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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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.

Energy comes in two basic forms: potential and kinetic.

Potential Energy is any type of stored energy; it isn’t shown through movement. Potential energy can be chemical, nuclear, gravitational, or mechanical.

Kinetic Energy is the energy of movements: the motion of objects (from people to planets), the vibrations of atoms by sound waves or in thermal energy (heat), the electromagnetic energy of the movements of light waves, and the motion of electrons in electricity.

Each form of energy can be transformed into any of the other forms, but energy isn’t destroyed or created. Losses of energy can always be accounted for by small transformations to other types of energy, like sound and heat. Power plants convert potential energy or kinetic energy into electricity, a type of kinetic energy, and electricity in turn can be converted back into other forms of energy, like heat in an oven or light from a lamp.

Forms of Potential Energy

CHEMICAL

Chemical energy is stored in the bonds between atoms. (See here for more about atoms.) This stored energy is released and absorbed when bonds are broken and new bonds are formed –  chemical reactions. Chemical reactions change the way atoms are arranged. Like letters of the alphabet that can be rearranged to form new words with very different meanings, atoms go through chemical reactions to be reorganized to form new compounds  with vastly different properties. Each compound has its own chemical energy associated with the bonds between the atoms it contains.

When we burn sugar (a compound made of hydrogen, oxygen, and carbon) during exercise, it’s components are reorganized into water (H2O) and carbon dioxide (CO2). These reactions both absorb and release energy, but the net reaction releases energy.

Chemical reactions that produce net energy are called exothermic. When gasoline is burned, the reactions taking place are exothermic and thermal energy is released, which can be used to power an engine. Meanwhile, chemical reactions that absorb net energy are called endothermic.

NUCLEAR

Nuclear energy is the stored potential of the nucleus, or center, of an individual atom. Most atoms are stable on Earth; they retain their identities as particular elements, like hydrogen, helium, iron, and carbon, as identified in the Periodic Table of Elements. Nuclear reactions change the fundamental identity of elements.

Unlike everyday chemical reactions that change how atoms are stuck together (rearranging the letters of a word), nuclear reactions change the name of the atoms themselves. (Sort of as if the letter “m” was split into the letters “r” and “n,” or the letters “l” and “o” combined to make the letter “b”).  In nuclear reactions, atoms split apart or join together to form new kinds of atoms, called fission and fusion, respectively.

When atoms split apart or fuse together, they release stored nuclear energy, sometimes in huge quantities.

Today’s nuclear power plants are fueled by fission, a breaking apart of uranium or plutonium atoms that releases lots of energy. Hydrogen atoms in the sun experience nuclear fusion, combining to form helium and subsequently releasing large amounts of kinetic energy in the form of electromagnetic radiation and heat.

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 basis for the energy is a reversible 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 are relaxed.

GRAVITATIONAL

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

For example, the farther you lift an anvil away from the ground, the more potential energy it gains. The energy used to lift the anvil is called work, and the more work performed, the more potential energy the anvil gains. If the anvil is dropped, that potential energy becomes kinetic energy as the anvil moves faster and faster toward Earth.

Forms of Kinetic Energy

MOTION

A moving object has kinetic energy. A basketball passed between players shows translational energy in the motion that gets the ball from player A to player B. 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 uses four times the energy.

If a player shoots a basketball with backspin or topspin, the basketball will also have rotational energy as it spins through the air. Rotational energy is proportional to how quickly the ball spins, as well as the ball’s mass, and the size and shape of the ball. A hollow ball needs more energy than a solid ball of equal mass to spin at the same rate. The hollow ball requires more energy because it’s mass is farther from its center.

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

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

A hot cup of tea in a cool room loses some of its thermal energy as heat flows from the tea to the room. The atoms in the hot tea slow their vibrating as the tea loses heat, and over a few hours the tea cools to the same temperature as the room. At the same time, the room gains the lost thermal energy from the tea, but because the room is much larger than the tea, the temperature of the room increases by so little a person wouldn’t notice it.

Adjacent objects that are different temperatures will spontaneously transfer heat to try to come to the same temperature. However, how much energy it takes to change the temperature of an object is based on what its made of, a principle called heat capacity or thermal capacity. Water has a higher heat capacity than steel, for example. An empty pot on the stove takes almost no time to get to 212 degrees Fahrenheit (the boiling temperature of water). A pot half-full of water will take much longer to reach the same temperature, because water needs to absorb more energy — per weight, per degree — to get as hot as metal.

SOUND

Sound waves are made through the transmitted vibration of atoms in bulk — though atoms can also vibrate through heat — and sound can travel by the motion of atoms regardless of whether they are 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 (unlike the photons in light). 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.

