Microwave Tech - Energy harvesting technology helps power IoT devices

For a long time, the huge market formed by the Internet of Things and the huge number of billions of devices have gradually become known to people. At the same time, mobile IoT devices are becoming more and more, and wired power is not a long-term solution. As the Internet of Things market continues to grow vigorously, the energy supply method and battery issues of equipment are becoming new challenges.

Imagine that we have 1 billion IoT devices, and each device has a battery life of 3 years. This means that on average, nearly 1 million batteries need to be replaced every day, which brings cost pressure, environmental hazards and many other problems. So is there any new energy supply method that can alleviate this phenomenon?

Where there is light, there is energy, and photovoltaic energy (solar energy) is being widely used. At the same time, many photovoltaic technologies continue to make progress, such as large-scale solar photovoltaic panels, and small photovoltaic cells used in products such as calculators.

In addition, organic solar cell technology is also expected to be commercially available in the future, providing equivalent or even better performance. Some new materials also have features such as flexible substrates and customizable shapes, and can be customized and printed on flexible plastics or other materials to add new photovoltaic modules to existing industrial designs.

The amount of energy collected by solar energy is related to various factors such as light intensity and photovoltaic materials. Different technologies have different energy values collected from a unit area under different light levels, and the prices of materials are also different. Therefore, the collection of photovoltaic energy needs to consider the light environment, available area, and budget constraints.

A small calculator is an electronic product that people are very familiar with, but what is less known is that as early as 100 years ago, the "calculator" at that time-the adding machine, had begun to rely on mechanical energy harvesting to operate.

In mechanical energy collection, we use mechanical motion to move the magnetic poles in the coil to form an energy burst, and then capture this energy for wireless transmission. With the help of the mechanism of collecting and releasing energy through exercise, we can make the energy be used with production, rather than stored in the battery.

However, mechanical energy harvesting must have corresponding collection elements. An element often needs to be 3 square centimeters in size, and the height can be less than 1 cm. How to integrate components to meet the energy requirements of the equipment, this is what we need to fully consider.

Thermal energy harvesting may be a technology that people are not familiar with. In thermoelectric devices, when different temperatures are placed side by side, voltage is generated accordingly. Using the voltage converted from this temperature difference, we can realize the collection of heat energy.

Specifically in the thermoelectric generator, we heat one end of the generator while keeping the other end at a low temperature, so that a potential difference appears in the circuit; and then use a booster circuit to increase the voltage to meet the operating requirements of the integrated circuit. Based on this principle, Atmosic and a company have cooperated to develop and develop a thermal energy collection watch, which can fully support basic watch functions independently by collecting the heat of the wrist.

It should be noted that in heat energy collection, we not only need a heat source, but also a radiator to create a temperature difference. Because heat must continue to flow in the equipment to produce a continuous source of current and energy.

For a radio frequency source with a 100% duty cycle, the maximum theoretical power that can be obtained decreases rapidly as the moving distance increases. When the moving distance exceeds one meter, in the case of 2.4 GHz, even the available raw energy is less than 100 microwatts. In addition, the efficiency of the collector and storage must be considered. When the frequency band is switched to 915 MHz, the device can obtain a higher level of power harvesting, and can collect energy two or three meters, or even five or six meters away.

Different from other energy harvesting methods, radio frequency energy harvesting also needs to consider the communication regulations of various regions, including available frequency, maximum output power, etc. These restrictions actually affect the amount of energy that can be collected. For example, the restrictions in Europe are stricter than those in North America and Japan, so that they can usually only get 10db lower energy than usual.

As a global innovator of ultra-low-power Internet of Things (IoT) wireless technology, Atmosic has developed three innovative technologies: ultra-low-power radio frequency, radio frequency wake-up, and controlled energy harvesting to achieve the lowest power consumption and completely reduce IoT applications Reliance on batteries. For example, we can apply radio frequency wake-up technology in a security tag so that it will only activate when it is close to the card reader. Wake up through radio frequency identification can also allow the device to operate only when energy harvesting is needed; or rely on putting the device into a special box or close to the signal source to charge the device when it is not running.

Of course, energy harvesting is not an "all or nothing" technical route. We can still combine battery technology with energy harvesting technology, use the collected energy first through the power management unit, continue to optimize energy consumption, and greatly extend the life of the battery; it is also possible to use only the collected energy in some cases, Completely get rid of the dependence on the battery.

Atmosic has designed an ultra-low power Bluetooth 5.0 chip that focuses on energy harvesting applications. It has many features that help reduce energy consumption, such as an independent and flexible wake-up receiver, which allows the chip to wake up only when it receives a specific RF signal, thereby Maintain low energy consumption; and integrated power management unit, which can collect and manage multiple energy inputs, and even realize the "permanent" use of the battery under certain conditions.

Finally, the controlled energy harvesting technology provided by Atmosic provides a variety of solutions to the battery and cost issues of the Internet of Things and other devices. There are many types of energy harvesting technologies available, but they are not a panacea. We still need to have a deep understanding of the environment and specific applications in which we are in, combined with the dimensions of budget and goals, and choose the most suitable solution according to the conditions.