While the harvesters are obviously the heroes of energy harvesting technology, the importance of efficient power management should not be taken for granted. Power management components are responsible for converting the highest amount of energy possible from the harvester to into usable electricity to power the device and for storage.
Analog Devices manufactures several power management units (PMUs) for use in energy harvesting technology. On the exhibition floor, they demonstrated an energy harvesting solution for powering IoT sensors: a photovoltaic (light) harvester (manufactured by Alta Devices) connected to their one of their new proprietary PMUs to power a sensor development kit. In a second demonstration, when connected to another of Analog’s PMUs (ADP5091), the photovoltaic harvester was measured as producing around 400 mW of power under indoor lighting conditions, showing the potential for ambient light energy to supply energy to low-power electronics.
As mentioned above, efficient energy harvesting performance heavily relies on the components of the power management units that convert and regulate captured energy, not just the harvester. Linear Technology is supporting energy harvesting applications with a wide range of power management products for high efficiency conversion of vibrational, solar, and thermal energy. Their catalog boasts over a dozen ultra-low power Energy Harvesting ICs that extend the run time of the primary battery by automatically managing ambient and battery energy. These solutions find practical application in a number of areas, including building management, industrial automation, automotive, and wireless sensor nodes.
Figure 12. Linear Technology’s Energy Harvesting IC (LTC3330), converts and regulates power from a photovoltaic (solar) harvester.
Figure 13. When the harvester is inactivated (covered with paper in bottom photo), the IC automatically switches to battery power. It is the efficient conversion and switching of power that result in extended primary battery life using components from Linear Technology.
Spotlight on an Industry Leader
With millions of units already in deployment, EnOcean is enabling smart technology within homes and buildings around the globe with their battery-less wireless sensors and switches. Their solutions are completely self-powered through harvesting ambient energy in the form of temperature gradients, motion, or light. The brilliance of the technology lay within the sensors being powered by the energy signatures they are designed to sense. For example, a light sensor is powered by solar cells and sends a wireless signal about whether a window is open or closed. Or a water pressure sensor is activated when water contacts a swelling material (kinetic motion) in the bottom of the sensor, enabling a signal to be sent to a control system to turn off the water to save from damage. As well, an EnOcean-enabled heat valve is powered by the temperature difference in its own radiator. Another application includes pressure sensors powered by compression from car weight for parking management.
These sensors signal huge cost saving potential when used for energy/resource automation and control in buildings and homes. They can maximize temperature controls for comfort or turn off lights or devices in areas not being used. The technology has added value in piece of mind. Knowing that a CO2 sensor will not run out of battery, or knowing that controls will be activated to prevent damage, such as in a water leak. But it can also be used for piece of mind for our loved ones. For example, pressure sensors could monitor whether someone got out of bed or was laying on the floor, supplying information about the health and activities of elderly family remotely.
Besides power, one of the biggest hang-ups in IoT development is communication, different devices using different radio standards (language of communication). This prevents devices from different manufacturers from ‘talking’ to each other and sharing information or enacting controls. This is highly undesirable in a smart environment situation where all devices need to be able to connect and communicate with one another, or to a centralized system. EnOcean has opened up their device protocols to work with any wireless radio standard, including BLE and the EnOcean standard, allowing for their sensors to be used in a wide variety IoT systems. This has been hailed as one of the biggest developments in energy harvesting technology this past year. Additionally, the EnOcean Alliance and ROHM have been working together to establish an open, global specification for energy harvesting wireless communication. This would support the needed standardization to make self-powered IoT devices and systems interoperable. A list of next-generation wireless energy harvesting modules can be found here: http://www.rohm.com/web/global/enocean#edk400j
As you can see, there is great diversity in design and function of energy harvesting technology. However, different harvesting inventions are united in representing the benefits of energy harvesting technology: lower cost, less material waste, and more eco-friendly and sustainable.
In addition, these technologies are going to be powering microelectronics in our homes, buildings, cars, and in our wearable devices, enabling the technology that is going to truly enhance our personal and environmental well-being.
Energy harvesting technologies have come a long way in design and efficiency, with many technologies adopting small, flexible, thin-film form factors. Coupled with lower power demands for many devices, it may be that energy harvesting technology is just beginning to peek out from beyond many of the hurdles that it faced before. As further gains continue to be made, a future where our lives are powered free energy that already exists around us is closer than ever.