How do you clean a clean-energy generating system? With a microcontroller (and a few other parts, of course). An excellent example is US designer Scott Potter’s award-winning, Renesas RL78 microcontroller-based Electrostatic Cleaning Robot system that cleans heliostats (i.e., solar-tracking mirrors) used in solar energy-harvesting systems. Renesas and Circuit Cellar magazine announced this week at DevCon 2012 in Garden Grove, CA, that Potter’s design won First Prize in the RL78 Green Energy Challenge.
The nearby image depicts two Electrostatic Cleaning Robots set up vertically in order to clean the two heliostats in a horizontal left-to-right (and vice versa) fashion.
Potter’s design can quickly clean heliostats in Concentrating Solar Power (CSP) plants. The heliostats must be clean in order to maximize steam production, which generates power.
Built around an RL78 microcontroller, the Electrostatic Cleaning Robot provides a reliable cleaning solution that’s powered entirely by photovoltaic cells. The robot traverses the surface of the mirror and uses a high-voltage AC electric field to sweep away dust and debris.
Object oriented C++ software, developed with the IAR Embedded Workbench and the RL78 Demonstration Kit, controls the device.
The RL78 microcontroller uses the following for system control:
• 20 Digital I/Os used as system control lines
• 1 ADC monitors solar cell voltage
• 1 Interval timer provides controller time tick
• Timer array unit: 4 timers capture the width of sensor pulses
• Watchdog timer for system reliability
• Low voltage detection for reliable operation in intermittent solar conditions
• RTC used in diagnostic logs
• 1 UART used for diagnostics
• Flash memory for storing diagnostic logs
The complete project (description, schematics, diagrams, and code) is now available on the Challenge website.