# MPPT and Solar design layed out

After a very educational thread with Sgt.Wookie, I have finalized my plan for the solar part of my rooftop unit.

For generation 1: (Overview)

Two 36 volt panels wired in parallel on a balance board (used to tilt the array to follow the sun) with a center fulcrum, using ball-barrings for friction reduction on the fulcrum shaft. On the end of the shaft will be a large 20 inch pulley. A v-belt from the 20 inch pulley to a 1 inch pulley on a stepper motor will control the table tilt from east to west. (you may have to change the pulley sizes depending on strength and number of degrees per step of your motor)

The gen1 will use a data table for positioning rather than an optical version. Sun location tables can be gotten from many resources on the web. The longitude and latitude of the solar array and the time and date will give you the angle of the sun. So, at 70degLon and 99degLat (not real) @ 2:15pm on December 5 2009, the sun will be at X location in the sky. The motor will tilt the table to X. The algorithm for sun location can easily be adapted into a microprocessor for continual tracking. (that will be incorporated in gen1.2)

Sgt. Wookie opened my eyes to a scaleable MPPT system that I have already started to put together (on breadboard) for testing. I was stuck in a know-it-all mindset which led me to believe that MPPT was "physical solar tracking" like the table design I have. It is not. MPPT reads the output voltage/current/temperature from the solar or wind generator and reads the batteries voltage, amperage, and temperature. A bunch of math goes by and determines the MAXIMUM POWER POINT for charging the batteries. The needs of a battery changes the closer to full it gets, as the solar output stays constant. The mppt Tracks the changes and bucks or boosts the levels for a severe efficiency gain. (They state up to 30% and greater, changes in sumer or winter)

The battery bank will use the mppt with a charging circuit and a desulfinator circuit to help achieve maximum battery life and efficiency.

When the batteries reach a full level of charge, many charging circuits divert the incoming power to resistors of some kind to dissipate the energy as heat. I will instead attach a DC to AC inverter to dump any extra power to the grid. This will slow the spinning of my power meter and result in lower usage bills.

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