POE Review 2
Lesson 1.3 Energy Applications - Overview
Preface
Today’s consumer demands effective energy management. Consumers rely on efficient and accessible energy to power automobiles,
homes, appliances, and electronics. National trends regarding energy management include appliance and home energy star ratings
and the development of alternative and renewable energy sources. Energy conservation states that energy cannot be gained or
destroyed but instead transferred from one form to another. Understanding how energy is transferred from one form to another
allows engineers to design efficient applications utilizing energy. We know that many sources of energy won’t last forever and that
many sources have negative consequences on the environment. In the past individuals were forced to harness power that humans
or animals created from the energy stored in food. Power could also be harnessed from surrounding resources like wind, flowing
water, heat from the sun, or from combustible materials like wood.
This lesson is designed to provide students with an opportunity to investigate thermo energy and alternative energy applications.
Students will explore and gain experiences relating to solar hydrogen systems and thermo energy transfer through materials.
Understandings
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4.
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8.
Energy management is focused on efficient and accessible energy use.
System energy requirements must be understood in order to select the proper energy source.
Energy systems can include multiple energy sources that can be combined to convert energy into useful forms.
Hydrogen fuel cells create electricity and heat through an electrochemical process that converts hydrogen and
oxygen into water.
Solar cells convert light energy into electricity by using photons to create electron flow.
Thermodynamics is the study of the effects of work, thermo energy, and energy on a system.
Thermal energy can transfer via convection, conduction, or radiation.
Material conductivity, resistance, and energy transfer can be calculated.
Knowledge and Skills
It is expected that students will:
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Test and apply the relationship between voltage, current, and resistance relating to a photovoltaic cell and a
hydrogen fuel cell.
Experiment with a solar hydrogen system to produce mechanical power.
Design, construct, and test recyclable insulation materials.
Test and apply the relationship between R-values and recyclable insulation.
Complete calculations for conduction, R-values, and radiation.
Essential Questions
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5.
What limitations affect electricity production using solar cells?
What limitations affect electricity production using hydrogen fuel cells?
How can system configuration affect voltage and current?
How does thermodynamics relate to energy and power?
What are some everyday examples of the First and Second Laws of Thermodynamics?
Lesson 1.3 Energy Applications - Key Terms
Term
Definition
Active Solar Energy
Collection
A type of system that uses circulating pumps and fans to collect and distribute heat.
Alternative Energy
Any source of energy other than fossil fuels that is used for constructive purposes.
Ampere
The unit of electric current in the meter-kilogram-second system of units. Referred to as amp and symbolized as
A.
Conduction
The transfer of heat within an object or between objects by molecular activity, without any net external motion.
Convection
Process by which, in a fluid being heated, the warmer part of the mass will rise and the cooler portions will sink.
Current
The net transfer of electric charge (electron movement along a path) per unit of time.
Electrical Energy
Energy caused by the movement of electrons.
Electricity
The flow of electrical power or charge.
Electromagnetic Energy
Energy caused by the movement of light waves.
Electrolysis
The process separating the hydrogen-oxygen bond in water using an electrical current.
Energy
The ability to do work.
Entropy
The function of the state of a thermodynamic system whose change in any differential reversible process is
equal to the heat absorbed by the system from its surroundings divided by the absolute temperature of the
system.
First Law of
Thermodynamics
The law that heat is a form of energy, and the total amount of energy of all kinds in an isolated system is
constant; it is an application of the principle of conservation of energy. Also known as conservation of energy.
Fuel Cell Stack
Individual fuel cells that are combined in series.
Heat
Energy in transit due to a temperature difference between the source from which the energy is coming and a
sink toward which the energy is going.
Kelvin
A unit of absolute temperature and symbolized as K. Formerly known as degree Kelvin.
Line of Best Fit
A straight line that best represents all data points of a scatter plot. This line may pass through some, all, or none
of the points displayed by the scatter plot. Also referred to as a Trend Line or Regression Line.
Ohm
The unit of electric current in the meter-kilogram-second system of units. Symbolized as Ω.
Ohm’s Law
States that the direct current flowing in an electric circuit is directly proportional to the voltage applied to the
circuit.
