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Miniscale Energy
Generation
Peter C. Gravelle, Borce Gorevski, Nick Ieva
Sponsor/Advisor: Dr. S. Lyshevski,
Electrical Engineering Department
Objective

To design and prototype a self-sufficient
miniscale generator
Goals
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Sub-5 cm3 volume
At least 0.1 W/cm3
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Waterwheel with permanent magnets
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We can probably exceed these greatly
Salt-water resistant (nautical/sharks)
Output voltage greater than 7V
Design Choices
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Generator
Wheel
 Magnets
 Windings
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Electronics
Energy storage
 Energy harvesting circuitry
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Housing
Wheel
Technical Details: Wheel
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Diameter of wheel: <2.5cm
Material: plastic
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Teflon? Durlen? HDPE? Nylon?
Magnets mounted on wheel
Magnets

SmCo
Corrosion resistant
 More expensive
 Weaker

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NdFeB
Very highly magnetic
 Low cost
 Very corrodible

Magnet Feasibility Graph
Feasibility Chart: Magnets
T1
3
2
1
E1
T2
NdFeB
SmCo
0
T4
T3
Humidity Resistance
Field Strength
Salt Environment
Small Pieces
Cost
T1
T2
T3
T4
E1
sum
NdFeB
1
3
1
3
3
11
SmCo
3
2
3
2
1
11
We picked NdFeB

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Dr. Lyshevski told us to 
Cheaper
Stronger
More easily machined into small parts

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Arcs required for our design
Corrosion can be dealt with by plastic coating
Right now looking at ring magnets with OD = 0.625”,
ID = 0.250”, and thickness of either 0.250” or 0.375”
Field Simulation for N35 grade
NdFeB (3mm dia, 1mm thick disc)
6.942e-001 : >7.279e-001
6.605e-001 : 6.942e-001
6.268e-001 : 6.605e-001
5.931e-001 : 6.268e-001
5.594e-001 : 5.931e-001
5.257e-001 : 5.594e-001
4.920e-001 : 5.257e-001
4.583e-001 : 4.920e-001
4.246e-001 : 4.583e-001
3.909e-001 : 4.246e-001
3.572e-001 : 3.909e-001
3.235e-001 : 3.572e-001
2.898e-001 : 3.235e-001
2.561e-001 : 2.898e-001
2.224e-001 : 2.561e-001
1.887e-001 : 2.224e-001
1.550e-001 : 1.887e-001
1.213e-001 : 1.550e-001
8.759e-002 : 1.213e-001
<5.389e-002 : 8.759e-002
Density Plot: |B|, Tesla
Windings

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Dr. Lyshevski has windings that we can use
We also found several websites, should we need
different windings
Axial motor winding pattern

Pattern will be made of plastic (see below)
Energy Storage
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Batteries

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High energy density
Limited charge cycles
Lower voltage
Temperature sensitivity
Supercapacitors
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High (but lower than batteries) energy density
Unlimited charge cycles
Higher voltage
Temperature insensitive ( -40C to 70C)
Batteries vs. Supercapacitors
Feasibility Assessment: Energy Storage
T1
3
E1
Li-ion Batteries
Supercapacitors
T2
2
1
S1
T3
0
T8
T4
T7
T5
T6
Energy
Density
Power
Density
T1
Li-ion Batteries
Supercapacitors
Life
Charging
Discharging
Circuit
Operating
Temp
Self-Discharge
H2O
Safety
Cost
T4
T5
T6
T7
T8
S1
E1
sum
1
1
1
1
2
3
1
1
15
3
3
3
3
3
1
3
1
25
Size
Max
Voltage
T2
T3
3
1
2
3
We picked Supercapacitors
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Smaller size
Greater cycle life
Will not ignite in water
Greater power density
High voltage density
But which supercapacitor?
Capacitance
Max
Voltage
Nom.
Voltage
Max
Current
Size
ESR
T1
T2
T3
T4
T5
T6
sum
HPSK0G103ZL (flat)
1
4
3
5
4
1
18
FS0H223Z (cyl)
1
5
5
3
5
2
21
FS0H473Z (cyl)
2
5
5
3
5
2
22
FT0H104Z (cyl)
3
5
5
3
5
3
24
FT0H224Z (cyl)
3
5
5
3
4
3
23
FA0H473Z (cyl)
2
5
5
5
3
3
23
FE0H473Z (cyl)
2
5
5
5
4
3
24
FE0H104Z (cyl)
3
5
5
5
3
4
25
PC5 (flat)
5
2
2
5
2
5
21
PC5-5 (flat)
4
5
4
5
0
5
23
GW 2 13D (flat)
4
5
4
5
1
5
24
B49100A1503Q000 (flat)
4
2
1
4
2
5
18
B49100B1104Q000 (flat)
5
2
1
5
1
5
19
So, which one is it?

Further investigation is needed to determine the
relative importance of our conditions
Size vs. Voltage
 Size vs. Current
 The smaller the size, the better!
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Energy Harvesting: AC-DC

Standard bridge rectifier
Harvesting Circuitry: Voltage
Regulation
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Switched-capacitor DC-DC voltage converter
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Efficiency: ~90%
Doubles input voltage
Max output current: 300mA
Step-up (boost) converter
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Also has an efficiency of ~90%

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Depends entirely on ESR values for capacitors and resistors
But needs more parts (volume, cost)
Adjustable output voltage/current
Max output current: 1A