University of San Diego

Appropriate Technology Micro-Electricity Generation

MENG 491W Senior Design Project Proposal

Amanda Berlinsky, Christina Callas, Logan Johnston, Rigoberto Laborin10/16/2008

MENG 491W Fall 2008

Table of Contents1. Context....................................................................................................................................................4

1.1. Background of Need.........................................................................................................................41.2. Customer Need Statement...............................................................................................................51.3. Literature Review.............................................................................................................................5

1.3.1. Prior Work..................................................................................................................................51.3.2. Patents.......................................................................................................................................51.3.3 Codes and Standards:.................................................................................................................61.3.4. Related Technology:..................................................................................................................6

2. Problem Definition..................................................................................................................................62.1. Customer Requirements...................................................................................................................7

2.1.1. Form...........................................................................................................................................72.1.2. Fit...............................................................................................................................................72.1.3. Function.....................................................................................................................................7

2.2. Assumptions.....................................................................................................................................72.3. Constraints........................................................................................................................................72.4. Customer Requirements Schematic..................................................................................................82.5. Test/Evaluation Plan for all Requirements and Constraints..............................................................8

3. Concept Development.............................................................................................................................83.1. Overview...........................................................................................................................................8

3.1.1. Creative Strategies.....................................................................................................................83.1.2. Governing Principles .................................................................................................................9

3.2 Synthesis and Analysis of Overall Concept.........................................................................................93.2.1. Concept 1: Steam Powered Turbine........................................................................................103.2.2. Concept 2: Peltier Junctions.....................................................................................................113.2.3. Concept 3: Stirling Heat Engine...............................................................................................113.2.3.a Alpha Stirling Heat Engine.....................................................................................................123.2.3.b. Concept 3: Beta Stirling Heat Engine....................................................................................123.2.3.c Concept 3: Gamma Stirling Heat Engine...............................................................................133.2.4.Concept 4: DC Generator..........................................................................................................143.2.4a. Concept 4: Brushed DC Generator.........................................................................................143.2.4b. Concept 4: Brushless Generator............................................................................................153.2.5 Overall Concept Synthesis: Stove Design..................................................................................163.2.5a Justa Stove..............................................................................................................................163.2.5b Rocket Stove...........................................................................................................................164.1.2. Design Schematics...................................................................................................................21

4.2..........................................................................................................................................................22Functional Specifications.......................................................................................................................224.3. Physical Specifications....................................................................................................................234.4. Product QFD...................................................................................................................................244.5. Subsystems.....................................................................................................................................24

4.5.1 Stove/Engine Interface.............................................................................................................254.5.2 Stirling Engine...........................................................................................................................25

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4.5.3 Power Transmitter....................................................................................................................264.5.4 DC Generator............................................................................................................................264.5.5 Voltage Regulator.....................................................................................................................27

4.6 Design Deliverables.........................................................................................................................275. Project Plan............................................................................................................................................27

5.1 Research..........................................................................................................................................275.2. Critical Function Prototypes............................................................................................................27

5.2.1. Critical Design Functions..........................................................................................................275.2.2. Critical Values..........................................................................................................................285.2.3. Critical Measurements.............................................................................................................28

5.3 Design..............................................................................................................................................285.3.1 Justa Stove/Heat Engine Interface............................................................................................285.3.2 Pistons and Cylinder..................................................................................................................285.3.3 Regenerator..............................................................................................................................295.3.4 Linkage System.........................................................................................................................295.3.5 Transmission System.................................................................................................................305.3.6 Generator/ Voltage Regulator..................................................................................................30

5.4. Construction...................................................................................................................................305.5 Testing.............................................................................................................................................315.6 Project Deliverables.........................................................................................................................325.7 Schedule..........................................................................................................................................335.8 Budget.............................................................................................................................................345.9 Personnel.........................................................................................................................................34

6. References.............................................................................................................................................367. Appendices………………………………………………………………………………………………………………………………………..397.1 Team Member Resumes………………………………………………………………………………………………………………….397.2 Justa Stove Construction………………………………………………………………………………………………………………….40

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1. Context

1.1. Background of NeedThe customers for this project are people in developing countries that lack electricity and generally live in poor, rural, agrarian communities. The majority of them “are poor villagers surviving on less than adequate diets, whose infant mortality is an order of magnitude higher than in the developed world and whose life expectancy is as much as three decades shorter” (Alam). Because the countries are not fully industrialized, access to modern technology is limited and the sophistication of common tools is relatively low.

The international community has recognized the importance of bringing power into developing nations as a step in lessening the strains of poverty. Without electrical power developing countries are unable to modernize and use many time and labor saving devices. While powering an entire nation requires funding and infrastructure beyond the scope of this project, the electricity required to make a difference to an individual is small: “it has been estimated that each person needs the energy equivalent of only 100 watts of electricity to meet their most basic energy needs.” (Reddy)

The stakeholders of this project include nonprofit organizations (ie Engineers Without Borders, World Vision), and possibly governments that would be responsible for producing, distributing, and selling the device to end users. These organizations’ mission is to improve living conditions in developing countries through the use of appropriate technology. Designing for appropriate technology introduces many complex constraints and principles unique from other design situations. In the context of developing countries, appropriate technology is the pursuit of affordable solutions to meet community needs that can be used and maintained by the end users. For a design to be successfully incorporated into the community and provide significant, long-term benefits respect and attention must be paid to all of facets of the customer’s situation.

The aim of this project is to integrate with ongoing appropriate technology projects, particularly the introduction of high efficiency stoves into developing countries. Traditional biomass stoves have operated as a sufficient cooking method and light source for centuries. However, they are not fuel efficient, are often a fire hazard, and expose users to harmful smoke. Smoke inhalation is of great concern because cooking occurs daily, often in small rooms with low ceilings. In addition to harming women who cook, children and babies are often present inhale as much smoke as their mothers. “In total, biomass smoke exposure causes nearly 2 million deaths annually, the equivalent of 1 life lost every 20 seconds, or nearly 3% of the global disease burden each year.” (Donohoe) In an effort to address the problems of traditional stoves government and relief agencies have engineered more environmentally friendly designs. One drawback to these stoves’ design that the fire is completely enclosed which eliminates the primary source of light for many customers. This problem is an area that the micro-electricity generation device (M.E.G.) could also potentially address. A discussion of specific stoves designs is included in section 3.2.

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1.2. Customer Need StatementApproximately two billion people in developing countries live without electricity. (Bradbook) Access to electricity would help accomplish basic tasks and increase economic opportunities. Addressing this need would allow for the incorporation of low power devices such as a pump, small laptop, or light source into daily life and improve the standard of living. However, in order to provide long term benefits to the end users this project focuses on countries with some level of technological development and plans for industrialization.

1.3. Literature Review

1.3.1. Prior WorkHeat has been used as a means of producing electricity in many different ways. However, it appears that it has never been attempted in the context of appropriate technology for use with cooking stoves. This is largely because this project is a relatively novel combination of two ideas proposed by Engineers Without Borders.

1.3.2. PatentsThere are some potential stoves including rocket stoves, coal and wood-burning stoves, and cooking stoves. Below are examples of patented stoves, mainly cooking and coal-burning, that resemble the particular requirements of the stove.

