a human power conversion system based on children’s play PAPER

8/2/2019 a human power conversion system based on children’s play PAPER

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A Human Power Conversion System Based onChildren’s Play

Shunmugham R. PandianDepartment of Electrical Engineering and Computer Science

Tulane University

New Orleans, LA 70118

Abstract -A new method is proposed for harnessing of human

power based on children's play in playgrounds and publicplaces, on devices such as the seesaw, merry-go-round, andswing. When large numbers of children play in a playground,part of the power of their play can be usefully harnessedresulting in significant energy storage. This stored energy canthen be converted to electricity for powering basic, low-powerappliances such as lights, fans, communications equipment, andso on. The method provides a low-cost, low-resource means of generation of electricity, especially for use in developingcountries. The paper discusses the basic theory behind themethod. Results of experiments on a laboratory prototype

compressed air human power conversion system using a teeter-totter are presented to illustrate the practical effectiveness of theproposed method.

I. INTRODUCTION

Energy is the driving force of modern societies, andgeneration and utilization of energy are essential for socio-economic development. Per-capita energy consumptionlevels are often considered a good measure of economicdevelopment. In recent years, energy scarcity has become aserious problem due to depletion of non-renewable energysources, increasing population, globalization of energy-intensive economic development, environmental pollution,

and global warming [1], [2].

In this context, the field of renewable energy represents anew frontier for the academic and research community, dueto the following factors:

• Depletion or unreliability of non-renewable energysources, e.g., oil

• Environmental pollution, e.g., due to coal use

• Needs of increasing population, especially inresource-scarce developing countries

• Global Warming/Climate changes

• New applications in modern, high-tech settings – e.g., wearable computing and portable consumer electronics

While in developed countries the energy problem is one of short-term scarcity or optimum use, an estimated 40% of theworld's population – or, 2 billion people mainly in the lessdeveloped countries – do not have even have access toelectricity. Moreover, this number is expected to double bythe year 2050.

The reasons for this limited access to electricity indeveloping countries are the lack of energy sources such ascoal, oil, or nuclear energy, and – even where such sourcesexist – the lack of expensive capital to exploit existingresources. While the costs of renewable energy sources suchas solar and wind energy are falling gradually, thesetechnologies are still far too expensive for developingcountries, where about half the population has incomes of less than two dollars a day.

In recent years, there have been many interesting

developments in the field of human power conversion. In the present paper, a method of harnessing the power of children's play in playgrounds and public places, on devices such as theseesaw, merry-go-round, and swing is proposed.

When large numbers of children play in a school playground, part of the power of their play can usefully be harnessedresulting in significant energy storage. This stored energy canthen be converted to electricity for powering basic, low- power appliances in the school such as lights, fans,communications equipment, and so on. The method providesa low-cost, low-resource means of generation of auxiliaryelectric power, especially for use in developing countries.

In the proposed method, compressed air devices are used for the conversion and storage of human power. Use of compressed air is explosion-proof and fire-proof and opentubing results simply in air leakage. The lower efficiency of the resulting system is compensated by the simplicity, safety,and low-cost of operation of the pneumatic system.

The compressed air will be stored in storage tanks close tothe point of use, and used to power a pneumatic actuator suchas cylinder or air motor, which will in turn move an electricgenerator to produce electricity. The electricity can be storedin batteries, and used to power dc-operated lights andappliances or to power ac-operated appliances through the

use of inverters and power control circuitry.

II. TRENDS IN HUMAN POWER CONVERSION

Human power was perhaps the earliest source of energyknown to mankind [3]. Its first uses were in tool-making, plowing, rowing boat, and so on. Mechanized uses of human power were achieved in the form of hand cranking by theRomans. However, pedaling which is a simpler and less

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tiresome means of human power conversion did not comeabout until the 19th century with the invention of the bicycle.Human power was widely used in the developed countries inthe late 19th and early 20th centuries for purposes such asirrigation, operating machinery, and as a source of electricityfor watching/listening to television and radio. In manydeveloping countries, human power is still widely used inagriculture, industry, and services.

