Antonio Vivaldi

 

Nanoscale pillars could radically improve conversion of heat to electricity, say CU-Boulder researchers

An atomic-scale model of a nanophononic metamaterial. The vibrations caused by the pillar slow down the horizontal flow of heat through the thin film.

University of Colorado Boulder scientists have found a creative way to radically improve thermoelectric materials, a finding that could one day lead to the development of improved solar panels, more energy-efficient cooling equipment, and even the creation of new devices that could turn the vast amounts of heat wasted at power plants into more electricity.

The technique—building an array of tiny pillars on top of a sheet of thermoelectric material—represents an entirely new way of attacking a century-old problem, said Mahmoud Hussein, an assistant professor of aerospace engineering sciences who pioneered the discovery.

The thermoelectric effect, first discovered in the 1800s, refers to the ability to generate an electric current from a temperature difference between one side of a material and the other. Conversely, applying an electric voltage to a thermoelectric material can cause one side of the material to heat up while the other stays cool, or, alternatively, one side to cool down while the other stays hot.

Devices that incorporate thermoelectric materials have been used in both ways: to create electricity from a heat source, such as the sun, for example, or to cool precision instruments by consuming electricity.

However, the widespread use of thermoelectric materials has been hindered by a fundamental problem that has kept scientists busy for decades. Materials that allow electricity to flow through them also allow heat to flow through them. This means that at the same time a temperature difference creates an electric potential, the temperature difference itself begins to dissipate, weakening the current it created.

Until the 1990s, scientists addressed this problem by looking for materials with intrinsic properties that allowed electricity to flow more easily than heat.

“Until 20 years ago, people were looking at the chemistry of the materials,” Hussein said. “And then nanotechnology came into the picture and allowed researchers to engineer the materials for the properties they wanted.”

Using nanotechnology, material physicists began creating barriers in thermoelectric materials—such as holes or particles—that impeded the flow of heat more than the flow of electricity. But even under the best scenario, the flow of electrons—which carry electric energy—also was slowed.

In a new study published in the journal Physical Review Letters, Hussein and doctoral student Bruce Davis demonstrate that nanotechnology could be used in an entirely different way to slow the heat transfer without affecting the motion of electrons.

The new concept involves building an array of nanoscale pillars on top of a sheet of a thermoelectric material, such as silicon, to form what the authors call a “nanophononic metamaterial.” Heat is carried through the material as a series of vibrations, known as phonons. The atoms making up the miniature pillars also vibrate at a variety of frequencies. Davis and Hussein used a computer model to show that the vibrations of the pillars would interact with the vibrations of the phonons, slowing down the flow of heat. The pillar vibrations are not expected to affect the electric current.

The team estimates that their nanoscale pillars could reduce the heat flow through a material by half, but the reduction could be significantly stronger because the calculations were made very conservatively, Hussein said. 

“If we can improve thermoelectric energy conversion significantly, there will be all kinds of important practical applications,” Hussein said. These include recapturing the waste heat emitted by different types of equipment—from laptops to cars to power plants—and turning that heat into electricity. Better thermoelectrics also could vastly improve the efficiency of solar panels and refrigeration devices.

The next step is for Hussein to partner with colleagues in the physics department and other institutions to fabricate the pillars so that the idea can be tested in the lab. “This is still early in the phase of laboratory demonstration but the remaining steps are within reach.”

Hussein also hopes to further refine the models he used to gain additional insight into the underlying physics. “A team of highly motivated Ph.D. students are working with me around the clock on this project,” he said.

The research was funded by the National Science Foundation.

Read the study at http://prl.aps.org/abstract/PRL/v112/i5/e055505.

 

Shocking photos.

 

What the world eats (except Brazil) - link -

 

Homemade Energy Drink

 

I started out with the intention of coming up with a recipe for a homemade version of the store bought energy drinks, but after doing some research and discovering how unhealthy they are for you, I decided instead to try and design a less sugar/caffeine fueled way to help myself through the workday afternoon sleepy slump.
What I landed on was a system of three drinks and some energy boosting ideas that are going a long way to helping me keep my energy up all day long! Here's the good on the drinks:
The Fire Hydrant (left) - 3-4 8oz glasses throughout the day
filtered water
1 slice lemon
1 pinch cayenne pepper
Other than getting 7-8 hours of sleep a night, staying hydrated is the most important thing you can do to help keep your body functioning at optimum levels. So this drink is just water with a squeezed lemon slice and a pinch of cayenne pepper. The lemon not only tastes good, but is also super alkaline* which helps your body maintain a healthy pH level. The cayenne pepper helps raise energy levels naturally and provides protection for your heart by helping to maintain proper cardiovascular movement throughout the body. Combining this with 4-5 glasses of regular water will bring you up to your recommended 8 glasses of water per day!
*For an explanation of lemons' miraculous transition from acidic outside of the body, to alkaline once ingested, visit this link: http://phbalance.wikispaces.com/Lemons+Alkaline%3F
The Quick Fix (center) - as needed, during the day
(I don't recommend drinking it at night as it might keep you up)
hot water
1 1/2 - 2 tsp honey (to taste)
1 inch of fresh ginger root
1/4 tsp ground cardamom
1/4 tsp tumeric
Cut off two thin slices of ginger and place in your cup or mug.
Use a garlic press to juice the remaining ginger into your mug.
Add both spices and fill your mug with hot water and stir.
This is the closest thing I found to a non-caffeine/refined sugar pick me up! And I find it pretty delicious. Ginger speeds up metabolism and increases circulation. It also aids in the digestive process which can help stave off the post lunch coma that contributes to the afternoon slump. Turmeric, a cousin of ginger, also helps speed things up in the body, including energy levels! And Cardamom has long been valued medicinally for its ability to increase circulation and improve energy. Honey is mother nature's equivalent of an energy shot and is one of the best kinds of sugars for your body.
The Heavy Lifter (right) - 1 glass in the morning
1 ripe banana
1/4 cup raw almonds or 2 tbsp almond butter
1 scoop of high quality whey protein powder (low sugar content)
2 washed kale leaves
1/2 cup plain yogurt
1 tbsp ground flax seeds
1 cup milk of choice (I used unsweetened almond milk)
According to Dr. Oz, sixty percent of women don't get enough protein in their diets and that is often the number one reason for fatigue! (http://www.doctoroz.com/media/print/11196) A morning protein shake is a really easy and delicious way to make sure that you're starting the day off well fueled. Pair this with a piece of whole grain toast and you have everything you need to give you a solid energy foundation for the day.
The next steps are energy booster tips that I find, when done along with the drinks, help me keep on keeping on all day long!

Hoje, vende-se com a emoção e com o sentimento.

 

Psicologia da cor – link