Patents for cooking stoves:1. U.S. PATENT 4785: “Cooking Stove”; Inventor: Adam C. Conde; Patented: October 3, 1846

Description: The stove has two ovens, which are placed with one above the other, with a flue space between them. This is used for the passage of air that is heated by the action of the fire that is placed in the fire chamber. The heated air is then conducted through tubes that transport the heat into the apartment. Applicability and Shortcomings:Its design provides some of the simple uses people would need stoves for (ie. cooking and heating households). Also, the design gives some flexibility as to how to extract the energy from the product. However, the unique piping system might not be a common resource. This is a really old model, so it may be outdated.

2. U.S. PATENT 5,413,089: “Wood and Coal Burning Stove”; Inventor: Derik K. Andors, Robert W. Ferguson & Dane P. Harman; Patented: May 9, 1995.Description: This stove is used for heating homes by burning wood cleanly within current EPA standards. The stove is easily converted to burning coal. This solid fuel burning stove includes a firebox and a secondary combustion unit formed from high temperature insulation, refractive material mounted on the top and rear walls of the firebox. Applicability and Shortcomings:

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It is a common solid fuel stove for heating homes, which should be similar to what might be available. However, it is not necessarily a cooking stove. Therefore households might not have this model if they are only able to have one stove that has both applications.

Patent for Stirling Engine:3. U.S. PATENT 5,611,201: “Stirling Engine”; Inventor: William H.Houtman; Patented: March 8,

1997.Description: This Stirling Engine has multiple parallel cylinders that are used to create a dual action system. Applicability and Shortcomings: It has a reversible thermodynamic cycle; therefore it can be used as a means of delivering mechanical energy from a source of heat. This model may be too complex of a design to be used in developing countries.

1.3.3 Codes and Standards:

The design, manufacturing, and application of the product will adhere to the following codes and standards.

1. ASME EA-1-2008 – Energy Assessment for Process Heating Systems:2. ASME EA-4-2008 – Assessment for Compressed Air:3. E.P.A. Title 40, Part 60, Subpart AAA—Standards of Performance of New Residential Wood

Heaters

1.3.4. Related Technology:Although this specific design configuration is new, the idea of developing appropriate technology has been increasingly popular for the last few decades. One closely related project is the ST-5 engine created for developing countries by Stirling Technologies. The ST-5 unit consists of two parts: one is an external combustion Stirling engine and the other is a pair of burners designed to use traditional fuels. The ST-5 engine is very similar in theory to the project being proposed but it is a more complex design which requires a forced air blower which is initially run by a battery and a cooling fluid system.

Another related project is the recent effort to replace the light source eliminated by high efficiency stoves by producing inexpensive, heat driven LED lights. This product shares customers with the pproposed project but the work is not directly applicable because the lights only require one to two watts of power, a fraction of that needed to run a standard electric device. The technology used to convert heat into electricity in this application is sufficient for lights but cannot be altered to produce more power. However, the model the LED lights provide for successful work in appropriate technology may prove to be useful.

2. Problem Definition

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2.1. Customer Requirements

2.1.1. Form1. Visually appealing (L)

2.1.2. Fit 1. Must interface with electrical equipment (9 or 12 volts DC) (H)2. Must be able to be integrated into the intended stove type (H)3. Easily transported to location(M)4. Able to withstand temperatures ranging from 0°C to 40°C(M)

2.1.3. Function1. Convert heat from a high efficiency stove into at least 50 watts of electrical power (H)2. Work reliably (200 hours without service) (H)

3. Be safe to operate in close contact with people. (H)4. Low cost (affordable for ends users). (H)5. Operation is understandable to end users. (H)6. Basic maintenance can be performed with basic tools and techniques .(H)7. Allows stove to continue functioning for cooking purposes, (No more than 15% decrease in heat

output of stove)(. (H)8. No harmful exhaust. (M)9. Low noise levels (<70dB). (L)

2.2. Assumptions

1. Team will not change or decrease the budget midstream.2. Customer requirements will not change midstream.3. Supplies will be delivered on time.4. Design team will be stable for design phase of project.5. High efficiency stoves are commonly used in developing countries.6. Developing countries have a need for electrical power.7. Safe space will be available for testing.

2.3. Constraints

1. Project budget must be no more than $800.2. Project must be finished within 8 months.3. Project design complexity must be within the capabilities of the design team.4. Project must meet all applicable codes, standards, and government regulations. 5. The device must be able to be constructed within Loma Hall.6. There must be necessary supervision when using equipment involving 25+ volts.

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7. There must be a low risk of injury to design team and other students.8. The project must be testable at USD; including the use of the heat source.9. The project must be able to be tested in a non-destructive, reliable manner.

2.4. Customer Requirements Schematic

Figure 1: Customer Requirements Schematic for a M.E.G. Device Consisting of a Heat Engine and Generator.

2.5. Test/Evaluation Plan for all Requirements and Constraints

Heat Engine

o Achieve the required mechanical work (rpm of a flywheel) to run a generator and output 50W or greater: Heat engine will be fixed to a heat source representative of a high efficiency stove and the rpm will be measured with a tachometer. The output torque will be measured by a Prony brake dynamometer.

M.E.G. Device

o Produce at least 50W of power of the desired voltage (9V and/or 12V): The complete device will be fixed to the testing heat source and the power output will be measured by a voltmeter, ammeter, and variable load device.

o Operate with a noise output of less than 80db: While the complete device is being run the noise will be measured with a decibel meter.

3. Concept Development

3.1 Overview

3.1.1. Creative Strategies Many creative strategies were employed to develop ideas for micro-electricity generation under the constraints of appropriate technology. Initially this included brainstorming and researching prior attempts. After the goals of the project were established as a foundation, group discussion led to a multitude of

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questions for research. Outside-the-box, “wild” thinking was also used because there was little prior work to use for inspiration.

3.1.2. Governing Principles The function of the design is governed by principles from a wide range of disciplines. These principles and their relation to the design are noted below.

Heat Engine

Thermodynamics (expansion and compression of the working fluid) Heat transfer (absorbing heat from the stove and rejecting it to the air, regenerator) Solid mechanics (component stress) Material properties (high temperatures, tribology) Dynamics/kinematics (piston-cylinder) Fluid mechanics (pumping) Combustion (Justa stove) Manufacturing (Stirling components that cannot be purchased) Machine Design (flywheel and linkages)

Generator

Electromagnetism (induced current)

One major hurdle for developing a design was the economic and practical constraints of appropriate technology. Because money is a scarce resource the product must provide a valuable service for an acceptable cost to the end users. Economics has no bearing on governing principles affecting the mechanics of a design but it carries significant weight in determining which designs are approved.

3.2 Synthesis and Analysis of Overall ConceptCreativity strategies were not used in a structured format for concept development. Instead, the group discussion naturally became a brainstorming session. In this stage of design our group benefited from the vague nature of the project statement and our own inexperience. Without any known solution we had no preconceptions of what the solution should be. The initial idea generation did not produce any solid solutions; rather the session progressed as a flow of questions which provided topics for research. This process is depicted in Figure 2 below.

