Published on EGEE 401: Energy in a Changing World (https://www.e-education.psu.edu/egee401)

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Unit 1, Lesson 2

Introduction

Unit 1: Energy Principles – Lesson 2: Energy Transformations

About Lesson 2

In the previous lesson, we considered energy in its many kinetic and potential forms and began our investigation into the energy industry. To get energy when and where we need it, in a form that is useful to us, we create conditions that cause energy transformations. For example, when we drive a car or when we produce electricity from burning coal or spinning windmills and cool our home, we are orchestrating large scale energy transformations to give us energy when and where we want it.

This lesson explains the fundamental nature of those energy transformations that are most relevant to the energy industry, how we use energy and how the inputs and outputs of these activities interact with the environment. These transformations will be the groundwork for future lessons regarding climate change, electricity demand and generation, and transportation fuels and systems.

You'll need to be comfortable with the content of the reading from Lesson 1. These terms, defined there, will be used throughout this lesson and course: potential energy, chemical energy, mechanical energy, nuclear energy, gravitational energy, electrical energy, kinetic energy, radiant energy, thermal energy, motion energy, sound energy, conservation of energy, and energy efficiency. It may be helpful during the course of this lesson to refer back to the Lesson 1 reading assignment.

What will we learn in Lesson 2?

With the successful completion of this unit, you will be able to:

  • explain how energy transforms from one type to another;
  • define energy efficiency;
  • understand descriptions of machines and processes that transform energy;
  • relate energy concepts to the world around you;
  • master new energy-related topics, actively, and with meaning.

What is due for Lesson 2?

The chart below provides an overview of the requirements for Lesson 2. For details regarding the assignment, refer to the page(s) noted in the table.

Please refer to the Calendar in CANVAS for specific time frames and due dates.

Lesson 2 Requirements
REQUIREMENT LOCATION SUBMITTED FOR GRADING?
Reading: Read all pages of Lesson 2 and interact with related materials as instructed. Pages 2 - 10 No
Lesson 2 Activity: Complete Lesson 2 Activity. (It's in CANVAS, under Modules, Unit 1.) Page 4 Yes
Unit 1 Discussion Forum: Energy's Pace of Change (It's in CANVAS, under Modules, Unit 1.) Page 5 Yes

Questions about EGEE 401?

If you have any questions, please post them to our Questions about EGEE 401?  Discussion in CANVAS. Use this Discussion for general questions about course content and administration. I will check it daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate or have a related question.

 

Chemical to Thermal

Combustion

Fire Triangle with Fuel, oxygen and heat each on it's own side of the triange.
Figure 2.1: Fire Triangle.
Credit: Public Domain

In combustion, chemical energy is transformed to thermal and radiant energy.

Combustion (burning) is essentially a chemical reaction between a fuel and oxygen. Atoms in the fuel are held together by chemical bonds. When conditions are right, the atoms start to break apart from one another, setting off a chain reaction that releases more heat, causing more atoms to break away. Do you remember Smokey the Bear’s Fire Triangle?

The interaction of the three sides of the fire triangle (heat, fuel, and oxygen) are required for the creation and maintenance of any fire. When there is not enough heat generated to sustain the process, when the fuel is exhausted or when the oxygen supply is limited, a side of the triangle is broken and the fire is suppressed.

When heat is added to fuel and oxygen, the atoms in the fuel are energized and start to break apart from one another. Once released, these atoms form new bonds with the oxygen. Energy is required to break the chemical bonds in the fuel (an endothermic process). When the new chemical bonds are formed, energy is released (an exothermic process).

In combustion, more energy is released from the new bonds than is required to break the old bonds. This excess energy keeps the reaction going and produces heat and light.

Why Fossil Fuels are Special

Fossil fuels (coal, petroleum and natural gas) are excellent fuels because they are made up mostly of hydrocarbons (molecules with carbon hydrogen bonds). These molecules react readily with oxygen. The carbon combines with oxygen to form carbon dioxide (CO2). The hydrogen combines with oxygen to form water (H2O).

A primary component of natural gas is methane. Here’s the chemical reaction between methane (CH4) and oxygen which produces carbon dioxide, water, and heat.