Interest in human power conversion declined in the early 20th century due to several technological developments:

• Availability of cheap, abundant electrical energy

• Use of compact, powerful, and versatile electricmotors and lights

• Availability of cheap, disposable batteries for portable use

In recent years, human power conversion is making acomeback due to a variety of economic, environmental, andtechnological factors:

• Applications in less-developed countries and remotelocations of developed countries (e.g., camping)

• Use in portable computing, where progress in battery technology lags behind developments inlaptop PCs

• Use in wearable computing and communicationdevices, where absence of batteries or usableenergy in remote locations such as battle fieldshinders their continuous use

• Energy shortage and high cost of solar/wind power

• Use in emergency situations, e.g., earthquakes andhurricanes

• Energy conservation – e.g., to minimize energy

requirements in power assist devices for elderly anddisabled

• Environment friendly – batteries are energy-intensive to produce and are non-biodegradable

• Advances in actuators, materials, and energy storagetechniques

• Technological challenges – e.g., human-poweredflight, with spin-off benefits

Trevor Baylis's (re)invention of the clock work radiocontributed immensely to this trend [4]. Various new products are based on the use of human power conversion for operating flash lights, cell phone battery chargers, wristwatches, energy-scavenging shoes for wearable electronics[5], power-harvesting shoes for soldiers [6], laptop andwearable computers [7], children's toys [8], and so on.

Major technological developments in human power conversion were brought about by the research of PaulMacready – named as the Engineer of the Century, by ASME – and his group in the area of human powered flight (e.g.,[9]). This research led to new developments in the use of light-weight composite materials, aerodynamic vehicle

design, high-power batteries, high-strength electric motorsand generators, and so on.

TABLE I

POWER OUTPUTS OF COMMON HUMAN ACTIVITIES

Activity Maximum human power (W)

Pushing button 0.64Squeezing handle 12Rotating crank 28Riding bike > 100

Macready’s research also resulted in commercialization of new products such as light reconnaissance aircraft, solar powered flight, electric and hybrid vehicles, and electric power-assist bicycles.

Human power conversion can be used to reduce the need for large portable energy storage devices in orthosis and assistivetechnology systems (e.g., [10]). Researchers in Japan areexploring the potential of human power for rescue situationssuch as earthquakes [11].

The significant potential of human power as an energy sourcecan be realized from the fact that daily average humancalorific consumption is about 2500 kcal.

Since1 cal = 4.184 J

=> 2500 kcal = 10.5 MJ ≈ 3kWhr

This is equivalent to the energy stored in 1050 AA alkaline batteries [7]. Eating a hamburger gives us the energy of morethan 100 AA batteries.

Typical power outputs of some common human activities are

listed in Table I [12]. However, day-to-day human activitiesalso consume large amounts of energy, as shown in Table II[7]. Therefore, the net energy available for conversion isquite limited in practice.

Table III lists the typical power requirements of commonhousehold electrical and electronic appliances. From theseconsiderations of human power, it is clear why most human power conversion systems proposed so far are limited to powering consumer electronics devices, e.g., portable radiosand flashlights.

From the discussions so far, we may conclude that (i) thehuman power conversion-based systems developed so far are

mostly based on harnessing individual human power, (ii)therefore they are mainly limited to powering low-power consumer electronics devices, and (iii) the existing systemsare based on exertion of deliberate effort by individuals.

TABLE II

ENERGY CONSUMPTION FOR HUMAN ACTIVITIES

Activity Energy consumed (W

Sleeping 81

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Sitting 116Swimming 582Sprinting 1630

TABLE III

POWER REQUIREMENTS FOR DOMESTIC APPLIANCES

Appliance Power consumption

Portable FM radio 30 mWWalkman (play mode) 60 mW

Flashlight 4 WLaptop PC 10 WFluorescent light 10-30 WDesk fan 25-50 WTV (20 in) 50 WWater pump 100 WPressure cooker 500 WMicrowave oven 1000 W

It is clear that the systems proposed in literature are unsuitedto power basic domestic appliances such as fluorescent lights,desk fans, television sets, or communications equipment(e.g., fax machines). These are among the basic needs of amajority of the population in developing countries.

