Solar Power on the Pi / Arduino in the Caribbean

Project Curacao is a remotely controlled (from 3500 miles away) Solar Power and Wind Powered Raspberry Pi / Arduino project.  It has a Raspberry Pi Model A running the

higher level functions (graphs, database, remote control, camera) and an Arduino Mega 2560 running the power management system.   The project was started in June 2013, deployed in March 2014 and received an upgrade to a number of systems in October 2014.

The box is completely solar powered.  No connection to the mains.  The project also uses a Wind Power Turbine for trickle charging at night.

The Solar Power Panels

First the good news. The Adafruit solar panels survived 6 months in the sun and rain in excellent condition. No trace lifting (a Curacao expert on solar cells, Brett Ruiz, told us that trace lifting and seal breaking is a big problem on the island) and they were perfectly

clean. Our last test of solar panels and lights were 3 meters lower and 10 meters closer to the ocean. Those lasted less than three months. We made sure no one cleaned these panels during the six months in Curacao. The picture of the 6 month old solar cells is to the right. Those are clouds reflecting in the panels, not dirt.

Addressing the Solar Power Issue

We had a power problem with the Arduino Battery Watchdog. On a very cloudy week, it would lose battery power and then lock up in some odd state and never come back up. We needed more power (although adding the external WatchDog timer also fixes the issue) so we added a new solar panel to the Arduino and added a new solar panel for the Raspberry Pi. About 70% more power for the Arduino and about 25% or so more for the Raspberry Pi. These numbers are less than you would expect because of the angles of the panels to the 12 degree tropical sun. Angle to the sun makes a huge difference.

Now the power RasPiConnect screen looks really good. The graph below shows the voltage from the solar cells go above 5V on a daily basis which indicates the battery is fully charged. The Raspberry Pi still does not get enough energy to run 24/7, but since the voltage goes over 5V on the Pi solar cells on most days, it’s clear that the limitation is how much we can store in the battery, and not the cells themselves.  RasPiConnect is a control panel building app for the iPhone / iPad from MiloCreek.  Here is a tutorial on how to build a RasPiConnect control panel.

And the Arduino Battery WatchDog power subsystem.

SunAir Solar Power Controller

SwitchDoc Labs is releasing an 3rd generation improved solar cell charger and sun tracker called SunAir late fall of 2014.  The box in Curacao is running the 1st generation charging system and we have improved the functionality and reduced the cost.  SunAir is the sum total of all our Project Curacao experience and really nails what is needed for this kind of system.  We just received the 3rd Generation SunAir boards at SwitchDoc Labs and they are being tested in the next few days.  Then we will do a release to manufacturing.

Oh, and SunAir will charge your phone too, which is helpful in Curacao where the mains power goes away sometimes.