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Figure 2. Creativity Flow Chart

3.2.1. Concept 1: Steam Powered Turbine

Design ConfigurationThe heat from the stove could be used to vaporize water which would be run through a steam turbine or through a steam engine similar to a steam locomotive. The mechanical work of the turbine could then be converted into electricity.

Advantages/Disadvantages Design configuration of a turbine is relatively simple Plenty of available information on the process Precision turbine makes the cost of including it in a design questionable Potentially corrosive steam

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Schematic

Figure 3: Input-Output Schematic for a Steam Powered Turbine

3.2.2. Concept 2: Peltier Junctions

Design ConfigurationPeltier junctions are thermoelectric devices that create voltage from a temperature difference.

Advantages/Disadvantages Have been successfully used in past appropriate technology projects Peltier junctions can produce a maximum power output of approximately five watts

Schematic

Figure 4: Input-Output Diagram for a Peltier Junction

3.2.3. Concept 3: Stirling Heat Engine

Design ConfigurationLike all heat engines, a Stirling engine takes advantage of a temperature difference (between the stove and the ambient air) to produce mechanical work.

Advantages/Disadvantages Closed cycle process which can utilize air as a working fluid Quiet to run, has no valves and few moving parts Abundance of information about them from commercial and hobbyist sources High thermal efficiency, due to the regenerator (an internal heat exchanger)

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High weight to power ratio relative to other types of engines

Schematic

Figure 5: Input-Output Diagram for a Stirling Heat Engine

3.2.3.a Alpha Stirling Heat Engine

Design ConfigurationAlpha Stirling engines use two separate power pistons. One piston is inside a hot cylinder and the other is in a cold cylinder.

Advantages/Disadvantages High power-to-volume ratio relative to other Stirling configurations Requires the movement of hot seals which wear significantly faster than cold seals

Schematic

Figure 6: Alpha Stirling Engine Schematic (Wikimedia.com)

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PP

DP

FW

CS

HS

CF

FW= FlywheelPP= Power PistonDP= Displacer PistonHS= Hot SectionCS= Cold SectionCF= Cooling Fins

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3.2.3.b. Concept 3: Beta Stirling Heat Engine

Design ConfigurationIn contrast to the Alpha, a Beta engine uses only one power piston in conjunction with a displacer piston located in the same cylinder.

Advantages/Disadvantages Displacer piston is a loose fit and requires less precision then a power piston Does not require the use of the hot, moving seals Power piston functions as a guide for the displacer piston so additional design is required to

constrain them

Schematic

Figure 7: Beta Stirling Engine Schematic (Wikimedia.com)

3.2.3.c Concept 3: Gamma Stirling Heat Engine

Design ConfigurationA Gamma engine is much like the Beta version pictured above except that the displacer and power pistons are located in separate cylinders. The pistons are connected to the same flywheel and the working fluid can flow between the two cylinders.

Advantages/Disadvantages

Power and displacer pistons are independently connected to the flywheel (simplified construction)

Requires no hot, moving seals

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DP

PP

FW

FW = FlywheelPP = Power PistonDP = Displacer PistonHS = Hot SectionCS = Cold SectionCF = Cooling Fins

C S HS

CF

ES: Expansion spaceCS: Compression SpaceP: Power pistonD: Displacer pistonR: RegeneratorC: CoolerH: Heater

Generator

Mechanical work(rotating shaft)

Voltage

Heat

Current

Noise

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Lower compression ratio than the other two Stirling types because of the increased dead space

Figure 8: Gamma Beta Stirling Engine Schematic (Institut fur Kolbenmaschinen)

3.2.4. Concept 4: DC Generator

Design ConfigurationThe most promising of the previous concepts are devices that convert heat into mechanical work which requires that another subsystem is added to convert mechanical work into electricity. This would be most practically accomplished by a generator. DC is preferred over AC for safety reasons.

Schematic

Figure 9: Input-Output Schematic for a Generator.

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3.2.4a. Concept 4: Brushed DC Generator

Design ConfigurationA wound armature is spun between two permanent magnets which creates a current. The current is transferred to two brushes which are pressed up against the commuter.

Advantages/Disadvantages Low in cost Brushes wear with time Generally bigger and heavier than most other generators

Schematic

Figure 10: Brushed DC Generator Schematic (orientalmotor.com)

3.2.4b. Concept 4: Brushless Generator

Design ConfigurationBrushless DC generators have magnets attached to a rotating spindle and stationary stators which pick up the electromagnetic forces and produce electrical energy.

Advantages/ Disadvantages High conversion efficiency of mechanical power to electrical energy and vice versa

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Schematic

Figure 11: Brushless DC Generator Schematic (orientalmotor.com)

3.2.5 Overall Concept Synthesis: Stove DesignIdeall, this device will be universal enough to be used with multiple stove designs. However, for the purposes of this project, one stove design must be selected for the device to work with. It is important to select a model that is widely used, creates sufficient heat to operate the device, and is configured to allow for the attachment of the device.

3.2.5a Justa Stove

Design ConfigurationThe basic design of a Justa stove includes: a centralized burning area where fuels such as wood can be burned, a hot chamber, and an exhaust pipe. The heat from the burned fuel rises into the hot chamber which focuses the heat onto the cooking surfaces. As the air cools and contracts it enters the exhaust pipe and leaves the stove.

Advantages/Disadvantages Relatively popular in underdeveloped countries Built from inexpensive, common materials Complete combustion because of high temperatures in the “elbow” combustion

chamber Heat is concentrated due to the pathway constraining heat flow Limited space available to attach the M.E.G. device

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Schematic

3.2.5b Rocket Stove

Design Configuration:This design also has a combustion chamber, which along with the help of the chimney allows this stove to create an additional draft that increases the temperature in the stove. The rocket stove is very similar to the Justa stove in that it creates a concentrated heat area.

Advantages/Disadvantages Needs minimal amounts of fuel, such as wood, because of its concentrated combustion. Compact nature makes it difficult to insert the hot section of the Stirling engine without

significantly decreasing air flow in the stove.

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Figure 12: Justa Stove Schematic (www.aprovecho.org)

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Schematic

Figure 13: Justa Stove Schematic (boingboing.net)

3.3. EvaluationDecision matrices were used to evaluate concepts discussed in Section 3.2 to observe which designs had good features and which did not adequately meet the customer requirements. Based on this analysis, shown in Table 1, a steam powered turbine was eliminated for its low score as was Peltier Junctions because the maximum power output was below the required range.

Table 1: Kepner-Tregoe Analysis for Engine selection

Features/ Selection Criteria

Construction Simplicity

Construction Tolerances Size Engine Feasibility Service

Life Efficiency Cost Overall Score

Weight Factor 8 8 6 10 6 10 8 Steam Powered

Turbine 3 3 2 6 1 5 1 184

Peltier Junctions 5 5 5 6 4 1 5 244Alpha 3 4 4 8 2 8 4 284Beta 5 3 5 9 5 8 4 326

Gamma 4 4 4 7 5 7 3 282

All Stirling engines require the addition of a generator to produce electrical power. A K-T analysis (in Table 2 below) was performed) on the two generators discussed in Section 3.2 in order to determine if one held a significant advantage over the others.

