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Energy Harvesting: The Recycling of Energy

There has been considerable discussion on the energy consumption of Korea lately. Controversies regarding the establishment of new nuclear power plants garnered public interest recently because no better options seemed to exist. Aside from the numerous new and renewable energies that could be possible solutions to this dilemma, a different approach to energy conservation called energy harvesting might be the most beneficial in Korea’s present environment. Energy harvesting aims to efficiently collect the various energies that have been inevitably abandoned in daily life. The Sungkyun Times (SKT) now elaborates on the concept of energy harvesting, its advantages, and the suitability of energy harvesting in Korea.

Energy Harvesting

What Is Energy Harvesting?

Energy harvesting refers to the act of gathering energy that has been wasted in people’s daily lives. The term originates from the fact that related technologies focus on “harvesting” energy that exists in surrounding environments. Energy harvesting is also described as the recycling of energy since its main energy sources are reused from already-spent energy. One of the basic principles of science is that energy cannot be created or destroyed. All of the energy that people use is converted from another source. For example, thermal power plants burn fossil fuels for heat energy, which is converted into the kinetic energy of water vapor, which is then converted into electric energy. The same principle is applied in energy harvesting. When people walk, most of their energy is converted to sound, heat, and vibration energy. Energy harvesting technology clusters this wasted energy and converts it into valuable electricity. Although the idea of energy harvesting is not something new and can be found in longestablished inventions such as the waterwheel or the windmill, modern technology has further developed its potential by opening numerous new fields of utilization. A market research company called IDTechX reported that the energy harvesting market scale was at $7 billion in 2012, $9 billion in 2015, and $15 billion in 2017.

Advantages of Energy Harvesting

Energy harvesting is economically beneficial because not a lot of money is needed for obtaining its energy sources. Thermal power plants need fossil fuels, nuclear power plants need uranium, and hydraulic power plants need water. All of these energy sources need continuous investment whereas energy harvesting does not need any. Energy harvesting uses whatever is nearby as energy sources whether it is a car on a freeway or pedestrians on sidewalks. Energy harvesting devices are designed for efficient and sustainable energy and are environmentally-friendly.

greenlaunches.comjwt/ Vodafone Power Pocket

Moreover, energy harvesting is an innovative method of saving energy. High proportions of the energy people spend in their daily lives is wasted in most cases. A car, for instance, only uses 18% of the fuel input for driving and over 62% is wasted as vibration, heat, and sound energy. According to Innowattech, an energy harvesting company, 35% of this wasted energy can be harnessed for reusable electrical energy with the help of energy harvesting technology. Another example of energy conservation is using the heat energy of humans. A person is known to emit 120W of power when staying still and 190W when exercising. 1W is one watt, which is defined as the energy spent per second. 2.5W is the typical amount of power needed to charge a smartphone. In other words, a smartphone can be charged at any time if only 1~2% of the heat released from one’s body is harvested. In fact, England’s major telecommunication company Vodafone manufactured a product based on this idea. Vodafone’s Power Pocket uses body heat to charge 4 to 11 hours of smartphone usage time by placing the phone in one’s pocket for a day. As these examples clearly show, energy harvesting has amazing potential in collecting and converting inevitably wasted energy. Last but not least, energy harvesting has considerable potential in its immense range of applications. As energy harvesting’s objective lies in accumulating even minute fragments of existing energy, diversity can be found in its technology. Temperature differences between the outdoors and indoors, the speed of trains, artificial lighting, and even electromagnetic waves are possible energy sources in energy harvesting. Hot waste water from nuclear power plants can also be recycled with the appropriate technology. Many applications of energy harvesting are now within reach thanks to the progress of modern science.

Core Technologies of Energy Harvesting

Piezoelectric Technology Collecting the Energy of Movement

Certain objects such as ceramic, deoxyribonucleic acid (DNA), or bones emit electricity when pressure is applied. This phenomenon is caused by disruptions in electrical balance. When pressure alters the shape of an object, the electrical balance is broken and an electrical current begins to flow. This is called the piezoelectric effect and is one of the most important technologies in energy harvesting.

Left: digitaltrends.com/ Pavegen and Google’s Piezoelectric Technology CollaborationRight: japanesestation.com/ Piezoelectric Energy Harvesting in a Japanese Subway Station

Pavegen, a British piezoelectric technology company, built an energy harvesting soccer field for children in Rio de Janeiro, Brazil. Two hundred tiles of piezoelectric power generators were spread under the field’s grass. When children played during the day, energy would be generated and stored for lighting the field at night. Every footstep would be worth 5W of electrical power and the power efficiency was over 90%. High electrical power efficiency means that most of the energy input in the generator is converted into electricity. When the magnitude is increased from children’s footsteps to the pressure of cars and trains, large amounts of electricity can be stored through energy harvesting as well. Professor Sung Tae-hyun of Hanyang University’s Department of Electrical Engineering claims that when piezoelectric technology is applied to one kilometer of Korea’s freeways, the monthly electrical power consumption of 250 houses can be generated every hour. He explained that although the initial installment fees might be a burden, they would be worth investing in for the long-run.

