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You can check out Brilliant.org/SciShow to learn how to take your  STEM skills to the next level. [♪ INTRO]. From the blowing wind to the shining  sun, energy is all around us.

And humans have an almost insatiable  demand for it, so scientists and engineers are always on the lookout for sustainable  ways to provide the energy we need. And, sure, with tools like solar panels,  wind turbines, and geothermal wells, they’ve already found some great  alternatives to fossil fuels. But then there are the other ideas.

The  alternative alternatives, if you will. Some could be the next big thing; others  might be as kooky as they are clever. Here are six of the weirdest ways  to harvest the energy around us.

Unless you’re standing next to  a nuclear reactor or something, the biggest source of energy near  you right now might be, well, you. Just sitting around, an average  adult male human gives off heat at a rate of about ninety Joules per  second, which is to say, ninety watts. That’s quite a lot of energy just going  out into the world as wasted heat, so some people are trying to put it to work.

The easiest way might be to  just repurpose that heat, like they’ve done at the  Stockholm Central train station. Around a quarter-million people  pass through it every day, generating a lot of heat as  they wait for their train. The station’s ventilation system captures  that heat by using it to warm water, which then gets piped into nearby  buildings to help heat them in the winter.

At maximum capacity, those office buildings can cut their heating bills by  25%, which is no small savings. But what if you want to put  your own body heat to work without living in Stockholm  or wrapping yourself in pipes? Thermoelectricity might be for you.

First discovered in 1821, thermoelectricity  is a property of certain materials. Basically, when there's a difference  in temperature across these materials, it can generate an electric current. Traditionally, this was a  very inefficient process, but modern materials science has  made significant improvements.

Most thermoelectrics today are semiconductors, like the materials used to make computer chips. Take bismuth telluride. It’s a  room-temperature semiconductor that, when combined with antimony, produces a  thermoelectric used for refrigeration.

It might sound complicated, but working with  thermoelectrics can actually be really simple. In 2013, for example, a high school student used thermoelectric tiles to  create a self-powered flashlight. Just grab it by the handle  and your hand’s body heat creates enough electricity to light up  the LED inside, no batteries needed.

NASA scientists are studying thermoelectrics  for use inside astronauts’ spacesuits. And, in 2017, researchers described  using them to create medical implants that can be powered by the  patient’s own body heat, like devices to help with regenerative  therapies for bone tissue, or brain stimulation for motion disorders. For many alternative energy proposals, a major obstacle is the need to build  lots of infrastructure at massive costs.

But there’s one kind of human infrastructure that’s already virtually  everywhere on

Earth: radio waves. From your favorite radio station  to the WiFi router on your desk and the cell tower down the block, radio  waves are already everywhere we are. And as a form of electromagnetic radiation, every radio wave carries energy that  we can snatch right out of the air. Engineers in the twentieth century  developed special antennas, called rectennas, that can convert  these waves into electricity.

In the sixties, they were  experimenting with using microwaves to beam power from place to place, and  the rectenna was a big part of that. That never really panned out.  But it does demonstrate that, unlike the wireless charging technology  that might be built into your phone, rectennas work at large  distances from the transmitter. That said, the tradeoff for being  able to gather this kind of power from basically anywhere is  that you don’t get a lot of it.

Like really not a lot; we’re talking power measured in  microwatts or even tenths of microwatts. That’s not enough to charge your phone, but it could be enough to power tiny sensors. The goal here is to inject technological  “smarts” into basically everything around you.

For example, diagnostic pills that noninvasively  beam medical data out of your stomach, or walls that can “intelligently” reflect and  redirect signals so your wifi is always in range. Which is weirdly close to that old  saying about “if walls could talk,” but it’s pretty cool that  it might soon be possible. Not all possible energy sources  have potential applications as important as wireless medical data.

But that doesn’t mean they  can’t just be plain fun. The human body is an amazing tool  for converting chemical energy, like, you know, potatoes, into  the mechanical energy of motion. But, since every action has an  equal and opposite reaction, only some energy in each step  goes into pushing you along.

The rest is spent trying to push the Earth back, where it’s effectively lost,  unless we can capture it! One way to do that is through piezoelectricity,  a property of some crystals in which they acquire an electric charge when compressed, transforming mechanical  energy into electrical energy. Sure, that might sound like pseudoscience,  but it was actually discovered in 1880 by future Nobel Laureate Pierre  Curie and his brother Jacques.

Even if you haven't heard of them, you've probably heard of Pierre's wife  Marie Curie. Talk about a power couple. Piezoelectricity works because the crystal  structure of some materials is not symmetrical.

When you compress one of these crystals, the molecules physically stretch or are squeezed, moving the positive and negative  sides together or apart. And with positive charge on one side  and negative charge on the other, the crystal can now conduct an electric current! So, to capture the energy lost by walking, engineers just need to place piezoelectric  materials underneath everywhere we walk.

Which sounds, ya know, expensive. But there are some places where we step  more often than others, like dance floors! In 2008, this idea was put to the test by a pair  of nightclubs located in London and Rotterdam and I remember it because I wrote  about it in my blog, EcoGeek.

