Eventually, every battery on Earth will require replacement, which can be costly and complicated. This is where energy harvesting devices come in. These innovative devices can store energy and use it later, eliminating the need for pricey and inconvenient battery replacements. The era of battery-free IoT devices has arrived, with applications ranging from home electronics like remote controllers to smart buildings and smart factory sensors. Silicon Labs is proud to offer a line of ‘EFR’ Energy Friendly Radios that meet the requirements for energy-harvesting devices.
What is energy harvesting?
As populations grow, economies develop, and industries and cities expand, global energy usage is soaring to new levels. Projections from the US Energy Information Administration point to global energy demand increasing by 47% in the next 30 years, driven by these very forces. To accommodate this growth sustainably and protect our planet, we’ll need to turn to more alternative, renewable resources-and IoT designers can be at the root of this change.
Energy harvesting presents a power supply alternative for embedded system designers, offering a potential solution to the global energy challenge while safeguarding our planet’s finite resources. The concept of energy harvesting started with small sensors for handheld gadgets and has now evolved into scalable solutions, allowing wireless sensors like Bluetooth to thrive in applications incompatible with standard battery designs.
For instance, an energy harvesting power supply empowers a system designer to effortlessly build an ultra-sleek wireless sensor capable of spanning over 100 meters (approximately 328.08 ft) and sustaining a life expectancy of more than 20 years. Commercially available energy harvesters can convert solar, mechanical, or thermal energy into electrical energy-with solar energy having the highest power density. So, how did we get to this immense capacity, and how can we push the potential of energy harvesting in the future?
The evolution to energy harvesting
Traditional batteries must be replaced and tend to be bulky – an inefficient design that creates substantial waste. According to the EPA, over three billion batteries are thrown away yearly, contributing to tons of hazardous waste. As a more sustainable alternative, more manufacturers are turning toward energy-storing technologies called supercapacitors and thin-film batteries to lengthen the product lifecycle and improve quality. Thin-film batteries are known for their ultra-thin profile and low leakage characteristics. They’re also becoming more cost-effective, making energy harvesting more accessible. We have now reached a technological tipping point that will result in the evolution of energy harvesting-based systems from today’s niche products, such as calculators and wristwatches, to their widespread use in building automation, security systems, embedded controls, agriculture, infrastructure monitoring, asset management, and medical monitoring systems.
Energy harvesting technologies come from multiple renewable sources, and these technologies can be used alongside thin-film batteries rather than traditional batteries that tend to use natural resources. The total lifetime capacity of thin film batteries is equivalent to four lithium “AA” batteries or a single “C” size lithium-thionyl chloride battery. Thin-film batteries are well suited for space-constrained embedded systems that require an ultra-thin profile and long battery life.
The flexibility of designing a self-sustaining embedded system through energy harvesting versus main power or conventional replaceable batteries creates new application possibilities. It opens new frontiers for embedded system development, such as the ability to further power IoT devices cost-effectively, as Silicon Labs’ Daniel Cooley explained in a recent keynote at Embedded World 2023.
Energy harvesting applications
The growth of energy harvesting technology enables wireless sensors to be used in applications previously incompatible with conventional battery-powered designs. One of the most intriguing energy harvesting applications is a battery-less kinetic-harvesting push-button switch. These devices are found in the home, smart buildings, and smart factories and only require a few hundred microjoules to operate. They use the kinetic momentum of a button push to charge super-capacitors enough to send an IoT packet to a gateway. These switches can be moved and re-commissioned for a much longer lifetime than traditional switches.
Other key applications are powering sensors found in the smart factory. Devices can harvest indoor ambient light, heat from a steam trap, and/or vibration from a motor to power a predictive maintenance sensor and communicate back to a gateway. Likewise, conventional asset tracking tags can have their lifetime extended by replacing a battery for a PV cell, RF energy harvester, supercapacitor, or printed battery. Additionally, the smart home is now seeing devices such as television remote controls, computer keyboards, and gaming mice rely on PV and RF charging to reduce the need for annoying battery replacement.
Low power consumption can be achieved by selecting components with low leakage specifications and using an ultra-low-power microcontroller (MCU) like Silicon Labs’ Si10xx wireless MCUs. Similar to how battery-powered systems can use techniques to achieve low-power operation, power consumption can be minimised in Silicon Labs’ energy harvesting systems. By understanding and optimising a device’s cold start, sleep, and wakeup consumptions, these MCUs contribute to powering IoT devices, thus expanding the range of energy-harvesting abilities.
The future of energy harvesting
As we work towards creating higher-performing MCUs and more widely available energy harvesting systems, these systems can reduce our carbon footprint and allow for more efficient battery operating systems. Providers like Silicon Labs are making energy solutions more feasible and helping reduce waste by offering alternative electricity sources. Energy harvesting could become widespread, powering homes, smart cities, security systems, industrial devices, and much more.
Tristan Cool is an Industrial IoT Product Marketing Manager at Silicon Labs, leading the company’s exploration into alternative power solutions for the IoT. He leads the Industrial Asset Monitoring Segment, covering applications such as asset tracking, machine condition monitoring, and fleet telematics.