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Energy Harvesting & Design Optimization Laboratory, UMBC
Department of Mechanical Engineering
University of Maryland, Baltimore County
Mechanical Motion Conversion from
Reciprocating Translation to One-Directional
Rotation for Effective Energy Harvesting
Kabir Ahmeda, Soobum Leea
aDepartment of Mechanical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle,
Baltimore, MD, USA 21250-0001
1/19
Outline
Literature survey on Energy Harvesting Buoy
Our Idea
Prototyping
Power Estimation Study
Conclusion
Future Works
2/19
Motivation
A large scale buoy can potentially replace 10% of world electricity demand
Buoy generators can conceivably produce power more cheaply than coal (4.5 cents/kWh), currently the cheapest source of energy
3/19
Methods
Wave motion rotational movement
Hydraulic pressure (water flow) to actuate hydraulic motors
or turbine
Wave motion translational movement
Linear generator: utilizing electric coil and magnetic shaft for
producing electric current
Use of dielectric elastomer
4/19
Previous Work
Linear generators
Permanent magnet linear
generator buoy, Rhinefrank, K. et
al. (USA, 2006)
Ocean Wave Energy Harvesting
Buoy for Sensors (2009)
•Utilization of singular anchored linear
generators
•Simplifies the overall mechanical
design and the device experiences low
mechanical wear
•Eliminating the complex and inefficient
process of converting the linear thrust
of the waves to rotational torque
5/19
Previous Work
Pelamis (2008), UK
As the waves move the joints up and down, hydraulic rams
move according to them, pumping high pressure oil to
hydraulic motors which drive electric generators
Near shore devices
•Agucadoura Wave Farm (Portugal)
http://www.pelamiswave.com/
6/19
Previous Work
Ocean Power Technologies (OPT)
The rising and falling of the waves offshore causes the buoy
to move freely up and down
The resultant mechanical stroking drives a rotational
electrical generator
http://www.oceanpowertechnologies.com/
7/19
Our Idea
The buoy motion dependent of
wave motion (by airbag or float)
The reciprocating translational
motion from wave generates
one directional rotational
motion
No need of rectification to convert
VAC to VDC
8/19
Implementation
Practical application of motion conversion concept
Linear rail and carriage provides the translational motion
The motor would utilize the rotational motion, by means of
pulleys to convert from translation to rotation
In order to ensure unidirectional rotation, a pair of clutches
are used, placed on the side of the generator
9/19
Implementation
Design of inner cylinder
The cylinder to engage in
continuous translational motion
when acted upon by the ocean
potential energy
Belt clamps allow the
translational motion of the
cylinder to provide torque for
driving the pulley
Each clamp on opposite side
Belt sit
clamp
10/19
Implementation
Assembly on the
outer cylinder
The outer cylinder
houses the pairs
of linear rails
A mounting base
for the generator
11/19
Implementation
Simulated Complete
Assembly
The complete assembly of all
part of design is shown to
accommodate intended motions
Assembly shows the location of
each cylinder relative to the
other, and the position of all
other components on each of
the cylinders
Pulley-clutch
subassembly
Belt sit clamp
12/19
Implementation
Prototype 1st ver.
Generator: 15V 2.4A, 3940 rpm max
Clutch
Generator
Belt on
Pulley
Forcing
Handle
Inner
Cylinder
Outer
Cylinder
13/19
Power Evaluation Study
Push-full force (≈2N)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
0 1 2 3 4 5 6
x 105
0
0.1
0.2
time (x10-5 sec)
vo
l (V
)
14/19
Power Evaluation Study
Push-full force (≈2N)
Trial 1 2 3 4 5 6 7 8 9 10 Avg
Mean VDC (mV)
27.1 30.5 26.0 27.5 28.4 25.4 31.5 31.9 32.2 32.2 29.3
Mean Power (mW)
0.490 0.621 0.450 0.504 0.538 0.431 0.660 0.677 0.690 0.693 0.575
Peak VDC (mV)
163.2 174.7 176.4 205.3 195.8 204.0 196.1 184.9 228.3 157.3 188.6
Peak Power (mW)
17.8 20.4 20.7 28.1 25.6 27.7 25.6 22.8 34.8 16.5 24.0
15/19
Realistic Illustration
The result from the
prototype indicates the
feasibility of the design for
suggested application
Set-up example in pelagic
ocean area
This will provide solution for
continuous mission fulfillment
without accessibility to power
supply
Buoy
system
Connection
cables
Sea bed
16/19
Conclusion
A wave energy harvesting device with new
mechanical rectifier presented
Generates electrical energy from bi-directional reciprocating
motion as found in ocean wave to one directional rotational
motion
Belt clamps on opposite locations
Use of pair of clutch-pulley assembly
No need of electrical rectification
Output power 0.58mW
17/19
Future Works
More smooth motion
System tolerance minimization (3D printed ABS metal)
•Minimization of backlash
High quality bearing and belt
Comparison with electrical rectification
Improving durability
Wave testing
Waterproof design
Water basin testing
Power estimation for possible future applications
18/19
Acknowledgement
This research was supported by UMBC
Undergraduate Research Assistantship Support
(URAS, 2015).
Thank You!