1. 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

2. 1/19
Outline
 Literature survey on Energy Harvesting Buoy
 Our Idea
 Prototyping
 Power Estimation Study
 Conclusion
Future Works

3. 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

4. 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

5. 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

6. 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/

7. 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/

8. 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

9. 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

10. 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

11. 10/19
Implementation
 Assembly on the
outer cylinder
The outer cylinder
houses the pairs
of linear rails
A mounting base
for the generator

12. 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

13. 12/19
Implementation
 Prototype 1st ver.
Generator: 15V 2.4A, 3940 rpm max
Clutch
Generator
Belt on
Pulley
Forcing
Handle
Inner
Cylinder
Outer
Cylinder

14. 13/19
Power Evaluation Study
 Push-full force (≈2N)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)
0 1 2 3 4 5 6
x 10
5
0
0.1
0.2
time (x10-5 sec)
vol(V)

15. 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

16. 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

17. 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

18. 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

19. 18/19
Acknowledgement
 This research was supported by UMBC
Undergraduate Research Assistantship Support
(URAS, 2015).

20. Thank You!