Wireless Power Final Presentation

8/8/2019 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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Outline

Introduction

Choice of applications

BikeLights

PowerSaver

Conclusion

Questions


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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


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


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


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

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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

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Wireless Power Final Presentation

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