The Ketura Sun solar park in Israel’s Negev desert, which was built by Siemens AG and solar energy pioneer Arava Power, and is currently operated by Siemens AG, may be the world’s first solar energy production facility to be cleaned entirely by robots.
Located in the hot southern stretch of Israel’s Negev desert, between the Gulf of Aqaba and the southern tip of the Dead Sea, the solar panels at Ketura Sun are constantly soiled from frequent sand storms and virtually no rain.
This video shows the 4.95MW Ketura Sun solar field at Kibbutz Ketura, Israel.
Prior to using the autonomous method of cleaning, the panels were cleaned only nine times a year due to the expense of traditional, labor-intensive, water-based cleaning. The process used 540,000 litres of water annually (2.7 litres per panel in average conditions, and 4.3 litres per panel following a dust storm).
During the five days it took to clean all the panels, energy production dropped and work crews endangered sensitive equipment. Between those infrequent cleaning cycles, energy output was significantly diminished due to soiling.
Testing the robotic method
Siemens and Arava Power ran a test pilot of Ecoppia’s robotic, waterless E4 cleaning system and found that the autonomous solution effectively removed 99% of panel dust every day. It took less than three months to deploy 84 of Ecoppia’ robots over the entire Ketura Sun field, and today nearly 100 centrally-controlled E4 robots clean the entire field every night, ensuring maximum production efficiency during sunlight hours.
The way it works
The E4 robots use a soft microfiber and gentle air flow cleaning system, using gravitation to move dust particles downwards, and off the panel. The robotic system is driven by a control unit and sensors that guide the robots along each solar panel row.
This video shows how Ecoppia E4, the autonomous solar panel cleaning system, works.
The robots move along a rigid aluminum frame using wheels coated with polyurethane to ensure smooth movement and no force on the panels.
Each cleaning robot is powered by five electric motors – two motors driving the horizontal movement along the solar panel row, two motors powering the vertical up-and-down movement, and one motor operating the rotation of the microfiber elements. To maintain a smooth sustainable upward and downward movement, the E4 robot uses a winch system with two flexible, coated silicon rubber wires that operate angularly from opposite sides of the winch cylinder to the center point of the microfiber cylinder frame. Cleaning is performed at a pace of 54 square feet per 30 seconds, and typically takes place during the evening to avoid shading during electricity generation hours.
Managing the fleet
One master computer controls the entire fleet of robots and is programmed for daily cleaning at a defined hour, which is adjustable per the seasons of the year and the time of the sunset. The E4 system is supported by real-time and forecast data from The Weather Channel to help better inform plant operators of site conditions and impending extreme weather events.
The entire fleet of robots is remotely managed through the Master application or through SMS-based commands from any smartphone. In addition, real time analytics are offered through a web-based dashboard. The remote management of robots is enabled using programmable logic controllers (PLC), which store cleaning scenarios and communicates with the master application. Four electronic sensors embedded into each E4 cleaning robot ensure optimal cleaning performance with accurate measurement and monitoring of vertical and horizontal movement.
Robots powered by the sun
The E4 robots are self-powered by batteries charged by a dedicated solar panel. When the robots are not cleaning they are securely locked to a docking station outside of the solar PV row to ensure they are not affected by strong winds. And at the same time, robot batteries are charged through their solar panel, with full batteries typically supporting three sequential cleaning cycles. Energy consumption is further optimized with Ecoppia’s patented Eco-hybrid solution, which allows the robots to recover energy while they descend solar panels, enabling longer intervals between battery charges.
Working hard in the desert, the robots naturally pick up a lot of dirt and dust as they labour along the solar panels. They keep themselves clean by using a self-cleaning mechanism when they complete a descent. An additional self-cleaning routine is carried out at the end of the cleaning cycle, before the robot returns to its docking station.
“Ecoppia has changed the way we run the Ketura Sun field,” added Yanir Aloush, VP of Operations at Arava Power. “Less guesswork about when to clean, less downtime since there’s no need for on-site cleaning crews, and less external personnel.” Arava saw ROI on this project in less than 18 months. Less than three months into operation, Arava Power contracted Ecoppia for an additional five plants in the Middle East, totalling 35 MW.
Written by Anne Fischer, Managing Editor, Solar Novus Today