Innovative devices that convert sunlight to electric power more efficiently and cost effectively than the current generation of solar cell technology are the objects of a global pursuit—means to reducing fossil-fuel consumption and to securing pole position in the competition for fast-growing international markets for clean energy sources.
As reported in the journal Applied Optics,* the NIST team has combined 32 LEDs—each generating light from different segments of the solar spectrum—and other off-the-shelf equipment with their custom-made technologies to build a system that measures the wavelength-dependent quantum efficiency of solar devices over a relatively large area.
Anticipated advantages over current approaches—most of which use incandescent lamps or xenon arc and other types of discharge lamps—are greater speed and ease of operation, more uniform illumination, and a service life that is about 10 times longer.
The new NIST system for measuring spectral response easily accommodates two unique but complementary methods for determining how much electric current a solar, or photovoltaic (PV), device generates when hit by a standard amount of sunlight. Both methods are straightforward, and they use the same hardware setup.
With either method, the automated system produces measurements more rapidly than current instruments used to simulate solar radiation and characterize how efficiently a device converts light energy to electric energy.
One method, which activates the LED lights sequentially, is less subject to interference than the other technique, and yields a spectral response measurement in about 6 minutes. With the other method, all 32 LEDs are activated simultaneously, but each generates pulses of light at a different rate. The solar response of a PV device over the entire LED-blended spectrum can be determined in about 4 seconds.
Though more susceptible to interference, the faster method has potential for in-line manufacturing tests for ensuring quality, the researchers write.
The new system represents a major stride toward a technical goal set by a group of solar energy experts convened by NIST in late 2010.** "To accelerate all types of PV development and lower costs through more accurate assessment of performance," these experts set the goal to achieve spectral response measurements in fewer than 10 minutes.
While the new system beats the time requirement, the NIST team must push their technology further to match related targets that are part of the goal. Their to-do list includes matching or exceeding the energy intensity of the sun, broadening the LED-synthesized spectrum to include the infrared portion of the sun's output, and consistently achieving measurement results with uncertainties of less than 1 percent.
With their work to date, however, the NIST researchers have demonstrated that LEDs are now "technologically viable" for use in solar simulators and for characterizing PV and other photoelectric devices, says NIST physicist Behrang Hamadani.* B. H. Hamadani, J. Roller, B. Dougherty and H. W. Yoon. Versatile Light-Emitting-Diode-based Spectral Response Measurement System for Photovoltaic Device Characterization. Applied Optics Vol. 51, No. 19, July 1, 2102.
Mark Bello | EurekAlert!
Producing electricity during flight
20.09.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Solar-to-fuel system recycles CO2 to make ethanol and ethylene
19.09.2017 | DOE/Lawrence Berkeley National Laboratory
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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