Sunday, January 24, 2016

off grid transfer switch

Off grid solar and wind power has become more urgent, because governments constant hunt after more tax to finance the old fossil energy sociaty structure.

This post i about my 'off grid lite' system, and a smaller but important part in my off grid power system, the load handler. The load handler is a electronic off grid transfer switch that can handle switching and sourcing a huge amount of electricity, with low voltage drop, low head release, and low waist.

Background


I have 5200 watt installed grid tied solar cells, and i like to more than double this to become 100% self-sufficient.

But it is not possible to do that, without going to pay lot of taxes for the energy i need to send to the  grid in the summertime, and draw back in the winter time for a heat pump.

The cost of a off grid system capable to deliver this amount of power is a challenge. Automatic functionality and transfer switching between different sources, is also a hard job to create with low waist energy consumption, and operational stability.

Solution

The off grid lite system is made as a scalable and modular system, and in this system the load handler become crucial for operational stability, i a battery, solar and wind driven power plan. The tesla power wall is a upcoming solution, using fronius hybrid inverter from Austria, but the tesla wall have a cost that isen't micro economic scalable. You need a bigger amount of money to get started.

There fore i decided to start with what i have in my garage. Some old laptop batteries, a battery pack from salvaged electric scooter, old diy experimental solar panels, mosfets, din rack enclosure and more.

The 'off grid lite' system was born:
tesla power wall alternative


In the off grid lite system i use several load handlers. The load handler is mosfets used as switch and driven by a micro controller. I use arduino uno to measure off grid system variables and to turn load handler on and of.

The load handler is called 'arduino load handler' and the design is made to fit a DIN rail frame found on thingerverse. The electronic for the off grid lite system consist of several parts, and some can be found om my site http://en.techmind.dk/, more parts and drawings can be placed here and on my website as the project progress. For now you can find a BMS solution for salvaged labtop batteries and a arduino MPPT charger design whit printed circuit board.