Photovoltaic System Design and Implementation

Project Plan

Senior Design DEC08-05

Client Dr. Dionysios Aliprantis

Faculty Advisors Dr. Dionysios Aliprantis Dr. Sumit Chaudhary Dr. Greg Smith

Team Members Scott Elliott Raja Umer Imtiaz Krysten Redinbaugh Molly Reida Robert Wells

REPORT DISCLAIMER NOTICE

This document was developed as a part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator.

May 5, 2008

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Table of Contents 1 Introductory Material ............................................................................................................................ 5

1.1 Problem Statement....................................................................................................................... 5

1.2 Potential Solution ........................................................................................................................ 5

1.3 Constraints................................................................................................................................... 5

1.4 Operating Environment ............................................................................................................... 5

1.4.1 Array ....................................................................................................................................... 5

1.4.2 Electronics............................................................................................................................... 6

2 Proposed Approach............................................................................................................................... 6

2.1 Concept Sketch............................................................................................................................ 6

2.2 System Block Diagram................................................................................................................ 7

2.3 System Description...................................................................................................................... 7

2.3.1 Solar Array .............................................................................................................................. 7

2.3.2 MPPT & Inverter..................................................................................................................... 7

2.3.3 LCD Display ........................................................................................................................... 7

2.3.4 Manual Disconnect.................................................................................................................. 7

2.3.5 Grid ......................................................................................................................................... 7

2.4 User Interface .............................................................................................................................. 7

2.4.1 Overview................................................................................................................................. 7

2.4.2 Real-time Data Plot ................................................................................................................. 8

2.4.3 Direct Communication Port .................................................................................................... 8

2.5 Requirements ............................................................................................................................... 8

2.5.1 Functional Requirements......................................................................................................... 8

2.5.2 Non Functional Requirements................................................................................................. 9

2.6 Market Survey ............................................................................................................................. 9

2.6.1 Power Electronics.................................................................................................................... 9

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2.6.2 Different types of Solar Cells................................................................................................ 10

2.6.3 Light Concentration .............................................................................................................. 10

2.6.4 Patents ................................................................................................................................... 10

3 Scheduling........................................................................................................................................... 11

3.1 Deliverables ............................................................................................................................... 11

3.2 Team Organization Structure..................................................................................................... 11

3.3 Task Hierarchy .......................................................................................................................... 12

3.3.1 Gantt Chart ............................................................................................................................ 12

3.3.2 Task Descriptions.................................................................................................................. 14

3.4 Work Breakdown....................................................................................................................... 20

3.4.1 Work Breakdown .................................................................................................................. 20

3.4.2 Resource Requirements......................................................................................................... 20

4 Closing Statements.............................................................................................................................. 21

4.1 Budgets ...................................................................................................................................... 21

4.1.1 Part Costs .............................................................................................................................. 21

4.1.2 Labor Estimates..................................................................................................................... 21

4.2 Estimate of Task Effort and Risks............................................................................................. 22

4.3 Plan Review............................................................................................................................... 23

4.4 Summary.................................................................................................................................... 24

5 Works Referenced............................................................................................................................... 25

Appendix A................................................................................................................................................. 26

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Index of Tables Table 1: Comparison of Solar Cells ............................................................................................................ 10

Table 2: Project Schedule ........................................................................................................................... 12

Table 3: Labor and Skills Time Estimate.................................................................................................... 20

Table 4: Estimate of Material Costs............................................................................................................ 21

Table 5: Estimate of Labor Costs................................................................................................................ 21

Table 6: Analysis of ROI ............................................................................................................................ 22

Index of Figures Figure 1: Concept Sketch.............................................................................................................................. 6

Figure 2 System Block Diagram................................................................................................................... 7

List of Definitions Crystalline Silicon Tetrahedrally bonded silicon atoms that form a crystal lattice structure Inverter A device for converting direct current into alternating current IV Curve Curve that shows a PV array’s voltage with respect to current Load The power consumed by a circuit. The electric power desired. Maximum Power Point Tracker (MPPT)

A high efficiency DC to DC converter which functions as an optimal electrical load for a solar panel or array.

Photovoltaic (PV) Technology that coverts solar radiation into electricity

Solar Array An array of photovoltaic modules or panels

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1 Introductory Material

1.1 Problem Statement

In recent years, alternative energy systems have become an area of intense focus. Iowa State University provides education to students to help meet society’s current needs, and has recently announced a commitment to make the campus a model of energy efficiency. However, the university currently does not have any solar energy installations. Iowa State has a related research facility located in the Applied Sciences Complex, but it is only designed for small scale fabrication of amorphous silicon and not for power generation. There is also a small wind turbine on campus, north of the Molecular Biology Building, but it is not a solar application. Solar energy is uniquely suited for peak load conditions because solar power is maximized in midday when energy needs are the greatest.

