Introduction: Wi-Tricity (Wireless Electricity)
Made by Manish Kumar, Murtaza Tunio, Minaam Abbas, Mustafa Rashid and Saad Hirani.
Wireless electricity is one of the most emerging solutions to the global power crisis. It is defined as the transfer of wireless electricity or power from a source to a load without the use of any artificial interconnecting conductors such as wires. Wireless electricity is being used primarily on the basis that at times, wires can be inefficient (power is lost as wires transmit electricity over long distances), inconvenient (in terms of cost and labor) and sometimes hazardous (many people may be electrocuted or put in some sort of danger).
Our team paid attention to two different forms of wireless energy transfer- the first is through resonant inductive coupling, whereby energy supplied to a coil is transferred to a similar parallel coil without the use of any wires in order to provide enough electricity to light LED’s (Light Emitting Diodes). The second is through the use of a laser that reflects onto a solar panel attached to a capacitor that stores the energy converted by the solar panel, and transmits it to an LED placed at a distance. This time, the LED is connected through wires as the laser already shows the transfer of wireless energy. Other forms of wireless electricity transfer not looked at include the use of microwaves etc.
Step 1: History
Wireless power transmission is not a new idea. Nicola Tesla demonstrated transmission of electrical energy without wires in early 20th century. Tesla used electromagnetic induction systems. Tesla discovered that electrical energy could be transmitted through the earth and the atmosphere. In the course of his research he successfully lit lamps at moderate distances and was able to detect the transmitted energy at much greater distances. The Wardenclyffe Tower project was a commercial venture for trans-Atlantic wireless telephony and proof-of-concept demonstrations of global wireless power transmission. The facility was not completed because of insufficient funding.
Earth is a naturally conducting body and forms one conductor of the system. A second path is established through the upper troposphere and lower stratosphere starting at an elevation of approximately 4.5 miles.
A global system for "the transmission of electrical energy without wires" called the World Wireless System, dependent upon the high electrical conductivity of plasma and the high electrical conductivity of the earth, was proposed as early as 1904
Following World War II, which saw the development of high-power microwave emitters known as cavity magnetrons, the idea of using microwaves to transmit power was researched.
William C Brown demonstrated a microwave powered model helicopter in 1964. This receives all the power needed for flight from a microwave beam. In 1975 Bill Brown transmitted 30kW power over a distance of 1 mile at 84% efficiency without using cables.
Japanese researcher Hidetsugu Yagi also investigated wireless energy transmission using a directional array antenna that he designed. In February 1926, Yagi and Uda published their first paper on the tuned high-gain directional array now known as the Yagi antenna. While it did not prove to be particularly useful for power transmission, this beam antenna has been widely adopted throughout the broadcasting and wireless telecommunications industries due to its excellent performance characteristics.
In 2006, more recent breakthroughs were made; using electrodynamics induction a physics research group, led by Prof. Marin Soljacic, at MIT, wirelessly power a 60W light bulb with 40% efficiency at a 2 meters distance with two 60 cm-diameter coils.
Researchers developed several techniques for moving electricity over long distance without wires. Some exist only as theories or prototypes, but others are already in use.
Step 2: Our Model Space Harvesting
Our model consists of ‘satellite’, which emits a laser, and a solar cell, placed on ‘earth’, designed absorbs the energy from that laser. This model demonstrates the concept of energy harvesting from space. The world today relies heavily on oil to fulfill its energy requirements; however, oil will not last long enough to sustain us for long. The US Department of Energy in the Hirsch report indicates that “The problems associated with world oil production peaking will not be temporary, and past “energy crisis” experience will provide relatively little guidance.” Moreover, the increasing demand for energy all over the world does not make the situation any better. Therefore scientists have proposed many radical solutions.
One of the proposed solutions is to place an array of solar panels in space and beam the energy generated down to earth by means of microwaves or lasers. Such a system has many benefits:
- Higher collection rate: In space, transmission of solar energy is unaffected by the filtering effects of atmospheric gasses. Consequently, collection in orbit is approximately 144% of the maximum attainable on Earth's surface.
- Longer collection period: Orbiting satellites can be exposed to a consistently high degree of solar radiation, generally for 24 hours per day, whereas surface panels can collect for 12 hours per day at most.
- Elimination of weather concerns, since the collecting satellite would reside well outside of any atmospheric gasses, cloud cover, wind, and other weather events.
- Elimination of plant and wildlife interference.
- Re-directable power transmission: A collecting satellite could possibly direct power on demand to different surface locations based on geographical baseload or peak load power needs.
