Thanks to modern control technology, the kite, that aircraft-like toy that has amused young and old for centuries, is fast emerging as an efficient alternative for wind-based energy generation.
By harnessing the persistently strong winds that blow 100 to 500 metres above the ground, EnerKites become novel wind energy harvesters capable of generating up to 90% of the time. The concept consists of a para-kite, capable of flying high in the atmosphere, attached to a line that is wound and unwound around a drum. During the reel-out phase, the wind attacks the kite creating a pull force that causes the drum to turn as the kite gains altitude and the line unwinds. This rotation, connected through the axis of a generator, enables the kinetic energy of the wind to be converted into electricity. When the kite reaches its maximum height, the pitch is changed and therefore the angle of attack. The drum is then used to reel the kite back in. But, because the wing is now almost stalled, the energy expended is much less than was harvested during the reel-out phase. This net energy surplus is what is available for consumption, perhaps in an outlying rural community with no connection to the grid.
While the method sounds simple, the automatic control required to make it practical has proved to be far more complex. In addition to the towing rope, two steering ropes must also be attached to the kite. Then, to make things even more challenging, the wind is a dynamic system full of short-term fluctuations. The negative gusts that can occur, while not too much of a problem for the flight characteristics, are an absolute nightmare for the engineers developing the control required for orderly winding and unwinding of the drum.
This month’s feature on power generation presents an article on how German based start-up, EnerKite, overcame the problems using sophisticated software and microdrives from Faulhaber. You’ll find it in 'Using wind energy efficiently'.
ARP 0108 – What you need to do
Last month, we published the first of a two-part article that came out of a recent round-table panel discussion on the imminent arrival of the latest revision of ARP 0108. This issue, to provide readers with some insight into the steps and processes required for compliance when designing and operating a plant utilising explosion protection apparatus, we posed a scenario and asked our expert guests how C&I engineers might ensure conformance with recommended practice.
The hypothetical plant is a bulk fuel loading depot. For each loading arm, the equipment located at the gantry includes a preset controller, a flowmeter, an additive injection controller, multiple solenoid valves, and an earth monitoring system. To comply with SAS 10108 and ARP 0108, we discussed what the design team and end users need to do in terms of overall concept, equipment certification, loop design, installation, commissioning and maintenance. See the article in 'ARP 0108 – What you need to do', complete with some handy flow diagrams to guide you through the process.
X-Change 2014
One of the highlights of the local automation calendar is the hugely successful annual Wonderware X-Change conference. This year’s event promises to be even bigger and better than usual, seeing the release of System Platform 2014 coincide with the launch of the new Foxboro Evo.
Evo, the latest process automation system from Foxboro, is designed to future proof the automation investment by allowing users to make investments in technology today, which will not be made obsolete by new innovations tomorrow. Traditional process automation, safety control, and advanced industrial applications, have all been incorporated into a single real-time automation platform. The underlying rationale is to improve operational integrity through the better process insight which can now be made available to operators.
Combine all of this with a keynote address by Mike Caliel, president of the Software and Industrial Automation division of Invensys, and the Wild Coast Sun from 6-9 April looks well worth the visit. We hope to see you all there.
PS: Thanks to all those readers who alerted us to the fact that some of the QR codes last issue were a bit cumbersome to work with on an Android platform, the IT team is already working on a sleeker solution for the April issue.
Steven Meyer
Editor: SA Instrumentation & Control
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