Transcript Generating Unit - Research

Third World Electric Generator: Electricity from Excess Heat
Sung Hoon Bae1, Daniel Rim2, Chris Zachara2
Advisor: David Owens3
Dept. of 1Biomedical, 2Chemical Engineering, 3Owen Graduate School of Management, Vanderbilt University, Nashville, TN
Introduction
Design Components
Design Performance (continued)
Problem Statement
• Third world countries, though some of the most populated
Generating Unit
• TEG (TEC1-12706)
Storage Unit
• Not enough power was generated to charge the batteries
• Unrealistic theoretical charging time with given performance
regions on earth, suffer from abysmal electricity distribution
• Manure-to-biogas digesters are a great source of renewable fuel
for families off the grid, but use of biogas is largely inefficient
Design Approach
• Utilize excess heat wasted by gas appliances
• Stored electricity is needed for its portability and ease of use
Thermoelectric Generation (TEG)
• Temperature difference creates electric potential described by:
V  (SB  S A )(T2  T1 ) (Eq.1),
where S A and S B are Seebeck coefficients and T1 and T2 are
temperatures at junctions (Figure 1)
• Typical application is thermoelectric cooling (TEC)
- Theoretically reversible process
• Specially doped semiconductors (ex. Bismuth Telluride)
• Current technology: only 10% energy efficient
- Vmax = 16.4V; Qmax = 57W
• Heat sink
• Thermal grease (Arctic Silver)
- Maximizes contact area
Storage Unit
• NiMH Battery (Sanyo Electric)
Figure 3 Overall design of the prototype
- Voltage = 1.2V
- Capacity = 2000mAh
Cost Analysis
• Cost of the prototype = 57.86$/unit
• Battery life is approximately 4 years (limiting factor)
• Visible monetary benefit in 6 years at most
• Controllers
- Voltage regulator
- Charging controller
• LED (Figure 4)
- Vforward = 2.4V; Iforward = 20mA
- R = 1.8Ohms
- Luminous = 6000mcd
Figure 4 Circuit diagram of LED component
Generating Unit
• Short-term drift and long-term drift
• Characterized actual specifications
• Heat source: boiling water (100°C)
Storage Unit
• Monitored charging process over time
Design Criteria
•
•
•
•
•
•
Must be easy to use and require no training
Must be portable for flexible uses
Must be economically feasible
No additional energy should be used to generate electricity
Should effectively use excess heat to generate electricity
Charging process should be safely and automatically monitored
2.5
2
1.5
1
0.5
0
20
40
60
80
100
120
Time (sec)
140
2 NiMH Batteries
14.99
Thermal Grease
0.87
6 LED lights
6.00
Miscelleneous
6.50
Total
57.86
Table 4 Expected savings by usage
years for different energy consumptions
Future Directions
1.5
1
160
180
0
0
500
1000
1500
2000
2500
3000
Time (sec)
Figure 6 Short-term (left) and long-term (right) drift measurements of prototype I
(blue) and prototype II (red)
• Prototype I withstood ~30 minutes of operating period
• Not enough power was generated for both prototypes
Type
I
II
24.00
2
0.5
0
Heat sink
processes are not completely reversible
• Current prototype cannot provide sufficient power to charge 2
NiMH batteries or light 6 LED lights
• Failed to meet the required product specifications under the
price constraints (mainly due to quality of TEG)
Prototype I
Prototype II
Prototype I
Prototype II
Amplitude (V)
heat
• Power 6 LED lights for 2 hours per day
• Incorporate a battery charging system for portable electricity
• Achieve low selling price, ideally between $40 and $60
5.50
• Thermoelectric cooling (TEC) and thermoelectric generating
3
3
Amplitude (V)
• Design a household scale electric generator
• Integrate with biogas systems
• Utilize thermoelectric technology to recover energy from excess
TEG
Conclusions
Generating Unit (Figure 6 and Table 1)
• Steady electric generation after ~50 seconds
• Higher electric generation from prototype I (~2.5V)
2.5
Unit Price ($/unit)
Average Money Spent for Lighting
Year 1.00$/mo 1.50$/mo 2.00$/mo
1
-45.86
-39.86
-33.86
2
-33.86
-21.86
-9.86
3
-21.86
-3.86
14.14
4
-9.86
14.14
38.14
5
-3.36
26.64
56.64
6
8.64
44.64
80.64
7
20.64
62.64
104.64
8
32.64
80.64
128.64
Figure 5 Experiment set up
Design Performance
Project Goals
Component
Table 3 Material cost of the prototype I
without economic scale
Figure 2 Discharging graph of a NiMH battery
Nickel Metal Hydride (NiMH) Battery
• Relatively constant discharged voltage (Figure 2)
• More current compared to other batteries
• Various capacities available
4 hours
720
36.0
66.7
Table 2 Required charging time for each various usages hours (1,2,3, and 4)
System Verification
Figure 1 Diagram
showing Seebeck effect
Energy used (mAh)
% Capacity Used
Expected Charging Time (hrs)
1 hour
180
9.0
16.7
Usage Hours
2 hours 3 hours
360
540
18.0
27.0
33.3
50.0
Rise Time Falling Time Avg. Amp. Power Generated Power Needed*
47 sec
30 min
2.50 V
6.25 mW
500 mW
46 sec
11 min
0.62 V
0.38 mW
500 mW
Table 1 Various specifications of prototypes I and II. *To charge NiMH batteries.
• Further investigate ways to increase output voltage and power
• Experiment with larger TEG’s and TEG’s in series
• Analyze performance of various TEG’s from multiple
manufacturers
• Investigate advanced cooling methods, like fluid or fan cooling
• Finalize method of implementation and develop housing.
• Assess feasibility of market success
Acknowledgements
We would like to thank the Dr. King, Dr. Bonds, Dr. Walker, Alex
Makowski, Kurt Hogan, Stephen Songy, and the ME mechanics
shop for making this project possible.