage signals, as is now the case, could make this dream a reality. However, up to now, it has been difficult to control the flow of electrons in metals as metals reflect light waves and the electrons inside them cannot be influenced by these light waves.

Physicists at FAU have therefore turned to graphene, a semi-metal that comprises only one single layer of carbon and is so thin that enough light can penetrate to enable electrons to be set in motion. In an earlier study, physicists at the Chair for Laser Physics had already succeeded in generating an electric signal at a time scale of only one femtosecond by using a very short laser pulse. This is equivalent to one millionth of one billionth of a second. In these extreme time scales, electrons reveal their quantum nature as they behave like a wave. The wave of electrons glides through the material as it is driven by the light field (the laser pulse).

The researchers went one step further in the current study. They aimed a second laser pulse at this light-driven wave. This second pulse now enables the electron wave to pass through the material in two dimensions. The second laser pulse can be used to deflect, accelerate or even change the direction of the electron wave. This enables information to be transmitted by this wave, depending on the exact time, strength and direction of the second pulse.

It’s possible to go one step further. “Imagine the electron wave is a wave in water. Waves in water can split because of an obstacle and converge and interfere when they have passed the obstacle. Depending on how the sub-waves stand in relation to one another, they either amplify or cancel each other out. We can use the second laser pulse to modify the individual sub-waves in a targeted manner and thus control their interference,” explains Christian Heide from the Chair of Laser Physics. “In general, it’s very difficult to control quantum phenomena, such as the wave characteristics of electrons in this instance. This is because it’s very difficult to maintain the electron wave in a material as the electron wave scatters with other electrons and loses its wave characteristics. Experiments in this field are typically performed at extremely low temperatures. We can now carry out these experiments at room temperature, since we can control the electrons using laser pulses at such high speeds that there is no time left for the scatter processes with other electrons. This enables us to research several new physical processes that were previously not accessible.”

It means the scientists have made significant progress towards realizing electronic systems that can be controlled using light waves. In the next few years they will be investigating whether electrons in other two-dimensional materials can also be controlled in the same way. “Maybe we will be able to use materials research to modify the characteristics of materials in such a way that it will soon be possible to build small transistors that can be controlled by light,” adds Heide.

Graphene on arbitrary substrates is a key to combine advanced electronic devices with carbon materials. For devices meant to withstand large currents or heat, thick multilayer graphene (MLG) is preferred over few-layer graphene.

For example, low-resistance wiring requires a thickness of tens of nanometers to replace copper wiring in large-scale integrated circuits, whereas a heat spreader requires a thickness of more than several micrometers, depending on the type of the device.

However, current vapor deposition techniques, including chemical vapor deposition and plasma-assisted vapor deposition, have difficulty forming thick, uniform MLG on insulating materials.
On the other hand, metal-induced solid-phase crystallization of amorphous carbon (a-C) or polymers has attracted increased attention for the direct synthesis of MLG on insulators.

Some of these techniques have allowed the synthesis of thick (>5 nm) MLG by controlling the initial thickness of amorphous carbon. However, further investigations were necessary to achieve a high-quality uniform MLG on insulators.

Reporting their findings in ACS Applied Materials & Interfaces (“Metal Catalysts for Layer-Exchange Growth of Multilayer Graphene”), researchers in Japan have developed a technique that uses ‘layer exchange’ to grow high-quality uniform crystals of MLG directly on an insulating material.

In this study, the scientists examine the potential of 15 kinds of transition metals (Ni, Co, Fe, Cr, Mn, Ru, Ir, Pt, Ti, Mo, W, Pd, Cu, Ag, and Au) to be used as catalysts for the metal-induced layer-exchange growth of MLG. The interaction between metal and carbon is summarized from the perspective of the periodic table.

All the team’s samples started with a stacked structure of an a-C/metal/SiO2 substrate and were then annealed at 600-1000°C for 1 hour in ambient Ar. From the experimental results, the interactions between the metals and a-C were classified into four groups: layer exchange; carbonization; local multilayer graphene formation; and no graphitization.

This classification was related to the arrangement of each element in the periodic table. In particular, layer exchange was achieved for the metals Co, Ni, Cr, Mn, Fe, Ru, Ir, and Pt.

The metals that allowed for layer exchange demonstrated the following tendency: metals with high C solid solubility induced low-temperature MLG synthesis, whereas metals with low C solid solubility produced high-quality MLG.

“The guidelines constructed in this study will play an important role in developing the research of growing MLG on substrates that could be used in advanced electronic devices,” the authors conclude.