Mixing wind turbines with the tropics

Lead Image © Boris Klissourski, 123RF.com

Into the Wind

We describe the further saga of Project Curaçao, a Raspberry Pi-based weather station powered by wind and sun.

In an article on wind power in the previous issue of Raspberry Pi GEEK [1], I talked about designing a solution that would allow a small computer system on a remote island to operate on solar and wind power. Since then, I actually installed the weather station system – on the Caribbean island of Curaçao on March 12, 2014.

The system is still functioning well in an unattended mode on the island as of the writing of this article (April 2014). However, the wind turbine that was suppose to provide assistance to the primary solar-based power system met with premature and unexpected misfortune. In this article, I describe what happened and what I intend to do about it, but I'll begin with a brief description of the project for those who missed the previous issue.

What Is Project Curaçao?

Project Curaçao is a sensor-filled project designed to hang on a radio tower on the island nation of Curaçao. Curaçao is a desert island 12 degrees north of the equator in the Caribbean. It is a harsh environment with strong tropical sun, salt spray from the ocean, and unremitting heat, but it is a beautiful place to visit and a challenging spot to build and install a Raspberry Pi-based environmental monitoring system. The system consists of a Raspberry Pi running a Python-based control system, a RasPiConnect server (for remote monitoring and remote control), and an Arduino acting as a power system manager and watchdog system overseeing the Raspberry Pi.

The basic design for Project Curaçao is shown in Figure 1. Figure 2 shows a block diagram of the power subsystem. The 50W wind turbine is connected through a set of relays to the battery charging system. The Arduino watchdog switches the input of the battery charging system from solar to wind based on time (sunrise/sunset) or by direct control from the control panel on RasPiConnect [2]. A voltage protection circuit between the turbine and the charger protects the charger and regulator from overvoltage conditions (anything above 18V in this case).

Figure 1: Project Curaçao configuration.
Figure 2: Power subsystem for Project Curaçao.

Because I knew this wind turbine would not be generating very much power (my estimate based on loaded measurements was about 100mA (0.5W) in 15mph winds), I decided to use only the wind turbine to trickle charge the Raspberry Pi's battery at night. The Raspberry Pi (Model A) takes about 1.5-2W to run the system. The WiFi connection makes up almost a third of this power.

Installation of the Turbine

With the help of Geoff Howard, expert tower climber (and patient man), I installed the wind turbine and the box up on the radio tower. We mounted the wind turbine as high as the wire would reach, because the wind speed typically increases 15 percent every 10 meters above the ground. This was readily proved to be true as we climbed the tower into the gale. The final installation was completed on March 15, 2014 (Figure 3).

Figure 3: I installed the wind turbine on March 15.

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