Energy Harvesting Widens Wireless' Appeal

Developments in energy harvesting promise to banish battery issues.

By Seán Ottewell, Editor at Large

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Processors are showing increasing interest in installing wireless instruments. However, reliance on batteries and the cost of replacing them is causing some concerns. So, chemical makers should welcome rapidly emerging developments that enable vibrations or heat gradients to scavenge power that then can supplement or even supplant batteries. Already, a number of sites are pioneering use of such energy harvesting with wireless devices.

One of the most novel entrants into the market is the Intelligent Power Module (IPM) from Perpetuum, Southampton, U.K. (Figure 1). Jointly developed with Emerson Process Management, Austin, Tex., the IPM allows users to connect Perpetuum's vibration energy harvester to a Rosemount 3051S wireless pressure sensor — this delivers significant savings by avoiding the need to regularly replace batteries, even at fast update rates of a few seconds.

"To really get the benefits of wireless, you need a wireless power source. The ideal solution is an energy harvester that is 'fit and forget' and that will have a lifespan in excess of the wireless sensor network that it is powering," says Perpetuum president Roy Freeland.

However, the thinking behind the IPM goes further than this. "The big news here is the complete and simple interchangeability of the IPM unit. Not only can you use it with vibration energy harvesters, but also thermal harvesters from other suppliers such as Micropelt and Perpetua. You can even make use of any nearby 24V-DC supply that is often found in process plants," he notes.

Development of the IPM has taken place in parallel with work the International Society of Automation's ISA 100.18 Power Sources Working Group has carried out. One of the key objectives of this group, which Freeland co-chairs, is to define specifications for the interchangeability of various power sources and to define performance specifications so users can compare different harvesters and choose the optimum power source for each application.

"Although work is still ongoing to develop the standard, this is effectively the first technology to meet its requirements of providing simple interchangeability between different types of harvester. We hope that the draft standard itself should be published some time in the next 3–6 months," adds Freeland.

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For Emerson, the IPM has come about after many years of looking at different energy harvesting devices. "One of the earliest was solar panels, but these became a maintenance headache for some process users," says Wally Baker, Chanhassen, Minn.-based senior marketing manager, Smart Wireless, upstream oil & gas.

So the company started to work with Perpetuum's energy harvesters, subjecting them to conditions like high temperatures and pressures that its equipment typically must handle.

"We use the IPM to supplement the energy supply in our own devices. A typical Emerson power module giving one-minute updates from a pressure device has a ten-year battery life. If four-second updates are required, the battery life falls to under three years. So, the great advantage to having the IPM and vibration energy harvester is that you need never change the battery during the life of the device," notes Eric Milavickas, wireless sales & marketing director, Chanhassen.

Both Baker and Milavickas believe the IPM and energy harvesting will change how people think about wireless technology. At the same time, they acknowledge that simple and quick installation of smart wireless transmitters, IPMs and vibration energy harvesters is an important issue for process customers.

To this end, the company has conducted two U.S. field trials, one at a Firestone Polymers facility and the other at an OXEA plant.

The Firestone site trialed first-generation prototypes in a number of different applications. The twin goals for Emerson were to demonstrate ease of installation and the ability to run for extended periods under typical operating conditions.

"In terms of the first goal, installation was achieved quickly, with the system up and running in a couple of hours," notes Baker. "A similar hard-wired installation would have taken days or even a week if all new wire runs would need to be put in place. There are other cost implications: our customers are telling us that in North America it can cost up to $10,000 to install a point — and that's excluding the device. So standalone power options like the smart wireless power module and the Perpetuum vibration energy harvester with the IPM spoke volumes immediately."

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