solar oven

Design Team and Project Logistics

You will conduct this project in teams of 3-4 students. If you are co-enrolled in ME495, you should use the same project team for both classes. If you are not enrolled in ME495, you may form a group with other non-ME495 students, or you will be placed onto a team of non-ME495 students.

Design Requirements

Note that some of these requirements leave some flexibility in how they are interpreted. Feel free to propose ideas you have that might bend the rules to Dr. Nelson, who may or may not allow your idea. You should obtain approval in writing from Dr. Nelson if you are bending a rule.

· The complete heating system must be able to fit within a 27 cubic foot space, with a maximum linear dimension of 5 ft. The weight of the oven should allow it to be manually handled (i.e. moved around a house) by only one person without assistance.

· Projects may not be left on campus overnight (this may impose an additional size/weight restriction)

· Design must cost less than $30 (see bill of materials description under project report)

· No electrical or exothermic chemical heating

· No use of any lenses or concentrators (such as satellite dishes or Fresnel lenses) unless you make them yourself

· Must be able to produce a fully-cooked, safely edible, baked good within 50 minutes (see demonstration details) that has a minimum dimension of 1” and has a total volume of at least 30 in3. Note that:

· Automatically acceptable baked goods include brownies, breads and cakes. Additional goods will be considered, but must be approved by Dr. Nelson.

· To be “fully-cooked”, no liquid dough/batter may remain and any internal ingredients must be cooked after beginning in an uncooked state.

· Everything that the food touches must be safe for human consumption.

· Your design may utilize moving parts, but you must move them manually (i.e. no electrical actuation)

Analysis Requirements (ME450)

In order to demonstrate and apply your heat transfer knowledge, you will be required to describe and estimate some thermal parameters for your design (see project report requirements below).

Timeline of Deliverables

See “Deliverables” section for full information about each deliverable

· 2/21/17: Memo 1 Due in Class

· 3/28/17: Memo 2 Due in Class

· 4/10/17: Final Device Construction Deadline

· Email a picture of your completed project to Dr. Nelson by the end of the day

· 4/18/17: ME450 Project Report Due

· 4/18/17 (if sunny): Project Demonstration Day

Demonstration Details

ME 450 Demonstration Details (4/18/17 – if sunny)

· If not sunny, demo will occur on next sunny lecture day

· Demonstrations will be in the grass bowl to the north of the engineering building

· You may leave your ovens outside in the sun to heat up all day, but the oven must be at the demonstration site by 3:30pm

· 3:30-4:00 Design reviews, hang out, prepare baked goods

· 4:00 Place baked good in oven

· 4:50-5:15 eat baked goods!

Deliverables

Preliminary Memos. ALL MEMOS MUST INCLUDE YOUR ASSIGNED TEAM #

· Design Project Memo 1. Include the following:

· 2 page maximum

· At least 3 different design ideas you considered for your project, including schematics/diagrams . NOTE: you must have 3 DIFFERENT designs – not combinations of each other

· A finalized physical design for your project, including:

· Explanation of why you chose your selected design over the other options

· Description of your absorber surface

· Description of your insulation approach

· Identification of materials/items to be used in your design

· Listing of where/how you will obtain the materials in your design

· Design Project Memo 2 (Note that you should discuss your memo 2 with Dr. Nelson before submitting the final reports). Include the following:

· A sketch/schematic of your design

· A list of the key heat transfer paths from your absorber to the ambient

· A thermal resistance network for each of the heat transfer paths, identifying what EACH thermal resistor represents (equations not necessary)

· An estimate of the rate at which solar energy is absorbed in your design

ME450 Project Report

The project report will be due on the originally scheduled demonstration date regardless of weather. If a lack of sunny conditions causes the demonstration to be postponed, the report will still be due!

The project report should be brief and concise , containing the sections described below:

· Cover Sheet: Grade Sheet (see appendix)

· Section 1: Design Description (<2/3 page)

· Describe your design, including a SCHEMATIC, a PHOTOGRAPH, and a description of materials/items used

· Describe why you chose your design

· Section 2: Analysis ( only as much length as is necessary to clearly communicate your analysis). Note that scanning handwritten resistance networks may be faster/easier than creating digital figures.

· Estimate the rate in Watts at which sunlight is absorbed by your design (assume a solar flux of 1000 W/m2)

· Show a thermal resistance network for each heat transfer path for the heat loss from your design. Calculate/estimate all thermal resistances. For all convection correlations, list the assumed geometry, the equation being used, and the calculated ‘h’ value.

· Identify the dominant mode of heat loss, and discuss why this is the case.

· STATE AND JUSTIFY all assumptions and estimates in the analysis. And by “justify” I mean “PROVE to me that your assumption is reasonable”

· Section 3: Reflection (<1/2 page)

· Suggest TWO design modifications that would significantly reduce the heat loss from your design. One modification must be a low-cost modification that would fit within your project budget, and the other modification must be a modification using commercially available materials/technologies that would be realistically used in industry (i.e. without an absurd cost constraint). Note that you will have to perform some independent research on available materials and technologies to complete this.

