1. Photovoltaic Systems Engineering Session 19a Solar+Storage Systems
SEC598F18
Photovoltaic Systems Engineering
Session 19a
Solar+Storage Systems
Stand-Alone Systems, part 2
November 07, 2018

2. Stand-Alone PV Systems
Stand-Alone Residence: Floor Plan

3. Example 2. A stand-alone cabin
Design steps in a stand-alone PV system
Examination of site and estimation of performance
Securing financing
Carrying out PV system engineering and design
Electrical loads (DC and/or AC)
Connection to charge controllers and batteries
Selection of inverter and BOS
Securing relevant permits
Construction
Inspection
Performance monitoring

4. The Ah loads listed
have been corrected
for inverter and wire
losses

5. Example 2. A stand-alone cabin
In other words:
The kitchen and dining room lights have “nameplate” power draw of:
The refrigerator power draw is:

6. Example 2. A stand-alone cabin
The average amp-hour load for each device is given by
where Toperation is given by

7. Example 2. A stand-alone cabin
For Example:
The kitchen light in November has a weekly Amp-hour requirement:
The receptacles have a weekly Amp-hour requirement:

8. Example 2. A stand-alone cabin
Corrected weekly loads

9. Battery Requirements

10. Example 2. A stand-alone cabin
Battery Selection Assumptions: Autonomy: 3 days C-rate: C/72 Possible candidate: 12V, 244Ah Array: 8 batteries – 2 parallel sets of 4 in series: Therefore: 48V, 488Ah

11. Battery Requirements

12. Latitude-15o, Latitude, Latitude+15
Array Sizing and Tilt
Approach:
Compute the design current for each month, at each of three angles:
Latitude-15o, Latitude, Latitude+15
Summer All Year Winter

13. Array Orientation (Denver, CO)

14. Array Orientation (Denver, CO)
Each of the currents is the minimum allowable current (to charge the batteries fully)
The highest minimum current in this table is chosen to provide adequate current for the most challenging month

15. PV Array and Charge Controller Design
Assumptions:
Battery array charging voltage – 54V
Battery array charging current – 7.8A
Charge controller efficiency – 97%
Wire losses – 2%
Include a factor to account for miscellaneous losses (90%)

16. PV Array and Charge Controller Design
Assumptions:
Consider modules with these characteristics:
Vmp = 17.6V; VOC = 22V
Imp = 7.4A; ISC = 8A
Pnameplate = 130W
Four modules connected in series:
Vmp = 70.4V
Imp = 7.4A
Pnameplate = 520W
Choose an MPPT controller
Vin,max > 4VOC = 4(22V) = 88V
Iin,max > ISC(1.25) = (8)(1.25) = 10A

17. Example 2. A stand-alone cabin
Wiring

18. Wiring Diagram