1.2 Potential Solution

We propose to design and implement a 100 to 700 W photovoltaic array to be installed on campus. The array will provide power to the grid, and will also include capabilities for data acquisition. The data acquisition sub-system will display a real-time plot of the power output that can be viewed by visitors and prospective students.

1.3 Constraints

The project shall satisfy the following constraints:

1. The funds officially available for EE 491/492 senior design projects are $150. Since this amount is insufficient, additional funding must be sought.

2. The array should be able to work in Iowa’s extreme weather.

3. Safety, governmental, industrial and environmental standards should be followed.

4. The student design team will not be allowed on the roof to install the system, or plan its location. Instead, a roof schematic will be used.

5. The deadline for completing the project is December 08.

1.4 Operating Environment

1.4.1 Array

Since the photovoltaic array will be mounted on the roof of a building on campus, it will be exposed to a variety of weather conditions. The power generated by the panels will depend upon the amount of sunlight striking the panels and the tilt angle of the array. To obtain maximum power output, the panels will face south and be angled at 42° from horizontal during the spring and fall seasons. During the summer, this angle will be decreased by 15°, and during the winter this angle will be increased by 15°. A mechanical system may be designed to vary tilt throughout the year.

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During the winter, snow accumulation on the array will be an issue. Using a sharper angle for the array during the winter will allow the snow to slide off, but the array must be capable of supporting the weight of the snow during and after a large winter storm.

Rain or melted water will also be quite useful. Rain water will help clean the solar panels by washing away dust particles and debris. Water melt will also reduce friction on the array surface, so the slippery surface will further aid the snow shedding process.

1.4.2 Electronics

The MPPT and inverter will be located indoors, and will therefore be subject to a controlled environment. However, if the array or the grid is hit by lightning, electrical surges could damage the electronics. Therefore, lightning and ESD protection must be included. The power electronics subsystem will also be responsible for ensuring that any input surges will not be propagated to the data port used by the display.

2 Proposed Approach

2.1 Concept Sketch

Figure 1: Concept Sketch

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2.2 System Block Diagram

Figure 2 System Block Diagram

2.3 System Description

2.3.1 Solar Array

Between 3-4 standard polycrystalline roof top panels will be connected together and will output DC current which will be fed to the MPPT and inverter

2.3.2 MPPT & Inverter

The MPPT will change the load to match the optimal power point of the array. This will allow the output power to be optimized. The power will be sent to the inverter which will convert DC to AC. This is necessary because the grid is AC.

2.3.3 LCD Display

An LCD display will be connected to the output for displaying the current system power output.

2.3.4 Manual Disconnect

This will allow a user to disconnect the array from the grid safely so that maintenance can be performed, or to protect the grid incase the array is malfunctioning. The manual disconnect is required per IEEE 1547-2003 [1].

2.3.5 Grid

The array’s output will be connected to the university’s power system and will generate AC power which will be added to the grid.

2.4 User Interface

2.4.1 Overview

The solar array and associated electronics will be entirely automated and capable of providing an optimal amount of power to the grid with no user intervention. To increase functionality, several features will be included that will provide users an opportunity to interact with the system.

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2.4.2 Real-time Data Plot

The photovoltaic system will include an attractive display to provide users with information about the array, the power it is currently producing, and solar energy in general. In particular, this display shall:

1. Provide a real-time plot of the daily and yearly power output of the array. This plot may also include data from the wind turbine.

2. Provide informative facts about solar energy 3. List and thank the sponsors of the project

The display system will receive real-time power data from the inverter using a direct communication port, which is described below.

2.4.3 Direct Communication Port

While the data plot will be informative only, users will be able to bypass the display and communicate directly with the inverter to issue one of several commands. The commands will allow a user to perform a full curve-trace of the array or to retrieve raw data on the operation of the inverter. This functionality is intended for collecting data that will be used in research.

2.5 Requirements

2.5.1 Functional Requirements FR001 The photovoltaic array shall output between 100 and 700 Watts of power.

FR002 The photovoltaic array shall have manual north-south tracking.

FR003 The mechanical tracking system will withstand temperatures between -40 C and 85 C.

FR004 If the mechanical tracking system cannot meet the temperature requirements, sensors shall be implemented that will prevent operation until conditions are favorable.

FR005 Mirrors may be used to increase the amount of light incident on the solar panels.

FR006 A MPPT (Maximum Power Point Tracker) shall be used to provide maximum power.

FR007 The output power provided by the photovoltaic array shall be fed back to the grid through a DC-AC inverter.

FR008 The inverter shall meet the safety and operational requirements of IEEE 1547-2003 [1].

FR009 The MPPT and inverter will have a combined efficiency of at least 90%.

FR010 The MPPT and inverter shall be rated to handle the maximum power output of the array.

FR011 An LCD screen will display a live feed of the power provided by the photovoltaic array.

