1. Photovoltaic Systems Engineering Session 27
SEC598F17
Photovoltaic Systems Engineering
Session 27
Residential PV System Case Study
Construction, Inspection, Interconnection, Performance
November 28, 2017

2. Session 27 - Value to class members
Additional evaluation and analysis of a residential grid-tied PV systems
Operation
Life Cycle Costing
Payback Analysis

3. Grid-Tied PV Systems – The Design Process
Design Steps in a Residential Scale System
Examination of site and estimation of performance
Securing financing
Carrying out PV system engineering and design
Securing relevant permits
Construction
Inspection
Connection to the grid
Performance monitoring

4. Grid-Tied PV Systems – The Design Process
Step 4 – Securing relevant permits
Special overlay districts
Architectural considerations
Zoning ordinances
Setbacks, elevations, materials
Building permits
Construction practices; electrical enclosures, wiring, components
Engineering approvals
Mechanical considerations
Utility agreements
Connection arrangements; net metering rules; electrical signal quality

5. Step 4 – Securing relevant permits – P&D

6. Step 4 – Securing relevant permits – P&D

7. Grid-Tied PV Systems – The Design Process
Step 4 – Securing relevant permits
Special overlay districts
Architectural considerations
Zoning ordinances
Setbacks, elevations, materials
Building permits
Construction practices; electrical enclosures, wiring, components
Engineering approvals
Mechanical considerations
Utility agreements
Connection arrangements; net metering rules; electrical signal quality

8. Grid-Tied PV Systems – The Design Process
Step 4 – Utility Agreements
APS contracts and documents
Reservation to connect a homeowner’s generation facility to the APS Distribution System
The Interconnection Requirements for Distributed Generation document
Application to ensure that the PV system is qualified to participate (and have grandfathered rights) in the Net Metering Program

9. Grid-Tied PV Systems – The Design Process
Step 5 – Construction
Step 6 – Inspection
Step 7 – Connection to the grid
Step 8 – Performance monitoring

10. Step 5 - Construction

11. Step 5 - Construction

12. Grid-Tied PV Systems – The Design Process
Step 5 – Construction
Step 6 – Inspection
Step 7 – Connection to the grid
Step 8 – Performance monitoring

13. Step 6 – Inspections

14. Comparison of Two Residential PV Systems
5kW system
installed in 2010
3.5kW system
to be installed in 2014
Roof mounted
22 Siliken 225W poly modules
Sunny Boy 4kW inverter
No remote monitoring
Installed cost: $28,979
$5.85/W (dc)
Incentives:
Utility co. rebate: $13,365
Federal ITC: $8,694
State Solar Incentive: $1,000
Total OOP Cost: $5,920
$1.20/W (dc)
Elevated structure
14 Canadian 250W poly modules
14 Enphase micro-inverters
Enphase monitoring solution
Installed cost: $13,450
$3.84/W (dc)
Incentives:
Installer rebate: $1,000
Federal ITC: $4,035
State Solar Incentive: $1,000
Total OOP Cost: $7,415
$2.12/W (dc)

15. Grid-Tied PV Systems – The Design Process
Step 5 – Construction
Step 6 – Inspection
Step 7 – Connection to the grid
Step 8 – Performance monitoring

16. Step 7 – Connect ion to the grid

17. Net Metering At the end of each month, a utility bill is calculated:
Generation = N(kWh from utility) – N(kWh to utility) +/- N(credits from “energy bank”)
This is all at the retail rate
Once a year, the residual credits are cashed in
This is all at the wholesale rate
For APS solar customers, the “settle-up” date is 12/31
For SRP solar customers, the date is 04/30
This is a critical difference

18. Net Electrical Metering – Case 1
PV input = 0 PV
system
Solar Meter
Utility
Service Panel
UtilityMeter
To House Loads
UM runs forward

19. Net Electrical Metering – Case 2 (Self-Consumption)
PV input < Utility input PV
system
Solar Meter
Utility
Service Panel
UtilityMeter
To House Loads
UM runs forward,
but reduced

20. Net Electrical Metering – Case 3 (Power export)
PV input > Utility input PV
system
Solar Meter
Utility
Service Panel
UtilityMeter
To House Loads
UM runs in reverse

21. Grid-Tied PV Systems – The Design Process
Step 5 – Construction
Step 6 – Inspection
Step 7 – Connection to the grid
Step 8 – Performance monitoring

22. Recent Performance

23. Step 8 – Performance Monitoring

24. Step 8 – Performance monitoring
on-peak c/kWh; off-peak – 2.3c/kWh; average – 8c/kWh
All electricity costs – 12.3c/kWh

25. Step 8 – Performance monitoring

26. Step 8 – Performance monitoring
APS Net Metering

27. Step 8 – Performance monitoring
APS Net Metering – Generation Bill
Avoided Electricity Cost = 0.123$/kWh * 5225kWh = $643

28. Step 8 – Performance monitoring
SRP Net Metering
Avoided Electricity Cost = $643 - $130 = $513

29. Current residential PV system example
A spreadsheet was used to analyze this situation; plotting the results yields (for annual return)

30. Revised current residential
Payback –> 10.5 – 13.5 years