Think molecules are dull? Look at these beauties.

If molecules were this large, think how much more esthetic the world would be.

 

Cloudy skies on nearby super-Earth by Alexandra Witze

NASA, ESA & G.Bacon

An artist's view of the extrasolar planet GJ 1214b, which scientists say has an atmosphere thick with clouds.

One of the best-studied nearby extrasolar planets — a body just a little larger than Earth — is swaddled in alien clouds, researchers have found. It is the smallest and most Earth-like world yet to yield the secrets of its atmosphere. Another study has found tantalizing hints of clouds on a larger, Neptune-sized world. The pair of discoveries, reported today in Nature^{1, 2}, suggests that clouds may envelop many exoplanets.

“We always knew the clouds must be there for some planets, but now we have a wave of results telling us that clouds are actually very common,” says Heather Knutson, a planetary astronomer at the
California Institute of Technology in Pasadena and lead author of the second paper.

The two planets are among the closest to our Solar System to have been found so far. The super-Earth discovery involves GJ 1214b, just 13 parsecs (about 42 light years) from us, which whirls around a red dwarf star once every 38 hours. As the planet passes across the star’s face, some of the starlight should filter through the planet's atmosphere, revealing its composition.

In 2010, scientists reported finding no imprint of GJ 1214b's atmosphere in the spectrum of light from its host star (see ‘A gaze at exoplanet haze’). Researchers speculated that clouds could be blocking the background starlight from getting through.

Another option was that the planet's atmosphere was made mostly of heavy molecules, such as water, rather than lightweight hydrogen. If this was the case, then the planet's gravity would compress its atmosphere into a thin, dense layer. This thin layer shrinks the size of features in the spectrum to below what the measurements could detect.

At the time, researchers could not distinguish between these two options. Now, observations from the Hubble Space Telescope show that clouds must be present.

A team led by Laura Kreidberg, of the University of Chicago in Illinois, studied near-infrared light filtering around GJ 1214b during 15 of its passages in front of its star. This gave the scientists enough data to have seen the spectral imprint of a water-rich atmosphere had it been there. They saw nothing, and concluded that the planet must be swathed in clouds.

Kreidberg says that the atmosphere could still be made mostly of water vapour. “But we found there also have to be clouds,” she says.

Those clouds would be unlike any on Earth, given the temperatures and pressures in the exoplanet's atmosphere. They could be made of something like zinc sulphide or potassium chloride, as both of these compounds would condense into microscopic droplets, and thus form clouds, under such conditions. “It’s the first time that we’ve been able to characterize the atmosphere of an exoplanet smaller than Neptune,” says Kreidberg.

Similar clouds may also enshroud the larger, Neptune-sized world known as GJ 436b, located about 10 parsecs (33 light years) away. Caltech’s Knutson and her colleagues targeted this planet because it is an archetype of many similarly sized exoplanets. Like Kreidberg’s team, these scientists also used the Hubble telescope to watch changes in a star’s light as the planet passed in front of it.

Once again, the star’s spectrum showed no imprint of the planet's atmosphere. And once again, the options are either a cloudy atmosphere or one that is weighed down by heavy molecules such as water or methane.

Neptune is made mostly of hydrogen and helium, so a Neptune-sized object with a heavy atmosphere would defy expectations, says Knutson. “We thought this was just a Neptune analogue, but if it doesn’t have a lot of hydrogen we have to think harder about how you would build a planet like that,” she says.

Both new studies show how clouds are cropping up on more and more exoplanets, says Julianne Moses, a planetary scientist at the Space Science Institute in Boulder, Colorado. In October, a team led by scientists at the Massachusetts Institute of Technology in Cambridge reported mapping clouds on two different hemispheres of a planet called Kepler-7b³.

 

 

Lithopanspermia: How Earth May Have Seeded Life on Other Solar System Bodies by Shannon Hall

December 17, 2013

Want to stay on top of all the space news? Follow @universetoday on Twitter

An artist’s conception of a rock fragment colliding with Europa’s icy surface. Image Credit: NASA/JPL

With the recent discovery that Europa has geysers, and therefore definitive proof of a liquid ocean, there’s a lot of talk about the possibility of life in the outer solar system.

According to a new study, there is a high probably that life spread from Earth to other planets and moons during the period of the late heavy bombardment — an era about 4.1 billion to 3.8 billion years ago — when untold numbers of asteroids and comets pummeled the Earth. Rock fragments from the Earth would have been ejected after a large meteoroid impact, and may have carried the basic ingredients for life to other solar system bodies.

