Keeping roofs cooler to cut energy costs

A simple paint-on coating might cut home energy use and urban pollution, a teen’s research suggests.

PITTSBURGH, Pa. — The roof of a house can get pretty hot in the summer. Even if there is an insulated attic below, some of that heat can work its way into the living space. That can make air conditioners work harder and pump up electricity bills. But a thin, paint-like coating could help keep roofs cooler, a teen researcher finds. And in urban areas, widespread use of her new roofing treatment might even cut the formation of lung-irritating ozone on hot days.

Shingles come in many colors, but dark ones are especially popular, says Jesseca Kusher. The 18-year old attends Spartanburg Day School in South Carolina. Like most dark objects, shingles absorb a lot of heat from sunlight. In the summer sun, they can easily reach 73.5° Celsius (164° Fahrenheit), she notes. If those shingles reflected more sunlight, they’d stay cooler. And that could help cut down on home cooling bills. According to the Environmental Protection Agency, air conditioning consumes about 5 percent of all the energy used in the United States. Cooling buildings costs the nation about $11 billion each year.

So Jesseca looked into ways to make shingles reflect more light. She mixed tiny particles — a powder — made from any of several different substances into a clear paint-like coating. One coating got graphite, the same material in pencil lead. Another recipe included gypsum. That’s a soft mineral often found in the drywall used in construction. She even tried adding mica. That’s a mineral used in some lampshades. It readily breaks into small, glittering flakes.

Each of these powders came in several colors. In each of Jesseca’s test recipes, her reflective powder accounted for 40 percent of the weight of the final mixture. She also prepared some of the paint-like coatings with no additive. That would let her judge whether a powder — versus the transparent goop it was added to — affected a shingle’s reflectivity, she explains.

Jesseca used four different colored shingles. She painted each of her concoctions onto bits of each color of shingle and let them dry for 24 hours. Then, to simulate how the shingles would heat up in summer, she placed each postage-stamp-size sample under a 150-watt sun lamp. (Those bulbs send out radiation across a wide band of wavelengths, similar to those emitted by the sun.) Each test sample was irradiated for 15 minutes, or until the untreated shingles reached a temperature of 73.5 °C, whichever came first. To measure how hot each sample got, the teen used an instrument that measures the infrared radiation (heat) emitted by an object.

3-D Recycling: Grind, melt print!

A new desktop recycler turns trash into 3-D printer ‘ink'.

Three-dimensional, or 3-D, printers make it possible to “print” almost any object with a computer. The machines produce items by laying down tiny drops, or pixels, of material one layer at a time. That material can be made from plastic, metal or even human cells. But just as the ink for standard computer printers can be expensive, 3-D printer “ink” can be quite pricey too. Meanwhile, society faces a growing mound of plastic trash. Now three Canadian engineering students have found a way to deal with both problems: Recycle plastic waste into spools of 3-D printer ink. 

The first part of their new machine is a plastic recycler. It grinds and crushes waste plastic into uniform bits about the size of peas or large grains of rice. The waste can be used drink bottles, coffee cup lids or other plastics. But this trash must be clean.

Users must grind only one type of plastic in any given batch. Otherwise, the ink-making part of the process may not work well, notes Dennon Oosterman. He worked on the new machine with fellow students Alex Kay and David Joyce. All three attend the University of British Columbia in Vancouver, Canada.

The machine stores the plastic bits in a drawer until there are enough for a spool of “ink.” Then those bits go into the next part of the machine. It’s called an extruder.

To extrude something means to push it out. To do that, this part of the system first melts the plastic bits. A little of that melted plastic attaches to a spool. The spool then turns, pulling a long, thin thread of the plastic out of the machine. “You can think about stretching gum apart,” explains Oosterman. But instead of becoming a mess of stringy goo, the plastic cools and winds neatly onto the spool.

The machine pulls out and winds as much as three meters (10 feet) of plastic thread per minute. At that rate, it takes roughly two hours to make a one-kilogram (2.2 pound) spool of plastic thread. That’s about 40 percent faster than other small-scale plastic-ink makers, Oosterman says.

‘Smart’ clothes generate electricity

New fabric harvests energy from its wearer.

You’ll get a charge out of the clothes of the future. Scientists in South Korea have developed a flexible, foldable and wearable fabric that generates electricity as it bends and flexes. A person wearing a shirt tailored from the material only has to move around to power a small screen or other electronic devices.

The advance represents an important step toward making wearable power sources a reality, says Yunlong Zi. He’s a physicist at the Georgia Institute of Technology, in Atlanta, who did not work on the new fabric. In his own lab, he studies ways to harvest energy. “Cell phones need batteries, but batteries have limited life,” he notes. With clothing that can generate electricity, he notes, that’s no longer an issue: “You can make power by yourself.”