Combustion Reaction Energy from Bond Energies. See link in credit line for details. (links to different site)
Figure 2.2: Methane Combustion.
Credit: Virtual Chembook, [1] Elmhurst College, Charles Ophardt

A reaction between a hydrocarbon and oxygen yields carbon dioxide and water. But, when there are other elements present, these will become part of the reaction and resulting byproducts. For example, air contains nitrogen. A byproduct of combustion with air will be nitrogen dioxide (NO2). Similarly, the presence of sulfur results in sulfur dioxide (SO2). Depending on the conditions, carbon monoxide (CO) may also be produced. The products of combustion depend on the specifics of all the compounds involved in the reactions.

In all cases, combustion is a chemical reaction that produces products in the form of compounds, heat, and light.

Radiant to Chemical

Photosynthesis

Sun shining on tree.
Figure 2.3: Photosynthesis: In the process of photosynthesis, plants convert radiant energy from the sun into chemical energy in the form of glucose - or sugar.
Water (6H2O) + carbon dioxide (6 CO2) + sunlight (radiant energy) = glucose (C6H12O6) + Oxygen (6O2).
Credit: Energy Explained [2]

Photosynthesis is the transformation of radiant energy to chemical energy.

Plants take in water, carbon dioxide, and sunlight and turn them into glucose and oxygen. Called photosynthesis, one of the results of this process is that carbon dioxide is removed from the air. It is nature's process for returning carbon from the atmosphere to the earth.

The "fossil fuels" we use today (oil, coal, and natural gas) are all formed from plants and animals that died millions of years ago and were fossilized. When we burn (combust) these carbon-rich fuels, we are pulling carbon from the earth and releasing it into the environment.

Viewing Assignment

Watch the video Photosynthesis [3], a segment excerpted from Interactive NOVA: "Earth."

A hint of things to come! We'll learn more about photosynthesis and related process later, when we study the carbon cycle (the natural movement of carbon atoms between the atmosphere, oceans, earth, and living things).

Nuclear to Thermal

Fission

Nuclear fission is the transformation of nuclear energy to thermal energy and electromagnetic radiation.

Fission, for nuclear power generation, is a controlled nuclear reaction that takes place in a specially designed nuclear reactor. A fuel (typically uranium 235) is bombarded with neutrons, causing one heavy atom to split into two. This reaction releases tremendous amounts of energy and more excess neutrons, which them bombard more heavy atoms causing them to split, kicking off a chain reaction.

The fragmented remains of the busted atom are fission products.The diagram below shows the fission reaction for the fuel uranium 235, producing the products barium and krypton, and releasing neutrons.

diagram of  fission reaction for the fuel uranium 235.  See link in credit line for more details (opens new website)
Figure 2.4: U-235 nuclear fission chain reaction.
Credit: Nuclear Fission Basics [4]

In the fission process, a tiny amount of mass is "lost." This mass has been converted to energy as described by Einstein's E=mc2, where E = energy, m = mass and c = speed of light. The speed of light is, of course, a very large number. Without a lot of math, you can see that a very small amount of matter converts to a very large amount of energy.

The fission products resulting from a nuclear reaction have an imbalance of neutrons relative to protons, making them unstable. Described as radioactive, these nuclei spontaneously emit electromagnetic rays or streams of particles. This spontaneous loss of energy results in the atoms themselves transforming from one type to another, in a process called nuclear decay. These materials are extremely dangerous to humans and in some cases remain so for over a thousand years.

Fusion

In fusion, a reaction both opposite of and similar to fission, nuclei are forced together in a process resulting in total less combined mass, yielding tremendous amounts of energy.

Fusion is used with fission in nuclear weapons (hydrogen bombs), but, currently, there are no commercial fusion energy production plants in operation or planned. The insurmountable challenges for a controlled, commercial fusion energy production are getting the fuel (different isotopes of hydrogen) to a high enough temperature and then confining it long enough to get the chain reaction going.

As an interesting aside, the sun itself is a natural fusion reactor – its massive gravitational forces create conditions right for fusion.

For more about fusion, here's an excellent site and summary (and my reference for this section), from the World Nuclear Association [5].

Motion to Electrical

Electrical Generation

electricity generator driven by steam
Figure 2.5: A large electricity generator driven by steam at CalEnergy's Leathers geothermal power plant in Imperial County, California (from Explain That Stuff! [6]).
Credit: Photo by Warren Gretz, courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).

Electrical generation is the transformation of motion energy into electrical energy.