Passive Solar Energy
Collection
Systems that do not make use of any externally powered, moving parts, such as circulation pumps, to move
heated water or air.
Product Development
Stages a product goes through from concept and use to eventual withdrawal from the market place.
Lifecycle
Radiation
The process by which energy is transmitted through a medium, including empty space, as electromagnetic
waves. This energy travels at the speed of light. This is also referred to as electromagnetic radiation.
Renewable Energy
A resource that can be replaced when needed.
Resistance
The opposition that a device or material offers to the flow of direct current.
R-value
The measure of resistance to heat flow.
Second Law of
Thermodynamics
A general statement of the idea that there is a preferred direction for any process.
Temperature
A property of an object which determines the direction of heat flow when the object is placed in thermal contact
with another object.
Thermal Equilibrium
Refers to the property of a thermodynamic system in which all parts of the system have attained a uniform
temperature which is the same as that of the system’s surroundings.
Thermodynamic System
A part of the physical world as described by its thermodynamic properties such as temperature, volume,
pressure, concentration, surface tension, and viscosity.
Thermodynamics
The study of the effects of work, heat, and energy on a system.
U-value
A measure of thermal transmittance through a material.
Volt
The unit of potential difference symbolized as V.
Voltage
The potential difference measured in volts. The amount of work to be done to move a charge from one point to
another along an electric circuit.
Zeroth Law of
Thermodynamics
A law that if two systems are separately found to be in thermal equilibrium with a third system, the first two
systems are in thermal equilibrium with each other; that is, all three systems are at the same temperature. Also
known as thermodynamic equilibrium.
We can see here the characteristic curve of the fuel cell. The characteristic curve of a fuel cell is the relationship between the current density and the cell
voltage. Notice a sharp fall from the ideal cell voltage immediately following open circuit. This is followed by a somewhat linear decline in cell voltage.
This is followed by a rapid drop off in cell voltage.
The primary factors affecting the curve are listed below. Each of these losses contributes to the decline in cell voltage.
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Activation losses are a result of the slow speed of the reactions taking place.
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Fuel crossover and internal currents is a result of fuel which crosses through the membrane, not contributing to the
chemical redox reaction, thus not contributing to the production of electricity.
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Ohmic losses are a direct relationship to the combined resistance of the various components within the fuel cell circuit. This
includes the material of the electrodes, the membrane, and the various interconnections.
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Mass transport, often called concentration losses, is a result of a reduction
of the concentration of hydrogen and oxygen on the electrode surface. This is due to the failure to transport the required
gases to the electrode surfaces.
By careful design in all of the components involving science, engineering, and the technical trades, these losses can be minimized resulting in
Radiation: The process by which energy is transmitted
through a medium, including empty space, as
electromagnetic waves. This energy travels at the speed of
light. This is also referred to as electromagnetic radiation
(EM radiation). One of the most common examples of this
is the heat transferred from the Sun to the Earth.
Convection: Process by which, in a fluid being heated, the
warmer part of the mass will rise and the cooler portion
will sink. If the heat source is stationary, convection cells
may develop as the rising warm fluid cools and sinks in
regions on either side of the axis of rising. Put another
way: Convection is the transfer of heat energy occurring by
a movement of currents; this typically occurs in a gas or
liquid state.
Conduction: The transfer of heat within an object or
between objects by molecular activity, without any net
external motion. This transfer of heat works better in solids
than liquids. Put another way: Conduction is the transfer of
heat by the movement of warm matter. For example, a
metal spoon placed in a hot cup of soup will feel warm to
your hand because the heat from the soup is conducted
through the spoon.
Lesson 1.4 Design Problem - Overview
Preface
Problems exist everywhere, and they vary in their degree of complexity and importance. Regardless of how problems are identified
or from where they come, engineers use the design process to creatively and efficiently solve problems.
Solutions to problems are sometimes created by teams. These teams work together, constantly communicating with each other, to
create the desired product. The team may receive a problem for which they are expected to create a solution with very few
constraints. This allows the team to think creatively and use their ingenuity.
In this lesson students will work in teams to solve a design problem that focuses on energy and power. They will use their prior
knowledge to create a solution to the problem. It is important for students to understand that an acceptable solution is one that fits
the constraints and specifications of the design brief.
