The Switch: America’s electrical grid

Boulder Dam wires. Photo by Ansel Adams, from U.S. National Park Service.

Boulder Dam wires. Photo by Ansel Adams, from U.S. National Park Service.

The nation’s electric grid touches every aspect of our lives. But few of us give it a second thought. Until something goes awry – when we’re suddenly groping in the dark for flashlights, worrying about what might spoil in the fridge.

Consider this: the average customer loses power for 214 minutes per year, according to a study by Carnegie Mellon that found the United States ranks toward the bottom among developed nations in terms of the reliability of its electricity service.

BURN’s new hour-long special “The Switch” is about our aging electric power grid: a half century-old patchwork system – stretched to capacity – that transmits and distributes electricity from plants to consumers.

Host Alex Chadwick and BURN’s producers and reporters explore how the grid works, and what happens when it breaks under storms and floods.

We talk to the people who help fix it, a family that’s left the whole thing behind, and the innovators working to make our national grid safer and smarter.

Click here for photos, video and more from BURN’s special The Grid.

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The Electrical House That Jack Built

The Milwaukee Electric Railway and Light Co. published The Electrical House That Jack Built – a 1916 pamphlet showing how electrical appliances were transforming life in the home. Written in verse to parody the well-known nursery rhyme and illustrated with drawings resembling children’s books of the period, it celebrates the convenience, comfort and health enjoyed by users of electrical appliances. Images are courtesy of the Wisconsin Historical Society.

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When it rains, it floods: Hoboken underwater

A Hoboken street and power station partly flooded. Photo:  Donna Ferrato.

A Hoboken street and power station partly flooded. Photo: Donna Ferrato.

 

Alex Chadwick, BURN Host

The next BURN special is about what keeps us all going, except when it doesn’t: the grid. That’s the term for the complicated, interconnected electrical power system that runs so many of the machines that power our lives. The grid makes i-everything possible.

But it is old, and in many places frail. The city of Hoboken, New Jersey, is subject to flooding even in normal heavy rains. But it never saw anything like what happened last October when Hurricane Sandy hit. Parts of the city were without power for ten days. Now Hoboken is working to build a new, smarter grid for itself – in part, an official told me, because the big lesson the city learned from the storm was that by the time the next big storm hits, Hoboken will have to be ready to save itself.

The city partly flooded twice in the last month from rain storms. Now it’s late May, and after recent heavy rains, the city is partly flooded again.

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There’s power, and then there’s power

Robert Rand, BURN Editor

When you think about political power, electricity probably isn’t the first thing that comes to mind. But when you think about the ability – or more importantly, the inability – of a government to deliver electricity to its citizens, the political nature of energy transmission becomes clear.

Ask any mayor or governor who worries about the wrath of constituents during extended power outages, such as those that occurred last year during Hurricane Sandy. The politics of Sandy were captured in this headline from the Associated Press: “Sandy a Super Test for Bloomberg, Christie, Cuomo.”

Lenin and electrification

One of the first politicians to grasp the political nature of electricity was neither from New York nor New Jersey. He was Vladimir Ilych Lenin, founder of the Soviet Union. In the early years of the USSR the new Bolshevik government faced the daunting challenge of extending control over the vast Russian landmass. Lenin framed the issue this way: “Communism is Soviet power plus the electrification of the whole country.”

Lenin understood that a government is as good as its grid. The ability to provide a reliable source of electricity is one of the most important measures of effective state governance. Lay a electrical grid across the land and the people will be satisfied and prosper.

In prosperous, developed countries, the grid is so well-established and electricity so plentiful that it’s taken for granted. Fail to lay down a reliable grid, or fail to make quick repairs when the power goes out, and a government’s credibility may tatter, with political, economic and social consequences to follow.

Which makes an event in the Middle East last week especially interesting.  It happened in Syria, which is embroiled in a God awful civil war that has claimed more than 70,000 lives. Syria’s president, Bashar al-Assad, has spent most of the past few months hunkered down in the presidential palace in Damascus.

Mideast SyriaLast Wednesday, Assad made a rare public appearance. He visited a power station in the city center.

