12 Emerging Technologies that May Help Power the Future
According to UN forecasts, the world population will exceed 11 billion by 2021. The increase will face environmental challenges and pressures on energy sources.
So, researchers at Georgia Tech University are researching technologies that develop energy abundance, efficient and eco-friendly.
Here’s a brief look at 12 unexpected technologies that can provide future energy for the Earth.
1- Na-TECC; Worth its salt
Shannon Yee is developing a technology that leverages the isothermal expansion of sodium and solar heat to directly generate electricity. Affectionately known as “Na-TECC” (an acronym that combines the chemical symbol for sodium with initials from “Thermo-Electro-Chemical Converter” and also rhymes with “GaTech”), this unique conversion engine has no moving parts.
The goal of this technology is to convert heat into electricity with efficiencies of over 45 percent.
2- New Breed of Betavoltaics
In another project, Yee’s group is using nuclear waste to produce electricity — minus the reactor and sans moving parts.
Funded by the Defense Advanced Research Projects Agency (DARPA) and working in collaboration with Stanford University, the researchers have developed a technology that is similar to photovoltaic devices with one big exception: Instead of using photons from the sun, it uses high-energy electrons emitted from nuclear byproducts.
Betavoltaic technology has been around since the 1950s, but researchers have focused on tritium or nickel-63 as beta emitters. “Our idea was to revisit the technology from a radiation transport perspective and use strontium-90, a prevalent isotope in nuclear waste,” Yee said.
Strontium-90 is unique because it emits two high-energy electrons during its decay process. What’s more, strontium-90’s energy spectrum aligns well with design architecture already used in crystalline silicon solar cells, so it could yield highly efficient conversion devices.
3- Flexible Generators
Yee’s group is also pioneering the use of polymers in thermoelectric generators (TEGs).
Solid-state devices that directly convert heat to electricity without moving parts, TEGs are typically made from inorganic semiconductors. Yet polymers are attractive materials due to their flexibility and low thermal conductivity. These qualities enable clever designs for high-performance devices that can operate without active cooling, which would dramatically reduce production costs.
“Thermoelectrics are still limited to niche applications, but they could displace batteries in some situations,” Yee said. “And the great thing about polymers, we can literally paint or spray material that will generate electricity.”
4- Recycling Radio Waves
Researchers led by Manos Tentzeris have developed an electromagnetic energy harvester that can collect enough ambient energy from the radio frequency (RF) spectrum to operate devices for the Internet of Things (IoT), smart skin and smart city sensors, and wearable electronics.
Harvesting radio waves is not brand new, but previous efforts have been limited to short-range systems located within meters of the energy source, explained Tentzeris, a professor in Georgia Tech’s School of Electrical and Computer Engineering. His team is the first to demonstrate long-range energy harvesting as far as seven miles from a source.
Recently capabilities of this technology is increased to collect energy from multiple TV channels, Wi-Fi, cellular, and handheld electronic devices, enabling the system to harvest power in the order of milliwatts.
5- Picking Up Good Vibrations
In another energy harvesting approach, researchers in Georgia Tech’s School of Mechanical Engineering are making advances with piezoelectric energy — converting mechanical strain from ambient vibrations into electricity.
Scientists have been exploring this field for more than a decade, but technologies haven’t been widely commercialized because piezoelectric harvesting is very case and application dependent, explained Alper Erturk, an assistant professor of acoustics and dynamics who leads Georgia Tech’s Smart Structures and Dynamical Systems Laboratory.
Current piezoelectric energy harvesters rely on linear resonance behavior, and to maximize electrical power, the excitation frequency of ambient sources must match the resonance frequency of the harvester. “Even a slight mismatch results in drastically reduced power output, and there are numerous scenarios where that happens,” Erturk said.
Although electrical output from vibration energy harvesters is small, it is still enough to power wireless sensors for structural health monitoring in bridges or aircraft, wearable electronics, or even medical implants. “Piezoelectric harvesting could eliminate the hassle of replacing batteries in many low-power devices — providing cleaner power, greater convenience, and meaningful savings over time,” Erturk said.