An electrical generator is a machine that converts mechanical energy into electricity. It works on the phenomenon of electromagnetic induction, discovered by Michael Faraday nearly 200 years ago. When an electrical current runs through a wire, a magnetic field is created around it. Likewise, if a changing magnetic field is created around a wire, electricity will move through the wire. This is accomplished through the relative motion of a magnet and wire.

"Electric generators are essentially very large quantities of copper wire spinning around inside very large magnets, at very high speeds. A commercial utility electric generator—for example, a 180–megawatt generator at the Hawaiian Electric Company's Kahe power plant on Oahu—can be quite large. It is 20 feet in diameter, 50 feet long, and weighs over 50 tons. The copper coils (called the "armature") spin at 3600 revolutions per minute.” (Source: The Electricity Forum [7])

I also like this explanation from Explain That Stuff! [6], after making the point that a generator is essentially an electric motor working in reverse, the article continues:

An electric motor is essentially just a tight coil of copper wire wrapped around an iron core that's free to rotate at high speed inside a powerful, permanent magnet. When you feed electricity into the copper coil, it becomes a temporary, electrically powered magnet—in other words, an electromagnet—and generates a magnetic field all around it. This temporary magnetic field pushes against the magnetic field that the permanent magnet creates and forces the coil to rotate. By a bit of clever design, the coil can be made to rotate continuously in the same direction, spinning round and round and powering anything from an electric toothbrush to an electric train.

So how is a generator different? Suppose you have an electric toothbrush with a rechargeable battery inside. Instead of letting the battery power the motor that pushes the brush, what if you did the opposite? What if you turned the brush back and forth repeatedly? What you'd be doing would be manually turning the electric motor's axle around. That would make the copper coil inside the motor turn around repeatedly inside its permanent magnet. If you move an electric wire inside a magnetic field, you make electricity flow through the wire—in effect, you generate electricity. So keep turning the toothbrush long enough and, in theory, you would generate enough electricity to recharge its battery. That, in effect, is how a generator works. (Actually, it's a little bit more tricky than this and you can't actually recharge your toothbrush this way, though you're welcome to try!)

In practice, you need to put in a huge amount of physical effort to generate even small amounts of electricity. You'll know this if you have a bicycle with dynamo lights powered from the wheels: you have to pedal somewhat harder to make the lights glow—and that's just to produce the tiny amount of electricity you need to power a couple of torch [flashlight] bulbs. A dynamo is simply a very small electricity generator. At the opposite extreme, in real power plants, gigantic electricity generators are powered by steam turbines. These are a bit like spinning propellers or windmills driven using steam. The steam is made by boiling water using energy released from burning coal, oil, or some other fuel. (Note how the conservation of energy applies here too. The energy that powers the generator comes from the turbine. The energy that powers the turbine comes from the fuel. And the fuel—if it's coal or oil—originally came from plants powered by the Sun's energy. The point is simple: energy always has to come from somewhere.) "

This should give you a good idea of how the pieces fit together: whenever we can get something to turn, we can make electricity. Steam, falling water, and wind are examples of ways to turn a turbine, spinning a wire inside a magnetic, generating electricity!

Chemical to Electrical

diagram of a battery.  See link in caption for text version.
Figure 2.6: Batteries transform chemical energy into electrical energy.
Text Version [8]
Credit: Northwestern College [9]

Batteries transform chemical energy into electrical energy.

There are many different types of batteries, but all have three basic components: positive electrode (cathode, or "positive terminal"), negative electrode (anode or "negative terminal"), and electrolyte.

When the positive and negative terminals are connected so that electrons (electricity) can flow between them (usually by a wire), chemical reactions occur at the electrodes. These reactions release excess electrons at the anode which flow to the cathode.

The chemical reactions occur between the electrolyte and the cathode and between the electrolyte and the anode. Different types of batteries use different materials for the these three components.

Disposable batteries (batteries that can't be recharged) work until the reactive chemistry of the electrodes and electrolytes is exhausted.

In a battery that is re-chargeable, electricity can be applied to run the process in reverse, restoring the properties of the materials so that electricity-generating reactions will again recur. Car batteries are an example of re-chargeable batteries.

Batteries with a liquid electrolyte are called "wet cell." Lead-acid batteries (typical car battery) are wet cell. Batteries with a solid electrolyte are called "dry cell." Alkaline batteries used around the house are examples of dry cell.

Batteries make energy portable. In effect, they store electricity that can be delivered on demand, when and where it is needed.

