Solar oven report

University of Arizona Tucson, AZ, 85716

S.A.C.R.A.W Solar Oven Prepared for: Dr. Stanley Pau

Jack Speelman Rebecca Nelson Paola “Andy” Lopez Lorin Greenwood Stephanie Gilboy October 21st 2012

Figure 1: Shows the team members of Team S.A.C.R.A.W standing alongside the final solar oven on Solar Oven Testing Day.

Team S.A.C.R.A.W Solar Oven 2

Table of Contents

Cover 1 Table of Contents 2 Executive Summary 3 Introduction - Motivation/Background/Key Terms 4-5 - Criteria and Constraints 5-6 Main Body - Functional and Design Requirements 6-7 - Design Theory and System Model 7-10 - Design Description – Conceptual Design 11-13 - Design Description – Final Design 14-17 - Design Justification 17-18 - Evaluation of Results 18-19 - Test Procedure 19-20 Design Critique and Summary 20-22 Appendix - First Oven Spreadsheet Data and Design/Drawing 22-24 - Final Oven Spreadsheet Data and Design/Drawing 25-27 - References 28

Team S.A.C.R.A.W Solar Oven 3

Executive Summary

The objective of the solar oven project was to design, build, and test a productive solar oven that

could reach an interior temperature of 100˚C. This was obtained through converting solar energy,

also known as electromagnetic energy, into thermal energy. The first law of thermodynamics

was utilized by understanding that energy cannot be created or destroyed but could be

transformed and used to heat the interior of the oven.

Two solar ovens were constructed in order to fully maximize the temperature inside the oven

chamber. The first oven was used as a prototype and research tool in order to build an oven that

could reach the optimum temperature calculated. The initial oven was predicted at 170.26˚C but

only reached an interior temperature of 85.6˚C. This produced a preforming index number of

1.02 and a cost index of 6.05˚C/dollar. The improved oven had a predicted temperature of

176.58˚C using the ambient air temperature and solar density provided. The oven reached an

interior temperature of 99.6˚C. The performing index for the second oven was calculated to be

1.28 and a cost index of 4.34˚C/dollar.

Team S.A.C.R.A.W Solar Oven 4

Introduction

Motivation:

• Learn the concept of team work and how to work together with other people to

achieve a common goal

• Gain proficiency in Excel, Solid Works, and basic solar oven knowledge.

• Acquire knowledge of the transformation of solar energy to heat.

• Learn the basics of the design and construction process

Background:

The main goal of the solar oven project was to find out the best way to change solar

energy into thermal energy. To do this, teams needed to know the first law of thermodynamics.

The first law states that energy cannot be created or destroyed, but can be changed from one

form to another. In the Solar Oven Theory, the energy that is put into the oven should equal the

energy that comes out (Ein=Eout). Therefore, the solar energy in joules should equal the thermal

energy in joules. The oven does this by taking the energy from the sunlight and transferring it

into heat. Since the energy in equals the energy out it allows the equation stated above to be

true. Knowing that the power is equal allows Team S.A.C.R.A.W. to find the temperature of the

oven chamber.

Mathematics for the Solar Oven with Key Terms:

Predicted Temperature:

Team S.A.C.R.A.W Solar Oven 5

€

Tio = Tambient + IoAw ⋅ G⋅ τ

n ⋅ a Usb ⋅ Asb +Uw ⋅ Aw( )

Variables:

Tio =the temperature inside the cooking chamber

Tambient= the outdoor temperature on the day tested

G= the gain from the reflectors

Uw= the heat transfer coefficient of the window

Aw= the area of the window

Usb= the heat transfer coefficient of the sides and bottom of the cooking chamber

Asb= the total area of the sides and bottom of the cooking chamber

Constants:

a= absorption coefficient of the cavity walls

τ= the optical transmission coefficient of the cavity walls

Io= the incident solar power density

Performing Index:

Variables: