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Solar MOOC Off Grid Solar PV System Design

Ryan Light, IRIS LLC

� Scenario � Load Analysis � Battery Sizing � Array Sizing � Charge Controller Sizing � Inverter Sizing � Lifestyle Changes

Welcome to Client A. In this scenario our clients are a retired couple who have built a 460 SqFt “Tiny Home” on a large acreage located outside of Ames, Iowa. Your site assessor has determined that the area is clear of obstructions and will have a daily access of 5.4 sun hours/day. They will live here year round as their primary residence.

� First and most important step in designing an off grid system.

� Take the time to learn/research the energy usage of each device.

� Take the time to learn/research the energy usage of the clients.

� Pay attention to phantom loads and seasonal usage.

� Measured Usage: 11.2kW/h per day � This gives us a starting point for the

batteries, solar panels and balance of systems components.

� Always attempt to talk the client into greater energy efficiency rather than a larger system.

� Determining Type of Battery to be Used: •  Lead Acid Vented •  Lead Acid Sealed •  AGM •  Gel Cells •  Li-Ion, Nickel, and others

� Battery Voltages •  2V •  6V •  12V •  Others

� Battery Amp/hours •  Size Increase=$$$$ •  Size Increase=Less Batteries

AC  Ave  Daily  Load   ÷  

Inverter  Efficiency   +  

DC  Ave  Daily  Load   ÷  

DC  System  Voltage   =  

Ave  Amp-­‐hours  per  Day  

11200   ÷   0.9   +   0   ÷   48   =   259  Ave  Amp-­‐hours  

per  Day   ×  Days  of  

Autonomy   ÷   Discharge  Limit   ÷  BaLery  AH  Capacity   =  

BaLeries  in  Parallel  

259   ×   3   ÷   0.5   ÷   350   =   4  DC  System  Voltage   ÷   BaLery  Voltage   =  

BaLeries  in  Series   ×  

BaLeries  in  Parallel   =   Total  BaLeries  

48   ÷   12   =   4   ×   4   =   18  

� For this scenario the clients found a good deal on bulk Kyocera 240W Panels

� From the Battery Sizing Sheets we can determine the Array Sizing

Average  Amp-­‐hrs/day   ÷  

BaLery  Efficiency   ÷  

Peak  Sun  Hrs/day   =  

Array  Peak  Amps          

259   ÷   0.8   ÷   5.4   =   60          Array  Peak  

Amps   ÷  Peak  Amps/module   =  

Modules  in  Parallel      

Module  Short  Circuit  Current          

60   ÷   8.23   =   7       8.91          DC  System  Voltage   ÷  

Nominal  Module  Voltage   =  

Modules  in  Series   ×  

Modules  in  Parallel   =   Total  Modules  

48   ÷   29   =   2   ×   7   =   12  

Total  Daily  Load  Wh/

day   ÷  Peak  Sun  Hrs/day   ÷  

BaLery  Efficiency   ÷  

PV  Temp  Losses   ÷  

Derate  Factor   =  

PV  Array  WaLs  

11200   ÷   5.40   ÷   0.80   ÷   0.90   ÷   0.90   =   3201  PV  Array  WaLs   ÷  

STC  WaL  RaZng   =  

#  of  Modules  Needed  

3200   ÷   245   =   13  Array  

Nominal  Volts   ÷  

PV  Module  Nominal  Volts   =  

#  of  Modules  in  Series  

150   ÷   29   =   5  

� Controller Types •  MPPT (Max Power Point Tracking) •  PWM (Pulse Width Modulation) •  Single Stage & Shunt Controllers •  Diversion Controllers

� For Controller Sizing we need information from the Panels and the Battery Bank

� Battery Bank info from earlier worksheet � Panel Info

Model Max Power

Voltage at Max Power

Current at Max Power

Maximum System Voltage

Open Circuit Voltage

Short Circuit Current

Series Fuse

Rating

Dimension (LxWxD) Weight

KD245GX-LFB

245 Watts

29.8 Volts

8.23 Amps 600V

36.9 Volts

8.91 Amps 15 Amps

65.43"x39"x1.8"

44.1 lbs

Module  Short  Circuit  Current   ×  

Modules  In  Parallel   ×   Safety  Margin   =  

Array  Short  Circuit  Amps      

Controller  Array  Amps  

8.91   ×   3   ×   1.25   =   33.4125       60  DC  Total  Connected  WaLs   ÷  

DC  System  Voltage   =  

Max  DC  Load  Amps              

Controller  Load  Amps  

    ÷       =                      

�  Inverters are greatly varied � Stand alone inverters are selected by AC Watts,

System Voltage (Batteries), and Surge Watts

AC  Total  Connected  WaLs   DC  System  Voltage   EsZmated  Surge  WaLs  

11200   48   13000  

� Clients must understand that they cannot live as if they are on Grid Power

� A backup system such as Wind, Generator, or Hydro is recommended.

� Install monitoring systems throughout � Understand the monitoring systems and

what they are telling you. � Decision for the night? What kind of

popcorn with the movie tonight…microwave or stove top?

� IRIS LLC � 1728 Hwy 67 � Princeton, IA 52768 � 563-340-2501 � [email protected] Thank

you!