Radiant to Electrical

Photovoltaic

a large solar array (solar panels on the roof of a building)
Figure 2.7: Solar Array.
Credit: National Renewable Energy Laboratory Photographic Information exchange [10]

In a photovoltaic process, radiant sunlight is converted to electricity.

In the 1800s, it was discovered that certain materials have the natural property of generating electricity when exposed to sunlight. But the amount of electricity was tiny. Over the years, vast improvements in materials and technology have led to the development of standard products that use this photovoltaic (PV) property to generate significant amount of electricity from sunlight.

The photovoltaic material is typically silicon, an abundant natural resource, mixed with other natural materials to enhance its electricity-generating properties. The energy from the sun invigorates the photovoltaic material at the molecular level, causing electrons to break away, creating an electrical current. To conduct the current in a controlled and orderly manner, manufacturers package thin slices of photovoltaic material between layers of carefully designed conductors to form what is called a solar cell. These cells are usually wired together in modules (or panels) that are assembled in groups called arrays. This array is the wall of shiny panels you may see on a roof or in a yard. (In the photograph above, you can see that module consists of 36 cells. This large array contains many, many modules!)

When sunlight hits an array, electricity is generated. Sunlight is the fuel (the source of energy)—the more sunlight, the more electricity. The PV array is the power plant—the larger the array, the more electricity you can generate.

Reading Assignment

Open and review the data sheet for a 240-Watt solar module [11]. Typically, many modules are installed together to form a solar array. [12]

Solar Energy

A word about the words "solar energy."

Solar energy is a broad term—it involves many technologies and applications. Photovoltaic (PV) systems generate electricity from the sun, using the photovoltaic process.

Solar energy can also be used to heat water (or other fluids) for space heating or domestic use. This is an entirely different application of solar energy and is usually called solar hot water or solar thermal. In photovoltaic applications, the photovoltaic material absorbs energy of certain wavelengths, energizing and realizing electrons. (This process actually works better at cooler temperatures.) In thermal applications, the material or fluid is simply warmed from absorbing the sun's energy.

When buildings are designed to work with the sun, absorbing heat from the sun when it is needed and rejecting it when it is not needed without the use of mechanical equipment (fans, collectors, pumps, controls), it is called passive solar. For heating, passive solar typically involves a "thermal mass" (say a stone floor) that absorbs the sun's heat which is then radiated off when ambient temperatures drop. For cooling, this means design features such as overhangs that block summer light and windows that open. In fact, deciduous trees are great passive solar devices—in the summer, they provide shade, in the winter, they allow the sunshine to come through! I have passive solar in my greenhouse, metal drums painted black and filled with water that absorb heat during the day and radiate it back overnight.

There are other ways of using solar energy (including "concentrating solar"), but the ones discussed here are the major ones in use now. The important point is, when discussing "solar energy," remember it has many possible applications.

Refrigeration Cycle

Air Conditioning and Heat Pumps

Air conditioners and heat pumps use a series of energy transformations to convert electricity to thermal energy, and none of them involve combustion! At the heart of these systems is a multi-step transformation process called the "refrigeration cycle" that transforms motion energy into thermal energy (heat).

Essentially, in the refrigeration cycle, a working fluid (refrigerant) moves through a series of stages where it goes from gas to liquid and back to gas. A compressor mechanically squeezes the gas until it is a hot, high pressure gas. From there, the gas goes to a condenser where it cools down (releasing heat to the surrounding air) until it becomes a liquid, still under high pressure. In the final stage, the liquid goes to an evaporator where the pressure drops and the liquid evaporates, becoming a gas again. When the liquid evaporates, it pulls heat in from the surrounding air.

Reading Assignment

To better understand, read through "How an Air Conditioner Works" and "What a Ton of Cooling Is" from the American Society of Heating, Refrigerating and Air-Conditioning Engineers. [13]

Air conditioners and heat pumps use electricity to drive the compressor, fans, and air handling units.

According to the EIA [14], in 2014 about 13% of the electricity used in U.S. homes was used for space cooling. (We'll talk a lot more about electricity demand and consumption later in the course, but know for now that the multi-step refrigeration cycle is the transformation process that is at the heart of a significant portion of energy consumption in our country.)

Energy Efficiency

Energy efficiency is the amount of useful energy you get from any type of system. It is calculated as the useful energy output divided by the total energy input.

