Reduce Your Electricity Bills With New Solar Roof Tiles

source:http://wonderfulengineering.com

Solar power is the new “in” thing these days. It’s free, it’s clean and it’s abundant. So, what better use than to employ this free energy at home? Solar energy has been around since the dawn of man and it has probably been harnessed by civilizations before ours. Only recently, have we explored solar energy as an alternative to non-renewable energy. The Scandinavia, Germany and now China are swiftly developing solar energy tools to utilize maximum possible energy in the cheapest possible way.

A popular invention of the recent century is the ‘solar cell’ which is basically a semi-conductor material that converts solar energy to electrical energy. Solar cells gave birth to the concept of solar cars, solar heaters and solar parks. Recently, these cells have found their way into residential dwellings too!
Now you can simply turn your roof into a solar module using these solar cells and harness sun’s unlimited energy for no cost. Although, we do agree that the cells are costly but it is a one time investment and specially if you live in tropical or equatorial regions, the investment can be worth it.
One thing to keep in mind while you are planning to install solar cells on your rooftop is the orientation angle. The orientation angle is the particular angle of the rooftop, intensity of incoming radiations will depend on this angle. In order to maximize the energy, the orientation angle should be such that solar radiations make maximum contact with the roof.
These amazing and good looking cells can help you cut down on your energy bill. Of course when you are using solar power for half or even all of the appliances at home, the national grid cannot charge you much. Another useful advantage of solar modules is their easy availability whenever you are out of power (because solar power is a 24 hours service).
Many people are quickly turning their house roofs into solar panels and cutting down on their energy bills efficiently. Considering the global climate change and carbon footprint, anthropogenic activities are causing, we all can put in little efforts like buying solar cells, to help mitigate the environmental problem. Imagine how the environment can benefit if all the millions of people in the US alone shift to green energy. Not to mention, the roof looks spectacular with these solar cells. See for yourself.

 

Smart Window Blocks Heat, Generates Electricity

Buildings are going green and so it’s no surprise that researchers are working to develop smarter windows.
Among the smartest is a window designed by researchers at Shanghai University, led by Yanfeng Gao, which does triple duty: It’s transparent, regulates temperature fluctuations and doesn’t require external power to work.

The team’s goal was to find a way to merge a window with the power-generating capabilities of a solar panel, which typically isn’t transparent. Ideally, the researchers wanted to develop a window that would change its optical properties in response to temperature and do it without requiring power.
The answer was vanadium oxide. Gao’s team sandwiched a thin film of vanadium oxide between two layers of polycarbonate, the same material used in strong eyeglasses.
At room temperature, the polycarbonate panels appeared transparent. In fact, up to temperatures of 154 degrees Fahrenheit (68 C), the panels allowed heat — infrared light — to pass through. But once the temperature rose above that, the VO2 turned metallic and started reflecting the infrared wavelength, even though the panels appeared transparent to the eye.
In addition to regulating the wavelength of light, the vanadium also scattered some of the light to the sides of the panel. That’s where Gao’s group put a simple photovoltaic cell, which faced into the glass from the edge. In their experiment, sections of smart glass only a few inches on a side powered a 1.5-volt lamp.
Such a window would likely be more expensive than simple glass panes. But Gao and his co-authors noted in their study that buildings eat up 30 to 40 percent of the energy humans produce, and it all goes to heating, cooling and lighting. So a smart window like this could make a dent in that percentage.
The research is described in the current issue of the journal Scientific Reports.

 

Nanoscale Engineering Boosts Performance of Quantum Dot Light Emitting Diodes

Oct. 25, 2013 — Dramatic advances in the field of quantum dot light emitting diodes (QD-LEDs) could come from recent work by the Nanotechnology and Advanced Spectroscopy team at Los Alamos National Laboratory.

 

The quantum dot device structure shown with a transmission electron microscopy (TEM) image of a cross-section of a real device. (Credit: Image courtesy of DOE/Los Alamos National Laboratory)

Quantum dots are nano-sized semiconductor particles whose emission color can be tuned by simply changing their dimensions. They feature near-unity emission quantum yields and narrow emission bands, which result in excellent color purity. The new research aims to improve QD-LEDs by using a new generation of engineered quantum dots tailored specifically to have reduced wasteful charge-carrier interactions that compete with the production of light.
"QD-LEDs can potentially provide many advantages over standard lighting technologies, such as incandescent bulbs, especially in the areas of efficiency, operating lifetime and the color quality of the emitted light," said Victor Klimov of Los Alamos.
Incandescent bulbs, known for converting only 10 percent of electrical energy into light and losing 90 percent of it to heat, are rapidly being replaced worldwide by less wasteful fluorescent light sources. However, the most efficient approach to lighting is direct conversion of electricity into light using electroluminescent devices such as LEDs.
Due to spectrally narrow, tunable emission, and ease of processing, colloidal QDs are attractive materials for LED technologies. In the last decade, vigorous research in QD-LEDs has led to dramatic improvements in their performance, to the point where it nearly meets the requirements for commercial products. One outstanding challenge in the field is the so-called efficiency roll-off (known also as "droop"), that is, the drop in efficiency at high currents.
"This 'droop' problem complicates achieving practical levels of brightness required especially for lighting applications," said Wan Ki Bae, a postdoctoral researcher on the nanotech team.
By conducting spectroscopic studies on operational QD-LEDs, the Los Alamos researchers have established that the main factor responsible for the reduction in efficiency is an effect called Auger recombination. In this process, instead of being emitted as a photon, the energy from recombination of an excited electron and hole is transferred to the excess charge and subsequently dissipated as heat.
A paper, "Controlling the influence of Auger recombination on the performance of quantum-dot light-emitting diodes" is being published Oct. 25 in Nature Communications. In addition, an overview article on the field of quantum-dot light-emitting diodes and specifically the role of Auger effects appeared in the September Materials Research Society Bulletin, Volume 38, Issue 09, also authored by researchers of the Los Alamos nanotech team.
Not only has this work identified the mechanism for efficiency losses in QD-LEDs, Klimov said, but it has also demonstrated two different nano-engineering strategies for circumventing the problem in QD-LEDs based on bright quantum dots made of cadmium selenide cores overcoated with cadmium sulfide shells.
The first approach is to reduce the efficiency of Auger recombination itself, which can be done by incorporating a thin layer of cadmium selenide sulfide alloy at the core/shell interface of each quantum dot.
The other approach attacks the problem of charge imbalance by better controlling the flow of extra electrons into the dots themselves. This can be accomplished by coating each dot in a thin layer of zinc cadmium sulfide, which selectively impedes electron injection. According to Jeffrey Pietryga, a chemist in the nanotech team, "This fine tuning of electron and hole injection currents helps maintain the dots in a charge-neutral state and thus prevents activation of Auger recombination."
These studies were funded by a grant from the U.S. Department of Energy Office of Science.