What is Energy Harvesting?

This page is an entry in our extensive guide to Bluetooth Beacons.

What is energy harvesting?

Energy harvesting is the process of collecting energy from the environment and converting it into a usable form, such as electricity and light. Energy can be harvested from a variety of sources, including solar, wind, water, thermal energy, sound, radio waves, vibrations, and movements.

That's a lot of potential energy sources, right? And for the most part, these sources are going untapped in 2022.

Energy harvesting has the potential to change that.

Energy harvesting and IoT

Alright, but how does this relate to IoT?

For starters, IoT devices are often battery-powered. And if there's one thing we know about batteries, it's that they run out. Energy harvesting can be used to extend their operating life by reducing or eliminating the need for batteries. In certain cases, this can also make the devices smaller, cheaper and can allow us to embed them into assets rather than simply attaching them externally.

This is a huge added convenience for nearly every IoT business owner — and a complete game-changer for certain IoT use cases. To help you get a better understanding of the wide-reaching benefits of this technology, here's a breakdown of some key ways IoT can benefit from energy harvesting.

Reduced maintenance

First, energy harvesting can reduce maintenance costs as IoT devices can be designed to be self-powered and self-sufficient. This is especially beneficial for remote or hard-to-reach locations, where regular maintenance can be difficult or impossible.

That means devices can be deployed without consideration for when the battery will need to be replaced. That can go a long way towards making the process of deployment more convenient and open-ended.

Battery replacement of thousands of devices and thousands of sites can be a project killer in terms of the cost of sending a “man in a van” to each site. Beyond the cost there is a likelihood that batteries will not be replaced and devices go dark.

Maintaining battery powered IoT devices becomes a challenge as the scale increases. Replacing the batteries in all the devices at once will send some batteries that are still good to a landfill. Waiting until each battery dies will result in high operational cost and the potential for lost data.

New applications in remote or inaccessible locations

Energy harvesting is also opening up new possibilities for applications in remote or inaccessible locations, where traditional power sources are not available.

In the cases where energy is harvested from radio waves, the device can literally be embedded within plastic or cardboard. This can be more aesthetically pleasing as well as robust and durable.

Increased sustainability

Energy harvesting is a more eco-friendly alternative to traditional power sources, as it relies on renewable energy sources that are not subject to depletion.

Batteries are some of the worst things that you can dispose of in the environment. This makes disposing of them difficult and costly, even when done safely. By using energy harvesting, batteries can be removed, saving them from harming the environment.

Lower Deployment Costs

One of the most expensive things you can do to a project is require new cabling for power to be installed or retrofitted. Planning approvals, dust and disruption, building work and time from electricians can dwarf the capital expense of the IoT devices themselves adding delay, risk, environmental hazards (dust in hospitals … not good) and costs that can torpedo a project either at the start or when it comes time to scale from pilot to production.

How does energy harvesting work?

Alright, that's the basics and the benefits out of the way. But how does energy harvesting work?

The method of harvesting energy varies depending on the system at hand and the type of energy. For regenerative braking, a car's electric motor will switch to generator mode. Photons will excite the silicon inside a photovoltaic solar panel and cause a current to flow. Water cascading down a waterfall will spin a turbine. In all of these examples, energy that would normally go to waste is converted into another, usable form.

Once the energy has been converted it can be stored for future use. For electricity, the storage can be in a capacitor or a battery. Steam can be pressurized inside a tank and then released when power is needed.

For any given type of energy, a method of harvesting and storing can be developed.

The types of energy most commonly harvested

Natural or artificial light

One of the most common sources of energy for energy harvesting is natural or artificial light. Light can be converted into electricity using photovoltaic (PV) cells, which are made of materials that convert light into an electrical current.

Light is a strong source of energy but requires line of sight to a light source, which may not be available when objects are stacked around the device. The ROI can be compelling but typically there are more component costs than some other forms of energy harvesting.

Examples are electronic calculators. An application where results have been mixed is with TV remote controls, where the PV cell can be easily covered.

Vibration & Movement

Another common source of energy for energy harvesting, movement and vibrations can be collected using piezoelectric materials which convert mechanical energy into electrical energy.

Vibrations are typically a much smaller source of energy, but can be surprisingly impactful depending on where your devices are deployed. Underwater, in urban environments, in windy areas — there are plenty of locations where movement or vibrations create enough energy to power small IoT devices.

One popular use case where movement provides sufficient energy to enable IoT devices is in light switches, which use the energy harvesting from depressing the switch to power radio communication to indicate that the switch has been pressed. This can mitigate the need to run wiring to the switch and can allow the switch to be placed at a place where it is most convenient even if wiring isn’t available.

Thermal power

Thermal power can be collected using a variety of methods, including thermoelectric generators and heat engines. Thermal energy is much more widely available in certain environments than sources like vibrations or radio waves.

Thermal energy harvesting has proved popular in industrial environments where heat is plentiful and the status of machinery needs to be relayed without laying additional cables.

Radio waves

It may come as a surprise, but radio waves or RF (radio frequency) is another type of energy that can be harvested. Radio waves can be converted into electricity using a process called rectification. The challenge with harvesting radio waves is the energy available is smaller than most other sources, so the technology required to capture it and to retain it needs to be more sophisticated and the amount of energy may not be sufficient for all applications. It has the advantage that it can be done at the lowest cost, with the smallest sensors and the harvesting can be done by devices embedded in packaging, apparel and other materials.

Increase your IoT effectiveness with Wiliot

Whether you're looking to deploy IoT devices in remote conditions or simply looking for the most effective and efficient ways to run your network, Wiliot is here to help. We can help you decide on the right type of energy harvesting for your business and work with you to implement the technology to get you up and running. Reach out to our team today to learn more.