In the present research, we propose harnessing the humanmuscle power of children playing in public spaces such asschool playgrounds, on equipment such as teeter totters,swings, and merry-go-rounds. Such an energy conversion is playful and hence does not require deliberate effort.

For human power conversion systems to be useful in thecontext of developing countries, several constraints need to be considered: low-cost, low-resource and limited-skillsrequirements, low-maintenance, safety and comfort tohumans, and environment-friendliness.

The low-cost requirement also imposes a trade-off betweencost and efficiency of the energy conversion system.

Improving the efficiency of the conversion system – as isoften essential in the case of individual human power conversion – generally would result in increased cost of theoverall system. In the case of several children playing on playground equipment, power is produced as a byproduct .Therefore, a low-cost system can be designed andimplemented without seriously affecting efficiency, since alarge number of children are involved in the play.

III. PLAYFUL ENERGY CONVERSION

Human power conversion is easily achieved from children’splay under conditions where the children are static relative to

Figure 1. Types of children’s playground equipment

the moving playground mechanism, such as seesaw, swing,and merry-go-round (Fig. 1). Where the children are in adynamic state relative to a static mechanism (e.g., slide) itwill be difficult to employ cost-effective human powerconversion techniques due to considerations of safety andsimplicity.

A variety of mechanisms are used for conversion of humanpower to usable electrical or mechanical energy: springs,hydraulic components, electric generators, piezoelectrics,compressed air systems, flywheels, and so on [7]. The factorsaffecting the choice of the most suitable conversionmechanism are similar to those for the general energyconversion problem [13].

We consider the use of pneumatic cylinders as ideal for play-based human power conversion due to the following reasons[14]:

• Low-cost and easy availability of pneumatic

actuators, e.g., in the form of the bicycle pump• Ease of operation of pneumatic systems

• Simplicity of design and ease of maintenance

• High power-to-weight and power-to-size ratios

• Shock- and explosion-proof

• Ability to withstand overloading, rapid reversals,and continuous stalling

• Safe dissipation of heat

• Resistance to heat, humidity, and hazardousatmosphere

The main limitations of compressed air systems for energyconversion include their low efficiency, especially in

comparison with electric energy conversion systems, and thevery low energy storage density of compressed air. However,these disadvantages are outweighed by the above-mentionedadvantages, especially low-cost, in the context of play-basedhuman power conversion. The compressibility of air alsomakes pneumatic systems a preferred machine interface tohumans, e.g., rehabilitation robotics [10].

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Figure 2. Compressed air generation from teeter-totter

The basic principle of the new method is illustrated in Fig. 2.For simplicity, we limit our discussion to power conversion based on a seesaw. The cases of a swing and a merry-go-around can be considered similarly.

The typical playground seesaw is often supplied with hardcylindrical helical springs to smoothen the actions of the

seesaw mechanism. In the present study, instead of thesprings we employ two pneumatic cylinders on the two sidesof the seesaw. To prevent any accidents and injuries to players’ limbs from the moving pistons, we can provide a bellows-type flexible sheath between the bottom of seesawand the top of the cylinder. The outer bodies of the cylinderswill get heated up due to the compression of air inside. Thiswould require shielding of the outer bodies too (not shownhere).

Figure 2 shows the process of compression of air and itstransmission to the power generator stage. For improvedcompression rate, we consider the case of double actingcylinders. The atmospheric air enters the cylinder portsalternately through check valves. The reciprocating verticalmotion of the piston of the cylinder under the motion of theseesaw results in compressed air being outputted throughcheck valves via the cylinder ports, to the compressed air pipeline.

Fig. 3 illustrates the generation of electric power from thecompressed air. The compressed air from the pipeline isstored in an air tank. Essential parts of the air tank, such as pressure gage, pressure release valve, etc are not shown herefor simplicity.

When the compressed air inside the air tank reaches a set

pressure level, the on-off valve is opened. FRL stands for filter-regulator-lubricator unit. If the pressure of the stored air is low due to pressure drop along a long pipeline, then an air booster unit can be used to reduce the volume and increasethe pressure of the air to the power generator unit.