ELECTROMAGNETIC RADIATION

Electromagnetic energy is the same as radiation or light energy. This type of kinetic energy can take the form of visible light waves, 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 nuclear fission of uranium — can travel in a vacuum, and physicists like to think of electromagnetic radiation as divided into tiny energy packets 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 stored chemical energy by plants during photosynthesis, the process by which plants, algae, and some other small organisms use the sun’s electromagnetic 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.

The electricity industry has three main components: the power plants, the transmission lines, and the distribution to you through utilities.

Mostly, three different entities operate these components. A power company owns a plant, some non-profit transmission company is responsible for the transmission, and a utility distributes the electricity to users.

Transmission may seem boring and straightforward — just a bunch of wires — but transmission is probably the most complex and sophisticated part of electricity.

WHY TRANSMISSION IS IMPORTANT

We only have the capacity to store the tiniest fraction of electricity produced in a single day. Electricity has to be generated within moments of when its used.

Many thousands of megawatts of power plant capacity are operating right now, and all that power has to be delivered to the right place, right now, too. It’s happening every day, even as individual power plants are pulled off line for service, even as fuel prices fluctuate, or weather conditions change and there’s a heat wave and everyone cranks up their air conditioning, or a major line goes down and there’s suddenly far too much electricity being generated.

Imagine what happens when your source of energy is wind, and the wind dies down. How do you fill the hole? How do we plan for that? It’s all part of the complexity of transmission, and the authorities in charge of it, who also are responsible for reliability and operating the power markets.

The price of electricity fluctuates by hour, as electricity demand rises and falls throughout the day [link to MM if it's ever constructed]. It can be ten times the price in the middle of the day, when air conditioners and industries are running full blast. But did you know that the price is also different depending on where you are geographically?

Imagine if a single, high voltage line goes down. It’s not only that the people expecting that power won’t get it. Physics dictates that the surrounding lines will instantly be carrying more, and they may go down too, or their flows may change direction. Suddenly, in that instant, the price of electricity on one end of the line become sky high as there’s a lack of electricity, and the price at the other end drops down to nearly zero because there’s too much electricity going there.

Many of these details – energy market administration, the reliability of the power, the price – hinge on the electricity grid and how it’s run and where the lines are.

WHY TRACKING TRANSMISSION DATA IS COMPLEX

There is no national electricity grid. The country is divided into the Eastern Interconnected System, the Western Interconnected System, and the Texas Interconnected System. Our grids also interact with the Mexican and Canadian grids in some places.

To complicate matters, a large number of authorities are in charge of electricity transmission, and the authorities don’t all work the same way. There are Independent System Operators in some regions and Regional Transmission Organizations in others, and there are many tiny municipalities all over the country. There are eight regional reliability councils, map here, and the whole smorgasbord is overseen by the Federal Energy Regulatory Commission.

A PATCHWORK OF ELECTRICITY MARKETS

On top of the regulatory diversity, which is not really divided by state, energy markets rules are divided by state. For example, all of New England is lumped together when it comes to transmission, under the New England Independent System Operator. Yet, each state in New England has different environmental laws, electricity rate rules, and so forth. For more about electricity markets, go here.

Each region has different rules about when or if it publishes data about how much electricity was used, who used it, and when it was used. But these regions aren’t divided exactly along state lines.

To track how much electricity individual homes used yesterday is almost impossible. Electricity load numbers are all mixed up with industrial and municipal uses, divided along regions that aren’t quite counties or states. Furthermore, in some parts of the country, authorities claim that the electricity demand data is confidential, at least until it has to be submitted to the Federal Energy Regulatory Commission once per year.  That makes it hard for the public, the government, and research institutions to get information about how we use energy.

SMART GRID: WHERE OH WHERE IS THE ELECTRICITY NOW?

When electricity leaves the power plant, we don’t know exactly where it goes, and as stated before, the authorities who know anything are diverse and follow different rules. Yes, we have extremely complex math to model where it is. Yes, we can go out and measure the lines. Yes, individual power plant companies know how much they’re producing. But do we have a national ability to know what is going on everywhere on the grid? No.

But we could.

That is the idea behind the smart grid: know what is going on instantaneously. The idea encompasses technologies for high voltage lines and for low voltage and individual users. It includes tracking electricity and also handling data wirelessly.

Applications for this information could be endless, from encouraging less energy use during peak hours to sociological studies and beyond.

SMART METERS

We are only tracking the total energy used over a month. If there aren’t special meters and ways to relay information, we don’t know how much an individual or a neighborhood is using right now. Someone from the electric company would have to get in a truck and go to your home or your neighborhood and measure.

Instead, with smart meters, information about hourly use can be read instantly by the power company and by you, the user.

Having a meter connected to a pleasant interface like a monitor or a webpage allows an individual to take control of their own energy use in a way that was vague and theoretical before.

We can track when people use electricity, where and when there are inefficiencies, pinpointing power outages and how widespread they are. Lumping geographical hourly data together, there’s no end to interesting aspects to study, even into the realms of sociology and psychology.

