Humankind has long sought alternative sources of clean, renewable energy. Scientists have turned their attention to an unlikely source: air humidity. Inspired by Nikola Tesla, researchers are now making remarkable progress in the field of hygroelectricity, a technology that aims to harvest electricity from the moisture present in the atmosphere.

The journey began when a humidity sensor in a laboratory unexpectedly started generating electrical signals without an external power source. This incident ignited curiosity and sparked renewed interest in Tesla’s original idea of obtaining electricity from humidity in the air, akin to storm clouds processes.

Tesla himself explored hygroelectricity in the past, with limited success due to technological constraints. However, recent developments in scientific research have breathed new life into this innovative approach. Research groups around the world are now delving into various methods to extract electrical energy from water molecules present in the air.

One of the key factors contributing to hygroelectricity advancement is the understanding that water molecules in the air can transfer small electrical charges among themselves. Scientists are tirelessly working to control this phenomenon and harness it for practical applications.

The primary challenge lies in harvesting enough electricity to make it usable for everyday purposes. Hygroelectricity can power miniature computers or sensors, but generating significant amounts of energy remains a hurdle.

Water molecules

In 2020, a breakthrough occurred when a team of scientists published a research paper detailing the discovery of protein nanowires produced by a bacterium. These nanowires could harvest electricity from the air. The exact mechanism behind this process is still under discussion. However, it is believed to involve the material’s tiny pores trapping water molecules, which then acquire a charge as they rub against the nanowires.

The team, led by Yao Luo, developed a revolutionary device that could function anywhere on Earth. Their innovative structure relied on nanopores that facilitated the accumulation and manipulation of water molecules, enabling efficient charge separation and electricity generation.

In a follow-up study published in May 2023, the researchers successfully replicated the nanopore-filled structure using a variety of materials. Graphene oxide flakes, polymers, and cellulose nanofibers derived from wood were among the materials tested. All exhibited remarkable electricity generation abilities.

Ongoing experiments of hygroelectricity

Current experiments have demonstrated that devices thinner than a human hair can generate small amounts of electricity, equivalent to a fraction of a volt. Although these initial outputs are modest, they serve as a proof of concept and inspire further development.

Looking ahead, Yao envisions scaling up the technology by increasing the amount of material used or connecting multiple pieces. These advancements could potentially result in useful charges of multiple voltages, unlocking hygroelectricity for a wider range of applications.

Reshma Rao, a materials engineer at Imperial College London, advocates flexibility in material selection. This adaptability fosters innovation and paves the way for sustainable energy solutions tailored to specific needs and contexts.

Reshma Rao, however, advises against expecting this technology to power entire buildings or energy-intensive machines such as cars. Rao points out that power generation may not be sufficient for such purposes.

Instead, hygroelectricity may be better suited to powering smaller devices like sensors in the Internet of Things (IoT) or wearable electronics. These compact and energy-efficient devices can benefit from continuous, low-level power generation offered by hydroelectricity.

Previous research on hygroelectricity

In 2020, a research group in Israel harvested electricity by passing humid air between two metal pieces. As the moist air flowed over the metal, it induced a charge in the material. This concept was built upon an observation made in 1840 when a train driver experienced tingling sensations and witnessed sparks between his fingers and the metal levers of the vehicle due to steam rubbing against the metal.

Colin Price, a researcher at Tel Aviv University, mentions that lab experiments using small metal pieces generated low charges. However, they are improving the system. Their process requires a relative humidity of 60% or higher, unlike Yao’s device, which generates electricity at a relative humidity of around 20%.

In Portugal, a team involved in the EU-funded project CATCHER focused on harnessing humid air as an energy source. Svitlana Lyubchyk from Lusófona University coordinated the project and co-founded CascataChuva.

CascataChuva’s prototype, about to be completed by the end of the year, incorporates a grey disc made of zirconium oxide. This unique material can trap water molecules in humid air and guide them through tiny channels, generating an electrical charge. Remarkably, a single disc supplies 1.5 volts, and just two discs power an LED. Connecting multiple discs will enable the increase of the overall output.

As the quest for renewable energy intensifies, hygroelectricity stands out as a promising frontier, capturing researchers’ imagination. With ongoing advancements in materials, structures, and understanding of charge separation mechanisms, Nikola Tesla’s vision is being propelled closer to reality.