FR012 The LCD display will show the IV curve of the photovoltaic array.

FR013 The LCD display will show a real-time image of the photovoltaic array.

FR014 The LCD display will provide general information about photovoltaic cells.

FR015 The LCD display may show money saved by the photovoltaic array.

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2.5.2 Non Functional Requirements NFR001 The photovoltaic array should be placed on the roof of Coover Hall.

NFR002 The photovoltaic array may be visible from ground level.

NFR003 The LCD display will be viewable in a public area in Coover.

2.6 Market Survey

2.6.1 Power Electronics

MPPT and DC-AC inverter technologies are not new, so many devices already exist that perform the same functions as the power electronics which will be developed for this system. In general, the competing products fall into one of two categories:

1. Grid-tie inverters. Similar to the inverter being developed in this project, these inverters perform maximum power point tracking and convert the power output to AC so that it can back-feed the grid.

2. Battery charge controllers. These products also perform MPPT, but use the power to charge a battery bank rather than back-feed the grid. Such charge controllers are designed for a battery bank of a specific voltage (usually a multiple of 12 V for a lead-acid bank) and contain intelligent circuitry to prevent overcharging the batteries.

The electronics developed for this project will differentiate themselves from the products currently available on the market in three ways:

1. Scale. Most solar inverters are capable of handling several kilowatts and cost over $2000. For example, the Fronius IG-5100 is rated for 5.1 kW and costs $3500 [2]. This project aims to build an inverter designed for 100 to 700 Watts for a fraction of the cost

2. Integrated curve tracer. No inverter currently on the market contains the ability to trace the entire I-V curve of the array. This feature will be unique to this project and will aid in research and education.

3. Integrated mechanical tracking controller. The inverter will also contain electronics needed to power motors for mechanical tracking of the sun. In all presently-available systems, the functionality is provided by a separate device.

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2.6.2 Different types of Solar Cells

Table 1: Comparison of Solar Cells

Type Efficiency $/Watt

Amorphous Si 1 ~4% $20-30

Polycrystalline Si 2 10-12% $5

Monocrystalline Si 3 20% $10

Triple Junction 4 28.5% (unavailable)

1 Based on PowerFilm Solar Products available through Flexible Solar Cells [3]

2 Based on polycrystalline panels available from Wholesale Solar [4]

3 Based on SunPower A-300 cells available through SunCat Solar, LLC. [5]

4 Based on Emcore ATJ cells [6]

This project will utilize polycrystalline panels, since they are both low cost and readily available.

2.6.3 Light Concentration

It is well known that mirrors and lenses can be used to increase the amount of light incident on a solar array, but this is rarely done for small-scale installations. This project will examine the feasibility of using mirrors or lenses and incorporate them if they are practical.

2.6.4 Patents

Several patents exist on similar systems. Some of the more recent patents dealing with solar cells, MPPTs, and inverters are listed below.

Patent 1 Siri. Solar array inverter with maximum power tracking. U.S. Patent 7,324,361, 2008.

Affect This patent does not affect us as it is for a bidirectional inverter which allows the array to work as a standalone generator. That feature is not part of the project requirements.

Patent 2 Dickerson; et al. Photovoltaic DC-to-AC power converter and control method. U.S. Patent 7,319,313, 2008.

Affect This patent does not affect us as it is designed to handle situations involving partial shading of solar arrays. Our system will be placed so as to avoid that situation and therefore the inverter will not have a similar circuit.

Patent 3 Chittibabu; et al. Photovoltaic cell. U.S. Patent 7,323,635, 2008.

Affect This patent does not affect us as the actual design of the cell’s being used are not part of this project. We are using commercially available cells.

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3 Scheduling

3.1 Deliverables

The team will provide the following at the completion of the project.

1. A working solar array, subject to available funds

2. A working MPPT tracker

3. A working inverter

4. A grid tie connection that meets the safety and power quality regulations of IEEE Std 1547-2003 [1].

5. Approval from Randy Larabee, Chief Electrical Engineer at ISU’s powerplant.

6. A complete user manual

3.2 Team Organization Structure

Rob WellsTeam Leader

Administration

Ryan CraggMechanical Engineering

Student

Scott Elliott

Umer Imtiaz

Molly Reida

Dr. Dionysios Aliprantis

Faculty Advisor

Krysten Redinbaugh

Communication Coordinator

MechanicalSoftware / FirmwareElectrical

Scott Elliott

Dr. Sumit Chaudhary

Faculty Advisor

Rob Wells

Molly Reida

Krysten Redinbaugh

Project Management

Dr. Greg SmithProgram

Coordinator

Rob Wells

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3.3 Task Hierarchy

3.3.1 Gantt Chart

Table 2 gives an overview of the project schedule. A complete Gantt chart is included in Appendix A.

