Air Quality

Published on March 25th, 2015 | by Sandy Dechert

14

Energy, & How It Becomes Electric Power

March 25th, 2015 by  


Since the days when we humans learned to use fire and developed six simple machines, we have progressed a lot in our ability to harness external sources of energy. In fact, we have defined and redefined its use. But what is energy? Scientists define it as “the ability to do work” — anything from manufacturing a box to carrying it, for example. The most important aspect of energy is that it enables some kind of change.

Mechanical (crane)

Mechanical energy usually comes to mind first. There are two different forms of it: kinetic (energy that is actually doing something, like running a machine) and potential (capable of running the machine, but currently at rest).

Potential vs. kinetic energy (energy.gov)To understand the distinction further, think of the energy involved in riding a bike. As you pedal along on a flat surface, you use your own kinetic energy (pedaling) to make the bicycle move forward. Going up a hill, you use more kinetic energy than when you’re on the level, but you also build up potential energy in terms of the gravity you overcome. When you’re stopped up at the top of the hill with the brakes on, you’re not using any energy at all. Heading down, you use both your kinetic energy and your gravitational potential. Think “battery” when you think of potential energy: it’s just kinetic energy that is stored.

Some examples of energy at work:

  • Wind, river, and tidal are all forms of kinetic energy. Dams and reservoirs are valuable as a potential energy source from moving water.
  • Light produces radiant energy, which we transform to create passive, photovoltaic, and concentrating solar power.
  • Heat from either artificial or geothermal (renewable) sources is called thermal energy and is often transferred from one material to another, as in boiling.
  • Energy can also come from sound (microwaves, for example).
  • We use chemical energy in batteries to store electricity.
  • Nuclear energy exists in potential at the atomic level and transforms to kinetic energy through a chain reaction.

Electricity is the premier form of energy in today’s world. Over the past 150 years, people have become accustomed to generating power by applying a spark to a fuel and burning it to run machines. This method itself consumes a lot of energy, because it depends on seeking, extracting, processing, transporting, and consuming fuels (primary energy) to achieve secondary energy. The secondary energy comes in the form of either electricity from a power plant, or steam and thermal power. Fuel burning also creates unwanted byproducts (pollution, harmful to biological life) along every step of its supply chain.

Formation of electricity fm source to power

Technically, electric energy starts as potential energy, measured in volts. When switched on, an electric circuit generates power. We measure power by combining how much electric energy is transferred and how fast the transfer happens (in joules per second, or watts). Most circuits transform the electric energy into mechanical or some other form of energy.

A watt (or kilowatt, megawatt, gigawatt, or terawatt) expresses how much electricity can be generated at a specific moment by a power plant, or how much is needed to power something (like a light bulb). We rate power plants in watts (or, more likely, kilowatts, megawatts, or gigawatts) to indicate the maximum amount of power a plant can put out at a given point in time. The (soon-to-be) largest solar PV power plant in the world has a rating of 379 megawatts, and the smallest US nuclear plant has a capacity of 502 MW. The largest single nuclear plants are three times that size, while nuclear stations go up to about 8,000 MW, or 8 GW (7 reactors). Three Gorges Dam (hydroelectric) in China is the largest electric power plant in the world, with a 22,500 MW (22.5 GW) electricity generation capacity.

Watt-hours indicate how much electricity is produced over time. What you see on your electric bill indicating electricity usage for the month is in watt-hours (or, more likely, kilowatt-hours).

Transformation of voltage in the electric power grid (pinterest.com)To get electrical energy from power plants to consumers, we send it through a system of interconnected wires: the electric power grid. We use resistors to standardize (rate) that power. However, each resistor lets a little power escape in the form of heat. We also lose power through transmission: estimates of grid loss are anywhere from 5-7% in most parts of the US and Canada. And when we convert direct current that’s originally generated to alternating current (AC), used for home and office outlets, we lose even more.