These findings, from Pennsylvania State University, strongly support lithopanspermia: the idea that basic life forms can be distributed throughout the solar system via rock fragments cast forth by meteoroid impacts.

Strong evidence for lithopanspermia is found within the rocks themselves. Of the over 53,000 meteorites found on Earth, 105 have been identified as Martian in origin. In other words an impact on Mars ejected rock fragments that then hit the Earth.

The researchers simulated a large number of rock fragments ejected from the Earth and Mars with random velocities. They then tracked each rock fragment in n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine how the rock fragments move among the planets.

“We ran the simulations for 10 million years after the ejection, and then counted up how many rocks hit each planet,” said doctoral student Rachel Worth, lead author on the study.

Their simulations mainly showed a large number of rock fragments falling into the Sun or exiting the solar system entirely, but a small fraction hit planets. These estimations allowed them to calculate the likelihood that a rock fragment might hit a planet or a moon. They then projected this probability to 3.5 billion years, instead of 10 million years.

In general the number of impacts decreased with the distance away from the planet of origin. Over the course of 3.5 billion years, tens of thousands of rock fragments from the Earth and Mars could have been transferred to Jupiter and several thousand rock fragments could have reached Saturn.

“Fragments from the Earth can reach the moons of Jupiter and Saturn, and thus could potentially carry life there,” Worth told Universe Today.

The researchers looked at Jupiter’s Galilean satellites: Io, Europa, Ganymede and Callisto and Saturn’s largest moons: Titan and Enceladus. Over the course of 3.5 billion years, each of these moons received between one and 10 meteoroid impacts from the Earth and Mars.

It’s statistically possible that life was carried from the Earth or Mars to one of the moons of Jupiter or Saturn. During the period of late bombardment the solar system was much warmer and the now icy moons of Saturn and Jupiter didn’t have those protective shells to prevent meteorites from reaching their liquid interiors. Even if they did have a thin layer of ice, there’s a large chance that a meteorite would fall though, depositing life in the ocean beneath.

In the case of Europa, six rock fragments from the Earth would have hit it over the last 3.5 billion years.

It has previously been thought that finding life in Europa’s oceans would be proof of an independent origin of life. “But our results suggest we can’t assume that,” Worth said. “We would need to test any life found and try to figure out whether it descended from Earth life, or is something really new.”

The paper has been accepted for publication in the journal Astrobiology and is available for download here.

The Baloney Detection Kit: Carl Sagan’s Rules for Bullshit-Busting and Critical Thinking by Maria Popova

Necessary cognitive fortification against propaganda, pseudoscience, and general falsehood.
Carl Sagan was many things — a cosmic sage, voracious reader, hopeless romantic, and brilliant philosopher. But above all, he endures as our era’s greatest patron saint of reason and common sense, a master of the vital balance between skepticism and openness. In The Demon-Haunted World: Science as a Candle in the Dark (public library) — the same indispensable volume that gave us
Sagan’s timeless meditation on science and spirituality, published mere months before his death in 1996 — Sagan shares his secret to upholding the rites of reason, even in the face of society’s most shameless untruths and outrageous propaganda.

In a chapter titled “The Fine Art of Baloney Detection,” Sagan reflects on the many types of deception to which we’re susceptible — from psychics to religious zealotry to paid product endorsements by scientists, which he held in especially low regard, noting that they “betray contempt for the intelligence of their customers” and “introduce an insidious corruption of popular attitudes about scientific objectivity.” (Cue in PBS’s Joe Hanson on how to read science news.) But rather than preaching from the ivory tower of self-righteousness, Sagan approaches the subject from the most vulnerable of places — having just lost both of his parents, he reflects on the all too human allure of promises of supernatural reunions in the afterlife, reminding us that falling for such fictions doesn’t make us stupid or bad people, but simply means that we need to equip ourselves with the right tools against them.



Through their training, scientists are equipped with what Sagan calls a “baloney detection kit” — a set of cognitive tools and techniques that fortify the mind against penetration by falsehoods:

The kit is brought out as a matter of course whenever new ideas are offered for consideration. If the new idea survives examination by the tools in our kit, we grant it warm, although tentative, acceptance. If you’re so inclined, if you don’t want to buy baloney even when it’s reassuring to do so, there are precautions that can be taken; there’s a tried-and-true, consumer-tested method.