Table 2: Project Schedule

Name Duration Start Date Finish Date

EE 491 111 days Tue 1/22/08 Sun 5/11/08

Managing Project 111 days Tue 1/22/08 Sun 5/11/08

Defining and Planning 32 days Tue 1/22/08 Fri 2/22/08

Identify Need 7 days Tue 1/22/08 Mon 1/28/08

Complete Project Definition 14 days Tue 1/22/08 Mon 2/4/08

Define Requirements 7 days Tue 2/5/08 Mon 2/11/08

Perform Market Research 14 days Tue 1/22/08 Mon 2/4/08

Map Project Schedule 11 days Tue 2/12/08 Fri 2/22/08

Determine Budget 11 days Tue 2/12/08 Fri 2/22/08

Fundraising 93 days Sat 2/9/08 Sun 5/11/08

Write Proposal 14 days Sat 2/9/08 Fri 2/22/08

Solicit Funds 79 days Sat 2/23/08 Sun 5/11/08

Documenting and Reporting 105 days Tue 1/22/08 Mon 5/5/08

Submit Weekly Status Reports 99 days Sat 1/26/08 Sat 5/3/08

Develop Draft Website 10 days Sat 2/23/08 Mon 3/3/08

Update Project Website 63 days Tue 3/4/08 Mon 5/5/08

Write Draft Project Plan 32 days Tue 1/22/08 Fri 2/22/08

Write Final Project Plan 10 days Sat 2/23/08 Mon 3/3/08

Designing 63 days Tue 3/4/08 Mon 5/5/08

Electrical 63 days Tue 3/4/08 Mon 5/5/08

Create Preliminary Design 21 days Tue 3/4/08 Mon 3/24/08

Detailed Design 42 days Tue 3/25/08 Mon 5/5/08

Perform Analysis 42 days Tue 3/25/08 Mon 5/5/08

Select Components 23 days Tue 3/25/08 Wed 4/16/08

Breadboard Circuits 23 days Tue 3/25/08 Wed 4/16/08

Draw Schematic 7 days Thu 4/17/08 Wed 4/23/08

Draw PCB 7 days Thu 4/24/08 Wed 4/30/08

Write Software 42 days Tue 3/25/08 Mon 5/5/08

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Finalize Drawings 5 days Thu 5/1/08 Mon 5/5/08

Mechanical 63 days Tue 3/4/08 Mon 5/5/08

Create Preliminary Design 21 days Tue 3/4/08 Mon 3/24/08

Detailed Design 42 days Tue 3/25/08 Mon 5/5/08

Perform Analysis 42 days Tue 3/25/08 Mon 5/5/08

Select Materials 23 days Tue 3/25/08 Wed 4/16/08

Draw Components andSchematics

14 days Thu 4/17/08 Wed 4/30/08

Finalize Drawings 5 days Thu 5/1/08 Mon 5/5/08

Create Draft Design andPresentation

21 days Tue 3/4/08 Mon 3/24/08

Prepare Draft Design Review 26 days Tue 3/25/08 Sat 4/19/08

Present Design Review 10 days Sun 4/20/08 Tue 4/29/08

Write Draft Design Report 14 days Tue 3/25/08 Mon 4/7/08

Write Final Design Report 28 days Tue 4/8/08 Mon 5/5/08

EE 492 118 days Mon 8/25/08 Sat 12/20/08

Managing Project 117 days Mon 8/25/08 Fri 12/19/08

Documenting and Reporting 117 days Mon 8/25/08 Fri 12/19/08

Submit Weekly Status Reports 117 days Mon 8/25/08 Fri 12/19/08

Update Project Website 117 days Mon 8/25/08 Fri 12/19/08

Design Project Poster 14 days Sat 11/8/08 Fri 11/21/08

Write Draft Final Report 14 days Tue 11/18/08 Mon 12/1/08

Write Final Report 14 days Tue 12/2/08 Mon 12/15/08

Prepare Final Presentation 14 days Tue 12/2/08 Mon 12/15/08

Designing 118 days Mon 8/25/08 Sat 12/20/08

Documenting 117 days Mon 8/25/08 Fri 12/19/08

Write User Manual 117 days Mon 8/25/08 Fri 12/19/08

Building Prototype 68 days Mon 8/25/08 Fri 10/31/08

Purchase Components 14 days Mon 8/25/08 Sun 9/7/08

Build PCB 54 days Mon 9/8/08 Fri 10/31/08

Fabricate Support Structure 68 days Mon 8/25/08 Fri 10/31/08

Testing 43 days Sat 11/1/08 Sat 12/13/08

Test and Debug Hardware 43 days Sat 11/1/08 Sat 12/13/08

Test and Debug Software 43 days Sat 11/1/08 Sat 12/13/08

Install Completed System 7 days Sun 12/14/08 Sat 12/20/08

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3.3.2 Task Descriptions

3.3.2.1 EE491

3.3.2.1.1 Project management

The team shall make sure that all deadlines are met and all deliverables are received at the end of the project. This shall be done by managing the project effectively with proper definition, preparation, design and fabrication

3.3.2.1.1.1 Task 1 – Definition and Planning

The team shall develop a project plan which shall serve as a binding agreement between the team and the client. The document shall ensure all requirements are completely understood by team members and client. The document shall ensure the expectations and deadlines of the project are met. The team shall discuss necessary tasks to complete the project along with their respective priorities.

