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

Session 19 content Stand-Alone PV Systems Scale of stand-alone systems Design basics Inverter and battery selection BOS components

Learning Outcomes An examination of the original photovoltaic systems at small scale (solitary electrical components).

Stand-Alone PV Systems – Design Steps Examples of stand-alone PV systems Solar powered accent lights Solar powered portable devices Solar powered water pump Solar powered fan Solar powered lighting systems Stand-alone refrigerator Stand-alone residences Stand-alone communication systems

Stand-Alone PV Systems – Design Steps Solar powered portable devices

Stand-Alone PV Systems – Design Steps Solar powered portable devices

Stand-Alone PV Systems – Design Steps Solar powered fan

Stand-Alone PV Systems – Design Steps Stand-alone (and remote) structure

Stand-Alone PV Systems – Design Steps Stand-alone communication system

Stand-Alone PV Systems – Design Steps Steps in stand-alone component design Evaluation of solar availability, electrical consumption, essential electrical loads Battery selection PV array sizing Module selection Charge controller selection Inverter selection Balance of system

Example 1. A stand-alone solar-powered refrigerator for home brewing. A friend has an old house in Phoenix with a set back garage that has limited electrical service. Upgrading the service would require extensive trenching from the service panel, which he would prefer to avoid. In this project, we shall design a stand-alone PV system designed to power a refrigerator that will be used for fermentation and aging 5-gallon containers of home-brewed beer. This beer will be Peter’s Solar IPA or something similar.

Example 1. A stand-alone solar-powered refrigerator for home brewing. Evaluation of solar availability, electrical consumption, essential electrical loads The Kenwood refrigerator draws about 386kWh per year (Energy Star sticker), so that it has a daily use of roughly 1.1kWh. This is consistent with its nominal power draw (200W) and 5 hours/day operation. To account for inverter losses of approximately 5% and to meet electrical surges at start, I shall choose a 300W pure sine wave inverter:

Example 1. A stand-alone solar-powered refrigerator for home brewing. Inverter: Aims, model pwri30012s 120 V ac, 10V-12V dc input Load on the batteries would be : where the refrigerator load is adjusted by the inverter losses (0.95) and approximate wire losses (0.98).

Example 1. A stand-alone solar-powered refrigerator for home brewing. The energy capacity of the batteries has to be adjusted for round trip charge/discharge efficiency of the batteries and the depth of discharge limit. We shall use Pb-Acid batteries, so c/d (roundtrip) efficiency is about 88% and the state of charge (SOC) has to remain above 20% (or the depth of discharge less that 80%), so the adjusted load is: We can use 12V batteries, so the daily charge capacity would be:

Example 1. A stand-alone solar-powered refrigerator for home brewing. This is sunny Phoenix, so let’s design the system for one day of autonomy. There are many Pb-acid batteries at 12V with capacity of 75 or more Ah. Let’s use two DEKA AGM batteries with these characteristics:   Batteries: DEKA, 12V, AGM Pb-acid Capacity at C/100: 91Ah Capacity at C: -40F to +140F (good for use in Phoenix) The solar modules will be mounted on the west-facing roof of the garage (ok for Phoenix, plenty of sun late of the afternoon), and according to NREL, there is an average of 6 Peak Solar Hours per day. Assuming that the output from the solar modules will be reduced by losses in the charge controller (efficiency of 85%), the readjusted energy going to the inverter is:

Example 1. A stand-alone solar-powered refrigerator for home brewing. So the PV array must produce electrical power of this value: There are a lot of manufacturers that produce 200+ Watt modules. So choose: Charge Controller: Morningstar SunSaver MPPT PV Modules: Canadian Solar 225W

Example 1. A stand-alone solar-powered refrigerator for home brewing. Note: This figure (from M&A) is for illustration only. The correct component values are on the previous slides