Figure 3. Electricity generation from compressed air

The compressed air is used to drive an air engine or air motor. An electromagnetic generator is coupled to the shaftof the air motor/engine, resulting in conversion of thecompressed air energy to electric power. The generated

electricity can be stored in batteries as a source of back-up or auxiliary power.

In general, air motors are very expensive compared to air cylinders and moreover require extensive gearing. Therefore,to reduce cost we can simply use the compressed air toactuate a cylinder which in turn can be used in a slider-crank mechanism to move the electric motor.

In the case of harnessing muscle power of children playingon a swing, a pneumatic rotary actuator can be used as thecompression mechanism. Here again, industry-grade rotaryactuators are quite expensive. Therefore, a pinion-and-rack gearing mechanism can be used along with a double actingcylinder for compression of air. Swings are usually providedwith flexible chains, therefore the extraction of the swingforce for air compression will only be partial.

Air motors could be used in the case of merry-go-rounds for compression. Here too, due to cost considerations it will be preferable to use crank-slider mechanism (as used in positivedisplacement reciprocating piston-type compressors) with anair cylinder.

IV. ANALYSIS OF POWER CONVERSION

The motion of the endpoints of the seesaw beam about thecenter of the seesaw is curvilinear. Due to the cylinders beingaffixed vertically to ground, the bidirectional motion of the pistons is linear.

Neglecting the mass of the seesaw beam, let the masses of the children on the two sides be denoted as M 1 and M 2. If thevertical displacement of the children is given as h, and theaverage acceleration is denoted as a, then the mechanicalenergy expended by the children’s play during the stroke is

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( ) ha M M W in 21 +=

This mechanical energy is converted into the energy of compressed air stored in the air tanks.

Neglecting the heat transfer to the container, we can assumethe compression of air to be polytropic, i.e., betweenisothermal and adiabatic phases, with a related rise in

temperature [14].

The work done for one cycle of compression is given by

−

−=

−

11

1

1

211

γ

γ

γ

γ

P

P V P W

where P1 is the initial pressure (absolute), V1 is the air tank volume, and P2 is the final pressure. W is the work done (in

joules) by the compression of air, and γ is the ratio of specific

heats. γ is assumed to lie between 1.3 and 1.4 for air for polytropic processes. Then, the above equation becomes

−

= 15.3

29.0

1

211

P

P V P W

for γ =1.4. The air in the tanks is initially at the atmospheric pressure.

From the above equations, knowing the air tank volume andthe final pressure of air, we can calculate the work potentialof the compressed air stored in the tank.

In the next step, when the compressed air is released toactuate the air motor/engine, the total boundary work done bythe expanding gas is given by [15]

∫=

2

1

V

V

PdV W

where the tank volume is V1, and the air escapes into theatmosphere finally occupying some volume V2.

The pressures and volumes are related by

1

2

112

−

=

γ

V V V V

and during expansion of air, sinceγ γ

2211 V P V P = , we have

γ

=

V

V P P 1

1

The work done by the expanding air is then given by

−

−=

−

γ

γ

γ

1

1

211 1

1

1

P

P V P W

where P2 is the pressure at release.

The work done by the expanding air is used to move the pneumatic actuator, which is coupled to an electric generator (usually, a dc motor used as a dc generator). Therefore, thereare energy losses due to friction in both the pneumatic andelectric actuators, as well as their finite efficiencies.

V. A PROTOTYPE TEETER-TOTTER POWER CONVERTER

Figure 4. Prototype teeter-totter play power converter

Figure 5. Pneumatic-to-electric power converters

To illustrate the practical effectiveness of the proposedhuman power conversion method, a laboratory prototypeusing a teeter-totter as play equipment has been designed andtested with children playing and producing power. A photograph of the actual system is shown in Fig. 4.

