1. Session 13 (R) Case Study – Residential System Design, Construction, Operation, and Analysis February 24, 2016

2. Session 13 - Value to class members A case study to compare and contrast the “textbook” and actual design, operation, and analysis of a residential grid-tied PV system o Design process o Permitting and constuction o Operation o Life Cycle Costing o Payback Analysis 2

3. Grid-Tied PV Systems – The Design Process Design Steps in a Residential Scale System 1. Examination of site and estimation of performance 2. Securing financing 3. Carrying out PV system engineering and design 4. Securing relevant permits 5. Construction 6. Inspection 7. Connection to the grid 8. Performance monitoring 3

4. Grid-Tied PV Systems – The Design Process Design Goals in any Residential Scale System o Meeting expected (or modeled) performance  Engineering professionalism o Reliable performance  Standards and Codes o Safe operation  Standards and Codes o Architectural aesthetics  Building and Zoning 4

5. Grid-Tied PV Systems – The Design Process Step 1 - Examination of site and estimation of performance o Inspection of roof and yards o Evaluation of obstacles, shading, and structures o Examining the solar resource 5

6. Step 1 - Examination of site and estimation of performance Inspection of roof and yards 6

7. Step 1 - Examination of site and estimation of performance Inspection of roof and yards 7

8. Step 1 - Examination of site and estimation of performance South vs West 8

9. Step 1 - Examination of site and estimation of performance ASU Parking Structure 9

10. Step 1 - Examination of site and estimation of performance 14 modules: 7 x 2 array 10 PV array sizing and module selection

11. Motion of Sun Diagram – Phoenix North Pole Summer Solstice Equinox Winter Solstice 23.5 o zenith latitude Phoenix Latitude = 33.5 o N S 11

12. Grid-Tied PV Systems – The Design Process Step 2 – Securing financing o Cash Purchase o Dealer Credit o Power Purchase Agreement o Solar Lease  Monthly terms  Prepaid structure 12

13. Grid-Tied PV Systems – The Design Process Step 2 – Securing financing 13 K.Tweed, “Half of Small Solar Installers Don’t Offer Leases or PPAs,” GTM 01/04/16

14. Grid-Tied PV Systems – The Design Process Step 3 - Carrying out PV system engineering and design o Evaluation of space availability, solar availability, and electrical consumption o PV array sizing o Module selection o Inverter selection o Balance of system 14

15. Step 3 - Carrying out PV system engineering and design Evaluation of electrical consumption Average monthly usage – 440 kWh 15

16. Step 3 - Carrying out PV system engineering and design Comparison of electrical consumption to solar electricity production Annual total electrical usage – 5300 kWH (12. 440) Annual total solar electricity production – 6300 kWh o PVWatts - 3500 W system, 18 o tilt Ratio: 6300/5300 = 1.19; APS regulations, the ratio cannot exceed 1.25 16

17. Step 3 - Carrying out PV system engineering and design “Power Pergola” 17

18. Step 3 - Carrying out PV system engineering and design Inverter Selection -> Enphase Microinverters A microinverter is a compact inverter installed directly on the back of a PV module o Therefore in a PV array, each module has its own inverter – the PV modules now have an AC output, not a DC output o Each module is separately operated at its own MPP – they are connected in parallel, so the current loss from shading is eliminated o The wiring and the connections are simplified, and high DC voltages are eliminated o A typical microinverter has a 25 year expected lifetime – a dramatic increase over the expected 10 – 12 year lifetime of a high power central inverter 18

19. Grid-Tied PV Systems – The Design Process Step 4 – Securing relevant permits o Special overlay districts  Architectural considerations o Zoning ordinances  Setbacks, elevations, materials o Building permits  Construction practices; electrical enclosures, wiring, components o Engineering approvals  Mechanical considerations o Utility agreements  Connection arrangements; net metering rules; electrical signal quality 19

20. Step 4 – Securing relevant permits - HPO 20

21. Grid-Tied PV Systems – The Design Process Step 4 – Securing relevant permits o Special overlay districts  Architectural considerations o Zoning ordinances  Setbacks, elevations, materials o Building permits  Construction practices; electrical enclosures, wiring, components o Engineering approvals  Mechanical considerations o Utility agreements  Connection arrangements; net metering rules; electrical signal quality 21

22. Step 4 – Securing relevant permits – P&Z 22

23. Step 4 – Securing relevant permits – P&Z 23

24. Grid-Tied PV Systems – The Design Process Step 4 – Securing relevant permits o Special overlay districts  Architectural considerations o Zoning ordinances  Setbacks, elevations, materials o Building permits  Construction practices; electrical enclosures, wiring, components o Engineering approvals  Mechanical considerations o Utility agreements  Connection arrangements; net metering rules; electrical signal quality 24