All the infrastructure used to handle the process and the energy lost in transformation, conversion, and distribution further diminish power. At the same time, the grid itself is limited to preplanned paths that limit access to power, especially in less “developed,” rural, and island areas. And consumers of power have become so distant from its source that they do not understand what’s necessary to provide it.

In the days of Edison, Westinghouse, and other electricity pioneers, power sources, availability, and losses did not mean as much as they do today. Increased population, debates over fuel costs and utility functions, and links with climate change have begun to cause considerable friction. We are transitioning from nonrenewable (fossil-fuel based) to renewable technologies, from older to newer sources of power. The structure of energy production and distribution is changing as well, beginning with the fuels we use to generate power.

Coal, oil, and natural gas, all nonrenewable resources, were abundant and accessible in the 19th century. We have used up the handiest sources, so these fuels have begun to require extraordinary effort to obtain. They are also becoming more expensive to convert to energy. Too, the process of generating power releases quantities of pollutants harmful to biological life. We can see a change in energy sources as developed countries begin to reduce or halt the use of coal — the “dirtiest” fossil fuel — and developing nations plan to use it only on the road to cleaner energy sources.

Biomass (wood, animal waste, nonfood vegetation) is intermediate. It belongs on the “renewable” list, but when burned inefficiently, it causes considerable pollution, especially in particulate form.

Cleaner sources include passive solar, windmills, dams and running water, and the like, which we once used but abandoned for the convenience and strength of electric power from fuels. Modern versions like giant wind turbines and photovoltaic panels provide much greater efficiency than our first efforts did. Geothermal, wave, and tidal energies are also showing promise. Nuclear power, used for over half a century, has proven “clean” at the power plant, but not in the uranium mining, transportation, and waste disposal, let alone in how its byproducts can be widely fatal and virtually ineradicable.

For a final snapshot of energy and power use in one of the most industrially developed nations of the world, here’s a look at all the energy sources and power use in the United States around the year 2013. Two and a half centuries ago, Americans would never have understood it. And it, too, must change to match the needs of the times.

Estimated US energy use (2013) by source (llnl.gov)






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About the Author

covers environmental, health, renewable and conventional energy, and climate change news. She's currently on the climate beat for Important Media, having attended last year's COP20 in Lima Peru. Sandy has also worked for groundbreaking environmental consultants and a Fortune 100 health care firm. She writes for several weblogs and attributes her modest success to an "indelible habit of poking around to satisfy my own curiosity."



  • JamesWimberley

    Everybody interested in sustainable technology should bookmark the LLNL energy flowchart page (link).

    The one (purely presentational) thing wrong with it is that the total area of the end-use boxes on the right does not match the areas of the source boxes on the left. I once found (but can’t retrace) a very large high-resolution image that had the correct proportions. I think the image once got accidentally truncated in the conversion to a lower-resolution web format, and they have just reproduced the error.

  • Omega Centauri

    I think you are making out too much energy to be kinetic. Kinetic is and only is one half mass times velocity squared (OK thats only good for velocities much less than the speed of light). The hydro energy stored behind a dam is not kinetic energy, it is potential energy (gravitational). Run of river hydro, whereby turbines interact with the kinetic energy of the water flow could be described as kinetic energy. Rotational energy is kinetic energy.

    Wave energy is typically half kinetic and half potential energy, it resembles the energy in an oscillator, say a pendulum. In a pendulum the energy cycles between
    kinetic (when the pendulum is at the bottom, and potential the top of the swing). Light
    is EM field energy cycling between the energy of the electric field, and the energy of the magnetic field. A capacitor if electric field energy, and inductor (think wire coil of electromagnet) is magnetic field energy. Water wave energy cycles between potential energy (the height difference of the surface), and kinetic (the motion of the fluid).

  • Bob_Wallace

    Most important, IMO, is to look at the amount of energy we waste because we use fossil fuels. Click on the last graph and look at it embiggened.

    Rejected energy = 50.0 quads
    Energy services = 38.4 quads
    57% wasted.