3.3.2.1.1.1.1 Subtask 1a – Identify need

The team shall work with the client and advisors to determine the needs to be met by the project.

3.3.2.1.1.1.2 Subtask 1b – Complete project Definition

To define concrete boundaries for the project proposal, the team shall meet with advisors and as a group to determine the requirements that will best meet the demands of the client.

3.3.2.1.1.1.3 Subtask 1c –Define Requirements

The team shall work with the client to decide the requirements that shall be met by the end deliverables. The requirements shall be organized into functional and non functional requirements, and differentiation will be made between what will be done and extra goals.

3.3.2.1.1.1.4 Subtask 1d – Perform Market Research

The team shall research existing technologies and patents that exist so that they will be better prepared and will not encroach on anyone’s existing rights.

3.3.2.1.1.1.5 Subtask 1e- Map Project Schedule

The team shall map out a project schedule to make sure that all deadlines are met and all tasks are accomplished in a reasonable amount of time. The project schedule shall make sure that all members of the team are involved in all aspects of the project.

3.3.2.1.1.1.6 Subtask 1f- Determine budget

The team shall devise a budget which will reflect the financial needs of the project. The budget shall be fluid allowing for changes in design based on the client’s desires.

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3.3.2.1.1.2 Task 2- Fundraising

The team shall seek additional funding by soliciting the College and associated organizations.

3.3.2.1.1.2.1 Subtask 2a- Write Proposal

The team shall write a proposal which can be given to the parties who are being solicited.

3.3.2.1.1.2.2 Subtask 2b-Solicit funds

The team shall use the proposal to explain the need and will seek funds from organizations, the college and contacts the team members have in industry.

3.3.2.1.1.3 Task 3- Documentation and reporting

The team shall document all steps in the design process through weekly reports and the creation of a website and poster which shall display relevant information. Tasks 1 and 2 will be included, as shall a final project document which describes final project results.

3.3.2.1.1.3.1 Subtask 3a-Weekly Status reports

The team shall maintain contact with advisors and the course coordinator and advise them on the current project status. The team shall document project work each week, and report weekly via email on the current status and plans for the upcoming week. Major setbacks, meeting agendas, attendance, and accomplishments from the previous week shall all be reported, as shall individual accomplishments by group members. The time spent by each member shall be recorded and a semester tally shall be kept of all hours spent on the project by the team members.

3.3.2.1.1.3.2 Subtask 3b-Develop Draft Website

The team shall develop a website dedicated to the project. The website shall contain the project description and solution approach along with all the documentation associated with the project, as well as information on the team members.

3.3.2.1.1.3.3 Subtask 3c-Update Project Website

Throughout the course of EE491 the team shall update the website with the current version of their documentation and any other information desired.

3.3.2.1.1.3.4 Subtask 3d-Write Project Plan Draft

The team shall draft a plan which will lay out the course to be followed in the design phase of the project.

3.3.2.1.1.3.5 Subtask 3e-Write Final Project Plan

The plan shall be approved by the advisor, client and program coordinator, as well as each member of the team and shall serve as a binding agreement between the team and the client. All references shall be cited and the document shall be professionally bound with a copy going to Dr. Smith and the client.

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3.3.2.1.2 Design Development

The team shall follow all steps to create the design report. Work shall be approximately divided among all team members.

3.3.2.1.2.1 Task 1 Electrical

3.3.2.1.2.1.1 Subtask 1a- Preliminary Design

The team shall work with their advisors and shall develop an initial design which takes all functional requirements and non functional requirements into consideration. The team will work with other groups as needed.

3.3.2.1.2.1.2 Subtask 1b- Detailed Design

The team shall work on perfecting the initial design with good component choices. They shall work with their advisor and shall perform necessary calculations to prove the design will work.

3.3.2.1.2.1.3 Subtask 1c- Perform Analysis

The team shall simulate their design to assure that it works, and shall make sure that all part specifications are appropriate before ordering them.

3.3.2.1.2.1.4 Subtask 1d- Select Components

Appropriate components shall be selected for the project, keeping future system expansion in mind.

3.3.2.1.2.1.5 Subtask 1e-Breadboard Circuits

Once the components are received, the circuits will be created, first on breadboards, for ease of debugging. Any necessary changes will be made for the final circuit design.