Al-Assad’s message: Don’t worry, be happy. I can deliver electricity to the people of Damascus. I still have political power.

The problem, of course, is the conundrum Assad will face if anti-government fighters manage to turn off the lights.

This summer, BURN will feature a one-hour radio and multimedia special on our nation’s electrical grid system – how it was built, how it works, and what happens when it doesn’t. Follow us here, on Facebook, SoundCloud, and Twitter all next month to hear great excerpts, see photos, and learn more about America’s grid.

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Rome BURNS: Italy’s power grid, taken by storni

Robert Rand, BURN Editor 

Not long ago, as Rome passed through the final weeks of winter, a swirling black cloud flew in from the hills outside the city just before sunset. It whorled in the skies over my neighborhood, elegantly dancing to and fro and inside out. I’d never seen anything like it. My daughter thought it was a tornado. I was mesmerized. The whole thing seemed extraterrestrial.

The show took place every day in the late afternoon for more than a week. The performers were flocks of European starlings — gli storni – come to roost in Rome and elsewhere in Italy by the many, many thousands.

Despite the beauty of their aerobatics, the starlings are not particularly welcomed here.

There are some obvious reasons.

starlings-italy

A more subtle and serious effect is the occasional blackout caused by way too many birds perching on electric power lines all at the same time. In the town of Brindisi, in the heel of southern Italy, outages once resulted when an army of starlings simultaneously took flight from their power line roost, triggering oscillations that interrupted the flow of electricity.

In Fasano, about a hundred miles north of Brindisi, the combined weight of the starlings caused high tension wires – in the words of a local newspaper – to be “sent into a tailspin.” In the Tuscan town of Montecarlo, a newspaper reported frequent blackouts and called the starlings “a scourge.” The city urged hunters to take up arms.

I checked with Terna, the Italian transmission grid operator, and was told that Rome did not experience any starling-induced blackouts this year. The city has used loudspeakers and light projectors to repel the birds with some success. A Terna spokesperson did point out that the company works with environmental groups to study the interaction between high-voltage lines and birds. One objective is to minimize avian collisions.

More than 9,000 special noise-making “dissuaders” – like this one – have been installed on the Italian grid to make power lines easier to see by birds in flight.

Bird grid dissuader

 

Here is Terna’s 2011 “Sustainability Report.”

By the way, “murmuration” is the word used to describe an airborne starling ballet. Daniel Butler, a writer for the Telegraph, described the science behind it this way:

Each bird strives to fly as close to its neighbours as possible, instantly copying any changes in speed or direction. As a result, tiny deviations by one bird are magnified and distorted by those surrounding it, creating rippling, swirling patterns. In other words, this is a classic case of mathematical chaos (larger shapes composed of infinitely varied smaller patterns). Whatever the science, however, it is difficult for the observer to think of it as anything other than some vast living entity.

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What goes down: Stein’s Law and the cost of energy

Carey King, BURN Contributor

Stein’s Law states: “If something cannot go on forever, it will stop.”

For nearly 60 years after World War II, the percent of U.S. household income spent on food and energy – or personal consumption expenditures (PCE) – declined.

But then things started to change. Again. Between 1998 and 2002, PCE for food and energy stopped declining and started increasing. The PCE for “food + energy” reached a minimum of 18% in 2002. Whether or not this will be the minimum percentage PCE for “food + energy” for the US for all time is a good question.

But this percentage cannot decrease forever because energy and food will never be free – back to Stein’s Law. As we’ll see shortly, the reversal of these trends could be an indicator of a fundamental transformation for our economy and society.

Carey King - Food_Energy chart

Figure 1. Personal consumption expenditures of US households expressed as a percentage of total expenditures. Data are from the US Bureau of Economic Analysis Table 2.3.5. Food = “Food and beverages purchased for off-premises consumption” and “Food services and accommodations.” Energy = “gasoline and other energy goods and of electricity and gas.”

The reason to consider both the PCE for energy and food is because food was fundamentally an energy source of pre-industrial power from humans and animals. Before fossil fuels and significant industrialization using wind, wood, and water power in the early 1800s, food was the major energy resource for prime movers.

