Energy harvesting technology in action at Tata Steel
14 May 2013
Tata Steel is trialling an ABB thermocouple that is able to generate the energy needed to drive it from the heat in the surrounding process. Combining this energy harvesting technology with wireless communications eliminates the need to run any wires to or from the device.
“It would be a dream come true for an engineer to have a self-powered wireless thermocouple,” explained Nikhil Kumar, area electrical engineer for blast furnace No.5 at the Port Talbot steelworks. “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.”
According to Tata Steel the device has not missed a reading in the three months since it was installed, and has not had to resort to its on-board battery backup.
The trial was initiated to see how the technology would cope in such a harsh operating environment. The thermocouple is installed on one of the plant’s steam lines, which operates at 120°C. The harvesting technology requires a temperature difference of just 30°C between the process and its surroundings in order to drive the instrument’s electronics and transmit its readings.
This contrasts with the results from a second thermocouple, which was installed nearby to test what happens when an energy harvesting instrument is installed without the necessary temperature difference. This second 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 have installed a mesh of instruments around the blast furnace to test how they cope,” explained Kumar. “The mesh has proved to be robust and the results are very promising so far.”
The instruments are able to talk to the gateway 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 does reduce this distance. “The energy-harvesting thermocouple has been operating successfully at a distance of around 20 metres from the gateway. It hasn’t dropped a reading during the entire trial,” said Kumar.
And even though one of the pressure transmitters is situated inside a pump house that makes it unable to ‘see’ the gateway directly, it has been communicating successfully with the thermocouple, which then passes on the data to the gateway. “It’s quite a clever and robust way of communicating,” expalained Kumar. “With the instruments communicating with their neighbours as well as the gateway, the mesh can continue to function even if one of them is damaged or unavailable.”
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