Table 2: Kepner-Tregoe Analysis for generator selection

Features/ Selection Criteria Appropriate Service Life Size Ease of Cost Overall

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Technology Integration ScoreWeight Factor 8 8 6 8 10

Brushless DC Generator 2 5 4 5 3 150Brushed DC Generator 5 4 4 5 5 186

The design matrices show the Stirling engine and brushed DC generator as leading concepts. Before proceeding with these ideas a rough analysis should be performed to determine overall design feasibility.

Feasibility AnalysisThere are several factors that determine the feasibility of using a Stirling engine and DC generator, this includes: the impact the device will have on the cooking performance and the efficiency of the heat engine.

Stirling Thermal EfficiencyThe theoretical efficiency of a Stirling engine is equal to the Carnot efficiency.

ηcarnot=1−T C

T H

Assuming a cold section temperature of 100°C and a hot section temperature of 1000°C the Carnot efficiency would be 90%. Obviously, this is an unattainable result but it does demonstrate the high theoretical efficiencies of Stirling engines. Research on power generating Stirling engines found efficiencies ranging from thirty to sixty percent.

Impact on Cooking PerformanceAssumptions:

Justa stove burns 1 kg of wood/hr (Aprovecho) Energy content of wood fuel is 15GJ/ton (Bioenergy) Generator conversion efficiency, ηgen=50 % Stirling engine thermal efficiency, ηStirling=20 % Generator output, Genout=100 W

The stove output can be found by the following calculation:

Qstove=(energy¿¿ wood)(woodtime )¿

Qstove=4600 W

The required engine input can be found by working backwards from the generator output:

Genout=100 W

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Gen¿=Genout

ηgen

Stirlingout=Gen¿

Stirling¿=Stirlingout

ηStirling

The results of the calculations are as follows:

Gen¿=200W

Stirlingout=200 W

Stirling¿=1000W

According to this analysis the Stirling engine would not significantly affect the cooking performance of the stove because it uses 20% of the stove heat output with conservative stove energy and Stirling engine efficiency estimates.

3.4. Refinements The brushed DC generator and Beta Stirling engine fared well in the K-T analysis and rough feasibility analysis. However, this is not enough to deem them the best solutions and they should be analyzed for potential improvements.

The major disadvantage of the Beta Stirling engine is that the power piston is used to guide the displacer piston. If the power piston is the only constraint on the displacer piston any error in the tolerance of the power piston will be propagated in the displacer. Also, the power and the displacer piston rods will be experience significant stress because they are responsible for preventing all unwanted, lateral motion unless another constraint is added.

One way to constrain the displacer piston is to add a guiding system, or track, on the inner wall of the Stirling engine cylinder. This can be accomplished by adding a soft material, which is heat resistant, to the inner wall at three locations (roughly 120 degrees apart) to secure the linear motion of the piston while also still allowing for air flow. Another solution would be to add metal piston guides concentrically around the displacer piston shaft at intervals. The metal will be resistant to the heat exposure and will also provide positive control over the displacer piston. These guides could be added after the cylinder was made or the cylinder and guides could be machined as one unit.

Also, the displacer piston is traditionally a solid but because of the difficulties associated with Beta engines and its large size this may be too heavy. This could be improved by using a hollow displacer piston which would decrease shaking and the overall weight of the heat engine.

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3.5. Selection In a K-T analysis, performed on the three Stirling engine types, the Beta design significantly out scores the others. The major advantages of a Beta engine over the Alpha is that it only requires one precision power piston and does not use hot, moving seals. Beta and Gamma engines are nearly identical in principle. However, the two-cylinder configuration of a Gamma engine creates a less compact design and a lower compression ratio which would increase the engine size. Considering each of these factors, and the concept evaluation, a Beta Stirling engine and a brushed DC generator are the most suitable for this project.

4. Design Specifications

4.1. Design Overview

4.1.1. DescriptionThe M.E.G. device is designed to utilize the heat produced from a Justa stove to generate electricity. In a broad sense this is accomplished by a Beta Stirling engine which uses the heat to produce mechanical work and DC generator which converts the work into electricity.

As described in section 3.2 a Stirling engine takes advantage of the temperature difference between a hot source (in this case from the heat provided by the stove), and a cold source (outside air). The cycle of a Beta Stirling engine is depicted below:

Figure 14. The red represents the hot section and the blue the cold. The cold section is shown with cooling fins.

The rotational energy of the flywheel is used to run a DC generator and produce electricity. The electricity is controlled by an inexpensive voltage regulator which produces a constant and safe level of

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electrical output. The overall target of the device is to produce a reliable, fifty watt power source to run lights or other small electrical equipment.

The subsystems include:

Justa stove/engine interface Piston and cylinder Regenerator Flywheel linkage Power transmitter DC generator Voltage regulator

4.1.2. Design SchematicsThe following schematics show the specific features and functions of the M.E.G. device design (Figure 2 and Figure 3 respectively).

Figure 15. Feature Schematic for the M.E.G. Device

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Figure 16. Function Schematic for the M.E.G. Device

4.2 Functional SpecificationsThe following design features and performance targets are directly linked to the customer requirements outlined in section 2.1.

FS1. Justa Stove:o FS1.1: Insulated, elbow shaped combustion chamber burns at 1500⁰C.

FS2. Stirling Heat Engine:o FS2.1: Closed cycle, one cylinder heat engineo FS2.2: Sealed at atmospheric pressure, air is the working fluid.o FS2.3: 19.37in3 expansion swept volume, 26.36in3 compression swept volume, (these

numbers are based on the estimated 4 in diameter cylinder).o FS2.4: Producing 200W at 200-400rpm. o FS2.5: Regenerator: steel wire mesh used to increase engine efficiency.o FS2.6: Thermal efficiency of 15% (minimum).

FS3. Power Transmitter:o FS3.1: Increases the 200-400rpm of the flywheel to 1500-2000rpm for the generator.

FS4. Brushed DC Generator:o FS4.1: Rpm range of 1000 to 2000. o FS4.2 : Conversion efficiency of 50%.o FS4.3 : Output of 24V and 2A.

FS5. Voltage Regulator:o FS5.1: Regulates the generator output to 12 and/or 9V.

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4.3. Physical SpecificationsThe following describes the main features of the M.E.G. device which are intended to meet the form and fit customer requirements:

PS1: Electrical output is wired into a standard outlet (9V and/or 12V) PS2: Components will be existing manufactured items whenever possible

PS2.1: Cooling fins made from aluminum and soldered onto main cylinder PS2.3: Cylinder will be made from cast iron pipe PS2.4: Pistons will be made from round steel stock, the displacer piston will be hollow

PS3: Device weight < 100lbs PS4: Justa stove built with cheap materials such as sand, dirt, vermiculite, and bricks.

