Light Cue 23

Solar Sunday is my weekly roundup of renewable energy and energy efficiency news from around the web.

Spring back?

TreeHugger Labs proved conclusively two years ago that Daylight Saving Time was counterproductive; now it appears that other research is backing us up. When the idea was thought up, the biggest use of electricity was lighting, so it actually did save energy; now, with population shifts and upsizing of housing, air conditioning predominates and more we burn more electricity. An Australian researcher said “Basically if people wake up early in the morning and go to bed earlier, they do save artificial illumination at night and reduce electricity consumption in the evening. Our study confirmed that effect. But we also found that more electricity is consumed in the morning. In the end, these two effects wash each other out.” An Indiana study concluded that “daylight saving time did save on lighting use but that heating and air-conditioning use more than offset any gains.”

Energy positive architecture

Not settling for mere zero-energy, Adrian Smith + Gordon Gill’s Masdar Headquarters are setting new design standards for green building, with their scheme that generates more energy than it consumes. The Masdar Headquarters building outside of Abu Dhabi is also the first building in history to generate power for its own assembly, using a solar roof pier that will be built first to power the rest of the construction.

Rainbow Power

For the first time, researchers have created solar cells made of different-sized quantum dots, each tuned to a specific wavelength of light. By arranging these quantum dots in an ordered pattern, the scientists hope that they can one day fabricate “rainbow” solar cells, which can efficiently harvest a large part of the useful spectrum of sunlight.
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Using quantum dots to absorb light has a unique advantage over other light-absorbing materials: the “size quantization effect.” By varying the size of the tiny semiconductor quantum dots, the researchers can tune the solar cells to absorb light of certain wavelengths. Smaller quantum dots absorb shorter wavelengths of light, while larger quantum dots absorb longer wavelengths.

By combining different-sized quantum dots on one solar cell, the researchers can create solar cells that absorb more light and thereby deliver power at greater efficiencies compared with solar cells made of bulk semiconductors.

Solar paint. No, really! Solar paint

A lick of solar-power paint could see the roofs and walls of warehouses and other buildings generate electricity from the sun, if research by UK researchers pays off. The scientists are developing a way to paint solar cells onto the steel sheets commonly used to clad large buildings.

Steel sheets are painted rapidly in steel mills by passing them through rollers. A consortium led by Swansea University, UK, hopes to use that process to cover steel sheets with a photovoltaic paint at up to 40 square metres per minute.

The paint will be based on dye-sensitised solar cells. Instead of absorbing sunlight using silicon like conventional solar panels, they use dye molecules attached to particles of the titanium dioxide pigment used in paints.

That gives an energy boost to electrons, which hop from the dye into a layer of electrolyte. This then transfers the extra energy into a collecting circuit, before the electrons cycle back to the dye.

While less efficient than conventional cells, dye-based cells do not require expensive silicon, and can be applied as a liquid paste.

If you must drive, drive this

If you’re a fan of the Mini Cooper but want something a little greener, the Norwegian THINK car might just be your answer. It’s compact, it’s electric, it’s a zero-emissions zippy little car that’s a feat of design and engineering. Topping out at 100 km/hr and running for 180 km on a single charge, THINK is a lot of power for such a tiny thing. All the other systems are well-thought out too, with 90% of the energy going straight to the engine, compared to traditional combustion engines that lose up to 70% of their energy to heat and friction.

Polarizing technology

In recent years, light emitting diodes (LEDs) have begun to change the way we see the world. Now, a Rensselaer Polytechnic Institute student has developed a new type of LED that could allow for their widespread use as light sources for liquid crystal displays (LCDs) on everything from televisions and computers to cell phones and cameras.

Martin Schubert, a doctoral student in electrical, computer, and systems engineering, has developed the first polarized LED, an innovation that could vastly improve LCD screens, conserve energy, and usher in the next generation of ultra-efficient LEDs. Schubert’s innovation has earned him the $30,000 Lemelson-Rensselaer Student Prize.

Schubert’s polarized LED advances current LED technology in its ability to better control the direction and polarization of the light being emitted. With better control over the light, less energy is wasted producing scattered light, allowing more light to reach its desired location. This makes the polarized LED perfectly suited as a backlighting unit for any kind of LCD, according to Schubert. Its focused light will produce images on the display that are more colorful, vibrant, and lifelike, with no motion artifacts.

Black is the new Green

After turning yellow taxis green, New York City is now announcing that it wants to make black cars greener. There are currently about 10,000 of these large sedans (mostly Lincoln Town Cars) that primarily service corporate clients and they emit 272,000 tons of CO2 equivalents annually, not to mention smog-forming emissions. Michael Bloomberg, New York’s mayor, wants to cut their greenhouse gas emissions by half and at the same time improve air quality.