Photovoltaic Stand-Alone Systems

244 Pages·2010·6.3 MB·English

DOE/NASA/01 95-1
NASA CR-1 65352
M206
Photovoltaic Stand-Alone Systems
Preliminary Engineering Design Handbook
H. L. Macomber and John B. Ruzek

Monegon, Ltd.

Gaithersburg, Maryland

Frederick A. Costello
F.A. Costello, Inc.

Herndon, Virginia

and
Staff of Bird Engineering
Research Associates, Inc.
Vienna, Virginia
August 1981
Prepared for
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
Under Contract DEN 3-195
for
U.S. DEPARTMENT OF ENERGY
Conservation and Renewable Energy
Division of Solar Thermal Energy Systems
Washington, D.C. 20545
Under Interagency Agreement DE-AI01-79ET20485
ACKNOWLEDGEMENT

This handbook was prepared by MONEGON, LTD., of Gaithersburg,
Maryland under Contract DEN3-195 with the National Aeronautics and Space
Administration, Lewis Research Center. John B. Ruzek served as Project Engineer
with management support by Dr. Harold L. Macomber. Valuable assistance was
provided by two subcontractors, Frederick A. Costello, Inc., Consulting Engineers,
and Bird Engineering-Research Associates, Inc.
NOTE: Throughout this handbook, reference is made to Loss of Load Probability
(LOLP) estimation procedures. According to the 1970 National Power Survey of
the Federal Power Commission, these estimating procedures may be more
correctly defined as Loss of Energy Probability (LOEP) procedures. This
definitional difference in no way affects the accuracy or usefulness of these
procedures.
/
CONTENTS
Section Title Page
1 INTRODUCTION 1-1
2 GUIDE TO HANDBOOK USAGE 2-1

3 TYPICAL STAND-ALONE PHOTOVOLTAIC

SYSTEM CONFIGURATIONS
3-1
4
COMPONENT DESIGN AND ENGINEERING INFORMATION 4-1
4.1 Electrical Loads 4-1
4.1.1 Estimating the Load 4-1

4.1.2 Load Reduction Strategies 4-4

4.1.3 Merits and Disadvantages of Both

Ac and Dc Power 4-5

4.2 Photovoltaic Arrays 4-7

4.2.1 Photovoltaic Terminology 4-7

4.2.2 Ideal Solar-Cell Current-Voltage

Characteristics 4-12

4.2.3 Current-Voltage Characteristics of

Arrays in the Field 4-21

4.2.4 Available Modules 4-24

4.3 Lead-Acid Storage Batteries 4-27

4.3.1 Advantages and Disadvantages of

Batteries in Photovoltaic Systems 4-27

4.3.2 Battery Operation 4-28

4.3.3 Battery Current/Voltage Characteristics 4-28

4.3.4 Battery-System Design 4-32

4.3.5 Battery Life 4-33

4.3.6 Lead-Acid Storage Battery Safety 4-36

4.4 Power Handling 4-40

4.4.1 Dc Power Conditioning 4-40

4.4.2 Control Schemes 4-43
4.4.3 Electrical Wiring 4-46

4.5 Emergency Backup Systems 4-51

4.5.1 Load Analysis 4-51

4.5.2 Basic PVPS Design Margin 4-52

4.5.3 Types and Suitability of Backup Systems 4-53

4.5.4 Incorporation of Backup Into the PV

System 4-56

iii
CONTENTS (Continued)
Section Title Page
5 INFORMATION NEEDED TO START THE
DESIGN PROCESS 5-1
6 PRELIMINARY SYSTEM DESIGN CONSIDERATIONS 6-1

6.1 Insolation and Siting 6-1
6.2 Operation of PV Systems Under Varying Loads 6-7

6.2.1 Array and Battery Quick-Sizing Method 6-7

6.2.2 Component Sizing 6-9

6.3 Basic Approach to Feasibility Assessment

of Photovoltaic Power Systems 6-13

6.3.1 Preliminary Estimate 6-13

6.3.2 Life Cycle Cost Determination 6-15

6.4 Reliability Engineering Approach 6-18
6.4.1 Definition and Specification of PV

System R & M Requirements 6-18

6.4.2
R & M Networks and Block Diagrams 6-24
6.4.3 Reliability Prediction and Feasibility
Requirements 6-29
6.4.4 Failure Mode and Effects Analysis 6-30

6.5 Advantages and Disadvantages of PV Power
Systems 6-34
7 SYSTEM DESIGN 7-1
7.1 Design Philosophy 7-1

7.2 System Design Procedure 7-2

7.3 Codes and Standards 7-15
7.3.1 Codes 7-15
7.3.2 Standards 7-16
7.3.3 Manuals 7-17
7.3.4 Approved Equipment Listings 7-17