A light bulb converts electricity to light and heat. Typically, the light is the "useful" output and the heat is a byproduct. Consider this, only five to eight percent of the energy used by a standard incandescent light bulb is converted to light, the rest is dissipated as heat. An incandescent bulb is actually a space heater that throws off a little light!

About 20% of the energy contained in gasoline is used to propel a vehicle with a combustion engine. On the other hand, cars with electric motors are able to convert around 60% of the electricity they get from the grid to power at the wheels. (source: fueleconomy.gov) [15]

The energy efficiency measure (useful output/total input) can be helpfully applied to many products and systems. However, units of measure must be handled carefully. The electricity a light bulb uses is measured in watts; the light it produces is measured in lumens. To simplify, many industries have adopted standard measures to simplify efficiency comparisons between related products. Lamps, for example, are often compared on the basis of lumens/Watt, called luminous efficacy.

Similarly, the efficiency air conditioning units is regulated by the U.S. Department of Energy (DOE) using the Seasonal Energy Efficiency Ratio or "SEER" rating system. The SEER rating is BTUs (total cooling output) divided by Watt hours (total electric input). The higher the rating, the more efficient the unit is. For more details, see the Air-Conditioning, Heating and Refrigeration Institute [16].

The US Government has simplified energy efficiency shopping for customers with the ENERGY STAR [17] rating system, a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy that awards Energy Star status to highly efficient products. If you'd like more information, visit the Energy Star [18] website or read through How Energy Star Works [19].

"Energy Efficiency"

A word about the words "energy efficiency"...

The term "energy efficiency" is also used with a more broadly scoped meaning, such as this previously published definition from the World Energy Council, "energy efficiency improvements refer to a reduction in the energy used for a given service (heating, lighting, etc.) or level of activity. The reduction in the energy consumption is usually associated with technological changes, but not always, since it can also result from better organization and management or improved economic conditions in the sector ('non-technical factors')."

In this sense, a programmable thermostat may help with "energy efficiency." Simple steps such as remembering to turn off the lights is a non-technical behavior that can also improve energy efficiency. These are examples of energy efficiency in its broader meaning, related to the smarter use of energy for a specific purpose.

Using PVWatts

Developed by the National Renewable Energy Laboratory (NREL), PVWatts is an online calculator for easily estimating the energy output and cost savings of a grid-connected photovoltaic (PV) installation. The calculator is widely used, especially during the design stage of proposed installations.

We are going to use the PVWatts calculator to explore and understand the concepts of power, energy and efficiency. It is an excellent opportunity to apply these concepts to a real world application. It also give us the chance to gain a better understanding of solar photovoltaic basics.

PVWatts Walk Through

Go to PVWatts [20]

1.     In the Get Started: field, enter “Harrisburg, PA”.

You’ll see a page describing the recommended Solar Resource Data for use in this estimation. Why is this important? Solar energy is the “fuel” for a photovoltaic system. The more fuel, the more electricity it can produce. The calculator uses historical weather data to estimate how much sunshine is available in a particular area.

2.     Using the arrow on the right, “Go to system info”

On this page you provide basic information about the photovoltaic design you are considering.

  • DC System Size (kW): From lesson 1, you’ll recognize “kW” is a unit of power. For a photovoltaic system, power indicates the rate at which energy from the sun is transformed into electricity. Individual solar cells and modules all have power ratings. The power rating for a solar module is the sum of the power ratings for each cell. The power rating for an array is the sum of the power rating of all the modules.

Remember our 240W modules from earlier in this lesson? If we build an array of twelve of them, the power rating of the array is (24 modules x 240 W/module) = 5,760 W or 5.76 kW. This “kW” value relates directly to the number of modules and is considered the “system size.” When someone says, how big is your system? You’d say “5.6 kW.”

In PVWatts, you’ll see the default value for system size is 4 (kW). For now, leave it as this value.

A quick word about AC/DC...

Don't get too distracted by the terms AC and DC. They are just two different forms of electricity. In both cases, electrons are flowing through a conductor (typically a wire). Direct Current (DC) means the electrons are moving in one direction all the time. Alternating Current (AC) means the electron flow alternates directions. A solar panel generates electricity in the DC form. The electricity grid (wires from the utility company) provides our homes and businesses with electricity in the AC form. In photovoltaic installations, we use a piece of equipment call an inverter to transform electricity from DC to AC.

  • The next three fields are Module Type, Array Type and System Losses (%).  Use the info button to the right of each to learn more (and see pix!), if you like. For purposes of exercises in this class please use default settings [Standard, Fixed (open rack) and 14].
  • The next two fields are closely related..