    Now look at electricity generation (68% wasted) and transportation (79% wasted).

    By moving off fossil fuels to renewables and electric vehicles we can reduce that waste, very significantly.

    • Martin

      Excellent explanation, but one is is still missing, cost and environmental impact of the tear down of the different power systems.

      • Bob_Wallace

        That’s something that needs a good economist to study deeply.

        Actually, it’s something that needs to be studied by a bunch of economists working separately. It seems to work best when we can compare studies and look at the numbers and assumptions used.

        I’m just going to guess that the cost and environmental impact of tearing down wind and solar farms is cheap and small. Most of the materials can be recycled and selling off the steel copper, aluminum, etc. should largely cover the costs.

        We know that it costs a lot to decommission a nuclear reactor and much of the material has to go to a hazardous waste dump, even after it’s “rotted in place” for 60 years.

        Coal plants might yield up enough steel and copper to pay for their disassembly. But the sites are pretty nasty and require extensive cleanup before they can be used for another purpose.

        Gas plants shouldn’t be too bad, but we’re unlikely to be tearing any of them down for a long time. A gas plant is really handy for deep backup. It can sit unused for months/years and be brought back into use fairly rapidly if needed.

        The whole pricing thing is very complex. And we probably don’t need to worry a lot. Wind and solar are winning out based on cost of electricity over the first 20 years. We aren’t building any more coal plants, we’re stuck with cleaning up those we’ve already built. Same with nuclear, we’re not likely to add more to that mess.

        • Ronald Brakels

          It will of course depend on the circumstances, but scrapping a wind farm should definitely be a money maker. All that steel and other metals, no benzene soaked ground, no asbestos… I’d pay money for the right to scap a wind turbine. And there has been a study done that shows I would be smart to do so.

          • Martin

            I do have hope for mankind, mainly because a lot of young and really young people actually get it and will replace some dinosaurs in the future.
            Except they will have to deal with the fallout from those other people.:((

      • Coley

        I think it’s a given that the taxpayer will be saddled with both.

    • Shiggity

      The shift to mobile computing devices and electric motor transport is increasing efficiency at incredible rates.

      Many utilities are finding they may not need to build more generation overall, but to just replace old generation with new renewables.

      • Larmion

        The shift to mobile computing devices has meant shifting computationally intensive tasks from the device to a centralized datacenter. While overall efficiency has increased significantly, the improvement is smaller than you’d think looking at client-side devices only. And increased demand for computing has so far outpaced improved efficiency.

        Still, your overall point is valid. The stagnation in power demand has mainly been driven by increased efficiency in industry rather than by households, but total demand is indeed flatlining.

    • Matt

      This is also one of those tricks that FF people use, talk about energy density. They will talk about all the energy “potential”, the energy density in FF; then leave out that 68% is wasted heat we converting to electricity. Same with potential in a tank of gas verses a battery.

  • Larmion

    That bullet list is a bit sloppy.

    – Energy can also come from sound (microwaves, for example).

    Microwaves are part of the electromagnetic spectrum, just like the visible light you referenced under radiant energy. Sound is a form of mechanical energy (molecules of air vibrating).

    – Nuclear energy exists in potential at the atomic level and transforms to kinetic energy through a chain reaction.
    Depends. It is generally converted into thermal energy; only a small fraction is released as kinetic energy.

    – Light produces radiant energy, which we transform to create passive, photovoltaic, and concentrating solar power.

    Light IS radiant energy, it does not itself produce energy.

    – Heat from either artificial or geothermal (renewable) sources is
    called thermal energy and is often transferred from one material to
    another, as in boiling.

    Heat is thermal energy, but what is an ‘artificial’ source of thermal energy?

    • Marion Meads

      And then you forgot Stefan-Boltzman’s Law. Go ahead and look it up!

      • Larmion

        What has black body radiation to do with any of the things I just said? Hint: nothing.

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