7.3.5 Notes 7-18
7.3.6 Applicable Document List 7-18

7

iv
CONTENTS (Continued)
Section Title Page
8 INSTALLATIONS, OPERATION AND MAINTENANCE 8-1

8.1 Introduction 8-1

8.2 Power Outages 8-1

8.3 Reliability and Maintainability 8-2

8.4 Operation and Maintenance Tradeoffs 8-3

8.4.1 Operation and Preventive Maintenance 8-3

8.4.2 Corrective Maintenance 8-5

8.5 System Maintenance 8-8

8.5.1 Maintenance Concept 8-8

8.5.2 Maintainability Design 8-9

8.6 Logistics Design 8-11

8.6.1 Supply Support 8-11

8.6.2 Power System Drawings 8-13

8.6.3 Tools, Test Equipment, and Maintenance

Aids 8-13

8.6.4 Technical Mannuals 8-14

8.6.5 Training 8-15

8.7 Installation Design Considerations 8-15

8.7.1 Physical Considerations 8-15

8.7.2 Equipment Housing and Structure

Considerations 8-16

8.7.3 Installation Checkout and Acceptance

Testing 8-16

9 SITE SAFETY 9-1

9.1 Personnel Safety Checklist 9-1

9.1.1 Safety & Health Standards 9-1

9.1.2 Electric Shock 9-2

9.1.3 Toxic &-Flammable Materials 9-2

9.1.4 Fire Safety 9-2

9.1.5 Excessive Surface Temperatures 9-3

9.1.6 Equipment Identification Labeling 9-3

9.1.7 Physical Barriers 9-3

V
CONTENTS (Continued)
Section Title Page
9.2 Facility Safety Checklist 9-4

9.2.1 PVPS Safety Protection from

Environmental Conditions 9-4

9.2.2 PVPS Safety Protection from Man-Made

Conditions 9-5

9.2.3 PVPS Safety Protection from Component

Failure 9-6

9.3 References 9-6
10 DESIGN EXAMPLES 10-1
10.1 Remote Multiple-Load Application 10-i
10.1.1 Northern Hemisphere Location 10-1

10.1.2 Southern Hemisphere Location 10-2

11 INSOLATION 11-1
11.1 Introduction II-I
11.2 Insolation Calculation Programs 11-5

11.3 Statistical Insolation Computations 11-13

11.4 Sun Angle Charts 11-15

11.5 Row-to-Row Shading 11-15

12 PHOTOVOLTAIC SYSTEM COMPONENTS 12-1

12.1 Solar Cell Modules 12-1

12.2 Batteries 12-7
12.3 Dc Regulators 12-9

12.4 Dc Motors 12-10
13 GLOSSARY OF TERMS 13-1
13.1 Definitions of Photovoltaic Terminology 13-1

13.2 Conversion Factors 13-3
14 PHOTOVOLTAIC POWER SYSTEM EQUIPMENT SUPPLIERS 14-1

14.1 Photovoltaic Cells, Modules 14-1

14.2 Batteries 14-2
14.3 Power Conditioning Equipment 14-3

14.4 Direct Current Motor-, and Load Devices 14-5

vi
CONTENTS (Continued)
Section Title Page
APPENDIX A WORLDWIDE INSOLATION DATA A-1
APPENDIX B FAILURE RATES FOR RELIABILITY ESTIMATION B-i
B.I Failure-Rate Trends B-i
B.2 Sources of Failure-Rate Data B-2
B.3 Estimated Failure Rates for Certain
Items in the Typical PV System B-3
APPENDIX C LISTING OF SPONSORS OF CODES AND STANDARDS C-i
C.I List of Codes and Standards Agencies and
Their Addresses C-I
C.2 Listing of Codes and Standards by Agencies C-2
REFERENCES
R-I

ERRATA SHEET

o
InExhibit 11.2-4, "Listing of an HP-67 Insolation Computation

Program", corrections shown parentheticallY in the following
tabulation of affected steps should be made:
Step No. Key Strokes Key ode
001 f LBLA (31) 25 11
043 g x (>) Y 31 (63)
110 f cos 35 73

138 hT (35) 73
152 hT (35) 22
200 h RTN (35) 22
o In Exi~bit 11.2-3. ~~pagraph 4 ("Example"), the tilt angle should
be 30
instead of 20 . The paragraph which follows is also numbered
"4" and !,huld be changed to "V".

V1
EXHIBITS
Exhibit
Page
2-1 Flow Chart, Photovoltaic Stand-Alone Systems
Preliminary Engineering Design Handbook
2-2
3-1 Generalized Stand-Alone Direct Current Photovoltaic
Power System Block Diagram
3-2
4.1-1 Load Diversity
4-3
4.1-2 Load-Reduction Strategies
4-4
4.1-3 Disadvantages of Dc and Ac
4-6
4.2-1 Terminology for Large-Scale Photovoltaic Installations 4-8
4.2-2 Series/Parallel Circuit Nomenclature
4-10
4.2-3 Module Output and Intermediate Loss Mechanisms
4-11
4.2-4 Operation of a Solar Cell
4-13
4.2-5 Equivalent Circuit of a Solar Cell
4-15
4.2-6 Typical Array Characteristics
4-16
4.2-7 Current-11oltage Characteristics of Cells in Series
and Parallel
4-18
4.2-8 Protection From Open Circuit Failures
4-20
4.2-9 Array Power Loss Fraction Vs. Substring Failure Density 4-23
4.2-10 Typical Available Silicon Solar Modules
4-25
4.2-11 Nominal Array Costs (1975 Cost Levels)
4-26
4.3-1 Characteristics Summary Table: Commercially Available
Batteries
4-29
4.3-2 Lead-Acid Battery Characteristic Curves
4-30
4.3-3 Lead-Acid Battery Failure Mechanisms
4-34
4.3-4 Typical Battery State of Charge (SOC) History 4-35
viii
EXHIBITS (Continued)
Exhibit Page
4.4-1 Self-Regulated PV System 4-42

4.4-2 I-V Curve of PV Module Exhibiting Self-Regulation 4-42

4.4-3 Voltage-Regulated PV System 4-42

4.4-4 Simplified Block Diagram For a Maximum Power

Tracking Controller 4-45

4.5-1 Summary Descriptions of Backup Systems 4-55

5-1 Minimum Data Requirements to Establish Feasibility 5-2

5-2 General Checklist for Detailed Design 5-3

6.1-1 Average Monthly Insolation (kWh/m2-day) and the

Ratio of Standard Deviation (Sigma 1) to Average 6-3

6.1-2 Horiz-n Profiles for Two Candidate Sites 6-6

6.2-1 Quick Sizing Computational Procedure for Array

and Storage 6-10

6.2-2 Battery Storage Requirements for 1% LOLP 6-11

6.2-3 Effect of Depth of Discharge on Battery Life on Typical

Lead-Acid Motive Power Type Cell 6-12

6.3-1 Components, System Costs and Ecooomic Parameters 6-16

6.3-2 Photovoltaic Power System Preliminary Design Life Cycle

Cost Computation 6-17

6.4-1 Reliability Functions for Exponential (Random) and

Gaussian (Wearout) Facilities 6-19

6.4-2 Partial Description of Requirements for Hypothetical

Customer Application 6-22

6.4-3 Example Reliability Allocation for a Hypothetical

System 6-23

6.4-4 Functional Rleliability Block Diagram 6-25

6.4-5 Functional Oriented lieliability Block Diagram 6-25

6.4-6 Optional Module Configurations: (A) Series:

(B) S !'ci
I6-26
EXHIBITS (Continued)

Exhibit

Page
7.2-1 Loss-cf-Load Probability Computational Procedure 7-3

7.2-2 Cumulative Distribution Function for the Normal Curve 7-4

7.2-3 Example of Loss-of-Load Probability Computation 7-7

7.2-4 Listing of a TI-59 Program for Calculating Loss-of-Load

Probability 7-8

7.2-5 Instructions for the Operation of the TI-59 Program

for Computing the Loss-of-Load Probability 7-9

7.2-6 Listing of an HP-67 Program for Calculating Loss-of-Load

Probability 7-10

7.2-7 Instructions for the Use of the HP-67 Program for

Calculating Loss-of-Load Probability 7-13

7.2-8 Typical Cases for the Loss-of-Load Probability 7-14

8.2-1 Causes of Power Loss in PV Systems 8-1

8.4-1 Reliability Improvement with Standby Redundancy
8-7

10.1-1 Multiple Load Application Monthly Load Summary 10-3

10.1-2 Multiple Load Application Equipment Sizing 10-4

11.1-1 Insolation Computation for a South-Facing Array 11-2

11.1-2 Insolation Computation Example: Washington, D.C. 11-3

11.1-3 Ground Reflectances for Various Surfaces 11-4

11.2-1 Instructions for Operating the TI-59 Insolation

Computation Program 11-6

11.2-2 Listing of a TI-59 Insolation Computation Program 11-7

11.2-3 Instruetions for Operating the I-IP-67 Insolation

Computation Program
11-9

11.2-4 Listing of an IIP-67 Insolation Computation Program 11-10

11.3-1 Generalized KH Distribution Curves 11-14

x