Using Energy Harvesting Devices with National Instruments Wireless Sensor Networks (WSN)

1. NI Wireless Sensor Networks

The NI Wireless Sensor Network (WSN) platform simplifies remote monitoring applications and delivers a complete, customizable monitoring solution. NI WSN hardware reduces installation and maintenance costs while delivering a flexible solution that features industrial ratings and extremely low power consumption.  Because of their low power consumption, NI WSN measurement nodes are ideal for energy harvesting applications.  With operational power on the order of 300mW, WSN end nodes can operate for up to 3 years on their internal 4AA batteries, or indefinitely with the use of energy harvesting devices. 

Figure 1.  Create flexible, easy-to-use remote monitoring solutions with NI Wireless Sensor Networks

The newest member of the NI WSN family, the NI WSN-3226 Voltage/Resistance combination node, adds resistance-based measurements, such as RTDs and potentiometers, to the NI WSN platform, and represents an ideal option for performing wireless measurements powered by energy harvesting.  With this node, you can combine temperature and voltage measurements on a single device. The WSN-3226 provides four analog input channels that you can configure on a per-channel basis for ±10 V measurements or resistance-based measurements. The device also features two bidirectional digital channels with industrial voltage ranges that you can program to respond to digital value change events. The 18-position screw-terminal connector delivers direct connectivity to sensors, and the device offers a 12 V, 50 mA sensor power output that you can use to drive sensors requiring external power. You can power the measurement node with four 1.5 V, AA alkaline battery cells, with operation up to three years on battery power, or you can externally power the node with a 5 to 30 V supply, such as a solar or vibration energy harvester.

In addition, LabVIEW integration with NI Wireless Sensor Networks simplifies the extraction of high quality measurement data.  LabVIEW graphical programming delivers advanced data analysis and visualization, including web-based data access and node programming for local processing, analysis, and control using the LabVIEW WSN Module. 

View the NI WSN Product and Configuration Guide »

Configure a Wireless Monitoring System »

Summary of WSN Energy Harvesting

*Note that NI WSN products must be purchased from NI, while the energy harvesting devices can be obtained by contacting Solarcraft or Perpetuum, respectively.

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2. Solar Energy Harvesting

Solar energy harvesting has become one of the most popular forms of renewable energy.  The proliferation of solar energy harvesting has driven down installation costs and allowed more applications to benefit from the use of solar energy harvesting.  Solar power is emission and noise-free, and in most parts of the world is constantly available.  Solar harvesting solutions require little maintenance and can provide reliable, continuous power to load devices.  In applications like environmental monitoring and structural health monitoring, the usage of solar energy  harvesting allows engineers and scientists to create standalone monitoring solutions and eliminate the need for traditional line or grid power.

Using Solarcraft Solar Energy Harvesting with NI WSN Measurement Nodes

National Instruments has partnered with Solarcraft to deliver a wireless measurement system that can run completely independent of grid power. This enclosure can be used to power any WSN measurement node, including nodes operating in router mode, meaning you can extend the coverage of your WSN using solar-powered routers.

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3. Vibration Energy Harvesting

Simply stated, vibration energy harvesting is the process by which otherwise wasted vibration (from a piece of industrial machinery, for example) is harvested and converted to useful electrical energy to perpetually power wireless measurement devices such as NI WSN measurement nodes. One of the most prevailing applications for wireless sensor networks is to monitor the health and status of essential industrial machinery assets within light & heavy industrial manufacturing environments. The value of industrial WSNs is the ease and economical deployment of monitoring areas or assets that would not be economically viable to access via traditional wired monitoring solutions. These assets exist in plant, near plant and in remote locations.

Today's technology is offering the OEM and end-user world more sophisticated and viable power options for WSNs. Until recently, the only power source available to power a WSN has been batteries, but batteries alone will not provide a power source that will last the life cycle of the WSN application without maintenance intervention. With the addition of Perpetuum Vibration Energy Harvester solutions, there will be sufficient, maintenance-free power beyond the life cycle of the WSN application.

Vibration Sources

Not all vibration is equal in the world of energy harvesting. The fact that a structure or object vibrates (even at excessive levels) does not automatically make it a viable candidate as a suitable vibration source to harvest from. The source vibration must have certain characteristics for it to be usable.

The following guidelines will shed some light on how to determine if you have a suitable vibration source for optimal use:

Resonant Frequency - The source vibration object should have a known and repeatable frequency component. This provides the optimal tuning frequency for the vibration harvester to work at its maximum potential.

Vibration Level - The RMS g level of vibration will be the next consideration. Once the Vibration Energy Harvester is frequency tuned for maximum mass/spring displacement, the RMS g level of the source vibration object will determine the power output of the VEH. The usefulness of a VEH in industrial environments will be its ability to produce sufficient power at low levels of vibration.

Tuning the VEH

All vibration energy harvesters (VEH) are in essence a mass/spring mechanically tuned resonator. Their effective operation is based upon the ability of the VEH to harvest from a vibration source with a repeatable and consistent frequency and known sufficient vibration level. The vibration source frequency is used to tune the VEH to a resonant frequency (the frequency that will produce the maximum amount of displacement of the mass/spring structure enabling maximum power output of a VEH based upon source vibration level. In other words, they are factory tuned to a pre-defined resonant frequency to match the vibration source of the application and maximize the power output of the VEH. 

In the industrial world, line powered machinery are excellent vibration sources to harvest from. They will have a repeatable frequency component of 60Hz (line power frequency) or 120Hz (2X line power frequency). In non-U.S. countries the frequencies are 50Hz & 100Hz. This allows the end-user to select the optimized VEH frequency to ensure maximized power output of the VEH in the target application. 

Using Perpetuum Vibration Energy Harvesters with NI WSN Measurement Nodes

National Instruments has partnered with Perpetuum, Ltd. to deliver a VEH that can indefinitely power NI WSN end nodes (NI WSN measurement nodes acting as routers remain in constant operation and require more power than the VEH can provide).

To learn more about vibration energy harvesting and view guidelines for locating suitable vibration points on industrial motors and machinery, refer to the Resources section on the Perpetuum website.

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4. Additional Resources

Visit the NI WSN Homepage

Purchase an NI WSN Starter Kit

Purchase a Solarcraft Solar-Powered Enclosure for NI WSN Nodes

Purchase a Perpetuum Vibration Energy Harvester to power NI WSN Nodes