Off Grid & Your Own Mini Grid.

A Guide to the Basics …

 Creating your own Renewable Energy creation, its terminology, its distribution and handling and its use in a normal domestic household.

For newcomers, this Chapter is the present state (March 2020) in achieving and supplying your own electrical power, ie, Off Grid.  And I will talk about renewable energy, its terminology, its distribution and handling and its use in a normal domestic household.

Off Grid is always going to be difficult to fully understand, as there are so many variables with your own particular situation. The World is changing, and folk see generating and using their own created power as a big step forward.

I will give costs in Euros/US Dollar, and Items that I mention can/are purchased in Europe.

Please remember that the costs do not include Installation charges and the Installer charges, both of which can be very excessive, and make the project not cost effective.

For a normal Domestic property.

  1. A renewable energy supply , eg, PV, Photovoltaic Panels.  
  2. Controlling the energy supply to charge the batteries, Charge Controllers.
  3. Batteries, power storage.
  4. OzInverter, converts a low voltage 48vDC to a 240v/120vAC & allows AC to back charge and create a low voltage DC.
  5. Standby Power supply..

1.  PV.  Photovoltaic Panels.

The PV Panels should face the Sun at Midday for the Spring and Autumn Equinox.

On average for a normal domestic household, 15kW is about correct,  and that amounts to a required space/size in your garden with a PV array of between  20 meters by 5 meters.

That would be 60 panels each 250w, (1.6m x 1meter each)  and  that would be a array space of 18.5 meters  by  5.1 meters.

And for an Array of 46 panels at 330w, (1.7m x 1.2m each).  

15kW of Mono crystalline PV from  4,500 to 9,200 Euros.

2.  DC Charge Controllers.

These regulate the Power coming from your PV to safely charge your battery bank.

The photo on the left shows commercially available PWM, and MPPT good quality controllers.

Some of these can take up to 200volts dc Input and give out a regulated and controlled 48volts dc at 60amps, thats 2.8kWatts, (Amps X Volts = Watts) into your 48 volt battery bank. 

You will need many controllers operating and controlling the PV panels, and each controller can be from 200 to 850 Euros.              

Another solution for handling that 15kW of power from the PV array, is to use what is called 'AC Coupling'.

Houses that you see around the World with PV on the roofs will be using GTI's, (Grid Tied Inverters) that take the PV dc output and change it to ac and feed it back into the Mains Utilities Grid for that Country.  These GTI's are slave machines and need to see the correct ac voltage and the correct HZ frequency, so to get there internal electronics/transformer to operate before they will feed into the Grid a few volts over the Mains Utilities supplied voltage.  

There are many Good Quality GTI's available second hand, i use fleebay etc, and i prefer GTI's with a toroid transformer,   see below photo of previously used SMA's........ .       150 to 300 Euros each.  

 The 48vdc OzInverter creates a very stable 240vac or 120vac at a stable 50H or 60HZ and the GTI's back charge through the OzInverter to the battery bank.

Three methods of controlling the  back charging from GTI's is possible.           A.   Use the Internal codes/settings in the GTI's to sequential shut down when a specified ac output voltage is reached.            B.   Use dc voltage comparators circuit to shut down the GTI ac side with a relay when the DC battery voltage rises above a charging rate voltage.           C.    Use PWM dc controllers that are connected directly to the 48vdc battery bank. These Diversion controllers, (Morningstar Tristar PWM at about 200 Euros each), will regulate the charging and any excess power when the batteries are full and will dump/divert to other sources, ie, Air Heaters 2kW each or Hot water heaters. etc etc. 

For a 15kW Array I prefer using 4off 2.5kW GTI's for 10kW and using DC Charge controllers for the 5kW as these can gently finish charging that precious 48vdc battery bank.

page still under construction...........