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Acoustic Power Generation : Reverse Engineering the human ear 1. 2. 3.
Praveen Kumar N Suraj Srinivas Pramukh Bharadwaj MV
II Semester K section (ECE) PES Institute of Technology
“The more I study nature, the more I stand amazed at the work of the Creator.” --Louis Pasteur
Conventional and Non Conventional energy sources, Conversion, Storage
Contents • Introduction – Present energy scenario • Why select sound energy? • How much of sound energy are we wasting? • Principle – Piezo electric effect • Inspiration from human ear • Sound to electricity conversion procedure • Expected Energy • Advantages of Acoustic power generator
• Applications • Way forward
Introduction – Present energy scenario The world mainly depends on fossil fuels (coal, petroleum and natural gas) with 85% of our energy requirements satisfied by fossil fuels
Introduction – Present energy scenario The popular conventional energy sources pose environmental concerns with fossils fuels contributing for about 90% of sulphur oxides and 80% of carbon di-oxide emission
Introduction – Present energy scenario They are also nearing exhaustion. Graph indicates steep downturn in fossil fuels availability around year 2030
Introduction – Present energy scenario Thus the various non conventional , renewable , greener energy sources need to be tapped. Solar Energy Wind energy Geothermal energy Ocean energy Biomass Energy Sound Energy
Why select sound energy? Inexhaustible
Able to cause noise pollution
How much sound energy are we wasting ? Case 1: Industry: Consider a processing factory with 250 heavy machines, each emitting sound of loudness 110db ie an intensity of 0.1W/sq.m running for 10 hr a day for 1 year. The energy per unit area that can be used is E = (250)(1mW)(10hr)(365days)
E = (250)(1mW)(36000s)(365) E = 328500000 J
E = 328MJ 9
How much sound energy are we wasting ? Case 2: Road Traffic: Total road length in India is 32 lakh km. If one acoustic plant is set up for every 50m there will be 6.4 crores in total. Considering average traffic loudness to be 90 db ie of intensity 1mW/sq.m running for 15 hr daily, and assuming efficiency of power generator energy to be 100% energy that can be harnessed per unit area in 1 year will be : E=n*P*t where n is number acoustic generators E = (64000000) * (1mW) * (15h)(365days) E = (64000000)(1mW)(54000s)(365) E = 126144000000 J
E = 126GJ
Principle : Piezoelectric Effect • Accumulation of charges (flow of electricity) on certain solids in response to the applied mechanical stress is called piezoelectric effect. • Flexoelectric effect is phenomenon where voltage is induced due to a strain gradient in the crystal. • Quartz, rochelle’s salt, barium titanate,lead zincronate titanate, polyvinilidene flouride are good piezoelectric crystals.
11 On these lines, sound (mechanical energy) can be converted to electrical energy
Inspiration from the human ear Function
Acoustic power generator
Conical collector inlet
Converging ear canal
Conical collector and spiral house
Perilymph , Endolymph
Water or glucose solution
Conversion procedure Sound energy
Diaphram Spiral house with piezo crystal Rectifier and filter 13 Battery
Conversion Procedure 1. Sound Source:
Any continuous sound source can be used Louder the sound , louder the intensity. Intensity increases with loudness in a logarithmic scale
where , L loudness of sound in db I is intensity of sound Louder the intensity greater is the power output.
