Energy harvesting for IoT devices takes advantage of energy all around us – from the sun and wind to flowing water. These natural sources can be used to power devices. In the world of Internet of Things, they’re especially valuable for running ultra-low-power products. Using this otherwise untapped energy supports sustainability and aligns directly with the UN Sustainable Development Goals.This approach also enables the development of battery-free IoT devices, which reduce waste and simplify long-term maintenance.
SDG 7 is about making clean, dependable energy accessible to all, while SDG 12 focuses on using resources more responsibly and improving overall energy efficiency both directly supporting modern IoT solutions.
So how does this connect to energy harvesting? It’s a perfect example of using natural resources to power devices while reducing energy waste. It also strengthens ESG strategies by enabling the creation of more environmentally friendly products.
What is energy harvesting?
Energy harvesting is the process of obtaining very small amounts of energy from the environment surrounding a device. The power of energy sources used during harvesting can sometimes be expressed in microwatts. The most commonly used sources in energy harvesting are sunlight, thermal energy/temperature, motion/vibration, and radio waves. Apart from solar energy, the sources mentioned above do not provide high power, but they are often available throughout the entire operating time of the device, or their availability is predictable.
Such low power levels place very stringent requirements on the designer in terms of the energy consumption of the device. These minimal amounts of energy make energy harvesting for IoT applications very demanding on the designer. The device needs ultra-low-power components, and their control must be tuned to match the energy available from the environment.
Advantages of energy harvesting for IoT
So what distinguishes energy harvesting for IoT devices from traditional solutions powered by large accumulators or lithium batteries? In this approach, we still need to store energy over time, but smaller and highly durable solid-state accumulators or supercapacitors are used instead.
Solid-state batteries have very low leakage currents, which is ideal for very low-power power supplies. Supercapacitors work well for powering radio modules because they can deliver a pulse of energy to the radio module.
Unlike lithium batteries, power supply via energy harvesting does not require maintenance throughout the product’s lifetime. This opens the door to truly maintenance-free IoT sensors that can operate for years without human intervention. With solid state batteries or supercapacitors, we do not have to worry about premature wear and tear. There is also no need for power supply infrastructure, whether cables or large solar panels. We save time and money not only when introducing the product, but also in maintaining it in the long term.
How can you harvest energy?
Below are several energy harvesting examples in IoT, showing how different natural energy sources can be used to power connected devices.
Photovoltaic
Photovoltaic cells are currently the most mature technology for harvesting energy from the environment and they offer a solid power density. With PV panels, we can power devices both outdoors and, with the right type of panel, indoors.
For outdoor devices, the available light source is sunlight, so the panel must effectively capture the full solar spectrum. Crystalline silicon (c-Si) panels are typically used for this purpose.
Indoors, the situation is different. Here, the available light usually comes from LED bulbs or fluorescent lamps, which provide lower intensity and a narrower spectrum, lacking UV and infrared components. In these conditions, GaInP cells and modern perovskite-based solutions perform particularly well.
Thermal energy
Another valuable option is thermal energy harvesting, which relies on the Seebeck effect. This phenomenon uses the temperature difference between a heat source and its surroundings to generate a voltage across semiconductor layers. Such systems are commonly applied in industrial environments where heat is abundant and continuously available.
For a Thermoelectric Generator (TEG) to operate effectively and deliver sufficient power, maintaining a significant temperature gradient is crucial. It’s not only the source temperature that matters; efficient heat dissipation to the environment is equally important to sustain that difference.
For example, air convection works on heating pipes but not in wearables, where heat flow and cooling are restricted.
Flow Energy
The energy of flow, e.g., wind or water, is a classic source of renewable energy, which is often associated with much higher power generation than energy harvesting would require. The trick in this solution is to miniaturize the turbine, whether wind or water, as much as possible. Energy harvesting based on flow energy can be used in subway or road tunnels where air movement is low and often episodic. In the case of water, this solution can be used in water pipes to power smart water meters or other water sensors.
Kinetic Energy
A more specialised energy source is vibration from roads, railways, bridges, and viaducts. It’s usually a last resort because it generates little power and requires matching the generator to the vibration frequency. It is a last resort because it works when there is no heat, light, or other energy sources in the environment. In the context of smart cities, vibrations are usually low frequency, for which electromagnetic generators are a suitable solution.
Why use energy harvesting?
Designing energy harvesting for IoT devices is a big challenge in itself and often requires expert embedded systems engineering and specialised IoT development services.While the initial design effort may be higher, these costs are offset over the product’s lifetime. An energy-harvesting device can operate for years without human intervention, making it ideal for long-lifecycle IoT deployments where replacing batteries is impractical or impossible. This not only lowers operational expenses but also enables installation in locations that are difficult or even impossible to access.
In many environments, reaching a device requires halting another system, such as a production machine. By eliminating the need for maintenance, we avoid costly downtime. This also allows the device to be embedded directly into concrete structures, installed deep inside building elements, or mounted on rotating components thanks to its reduced size and weight compared to battery-powered alternatives.
As a member of EnOcean Alliance we developed an embedded framework for EnOcean microcontrollers, built for STM32 and nRF platforms. It delivers a clean, production-ready structure with CMake and Kconfig, alongside a full suite of peripheral drivers. The result: faster development cycles and more reliable EnOcean-powered devices.
Disadvantages of energy harvesting devices
Energy harvesting for IoT offers clear advantages, but it also comes with limitations that need to be considered when selecting this technology.
Environmental energy sources can be unpredictable. The most obvious example is solar power, which depends on weather conditions. In some cases, however, the behaviour of the source is more stable for instance, heat or vibrations generated by industrial machinery making it easier to anticipate when the device will operate and when it won’t.
Difficulties arise when the application requires on-demand operation, low latency, or a strict activity schedule. In such scenarios, energy harvesting may not be the optimal choice.
Energy harvesting devices rely on buffers to store the energy they collect. Because these sources typically provide very low power, filling the buffer often takes time, resulting in a low duty cycle. In practice, this means such devices cannot transmit measurements in real time, and sending large amounts of data becomes challenging.
While working with the EnOcean Alliance, we addressed one of these challenges by implementing the first official OTA update mechanism for energy-constrained EnOcean devices. It enables remote firmware distribution even to units deployed in hard-to-reach locations. The system leverages short EnOcean frames and highly efficient data fragmentation to minimise energy consumption during updates.
Conclusion
Energy harvesting for IoT is no longer something from the future, it’s becoming a necessary part of building sustainable IoT systems. Yes, it adds some design challenges, like managing limited power and irregular energy availability. But the benefits are big: no battery maintenance, reliable operation even in tough environments, and a smaller impact on the planet. Together, these advantages make it a strong choice for many projects. It also directly supports global sustainability goals, aligning with SDG 7 by promoting access to clean, modern energy sources and SDG 12 through more responsible resource use and reduced electronic waste.
As new materials and ultra-low-power electronics keep improving, battery-free IoT devices are becoming real, not theoretical. Energy harvesting is key to building self-powered IoT devices that run independently using light, heat, or motion. For teams designing or managing systems, the question is no longer whether to use energy harvesting, it’s which type will work best for their environment and help build a more sustainable, self-powered future. If you’re exploring how energy harvesting could enhance your next IoT project, we’re always happy to share our experience.