3.3.2.1.2.1.6 Subtask 1f-Draw Schematic

A schematic of the circuit shall be drawn using either a CAD or Spice-based computer tool.

3.3.2.1.2.1.7 Subtask 1g-Draw PCB

A printed circuit board shall be designed using a computer tool and shall be ordered in preparation for building the prototype.

3.3.2.1.2.1.8 Subtask 1h-Write Software

The necessary software shall be planned and designed for the microcontroller and Windows programs needed to update the LCD display.

3.3.2.1.2.1.9 Subtask 1i-Finalize Drawings

All drawings shall be finalized and shall be submitted for approval to the advisory board and client before proceeding.

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3.3.2.1.2.2 Task 2 Mechanical

3.3.2.1.2.2.1 Subtask 2a-Preliminary Design

The team shall work with an outside mechanical engineering advisor to design the support structure for the solar array.

3.3.2.1.2.2.2 Subtask 2b-Detailed design

The design shall be perfected throughout the semester.

3.3.2.1.2.2.3 Subtask 2c-Perform analysis

Testing of the design shall be completed to make sure that all safety requirements are met and that the support structure shall hold the load, taking into consideration winter weather conditions in Iowa.

3.3.2.1.2.2.4 Subtask 2d-Select Materials

Appropriate materials shall be selected based on the load requirements and the cost of the material.

3.3.2.1.2.2.5 Subtask2e-Draw components and Schematics

All schematics shall be drawn so an outside contractor can build the system.

3.3.2.1.2.2.6 Subtask2f-Finalize Drawing

The final design shall be submitted to the advisory board and the client for approval before proceeding.

3.3.2.1.2.3 Task 3 Documentation

The team must meet with advisors to further discuss and decide on functionality and expected performance of the end product, in addition to implementation of the chosen technology. Through this process, the team shall gain a thorough understanding of what the end product needs to provide the user and shall be able to build a set of requirements. A complete document shall be written, which details the plan for product implementation.

3.3.2.1.2.3.1 Subtask 3a-Design Document Draft and Presentation

3.3.2.1.2.3.2 Subtask 3b-Prepare Draft Design Review

The team shall prepare to answer any questions the design review board has, to prove the feasibility of their design.

3.3.2.1.2.3.3 Subtask 3c-Present for Design Review

The team shall present the design to the Design Review Board, and shall show the feasibility of the project, the effectiveness of the design, and why certain design elements were chosen.

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3.3.2.1.2.3.4 Subtask 3d-Draft Design Report

The team shall draft a document recording the technical design specifications of the project. The document shall include mathematical reasons why certain points were included and shall include technical drawings of the system.

3.3.2.1.2.3.5 Subtask 3e- Final Design Report

The final design shall be approved by the design board, advisors and clients before proceeding.

3.3.2.2 EE492

3.3.2.2.1 Task 1Project Management

The team shall make sure that all deadlines are met and all deliverables are received at the end of the project by managing the project effectively with proper definition, preparation, design and fabrication.

3.3.2.2.1.1 Subtask 1a-Weekly Status Reports

The team shall maintain contact with advisors and the course coordinator and update them on current project status. The team shall document project work each week, and report weekly via email on current status and plans for the upcoming week. Major setbacks, meeting agendas, attendance, and accomplishments from the previous week shall all be reported as shall individual accomplishments by group members. The time spent by each member shall be recorded and a semester tally shall be kept of all hours spent on the project by the team members.

3.3.2.2.1.2 Subtask 1b-Update Website

Throughout the course of EE492 the team shall update the website with the current version of their documentation and any other information required.

3.3.2.2.1.3 Subtask 1c-Design Poster

The team shall create a poster for the project, highlighting the solution the team has developed. The team shall meet all poster guidelines laid out by the instructor. Using those guidelines, the team shall produce a poster that satisfies the course and client requirements.

3.3.2.2.1.4 Subtask 1d- Final Report Draft

3.3.2.2.1.5 Subtask 1e-Final Report

The team shall develop a final report document for the final results of the project. The team shall meet with advisors and as a group, to discuss and evaluate the success of the project with respect to the requirements. The final report shall discuss the success or failure of the project. Work shall be divided among team members approximately equally.

3.3.2.2.1.6 Subtask 1f-Final Presentation

The team shall report on the final results of their project, providing information on testing and final installation of the prototype. The team shall be evaluated to see if they met all goals and requirements.

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3.3.2.2.2 Task 2 Design

3.3.2.2.2.1 Subtask 2a-Write user manual

The team shall develop a user manual to accompany the completed prototype so that following groups or student may use it and not cause harm to themselves of the grid.

3.3.2.2.2.2 Subtask 2b-Purchase components

After testing, components shall be changed as needed, and final components shall be purchased for building the prototype unit to be installed.