25. Step 4 – Securing relevant permits – P&D 25

26. Step 4 – Securing relevant permits – P&D 26

27. Grid-Tied PV Systems – The Design Process o Special overlay districts  Architectural considerations o Zoning ordinances  Setbacks, elevations, materials o Building permits  Construction practices; electrical enclosures, wiring, components o Engineering approvals  Mechanical considerations o Utility agreements  Connection arrangements; net metering rules; electrical signal quality 27

28. Step 4 – Securing relevant permits – APS 28

29. Step 4 – Securing relevant permits – APS 29

30. Step 4 – Securing relevant permits – APS 30

31. Grid-Tied PV Systems – The Design Process Step 5 – Construction Step 6 – Inspection Step 7 – Connection to the grid Step 8 – Performance monitoring 10/14/15PSM SEEC Program F’1531

32. Grid-Tied PV Systems – The Design Process Step 5 – Construction Step 6 – Inspection Step 7 – Connection to the grid Step 8 – Performance monitoring 32

33. Step 6 – Inspections 33

34. Grid-Tied PV Systems – The Design Process Step 5 – Construction Step 6 – Inspection Step 7 – Connection to the grid Step 8 – Performance monitoring 34

35. Step 7 – Connection to the grid 35

36. Grid-Tied PV Systems – The Design Process Step 5 – Construction Step 6 – Inspection Step 7 – Connection to the grid Step 8 – Performance monitoring 36

37. Step 8 – Performance monitoring 37 on-peak - 14.4c/kWh; off-peak – 2.3c/kWh; average – 8c/kWh Cost of electricity – 14.3c/kWh Charge for electricity services – 15.9c/kWh

38. Step 8 – Performance monitoring 38

39. Step 8 – Performance monitoring Total PV generation for 2015 – 6185 kWh 39 Value of electricity = 5225*0.123 + 960*0.030 = $672 Annual Net Metering DEFG MonthAPS avgPVWattsAPS2015 PAPS2015 C Enphase201 5 Excess 2015 APS2015 (no solar)Net 2015Sum 2015 Generation Cost (F-E)(D+G)(D-E) Jan18037310627934162168-173 $0 Feb1773947939143342121-312-485$0 Mar1594397048457995165-414-899$0 Apr12854469545650105174-476-1375$0 May13662299559674115214-460-1835$0 Jun406660567344608264831223-1612$0 Jul9126117492626133511100487-1125$0 Aug11496117802525833311111528-597$0 Sep1058596583304524220803279-318$0 Oct640544165372478106271-207-525$0 Nov2055199239240210102-300-825$0 Dec14041810924430056165-135-960-$29 Annual Total5290633134684428618517575225-$29 Monthly avg440.8527.6515.4 Daily avg14.517.316.9

40. Step 8 – Performance Monitoring 3.5kW system installed in 2014 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) 40

41. Comparison of Two Residential PV Systems 5kW system installed in 2010 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) 3.5kW system to be installed in 2014 Elevated structure 14 Canadian 250W poly modules 14 Enphase micro-inverters o Enphase monitoring solution Installed cost: $13,450 o $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) 41

42. Economic Analysis Current residential PV system example Assume that the installed cost of a 3.5kW PV system is $3.84/W after all incentives are accounted for. Assume that the system will produce an annual electrical amount of 6300 kWh (as measured), although the annual electrical load is 5300 kWh. Assume the average utility cost of electricity as $0.123/kWh, but the PURPA value of electricity is $0.030/kWh. The plan here is to calculate the Life Cycle Cost (the numerator of the LCOE equation) on both an annualized and cumulative basis, and see when it crosses zero

43. Current residential Plotting the cumulative return for 25 years Payback – 10 years

44. Net Metering 44 At the end of each month, a utility bill is calculated: Generation = N(kWh from utility) – N(kWh to utility) – N(some credits from previous month) This is all at the retail rate

45. Net Metering 45 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

46. Revised Economic Analysis Revised current residential PV system examples Assume that the installed cost of a 3.5kW PV system is $2.12/W after incentives, or $7415. Assume that the system will produce a net electricity reduction amount through net metering of 5225 kWh (APS calculation), or 4168 kWh (SRP calculation). Assume the utility cost of electricity is $0.123/kWh and does not increase over the lifespan of the PV system. The plan here is to calculate the Life Cycle Cost (the numerator of the LCOE equation) on both an annualized and cumulative basis, and see when it crosses zero

47. Revised current residential Payback –> 10 – 14 years