The food that animals and people ate was the fuel that powered them, and therefore the machines and tools they operated. Thus, the quantity of food and fodder produced from the land had a major influence on the amount of power for agriculture and a little industry.

In a large sense, fossil fuels and subsequent technologies drove down the relative cost of food and energy. Those energy-dense resources enabled the technical change that generated economic growth. Fossil fuels also meant fewer and fewer workers were needed to grow food and mine energy sources.

Since 2002, we have been spending an increasingly higher proportion of our personal income on food and energy, due to resource scarcity. Thus, there has been an increased demand for more investment (capital and labor) in these basic needs.

In other words, food and energy have become increasingly scarce – and therefore, more expensive – because of the rising demands for each around the world.

As a result, an increasing proportion of workers and other resources may be needed to produce the same quantity of food and energy (fossil and renewable), possibly with declining per capita consumption. This is the exact opposite trend of fossil-fueled industrialization!

The truth is that constraints in food and energy supplies, together with consumption patterns (and demographics, too, but that’s another subject) have caught up with much of the ‘advanced’ economies (e.g. EU, US, Japan). Unconventional oil alternatives – oil sands, deepwater, oil shale, biofuels – don’t have the same level of pure energetic value as energy sources of the past.

In considering the ongoing debate about American jobs and decreasing unemployment rates, note how the oil and gas commercials tout the jobs they create. Then, remember the figure in this article. Historically, the economy has grown the most when we’re moving jobs out of the energy sectors.

The rising cost of energy is a primary cause of our slow economy, and there is a limited rate at which we can adjust to this new reality. The sooner citizens, businesses, and politicians accept this fact, the better we will be in the future.

Carey King is a research associate in the University of Texas at Austin’s Center for International Energy and Environmental Policy. King researches energy systems and how they work together and within the environment. King contributes blog posts for Environmental Research Web, under Energy – The Nexus of Everything.

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Wind Science, Energy, and Growing Prevalence

Wind is the kinetic energy of molecules in the air. Wind has powered ships and mills for centuries or longer.

Modern windmills convert the wind into rotational energy by allowing the air molecules to bombard the blades, turning them. The blades are connected to turbines, which generate electricity from that rotational energy.

Wind energy is one of the cleanest forms of energy available because it doesn’t require a fuel or produce greenhouse gas or other bi-products, outside of those from production and maintenance of equipment and transmission.

Wind turbines themselves take up only a small area compared to their generating potential, making it possible to install them on agricultural, forest, or grazing lands.

RAPID GROWTH

In just ten years, wind power in the United States grew more than ten-fold, from just over 2,000 megawatts in 1999 to more than 34,000 megawatts in 2009, when wind accounted for 9 percent of renewable energy produced in the country and more than geothermal and solar combined.

Here’s an animated map of wind development from 2000 to 2010.

Texas, Iowa, and Minnesota had the greatest wind capacity in 2010. Additionally, at least 27 other states used wind to generate electricity that year.

DRAWBACKS TO WIND ENERGY

Wind is an intermittent resource, meaning that the windmills can’t continuously and predictably produce energy. They only work when the wind blows, and they can only work as hard as the wind is blowing at that time.

Research is ongoing into predicting what regions of the country have significant wind resources suitable for wind development, a process that requires computer programming and meteorological knowledge.

Furthermore, public and private researchers are working to produce better models of wind on an hourly, daily, and seasonal basis to make it easier for wind energy producers to forecast their output and sell it ahead of time.

Another major hurdle to wind power is that it is expensive compared with fossil fuel-based electricity. Modern windmills cost a lot to design and build, especially as they have to be strong enough to endure extreme weather, even though they will mostly operate in moderate weather. That makes competing with other energy sources difficult without government intervention.

Some people don’t like the way windmills look, and windmills can also kill bats and birds, though newer designs have slower and less deadly blades. A 2010 study published in the Journal of Ornithology estimated that windmills kill around 440,000 birds every year. However, the same study showed that house cats kill more than 1,000 times that number, as many as 500 billion per year.