Tilt (deg): describes the angle of the array relative to horizontal (ground).  A flat array (like on a flat roof) has a tilt of 0 degrees. A vertical array would have a tilt of 90 degrees.

Azimuth (deg): describes which way an array faces. An array that is installed facing South has an azimuth of 180 degrees. Facing North, it would be 0 degrees.

The amount of energy an array gets from the sun depends on the amount solar radiation coming from the sun and how directly the array is facing the sun. PVWatts uses data from the selected weather station for your location to predict the amount of solar radiation available. The unit for this is energy per area per day (kWh/m2/day). PVWatts uses your location, tilt angle and azimuth to determine how directly the sun’s energy is hitting the array how much of the sun’s energy is available to generate electricity. (For example, when the sun is high in the sky, an array with a lower tilt will receive more of the sun’s energy than an array at a steeper tilt. When the sun in lower in the sky, an array at a steeper angle will receive more of the sun’s energy. Similarly, for azimuth, we’d want an array facing the path of the sun. In the Northern Hemisphere, an array would gain the most energy is facing south. In the Southern Hemisphere, facing north would be best.) Not required, but if you’d like more information, here’s a terrific resource, Solar Radiation on a Tilted Surface [21]. [22]

Using the info buttons in PVWatts, read documentation related to the two fields Tilt (deg) and Azimuth (deg). For now, leave these fields at default values (20 and 180).

3.     Using the arrow on the right, Go to PVWatts Results.

Ta da! This table gives the PVWatts prediction for how this photovoltaic system will perform. These estimates take into account historical weather data for your location (to determine how much solar radiation is available), the size of your system (kW), the direction your array is facing (tilt and azimuth) and several other factors we left at default values (module type, array type and system losses).

Take a few minutes to consider what this table is telling you.

  • The second column is the amount of solar radiation at your location. In photovoltaic terms, this is available fuel! Notice that it varies by month. Makes sense, right? Look at the unit of measure carefully: energy per area per day.
  • The next column is “AC energy.” This is the electricity coming out of the photovoltaic system—the DC electricity from the array has passed through an inverter and now is exactly the same as electricity from the utility company. It is measured in kWh. Notice that on months when the solar radiation is highest, the amount of energy generated is highest. And vice versa.
  • For this class, please ignore the Energy Value column. The NREL parameters used to generate these values are not good indicators for purposes of this course.
  • The bottom row of the table provides Annual results, including estimate of the total AC Energy this system will generate per year (a long term average).

4.    Notice at the top left of the screen that you can Print Results. Print your results and then do some experiments…(You don't submit this work. It is to help you build understanding.)

  • For the same location (Harrisburg, PA), enter all the same data except double the system size (use 8 instead of 4). Compared to your printed results, how are these results different?
  • For the same location (Harrisburg, PA), enter all the same data (back to 4 kW), except change the tilt (use 40). Compared to your printed results, how are these results different?
  • For the same location (Harrisburg, PA), enter all the same data (4 kW and 20 degree tilt), except change the azimuth to 135 (southeast). Compared to your printed results, how are these results different?
  • Go back to all original data (4 kW, 20 degree tilt and 180 azimuth), but change location to “Anchorage, AK” (Alaska). Compared to your printed results, how are these results different?
  • Experiment more if you like!

You will be using PVWatts to complete many questions on the Lesson 2 Activity. Use the demonstration above to be sure you understand the concepts. If you have questions, post them to the Questions about EGEE 401 discussion.

Lesson 2 Activity

Complete the Lesson 2 Activity. (It's in CANVAS, under Modules, Unit 1.)

Unless noted otherwise, correct answers come directly from the content of this lesson and assigned readings.

The Activity consists of a variety questions of different types, which may include true/false, multiple choice, multiple select, fill in the blank, ordering, and short answer. The point value varies and is indicated for each. Some questions are graded automatically, and some are manually graded.

The quiz is not timed, but does close at 11:59 pm Eastern Standard Time on the due date as shown in CANVAS.

Questions that are "manually graded" will be scored based on the correctness and quality of your answers. Thinking is good! Try to make your answers as orderly and clear as possible. Short is good, as long as you fully answer the question. Help me understand what you are thinking, and include data where relevant.

Numbers must ALWAYS be accompanied by units of measure (not "300" but "300 kW").

Proofread and spell check your work.

