Bosch Software Innovations

Energy harvesting for the internet of things Electricity out of (apparently) thin air Wireless sensors draw power from the environment

  • Billions of tiny sensors need power
  • Unusual sources: body heat, vibrations, pressure
  • Maintenance-free over long periods
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  • February 06, 2014
  • Bosch Software Innovations
  • Press releases

press release

    The billions of mobile sensors needed for the internet of things
    cannot be wired up. And changing batteries is too much trouble.
    One solution is for the devices to harvest the energy they need from
    their environment - with effectively no need for maintenance.

Stuttgart/Berlin – Anyone installing a network of wireless sensors needs to provide them with power. In the protected environment of a factory or a home, this is an easy enough task. But what if almost every object is fitted with sensors for the internet of things, including in places where there are no power lines? In that case, the energy can perhaps be drawn from pressure differentials, vibrations, or temperature gradients in the environment. Bosch, too, is researching this kind of energy harvesting and how it might be applied, for example in the framework of 9D-Sense, a publicly funded joint project on which Bosch is working with ten further partners.

Free of failure-prone cabling
Many of the billions of new entities on the internet of things will be low-cost sensors that collect data about their surroundings and then send it to a nearby router using standardized radio technology. To keep it as simple as possible to install the sensors, they need to be free of elaborate, failure-prone cabling. But for a network comprising hundreds or thousands of sensors in a given area, it would be a herculean task to change all those batteries – both time-consuming and far too expensive. Plus each sensor’s battery compartment would have to be waterproofed; a maintenance-free housing would be much less trouble.

Sensors, supply yourselves
From all of the above we can derive an ideal profile of requirements: battery-free wireless sensors that supply their own power as much as possible. And there are several effects known to physics that they might harness – but since not all of these sources of energy are present in every location, the most suitable one has to be selected in each case. A tiny rechargeable battery can store the minuscule amounts of energy gathered. Meanwhile, clever programming ensures the sensors only transmit their data when absolutely necessary – which saves power.

Photoelectric effect
When photons from high-energy radiation strike a suitable metal or semiconductor plate, they alter the energy state of the electrons in the material, thereby producing a voltage. This is the principle on which solar cells are based. And tiny solar cells can provide tiny sensors with electricity – as long as there is light.

Thermoelectric effect
Current can be generated by differences in temperature. In a circuit composed of two different metals, a voltage is produced if the metals are at different temperatures. This effect can be used to build small thermoelectric generators, for instance as an arm band where the side facing the skin is warm and the other side cool.

Piezoelectric effect
Certain materials display the piezoelectric effect, whereby a voltage is produced when pressure is applied. The effect is a result of the movement of electric charges within the material. And the inverse piezoelectric effect dictates that materials can be deformed by applying a voltage to them. Both effects already have a wide range of technical applications. Industrially produced piezo elements are usually made of ceramics and can for instance convert vibrations into small currents.

Vibration converters
Many machine parts vibrate during operation, and this can be harnessed by building a vibration converter that uses an oscillating or vibrating machine part to move a permanent magnet back and forth within a coil and induce a (usually small) voltage.

Rotation converters
These are based on the dynamo principle, whereby a rotating bicycle dynamo produces a voltage. Many technical devices also have rotating parts, and if these are fitted with miniaturized dynamos they can supply power to nearby sensors.

Practical application in the 9D-Sense project
Moving from theory to practice, Bosch is coordinating the 9D-Sense project, which is supported by Germany’s Federal Ministry of Education and Research and includes ten further university and industrial partners. As project manager Torsten Ohms from Bosch Sensortec explains, 9D-Sense is developing a small, low-cost, autonomous multi-sensor system that is supplied with power by an energy harvester.

The system has three elements. First, there is the sensor module, which measures in nine degrees of freedom (a three-axis acceleration sensor, a three-axis yaw-rate sensor, and a three-axis magnetic sensor). Next comes the power supply, consisting of a thin-film battery for intermediate storage along with a thermoelectric harvester and a vibration harvester. Finally, there is the secure wireless data connection along with the necessary algorithms and interfaces.

Various possible applications of this technology are currently being explored. One of them is “smart wristlets,” arm bands that record their wearer’s movements; the partner company for these is Gemalto. Meanwhile, Otto Bock Healthcare Products is looking into how to power orthotics so they can help their wearers to extend joints (in this case the knee).

Navigation systems for inside buildings
Bosch is also researching how sensors can help people to find their way around inside buildings. A sensor might recognize its wearer’s movements around the building and mark the route taken on an electronic map on a smartphone or tablet, which could if requested also show the wearer how to get around in an unfamiliar but mapped area. Projects are currently underway to generate maps of buildings by gathering user data. This all works without GPS, since reception of its satellite signals is at best poor and often non-existent within buildings. When wearers are sitting down, an energy harvester takes advantage of their body heat; if they are walking around, another harvester taps into their kinetic energy. Of course, wearers can deactivate all this technology if they wish.

9D-Sense research project:
EnAs joint project on energy-autonomous sensors:

Back to overview

The Bosch Group is a leading global supplier of technology and services. It employs roughly 375,000 associates worldwide (as of December 31, 2015). The company generated sales of 70.6 billion euros in 2015. Its operations are divided into four business sectors: Mobility Solutions, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 440 subsidiaries and regional companies in some 60 countries. Including sales and service partners, Bosch’s global manufacturing and sales network covers some 150 countries. The basis for the company’s future growth is its innovative strength. Bosch employs 55,800 associates in research and development at 118 locations across the globe. The Bosch Group’s strategic objective is to deliver innovations for a connected life. Bosch improves quality of life worldwide with products and services that are innovative and spark enthusiasm. In short, Bosch creates technology that is “Invented for life.”

The company was set up in Stuttgart in 1886 by Robert Bosch (1861-1942) as “Workshop for Precision Mechanics and Electrical Engineering.” The special ownership structure of Robert Bosch GmbH guarantees the entrepreneurial freedom of the Bosch Group, making it possible for the company to plan over the long term and to undertake significant up-front investments in the safeguarding of its future. Ninety-two percent of the share capital of Robert Bosch GmbH is held by Robert Bosch Stiftung GmbH, a charitable foundation. The majority of voting rights are held by Robert Bosch Industrietreuhand KG, an industrial trust. The entrepreneurial ownership functions are carried out by the trust. The remaining shares are held by the Bosch family and by Robert Bosch GmbH.

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PI8451 - February 06, 2014

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