Sang-Woo Kim led the development of this new material. He works at Sungkyunkwan University in Suwon, South Korea. A shirt made from the new fabric can be worn — even patched — like any other item of clothing. “It feels like an ordinary jacket,” he told Science News for Students.

Fully equipped, it's just a tad on the heavy side, he acknowledges. That added weight comes from the electronic gizmos the researchers wired into the shirt. For tests, these included small screens, lights and even a keyless remote. Press the shirt’s cuff, for instance, and the remote unlocks a car's doors.

How it works

The power-generating material is known as a wearable triboelectric (TRI-bo-ee-LEK-trik) nanogenerator, or WTNG. Here’s what that means: Triboelectricity refers to electricity generated by friction. Friction is the resistance encountered when one material moves over or through another material. People feel friction (in the form of heat) when they rub their hands together. In fact, the prefix tribo comes from the Greek word for rubbing. Meanwhile, nano is a prefix meaning a billionth. The material includes tiny zinc-oxide rods only billionths of a meter long. Those spiky nanoparticles help convert motion into electricity.

The Eiffel Tower Goes Green

The Eiffel Tower, built in 1889, was created with the sole intention of acting as the entrance to the 1889 World’s Fair, meant to last only a few years. Paris’s most iconic landmark has seen various additions and decorations for holidays and events in its 126 year life span, but it’s latest renovation is a new symbolic and practical addition. Last week, Urban Green Energy, a renewable energy firm, installed two wind turbines near the second level of the tower within the metal scaffolding. The turbines will produce 10,000 kilowatts per hours, enough to offset all the electricity used on the first floor, which includes restaurants, a souvenir shop, and historical exhibits, in a given year.

According to CNET, the vertical axis turbines are installed 400 feet from the ground, a height meant to optimize the amount of wind (from any direction) captured. The turbines will not be a sight for sore eyes or ears either; they have been specifically painted to blend in with the tower and the sound produced by the turbines registers at about 40 decibels, or the sound of a whisper.

The tower’s architecture was better suited for wind energy rather than solar power. “Being up on the tower, it was very evident wind was the right choice,” Jan Gromadzki, an engineer for UGE, told Fast Company. “We're so far up above the rest of Paris that we actually get very strong winds, very powerful winds that can be used and harnessed to produce energy. Solar would have required quite a bit of space, which they really don't have on the tower. It would also look like glass, and they didn't want to cover any of the structure.”

'Smart’ windows could save energy

Tiny droplets sandwiched between glass panes turn cloudy when it’s hot outside; this filter out some warming sunlight.

 

 
Sunlight streaming through a window can really heat up a room. In winter, when heating bills can soar, people tend to welcome that extra warmth. But in summer, that heat just boosts cooling costs. A homeowner could keep out some of that warming light by drawing the curtains or lowering the blinds. Or the window could change its transparency — blocking out some light, as needed — all by itself. That’s the idea behind new “smart” windows.

Some smart windows already exist. They work just like large versions of the LCDs (liquid crystal diodes) found in watches and other electronic devices. When an electric current flows through an LCD window, a coating on the panes of its glass darken. That blocks out some of the light. A homeowner can control the window’s light-blocking ability — or opacity — simply by flipping a switch. Or, a sensor connected to the window can automatically control the current, just like the thermostat used to control a furnace or air conditioner.

But the new smart window does not require such electronics. It depends only on the temperature outdoors, says Xuhong Guo. He’s a chemical engineer at the East China University of Science and Technology in Shanghai. His team designed a new liquid that it sandwiches between two panes of window glass. The researchers describe how this makes their window “smart” in the December 3 issue of Industrial & Engineering Chemistry Research.

The key: A heat sensitive gel

The material that Guo’s team designed is a colloid. That’s a substance in which tiny particles or droplets that don’t dissolve are spread throughout a larger volume of some other material. (Smoky air is one type of colloid. Milk is another.) The larger part of the new mix is a blend of water and alcohol. Floating inside are tiny globs of a gel.

Each glob is only between 200 and 700 nanometers across. That makes the diameter of the thinnest human hair about 24 to 85 times wider than each glob. The gel contains a heat-sensitive polymer (a chemical made from chain-shaped molecules). It also contains water and glycerol, a type of alcohol. The water and glycerol attach loosely to the polymer. This keeps the gel from dissolving into the larger volume of liquid. This also ensures that the gel globs don’t react with each other to form one big lump of goo.

Picture This: Christmas from space

Satellites survey human behavior by snapping pictures of holiday lights.

 

SAN FRANCISCO — Evening trips to the mall. Christmas parties. Rooftop lights. The December holidays are bright — dazzling enough to be seen by satellites orbiting high above Earth. Researchers recently used satellite data to track when, where and how often we turn on lights. The findings, they say, point to how human activities drive electricity use.