But the kit, Sagan argues, isn’t merely a tool of science — rather, it contains invaluable tools of healthy skepticism that apply just as elegantly, and just as necessarily, to everyday life. By adopting the kit, we can all shield ourselves against clueless guile and deliberate manipulation. Sagan shares nine of these tools:

Wherever possible there must be independent confirmation of the “facts.”

Encourage substantive debate on the evidence by knowledgeable proponents of all points of view.

Arguments from authority carry little weight — “authorities” have made mistakes in the past. They will do so again in the future. Perhaps a better way to say it is that in science there are no authorities; at most, there are experts.

Spin more than one hypothesis. If there’s something to be explained, think of all the different ways in which it could be explained. Then think of tests by which you might systematically disprove each of the alternatives. What survives, the hypothesis that resists disproof in this Darwinian selection among “multiple working hypotheses,” has a much better chance of being the right answer than if you had simply run with the first idea that caught your fancy.

Try not to get overly attached to a hypothesis just because it’s yours. It’s only a way station in the pursuit of knowledge. Ask yourself why you like the idea. Compare it fairly with the alternatives. See if you can find reasons for rejecting it. If you don’t, others will. 

Quantify. If whatever it is you’re explaining has some measure, some numerical quantity attached to it, you’ll be much better able to discriminate among competing hypotheses. What is vague and qualitative is open to many explanations. Of course there are truths to be sought in the many qualitative issues we are obliged to confront, but finding them is more challenging.

If there’s a chain of argument, every link in the chain must work (including the premise) — not just most of them.

Occam’s Razor. This convenient rule-of-thumb urges us when faced with two hypotheses that explain the data equally well to choose the simpler.

Always ask whether the hypothesis can be, at least in principle, falsified. Propositions that are untestable, unfalsifiable are not worth much. Consider the grand idea that our Universe and everything in it is just an elementary particle — an electron, say — in a much bigger Cosmos. But if we can never acquire information from outside our Universe, is not the idea incapable of disproof? You must be able to check assertions out. Inveterate skeptics must be given the chance to follow your reasoning, to duplicate your experiments and see if they get the same result.

Just as important as learning these helpful tools, however, is unlearning and avoiding the most common pitfalls of common sense. Reminding us of where society is most vulnerable to those, Sagan writes:

In addition to teaching us what to do when evaluating a claim to knowledge, any good baloney detection kit must also teach us what not to do. It helps us recognize the most common and perilous fallacies of logic and rhetoric. Many good examples can be found in religion and politics, because their practitioners are so often obliged to justify two contradictory propositions.

He admonishes against the twenty most common and perilous ones — many rooted in our chronic discomfort with ambiguity — with examples of each in action:

1. ad hominem — Latin for “to the man,” attacking the arguer and not the argument (e.g., The Reverend Dr. Smith is a known Biblical fundamentalist, so her objections to evolution need not be taken seriously)
2. argument from authority (e.g., President Richard Nixon should be re-elected because he has a secret plan to end the war in Southeast Asia — but because it was secret, there was no way for the electorate to evaluate it on its merits; the argument amounted to trusting him because he was President: a mistake, as it turned out)
3. argument from adverse consequences (e.g., A God meting out punishment and reward must exist, because if He didn’t, society would be much more lawless and dangerous — perhaps even ungovernable. Or: The defendant in a widely publicized murder trial must be found guilty; otherwise, it will be an encouragement for other men to murder their wives)
4. appeal to ignorance — the claim that whatever has not been proved false must be true, and vice versa (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist — and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we’re still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.
5. special pleading, often to rescue a proposition in deep rhetorical trouble (e.g., How can a merciful God condemn future generations to torment because, against orders, one woman induced one man to eat an apple? Special plead: you don’t understand the subtle Doctrine of Free Will. Or: How can there be an equally godlike Father, Son, and Holy Ghost in the same Person? Special plead: You don’t understand the Divine Mystery of the Trinity. Or: How could God permit the followers of Judaism, Christianity, and Islam — each in their own way enjoined to heroic measures of loving kindness and compassion — to have perpetrated so much cruelty for so long? Special plead: You don’t understand Free Will again. And anyway, God moves in mysterious ways.)
6. begging the question, also called assuming the answer (e.g., We must institute the death penalty to discourage violent crime. But does the violent crime rate in fact fall when the death penalty is imposed? Or: The stock market fell yesterday because of a technical adjustment and profit-taking by investors — but is there any independent evidence for the causal role of “adjustment” and profit-taking; have we learned anything at all from this purported explanation?)
7. observational selection, also called the enumeration of favorable circumstances, or as the philosopher Francis Bacon described it, counting the hits and forgetting the misses (e.g., A state boasts of the Presidents it has produced, but is silent on its serial killers)
8. statistics of small numbers — a close relative of observational selection (e.g., “They say 1 out of every 5 people is Chinese. How is this possible? I know hundreds of people, and none of them is Chinese. Yours truly.” Or: “I’ve thrown three sevens in a row. Tonight I can’t lose.”)
9. misunderstanding of the nature of statistics (e.g., President Dwight Eisenhower expressing astonishment and alarm on discovering that fully half of all Americans have below average intelligence);
10. inconsistency (e.g., Prudently plan for the worst of which a potential military adversary is capable, but thriftily ignore scientific projections on environmental dangers because they’re not “proved.” Or: Attribute the declining life expectancy in the former Soviet Union to the failures of communism many years ago, but never attribute the high infant mortality rate in the United States (now highest of the major industrial nations) to the failures of capitalism. Or: Consider it reasonable for the Universe to continue to exist forever into the future, but judge absurd the possibility that it has infinite duration into the past);
11. non sequitur — Latin for “It doesn’t follow” (e.g., Our nation will prevail because God is great. But nearly every nation pretends this to be true; the German formulation was “Gott mit uns”). Often those falling into the non sequitur fallacy have simply failed to recognize alternative possibilities;
12. post hoc, ergo propter hoc — Latin for “It happened after, so it was caused by” (e.g., Jaime Cardinal Sin, Archbishop of Manila: “I know of … a 26-year-old who looks 60 because she takes [contraceptive] pills.” Or: Before women got the vote, there were no nuclear weapons)
13. meaningless question (e.g., What happens when an irresistible force meets an immovable object? But if there is such a thing as an irresistible force there can be no immovable objects, and vice versa)
14. excluded middle, or false dichotomy — considering only the two extremes in a continuum of intermediate possibilities (e.g., “Sure, take his side; my husband’s perfect; I’m always wrong.” Or: “Either you love your country or you hate it.” Or: “If you’re not part of the solution, you’re part of the problem”)
15. short-term vs. long-term — a subset of the excluded middle, but so important I’ve pulled it out for special attention (e.g., We can’t afford programs to feed malnourished children and educate pre-school kids. We need to urgently deal with crime on the streets. Or: Why explore space or pursue fundamental science when we have so huge a budget deficit?);
16. slippery slope, related to excluded middle (e.g., If we allow abortion in the first weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant. Or, conversely: If the state prohibits abortion even in the ninth month, it will soon be telling us what to do with our bodies around the time of conception);
17. confusion of correlation and causation (e.g., A survey shows that more college graduates are homosexual than those with lesser education; therefore education makes people gay. Or: Andean earthquakes are correlated with closest approaches of the planet Uranus; therefore — despite the absence of any such correlation for the nearer, more massive planet Jupiter — the latter causes the former)
18. straw man — caricaturing a position to make it easier to attack (e.g., Scientists suppose that living things simply fell together by chance — a formulation that willfully ignores the central Darwinian insight, that Nature ratchets up by saving what works and discarding what doesn’t. Or — this is also a short-term/long-term fallacy — environmentalists care more for snail darters and spotted owls than they do for people)
19. suppressed evidence, or half-truths (e.g., An amazingly accurate and widely quoted “prophecy” of the assassination attempt on President Reagan is shown on television; but — an important detail — was it recorded before or after the event? Or: These government abuses demand revolution, even if you can’t make an omelette without breaking some eggs. Yes, but is this likely to be a revolution in which far more people are killed than under the previous regime? What does the experience of other revolutions suggest? Are all revolutions against oppressive regimes desirable and in the interests of the people?)
20. weasel words (e.g., The separation of powers of the U.S. Constitution specifies that the United States may not conduct a war without a declaration by Congress. On the other hand, Presidents are given control of foreign policy and the conduct of wars, which are potentially powerful tools for getting themselves re-elected. Presidents of either political party may therefore be tempted to arrange wars while waving the flag and calling the wars something else — “police actions,” “armed incursions,” “protective reaction strikes,” “pacification,” “safeguarding American interests,” and a wide variety of “operations,” such as “Operation Just Cause.” Euphemisms for war are one of a broad class of reinventions of language for political purposes. Talleyrand said, “An important art of politicians is to find new names for institutions which under old names have become odious to the public”)

Sagan ends the chapter with a necessary disclaimer:

Like all tools, the baloney detection kit can be misused, applied out of context, or even employed as a rote alternative to thinking. But applied judiciously, it can make all the difference in the world — not least in evaluating our own arguments before we present them to others.