· Section 4: Bill of Materials

· List ALL materials in the design (automatic 20% grade reduction for any material I find in your design that is unaccounted for in your bill of materials)

· Can treat scavenged items as zero cost only if anyone could reasonably attain them freely (for donated items you must count the full purchase cost)

· For structural materials, you must use the minimum UNIT COST, not a portion cost (i.e. if you buy an item in its smallest available quantity and only use 10% of the item, you still must include the TOTAL item cost)

· For fastening/assembly/filler materials, you may use portion costs (e.g. glue, nails, screws, etc). If in doubt, ask me.

· You must include the cost of any specialty tools required for your assembly that are not available in the machine shop (even if they are your own)

Grading

· 10 pts: Memos 1&2

· 70 pts: Report

· 5 pts: Design Description

· 55 pts: Appropriate and correct thermal analysis

· 10 pts: estimate of solar absorption

· 25 pts: correct thermal resistance network for heat loss paths

· 15 pts: calculations and estimates of thermal resistances

· 5 pts: discussion of dominant mode of heat loss

· 10 pts: Reflection

· 20 pts: Heater performance

· 20 pts if baked good fully cooked

· 10 pts if baked good partially cooked

· 5 pts if baked good is warm

· Bonuses

· +2 pt for creative dishes

· +2 pt for tastiness/cooking quality

· +5 pt (max) for innovative designs

· Penalties

· -5 pts/ dollar over $30

· -30pts (max) for poor grammar, spelling, formatting, and writing clarity

· Peer Evaluation: your project grade will be scaled by a peer evaluation from your teammates, who will rate your contributions to the group. See the peer evaluation document for additional details. Your project grade will equal (team project grade)*(peer evaluation score).

Appendix

This appendix contains four items:

· A cover sheet for your ME450 report, which must be included as the top page

· A peer evaluation form that should be emailed to Dr. Nelson ONLY if you want to give yourself and your teammates something other than 1.0 (if giving your teammates all 1.0, you need not do anything). If you wish to give a teammate a score below 0.9, you can only do so if you have consulted with Dr. Nelson beforehand in attempts to resolve the issue.

· A list of useful tips and radiation Basics

ME 450 Cover Sheet

Team # _____

Team Members

[insert names here]

Memos _________/10

Design Description _________/5

Solar Absorption _________/10

Resistance Networks _________/20

Resistance Calculations _________/20

Dominant Mode Discussion_________/10

Reflection_________/10

Heater Performance _________/20

Grammar/clarity grade scaler _________/100%

Bonuses _________

Penalties _________

TOTAL _________

Peer Evaluation

Assign a score for yourself and each group member in ME450 between 0 and 1.05. A score of 1.0 corresponds to fulfilling the required responsibilities for the project. If you are not assigning any scores other than 1.0, you do not need to turn in this form. If you assign a score other than 1.0, you must email the form to Dr. Nelson and justify the score in the comments. If you do not justify your scores (other than 1.0) or give yourself a blatantly dishonest score (i.e. above 1.0 when all teammates rate you below 1.0) I may decrease your own score. The peer evaluation scores will scale the individual project grades. Your score should consider the individual’s contributions, level of effort, ease of working with, and reliability. In order to give a score lower than 0.9, you must communicate with me beforehand and demonstrate efforts to resolve the problem. You may not give everyone on the team a score above 1.0.

SCORE

Your name ___________________________________ _______

Comments __________________________________________________________________________________ __________________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________________________________________

Teammate 1 __________________________________ _______

Comments __________________________________________________________________________________ __________________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________________________________________

Teammate 2 __________________________________ _______

Comments __________________________________________________________________________________ __________________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________________________________________

Teammate 3 __________________________________ _______

Comments __________________________________________________________________________________ __________________________________________________________________________________________________________________________________________________________________________________________

_____________________________________________________________________________________________

Tips & Radiation Basics – Important Things to Understand

· DO NOT PUT OFF TESTING UNTIL THE VERY END. Weather is unpredictable, and a lack of sunny days during the week before the demonstration date is not an acceptable excuse.

· Radiation (such as sunlight) does not provide heat UNTIL it is absorbed somewhere

· Black/dark objects generally absorb radiation (and also emit/give off the most radiation)

· Shiny objects reflect radiation (i.e. they redirect it somewhere else)

· Transparent objects let radiation go through without interacting with it (i.e. they do not absorb the radiation)

· No object is a perfect absorber/reflector/transmitter of radiation. The percentage of radiation that a material absorbs/reflects/transmits is the absorptivity()/reflectivity()/transmissivity(), respectively.

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