You’d probably appreciate a self-powered cell phone and ear pods that need no charging, right? What about traffic that powers streetlights? Or what about using trash to generate power?
Energy harvesting, or energy scavenging, is at the forefront of trying to make such dreams possible. Our world is surrounded by “wasted” energy that we could harness to drive billions of gadgets and appliances.
Some speculate that this energy scavenging is the tip of an energy source iceberg. Some think energy harvesting could power devices interconnected via the Internet of Things (IoT). Others speculate that energy harvesting could mean the end of low-power batteries that drive small electronic devices.
That all does sound pretty nifty so let’s explore the world of energy harvesting technologies and their implications for helping to power the future.
What Is the Definition of Energy Harvesting?
Energy harvesting describes a process that enables us to take energy from our body movements or the environment’s ambient energy. This excess or residual energy could come from pressure, temperature differences, movement, or thermal sources.
We can store this energy and convert it into electrical energy to power the Internet of Things (IoT devices) and wearables like smartwatches and wristbands. For example, our arm’s movements may be enough to power a smart watch’s wireless sensors that constantly measure your temperature or heart.
Solar cells in solar panels are also examples of energy scavenging that takes energy from the environment. They are a massive part of the fight to halt greenhouse gas emissions and combat climate change.
Why Do We Need Energy Harvesting?
Harvesting energy could play a vital role in the energy chain. Globally, the U.S. Department of Energy anticipates total world electricity will almost double between 2018 and 2050 as more people connect to power grids and buy electrical appliances.
Wearable sales have grown rapidly with an estimated 30 billion IoT devices in use by 2030. Each has a DOI, a digital object identifier, broadcasting information and using energy to connected devices. Battery-free, self-powered wearables would undoubtedly help reduce demand for recharging these billions of pieces of technology.
With global warming and climate change a real threat, clean power generation is vital. Energy harvesting allows us to take advantage of a power source already there. Still, it has yet to be taken advantage of fully.
What Are Examples of Energy Harvesting?
Energy harvesting can come from many sources. These include the following:
- The motion of a human body, such as a moving arm powering a smartwatch
- The vibration energy caused by people walking in the street or from train tracks
- The magnetic field around power lines
- The power of waves
- Capturing excess thermal energy at electricity-producing power plants
- Harnessing radio waves
How Does Energy Harvesting Work?
Several types of energy harvesting can power electronics or be used for energy generation or storage. These sources come from various types of energy, including:
- Solar energy: energy from the sun
- Kinetic energy: energy of movement, such as people walking
- Thermal energy: heat energy based on an object’s temperature
- Electromagnetic energy: energy that travels as wavelengths, like radio waves
- Mechanical energy: an object doing work, such as a wrecking ball demolishing a building
Can Energy Harvesting Use Solar Power?
We harness the sun’s power through energy harvesting in several ways.
Photovoltaic (PV) solar panels are the most familiar, essentially harvesting devices. A solar panel’s cells convert sunlight into an electric current to power appliances or store it in batteries for later use.
We further use the sun’s ambient energy to heat homes or water. There are power plants that melt salt using the sun’s energy, salt that later creates steam to power turbines to generate electricity.
Solar power has also been used on road traffic signs, in calculators, wristwatches, and powering remote weather stations. However, the sun is not always available indoors or at nighttime, leading to further energy harvesting technologies.
What Is Piezoelectric Energy Harvesting?
Piezoelectric—creating electricity through pressure—is a fascinating branch of energy harvesting. Vibrations are a type of energy of movement, also called kinetic energy.
A process called transduction can change this vibratory movement into electrical energy. Researchers have built piezoelectric transducers that convert motion into usable electrical power. This power supply can charge a battery, power a remote sensor system directly, or work with a supercapacitor. A supercapacitor offers energy storage like a battery but undergoes frequent and rapid charges and discharge.
Most piezoelectric transducers offer low-frequency electrical currents, limiting their uses in the energy harvesting field thus far. But they can replace batteries in gadgets and devices like sensors or watches. Piezoelectric transducers are common where a stronger electrical current is available through batteries or the power grid, placed in everything from security alarms to kidney stone-removing ultrasound machines.
Piezoelectric’s energy conversion efficiency is holding it back as an energy harvesting source. Yet there are high hopes for piezoelectric energy harvesting going forwards.
Piezoelectric roads could be powered by the vibrations of the vehicles driving on them and city centers by people walking on the streets. And with the development of researchers hope to make implantable pacemakers that can power themselves. The oscillating piezoelectric transducer would work with the beating heart’s movements to ensure it continues to work.
Does Energy Harvesting Take Place With Thermal Power?
Power plants use nuclear fission or burn coal or natural gas to create steam to rotate electricity turbines. Much of this steam, or thermal energy, goes to waste. Similarly, industrial processes, engines, and machines all give off thermal energy that could be reused.
Thermoelectric generators are a new development seeking to maximize the thermal energy in the environment. These thermoelectric generators use differences in temperatures to create electricity. This is called the Seebeck effect.
One requires two electrical conductors or semiconductors for the Seebeck effect to work. The two need to be dissimilar. If you heat one of the conductors, its heated electrons flow toward the cooler conductor, producing a small electric current.
