Design Your Own Off Grid System

PV

Photovoltaic Panels

There are three basic types:
1. Mono-crystalline: Square and Round cells make up the design of the panel. These panels are the most efficient for space to power output ratio.
2. Poly-crystalline: Very similar to the single crystal panels above, these Panels have a speckled blue pattern and are almost as efficient for space to power output.
3. Thin Film: These panels used very little silicon to manufacture, if any at all. The photon-electron conversion system is part of a very thin layer of silicon and is attached to a non-silicon substrate, like steel, aluminum or plastic.

GY

Electric Generator

Example: (Generac Quiet Source, More Information)

Note:
The key difference between Grid-Interactive Systems and Off-Grid Systems are:
1. Grid-Interactive Systems can also have generators, there may be some generator specification requirements for it to work correctly.
2. Off-Grid System can also have Electrical Meters. Off-Grid simply means the Inverter is unable or is programmed not to sell power by pushing energy out through the AC Input.

AC

AC Disconnects

Example:
1. MidNite Solar E-Panel series AC/DC Disconnect, More Information
2. Outback Power FLEXware FW500, More Information

NV

DC to AC Inverter

Example: (Outback VFX3524 Inverter, More information
1. VFX3524 is used with a 24 Vdc Battery Bank, like 4 each 6 Vdc batteries.
2. The VFX3524 can convert 3500 Watts of power from a properly sized battery bank -or- push 3500 Watts of power from PV, Wind or Water onto the Grid.

DC

DC Disconnect

CC

Charge Controller

Charge Controllers come in three basic sizes:
1. Small: Portable Power & Point-of-Use applications typically only require < 200 Watts of conversion.
2. Medium: Off-Grid, Backup, Water Pumping applications controlling >200 Watts to < 3000 Watts of power.
3. Large: Off-Grid, Grid-Interactive, Whole House systems with > 3000 Watts of power.

Example [Medium]: (Outback Power MX60 Solar Charge Controller, More Information)
1. The specification for MX60 is 60 Amps DC.
2. Using a 48Vdc Battery bank, the MX60 can handle 2880 Watts of PV.
3. Using a 24Vdc Battery Bank, the MX60 can handle 1440 Watts of PV.

BT

Charge Controller

The type and size of the battery bank depends on two main factors:
1. Amount of energy to power those backup items all at once (Some or All items ON at once).
2. The amount of time you expect Any item to have backup power.

Example:
1. You have 11 each 13 Watt Compact Fluorescent bulbs + on 75 Watt TV.
2. You need to run all of these items for up to 3 days in a row, 8 hours each day, with no Sun or Grid.
3. 11 x 13 Watts + 75 Watts = 218 Watts.
4. 3 days x 8 hours = 24 hours.
5. 218 Watts x 24 hours = 5232 Watt-Hours
6. As a Rule, batteries should not be drained more than 50%.
7. 5232 Watt-hours / 50% = 10464 Watt-hours. You need at least a 10464 Watt-hour Battery

Double Take: Most Batteries are measured in Amp-Hours of Capacity! How do you convert? Divide the battery bank voltage by the Watt-Hours you need.
1. 10464 / 24 Vdc = 436 Amp-Hour Bank
2. Each Battery is 6 Vdc.
3. 24 Vdc / 6 Vdc = 4 Batteries (each one having 436 Amp-Hour capacity, if not...
4. For instance, each battery is 218 Amp-Hours.
5. 436 Amp-Hours / 218 Amp-Hours = 2 Parallel Strings
6. Two Parallel String x Four Batteries in Each String = 8 Batteries Total. (That means lots of battery connector cables, so try to buy the right size battery and limit the number of strings to 1, 2 or 3.