Understandings
1.
Design problems can be solved by individuals or in teams.
2.
Engineers use a design process to create solutions to existing problems.
3.
Design briefs are used to identify the problem specifications and to establish project constraints.
4.
5.
Teamwork requires constant communication to achieve the desired goal.
Design teams conduct research to develop their knowledge base, stimulate creative ideas, and make informed decisions.
Knowledge and Skills
It is expected that students will:
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Brainstorm and sketch possible solutions to an existing design problem.
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Create a decision making matrix for their design problem.
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Select an approach that meets or satisfies the constraints provided in a design brief.
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Create a detailed pictorial sketch or use 3D modeling software to document the best choice, based upon the design team’s
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decision matrix.
Present a workable solution to the design problem.
Essential Questions
1.
What is a design brief and what are design constraints?
2.
Why is a design process so important to follow when creating a solution to a problem?
3.
4.
What is a decision matrix and why is it used?
What does consensus mean, and how do teams use consensus to make decisions?
Lesson 1.4 Design Problem - Key Terms
Terms
Definition
Accuracy
The condition or quality of being true, correct, or exact; precision; exactness.
Assembly
A group of machined or handmade parts that fit together to form a self-contained unit.
Brainstorming
A group technique for solving problems, generating ideas, stimulating creative thinking, etc., by unrestrained
spontaneous participation in discussion.
Component
A part or element of a larger whole.
Consensus
A general agreement.
Constraint
A limit to a design process. Constraints may be such things as appearance, funding, space, materials, and human
capabilities.
Decision Matrix
A tool for systematically ranking alternatives according to a set of criteria.
Design Brief
A written plan that identifies a problem to be solved, its criteria, and its constraints. The design brief is used to
encourage thinking of all aspects of a problem before attempting a solution.
Design
Modification
A major or minor change in the design of an item, effected in order to correct a deficiency, to facilitate production, or to
improve operational effectiveness.
Design Process
A systematic problem-solving strategy, with criteria and constraints, used to develop many possible solutions to solve a
problem or satisfy human needs and wants and to winnow (narrow) down the possible solutions to one final choice.
Design Statement A part of a design brief that challenges the designer, describes what a design solution should do without describing how
to solve the problem, and identifies the degree to which the solution must be executed.
Designer
A person who designs any of a variety of things. This usually implies the task of creating drawings or in some way using
visual cues to organize work.
Open-Ended
Not having fixed limits; unrestricted; broad.
Pictorial Sketch
A sketch that shows an object’s height, width, and depth in a single view.
Problem
Statement
A part of a design brief that clearly and concisely identifies a client’s or target consumer’s problem, need, or want.
Purpose
The reason for which something is done or for which something exists.
Sketch
A rough drawing representing the main features of an object or scene and often made as a preliminary study.
Solid Modeling
A type of 3D CAD modeling that represents the volume of an object, not just its lines and surfaces. This allows for
analysis of the object’s mass properties.
Target Consumer A person or group for which product or service design efforts are intended.
Team
A collection of individuals, each with his or her own expertise, brought together to benefit a common goal.
One way to define the problem is through the
use of a design brief.
This concise document (no more than one
page) identifies the client, clearly states
his/her problem or need, details the degree to
which the engineer will carry out the solution,
and lists the rules and limits within which the
engineer must perform.
A decision matrix is used to compare design
solutions against one another using specific
criteria. Design problem constraints are
identified by the customer in the workplace.
For classroom purposes, the student teams
will be provided the constraints and will be
required to develop a decision matrix.
A decision matrix is a design tool that may
be used multiple times throughout a design
process.
Lesson 2.1 Statics - Overview
Preface
Statics is the basis for the study of engineering mechanics and specifically rigid-body mechanics. Statics is concerned
with the equilibrium of bodies that are at rest or that move at a constant velocity. Using measurements of geometry and
force, Archimedes studied statics concepts in ancient Greece. Most of his work centered on simple machines for
construction of buildings.
In this lesson students will learn how to identify and calculate forces acting on a body when it is in static equilibrium.
Students will calculate internal and external forces of a truss. They will use this knowledge to design, build, and test their
own truss designs.
