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Written by William Klein   
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Thursday, 08 December 2011

Energy 101

Energy. We hear the word all day long. Save energy, I need some energy, Energizer bunny, etc. But, when it comes down to it, we’re often left grasping for straws when we try to explain what energy is. And given our current climate situation (it’s drastically changing , by the way), our rapid depletion of conventional energy sources, and an increasing population of over 7 billion worldwide that will need increasingly large amounts of energy, it is imperative that we begin to understand this ethereal concept of energy. Let’s look at what exactly energy is, where energy comes from, and how do we get energy.

What is Energy?
Energy is perhaps best described as a condition. Formally, it is the ability to do work. Energy comes in two main forms: 1) embodied energy—the inherent energy in objects due to their position, potential energy—and 2) moving energy—objects in motion, kinetic energy. We know energy mainly through the name of its form: chemical (food, fossil fuels, photosynthesis), thermal, electrical, radiant (your microwave, cellphone), nuclear (for more on this controversial power, read here ), mechanical, and others.1 Sure, it has a lot of names, it comes in many different forms. These names will come in handy as we further investigate our nation’s energy infrastructure, which is heavily dependent upon transforming energy to different, more usable forms, and transporting this energy (using more energy in this process) from source to sink. During these transformations, we will want to dust off the second law of thermodynamics, which basically states that when things change, things get messy, and you lose stuff along the way (any college student moving from dorm to dorm or apartment can attest to this).

Where Does Energy Come From?

This can be as complicated or as simple as you want to make it. Thanks to the conservation of energy theory, all the energy present today was here billions of years ago, and where it came from then is left to the mystics. So the real question is how is energy transformed? How does it become something useful that can drive our daily actions?

First steps: Energy can reach life on Earth from either outer space (the sun, gravitational pull from the moon tides) or from the inner core of the earth (geothermal energy). These sources of energy then drive much of the energy we think of every day. Global wind and water currents are largely driven by the same two processes—the spin of the Earth (Coriolis effect) and the differential solar influx (it’s hotter at the equator than the poles).2 These two factors create pressure gradients, which then drive global currents. Plants too derive their energy from the Earth and the Sun, utilizing solar energy to catalyze nutrient intake from the soil through photosynthesis. It is both from these moving parts—the flowing currents of wind and water, the growth of plants—and the primary sources, the sun and Earth, that we can harvest the energy we need to sustain human civilization.

Harnessing natural energy: Here is a good time to make a point about relative amounts of energy. Enough solar energy hits the Earth in one hour to power the Earth for a year.3 However, this energy is too diffuse for use at this time by civilization on a large scale. Plants, however, can capture this solar energy over their entire lifespan. While perhaps the plants living today don’t have enough embodied energy to make a dent in the energy picture through biomass, think about combining these two unconcentrated forms of energy. Take a whole lot of plant matter, accumulate it over millions of years, and compress it into either hard blocks or a liquid form. Poof! You have the fossil fuels that have driven the Industrial Revolution, courtesy of lots of solar energy and lots of chemical nutrients compressed into super pills.

Energy infrastructure: Because these sources of energy are concentrated, they tend not to exist where we need them—i.e., what are the chances that every city will develop on top of an oil field? To solve that problem, we have built an immense energy infrastructure—transmission lines for electricity and pipelines for natural gas and oil. Gas is moved via pumps within those pipelines, which utilize electricity to convert mechanical energy to fluid energy (the gears drive the movement of the gas). Transmission line and pipeline systems operate similarly, they carry large volumes of energy along main pathways, with branching out smaller pipes and wires (think of the high-voltage wires you see crossing roads and slicing through mountains). By the time it reaches our houses, the electricity has been reduced to 120 volts and the natural gas reduced from 1,500 psi in the transmission lines to as low as ¼ psi in your home’s pipeline.4 For a discussion of the push towards smart grid technology read here.

Natural Gas Pipeline Map5

So, what is electricity and natural gas anyways? And how does it relate to all that mumbo jumbo about solar and wind and water? Remember the good old days of chemistry class with plusses and minuses? Atomic molecules? Well, that’s
electricity, specifically the minuses, which are the electrons. Essentially, electricity is the flow of electrons from atom to atom, and we have figured out how to drastically increase this flow by creating significant gradients between the positive side and the negative side.6 The trick to inducing this flow from positive to negative has largely been done via turbines, and lots of them (most of the world’s electricity is currently produced via turbines.)7 Natural gas, on the other hand, is relatively straightforward. Natural gas is extracted from the earth, piped through pipelines, and used in your gas stove or more commonly in your home eating system. What’s tricky, however, is that this gas actually heats the water that heats your home, as opposed to the gas directly.

Transformation of energy: Turbines. Turbines. And more Turbines. Turbines are the transformers of electricity, responsible for converting energy from a fluid flow (gas or liquid) into electricity. In fact, they are the exact opposite of the pumps used to transport fluids, which convert mechanical energy to fluid energy. They are responsible for creating nearly all of the nation’s electricity (solar PV for example do not rely on turbines for conversion). Within the turbine realm, most of the thermal energy required to drive the blades comes from fossil fuels—coal and natural gas. It is important to recall our earlier notion of energy lost in the transformation process. For example, wind turbines have a technical capacity of capturing only 59.3% of energy as defined in Betz’ law.8 We then utilize our energy in our homes, where we encounter a bevy of foreign words: kWh, watts, volts, etc., but those definitions and uses will have to wait for another day.

As we look at our nation’s energy infrastructure, it is really interesting to note that the underlying technology has not changed in over 100 years. We still use the same generators, the same gears, the same pumps, turbines, pipe systems, etc. With this greater understanding of our energy infrastructure and basic energy principles, we can see why the more moving parts in a system, the more energy we are going to lose. Hence the recent movement of folks going back to applied technologies—solar ovens , passive solar , and other basic technologies that don’t require such significant infrastructure. This also helps explain the great potential in distributed solar , because not only do we not lose energy in the inefficiency of the turbines, but we don’t deal with transporting energy throughout the country. We can capture the sun right where we need it—on our roofs!

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8 Betz, A. (D. G. Randall, Trans.), Introduction to the Theory of Flow Machines. Oxford: Pergamon Press, 1966.

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Last Updated ( Tuesday, 29 May 2012 )