Energy Harvesters reduce wiring and battery costs for wireless sensors | Automation.com

Energy Harvesters reduce wiring and battery costs for wireless sensors

Energy Harvesters reduce wiring and battery costs for wireless sensors

Roy Freeland, President , Perpetuum Ltd

“8 man weeks of wire pulling plus 2 man weeks of sick pay plus 1 month of plant downtime.” That was the estimate of the resource required to hard wire sensors on six machines for Health Condition Monitoring.  Doing the installation wirelessly powered by vibration Energy Harvesters took just 40 minutes. This installation was initially done with magnetic mounts. Subsequently the installation was made permanent with adhesive mounted plates

Our experiences of installation of harvesters to power  WSNs in a wide variety of process plant including Oil Refineries, Gas Plants, Petrochem facilities, Water Utilities and Power Generating Stations  have all confirmed the speed and ease of wireless installation and the surprising (to some people) ease with which the system starts to operate.
 
Installation and Maintenance Costs
According to the market research firm ARC Advisory Group, the cost of installing a wireless network is roughly 10% that of a hard-wired design. And new networks can be up and running in as little as a few hours.

The problem is that wireless means not only the data transmission but also the power supply needs to be wireless to get these benefits. However, it is no good saving on installation cost and time if the maintenance costs are excessive. Replacing batteries has significant implications for plant maintenance and reliability management:-adds to costs and time together with the related issues of reliability, hazardous zone area

Update and Reporting Rates
Battery powered units may have reasonable life between replacements but if there is a requirement to increase reporting rate, for example when monitoring the vibration of machinery that is starting to exhibit problems, then battery life may quickly fall to an unacceptably short time . Vibration Energy Harvester powered units can be programmed to report as frequently as there is energy available.

Ideal solution is “Fit and Forget”
 How do you get all the benefits of installing a Wireless Sensor system? The solution is to use Energy Harvesters. These are capable of providing sufficient power for Wireless Sensor Nodes while machinery is running. Small, highly reliable electromechanical devices pick up the vibrations from motors, pumps, compressors and other vibrating machines. Even a smooth running motor will normally enable at least 1mW to be generated. Indeed plant surveys have shown that a high power output Vibration Energy Harvester can generate more than 1mW from over 90% of machinery in process plant.
 
Why generate mW in a Giga Watt Power Station?
It seems ironic that Vibration Energy Harvesters should be mounted on machines in a power station producing a 100MW of power. But it does make economic success.. The installation is much cheaper faster and less disruptive. There is no need to transform the voltage down, shut the plant whilst making the connections and running wires. You end up with a monitoring solution that requires no maintenance such as replacing batteries or checking wiring connections.

Ease of Installation
Vibration Energy Harvesters normally come in pre-designated frequencies. For example in the USA, devices are available with frequencies centred on 30, 60 and 120Hz. This is because the vibration from an induction or synchronous motor tends to have a suitable magnitude at either exactly twice line frequency or a harmonic of rotational speed which is a multiple or fraction of line frequency less the slip %. To select which harvester to use and where on a particular piece of machinery, it is possible to try out a number of harvesters in different locations on the machine using a multimeter to check the output power. A better solution is to use a simple tool that now exists and can be placed on the machine with a magnetic mount. In a few seconds, LEDs illuminate to advise the optimum selection of frequency and several locations on a machine can be tried very quickly.

Conclusion
Energy Harvesters are now readily available to power most low power wireless installations.  They enable the end user to reap the cost benefits of both much lower installation with no wiring and also no maintenance either replacing batteries or doing routine wiring checks.
 

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