The Demon-Haunted World is a timelessly fantastic read in its entirety, timelier than ever in a great many ways amidst our present media landscape of propaganda, pseudoscience, and various commercial motives. Complement it with Sagan on science and “God”.

Biofuels Vital Graphics - Powering Green Economy

Biofuels Vital Graphics visualizes the opportunities, the need for safeguards, and the options that help ensure sustainability of biofuels to make them a cornerstone for a Green Economy. Stories from around the world have been highlighter to exemplify possible approaches, lessons learned, risks and opportunities Biofuels Vital Graphics is meant as a communications tool.

It builds on an earlier report by the International Panel for Sustainable Resource Management of the United Nations Environment Programme, Towards Sustainable Production and Use of Resources: Assessing Biofuels, as well as research produced since.

Read online: 
Web | Mobile | PDF (4mb) | E-book (flash) | iTunes app | Maps & Graphics collection

Mobile editionRead on a mobile device

Liquid, gaseous or solid biofuels hold great promise to deliver an increasing share of the energy required to power a new global green economy. Many in government and the energy industry believe this modern bioenergy can play a significant role in reducing pollution and greenhouse gases, and promoting development through new business opportunities and jobs. Modern bioenergy can be a mechanism for economic development enabling local communities to secure the energy they need, with farmers earning additional income and achieving greater price stability for their production.

 

Third generation photovoltaic cell

From Wikipedia, the free encyclopedia

    

Third generation photovoltaic cells are solar cells that are potentially able to overcome the Shockley–Queisser limit of 31-41% power efficiency for single bandgap solar cells. This includes a range of alternatives to the so-called "first generation solar cells" (which are solar cells made of semiconducting p-n junctions) and "second generation solar cells" (based on reducing the cost of first generation cells by employing thin film technologies). Common third-generation systems include multi-layer ("tandem") cells made of amorphous silicon or gallium arsenide, while more theoretical developments include frequency conversion, hot-carrier effects and other multiple-carrier ejection.
^{[1] [2][3][4]}

Background

Solar cells can be thought of as visible light counterparts to radio receivers. A receiver consists of three basic parts; an antenna that converts the radio waves (light) into wave-like motions of electrons in the antenna material, an electronic valve that traps the electrons as they pop off the end of the antenna, and a tuner that amplifies electrons of a selected frequency. It is possible to build a solar cell identical to a radio, a system known as an optical rectenna, but to date these have not been practical.

Instead, the vast majority of the solar electric market is made up of silicon-based devices. In silicon cells, the silicon acts as both the antenna (or electron donor, technically) as well as the electronic valve. Silicon is almost ideal as a solar cell material; it is widely available, relatively inexpensive, and has a bandgap that is ideal for solar collection. On the downside it is energetically expensive to produce silicon in bulk, and great efforts have been made to reduce or eliminate the silicon in a cell. Moreover it is mechanically fragile, which typically requires a sheet of strong glass to be used as mechanical support and protection from the elements. The glass alone is a significant portion of the cost of a typical solar module.

According to the Shockley–Queisser limit, the majority of a cell's theoretical efficiency is due to the difference in energy between the bandgap and solar photon. Any photon with more energy than the bandgap can cause photoexcitation, but in this case any energy above and beyond the bandgap energy is lost. Consider the solar spectrum; only a small portion of the light reaching the ground is blue, but those photons have three times the energy of red light. Silicon's bandgap is 1.1 eV, about that of red light, so in this case the extra energy contained in blue light is lost in a silicon cell. If the bandgap is tuned higher, say to blue, that energy is now captured, but only at the cost of rejecting all the lower energy photons.

It is possible to greatly improve on a single-junction cell by stacking extremely thin cells with different bandgaps on top of each other - the "tandem cell" or "multi-junction" approach. Traditional silicon preparation methods do not lend themselves to this approach. There has been some progress using thin-films of amorphous silicon, notably Uni-Solar's products, but other issues have prevented these from matching the performance of traditional cells. Most tandem-cell structures are based on higher performance semiconductors, notably gallium arsenide (GaAs). Three-layer GaAs cells hold the production record of 41.6% for experimental examples.^[5]