Due to ease of installation in the laboratory, the power conversion system was installed on a large wooden board,The double-acting pneumatic cylinders (Bimba, SR0920-DM, with 20 in stroke, 1-1/16 in bore stainless rod) were

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0

5000

10000

15000

20000

25000

30000

35000

40000

43 53 70 87

Children-pair weight (kg)

E n e r g y ; i / p

& o / p ( J )

0

2

4

6

8

10

12

14

E f f i c i e n

c y ( % )

Input Output Efficiency

installed at an angle of 45 degrees on the two edges of theseesaw (overall dimensions: 82-1/8”L x 20”W x 25-5/8”H;net weight: 37.5 lb). Check valves were used to direct thecompressed air into two 1.5 gallon interconnected air tanks.1/4 in PVC tubing was used as the air pipeline. Pressuregages were used to monitor the air pressure in the tanks.

Figure 6. Construction of air engine-based generator

Figure 7. Construction of inflator-based generator

We have built and tested three types of systems to convert theenergy of the compressed air into electric energy:

• Direct coupling of an air motor to a dc motor/generator, as shown in the foreground of Fig. 4.

• Coupling of an air engine to a dc motor fitted with aflywheel

• Retrofitting of a commercial dc-operatedcompressor to act as a pneumatic-to-electric energyconverter

In the first case, a Gast model 1AM-NRV-63A, 15:1 gear ratio, air motor with max speed 350 rpm, was coupled to aPittman 24 V DC motor with 5.9:1 gear ratio. We found thatthe efficiency of this system was quite low, due to the largefriction of air motors [16].

In the second case, we coupled the air pressure engine of anAir Hog air pressure plane system (from Spin Master Toys)to a Mabuchi dc motor for RC airplanes. The enginespecifications were 0.046 cu. in, torque 2 in. oz. @ 4000 rpm@ 80 psi (Fig. 5, left).

In the last case, a Campbell Hausfeld 12 V dc inflator (300psi) was modified using a three-way valve (Mac 1111-A-011) to act as air -to-electric power converter (Fig. 5, right).

Figure 8. Results of seesaw-based power conversion

The details of construction of the air-engine based and

inflator-based power generators are shown in Fig. 6 and Fig.7respectively.

The electricity generated was used to directly power threedirect current appliances simultaneously: a 6 inch, 4 wattfluorescent tube light, a low-power music player, and a two-

blade fan powered by a small hobby dc motor .

Fig. 8 shows a summary of results of trial runs when a few pairs of children played on the seesaw.

In this figure, the input energy represents the totalmechanical energy expended by the children-pair for theduration of play (3 minutes). It was calculated based on the

average number of strokes (35-40/min), the average strokelength (30-40 cm), and the children-pair weight. The teeter-totter beam mass was neglected.

The output energy represents the work potential of compressed air in the tanks (total volume of compressed air tanks: 3 gallons). The compressed air pressure varied fromabout 30 to 55 psi (g), depending on the weight and timing of trial.

The energy of compressed air in the tank is converted by the pneumatic-to-electric power converters, and the electricity produced is used to power the appliances. Of the threeconverters developed, the air pressure engine was the most

efficient, and the air motor-based one was the least efficient.

Fig. 9 shows the results when the three gallon tank compressed air at 50 psig (data set 4 in Fig. 6) was used to

power the fluorescent light, using the air pressure engineconverter. The total electric energy expended on the load is about 550 J. This represents a pneumatic-to-electric energyconversion efficiency of 16.7%, and overall systemefficiency (from the mechanical play energy to final payloadenergy) of 1.6%.

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The above system efficiency is comparable to that of shoe- based power converters reported in literature. Theseconverters typically produce about 1 W power output fromthe human walking action involving energy expenditure of about 65 W.

In the prototype, for simplicity the compressed air from the

tank is not delivered to the air engine at a regulated pressure.Therefore, the power converter efficiency is reduced for smaller tanks due to rapid pressure drops.

For example, Fig. 9 also shows the case of a larger, 11 gallontank used with the air engine converter to power thefluorescent light and other loads. In this case, while the tank capacity is 3.6 times that of the smaller tank, the electricenergy output is 5.5 times as high. At this rate, two children

playing on a seesaw for three minutes could be expected to power a low-power electric appliance with 14 W for a minuteduration.