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The Hydrogen Economy, Hydrogen Sources, and the Science Behind These

The hydrogen-filled Hindenburg in 1936 or 1937. Photo from DeGolyer Library at Southern Methodist University.

THE HYDROGEN ECONOMY

The hydrogen economy is a hypothetical future in which energy can be bought, sold, stored, and transported in a currency of hydrogen, much like today’s energy is often exchanged in electricity. Because hydrogen doesn’t need to be attached to the electricity grid, it can be used in forms of transportation like buses and cars.

The end-user of the hydrogen, for example an automobile driver, doesn’t experience significant pollution beyond the formation of water from burning the hydrogen.

For more details about the hydrogen economy see here.

Hydrogen, a gas, isn’t a fuel like gasoline or coal; hydrogen is a way to store and transport energy made from other fuels, like a battery or electricity. Unlike fossil fuels, pure hydrogen isn’t stable, so forming hydrogen in the first place requires energy and produces carbon dioxide, and storing hydrogen involves special considerations because this light gas is very flammable and also quickens rust and oxidation in pipelines and storage containers.

HOW HYDROGEN IS DIFFERENT FROM FOSSIL FUELS

Allowing hydrogen (a gas) to burn in the presence of oxygen releases that stored energy in the form of heat. Hydrogen can also be reacted in a fuel cell to produce electricity. In either case, electricity or heat can then be used to power cars or any number of other devices. Gasoline, biofuels, wood, and other carbon-based fuels all produce carbon dioxide when they are burned, and rising carbon dioxide levels are widely implicated in climate change. Burning hydrogen produces energy, water and a few trace compounds, but it doesn’t produce carbon dioxide.

2 H2 (hydrogen gas) + O2 (oxygen gas) = 2 H2O (water vapor) + energy

It’s unclear what widespread emission of water vapor could do. According to recent published estimates, atmospheric water vapor is responsible for 75 percent of the greenhouse effect. However, water vapor can condense, and it’s naturally-occurring in the atmosphere. It is much easier to trap and transform to liquid than the carbon dioxide normally emitted by burning gasoline. Carbon dioxide won’t form a liquid at atmospheric temperatures and will solidify into dry ice only below -108.4 Fahrenheit, so proponents say it can be easier to trap the vapor in hydrogen-powered machines.

If the energy used to generate and purify and store and ship hydrogen doesn’t require emitting greenhouse gases or toxics, proponents argue that hydrogen is a clean alternative.

SOURCES OF HYDROGEN: THE UNFORTUNATE REALITY TODAY

Hydrogen, not carbon, is the most prevalent atom in the human body. There are two hydrogen atoms in every water molecule, and as many as hundreds of hydrogen atoms on the basic building blocks of life, from DNA to plant fibers. Nonetheless, harvesting the hydrogen atoms out of any of these structures to make hydrogen fuel isn’t easy because hydrogen likes to be bonded to carbon or oxygen; it doesn’t like to be elemental gas.

To produce pure hydrogen today, industries use primary fuel source like petroleum, natural gas, coal, or biomass. Through chemical processing, the hydrogen atoms are stripped from the fuel by way of an input of energy from electricity (more than 80 percent of which comes from fossil fuels in the United States). Furthermore, the leftover material from the stripping is carbon dioxide, the same carbon dioxide that would have been produced if the fuel was burned in an engine.

The reactions for various fuel to hydrogen conversions can be found on the U.S. Department of Energy website here.

Hydrogen can also be produced, at great energy loss, through the electrolysis of water: using electricity, water is divided into its constituents, hydrogen and oxygen. However, water electrolysis is the least carbon-neutral hydrogen production method, and it is very expensive ($3 to $6 per kilogram instead of a little more than $1 in the case of using coal for hydrogen), according to the U.S. Energy Information Administration. All hydrogen production methods result in a net energy loss.

 

 

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Photovoltaic Cells, Solar Power, and LEDs

Most of the world’s energy can go back to our sun. Every day we are heated by its electromagnetic rays, and plants use the sun’s energy to make sugars and ultimately proteins and other good things to eat. Fossil fuels were also once made from these plant and other organisms that relied on the sun’s energy millions of years ago. Today, humans can convert the sun’s energy directly into electricity, through solar thermal and solar photovoltaic systems.