Scientists sent radiometers into space and pointed them toward Earth. These instruments measure the intensity of light. In 2012, the research team released a set of “Earth at Night” maps. They had used data collected on nights with ideal conditions — evenings that were both moonless and cloud-free.

Miguel Román is a physical scientist at NASA Goddard Space Flight Center in Greenbelt, Md. He and his team wanted to analyze how light patterns change from day to day. To do that, his team improved its scans so that the scientists could collect data even on nights with clouds and a bright moon. (Unfortunately, the system can’t cope with snow. Light reflecting off the white stuff “contaminates the signal,” Román says.)

From 2012 to 2014, the satellite snapped daily pictures of 70 U.S. cities. The scientists used those images to measure how much the cities brightened between Thanksgiving and New Year’s Day. They compared the cities’ holiday glow to their light output the rest of the year.

It was “a huge effort,” says Román. “It took three years’ worth of data.” But with the team’s revamped system, “we can do comparisons across cities, even across neighborhoods within cities,” Román says. He described his group’s new findings December 16 at the fall meeting of the American Geophysical Union.

Many cities radiated 20 to 50 percent more light during holiday nights, the researchers found. The light intensity climbed a bit more in the suburbs than in busy city centers. But overall, it seems that everyone in the United States — regardless of income or ethnic background — celebrates the holidays, Román says.

A different picture emerged when his team analyzed another part of the world: the Middle East. There, the major holiday is Ramadan. It’s the ninth month of the Islamic calendar. On those 30 days, Muslims fast from dawn to dusk.

Five ways to keep your home warm this winter

If you live in a poorly insulated home, and many of us do, you could spend thousands this winter on energy bills. But our ancestors had many ways to keep snug at little or no cost. Now, thanks to modern infrared cameras and advances in environmental physics, we can understand how these methods work and measure how effective they are.

The key to understanding how to keep warm is the fact you lose more heat by radiation to your surroundings than you do by convection to the air. This is why your house feels so cold when you get back from a winter break, even after you’ve turned on the central heating; though the air quickly warms up, the walls take far longer to do so and may continue to make you shiver for up to a day.

In the same way, in poorly insulated houses the inside of the external walls can be several degrees colder than the air and the internal walls, making you feel chilly.

Fortunately, there are five simple ways to overcome this and minimise your energy bills.

Close your curtains at night

During the day, your windows let in more radiant energy than gets out; sunlight can enter through the glass, but the window is opaque to the infrared radiation trying to escape. At night, however, single-glazed windows can get extremely cold – in my Victorian house which we try and keep at a room temperature of 20°C, an infrared camera showed internal window temperatures of as low as 7°C on a frosty night.

Even double-glazed windows aren’t great insulators and can fall to around 14°C. This results in energy losses of 50-100 watts per square metre, equivalent to running an old-fashioned light bulb.

Look out behind the bus stop, here come guerrilla gardeners digging up an urban revolution

Lurking beneath the authorities' radar is a vast, international underground movement that stretches from Africa and Europe to the Americas: guerrilla gardening, the un-permitted colonisation of land, is still a mysterious activity about which little research is undertaken.

The movement brings together students, academics, businessmen, planners, architects, chefs, community workers and many more professions making up the ranks. Would-be guerrillas can enlist in a troop online through sites such as guerrillagardening.org; a forum established by Richard Reynolds (“Britain’s 24th most influential gardener”), deemed the father of the modern guerrilla gardening movement. The movement has grown in recent years, fuelled partially by the rise of Twitter and other forms of social media which make it much easier to organise digs.

Generally speaking, guerrilla gardeners either aim to beautify a neglected patch of land or, increasingly, pursue the cultivation of space via urban agriculture by growing fruit and vegetables in a city context. A somewhat famous example of this is Incredible Edible Todmorden, a guerrilla gardening project started in 2008 where residents “adopt” areas of the town and plant without permission. Impressed by the displays and ideas, the local authority started to work with the guerrillas and the Incredible Edible Network was soon born – now an international movement promoting the idea of urban agriculture.

Air conditioning raising night-time temperatures in the US

Heat from cooling systems now raises some urban temperatures by more than 1C at night, reports Climate News Network.

Researchers in the US have identified a way in which city-dwellers are inadvertently stoking up the heat of the night – by installing air conditioners.

Because the cities are getting hotter as the climate changes, residents are increasingly investing in aircon systems − which discharge heat from offices and apartment blocks straight into the city air. And the vicious circle effect is that cities get still warmer, making air conditioning all the more attractive to residents.

