Wireless Power Final Presentation
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Transcript of Wireless Power Final Presentation
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10-12-2007 MDP Group 1 Wireless Power Supply 1
Wireless Power Supply
Final PresentationSpeakers: Ralph Leijenaar
Ren van Bussel
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10-12-2007 MDP Group 1 Wireless Power Supply 2
Outline
Introduction
Choice of applications
BikeLights
PowerSaver
Conclusion
Questions
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10-12-2007 MDP Group 1 Wireless Power Supply 3
Choice of applications
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All applications
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Criteria
Criteria for applications:
User-friendly, easily standardizedTechnically possible to make nowEconomically feasible, compete with current technologySustainableHealth and environment safe, FCC compliant
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Criteria
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Bike lights
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DesignHub dynamo powers 5.8 GHz transmitter
Hub dynamo delivers 3 W of power
LED lights:Consisting of 3 to 4 LEDsComplete back surface is 5.8 GHz rectenna
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PowerReceived power P r calculated with Friis equation (front):
Average LED light power consumption60-80m A
3V circuit: 180-240mW
Wireless powering without batteries not feasible usefor recharging batteries
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Front LED light distance r = 30 cmRectenna conversion efficiency = 83%Wavelength
P t (transmitted power) = 3 W A
p,t(transmitter surface area) = 5 cm2
A p,r (receiver surface area) = 40 cm2(back surface of LED light)
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Health hazards
Most problematic effect of RF radiation on the body:heating effect
Measured by:Specific Absorption Rate (S AR)(power absorbed by the body per unit mass)
Applications have to comply with S AR limits
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Health hazards: S AR calculation
Male human 1070 kg/m3
Speed of light c = 310 8 m/spermittivity of free space is 0 = 8.85 1012 F/m.
and r tissue and frequency dependant, calculation: = 3.87 S/m
r = 36.9
BikeLights:average distance to the body r = 0.5 mdistance to nearest body part (foot/leg) r = 0.3 mInput power P = 3 W
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Health hazards: BikeLight S AR values
Whole-body S AR (averaged distance) = 0.035 W/kgLocal SAR (foot/leg) = 0.098 W/kg
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EnvironmentAssuming the batteries are only recharged while the LED light itself is
in use an estimation of the ratio of the time the LED lights can beused with and without recharging can be made ( T r):
Assuming a power usage of 60m A and recharging with 1,72m A (5.17mW / 3V):
Increase of 3%Charge batteries when lights are off better increaseNo real environmental benefits
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Economic aspects
With respect to wired lighting using a normal dynamo
Hub dynamo more expensive:
Normal dynamo: starting at 10,- to 25,-Hub dynamo: starting at 30,- to 40,-
Transmitter and rectenna costs
Rechargeable batteries used:With respect to normal LED lighting no extra costsWith respect to wired lighting only costs of 1 set of batteries
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Bike lights: conclusion
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Criteria Points before Points after
User friendliness 9 6
Technical feasibility 8 5
Economical feasibility 9 6
Sustainability 9 6Health 8 8
Total 43 31
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Future improvements
Main goals:
Increase power received by LED lights
Reduce power needed by LED lights
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Standby saver
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Design
Antenna in the remote controlRadio waves of 5.8 GHzRectenna in TV switches relay
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Health hazards: S AR
Again, heating and S AR important
, , c, 0 , and r are the same as the bike lights, r andP are differentDifferences:
average distance to the body r = 0.4 mdistance to nearest body part (thumb/hand) r = 0.02 mInput power P = 12 W
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Health hazards, calculation
The SAR is calculated averaged over time:Whole-body S AR (averaged distance) = 0.00031 W/kgLocal SAR (hand) = 0.12 W/kgUsed just one time in six minutes
Directivity, probably lower S AR
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Environment
Standby functions: 5% of power used in developedcountriesSuitable for TV, not convenient for VCRTVs: average 21 kWh/year per householdRemote uses batteries, but surprisingly littleVery difficult to implement in existing devices
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Economic aspects
Saves electricity, thus money 4,20 per year per household
More batteries used, not significantTV more expensive: remote, antennas, more materialsCould be sold as environment saving idea
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Conclusions
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Criteria Points before Points after
User friendliness 8 8
Technical feasibility 8 7
Economical feasibility 9 8
Sustainability 9 8Health 8 8
Total 43 39
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Future improvements &Recommendations
Reduce power needed to switch the relayLess power = less batteries
For existing devices a seperate standby saver could beused between the plug and socket
The converting of a half-second-long radio beam to amillisecond pulse is idealised
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Conclusion bike lights
Impossible to use wireless power for bike lightsCharging is an option
SAR calculations show no health hazardsLittle environmental impact
Batteries still needed
Material costs higher than existing lights
Recommendations:Increase the antenna gain & use a second dynamo for the backlightImprove LED efficiency
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Conclusion standby saverPossible using a frequency of 5.8 GHzSAR within limits
Assuming it is not used often in six minutes
Environment: 5% of power used in developed countriesis standby power
Not suited for all applications
For the same reason: not a lot of money saved perhousehold
4,20
Recommendations:Reduce power to switch relay, use a separate device forexisting devices, look into the conversion
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Questions?
?10-12-2007 MDP Group 1 Wireless Power Supply