SOLAR THERMAL OR PHOTOVOLTAIC?

Solar panels, also called solar thermal, convert sunlight to heat and then heat to electricity. Photovoltaic cells, or solar cells, convert sunlight directly into electric current by way of carefully-engineered semiconductor materials.

Though solar photovoltaics are more efficient converters of sunlight, they are also more expensive.

As of May 2011, the world’s largest solar power plant is a concentrating solar thermal power plant in the Mohave desert in California. Solar Energy Generating Systems has a capacity of 310 megawatts and uses parabola-shaped reflective troughs to concentrate electromagnetic radiation.

The world’s largest solar photovoltaic plant is probably the Sarnia Solar Project in Ontario, Canada. It has a capacity of roughly 80 megawatts.

HOW SOLAR THERMAL WORKS

Sunlight heats a design element (water, air, chemical fluids), and that thermal energy is transmitted for other applications, such as heating water, heating space, or generating electricity. In solar thermal power plants, sunlight heats a specialized fluid, which in turn heats water into steam, which can run turbines and produce electricity.

Solar thermal power plants use concentrators that bounce the sunlight off elliptical mirrors to a central tube, in which the specialized fluid lies.

HOW PHOTOVOLTAICS WORK

Photovoltaic cells are made of specialized diodes. Electrons (natural components of atoms) in the photovoltaic cells absorb light, which excites them to a state where they can be conducted as electrical current. This difference in energy, between the valence band (the state of a normal electron staying around its home atom) to the conduction band (electron free to move between atoms) is called the band gap.

Solar photovoltaic farm in Indonesia. Photo by Chandra Marsono.

Well-engineered photovoltaics have a band gap that coincides with the energies of as broad a spectrum of light as possible, to convert the maximum amount of the sunlight into electricity.

As sunlight energy pops electrons into the conduction band and away from their home atoms, an electric field is produced. The negatively-charged electrons separate from the positively-charged “holes” they leave behind, so that when electrons are freed into the conduction band, they move as electric current in the electric field, electricity.

PHOTOVOLTAICS ARE MADE OF SPECIALIZED MATERIALS

An ever-expanding variety of semiconductor materials can be used to make solar cells; universities and companies worldwide are researching these options, from special bio-plastics to semiconductor nanocrystals. Nonetheless, the photovoltaic cells available today require precise manufacturing conditions and are therefore far more expensive to produce than solar panels.

Silicon has to be processed under clean room conditions — carefully regulated atmospheres — to remove impurities and prevent introducing contaminants, both of which can change the band gap. Thin film-based photovoltaics require special production methods, like chemical vapor deposition. Semiconductor processing also uses strong acids and often dangerous chemicals for etching.

Today, commercially-sold cells are made from purified silicon or other crystalline semiconductors like cadmium telluride or copper indium gallium selenide.

WHERE DO WE GET THE STARTING MATERIALS?

Silicon is plentiful in the Earth’s crust. Cadmium is a readily available but highly toxic heavy metal, as is arsenic, another chemical used in some cells. As tellurium demand is only recently rising in response to solar demand, it’s unknown what the global supply is for this unusual element but it may be quite abundant. Photovoltaics are a lively area of research, and the future production and environmental costs of starter materials, production, and pollution are difficult to predict.

California, Massachusetts, Ohio, and Michigan produced the most photovoltaics in 2009. However, that year, 58 percent of photovoltaics were imports, primarily from Asian countries like China, Japan, and the Philippines.

LED TECHNOLOGY: MORE THAN HEADLAMPS

Photovoltaic cells work in the opposite direction of light-emitting diodes, or LEDs. LEDs are used interchangeably with other lighting, like light bulbs. However, LED’s work in a completely different manner, far closer to the way photovoltaics work.

Click here see a bar chart comparing how much energy is used by various light sources.