Figure 9. Air engine power conversion

VI. DISCUSSIONS

The proposed approach can be applied to power conversionusing swings, merry-go-rounds, aero bikes, etc., where thechild is stationary with respect to the playground equipment.The power output levels could be expected to be much higher with merry-go-rounds, where many children can play at thesame time.

Due to limitations of space and facilities, the laboratory prototype developed in this study has used small-sized power converters (air cylinders and electric motors), air tanks, andlow-efficiency payloads. Therefore, in a typical playgroundsituation where several children play at the same time ondifferent playground equipment, larger-sized componentscould be used resulting in higher-efficiency power conversion. Vertical installation of the air cylinders wouldalso significantly improve the energy efficiency.

For ease of implementation, industry-grade pneumaticcomponents such as cylinders and valves have been used inthe prototype. These components are generally designed tooperate at high pressures with low leakage, but consequentlyhave high friction. So, low-friction, low-pressure componentsmay be used for better efficiency. For example, in the field of robotic orthoses newer soft actuators such as rubber actuators

have been developed to meet similar requirements [10].Commercial bicycle pumps with built-in check valves toohave lower friction.

Electromechanical generators can of course be used withhigher efficiency [17]. However, cost and safety issues haveto be considered in this case. The cost-to-size and cost-to-

power ratios of electric actuators are quite high compared to pneumatic actuators. Moreover, hazards of electric shock may offset the higher efficiency of direct mechanical-to-electric power conversion. Further, electrical systems aremore expensive to weather-proof compared to pneumaticones.

Further research and development, and extensive field trialsare required to develop guidelines for optimum selection of component types and sizing, interfacing to playgroundequipment, safety and comfort issues, weather-proofing,noise, and so on. Locale-specific conditions may also play amajor role in the practical implementation of the power converters.

To reduce maintenance and improve the performance, it isnecessary to filter the air entering the compressing cylinders.This is particularly so because air in the playgroundatmosphere is dust-filled. However, coarse air filters may besufficient in most cases unlike in precision industrialoperation. In practice, trade-offs between cost of air filters

and cost of maintenance of low-cost cylinders may also beconsidered.

A beneficial side effect of the use of compressed air power converters in playgrounds is that the due to the use of thefilter unit, the outlet air from the system will be cleaner thanthe atmospheric air (cf. [18]). The injection of microscopicoil particles from the lubrication unit, however, may beconsidered negligible.

In addition to its use as a source of back-up power, the proposed system also can have the educational value of raising energy and environmental awareness, esp. amongchildren, in schools and museums.

Exercise bicycles have been investigated for nearly a centuryas a source of electricity generation, and their use for power generation by children in schools has also been suggested[19]. While such an approach has the advantage of harnessing a large portion of the pedaling power from thestationary bikes, it also has the limitation of requiringdeliberate effort.

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The use of children’s play has been used for irrigation inColumbia [20]. This approach uses expensive hydraulicactuators. More recently, in Laos a group of volunteer engineers have used pedal power conversion to generateelectricity for a village without electricity [21]. Thiselectricity has been used for providing access to telephonyand the Internet.

Collective human power conversion is an example of micro power generation schemes, which offer significant promisefor empowering individuals and local communities in bothdeveloped and developing countries. An example of thisapproach is a micro hydroelectric power generator reportedin [22]. In this work, a small, low-cost hydroelectricgenerator is used for harvesting micro power from river water flow, without need for construction of dams. Similar low-cost, downsized power generators from solar, wind, andother energy sources need the attention of researchers andeducators worldwide.

Ethical questions may be raised on the use of children for power generation. However, the power generated in the

proposed scheme is meant toward essential use in schoolsand other public places in developing countries, or for

purposes of education-cum-entertainment on energy-relatedtopics. Due to the relatively small amounts of power involved, the power generated itself has little commercialvalue (e.g., for cogeneration or selling to utilities).

