Energy harvesting working like a dream at Tata Steel 09 May 2013

Tata Steel, which is trialling a novel thermocouple from ABB that generates its own energy from the heat in the surrounding process, says the technology works.

Combining this energy harvesting technology with wireless communications eliminates the need to run wires to or from the device, says Nikhil Kumar, area electrical engineer for blast furnace No.5 at the Port Talbot steelworks.

"It would be a dream come true for an engineer to have a self-powered wireless thermocouple," he muses.

"You don't have to run any cable, which saves money on the installation and also eliminates the risk of burning or damaging the cable during operation."

Kumar confirms that the ABB device hasn't missed a single reading in the three months since it was installed, and has not had to resort once to its on-board battery backup.

The trial was initiated to see how the technology would cope in one of the harshest operating environments in industry. The thermocouple has been installed on one of the plant's steam lines, which operates at 120oC. The harvesting technology requires a temperature difference of just 30oC between the process and its surroundings to drive the instrument's electronics and transmit readings.

This contrasts with the results from a second thermocouple installed nearby to test what happens when an energy harvesting instrument can't get the temperature difference. This instrument has had to rely on its battery for the entire duration of the test.

Tata Steel has also been trialling wireless adapters fitted to a pair of pressure transmitters. The adapters enable all the instruments to communicate with one another, and with the plant's control system via a wireless gateway.

"We've installed a mesh of instruments around the blast furnace to test how they cope," explains Kumar. "The mesh has proved to be robust and the results are very promising going forward."

He says that the instruments are able to talk to the gateway from up to 50m away, if there is a clear line of sight. In practice, there are numerous walls, pipes and other obstructions around the plant, which brings that distance down.

In fact, the energy-harvesting thermocouple has been operating successfully at a distance of around 20 metres. Also, even though one of the pressure transmitters is inside a pump house so can't 'see' the gateway, it has been communicating with the thermocouple, which then passes on the data.

"It's quite a clever and robust way of communicating," states Kumar. "With the instruments communicating with their neighbours, as well as the gateway, the [network] mesh can continue to function, even if one of them is damaged or unavailable."

Brian Tinham

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