LEDs absorb energy in the form of electricity, exciting electrons into the conduction band. When the electrons in the semiconductor material drop back into the valence band from the conduction band, they emit energy in the form of photons, or electromagnetic radiation.

It’s a highly efficient process because energy isn’t wasted on producing heat, which happens with standard tungsten filament bulbs. LEDs also last a much longer time as they do not have filaments to burn out, and because they are very small and several units are used to replace one large traditional lamp, they do not all burn out at once. That makes LEDs a good choice for stoplights or other safety critical applications.

 

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Forms of Energy: Motion, Heat, Light, Sound

What forms of energy is Raul using to move his LEGO car?

When he was a teenager in Romania, Raul Oaida became obsessed with building things: a jet-engine bike, a tiny spaceship, a LEGO car that runs on air. Why? Well, why not?

You can see more cool stories about energy at The Adaptors website.

Like video and audio? Check out The Adaptors Podcast.

 

Energy comes in two basic forms: potential and kinetic

Potential Energy is any type of stored energy. It can be chemical, nuclear, gravitational, or mechanical.

Kinetic Energy is found in movement. An airplane flying or a meteor plummeting each have kinetic energy. Even the tiniest things have kinetic energy, like atoms vibrating when they are hot or when they transmit sound waves. Electricity is the kinetic energy of flowing electrons between atoms.

energy_forms_pie-chartEnergy can shift between forms, but it is never destroyed or created.

A car transforms the potential energy trapped in gasoline into various types of energy that help the wheels turn and get the car to move. Most of the energy is converted to thermal energy, which is an unorganized form of energy that is difficult to convert into a useful form.

Power plants transform one form of energy into a very useful form, electricity. Coal and natural gas plants use the chemical potential energy trapped in fossil fuels. Nuclear power plants change the nuclear potential energy of uranium or plutonium into electricity too. Wind turbines change the kinetic energy of air molecules in wind into electricity. Hydroelectric power plants take advantage of the gravitational potential energy of water as it falls from the top of a dam to the bottom.

These transformations are hardly perfect. An efficient fossil fuel power plant loses more than half of the energy it creates to forms other than electricity, such as heat, light, and sound.

Forms of Potential Energy

GRAVITATIONAL

Systems can increase gravitational energy as mass moves away from the center of Earth or other objects that are large enough to generate significant gravity (our sun, the planets and stars).

For example, the farther you lift an anvil away from the ground, the more potential energy it has. Lifting the anvil is called work, which is an interaction in which energy is transferred from one system (the person) to another (the anvil). The person has to do more work in order to carry the anvil higher, and the higher the anvil is carried, the more gravitational potential energy is stored in the anvil. If the anvil is dropped, that potential energy transforms to kinetic energy as the anvil moves faster and faster toward Earth.

CHEMICAL

Chemical energy is stored in the bonds between the atoms in compounds. This stored energy is transformed when bonds are broken or formed through chemical reactions. Like letters of the alphabet that can be rearranged to form new words with very different meanings, atoms move around during chemical reactions, and they form new compounds with vastly different personalities.

When we burn sugar (a compound made of the elements hydrogen, oxygen, and carbon) in our bodies, the elements are reorganized into water and carbon dioxide. These reactions both absorb and release energy, but the overall result is that we get energy from the sugar, and our bodies use that energy to do work.

Chemical reactions that produce net energy are exothermic. When wood is burned, the chemical reactions taking place are exothermic. Electromagnetic and thermal energy are released. Only some chemical reactions release energy. Endothermic reactions need energy to start and to continue, such as by adding heat or light.

NUCLEAR

Today’s nuclear power plants are fueled by fission. Uranium or plutonium atoms are broken apart, freeing lots of energy. Hydrogen atoms in the sun experience nuclear fusion, combining to form helium and subsequently releasing large amounts of energy in the form of electromagnetic radiation and thermal energy.

Nuclear energy is the stored potential of the nucleus of an atom. Most atoms are stable on Earth; they keep their identities as particular elements, like hydrogen, helium, iron, and carbon, as identified in the Periodic Table of Elements. The number of protons in the nucleus tells you which element it is. Nuclear reactions change the fundamental identity of elements by splitting up an atom’s nucleus or fusing together more than one nucleus. These changes are called fission and fusion, respectively.

