Today, more and more devices are connected to each other via radio with the help of intelligent sensors. But this growing “Internet of Things” is consuming more and more power. In the Fraunhofer lead project ZEPOWEL, hardware was therefore developed that makes the sensors not only energy-efficient, but downright energy savers.
Whether it’s protecting your home from burglars or keeping an eye on the machines in a factory, sensors for monitoring and control are on the rise: Sensors that report when a window is suddenly opened, or those that register that a machine is idling and wasting energy. With the help of a micro-controller, the tiny devices analyze the situation and then signal and receive instructions via a radio unit. In view of the growing number of these devices, the so-called sensor nodes, experts have been talking for some years now about the Internet of Things (IoT) — about many millions of devices in the future in the home or in industry that are connected to each other via the Internet.
An energy demand like the whole of Germany
However, these many sensor nodes still consume large amounts of energy themselves. In 2013, the energy consumption of all networked devices worldwide was already equivalent to the total electrical energy requirements of the whole of Germany, according to a study by the International Energy Agency in Paris. For this reason, eight Fraunhofer Institutes joined forces some time ago in the Fraunhofer lead project ZEPOWEL (see box) to develop particularly energy-efficient sensor nodes. In the course of this year, two solutions will be presented that approach the challenge from two different angles: The first is a self-sufficient sensor node that supplies itself with energy and collects environmental data — on air quality, for example. And secondly, a sensor node that detects the operating status of machines, motors or pumps in order to drastically reduce their energy requirements.
“The sensor node hardware we developed in the project is characterized by the fact that it can be built up modularly from different components and can thus be adapted to different purposes,” says Erik Jung, project staff member at the Fraunhofer Institute for Reliability and Microintegration IZM, which combined the individual developments from the participating institutes into a functional whole. “Some partners contributed their knowledge about building efficient chips and control electronics, others about building small and efficient batteries and energy converters. Others have contributed with their expertise in secure wireless protocols.”
Autonomous sensor for the smart city
The energy-autonomous sensor node, the “smart city node”, is characterized by the fact that it falls into a very energy-saving deep sleep mode when it is not needed. In this state, it consumes only a few nanowatts. Only when it is activated via radio does it start up — for example to measure fine dust and send the measured values via radio. The smart city node will be installed on cars and buses in the coming months. It uses an energy converter to generate electricity from vibrations while driving. “The nodes are tiny, maintenance-free and inexpensive and can be used in many places — giving you a very fine-meshed measurement network,” says Erik Jung. In the future, such sensors could also be used in agriculture to measure soil moisture and nutrient content very precisely at specific points, so that farmers can irrigate and fertilize in a more targeted manner. This sensor-based “precision farming” is on the rise, says Jung.
Teaching machines to save energy
The second type of sensor node will be used in machines with rotating motors, initially in machine tools provided by an industrial partner. Even today, there are many machines that are started and stopped by hand. Once a job is completed, they continue to spin at idle until you press the button. In addition to the measurement technology, the new sensor node now contains innovative power electronics for controlling 15 kW at switching voltages of up to 850 V. It is coupled to the machine and can now ramp the machine up and down as required or control it to the respective required speed. “There are still many machines in industry today that are not speed-controlled,” says Erik Jung. Replacing them with new machines would be enormously expensive. It therefore makes sense to equip them with the intelligent sensor node instead. “Roughly estimated, we would save around 20 percent of carbon dioxide emissions nationwide if intelligent sensors with integrated control were used across the board in industry,” says Erik Jung. The lead project ZEPOWEL has now delivered a corresponding standard.