Numerical analysis shows that the "perfect" single-layer solar cell should have a bandgap of 1.13 eV, almost exactly that of silicon. Such a cell can have a maximum theoretical power conversion efficiency of 33.7% - the solar power below red (in the infrared) is lost, and the extra energy of the higher colors is also lost. For a two layer cell, one layer should be tuned to 1.64 eV and the other at 0.94 eV, with a theoretical performance of 44%. A three-layer cell should be tuned to 1.83, 1.16 and 0.71 eV, with an efficiency of 48%. A theoretical "infinity-layer" cell would have a theoretical efficiency of 64%.^[

Home electricity use in US falling to 2001 levels

Dec 30, 2013 by Jonathan Fahey on phys.org
Read more at: http://phys.org/news/2013-12-home-electricity-falling.html#jCp

             

 

 

 

 

 

 

 

This combination of Associated Press file photos shows, left, a Cingular "Fast Forward" cradle and Motorola mobile phone in New York on Tuesday Nov. 4, 2003, and an Apple ultracompact USB Power Adapter, on Friday, Sept. 19, 2008, in New York.

The average amount of electricity consumed in U.S. homes has fallen to levels last seen more than a decade ago, back when the smartest device in people's pockets was a Palm pilot and anyone talking about a tablet was probably an archaeologist or a preacher.

Because of more energy-efficient housing, appliances and gadgets, power usage is on track to decline in 2013 for the third year in a row, to its lowest point since 2001, even though our lives are more electrified.

 

Here's a look at what has changed since the last time consumption was so low.

BETTER HOMES

 

In the early 2000s, as energy prices rose, more states adopted or toughened building codes to force builders to better seal homes so heat or air-conditioned air doesn't seep out so fast. That means newer homes waste less energy.

 

Also, insulated windows and other building technologies have dropped in price, making retrofits of existing homes more affordable. In the wake of the financial crisis, billions of dollars in Recovery Act funding was directed toward home-efficiency programs.

 

BETTER GADGETS

Big appliances such as refrigerators and air conditioners have gotten more efficient thanks to federal energy standards that get stricter ever few years as technology evolves.

A typical room air conditioner—one of the biggest power hogs in the home—uses 20 percent less electricity per hour of full operation than it did in 2001, according to the Association of Home Appliance Manufacturers.

       

This combination of Associated Press file photos shows, top, Switch75 light LED bulbs in clear and frosted, on Tuesday, Nov. 8, 2011 in New York and a 100-watt incandescent light bulb at Royal Lighting in Los Angeles on Jan. 21, 2011. LEDs.



 

Central air conditioners, refrigerators, dishwashers, water heaters, washing machines and dryers also have gotten more efficient.

 

Other devices are using less juice, too. Some 40-inch (1-meter) LED televisions bought today use 80 percent less power than the cathode ray tube televisions of the past. Some use just $8 worth of electricity over a year when used five hours a day—less than a 60-watt incandescent bulb would use.

 

Those incandescent light bulbs are being replaced with compact fluorescent bulbs and LEDs that use 70 to 80 percent less power. According to the Energy Department, widespread use of LED bulbs could save output equivalent to that of 44 large power plants by 2027.

The move to mobile also is helping. Desktop computers with big CRT monitors are being replaced with laptops, tablet computers and smart phones, and these mobile devices are specifically designed to sip power to prolong battery life.

It costs $1.36 to power an iPad for a year, compared with $28.21 for a desktop computer, according to the Electric Power Research Institute.  

 

ON THE OTHER HAND...

We are using more devices, and that is offsetting what would otherwise be a more
dramatic reduction in power consumption.

       

This combination of Associated Press file photos shows, top, a house in Duluth, Minn.,with triple-paned, south-facing windows that draw heat from the sun, and bottom an undated photo provided by Lowe's shows weatherstripping being applied.

 

 DVRs spin at all hours of the day, often under more than one television in a home. Game consoles are getting more sophisticated to process better graphics and connect with other players, and therefore use more power.

More homes have central air conditioners instead of window units. They are more efficient, but people use them more often.

Still, Jennifer Amman, the buildings program director at the American Council for an Energy-Efficient Economy, says she is encouraged.
   
    In this combination of Associated Press file photos, a man, top, looks at the back of a
   Sony's 4K XBR LED television in Las Vegas, on Monday, Jan. 7, 2013. and bottom, a
   man ooks at a CRT television in Redwood City, Calif., on Wednesday, Oct.

"It's great to see this movement, to see the shift in the national numbers," she says. "I expect we'll see greater improvement over time. There is so much more that can be done."

The Energy Department predicts average residential electricity use per customer will fall again in 2014, by 1 percent.