ELASTIC

Elastic energy can be stored mechanically in a compressed gas or liquid, a coiled spring, or a stretched elastic band. On an atomic scale, the stored energy is a temporary strain placed on the bonds between atoms, meaning there’s no permanent change to the material. These bonds absorb energy as they are stressed, and release that energy as they relax.

Forms of Kinetic Energy

MOTION

A moving object has kinetic energy. A basketball passed between players shows translational energy. That kinetic energy is proportional to the ball’s mass and the square of its velocity. To throw the same ball twice as fast, a player does more work and transfers four times the energy.

rotationalIf a player shoots a basketball with backspin or topspin, the basketball will also have rotational energy as it spins. Rotational energy is proportional to how many times it spins per second, as well as the ball’s mass, and the size and shape of the ball.

In shooting a basketball, players often try to add rotational energy as backspin, because it results in the greatest slowdown in speed when the basketball hits the rim or the backboard, increasing the chance that the ball stays near the basket. The opposite direction of spin, a topspin, can be used in games like tennis, because it will help speed up a ball after impact and lowers the angle it travels after the bounce.

THERMAL ENERGY AND TEMPERATURE

Thermal energy is directly related to temperature. We can’t see individual atoms vibrating, but we can feel their kinetic energies as temperature. When there’s a difference between the temperature of the environment and a system within it, thermal energy is transferred between them as heat.

tea kettleA hot cup of tea loses some of its thermal energy as heat flows from the tea to the air in the room. Over time, the tea cools to the same temperature as the room air. At the same time, the thermal energy in the room air increases due to heat transfer from the tea. However, the thermal capacitance of the room air is much larger than the tea, so the temperature of the air in the room increases by very little – so little that a person in the room wouldn’t notice it.

Heat  flows spontaneously from high temperature objects to nearby low temperature objects, until all objects reach the same temperature, called thermal equilibrium. Some materials are easier to heat up or cool down than others. The thermal capacitance, or heat capacity, of a material tells us how much energy it takes to raise that material one degree in temperature. A pound of water has greater thermal capacitance than the same amount of stainless steel, for example. In moments, an empty one pound pot on the stove heats to 212 degrees Fahrenheit (the boiling temperature of water). If you pour a pound of water into the pot, it will take much longer than the empty pot to reach the same temperature, because water needs more energy to get as hot as steel.

SOUND

Sound waves are made when stuff vibrates – like strings on an instrument or gas molecules in the air. Sound waves travel when the vibrating stuff causes stuff surrounding it to also vibrate. This happens in liquid, solid, or gaseous states. Sound cannot travel in a vacuum because a vacuum has no atoms to transmit the vibration.

Solids, liquids, and gases transmit sounds as waves, but the atoms that pass along the sound don’t travel the way photons do. The sound wave travels between atoms, like people passing along a “wave” in a sports stadium. Sounds have different frequencies and wavelengths (related to pitch) and different magnitudes (related to how loud).

Even though radio waves can transmit information about sound, they are a completely different kind of energy, called electromagnetic energy.

ELECTROMAGNETIC RADIATION

PlantElectromagnetic energy is the same as radiation or light. This type of energy can take the form of visible light, like the light from a candle or a light bulb, or invisible waves, like radio waves, microwaves, x-rays and gamma rays. Radiation — whether it’s coming from a candle or an x-ray tube — can travel in a vacuum. Sometimes physicists describe electromagnetic radiation as being composed of particles – tiny packets of energy called photons. Each photon has a characteristic frequency, wavelength, and energy, but all photons travel at the same speed, the speed of light, or nearly 1 billion feet per second.

Electromagnetic energy can be converted to the chemical energy stored in plants through photosynthesis, the process by which plants and algae use the sun’s radiation to turn carbon dioxide gas into sugar and carbohydrates.

ELECTRIC

Electric energy is to the kinetic energy of moving electrons, the negatively-charged particles in atoms. For more information about electricity, see Basics of Electricity.

 

-Anrica Deb

 

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