IN DEPTH: March of the PV robots

The robots have taken over at the Ketura Sun solar farm in the Negev Desert.

Phalanxes of more than 80 machines — cleaning units designed by Israeli technology start-up Ecoppia to sweep efficiency-killing dirt and sand off PV modules — glide back and forth along the panel frames at the eight-hectare Siemens-Arava array each night, using an innovative microfibre and air-flow system to keep output from the 5MW pilot plant at its peak.

Results at the world’s first autonomously cleaned solar installation, in a brutally hot stretch of land between the Gulf of Aqaba and the southern tip of the Dead Sea, have been impressive.

A handful of dust on a PV panel can dim its efficiency by up to 40%. The remote-controlled E4 robots, by removing 99% of “soiling” from the panels, have boosted electricity production “markedly” at Ketura.

According to Ecoppia, the combination of the uptick in efficiencies and output seen at the project, along with the reduction in maintenance costs, would — extrapolated to a 300MW PV farm — translate into operational savings of $9m a year, with the investment for the water-free robotic system repaid in as little as 18 months.

“From our original research it became clear that [in utility-scale solar power] you had a 21st-century industry using cleaning technologies from the stone age,” says Eran Meller, chief executive of Ecoppia, which had previously launched intelligent, automated technologies in the medical and homeland security sectors.

“We want to help shift the industry closer to grid parity with gas and nuclear by finding a cost-effective solution for the time-consuming business of cleaning PV panels.”

The Ecoppia robots, each fitted with a small PV and battery unit, move across arrays guided by a polyurethane-coated wheel-and-winch system run off five electric micro-motors, pumping a steady stream of air to blow dust down and off the panels.

During and after each maintenance round, the E4s use a self-cleaning mechanism to shake off the built-up dirt and ready themselves for the next sortie. When not in operation, the robots are locked into a docking station to recharge. Fully charged, they can work autonomously for three shifts.

Ketura’s Suntech panels previously had to be cleaned nine times a year in a manual, labour-intensive, water-based process that could take up to five days a time. Now, the robots are geared up to clean 500,000 panels a month, working automatically for around 60 minutes after sundown each day. The operator can also send the troops out following sandstorms for “emergency cleaning”.

“The time required for manual panel cleaning was time during which the field operated suboptimally, and you also had the issue of work crews potentially endangering sensitive equipment,” notes Meller. “Then, in the interim between cleaning cycles, significant electricity production degradation owing to dust accumulation would occur, negatively impacting overall field efficiency and profitability.”

Ketura, which flows 9GWh a year on to the Israel grid, was a tough test for the E4s, as the site suffers frequent sandstorms and gets virtually no rain.

“There are many tasks that humans can do that robots can’t — this is not one of them,” says Meller. “When it comes to effectiveness, consistency, economics on a daily basis, there is no way you can match the E4s, even if you were assuming free labour, particularly in such a hostile environment.”

Arava Power’s vice-president of operations, Yanir Aloush, recently endorsed the Ecoppia system as having changed the way the company runs Ketura: “Less guesswork about when to clean, less downtime, since there’s no need for on-site cleaning crews, less external personnel on the ground — we are very excited by the potential upgrade the solution offers us.”

Ecoppia’s home market, where the government is moving to double its installed PV base in the next two years, looms large, with 500MW grid-connected and 200MW under construction.

“We have [contracts for] five major solar farms [totalling 40MW] that are expected to close imminently,” Mellar says.

Israel’s solar resource is one of the richest in the world. It has a direct normal irradiance — a measurement of the intensity of sunlight — of about 2MWh per square metre, similar to Saudi Arabia.

Ecoppia recently received panel maker JA Solar’s stamp of approval for its system, clearing the way for its robots to be installed at the Chinese manufacturer’s arrays worldwide. A similar commercial certification had previously been given to the E4 technology by Suntech Power.

The Middle East and North Africa are seen as a major market for the product, says Meller, with India and Latin American “very attractive” regions. “We are on track to meet and exceed our expansion plans, such that Ecoppia robots will be cleaning five million panels a month by the end of the year, while adhering to the highest standards of operational excellence.

“Many of the main players are now saying it is not a matter of ‘if’ but ‘when’ the robots will conquer the solar arena.”