Figure 18: Dimensioned Schematic of the M.E.G. Device, (all dimensions are in inches)

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4.4. Product QFDTable 3: QFD matrix for M.E.G. device

Design SpecificationsFunctional Physical

Customer Requirements and Constraints Power Transmitter

CR1: Produce 9-12V of electricity 5 4 2CR2: Electrical Safety 5 4CR3: Endure temperatures of 0°C to 40°C 4 4CR4: Easily transported to location 3 5CR5: No harmful exhaust 5 5CR6: Low impact on stove performance 3 2 4CR7: Low cost 4 2 4 3 4 4

3 3CR9: Reliability/Durability 4 5 3

Target Values 30% Stirling Justa 12V 100lb $150 Technical Difficulty 4 3 3 2 2 4 3 4

Priority (1-5)

Engine Thermal Efficiency

Use of a Simple Heat

EngineUse of a Common

Stove DesignRegulated DC Voltage

Minimized Weight

Minimized Size

Use of Pre-Made Components

CR8: Regular maintenance performed with basic tools

Increase 200-400 rpm to 1000-2000rpm

Fits into 4" x 4" x 2' box

Each of the listed customer requirements are directly correlated to a design specification. The most important specifications are the use of a Stirling engine with a high thermal efficiency. A closed cycle Stirling engine is easy to accomplish and has great benefits for the design. However, having a high thermal efficiency depends on having a regenerator which complicates the design and increases in volume of the device inside the stove.

Other important factors are the optimization of the heat engine size and the use of pre-made components. Size presents a trade-off between a high power output (from the swept volume), and low material costs. Also, larger engines generally run at slower rpms which requires a larger and more expensive generator. A balance between these two is essential in order to successfully meet all of the customer requirements. The use of pre-made components may also be difficult because the piston and cylinder require precise sizing.

4.5. Subsystems This project can be divided into two major categories: one that produces mechanical work and a second that converts it into electrical energy. The Stirling engine absorbs heat from the stove and produces mechanical work in the form of linear motion (a power piston moving up and down). The pistons are attached to a flywheel which converts the linear motion to rotational motion. A generator can use this to produce electrical energy by electromagnetic induction (spinning magnets to create electricity). The project can therefore be further deconstructed into the follow subsystems:

Mechanical Work: Stove/engine interface Stirling Engine:

o Pistons and cylindero Regeneratoro Flywheel linkage

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MENG 491W Fall 2008

Electrical Energy Conversion: Power transmitter DC generator Voltage regulator

4.5.1 Stove/Engine InterfaceOne of the most critical aspects of design is the interface between the stove and the heat engine. The Justa stove has a very high thermal efficiency because of a well designed combustion chamber and concentrated air flow. However, this means there is little space to incorporate a heat engine. To solve this problem the stove design will be adapted and the engine will be inserted from the side of the engine above the combustion chamber. This should not significantly affect the stove operation because the heat into the engine is approximately 500W which is small in comparison to the 4000 to 10000W of heat output from burning wood.

However, because the engine will obstruct air flow the shaft of the combustion chamber will need to be enlarged above the engine. The original combustion chamber is made from 5 inch tubes and has a cross

sectional area of 19.6in2 ( 52 π4

) for airflow. The diameter of the combustion chamber limits the size of

the Stirling engine cylinder to a maximum of about 4 inches in diameter. The easiest way to maintain the original cross section is to replace the tube above the engine with a 7in X 7in square box. 4.5.2 Stirling Engine

Pistons and CylinderThe piston and cylinder will be made from materials with dissimilar strengths to protect against dirt or other unwanted particles that may enter the system. If both were made of a strong material and a small rock got into the cylinder it would rattle and damage both the piston and cylinder until it was removed. However, if one material is a soft and the other hard the foreign particle would become imbedded in the soft material and cause less damage. Further information about pistons-cylinder interaction and design problems associated with it are discussed in Section 3.4.

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MENG 491W Fall 2008

Figure 18: Piston and Cylinder Detail Schematic

RegeneratorThe regenerator is a stack of wire mesh which acts as a heat exchanger. When the hot air is displaced to the cold section some of it flows through the regenerator tube and warms the wire mesh. When the cool air moves back down the regenerator is still warm and transfers heat to the air. This pre-warms the air for the hot section and cools the regenerator so that it can pre-cool the air for the next cycle. Sizing a regenerator requires delicate balance because the regenerator housing increases the dead space in the heat engine which decrease the compression ratio.

Flywheel LinkageThe flywheel linkage is complicated because the power and displacer piston are concentrically located in the cylinder. This constraint requires that the displacer shaft run through the center of the power piston and that the power piston is connected to the flywheel at an offset. The linkages are further limited by the attachment of the generator which requires that one side of the flywheel is unobstructed.

4.5.3 Power TransmitterThe Stirling engine’s frequency will range from 200-400rpm, which corresponds to a very large and expensive generator. Also, synching a directly connected generator and engine is very difficult. To avoid this cost and complication a power transmission belt will be attached around the flywheel and generator. Power is a function of torque and angular velocity and angular velocity inversely proportional to the object’s radius. A power transmission belt allows the generator to run at a higher rpm then the flywheel by decreasing the radius which increases angular velocity.

4.5.4 DC GeneratorThe generator will be purchased from a retailer and its function will not be modified. However, in order to successfully use a power transmission belt it is likely that an add-on will be necessary to change the radius.

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MENG 491W Fall 2008

4.5.5 Voltage RegulatorThe voltage regulator will also be purchased from a retailer and used as is. The main function of the regulator is to take the use the output from the generator and lower it to a stable 9 and or 12V output. Providing a stable output is critical because the M.E.G. device is intended to function as a power source for other electrical devices which isn’t feasible if the device only works intermittently.

4.6 Design Deliverables The following is a list of deliverables that will be available at the end of the first semester:

• Preliminary Design Report with associated modeling and analyses • Full set of engineering drawings • Bill of Materials• Cost estimates

5. Project Plan

5.1 ResearchThere are several concepts that must be investigated in order to complete the project design. Although the internet has been extremely helpful for researching appropriate technology and high efficiency stoves only the basics of Stirling engines are discussed. This is largely because the Stirling websites are for model versions or are commercial sources which do not cover topics such as: sizing, construction and power generation.

The relationship between swept volume, frequency (rpm), mean pressure and temperature difference is critical to determining the dimensions of the Stirling engine and in turn how much power it produces. Once these characteristics are known there are three commonly used methods of analysis to estimate the power output of a Stirling engine, namely the West, Schmidt, and Beale numbers. Also, knowledge of engine frequency is especially important because it affects the generator and voltage regulator selection.

5.2. Critical Function PrototypesThe M.E.G. device relies on several critical functions to be successful. This includes sections of the design process, difficulties with acquiring measurements, and critical input values of the system. These are significant for this project, especially because this process involves a new rendition of existing technology.

5.2.1. Critical Design FunctionsThe heat engine is a single cylinder beta Stirling engine. The power and displacement pistons move along the same cylinder and attach to the fly wheel. The pistons are connected to each other through the fly wheel by a four-bar mechanism. The four-bar also translates the linear motion of the pistons into rotational motion.

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MENG 491W Fall 2008

The difficultly of the piston-cylinder system is the manufacturing of the linkages so that they do not interfere with one another. A simple way to build a prototype for this system is to make a four-bar linkage system out of wooden stir-sticks. Pro/Engineer can also be utilized to scale the system properly.