Understandings
1. Laws of motion describe the interaction of forces acting on a body.
2. Structural member properties including centroid location, moment of inertia, and modulus of elasticity are important
considerations for structure design.
3. Static equilibrium occurs when the sum of all forces acting on a body are equal to zero.
4. Applied forces are vector quantities with a defined magnitude, direction, and sense, and can be broken into vector
components.
5. Forces acting at a distance from an axis or point attempt or cause an object to rotate.
6. In a statically determinate truss, translational and rotational equilibrium equations can be used to calculate external
and internal forces.
7. Free body diagrams are used to illustrate and calculate forces acting upon a given body.
Knowledge and Skills
It is expected that students will:
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Create free body diagrams of objects, identifying all forces acting on the object.
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Mathematically locate the centroid of structural members.
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Calculate moment of inertia of structural members.
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Differentiate between scalar and vector quantities.
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Identify magnitude, direction, and sense of a vector.
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Calculate the X and Y components given a vector.
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Calculate moment forces given a specified axis.
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Use equations of equilibrium to calculate unknown forces.
Use the method of joints strategy to determine forces in the members of a statically determinate
Essential Questions
1. Why is it crucial for designers and engineers to construct accurate free body diagrams of the parts and structures that
they design?
2. Why must designers and engineers calculate forces acting on bodies and structures?
3. When solving truss forces, why is it important to know that the structure is statically determinate?
Lesson 2.1 Statics - Key Terms
Term
Definition
Cable
A strong rope, usually made of metal, designed to have great tensile strength and to be used in
structures.
Centroid
The geometric center of an area.
Compression Force
A body subjected to a push.
Concurrent Force
Systems
A force system where all of the forces are applied at a common point on the body or having their
lines of action with a common intersection point.
Cross-Sectional Area
A surface or shape exposed by making a straight cut through something at right angles to the
axis.
Direction
The direction of a vector is defined by the angle between a reference axis and the arrow’s line of
direction.
Fixed Support
A support that prevents translation and rotation in a beam.
Flange
A broad ridge or pair of ridges projecting at a right angle from the edge of a structural shape in
order to strengthen or stiffen it.
Free Body Diagram
A diagram used to isolate a body from its environment, showing all external forces acting upon it.
Gusset
A plate or bracket for strengthening an angle in framework.
Joint
The connection points of members of a truss.
Magnitude
The absolute value of a number.
Member
Slender straight pieces of a truss connected by joints.
Method of Joints
A method of analysis of trusses which constructs free body diagrams of each joint and determines
the forces acting in that joint by considering equilibrium of the joint pin.
Moment
The turning effect of a force about a point equal to the magnitude of the force times the
perpendicular distance from the point to the line of action from the force.
Moment of Inertia
A mathematical property of a cross section that is concerned with a surface area and how that
area is distributed about a centroidal axis.
Newton’s First Law
Every body or particle continues at a state of rest or uniform motion in a straight line, unless it is
compelled to change that state by forces acting upon it.
Newton’s Second Law The change of motion of the body is proportional to the net force imposed on the body and is in
the direction of the net force.
Newton’s Third Law
If one body exerts a force on a second body, then the second body exerts a force on the first
body which is equal in magnitude, opposite in direction, and collinear.
Pinned Support
A support that prevents translation in any direction.
Planar Truss
A truss that lies in a single plane often used to support roofs and bridges.
Resultant Force
The resultant of a system of force is the vector sum of all forces.
Roller Support
A support that only prevents a beam from translating in one direction.
Scalar
A physical quantity that has magnitude only.
Sense
The sense of a vector is the direction of the vector relative to its path and indicated by the location
of the arrow.
Simple Truss
A truss composed of triangles, which will retain its shape even when removed from supports.
Static Equilibrium
A condition where there are no net external forces acting upon a particle or rigid body and the
body remains at rest or continues at a constant velocity.
Statically
Indeterminate
A structure or body which is over-constrained such that there are more unknown supports than
there are equations of static equilibrium.
Structure
Something made up of interdependent parts in a definite pattern of organization, such as trusses,
frames, or machines.
Tension Force
A body subjected to a pull.
Vector Quantity
A quantity that has both a magnitude and direction.