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

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

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

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

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:

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

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:

Example 2. A stand-alone cabin Corrected weekly loads

Battery Requirements

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

Battery Requirements

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

Array Orientation (Denver, CO)

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

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%)

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

Example 2. A stand-alone cabin Wiring

Wiring Diagram