Another critical design aspect is the interface between the Stirling engine and the Justa stove. This is especially difficult because the team has no experience with this kind of stoves. To solve this design problem, the Justa stove will be constructed and used to evaluate the connection it to the heat engine.

5.2.2. Critical ValuesThere are two critical output values throughout the entire system: the heat output of the stove and the power output of the engine. These values are related, the output of the stove determines the temperature of the engine and the power output of the engine is proportional to the temperature difference between the hot side and cold sides of the engine.

The Justa stove heat output can be estimated and will also be measured once the stove is built. The design is basic, and simple to assemble. The Stirling engine output can be estimated from the stove output and engine characteristics (swept volume, frequency, etc). The low temperature from the ambient air can be varied over a range of reasonable values to observe the effect on engine output.

5.2.3. Critical MeasurementsThe success of the project will be determined by the output of usable electrical energy. This can be found by taking measurements with a multimeter and voltmeter at the voltage regulator. The regulator is designed to lower the output voltage to a safe, usable level that can be constantly produced by the engine. If the engine cannot produce enough output the electricity will cut out intermittently.

5.3 DesignThe cylinder and pistons will need to be designed first because the rest of the M.E.G. device is largely dependent on their dimensions. The linkages and flywheel will be the next design. The power transmission, generator and voltage regulator are all dependent on the frequency of the engine.

5.3.1 Justa Stove/Heat Engine InterfaceThe design of the stove/engine interface depends largely on fluid dynamics (air flow through the stove) and heat transfer (from the stove to the hot section of the engine).

5.3.2 Pistons and CylinderPro/ Engineer will largely be used to visualize the movement of the pistons and observe part sizing. However, analysis must be performed first to determine engine dimensions and materials.

The engine design is directly related to the amount of heat energy input from the stove. This input will affect the cylinder dimensions. Important variables in calculating Stirling engine characteristics such as power output or mean pressure include the Beale number (Bn), the West number (Wn), and the Schmidt number (Sc):

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MENG 491W Fall 2008

Bn=W o

PVF

W n=Bn(T H+T k )(T H−T k )

Sc=∑|Q|pV sw

Variables in these equations are:

Power output from the engine (WO) Mean average gas pressure (P, p) Swept volume of the expansion space (V) Engine cycle frequency (F) Absolute temperature of the expansion space or heater (TH) Absolute temperature of the compression space or cooler (TK) Heat transferred to into the working fluid (Q) Volume swept by the piston (V sw)

The major design trade-offs in engine design are due to material costs. The cooling fins need to be made from a material with a high thermal conductivity. The ideal material for this is aluminum but the price is significantly higher than other metals. To balance these properties a small number of fins will be used but will be made of aluminum to maximize heat transfer.

The cylinder and piston also present unique challenges. A precise hole must be machined in the power piston for the displacement rod to be inserted. This hole must be drilled so that the displacement piston is on the same axis as the cylinder to prevent the displacement piston from hitting the inner walls of the cylinder.

The major safety concern of the cylinder is lubrication. Because of the high pressures in Stirling engines lubrication will result in explosion. It is critical that users understand the risks of lubrication the engine and never do so. The estimated design time for the pistons and cylinder is roughly two weeks.

5.3.3 Regenerator The regenerator design is based on heat transfer equations. The wire mesh inside the regenerator retains heat and pre-cools the hot fluid as the fluid is moving from the hot end to the cold end and vice versa. Although the regenerator increases the efficiency of the engine by increasing the temperature difference, it also adds cost, machining time, and complicates assembly. A final decision whether to include the regenerator or not will occur after much of the rest of the engine is design and its work output and thermal efficiency have been estimated. This subsystem will take approximately a week to design.

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MENG 491W Fall 2008

5.3.4 Linkage SystemThe linkage system to convert the linear power of the piston into the rotational power of the flywheel is essentially an application of the crank and slider from machine design. These linkages will be designed using principles and analysis from mechanics of materials because they will experience fatigue stresses from repeated loading. Programs such as Matlab and Pro/Mechanica will be used to create and solve equations to determine the proper material selection and dimensions of the links and bolts. Using a stronger material (higher yield strength) increases cost while a material with low yield stress lowers the factor of safety.

The challenges for the subsystem include proper flywheel design and the connection to the linkages. In theory there will be two crank and slider mechanisms working along the same plane and both will be using the flywheel as one of their links. The design should optimize rotational power. This subsystem should take roughly a week to design and build.

Figure 19: Linkage System Schematic

5.3.5 Transmission SystemAs previously discussed the transmission system requires a belt to increase the rpm of the flywheel in order to use a cheap generator. This is similar to gearing in a machine design application. Determining the ratio of the radii provides the multiplication factor (x) to determine the angular velocity of the small wheel. The design must have realistic values for the radii of the flywheel and generator wheel and a generator rpm that corresponds to reasonable 24V generators. The approximate time to complete this design is approximately two days.

x=rflywheel

rgenerator wheel

ωgenerator wheel=xωflywheel

5.3.6 Generator/ Voltage RegulatorThe generator and voltage regulator require little design time because they will be purchased. However, they are both dependent on the speed of the flywheel and the exact models may not be known until late in the design phase.

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MENG 491W Fall 2008

5.4. ConstructionThere are many intricate and interdependent systems in this design that must be carefully manufactured so that the product will have optimum efficiency. Construction and assembly will take place in Loma 6 unless more room is required.

Although the Justa stove is not a part of the product, it is a critical part of the design process and final testing. The stove will be assembled according to the instructions provided in Appendix A. Attachment of the Stirling heat engine to the stove will be clearer after the stove has been built. It is likely that the stove will need adaptations to properly interface with a Stirling engine.

The Stirling engine will be manufactured largely with a mill and lathe. The mill will be used to machine the links of the four-bar mechanism. The flywheel and pistons will be generated on the lathe. There are several possible ways to manufacture a cylinder, one of which is to cut tube stock to the correct length and attach ends to create a closed system. Other options would be to machine the cylinder out of a large piece of stock or to have the cylinder cast. However, large pieces of stock are expensive and it is unlikely that a foundry would cast a single piece.

The cooling fins will be one of the most difficult steps of the assembly and manufacture because they are closely spaced, thin pieces. One solution is to braze the fins onto the cylinder; another would be to machine the cylinder and fins as one piece.

The actual construction techniques used to build the M.E.G. device may change significantly as the design evolves. Ideally, the majority of the parts would be mass produced pieces from equipment found in developing countries (ie. using a standard sewer pipe as the cylinder). Integrating pre-existing parts will lower costs and decrease the difficulty of replacing or repairing parts.

The regenerator system is incorporated into the cylinder of the engine to increase the temperature difference and therefore increase the efficiency of the engine. The linkage system is attached to the pistons and the flywheel. This is the mechanism which converts the linear motion of our engine into the rotational motion needed by the generator. This is a complicated model where two crank and slider mechanisms will be working simultaneously on the same axis and flywheel. A belt will be attached to the flywheel and another wheel where we will amplify the RPM. This wheel will then be attached to a brushed DC generator which will create an electric current. This current will then pass through a voltage regulator in order to produce a constant voltage for the user.

