rainbowcatch.jpgUB engineers have created a more efficient way to catch rainbows, an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research.

Qiaoqiang Gan, assistant professor of electrical engineering, and a team of graduate students described their work in a paper called “Rainbow Trapping in Hyperbolic Metamaterial Waveguide,” published Feb. 13 in the online journal Scientific Reports.

They developed a “hyperbolic metamaterial waveguide,” which is essentially an advanced microchip made of alternate ultra-thin films of metal and semiconductors and/or insulators. The waveguide halts and ultimately absorbs each frequency of light at slightly different places in a vertical direction to catch a “rainbow” of wavelengths.

SolarEnergy.jpgRice University scientists have unveiled a revolutionary new technology that uses nanoparticles to convert solar energy directly into steam. The new “solar steam” method from Rice’s Laboratory for Nanophotonics (LANP) is so effective it can even produce steam from icy cold water.

Details of the solar steam method were published online today in ACS Nano. The technology has an overall energy efficiency of 24 percent. Photovoltaic solar panels, by comparison, typically have an overall energy efficiency around 15 percent. However, the inventors of solar steam said they expect the first uses of the new technology will not be for electricity generation but rather for sanitation and water purification in developing countries.

sunflower.jpgA field of young sunflowers will slowly rotate from east to west during the course of a sunny day, each leaf seeking out as much sunlight as possible as the sun moves across the sky through an adaptation called heliotropism.

It's a clever bit of natural engineering that inspired imitation from a UW-Madison electrical and computer engineer, who has found a way to mimic the passive heliotropism seen in sunflowers for use in the next crop of solar power systems. 

Unlike other "active" solar systems that track the sun's position with GPS and reposition panels with motors, electrical and computer engineering professor Hongrui Jiang's concept leverages the properties of unique materials in concert to create a passive method of re-orienting solar panels in the direction of the most direct sunlight.

His design, published Aug. 1 in Advanced Functional Materials and recently highlighted in Nature, employs a combination of liquid crystalline elastomer (LCE), which goes through a phase change and contracts in the presence of heat, with carbon nanotubes, which can absorb a wide range of light wavelengths.

In some isolated clinics in parts of Africa, the electricity needed to power lights and medical devices is generated by expensive imported diesel fuel; the water supply can be so cold in winter that health workers can’t even wash their hands properly. But a startup company established by a team of MIT students and alumni aims to change that.

The patented technology they developed uses a mirrored parabolic trough to capture sunlight, heating fluid in a pipe along the mirror’s centerline. This fluid then powers a sort of air conditioner in reverse: Instead of using electricity to pump out cold air on one side and hot air on the other, it uses the hot fluid and cold air to generate electricity. At the same time, the hot fluid can be used to provide heat and hot water — or, by adding a separate chiller stage, to produce cooling as well.

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