Robotic solution for harnessing solar power in the desert

17 May 2011

Robotic researchers from Germany believe they hold the key to future global electricity generation.

The team from the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA) approached Desertec, a consortium whose big idea is the building of solar-thermal plants in the desert. Desertec has calculated that if just 1% of the Sahara Desert was devoted to solar energy production, enough electricity would be generated for the entire world at current annual levels of consumption.

The IPA has been building on kinematic and motor and drive research first begun in the 1980s over the last three years. Dr. Andreas Pott, leader of the IPA team, explained: “The idea of combining the power of a crane with the speed and accuracy of a robot is something other people have tried to do, but computer processing power was simply not advanced enough for cable robots to succeed until now.

“Our IPAnema robot consists almost entirely of cables and winches. The winches are fixed to movable square metal scaffolding. Held between the cables, which are controlled by the winches with the aid of a computer, is the tool, known as the end effector. In the past, it was hard to predict what the result would be when the actuators were moved, but now we are able to give commands to the winches in a completely synchronised way, thanks to computer modelling. We have taken pure science and put it to work on industrial grade devices.”

The demonstrator robot built last year is 5m high and has footprint of 9m x 7m. In reality, even this would be too small for the Desertec Project. It is estimated that this robot would have to be the size of a football pitch. However, unlike cranes that, owing to their swinging loads, must move slowly, IPAnema can accelerate quickly in full control of its load thanks to its automatically controlled winches. The actuator drum contained within the winch produces force that is transmitted through the cable over long distances. These high forces can be used for both heavy loads and for speed simply by changing the gearbox between operations.

Although IPAnema currently only exists in demonstrator form, it has, from the outset, been aimed at the needs of industry. As a result, only industrial components have been used. All interfaces have been designed to connect with standard production equipment. When work began on the IPAnema’s controller architecture and NC control in 2008, the team deliberately set the robot kinematic challenges by attempting to integrate it with other IPA research projects. This focus on prosaic details such as bearings, motor and drive technology and software paid dividends when the team was able to quickly manufacture eight winches and assemble IPAnema just over a year ago.

“When designing a robot capable of disparate tasks, such as lifting the 7 tonne collectors, consisting of dozens of parabolic mirrors, or laying cabling, flexibility is the key issue,” said Dr. Pott. “We have experimentally proved that we can reconfigure our robot by decreasing the payload by an half or a third and transfer that capacity into an increase in speed by the same factor. This doesn’t just have application in solar energy installation, we believe our technology could have just as transformational an effect on shipbuilding, aerospace, wind turbines, the erection of electric transmission lines, or indeed, any large scale construction project previously reliant on cranes.”

Although the Desertec project still leaves many political questions unanswered, the technical obstacles the mega project would create appear to have been potentially addressed by IPAnema. Desertec’s initial phase should see 100m mirrors covering an area of 36,000km2.

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