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ENERGY HARVESTING JOURNALEnerPak from TPL Inc is a sophisticated power management and energy storage system for energy harvesting-powered wireless sensors that have moderate power needs due to high data rate, the need to support a mesh network topology, or complex data measurement requirements. It features dynamic peak power tracking, a broad operating temperature range (-20°C to 60°C), and a broad dynamic range of delivered power (from microWatts to hundreds of milliWatts). It accommodates the low, variable and intermittent nature of energy harvesting sources, while providing reliable, regulated power necessary for critical sensing applications. Built around an ultra-low power microcontroller, EnerPak can consume as little as 5-8µA, enabling efficient use of the harvested energy for the application load. The system uses low impedance supercapacitors at the output to enable efficient delivery of high power burst loads while a lithium-polymer battery provides back-up in the event of a failure of the ambient energy.
Nominally designed for use in low-power wireless sensor applications (e.g., ZigBee, Wireless HART, ISA SP100, etc.) the EnerPak can be customized for almost any user-specified profile. It is also compatible with multiple different energy harvester devices (e.g., thermoelectric, photovoltaic, vibration) as the application demands. Currently two systems are available: the power management electronics and energy storage system that can be used with a harvester of the user's choice (EnerPak PM-1), or a module with an integrated 1" x 2" photovoltaic (PV) array (EnerPak SC-1). The EnerPak is available either as an enclosed system with a total packaged volume comparable to that of a standard D cell or, for integration with a customer's sensor module, the control electronics are available as a stand-alone board.
We asked Charles Lakeman, Vice President of the Micropower Division of TPL Inc.how he saw the business evolving and he replied as follows:
"Our business focuses on industrial users of wireless sensors. Based on our analysis we anticipate the global market for energy-harvesting as a power source for these sensors could reach several hundred million dollars with oil & gas, utilities, water, and equipment monitoring being the main users. We are targeting users who need more than pressure and temperature measurements for which battery powered sensors that are available and being installed today have a lifetime that is acceptable to users. I hope you understand if I am unable to disclose our specific business projections at this time. As for the number of nodes involved, I don't know if my crystal ball is better than anyone else's, but the adoption of energy harvesting is in its infancy, and will accelerate once users learn to trust it. Five years ago, users were very skeptical of wireless sensing - probably for good reason. Recently, however, networks of 1000s of sensors are being deployed - up from 10 to 100-sensor pilots a few years ago. Jeff Becker, Honeywell Process Solutions' global wireless business director, commented that "buying trends support this tendency: historically initial purchases of wireless sensors were relatively small - five motes per project, for example. But over the last four years or so, the average number of transmitters purchased at these same sites has steadily increased. ... In other words, most companies start small and expand their plants' wireless systems." (Chemical Engineering, November 2007, p. 34). I expect energy harvesting to follow a similar trajectory; when or whether, global deployments of billions of units will be reached, I can't say. Particular harvesting technologies used in these applications will, of course, include solar, but also vibration (piezoelectric, electrostatic and electromagnetic) and waste heat (thermoelectric). We are building strategic relationships will suppliers of these technologies."
He believes that he preeminent market opportunity for harvested energy lies with wireless sensors. Combining sensors that can detect changes in the environment with low power microcontrollers and radios, wireless sensors are being deployed in a variety of applications. While commonly available batteries suffice for some applications, there is a large and growing market where access to sensor nodes may be limited, dangerous or costly and routine maintenance to replace exhausted batteries will be impossible. This is the driving force for adoption of harvested energy, he argues.
He notes that much of the effort in energy harvesting design has been framed by the development of ultra-low power microcontrollers and advanced wireless communications technologies, producing a wealth of devices that can provide energy for measuring, processing and communicating small packets of data (such as temperature or pressure). "Collecting, processing and (above all) communicating data consume energy - and the more collecting, processing or communicating that takes place, the more energy is required."