Unit 1 Discussion

Unit 1 Discussion: "Energy's Pace of Change"

Energy Scale vs Year. from 6000 bc until near the industrial revolution humans used muscle and firewood. There is a very steep incease in use of fossil fuels with a very sharp drop off in about 2500 ad. The figure has a question mark after 2500 ad.
Figure 2.9: The Transient Phenomenon of Fossil Fuels.
Enter image credit here

Most discussions in the remarkable trajectory of human development in the past few years label the phenomenon the Industrial Revolution. This term is apt enough, although it emphasizes the industrious nature of clever humans. An equally important factor – if not more so –has been the abundant supply of cheap surplus energy in the form of fossil fuels. Coal fueled the early stages of the Industrial Revolution, opening the door to accelerated energy-resource discovery and exploitation. Indeed, the first major application of coal was to power steam engines used to pump water out of mines in order to gain access to more coal. Perhaps the Coal Revolution would more accurately represent the transformational change marked by the 19th century.

Fossil fuel stocks are known to be finite and by most accounts their extraction rates will peak this century. Thus in the long view it is a near certainty that the current age will be known to history as the Fossil Fuel Age. It is the time when humans discovered Earth's battery – solar-charged over millions of years – and depleted it fast enough to effectively constitute a short circuit.

During this epoch, our unprecedented capacity to process materials, manufacture goods, create a "built environment," and revolutionize agricultural productivity has translated into a world of spectacular accomplishments, advanced scientific knowledge, technology that an earlier generation might call magic, sustained economic growth, and a surging population of 7 billion industrially fed human beings. These feats would not have been possible without the bounty of fossil fuels.

In this light, our present state can be seen as a reflection of historically available energy. If depicted in a schematic fashion over the course of a civilization-scale timeline, the general history and future of fossil fuel use will very likely appear as a sharp spike. (See Figure [above]). Humanity now sits near the apex of the brief fossil fuel energy explosion and prepares to enter an untested regime of unprecedented scale: the loss of a resource that has been unquestionably vital to growth and development.

The passage above is excerpted from "Beyond Fossil Fuels: Assessing Energy Alternatives," an essay by T.W. Murphy, an Associate Professor of Physics at the University of California/San Diego. It is Chapter 15 of a book entitled, "Is Sustainability Still Possible?" published in 2013 by the Worldwatch Institute. I find this book to be an extraordinary collection of well-written and researched essays on a wide range of topics. It is not required that you purchase this book for this course, but it is near the top of my list of recommended reading. You may wish to check it out!


The title of this course is Energy in a Changing World. "Changing" is an understatement! My grandfather was born in 1903. He loved to remark that in the course of his lifetime the Wright brothers took their first flight and a man walked on the moon. Incredible. In terms of energy, let's consider where we were just "yesterday" and think about how quickly "tomorrow" will come.

It is natural to think things have always been as they are and will continue to be so. But we don't have to look back very far to find a world that was very different from today's, especially when we focus on changes related to our use of energy. When we look forward and ponder future energy options, it is necessary to be open and realistic about the rate and scope of change that is possible, in fact, probable.

Take a minute to look at Figure 15-1. The steep slopes of the spike shows how rapidly our use of fossil-fuel has increased, and will then decrease. In energy terms, the world was very different just a generation ago and the one before that--our parents' world and our grandparents' world.

My mother talks about when her parents first had central heating installed. Before that, only two rooms in the house were heated. Growing up, my mother never had a heated bedroom. My grandfather chopped and hauled wood and used coal purchased locally. It was all heavy hard work. Suddenly, all he had to do was push a little lever on the thermostat and the whole house would get warm. My mother said for years, he would stand by the thermostat and marvel at what a miracle it was, so grateful for the ease and ability to keep his family warm. My grandmother grew up traveling in a horse-drawn buggy. Her mother was an excellent driver, they say! She used to laugh about buying jello from a door-to-door salesman, before they had a refrigerator! (Life without a refrigerator. Can we imagine that?) My mother's family was typical, maybe considered "well to do" in their small rural community. They were the first in the area to have a telephone. Neighbors would come from all around to use the phone that still hangs in the central hall. I remember when they got an air conditioner, in the 1960s. It was installed in a window in the den and they'd turn it on for an hour or so on hot afternoons. As hot and humid as it was in South Carolina, this one window unit was the only air conditioning in any of my family homes (counting our own home and my grandparents) for my entire childhood. Sounds like I'm 220 years old, right? I'm 55.