3.3.2.2.2.3 Subtask 2c-Build PCB

The components shall be soldered onto the PCB designed in the previous 491 design section. The circuit shall be tested and changes will be made accordingly.

3.3.2.2.2.4 Subtask 2d-Fabricate Support Structure

The support mechanism for the solar array shall be built and tested, to be sure that it meets safety and other requirements, and then installed.

3.3.2.2.3 Task 3 Testing

Before delivery, the team shall build and thoroughly test a prototype of the hardware, while carefully documenting outcomes or failures. Expected and actual results will be compared.

3.3.2.2.3.1 Subtask 3a-Test and Debug Hardware

The hardware shall be thoroughly tested to make sure that it meets all safety and technical requirements. The hardware shall be tested with an outside power source before attaching the array, to prevent damage to the solar cells.

3.3.2.2.3.2 Subtask 3b-Test and Debug Software

The software shall be fully tested using various simulated contingencies to make sure that it functions as desired.

3.3.2.2.4 Task 4 Install Completed system

The team shall develop a working prototype to be used for testing and final implementation.

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3.4 Work Breakdown

3.4.1 Work Breakdown

Table 3: Labor and Skills Time Estimate

Documentation Software Design

Hardware Design

Build prototype

Test and Debug Total

Scott Elliott 45 25 75 5 50 200

Umer Imtiaz 45 100 5 50 200

Krysten Redinbaugh

45 100 5 50 200

Molly Reida 45 75 25 5 50 200

Rob Wells 45 50 50 5 50 200

Total 225 150 350 25 250 1000

3.4.2 Resource Requirements

3.4.2.1 Physical requirements

1. Lab space

2. CAD tools for schematic capture and PCB design

3. Microcontroller development tools (compiler and programmer)

3.4.2.2 Advisory Consultants

1. Jason Boyd: Coover Lab Manager

2. Dr. Dionysios Alliprantis: Faculty Advisor

3. Dr. Sumit Chaudhary: Faculty Advisor

4. Ryan Cragg: Mechanical Engineering student

5. Dr. Greg Smith Senior Design Program Coordinator

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4 Closing Statements

4.1 Budgets

In consideration of the tasks and objectives defined for this project, the following budgets have been prepared.

4.1.1 Part Costs

Table 4 provides an estimate of the cost of materials and subcontracted labor required to complete this project. Since each senior design team is allocated a budget of only $150, additional funding must be secured.

Table 4: Estimate of Material Costs

Material Cost

Solar Panels (500 W @ $6/W) $3000

Mounting Structure $500

Installation Labor $500

Power Electronics (development and parts) $750

Installation Supplies (wire, manual disconnect, circuit breaker) $500

Posters and Documents $50

LCD Display $600

Total $5900

4.1.2 Labor Estimates

Table 5 gives an estimate of the student labor required to complete this project. Although, student labor shall be donated, the numbers provide a useful reference for budgeting future projects.

Table 5: Estimate of Labor Costs

Person Hourly Rate Hours Total

Scott Elliott $10 200 $2000

Umer Imtiaz $10 200 $2000

Krysten Redinbaugh $10 200 $2000

Molly Reida $10 200 $2000

Rob Wells $10 200 $2000

Total 1000 $10,000

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4.2 Estimate of Task Effort and Risks

Table 6 shows the value of the energy produced by the solar array over its expected 20 year life.

Table 6: Analysis of ROI

Parameter Value Incident Solar Energy in Ames, Daily 1 5.0 kWh/m2/day Array Output, Annually 2 910 kWh Value of Energy

Annually 3 $64 Over Next 5 Years 4 $290 Over Next 10 Years 4 $550 Over Next 20 Years 4 $950

1 Data from National Renewable Energy Labs <www.nrel.gov> [7] 2 Assuming 5 m2 of 10% efficient cells 3 Assuming 7¢ per kWh 4 Adjusted to present-day value assuming 3% inflation

Per the calculations above, the system will not pay for itself through the energy it produces alone. It is important to note, though, that the price of electricity will likely rise substantially in the coming years, making this installation more profitable. Also, the cost of electricity was based on the ISU coal-fired power plant, since that is the current source of power for campus. However, solar energy is best suited to meet peak demand, which in many cases is provided by gas turbines that have an operating cost of nearly 20¢ per kWh. If the calculations are repeated using this price, the array will generate over $2500 during its lifetime.

Though the system will not make money, it will provide Iowa State many other benefits. In addition to the monetary value of the generated electricity, Iowa State University will receive the following benefits.

• Symbol of Energy Efficiency. In support of President Geoffroy’s program to establish Iowa State University as a model of energy efficiency, the ISU Solar Initiative will serve as a demonstration of ISU’s commitment to renewable energy. The array will illustrate the University’s concern for climate change and dependence on foreign oil. In addition, designs developed for this project can be extended to other efforts such as the Solar Decathlon. Finally, the University will directly benefit from the free electricity produced by the array.