VII. CONCLUSIONS

A new method for human power conversion based onchildren’s play on playground equipment has been proposed.The power harnessed can be used as an auxiliary or back-upsource for electricity, especially in developing countries.Pneumatic components are used as power conversion devices

along with equipment such as seesaw, swing, etc. Alaboratory prototype based on a seesaw has been developed,and experimental results obtained illustrate the practicaleffectiveness of the proposed method.

ACKNOWLEDGMENT

The research reported in this study was conducted while theauthor was with the Engineering Science Program at theUniversity of Michigan-Flint. It was supported by a FacultyResearch Development Grant from the UM-Flint Office of Research. The author is thankful to Robert Victor for help inconstruction of the lab prototype, and to Dr. MeenakshiVijayaraghavan, Ethan Roelle and Casey Lang for help with

experiments.

REFERENCES

[1] The World Bank/The International Bank for Reconstruction andDevelopment, 2000, World Development Report 1999/2000,Washington, DC.

[2] Intermediate Technology Development Group (ITDG), 2000,Sustainable Energy for Poverty Reduction: An action plan , Rugby,UK.

[3] J.C. McCullagh (Ed.), 1977, Pedal Power in Work, Leisure, and

Transportation, Rodale Press, Emmaus, PA.[4] T. Baylis, 1999, Spring operated current generator for supplying

controlled electric current to a load , US Patent no. 5,917,310.[5] N.S. Shenck and J.A. Paradiso, 2001, “Energy scavenging with shoe-

mounted piezoelectrics”, IEEE Micro, 21, pp. 30-42.[6] R. Pelrine, R. Eckerle, P. Jeuck, S. Oh, Q. Pei, and S. Stanford, 2001,

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[8] T.O. Grichen, 2002, Toy rocket set , U.S. Patent Application no.20020020401.

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S.R.Pandian, 2000, “Development of an active orthosis for kneemotion by using pneumatic actuators”, International Conference on Machine Automation (ICMA 2000), Osaka, Japan, pp.615-620.

[11] H. Tsukagoshi, A. Miyashita, and A. Kitagawa, 1999, “A Fundamentalconsideration of a human power pedal air pump for disaster”, SICE Conference Proceedings, pp. 541-542, Morioka, Japan (in Japanese).

[12] A.J. Jansen and A.L.N. Stevels, 1999, “Human power, A sustainableoption for electronics”, Proc. IEEE Int. Symp. on Electronics and the Environment , Danvers, MA, 1999, pp. 215-218.

[13] K. Kuribayashi, 1993, “Criteria for the evaluation of new actuators asenergy converters”, Advanced Robotics, 7, pp. 289-307.

[14] S.J. Majumdar, 1996, Pneumatic Systems, McGraw Hill, New York, NY.

[15] Y. A. Cengel and M.A. Boles, 2002, Thermodynamics: An Engineering Approach, McGraw Hill, New York, NY.

[16] F. Takemura, S.R. Pandian, Y. Hayakawa, and S. Kawamura, 2000,“Modelling and sliding mode control of a vane-type pneumatic motor”,Trans. of Japan Society of Mechanical Engineers, 66-C, pp. 127-134(in Japanese).

[17] A.A. Kiryakin and Y.A. Moshchinskii, 1997, “Electromechanicalconverters of human muscle energy”, Applied Energy: Russian J. of Fuel, Power, and Heat Systems, 35(2), pp. 66-72.

[18] G. Negre, Method and device for additional thermal heating for motor vehicle equipped with pollution-free engine with additional compressed air injection, US Patent no. 6,305,171

[19] M. Seelhorst, 1998 (September), “Last Page: Think It’s New? Think Again”, Popular Mechanics, p. 138.

[20] A. Weisman, 1998, “Gaviotas: A Village to Reinvent the World ”,Chelsea Green Publishing, White River Junction, VT.

[21] A. Applewhite, 2003, “IT Takes A Village”, IEEE Spectrum, 40, pp.40 – 45.

[22] S.R. Pandian, 2004, “Playful Learning: Robotics and MechatronicsProjects for Innovative Engineering Education”, Proc. ASEE Gulf-Southwest Conference, Lubbock, TX.

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a human power conversion system based on children’s play PAPER