6- Power Rubbed The Right Way
Triboelectricity enables production of an electrical charge from friction caused by two different materials coming into contact. Although known for centuries, the phenomenon has been largely ignored as an energy source because of its unpredictability.
Yet researchers led by Zhong Lin Wang, a Regents Professor in Georgia Tech’s School of Materials Science and Engineering, have created novel triboelectric nanogenerators (TENGs) that combine the triboelectric effect and electrostatic induction. By harvesting random mechanical energy, these generators can continuously operate small electronic devices.
Behind these recent milestones is a two-stage design: First the TENG charges a small capacitor. Then energy is transferred to a final storage device (a larger capacitor or battery) that matches the impedance of the generator’s output and provides appropriate voltage and constant output.
“This really broadens the number of possible applications,” Wang said, pointing to temperature sensors, heart rate monitors, pedometers, watches, scientific calculators, and RF wireless transmitters.
7- Optical Rectenna
Researchers led by Baratunde Cola, an associate professor in Georgia Tech’s School of Mechanical Engineering, have developed the first known optical rectenna — a technology that could be more efficient than today’s solar cells and less expensive.
Rectennas, which are part antenna and part rectifier, convert electromagnetic energy into direct electrical current. The basic idea has been around since the 1960s, but Cola’s team makes it possible with nanoscale fabrication techniques and different physics. “Instead of converting particles of light, which is what solar cells do, we’re converting waves of light,” he explained.
Key to this technology are antennas small enough to match the wavelength of light (about one micron) and a super-fast diode — achieved in part by building the antenna on one of the metals in the diode. Cola describes the process:
- Carbon nanotubes are grown vertically off a substrate.
- Using atomic layer deposition, the nanotubes are coated with aluminum oxide to serve as an insulator.
- Extremely thin layers of calcium and aluminum metals are placed on top to act as an anode.
As light hits the carbon nanotubes, a charge moves through the rectifier, which switches on and off to create a small direct current. The metal-insulator-metal-
diode structure is fast enough to open and close at a rate of 1 quadrillion times per second.
The researchers are now focused on lowering contact resistance and growing the nanotubes on flexible substrates for applications that require bending.
8- Pulp Energy
Although fossil-fuel emissions may be the poster child for global warming, there is also growing concern over environmental harm from discarded electronics.
Researchers at Georgia Tech’s Center for Organic Photonics and Electronics (COPE) and Renewable Bioproducts Institute are developing paper-based electronics — organic solar cells, organic light-emitting diodes (OLEDs), and organic field-effect transistors (OFETs) — fabricated on cellulose-based substrates that can be recycled easily.
Today’s organic electronic components use very thin carbon-based semiconductor layers — about 1,000 times thinner than the average human hair. “Because they are so thin, you need nearly atomically flat substrates where the surface is down to a nanometer,” explained Bernard Kippelen, director of COPE and a professor in Georgia Tech’s School of Electrical and Computer Engineering.
To address this, Kippelen’s team is using cellulose nanocrystals (CNCs), a type of wooden wunderkind material, to develop new semiconductor devices, demonstrating that CNCs are a viable alternative to traditional plastic substrates — while offering new environmental benefits. Devices made on these substrates can be easily dissolved in water, allowing semiconducting materials and metal layers to be filtered and recycled.
9- Fuel from the Sky
In another intriguing project, researchers led by Peter Loutzenhiser are leveraging solar energy to reverse the combustion process and produce synthesis gas (mixtures of hydrogen, carbon monoxide, and small amounts of carbon dioxide), which can be converted into fuels such as kerosene and gasoline.
“Instead of using fossil resources to create fuel, we are using the byproducts of combustion (water and carbon dioxide) to re-energize the system with the sun,” explained Loutzenhiser, an assistant professor at Georgia Tech’s School of Mechanical Engineering.
The researchers are studying a two-step process using metal oxides that can split water and carbon dioxide. The first step, which occurs between 1100 and 1800 degrees Celsius, thermally reduces or “pulls off” oxygen from the metal oxide material. Then at temperatures of about 300 to 900 degrees Celsius, either water or carbon dioxide is introduced in the second step. These lower temperatures are favorable for re-oxidation, which enables the metal oxide to take back oxygen from either the water or carbon dioxide, resulting in hydrogen or carbon monoxide. “The two steps are important — otherwise the oxygen would recombine with either the carbon monoxide or hydrogen, resulting in the release of heat that would then be lost,” Loutzenhiser said.