A Seiko watch powered by a tiny thermal generator uses the differences in the wearer’s body and the ambient temperatures. Some factories already have energy harvesting power management schemes in place. For example, they use heat from furnaces to warm their offices or buildings.
This optimization of energy use is long overdue; some power plants now capture their wasted heat, estimated at up to 72% wastage.
Energy Harvesting and Electromagnetic Energy
It’s safe to say that Earth is a noisy place; if there are aliens, they can’t help but notice our love of the radio wave!
Cell phones, television broadcasts, radio shows, and Wi-Fi signals are a veritable electromagnetic cacophony. From broadcast masts to satellites, radio waves are everywhere. And yes, you guessed it, we don’t use all of these radio waves — which means they are ripe for energy harvesting.
This radio frequency energy harvesting is known as RF energy harvesting. An antenna circuit collects any excess electromagnetic waves then a rectifier turns that into direct current.
We can also conjure up electricity seemingly from thin air. Placing a conductor tube under power lines attracts electric energy in the electric field surrounding the transmission lines. Sensor nodes, powered by the harvested energy, can help charge a battery from the electrical energy shed by the power lines that would otherwise have been lost.
Can Energy Be Harvested From Humans?
Energy harvesting already occurs from humans with wearables that charge thanks to our movements.
Humans as energy harvesting systems go further. The vibrations we make walking on streets or even in our homes could be converted into electric energy. The cars we drive, the trains we take, the flights we enjoy — many actions can become electricity through energy harvesting.
Think about a deafening concert. All that dancing and jumping, plus the vibrations from speakers, are mechanical energy that could be redistributed as electricity — perhaps to power the cash registers and the fridges that are cooling the drinks!
Some researchers are trying to go one step further. Bracelets, rings, and earrings we wear could transmit information between our wearable IoT electronic devices like smartphones and laptops. We become the antenna, and the jewelry uses visible light communication (VLC) to share data.
How Do We Harvest Ocean Waves?
Ocean waves are a powerful force, and we’re only just learning how to use them as energy sources.
The back-and-forth and up-and-down motion of waves can move a buoy. This movement can be turned into rotation within the buoy, creating electricity through its internal generators. Technological advances are pushing ocean wave energy forwards.
Dielectric materials that don’t conduct electricity can boost energy harvesting at sea. A dielectric polymer not only increases efficiency but it can act as a sensor node to help with monitoring. Furthermore, these materials are actuators, meaning they help convert mechanical energy to electrical energy.
Is Energy Harvesting a Renewable Energy?
Energy harvesting is renewable energy. It replenishes and there’s an unending source.
Solar energy is the primary large-scale example of energy harvesting, and solar is considered a renewable source of energy. Ocean waves will continue to crash, radio waves will emit as long as humans communicate and there will always be thermal energy to harness on Earth.
Movement, or kinetic energy, will continue as long as life, light, noise, and vibrations occur. What’s unclear is the source of this energy and which is easiest to capture. However, energy harvesting has a lot of potential. It will exist as long as other energy sources create an excess.
Can We Harvest Rain Energy?
It’s possible to harvest rain energy from raindrops, although, in practice, it may be tricky. Raindrops don’t fall that hard, it’s not always possible to know where a shower will land, and the technology isn’t overly efficient.
It’s estimated that it would take a football field-size rain panel working at a theoretical 100% efficiency during historic rainfalls to operate the average U.S. home. Remember that the most efficient solar panels on the market function at around 25%. Researchers trying to develop wind turbines that work with the wind from passing cars may be onto something a little more plausible.
What Are the Disadvantages of Energy Harvesting Systems?
Energy harvesting is in its infancy, notwithstanding the growth of solar energy. Disadvantages for the nascent harvesting industry include the small electric charges available, making them suitable only for small self-powered devices.
Many materials, especially piezoelectric materials, are not 100% stable depending on conditions and degrade over time. Costs associated with thermoelectric generators are high for a low output return. Even well-established solar power only works well on bright days and less so in winter.
In short, energy harvesting technologies, excluding solar panels, have a long journey before mainstream acceptance and affordability.
Energy Harvesting: Making the Most of What We Have
The Earth is our home, and it needs to be treated and taken care of so it shines. As such, we must ensure we don’t waste what we have.
A few billion more people than at present will call Earth home before this century ends. At the same time, more and more countries are connecting their citizens to their power grids. We, friendly humans, are cell phone and internet obsessed, keeping in touch at all hours. Our power demands are going up.
Like any expanding household, it does well to reassess the energy expenditure from time to time. It’s clear we cannot keep burning fossil fuels like we have in recent years if we want to avert a climate change disaster.
Energy harvesting represents a reflective stage of assessing our energy use. It’s basically good housekeeping — why throw perfectly good energy out the front door or send it up the chimney when it can be used better?
It will take time and technology to understand how to use the oceans’ swells and the sun’s rays; these are the grand-scale questions. But every tiny action counts too. This is why self-powered wearable electronic gadgets, recycling of thermal energy, and creating a home energy efficiency checklist make perfect sense.
The best bit about energy scavenging? Many of these methods will blend into our current lifestyles unnoticed, so we can enjoy the power and the connectivity of the Internet of Things without adding to our carbon footprint. Energy harvesting could be a vital harvest for the world.
Brought to you by amigoenergy
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