Energy harvesting, also known as power harvesting or ambient power harvesting, is the process by which energy is derived from external sources (such as solar power, thermal energy, wind energy, salinity gradients, and kinetic energy), captured and stored for small, wireless autonomous devices, like those used in wearable electronics and the Internet of Things (IoT). Rather than relying on batteries, energy harvesting devices are able to operate indefinitely as long as the energy source remains available. This makes them particularly useful for applications where it is inconvenient or uneconomical to frequently change batteries.
Energy Harvesting Systems offers a more sustainable approach to powering small devices compared to traditional batteries which ultimately end up in landfills. With the rapid growth of IoT devices, energy harvesting is playing an increasingly important role in developing maintenance-free solutions for sensors, tags and other connected objects.
Popular Energy Harvesting Technologies
Several technologies have emerged as promising methods for harvesting energy from ambient sources:
Photovoltaic Energy Harvesting
Photovoltaic cells, more commonly known as solar cells, convert light directly into electric current. They have become the most widely used energy harvesting technology thanks to their versatility and the abundance of sunlight. Solar cells can be integrated into wearable electronics, remote sensors, calculators and more. Though dependent on light levels, they provide a near-limitless source of renewal energy during the day.
Thermoelectric Energy Harvesting
Thermoelectric generators use the temperature differences between two materials to produce voltage. They operate by taking advantage of the Seebeck effect where a temperature gradient creates electrical energy. Common applications include harvesting heat from industrial processes, car engines, buildings and even the human body. Thermoelectric harvesters offer an efficient approach requiring no moving parts.
Vibration Energy Harvesting
Vibration-based energy harvesters convert kinetic energy from vibrations into electricity. They work through electromagnetic, electrostatic or piezoelectric transduction mechanisms. Common vibration sources include operating machinery, moving vehicles and foot traffic. Vibration harvesters have been integrated into bridges and building infrastructure to power wireless sensor networks. They are particularly useful for applications where periodic motion is readily available.
Radio Frequency Energy Harvesting
RF energy harvesting involves scavenging electromagnetic energy from ambient radio broadcasts like cell networks, TV signals and WiFi. Receiving antennae capture RF waves which are then rectified into direct current by voltage rectifiers. RF harvesting offers potential for powering devices anywhere signals are present without needing other energ sources. However, it relies on transmitter infrastructures and signal levels can vary significantly by location.
Challenges in Energy Harvesting System Design
While energy harvesting promises perpetual operation, there are still hurdles to overcome before it can fully replace batteries:
Variable and Intermittent Power Sources
Most ambient energy sources like sunlight and vibrations are variable and intermittent in nature. This makes power management challenging as supply fluctuates. Efficient energy storage and power management circuits are required.
Matching Harvester to Load Requirements
The power levels generated by energy harvesters do not always match the variable demand of electronic loads. Circuitry is needed to boost, regulate and condition harvested power before storage or use.
Energy Efficiency of Power Conversion
No energy harvesting or power conversion process is 100% efficient. Losses occur at each stage from capture to storage and use. Improving overall system efficiency remains an area of focus.
Miniaturization for Integration
Size is often a constraint for small IoT devices. Further miniaturization of harvesters and power electronics is needed to minimize their footprint and enable integration into various form factors.
Applications of Energy Harvesting Systems
Despite the challenges, energy harvesting solutions are already enabling critical applications:
Remote Sensors: Solar and vibration powered autonomous sensors have been deployed for environmental, infrastructure and agricultural monitoring where battery replacement is infeasible.
Medical Implants: Miniaturized harvesters harvesting motion or RF have potential to power pacemakers and other implants without replacement surgery.
Smart Labels & Shipping Containers: RFIDs are demonstrating feasibility through RF harvesting for real-time tracking of goods in transit and inventories.
Smart Cities Infrastructure: Road and rail sensors rely on vibration harvesting while solar powers displays, lighting and public amenities to reduce energy costs.
Military & Aerospace: Thermoelectric harvesting tapping engine and equipment heat and kinetic harvesting of helicopter vibrations aim to power electronics without depleting precious fuel reserves.
With further technology advancements, energy harvesting systems have the potential to solve many of the world’s remote power needs in a clean, maintenance-free fashion. Although variable power sources and inefficient energy conversion present challenges, the growth of low-power electronics and more efficient harvesting technologies will drive expanded use across IoT applications over the coming years. Energy harvesting systems promise a more sustainable approach that could one day render batteries obsolete for many small electronics.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it