Thermoelectric Technology Gathering Heat

Temperature differences between the indoors and outdoors, between the body and the atmosphere, and between other materials are also sources of electricity. Heat and energy are proportional to each other and the activeness of electrons is proportional to energy. High heat will, therefore, result in active electrons. When there is a temperature difference between materials, the more animated side’s electrons will flow to the other side and electricity will be generated. This is called the thermoelectric effect, and it is a very useful energy harvesting technology. Wearable devices using heat to prolong battery life are good examples of thermoelectric technology applied to energy harvesting. Other approaches for usage of thermoelectricity include electric generators on frosty windows, sleeping bags, or even people’s clothes.

guff.com/ Photoelectric Effect

Photoelectric Technology Recycling Light

Albert Einstein had an exceptional career filled with scientific achievements, but what earned him the Nobel Prize was the discovery of the photoelectric effect. The photoelectric effect states that light will create electricity in metals. The detailed conditions are different depending on the types of metal and light, but the fundamental principle is that electricity can be obtained from light itself. Solar panels are representative examples that use the photoelectric effect. Energy harvesting technology goes a step further than solar panels and collects artificial light as well. Artificial lighting such as light bulbs, fluorescent lights, electronic displays, and streetlights are also capable of creating electricity given the right circumstances. The Korean Institute of Science and Technology (KIST) developed a two-sided photoelectric panel that collects light from the sun and artificial light from indoors simultaneously to increase its efficiency. Energy harvesting technology uses the photoelectric effect to create a virtuous circulation of energy by converting light to electricity, and back to light again.

Energy Harvesting in Korea Compatible

Technology to Korea’s Environment

Energy harvesting is an interesting concept and has its advantages, but whether it fits into Korea’s energy spending environment or not is a controversial topic. Fortunately, Korea is one of the leading countries in energy harvesting technology. According to a thesis by the Korea Technology Innovation Society (KOTIS) on energy harvesting patents, Korea held the highest number of patents following the United States (US). The study compared Korea, China, Japan, the US, and Europe on the number of energy harvesting patents and their competitiveness. Korea’s energy harvesting technology was rated 3rd on its competitiveness after Japan and the US. Korea especially exceeded in thermoelectric and photoelectric technologies and won international recognition. The Ulsan National Institute of Science and Technology (UNIST), for example, integrated thermoelectric and photoelectric technologies into a single energy harvesting device. The device collected sunlight from one side, and body heat from another. This combination of technology resulted in a high power efficiency of 10% which is more than two times the average efficiency of 4 to 5%. Korea’s highly-concentrated urban population is also a factor that makes energy harvesting compatible. A statistic from Korea’s capital, Seoul, showed that over 10 million people use the Seoul Metro in a single day. Crowded stations such as Gangnam Station have an average of 200 thousand users daily. If energy harvesting technology was applied to Korean subway stations or freeways, Korea would have more satisfying results than many other countries.

Commercialization of Energy Harvesting in Korea

Korea’s high level of energy harvesting technology and its suitable environment have led to several attempts on the commercialization of energy harvesting. A venture company released an energy harvesting electrical mat that collects electromagnetic waves as an energy source. It stores electromagnetic waves from its surrounding environment and makes the product more electrically efficient overall. Many efforts to make connections with technologies of the Fourth Industrial Revolution have recently taken place as well. The Korea Electric Power Corporation (KEPCO) and its affilated companies are trying to commercialize the Internet of Things (IoT) with the technologies of energy harvesting. IoT technology focuses on making “smart” everyday objects and linking them to create a network. One of IoT’s disadvantages was found in the impermanent sources of energy. Electrical lines always need to be connected without the help of batteries. Energy harvesting, however, allowed the IoTs to continuously collect energy from their surroundings as a permanent power source. KEPCO utilized this property and made wireless IoT sensors for commercialization, and are now researching telecommunication IoTs that can deal with power outages caused by natural disasters.

Although Korea’s energy harvesting position seems promising and commercialization does not seem far away, there are still some drawbacks that have not yet been solved. As of today, the power efficiency of energy harvesting technology is not sufficient enough. Piezoelectric technology shows an average of 25 to 50%, thermoelectric technology ranges from 0.1 to 3%, and photoelectric technology ranges between 10 to 24%. Although the maximum values for each technology varies, the output is not enough since energy harvesting is a recycling concept and the overall input is too low. Another problem is related to the cost of expensive harvesting technology. The quality of energy harvesting’s technologies are being improved at a high pace, but it might not be the best choice to commercialize costly technology that will be outdated after a couple of years. Installment fees and maintenance fees are also of concern. The California Energy Committee concluded that energy harvesting is a power source which is as beneficial as natural gas in ideal conditions, but much worse in most cases.

hankookilbo.com/ Energy Harvesting Electrical Mat

It is not easy to say that energy harvesting is the ideal solution for Korea’s current situation. Nevertheless, the development of technology and decreases in installment costs hint at an intersecting point in the future where energy harvesting is efficient both in terms of energy and cost. It would be sensible to prepare for this possible future change.

최영찬  cyc1117@naver.com

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