Conversion Procedure Target sound sources are
Target sound sources
Loudness in db
Intensity in W/sq.m
Industry – Heavy machinery Air compressor Milling machines Textile loom Boilers Sirens
Plane and Jet takeoff
Conversion Procedure 2. Conical collector:
Input sound Intensity I Through CS Area A
Output sound Intensity I’ Through CS Area A’
The sound from the source is collected by the near conical structure shown. Sound intensifies as it travels through it. For any sound, P=IA where P is power and A is area I is intensity of sound According to the Law of Conservation of Energy Input Power = Output Power IA = I’A’
Conversion Procedure 3. Diaphragm : Diaphragm is fixed at the output end of the conical structure They transfer the sound vibrations to the next stage (spiral house)
Durable Greater power output
Natural Rubber or Silicone rubber can be used
Conversion Procedure 4. Spiral house : Piezo electric crystal
The outlet of conical collector and the inlet of spiral house are connected via a
diaphragm The area of spiral house is continuously decreasing to provide further amplification. For a given conical collector, the output intensity increases with decreasing outlet area of spiral house. The spiral house is filled with water to reduce energy losses Spiral house houses an array of piezoelectric crystals
Conversion Procedure 5. Piezoelectric crystal :
The spiral house houses an array of piezoelectric crystals (quartz) for gradual energy absorption (compounding )
The crystals are arranged such that the pressure waves are incident on the crystal along that crystallographic axis which lies on the bond line which produces maximum intra-molecular deformation.
Deformation of the molecules results in a net dipole moment and leads to charge accumulation on the surface 19
Conversion Procedure 6. Rectifier and Filter:
The output current from the crystal is a haphazard signal This is smoothened by using proper electronics A output from crystal is fed to a rectifier to obtain a direct current
The small remaining ac component is removed by the filter A smooth dc voltage is thus obtained 20
Conversion Procedure 7. Storage: ATP Cell
1 – Voltage supply 2 - Electrodes 3 - Acidified soln. of Phosphate ions + ADP+ ATP sythesizer
Voltage is applied to electrodes dipped in a solution of ADP (adenosine di phosphate),phosphate ions and the enzyme ATP (adenosine tri phosphate) synthesizer DC Voltage ATP ADP + Phosphate ions ADP is converted into ATP thus storing the electrical energy produced
Calculations : Absorption of sound by crystal Let the acoustic absorption co efficient of the crystal per unit area be ಕಅ. Let the areas of the two ends of the spiral be ౧ & ౨ (౨>౧).
The intensity amplification = ౨/౧ Now, the input sound waves will effectively be incident on an area equivalent to ౨-౧.
Hence, the intensity of sound absorbed will be ಐa= (౨-౧)* ಕಅ* ಐi
where ಐi is the sound intensity incident 22
Calculations – Expected Output Voltage The charge (Q) developed by surface is directly proportional to the applied force (F) . Q = F*d
where d is proportionality constant
C = KA/t
where K is permittivity
V = Q/C V = (d/K)*(t)*(F/A) ………………………………..eq.1
V = gtP Where P is applied pressure, t is thickness and g is voltage sensitivity of the crystal Considering sinusoidal pressure wave, V=gt(Pmax sin(wt))
where gtPmax = V0
Hence the maximum voltage developed is proportional to the maximum pressure of the sound wave.
Design Options Two design options are suggested Macro Design
Frequency dependant applications
Frequency independent applications
Uses resonance pipes
Uses levers for amplification
Uses levers for mimicking the action of auditory ossicles to provide greater amplification
Can be used in limited numbers
Can be used in large numbers 24
Advantages • Continuous and inexhaustible input supply • Output hardly dependent on geographical location • The generator uses energy which is otherwise wasted • Eco friendly • Minimum Investment
• Occupies less space • Sleek • Potable • Easy construction • Can have an acoustic power generator in our own homes
Spyware applications , Burglar alarms
Prediction of tectonic movement
Small scale electricity source
Energy Supply to human body by the ATP cell
Multiple Generators in auditoriums
In everyday life to power cell phone s and other small devices
Way forward 1. The power output is not very high, right now. 2. But we believe that, given enough time and research on this particular topic, we can certainly come up with more efficient ways to build on the idea. 3. Taking inspiration from Michael Faraday, who first used a galvanometer to show the small current induced by EMI, we have the attitude of nurturing this toddler to dizzying altitudes.
“To know how to wait is the greatest secret of success” -- De Maistre