For this Discussion, we're going to collect and share stories about the changing use of energy in recent generations. As we look back on those stories, we're going to spin the stage and "ask" our grandchildren to look back on our times. What will they find noteworthy about the way we use energy?

  • Interview. Find someone in your world who is at least 75 years old and ask them to describe how the use of energy has changed in their lifetime. Ask them to think about their childhood and then to think about now. Consider heating and air conditioning, transportation, infrastructure, appliances, and other related topics. Do they remember stories from their parents on these topics? See what you can learn interesting and share it in your posting. Give us some points of reference, including where the person lived, rural or urban, etc. (You are not required to give any personal details.) If you do not have access to anyone to interview, you may share and discuss an interesting story, image or fact found through your own research that demonstrates how the role of energy in our lives has changed over the last 100 years.
  • Personal Reflection. Imagine it is 50 years from now and these same questions are being asked of you by your grandchildren. "Describe how the use of energy changed over your lifetime." In 50 years, looking back, what would we say about our use of energy today? What would be interesting, surprising, noteworthy? (Be sure to keep the focus on looking back at today. Don't put too much effort into describing the future. We'll go there in the last Discussion of this course!)
  • Respond. Read the postings of others and respond to at least one.
Post your work in the Discussion, "Energy's Pace of Change." You'll find it in CANVAS, under Modules, Unit 1. Please follow full instructions there.

Include both the Interview and your personal reflection in your initial posting.

Please see course calendar in CANVAS for due date of your FIRST posting and date when discussion ends (graded participation ends, all replies must be in).

Grading criteria

You will be graded on the quality of your participation. Be interesting and interested! Please see Syllabus for full Discussion grading criteria.

Summary and Final Tasks

Summary

In this lesson, you examined many energy transformations and the idea of energy efficiency – the amount of "useful" energy relative to the energy that was input. You also started to think about and discuss the "big picture" of the challenges facing our energy industry and the environment.

Reminder—Complete all of the lesson tasks!

You have finished Lesson 2. Double-check the list of requirements on the Lesson 2 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.


Source URL: https://www.e-education.psu.edu/egee401/content/p2.html

Links
[1] http://chemistry.elmhurst.edu/vchembook/
[2] http://tonto.eia.doe.gov/energyexplained/index.cfm?page=biomass_home%5C%20
[3] http://www.teachersdomain.org/resource/tdc02.sci.life.stru.photosynth/
[4] http://www.dummies.com/how-to/content/nuclear-fission-basics.html
[5] http://www.world-nuclear.org/info/inf66.html
[6] http://www.explainthatstuff.com/generators.html
[7] http://www.electricityforum.com/electricity-generation.html
[8] https://www.e-education.psu.edu/egee401/sites/www.e-education.psu.edu.egee401/files/image/lesson02/Battery_LD.html
[9] http://www.qrg.northwestern.edu/projects/vss/docs/Power/2-how-do-batteries-work.html
[10] http://www.nrel.gov/data/pix/searchpix.php
[11] http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDsQFjAA&url=http%3A%2F%2Ffiles.sharpusa.com%2FDownloads%2FSolar%2FProducts%2Fsol_dow_NUU240F2.pdf&ei=o-IOT7bSBon10gGRuNmRAw&usg=AFQjCNGi_VOn5x-U8sc9FZ-UkXpHUi3Twg&sig2=heHo4x7CCd9uzZI1l_jQlw
[12] http://www.ashrae.org/education/page/1455#1
[13] http://www.ashrae.org/resources--publications/free-resources/top-ten-things-about-air-conditioning#2
[14] http://www.eia.gov/tools/faqs/faq.cfm?id=98&t=3
[15] http://www.fueleconomy.gov/feg/evtech.shtml
[16] http://www.ahrinet.org/site/588/Homeowners/Save-Energy/Seasonal-Energy-Efficiency-Ratio
[17] http://www.energystar.gov/index.cfm?c=about.ab_index
[18] http://www.energystar.gov/
[19] http://home.howstuffworks.com/home-improvement/construction/green/energy-star.htm
[20] http://pvwatts.nrel.gov/
[21] http://www.pveducation.org/pvcdrom/properties-sunlight/solar-radiation-tilted-surface
[22] http://www.pveducation.org/pvcdrom/properties-of-sunlight/solar-radiation-on-tilted-surface