The stove will need to be modified slightly in order for our engine to be inserted. Because the stove has been previously designed to produce the correct amount of heat, putting an engine inside will affect the air flow through the stove. Causing a “clog” in the stove will be overcome by increasing the cross sectional area where the stove is inserted in order to maintain proper air flow.

5.5 TestingTable 4: Overall System and Individual Subsystem Testing Procedures and Goals

Customer Requirements Testing Procedure

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MENG 491W Fall 2008

System CompatibilityBuild Justa Stove to spec, document any necessary alterations to connect to the M.E.G. device.

No Harmful Exhaust

Make sure the exhaust pipe of the stove is not affected by the connection to the heat engine.Check insertion point of heat engine for leaks.

Simple and Safe to Operate Measure temperature of exposed device surfaces to ensure T< 40°C (prevent burn injuries)

Reliability Run device for 8 hours without service

Produce a Minimum of 50W of Power

Run the M.E.G. device on the Justa stove/representative heat source and measure the voltage regulator output with a multimeter and a voltmeter.

Preserves Stove’s Cooking Performance

Compare the heat output of the stove with the heat input of the Stirling engine. Engine is acceptable if heat ¿ , engine < ¿20%out , stove.Compare time to boil a given volume of water for original stove design to the time to boil for the stove and M.E.G. device.

Low Noise Level Run device on representative heat source and measure noise output with a decibel meter.

5.6 Project DeliverablesAt the end of the final design project, the team will present the following:

1. Final Design Report including test results:At this point the team should be able to demonstrate a functional trial in which all the components work accordingly and produce the desired amount of electricity proposed. The final design report will include the results of all testing on the stove, heat engine, and electricity generation portion. Also, the report will include finalized design plans and recommendations for future improvements.

2. Prototype Meeting CRs:A full scale prototype M.E.G. device will be completed and functional at the end of the final design project.

3. Analysis of Any Failed Components:Failed components will be analyzed to determine the reason for failure and any necessary changes to the design.

4. User Instructions:Written instructions will be limited because of potential communication barriers with end users. Instructions will be visual (picture form) when possible.

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MENG 491W Fall 2008

5.7 ScheduleID Task Name Duration Start Finish Predecessors

1 Begin Team Proposals 18 days Tue 9/23/08 Thu 10/16/082 Proposal Sec 3 for Instructor Review 6 days Tue 9/23/08 Tue 9/30/083 Proposal Sec 3-5 for Instrcutor Review 5 days Wed 10/1/08 Tue 10/7/082

4 Proposal Sec 5-7 Final Review 3 days Tue 10/7/08 Thu 10/9/085 Complete Proposal 3 days Tue 10/14/08 Thu 10/16/084,1

6 Prepare for Proposal Presentation 3 days Fri 10/17/08 Tue 10/21/085

7 Begin and Finish Building Stove 3 daysWed 10/22/08 Fri 10/24/086

8 Test Stove Heat Output 3 days Mon 10/27/08Wed 10/29/087

9 Preliminary Design Review 44 days Tue 10/21/08 Fri 12/19/0810 Construction of Design Begins 47 days Tue 1/27/09 Wed 4/1/099

11 Prepare for Critical Design Review 31 days Fri 1/30/09 Fri 3/13/09

12 Design Engine Entrance Based onEngine and Stove Specs

6 days Tue 2/3/09 Tue 2/10/09

13 Begin Building Stirling Engine 24 days Wed 2/11/09 Mon 3/16/0912

14 Manufacture Individual PistonComponents

6 days Tue 2/10/09 Tue 2/17/09

15 Manufacture Cylinder 4 days Tue 2/17/09 Fri 2/20/0916 Manufature Flywheel 3 days Fri 2/20/09 Tue 2/24/0917 Assemble Engine 5 days Wed 2/25/09 Tue 3/3/0914,15,16

18 Test Stirling Engine (Power, QOUT) 5 days Wed 2/25/09 Tue 3/3/0919 Assemble total mechanism including

stove, engine and generator8 days Wed 3/4/09 Fri 3/13/097,17

20 Do Further Testing of Fully IncorporatedDevice

6 days Thu 4/2/09 Thu 4/9/0917,10

21 Make Necessary Changes to TotalDesign

6 days Fri 4/10/09 Fri 4/17/0920

22 Prepare for Final Design Review 36 days Thu 4/2/09 Thu 5/21/0910,19

9/21 9/28 10/5 10/12 10/19 10/26 11/2 11/9 11/16 11/23 11/30 12/7 12/14 12/21 12/28 1/4 1/11 1/18 1/25 2/1 2/8 2/15 2/22 3/1 3/8 3/15 3/22 3/29 4/5 4/12 4/19 4/26 5/3 5/10 5/17 5/24September October November December January February March April May

Figure 20: Gantt Chart Showing Project Schedule

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MENG 491W Fall 2008

5.8 BudgetTable 5: M.E.G. Project Budget

Just

a St

ove Stove Base Fire clay bricks $0.35 50 $0.00 $17.50

Combustion Chamber Refractory Cement $42.11 1 $0.00 $0.00Cold Rolled Steel Sheet 1/32" x 12" x 16" $12.20 1 $0.00 $12.20A36 Steel Plate 1/4" x 1' x 1' $27.86 1 $0.00 $27.86A36 Steel Plate 3/16" x 2" x 4" $85.86 1 $0.00 $85.86

Dolly Casters - Locking (5inch) $9.98 2 $0.72 $20.68 Casters - Regular (5inch) $13.96 2 $1.01 $28.93 Wood (Red Oak) 1'x4'x10' $19.83 1 $1.44 $21.27 Wood (Red Oak ) 1'x4'x6' $11.72 1 $0.85 $12.57

Stirli

ng E

ngin

e

Cooling Fins Aluminum 1' x 4' $33.08 1 $0.00 $33.08Regenerator Steel wire mesh 12" x 12" $3.18 1 $2.07 $5.25Displacer Piston Steel 3" OD x 0.125" Wall x 2.875" ID $20.92 1 $5.00 $25.92Power Piston Steel 3.75" diameter x 3" long $37.25 1 $0.00 $37.25Flywheel Brake disc 1/4" x 1' x 1' (approximate dimensions) $15.00 1 $0.00 $15.00Links Steel .12" x 1' x 2' $35.92 1 $31.93 $58.80Voltage Regulator 5A, 12V output $16.00 2 $2.36 $18.36DC Generator Item #10-1915 12/24V DC 1500/3000RPM $7.95 1 $2.00 $9.95Power Transmission Belts Serpentine Belt 6 groove; 1" width x 40" long $20.89 1 $0.00 $20.89 Cylinder Cast Iron 4" diameter Closet Elbow $30.00 1 $0.00 $30.00

Tota

ls

Research $168.98Justa Stove $260.39Stirling $254.50Total $683.88

Flywheel A36 Steel 3/16" x 1' x 1' $23.40 1 $0.00 $23.40Displacer Piston Aluminum 3.5" OD x .22" Wall x 3.068" ID, 6" long $10.62 1 $5.00 $15.62

LT1084CT-12#PBF-ND

5.9 PersonnelIn order to effectively build the M.E.G. device as a team the project has been divided into four major subsections, each with a corresponding set of unique responsibilities. Clearly defining individual tasks at an early stage will prevent confusion and aid concurrent engineering.