By creating a piezoelectric dance floor, the  clubs could capture the energy of dancing and put it to use by running the lights  and powering the air conditioning. Each dancer creates up to twenty watts  of power, which isn’t a lot on its own. But add together more than a  thousand people on the dance floor and now you’re really talking!

This idea has also been tested at larger  scale on a highway in the Netherlands, where it could produce enough  power to sustain traffic sensors without the need for solar panels. It might also make sense in  other places with high traffic, like subway platforms and busy sidewalks. So the next time you feel a  little extra spring in your step, it might just be all the  power you’re leaving behind!

If there’s one thing humans do  more than anything else, it’s talk. When you talk, your vocal folds create  vibrations in the air that propagate outwards; and remember: where there  is motion, there is energy. As a kid, you might have put this  vibrational energy to work transmitting sound if you ever tied a string to two  cups to make a simple telephone.

The idea might be simple, but during  World War II, it was used in a big way. By the end of the war, naval officers could  communicate between the decks of a ship, or even across an island, using  nothing but voice-powered telephones. A sailor talked into the  device, a special generator would convert the vibrations from  their voice into enough electricity to send the message up to sixteen  kilometers over telephone wires.

And while we obviously have more  advanced communications equipment today, these voice-powered telephones can still be found on US Navy ships for use in emergency situations. But even if you never set foot on a ship,  sound power might be in your future. In 2012, researchers at the  Queen Mary University of London experimented with tiny generators  that could power a pacemaker based on nothing but the sound of your heartbeat.

For use outside the body, there’s also  the phenomenon of triboelectricity, which is basically a fancy  term for static electricity. Triboelectric nanogenerators work when  two different materials repeatedly collide or rub against one another, exchange  electrical charge, and generate a current. And in 2015, researchers published a way to  power these tiny generators with sound vibration.

Their experimental system could generate up to one hundred twenty-one milliwatts  per square meter of material. That’s obviously not a ton of power,  but these nanogenerators have been successfully adapted for tasks like air  filtration in noisy urban environments. Wind power is one of the oldest  forms of energy generation, but even here there’s room for new ideas.

Over the last twenty years,  electricity generated from wind power has grown from virtually nothing to  nearly ten percent of all US power. But wind turbines are big,  expensive things to build, which limits where they can be  placed and how they’re built. That’s got some energy investors considering  the use of giant kites to create power instead.

Funding from companies like Shell and Google is supporting research into  kite-powered generators that, while less powerful than wind  turbines, might also be cheaper. The idea is to fly one or more kites  several hundred meters above the ground, where the wind blows with more  force and greater consistency. It’s called crosswind kite power because the kites spend most of their  time flying perpendicular to the wind.

One project under construction in  the UK will use a pair of kites flying in a figure-eight pattern to produce  up to five hundred kilowatts of electricity. And theoretical studies suggest improved designs may be able to create up to  tens of megawatts in the future. That’s probably at least a  little more than you were getting when your sweet butterfly kite  took to the skies as a kid.

Alright, we’ve got one wacky source of power left and it’s maybe the most remarkable of all:  creating electricity literally out of thin air. Well, kind of—the power comes from  the moisture the air has absorbed. One of the most promising approaches, developed in 2020 at the University of  Massachusetts Amherst, is nicknamed Air-gen.

The device is made up of a  seven-micron-thick film of nanowires derived from protein, of all  things, connected to electrodes. When this combination is exposed  to humidity in the ambient air, the film absorbs molecules of water,  and a moisture gradient forms. Some of the water molecules will be  ionized, or electrically charged, so that moisture gradient creates  a gradient of charged particles.

Those charges flow, creating a current. In lab experiments, the Air-gen could  sustain a consistent level of power for around twenty hours before  needing a few hours of rest. And that performance remained steady for the  duration of more than two months of testing.

One promising application of this technology would be helping keep your  smartwatch or cell phone charged without ever having to plug it in. And incorporated into paint, it could potentially also help your walls  generate electricity to power your home. At least, if you live in a fairly humid place.

What is it with energy researchers and walls? If this all seems kind of miraculous,  that’s just the power of modern engineering. As researchers gain control over  more materials at smaller scales, they’re discovering the kinds of properties  we could only dream of in the past.

Of course, just because all these  forms of power are possible, doesn’t mean that they will prove to be practical. But they do reveal how much energy  is around us literally all the time. If we can find a way to harvest even a bit of it, we’ll be on our way to a more sustainable future.

If you’ve enjoyed this  helping of quirky engineering, you might like to keep learning with  an engineering course from Brilliant. In keeping with the theme, there’s  even a course on Solar Energy, which will teach you everything about  how we capture energy from the sun. And there are tons more courses, not just  in engineering, but in basic science, computer science, and math.

Just all  kinds of ways to learn something new. If you’re interested, you can go to  Brilliant.org/scishow to learn more. And you’ll save 20% off an annual Premium  subscription if you use that link to sign up.

So thank you for your support! [♪ OUTRO].