Step 3: Our Model Resonant Inductive Coupling
2. Resonant Inductive Coupling
Our model here demonstrates that electricity can be efficiently transmitted over large distances using inductive coupling. It consists of a two coils which have been ‘inductively coupled’, that is, the magnetic field generated in one coil induces a magnetic field in the other coil. However the point that differentiates this from an ordinary ‘transformer’ type setup is the fact the magnetic flux in these coils has been made to vibrate at a specific frequency with the help of a capacitor. This enables the two coils to transfer energy effectively even over large distances!
Our focus here was to show that electricity can be efficiently transferred over couple of Inches with the use of resonant inductive coupling. With usage of higher frequencies and a more powerful output such a device could be used to eliminate the need for power cords or extension cables.
The basic purpose and motivation for this project stems from the fact that in the modern world, power has become short in supply and its demand excessive. The costs of maintaining power and equating it to the increasing demand for fossil fuels makes the production of electricity a difficult task. With the reserves of fossil fuels in the world set to end within the first half of the 21st century, now is the best time to explore alternative forms of electricity for usage around the world. Sunlight, water and wind have already been used for powering houses, but these are also resources of nature and considering the fact that we live in a biosphere with limited resources it would be foolish to chase something natural to replace another. Thus the production of electricity by resonant inductive coupling and through lasers seems a useful alternative to the power crisis.
The project not only demonstrates on a small scale the way in which such electricity is produced, but also explores throughout the course of this experiment, whether or not wireless power is a viable source of energy. By looking at various advantages and disadvantages we will be able to determine to what extent in the future, wireless electricity will and can be used to human advantage. The project was inspired from MIT visionaries who wished to use this method of producing electricity following the discoveries of Tesla to benefit power producers around the world and ease production burden and alleviate running costs.
Step 4: Advantages
There are several advantages for this new mode of energy transfer.
1. Highly Resonant Strong Coupling Provides High Efficiency Over Distance
This mode of wireless power transfer is highly efficient over distances ranging from centimeters to several meters. We define efficiency as the amount of usable electrical energy created from a source. This mode of transfer can assure a high rate of efficiency due to its design.
2. Energy Transfer via Magnetic Near Field Can Penetrate and Wrap Around Obstacles
The magnetic near field has several properties that make it an excellent means of transferring energy in a typical consumer, commercial, or industrial environment. Most common building and furnishing materials, such as wood, gypsum wall board, plastics, textiles, glass, brick, and concrete are essentially “transparent” to magnetic fields—enabling this technology to efficiently transfer power through them. In addition, the magnetic near field has the ability to “wrap around” many metallic obstacles that might otherwise block the magnetic fields.
3. Non-Radiative Energy Transfer is Safe for People and Animals
WiTricity’s technology is a non-Radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organisms—people and animals—and are scientifically regarded to be safe. Professor Sir John Pendry of Imperial College London, a world renowned physicist, explains: “The body really responds strongly to electric fields, which is why you can cook a chicken in a microwave. But it doesn't respond to magnetic fields. As far as we know the body has almost zero response to magnetic fields in terms of the amount of power it absorbs."
4. Scalable Design Enables Solutions from Milli watts to Kilowatts
This system can be designed to handle a broad range of power levels. The benefits of highly efficient energy transfer over distance can be achieved at power levels ranging from Milli watts to several kilowatts. This enables the technology to be used in applications as diverse as powering a wireless mouse or keyboard (milliwatts) to recharging an electric passenger vehicle (kilowatts).
Step 5: Build Your Own Model? Materials
- 100 feet of high efficiency coils.
- 2, 500 micro farads capacitors.
- Connecting Wires
- An Oscilloscope (1.1MHz)
- A volt meter.
Step 6: How to Build the Model? Step 1
How to Build it?
Wound the coils into 8 by 4 inches. There should be at least 35 turns. We used 35. Make two such coils. Remember to have some ends left out.
Step 7: How to Build the Model? Step 2
Scrape off the edges of each coil's end. This will take off the insulation on them. Do this for every coil you have.
Step 8: The Circuit
These are pictures of both the receiving coil and the transmitting coil.
Step 9: Plug in the Wires
Plug in all the wires as shown in the circuit. And Voila it works. You do need to mess around with the oscilloscope a bit though.
Step 10: Watch It Work!
Watch the magic :) The greater the distance, the dimmer the lights.
Step 11: The Second Model
The second model was pretty easy to build. We bought a solar panel from the market. Connected it to an led. We charged the solar panel using a class 2 laser for 5 hours continuously to get a useful power output. And then used it. The model was made from Styrofoam. We covered it in black chart paper to give a space kind of effect. And the base we painted blue and green to signify the earth.
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