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MENG 491W Fall 2008

Figure 21: Organization chart for M.E.G. team

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MENG 491W Fall 2008

6. References

Alam, M. S., B. K. Bala, and A. M. Huo. "A Model for the Quality of Life as a Function of Electrical

Energy Consumption." Energy 16 (1991): 739-45. Global Energy Network Institute.

Www.geni.org.

Bradbook, Adrian J., and Judith G. Gardam. Placing Access to Energy Services within a Human

Rights Framework. Project Muse. Vers. 28. Human Rights Quarterly. 2006. Johns

Hopkins University. 20 Sept. 2008 <http://muse.jhu.edu/journals/hrq/>.

"Bio Energy Conversion Factors." Bio Feedstock Development Programs. ORNL.

<http://bioenergy.ornl.gov>.

Donohoe, MD, FACP, Martin. "Health Effects of Indoor Air Pollution from Biomass Cooking

Stoves." Medscape. 19 May 2008. 4 Oct. 2008 <http://www.medscape.com>.

"Exploring Appropriate Technology." Advanced Studies in Appropriate Technology. Aprovecho

Research Center. <http://www.aprovecho.org/index.html>.

"Investigation of Concepts for High Power Stirling Engines." Institut fur Kolbenmaschinen. 18

Sept. 2000. Universitat Karlsruhe. <www-ifkm.mach.uni-karlsruhe.de>.

"Technology Comparision: AC, DC & BLDC Motors." New Motion E-Newsletter. Feb. 2007.

Oriental Motors Corporation USA. <http://www.orientalmotors.com>.

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MENG 491W Fall 2008

Times, YK. "Image: Stirling Animation.gif." WikiMedia. 25 Feb. 2005.

<http://www.wikimedia.com>.

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MENG 491W Fall 2008

1349C Goshen St. Amanda Berlinsky 3473 Camino Valencia760-522-6205 760-752-9722berlinskya@gmail.com berlinskya@gmail.com

Objective: Seeking a permanent position as an entry level engineer in the field of Mechanical Engineering to utilize and strengthen my technical knowledge and gain hands on experience.

Education:University of San Diego, CA Expected May 2010

B.A./B.S. in Mechanical Engineering

Coursework & Lab experience:Graphics and Design, Materials Science, Static and Dynamic Systems, Solid Mechanics,Thermodynamics, Physics: Mechanics, Electricity and Magnetism, Optics, Programming andMATLAB, Manufacturing Processes, Fluid Mechanics, Heat Transfer; Lab Works: PhysicsMechanics, Circuit Design, Fluid Mechanics, Heat Transfer and Machine Design.

Experience:Military Leadership Academy Intern: Summers of 6/05 – 8/08 Freedom Alliance, Dulles, VA

Helped instruct and supervise approximately 45 cadets throughout the Academy. Taught leadership skills and how to apply them.

Technical Experience and Special Projects: NIFTY Project: Designed, fabricated/selected components, assembled, and tested NIFTY

project to complete a series of tasks to accomplish a simple goal.

Technical Skills: Tools/Test Equipments:

Lathe, Band Saw, Drill Press, Hand Drafting (in addition to CAD programs) Operating Systems:

Windows 95/98/XP/Vista Software:

Microsoft Excel/Word/PowerPoint, AutoCAD 2000/2002/2006, MATLAB

Personal Information: U.S. citizen Member of American Society of Mechanical Engineers, ASME (2004-present)

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MENG 491W Fall 2008

Logan K. JohnstonP.O. Box 1903

Mammoth Lakes, CA 93546(619) 889-9180

Logan.k.Johnston@gmail.com

Education: Bachelor of Arts/Science, Mechanical Engineering Mathematics and Theatre Arts minor. University of San Diego, 3.70 G.P.A., Expected December 2009.

Professional Experience: Tutor

TRiO Student Support Services, University of San DiegoSan Diego, CaliforniaOctober 2007 to Present

Tutor Engineering, Mathematics, Physics, and Theatre arts Participate in workshops

Assistant Supervisor Canyon Kids Ski School Rental Shop, Mammoth Mountain Ski AreaMammoth Lakes, CaliforniaDecember 2007 to January 2008

Measure and adjust ski equipment to proper fitting Manage and maintain rental shop area

Director of FinanceResidence Hall Association, University of San DiegoSan Diego, CaliforniaSeptember 2006 to May 2007

Manage and maintain budget Program events for students in residence halls

Equipment Adjuster (Part Time)Canyon Lodge Rental Shop, Mammoth Mountain Ski AreaMammoth Lakes, CaliforniaDecember 2005 to January 2007

Measure and adjust ski equipment to proper fitting Provide quality customer service

Volunteer Experiences:

President Sigma Phi Epsilon Secretary and Treasurer, Inter Fraternity Council Junior Marshal Sigma Phi Epsilon Ethics and Standards Board Umpire, Mono County Little League Life Guard, Walk on Water competition

Special Skills: Knowledge of Microsoft Office (Word, Excel, Outlook, PowerPoint),

Pro-E, Auto-Cad, CNC and manual machining, and C++ programming.

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MENG 491W Fall 2008

Lathe, mill, router, table saw, grinder, welding, band saw experience

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MENG 491W Fall 2008

Christina Callas826 Brighton Court

San Diego, CA 92109 (619) 300-5320

callas.christina@gmail.com________________________________________________________________________

EDUCATION

University of San Diego, San Diego, CA B.A./B.S. Mechanical Engineering Expected Fall 2009 Minor in Mathematics and Spanish Cumulative GPA: 3.89 2005 Trustee Scholarship Winner

ITESO, Guadalajara, Mexico Summers 2006 & 2007 Took classes in Spanish and lived with a host family 2007 Top Student Award Recipient in Psychology and Literature of Mexico

Relevant CourseworkThermodynamics Mechanics of MaterialsDynamics Fluid MechanicsMachine Shop Manufacturing ProcessesProE/AutoCad Machine DesignStatics Materials Science

WORK EXPERIENCE

Server/Housekeeper Summers 2005 - 2007Hearst Corporation – Wyntoon Estate McCloud, CA

Worked 40+ hours per week Set up for formal dinner parties, served meals at events ranging

from 30 - 100 patrons Performed housekeeping duties in guest rooms under strict deadlines

Server/Barista July 2001 - Feb 2003Laurie’s Mountain View Café Mount Shasta, CA

Performed opening and closing duties, counted daily till Worked independently to prepare food and serve customers

COMPUTER SKILLS

General: MS Word, PowerPoint, ExcelEngineering: ProE, AutoCAD

USD ACTIVITIES

2007 Bot Ball Competition March 2007 Constructed robot battle arenas for high school competition

2007 Walk on Water Competition April 2007 Assisted 7-12 year olds at competition involving the design of devices

for walking on water

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MENG 491W Fall 2008

7.2 Justa Stove ConstructionDue to file size and length constraints the full report on Justa Stove construction has been omitted. For a full version please visit: http://www.bioenergylists.org/stovesdoc/Still/AprovechoPlans/englishjustaplans.pdf

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