Using a heat-resistant device, made of tungsten and alumina layers, researchers from Aalborg University have found that the device can absorb the sun’s broad spectrum radiation and convert it to electricity
The photovoltaic (PV) cells in traditional solar cells convert sunlight efficiently within a narrow range of wavelengths determined by the material used in the PV cells. This limits their efficiency, as long wavelengths of sunlight are not converted at all and the energy of short wavelength light is largely wasted. Scientists have sought to increase the efficiency of photovoltaics by creating “multi-junction” solar cells, made from several different semiconductor materials that absorb at varying wavelengths of light. The problem is, such multi-junction cells are expensive to make.
Broadband solar absorption previously has been achieved using metal-insulator-metal (or MIM) resonators, which consist of an insulator sandwiched between a thick bottom and a thin top layer, each made of metals like chromium and gold. The metal components used in MIM resonators have relatively low melting points—temperatures that are reduced further when the materials are in very thin layers, as in the resonators, because of a phenomenon called melting point depression, in which the melting point of a material scales down as the dimensions of the material decrease. The metals in standard MIM resonators melt at around 500 degrees Celsius, hindering their usefulness in solar cells.
Now a group of researchers in Denmark have discovered an alternative method to capture a broad spectrum of sunlight using a heat-resistant device made of tungsten and alumina layers that can be fabricated using inexpensive and widely available film-deposition techniques. The researchers describe their work and the new material in a paper published this week in the journal Optical Materials Express, from The Optical Society (OSA).
“They are resistant to heat, including thermal shock, and exhibit stable physical and chemical properties at high temperatures,” explained Manohar Chirumamilla of Aalborg University in Denmark, the first author of the new paper. This allows the absorbers to maintain their structural properties at very high temperatures.
In experiments, the new absorbers were shown to operate at a temperature of 800 degrees Celsius and to absorb light of wavelengths ranging from 300 to 1750 nanometers, that is, from ultraviolet (UV) to near-infrared wavelengths.
“MIM resonators absorbing in the spectral region from UV to near-infrared can be directly employed in different applications, such as solar TPV [thermophotovoltaic] /TPV systems and solar thermal systems,” Chirumamilla said. “Other potential applications include in so-called tower power plants, where concentrated solar light generates steam to drive a generator.”
“This is the first step in utilizing the energy of the sun in a more efficient way than with current solar cells,” he added. “Using an emitter in contact with our absorber, the generated heat can then be used to illuminate a solar cell—which can then function more efficiently when it is placed directly in the sun.”
From protecting our most valuable works of art to enabling smartphone displays, glass has become one of our most important materials. Making it even more versatile is the next challenge. Developing new glass compositions is largely a time-consuming, trial-and-error exercise. But now scientists have developed a way to decode the glass “genome” and design different compositions of the material without making and melting every possibility.
Their report appears in ACS’ journal Chemistry of Materials.
Despite the fact that humans have been making glass since antiquity, the material is still unpredictable. Scientists don’t yet fully understand how the structure of glass affects its properties such as density, crack resistance and melting temperatures. This knowledge gap hinders progress in developing new products, such as lighter windows for more fuel-efficient cars. A major complicating factor is that just about any element can be incorporated into glass, which means a near-endless list of possible compositions, each with a different set of properties. Glass types have been made by trial-and-error, but this process takes a lot of time. Morten M. Smedskjaer of Aalborg University and colleagues at Corning Incorporated wanted to come up with a faster way to develop new glass compositions for large-scale use.
The researchers combined a range of computer models, from the empirical to those grounded in physics, to explore what they call the glass genome — the possible combinations of materials and their resulting properties. Using these models, glass makers will be able to predict how various glass compositions will behave in the real world, and optimize them for industrial production much faster than before.
Aalborg University (AAU) was established in 1974 under the name of Aalborg University Center (AUC), but changed its name to Aalborg University in 1994. Today, Aalborg University is the fifth largest university in Denmark based on the number of enrolled students. In Aalborg, the university is mainly located on the main campus in the eastern part of the city, but the university also has departments located in downtown Aalborg.
Currently, Aalborg University has approximately 21,606 students and 3,479 employees. In 2011, Aalborg University experienced the largest increase in applicants in Denmark, as the number of new students increased by 31 per cent.
Aalborg University research articles from Innovation Toronto
Researchers from Aalborg University are involved in an international project to develop portable robot skeletons for the elderly so they can continue to be active longer. Think of it as a tool, not as a robot, says researcher.
The world’s population is aging. According to the World Health Organization (WHO), in 2050 there will be more than two billion people over age 60. And the older we get, the weaker our bodies become. So an international team of researchers and companies are working to develop an exoskeleton for senior citizens so they can remain active for longer.
“Many older people are mentally fit and want to continue to be active, but their physical abilities are steadily deteriorating,” explains Shaoping Bai, Associate Professor at the Department of Mechanical and Manufacturing Engineering at Aalborg University. This is an attempt to complement the strengths of older people so they can continue to be mobile and live independently for a longer time
Mathematical equations can make Internet communication via computer, mobile phone or satellite many times faster and more secure than today.
Results with software developed by researchers from Aalborg University in collaboration with the US universities the Massachusetts Institute of Technology (MIT) and California Institute of Technology (Caltech) are attracting attention in the international technology media.
A new study uses a four minute long mobile video as an example. The method used by the Danish and US researchers in the study resulted in the video being downloaded five times faster than state of the art technology. The video also streamed without interruptions. In comparison, the original video got stuck 13 times along the way.