• Recruitment. The solar array’s output will be plotted in real-time on an attractive display prominently positioned in Coover Hall. The display will serve to establish Iowa State University’s status as an energy-conscientious institution to current and prospective students. Further, since the array, electronics, and display were designed and implemented by a student-run team, they will reinforce the reputation of the College of Engineering as a premier school of science and technology.

• Education. The ISU Solar Initiative provides students with a substantial engineering project to plan, manage, and implement. Such experiences make ISU graduates more competitive in the job market and more successful in demanding engineering positions. As a result, employers will be more likely to seek ISU graduates and further grow the reputation of the University.

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• Research. Upon completion of this project, the University will have a fully functional solar array and fully customizable power electronics. These facilities will prove useful for research in the areas of renewable energy and power conversion.

• CO2 emission reduction. The college will avoid nearly thirty metric tons of CO2 emissions over the twenty year lifetime of the solar array [8].

4.3 Plan Review

To ensure that work on this project plan was proceeding as intended, an early draft of the plan was submitted to the advisors, client, and program coordinator. Dr. Aliprantis, the client and faculty advisor for the project, was satisfied with the scope of the proposed effort. Dr. Smith, the program coordinator, offered several suggestions on grammar, syntax, and articulation, and recommended the following significant content changes:

• Include mention of the small wind turbine north of the Molecular Biology Building. Mention of the wind turbine has been included in the problem statement of the plan. Since it is not a photovoltaic installation, it does not directly affect the project.

• Add details and numerical values to the description of the operating environment. At this time, only the angle at which the array should point is known and has been included in this section. Additional specifications such as wind speeds, snow weight, and temperatures will be carefully considered as design progresses. However, since the panels are designed for roof-mount installation, they already meet all applicable requirements; all that is needed is to ensure that the mounting structure is equally robust.

• Clarify connection to the grid versus an isolated load. The photovoltaic array will be connected to the grid, as stated in the system description. This is in contrast to the wind turbine project, which currently intends to power an isolated load and use the grid as a back-up power source.

• Add details about the communication port. The draft project plan mentions only that there is a communication port on the inverter, but does not mention its functionality or intended purpose. These details have been added to the description of the user interface.

• Include specific makes and models of the competing products mentioned in the market survey. Many companies make a broad range of products that are similar to (but slightly different than) the tracker and inverter proposed for this project. Some manufacturers and part numbers were added to the market survey section where this topic is discussed.

• Add discussion about the patents relating to this project. Patents exist for several products similar to the inverter being developed for this project. These patents are mentioned in the project plan, but it was not stated whether they directly affect this project. Details were adding explaining why the patents are for products and systems different than the one being proposed.

• Correct titles in the organizational chart. Several titles in the organization chart have been altered to be consistent with official university titles.

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• Reconsider the cost of the mounting structure and installation labor. Dr. Smith believed that the estimated cost of the mounting structure and the labor to install the array were low. After discussion with Ryan Cragg, the estimates were revised.

• Justify the project despite the monetary loss. Due to the low price of electricity in Ames, the proposed solar array will never recover its cost in electricity alone. To justify the project, it is therefore necessary to explain why the array will not pay for itself, and to mention other benefits that make the project a good investment. A discussion of these topics was added to the Estimate of Task Effort and Risks.

4.4 Summary

In summary, ISU currently has no solar arrays that provide electricity to the campus. Since this is inconsistent with the University’s status as a premier school of science and technology and its commitment to energy efficiency, one solution is to put a solar array on campus that will feed its output to the grid. The power generation of the array will be plotted on a real-time display, to provide educational value and information to current and prospective students.

Given the background of the student members and the expertise of the faculty advisors, this project is feasible in the two semesters allotted. Since the project offers several unique benefits to Iowa State University, it is recommended that it be pursued.

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5 Works Referenced [1] IEEE Std 1547-2003, IEEE Standard for Interconnecting Distributed Resources with Electric Power

Systems.

[2] Whole Solar Products: Inverters. Fronius IG-5100 <http://www.wholesalesolar.com>

[3] PowerFilm Solar Products <http://www.powerfilmsolar.com> through Flexible Solar Cells <http://www.flexsolarcells.com>

[4] Wholesale Solar Products: Polycrystaline panels. <http://www.wholesalesolar.com>

[5] SunPower Prodcuts: Monocrystaline panels A-300. <http.sunpowercorp.com> through Suncat Solar LLC.

[6] Emcore Products: Multijunction ATJ cells. <http://www.emcore.com>

[7] National Renewable Energy Labs Average Solar Energy Available in the Nation <http://www.nrel.gov>

[8] Environmental Protection Agency: Clean Energy. Calculations and References <http://www.epa.gov/solar/energy-resources/refs.html>

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Appendix A Gantt Charts