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!