Dr. Maurizio Di Paolo Emilio has recently published a new book entitled, “Microelectronic Circuit Design for Energy Harvesting Systems.” John Koon, Editor-in-Chief of RTC Magazine has a dialog with the author to learn more about energy harvesting and its future.
- RTC: You have written a book entitled, “Microelectronic Circuit Design for Energy Harvesting Systems”, what motivated you to write such a book and what the book is all about?
We all live in a solar system with an enormous amount of energy sent to the earth; in addition, the earth is a living organism, or an accumulator and generator for various types of known and unknown energies. The question is legitimate: is it possible to “catch” this enormous energy and make it available to users? Scientifically speaking, yes, it is possible; the thing is possible.
Today’s technology world is evolving and bringing the most innovative products that have ever come to the market: IoT and Industry 4.0 are for example important themes of this period. The significant challenges that most electronic devices have to face are the problem of the outline dimension and power consumption. In this way, the economic and environmental impact of energy harvesting could be enormous. It provides a very small amount of power for low-energy devices, from environmental external sources as electromagnetic field, cosmic rays, kinetic, thermal and solar energy.
The book presents various theoretical aspects of energy harvesting with a focus on the design of new microelectronic circuit, broadband energy conversion, new method of conversion, future technologies and discusses the design of power management and the implementation of voltage regulators.
- RTC: What is energy harvesting?
Energy can be defined as the capacity for doing work, “work” is something resulting from the action of a force such as that of gravity. In nature, there are different types of energy: the most classic case is solar energy. An energy harvesting system captures the environmental energy and converts it into electricity to supply low power devices.
The only energy harvesting is obviously still not enough to be able to generate considerable amounts of energy in an active mode; so it must be provided a power management mode as well as storage solutions in order to ensure the proper functioning of a device. In all this, super capacitors and thin-film batteries are emerging in the market to accumulate the energy collection and further improve the efficiency and the size of the system.
The match perfect between Energy Harvesting and Power Management could be the winning choice for obtaining clean energy and at the same time limit the energy consumption by efficiently the energy storage devices, in order to meet the energy demand at times when no energy collects.
- RTC: What are some of the means of energy harvesting today?
The technological breakthrough IoT is to exploit the potential of the network to obtain a series of nodes interconnected in order to add additional operating functions; we think of a set of wireless sensors (WSN) connected in the network to provide environmental data accessible by the browser / cloud to a pre-analysis. The added value is a better control thereby allowing a firm comfort, greater energy efficiency, reduction of costs etc., adding intelligence to existing devices and the resulting diffusion of new devices in the surrounding environment.
Power management is a fundamental requirement for IoT: mobile devices obviously require batteries, but the possibility of replacing them completely or restrict the replacement / charging is a factor of considerable importance given the advent of further devices connected in the near future.
There are many techniques about this field: for example, to capture the energy lost or dissipated as heat, light, sound, vibration, or movement, then using special electronic circuits to manage the collection energy and then transform it into electrical signal.
Renewable energy can encompass all that energy derived from natural sources, such as sun and wind, but also geothermal heat and so on, so that all this can help reduce CO2 emissions and make a significant positive environmental impact. The objective of the Energy harvesting is to capture not only these but also other energies contained in human behavior such as vibration, thermal gradient and a whole range of energies that are dispersed into the environment.
The vibrations are the energy source for mechanical transducers and are characterized by two parameters: acceleration and frequency. The most commonly used are the kinetic energy understood as rotation or vibration; solar energy; electromagnetic radiation of the various wireless routers and mobile devices in the environment; Thermal is exploiting the variation of temperature, and then the Seebeck effect. The Human Walking, for example, is one of the activities that have more energy associated for the production of electrical signals.
The RF energy is currently used in a myriad of devices, we think of mobile phones or better smartphone, base stations, television antennas, routers, Wi-Fi etc. The ability to collect this type of energy could allow charging and the power supply of low-power devices while avoiding the use of batteries. The RF energy is a very topical issue especially in wireless charging with the transmission of radio frequency energy in the field of mobile devices.
- RTC: What are the considerations in designing an energy harvesting?
An energy harvesting system can be described by the following items:
- Energy transducer used to convert ambient energy into electrical energy of input.
- Rectifier and super capacitor: a rectifier and an optional storage system for energy management.
- dc-dc voltage regulator: a controller system for adapting the voltage level to the requirements of the powered device.
- Optional energy storage element: depending on the requirements of application, it is possible to use a battery as an energy storage element. For some systems, it can be activated at intervals of time, in others it is powered (or recharged) permanently.
- Load: the impedance of the system to power. It may have different ways of energy consumption making the whole system work in low-power mode. A typical electronic load is constituted by a sensor, a microcontroller, and a wireless transceiver.
The power conditioning circuits play an essential role in an energy harvesting system through various parameters such as the input impedance, power control and filtering.
The challenge is always to optimize the energy and the associated conditioning circuits to cope with a system where the correspondence of the power profiles and operation dynamics hours is in some way optimized.
Achieving a long battery life with energy harvesting techniques, in addition to representing an interesting application solution, it poses serious design problems. The DC / DC ultra-low power converters help to solve some design challenges, allowing performance of high yield peak, with a minimum of energy consumption in operational and standby modes.
- RTC: What is the future of energy harvesting?
The physical aspects that come into play in an energy-harvesting system can be described in terms of ability to store the energy, materials science, microelectronics for power management and systems engineering. All electronic systems such as computers and smartphones waste energy: why not charge your phone by using its electromagnetic waves that we know to be of greater intensity during calls and receiving data? Still, why not detect the energy that the universe sends to us? Such as cosmic rays for the realization of a low-power system to supply wearable systems.
The current trend for a better ecosystem will benefit the long-term market growth, representing in the fact that the power of the future solution for all low-power devices, beginning with the smartphone via the wearable electronics.
However, it is expected that the collection of energy will play an important role in future microelectronic devices. It will be possible to increase the energy generated using the new design of transducers or new materials as well as innovative conditioning circuits. Moreover, the electronic technology will continue its evolution to decrease the energy consumption due to the continuous downsizing of devices, with nanotechnology and, finally, with molecular electronics.
All solutions will be allowed thanks to microelectronics, which is always directed towards more solutions with low power consumption. The radio frequency transmissions also come mainly from wireless networks, and how our hunger for information and the desire to be always connected, the amount of data we want to convey is increasing exponentially, representing, in fact, a considerable advantage for the ‘ energy harvesting. The first solution is to combine a number of energy techniques to make available enough energy to power the device. The heat is one of the most abundant sources of energy that can be converted into electricity by reducing the need for wiring with a considerable saving of weight and cost. The harvesting systems that use the “wasted” heat to open new avenues to create micro-thermal generators. An increase in demand for more sustainable energy and advances in energy harvesting technology, improves the chances of seeing in the near future collection of thermal energy, RF and other modes in a wide range of new applications.
About the Author:
Maurizio Di Paolo Emilio has a Ph.D. degree in Physics and is a telecommunication engineer. He has worked on various international projects in the field of gravitational waves research. Working as a software/hardware developer in the data acquisition system, he participated in the designer of the thermal compensation system (TCS) for the optical system used in the Virgo Experiment (an experiment for detection of the gravitational waves). Additionally, Dr. Di Paolo Emilio has authored many technical and scientific papers and books relating to electronic design, X-ray, PCB, IT and embedded systems.