In order to realize a society connected to the Internet via sensors that are embedded in various things, securing a sustainable power source that drives sensors and wireless systems has become an issue.
It is important to use natural energy such as sunlight and wind power as they are environmentally friendly and sustainable.
Microbial fuel cell, (MFC), is also called microorganism power generation, which is energy that exists in nature. It is a device that directly generates from microorganisms existing in the soil and electricity generated bacteria from organic wastewater.
This time, we developed a sensing system that combines AKM's circuit technology with this MFC as a power source.
Since this MFC can stably supply power for 24 hours as long as microorganism activity exists, infinite choices for future business from primary to tertiary industries exist.
sensingnet Inc. has been developing a Regenerative Sensing System* using the AP4470 for sustainable power sources. At the World Business Satellite broadcast of, "Trend Tamago", on TV Tokyo, July 20, 2018, the AP4470 step-up DC-DC converter was introduced in, "Sensing technology using microorganism power generation".
sensingnet Inc. web site
* Regenerative Sensing System: Circulatory systems that utilize the energy resources that can be extracted from the natural environment such as biological activity, vibration and light, in sensing technology and date transfer.
The National Agriculture and Food Research Organization, (NARO)' s, MFCs have been tested together with the AP4470 and various sensors to contribute to practical agricultural and environmental applications.
Two circuit technologies of Asahi Kasei Microdevices are applied for system development.
● Step-up circuit that is capable of driving at 0.2V
● Ultra-low current consumption voltage detection circuit with nano ampere operation
Most temperature sensors, radio circuits, and display devices require a voltage of 3V or more to function. Since the output voltage of the MFC is lower than this, a single MFC cannot drive the wireless sensor module directly. Even when MFCs are connected in series, stable operation is difficult due to nonlinearity.
In order to solve this problem, to recover energy that can be practically used from MFC, it is necessary to raise the voltage by boosting with a step-up circuit, store the energy in an accumulator, and supply the energy to a wireless sensor module by controlling the accumulated energy. However, with existing booster circuits, voltage that can be boosted and current consumption do not match the characteristics of MFC and energy cannot be efficiently recovered. Therefore, MFC has not yet been put to practical use as a power source to drive wireless sensor systems.
The AP4470, developed by Asahi Kasei Microdevices for practical application of MFC, is a step-up circuit that meets the requirements of MFC with an integrated a circuit that controls boosting power without loss of power accumulated in the storage element. By combining an MFC and the AP4470, a sensor, radio module, or display device can be driven. A system for long term measurement can now be built which was not be possible before. The data obtained by the system contributes to global environment conservation and human living improvements.
Very weak energies in the natural environment such as light, vibration, heat, and radio waves have been ignored without collection. Energy Harvesting is to make effective use of these.
However, since power consumption of the power supply circuit is larger than that of the power generation amount, there had been nothing that could be used as a system power source so far.
It will be possible to charge the electric power to a level that can drive sensor / wireless module etc. without serializing and enlarging the area of environmental power generation elements as in the past.
Realizing long time operation, (without battery exchange), multipoint placement, (wiring free), and small and low-cost battery less IoT sensor node, accelerate implementation of various sensors in our society.