However, smart meters are new, and the technology is still developing, which means there’s opportunities for many mistakes or poorly functioning equipment. In 2011 a California utility found that a small proportion of meters were malfunctioning if the internal temperatures rose too high.

For more information about the electricity market see here.

Also see the Basics of Electricity.

Machines are so complicated these days it’s difficult to quickly explain how they work. Nonetheless, today’s machines were built using the basic principles of physics that we began harnessing hundreds of years ago.

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A BRIEF HISTORY OF ELECTRICITY

The first major use of electricity began in 1879, when Thomas Edison began installing incandescent lighting in notable locations like Wall Street in New York City. Edison wasn’t alone in his pursuit of electricity development, but he was the first to install integrated systems in conspicuous places.

At that time, Americans used various other light sources, like oil lamps, candles, and fires. A candle gives off only around a single watt’s worth of light. Calcium (or lime) lights could provide a lot of light, but it was a harsh light and reserved for conditions like the theater, hence the term in the limelight.

Most lighting was very poor – and often dangerous – in comparison to fluorescent bulbs, and electricity became popular quite quickly. By the turn of the century, other electric devices began to become available, and by the 1920s, Americans could purchase electric refrigerators, dishwashers, and washing machines.

The first electrical systems depended on extremely local power plants, within a few blocks, or even within the building. As time passed, electricity development became a regional responsibility, and today, the United States is split into many different systems of electricity distribution, including both regulated municipalities and for-profit utilities.

WHAT IS ELECTRICITY?

Electricity isn’t merely the existence of electrons but the flow, and it is their flow that provides power. It’s a little bit like gravity and the flow of water downhill. Water will move spontaneously downhill because of gravity. Electrons (like other charged particles) move spontaneously when they are in electric fields. An electric field is generated when there’s a difference in electric potential – called a voltage – just like a hill exists when there’s a difference in altitude.

Electricity is the flow of electrons, which themselves are small charged particles associated with atoms. Under neutral conditions, electrons stay with the atom or group of atoms that make up a compound. However, one electron is indistinguishable from another and can move from one atom to an adjacent one if the atoms make up a conducting material, like various metals.

Voltage can be thought of as the height of the hill. The bigger the voltage, the more electrons want to move, and the more power can be delivered.

Cataract Falls, Mount Tamalpais, California

Electrons moving can be diverted to do work, sort of in the same way that water traveling downhill can be diverted to run a mill or turbine.

The water’s kinetic energy is lost as it is used up in the turbine. Likewise, the electrons’ kinetic energy is lost when they are put to work in a device. The electrons don’t get destroyed in the process of losing energy, just as the water wouldn’t be destroyed.

ALTERNATING CURRENT

When you plug in something like a light, electrons flow from the plug, through the light, and back out through the plug. However, it’s not that simple, since we use what’s called alternating current, or AC, which means that the electrons flow one direction and then reverse direction. Alternating current makes it easy to change from a high voltage to a lower voltage. This change is made through a transformer.

ELECTRICITY IN THE HOME

Today, inside the home, electricity powers computers, televisions, telephones, lights, refrigerators, heaters, air conditioning, healthcare-related devices, video games, rechargeable toys, stereos, alarm systems, garage doors, ovens, stovetops, dishwashers, clothes washers, routers, can openers, DVD players, DVRs, and countless rechargeable devices like phones and electronic tablets.

Computers, televisions, and handheld electronic devices have become increasingly popular, while refrigeration, heating, and cooling have become more efficient. These recent trends in home electricity use have shifted the greater part of home energy needs from climate control to electronics.

A FUTURE FOR TELEVISION?

Today, most households have more than two televisions, with 88 percent of homes have two or more televisions in 2009. The average household had 2.5 televisions. In the same year, 79 percent had DVD players, 43 percent had DVRs, and 86 percent of households had one or more computers. Nielson reported in May, 2011 that for the first time in 20 years, television ownership is slightly down, perhaps in part because computers may be replacing the use of televisions, DVDs, VCRs, and video games.

More about home energy in the energy efficiency section.

As is the case with so many scientific fields, the history of nuclear physics and energy development has always been wrapped up with the history of modern warfare.

An unprecedented level of research went into the American bomb program, applying a rapidly evolving understanding of nuclear physics immediately to building a weapon. That investment spurred the rest of the world to pursue nuclear fission, often using the energy as an excuse for the weapons development. Rather than isolate nuclear energy from its less peaceable counterpart, the timeline incorporates all types of nuclear history.

Recent nuclear media coverage:

Germany begins shutting down old reactors and considers swearing off nuclear power entirely. Germany Dims Nuclear Plants, but Hopes to Keep Lights On.

New evidence that Japan’s troubled reactors were destined to malfunction, tsunami or not, in The Explosive Truth Behind Fukushima’s Meltdown.

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