According to scientists at Arizona State University, the air conditioning system is now having a measurable effect. During the days, the systems emit waste heat, but because the days are hot anyway, the difference is negligible. At night, heat from air conditioning systems now raises some urban temperatures by more than 1C, they report in the Journal of Geophysical Research Atmospheres.

The team focused on the role of air conditioning systems in the metropolitan area of the city of Phoenix, which is in the Sonora desert in Arizona, and conditions in the summertime are harsh there anyway.

Digital lighting goes organic

Research reveals a bright future for a new lighting technology.

 

Flick on a light at home and chances are a glass bulb or tube will start to glow. The two most common types of electric lights — incandescent and fluorescent — have worked pretty well for a long time. Make that too long: Both types are so last century.

Incandescent bulbs waste most of their energy. Regular and compact fluorescent tubes are more efficient. However, they contain toxic mercury. Now lighting engineers want us to imagine electric lighting beyond the bulb.
Picture sheets of electric lights that can bend or twist. Your bedroom could have glowing sculptures instead of lamps. A living room window might be transparent by day, then light up at night. The whole kitchen ceiling might glow. And whole walls could be covered with programmable lighting. A few taps on a control panel might change its brightness, color or pattern.

 

It’s all possible with organic light-emitting diodes, or OLEDs. They are a new type of digital — or solid-state — lighting. Made from solid materials, they don’t require the vacuum now found in an incandescent bulb or the gas that’s encased within fluorescent tubes.

Green or white? Planted or painted roofs can cool buildings

It’s getting hot in the city, and our overheated cities are only going to get hotter still as more people pile in and development and energy use intensifies. But planting away the problem could be a surprisingly low-cost solution to create cool roofs that will reduce office temperatures and improve working conditions for millions.

As more people move into urban areas and the effects of climate change steadily increase, it’s not surprising that urban warming is projected to worsen in the future.

One means to counteract this heat and cool things down is through planting various types of vegetation to form a green roof. Another option is to paint roof surfaces white, as is common in the Mediterranean, known as a cool roofs.

These simple measures can help reduce the urban heat island effect, where built-up areas experience higher air temperatures than rural areas due to higher-density buildings that trap heat. As you’d expect, this leads to more overheating and energy use (from use of air conditioning) within buildings during the summer, and less energy needed for heating during winter.

How to teach ... Earth Hour

Millions of people will switch off their lights on Saturday for Earth Hour, a campaign to raise awareness of climate change and environmental issues.

Whether it's researching the famous landmarks that take part, discussing ways of saving energy or investigating endangered species, we have plenty of teaching resources to ensure that pupils won't be left in the dark.

Get started with this Earth Hour assembly presentation. It encourages pupils to think about some of the environmental challenges the world is facing and steps they can take to help. Pupils can then test their knowledge of endangered species in this PowerPoint quiz.

WWF, the organisers of Earth Hour, have also created a support pack for schools. It contains a range of ideas to get pupils thinking about their own environmental concerns. In one activity, pupils write a wish for the planet's future on a star that can be cut out, decorated and used to make a display of the night sky featuring animal-shaped constellations.

In another activity, pupils learn about endangered species using a selection of fact sheets. Working in groups, pupils must find an engaging way of sharing information about their animal with the rest of the class. Ideas include playing a "Who am I?" guessing game or making a PowerPoint presentation. As a homework activity, pupils can use these templates to create fact sheets about either the snow leopard, African elephant or bottlenose dolphin. Additional templates for the mountain gorilla, polar bear and hawksbill turtle are available on the Earth Hour website.

Carbon as a commodity: a trade in pollution could help clean up dirty economies

We pay for the product, but not the carbon cost. Kin Cheung/AP

Is it fair that China is blamed for the carbon dioxide emissions it generates to manufacture products destined for the West? Would the West do more to reduce greenhouse gases if it had to pay for the emissions caused in producing the products it imports? Welcome to the world of carbon accounting, where changes to the way the books are kept could improve our chances of driving down greenhouse gas emissions worldwide.

Carbon dioxide emissions from burning fossil fuels such as coal, oil and gas have soared. In 2013 they were more than 60% higher than in 1990. This is despite significant progress in global climate policy, with numerous international agreements promising emission cutbacks.

This contradiction reflects the structure of most international agreements: industrialised countries are allotted emissions targets while developing countries are not. Unsurprisingly, emissions have largely stabilised in the countries with targets to meet, and more than doubled in countries without them. China has seen the largest amount of emissions growth and now emits more carbon dioxide per person than the entire European Union.

Run, don’t walk’: The school that gets pupils to generate electricity

Special floor tiles produce sustainable energy when pupils pound them

In a reversal of normal classroom rules, students have been encouraged to run and jump around a corridor at a Kent school.

It’s because the corridor has been laid with special kinetic tiles and every footstep on them creates sustainable energy.