If commercialized, the technology could transform desert areas into fuel farms, Loutzenhiser said: “Instead of pulling fuel out of the ground, we could pull carbon dioxide from the air and use the sun to convert it with water into a long-term storage medium that could be shipped and used around the world without changes to transportation infrastructure.”
10- Hello Graphene Supercaps, Good-bye Batteries?
Used in everything from military applications to elevators and cars, supercapacitors are attractive sources for clean energy because they quickly charge and discharge and have long cycling lives. But there’s one big drawback: low energy density.
“Today’s supercapacitors have only one-tenth the energy density of lithium-ion batteries,” pointed out Meilin Liu, a Regents Professor in Georgia Tech’s School of Materials Science and Engineering. “For the device to give you the same electrical energy, the device would have to be much bigger.”
Graphene is a two-dimensional material that conducts electricity better than copper and is both lighter than steel and 100 times stronger. Yet graphene has a tendency to stack together and form graphite. To prevent this, the researchers place molecular spacers between the graphene sheets, creating a 3-D porous structure that demonstrates a capacitance of 400 Faradays per gram — four times higher than current supercaps.
The researchers have also improved capacitance by dispersing transition metal compounds into the graphene-based structure.
Graphene alone can only produce a capacitance of about 400 Faradays per gram of material. In contrast, transition metal compounds have higher energy density (2,000 to 3,000 Faradays per gram), but poor electronic connectivity, which slows down the flow of electrons required for charging and discharging. Yet by combining the metal compounds with the 3-D porous graphene, which scores high marks for connectivity, the researchers have achieved capacitance of about 1,500 Faradays per gram while maintaining superior cycling.
“This new breed of supercaps could replace batteries, providing cleaner, safer, and more robust power for many applications, from portable electronics to electric vehicles and smart grids.”
11- Monolithic Microscale Heat Pumps
Proving that good things come in small packages, researchers led by Srinivas Garimella have developed a novel textbook-sized cooling system that operates on waste heat rather than electricity.
Since unveiling a proof-of-concept unit in 2009, the researchers have developed heat pumps with cooling capacities of one and two refrigerant tons. (Capacity of current residential units ranges from one to four refrigerant tons.) Efficiency has been substantially improved, and fabrication techniques have also been improved to enable mass production.
The researchers have also adapted the technology to provide cooling using waste heat from diesel-driven generators at military bases, where ambient temperatures are extremely high. “Not only is diesel fuel very expensive to transport, there are also risks to humans in delivering the fuel,” Garimella said. “Using the energy in the diesel fuel to the fullest extent by providing power as well as cooling through these units, without consuming additional prime energy, will lower overall costs and increase personnel safety.”
12- Next-gen Power Plants
Researchers in Georgia Tech’s School of Mechanical Engineering are working on major makeovers for power plants, introducing innovations that range from revamped power cycles to new infrastructure materials.
In one project, steam is being replaced with supercritical carbon dioxide (SCCO2) as the working fluid to operate turbines and produce electricity.
SCCO2 results when carbon dioxide is subjected to pressure above 7.4 megapascals and temperatures above 31 degrees Celsius. This magical state, somewhere between a liquid and a gas, provides high fluid density, thermal conductivity, and heat capacity.
Using SCCO2 in concentrated solar plants could push thermal efficiencies from 45 to 60 percent, enough to be competitive with fossil fuel, said Asegun Henry, an assistant professor of heat transfer, combustion, and energy systems. “Yet this requires higher operating temperatures — 800 degrees Celsius compared to current temperatures below 600 degrees — and current heat exchangers literally can’t take the pressure.”
In addition to making solar power more competitive, the heat exchangers could also be used with SCCO2 to boost efficiency in fossil fuel power plants. “More efficiency means less carbon dioxide emissions per kilowatt produced,” Henry said.