ELECTRIC BICYCLES - Engineering
ELECTRICBICYCLESA performance evaluationBY ANNETTE MUETZE & YING C. TANLECTRIC-MOTOR-POWERED BICY-First, this article provides a systematic, comprehensivecles have been making their way into theclassification of electric bicycles that includes an overviewU.S. market for about two decades. In theof the state of the art of today’s commercially availableUnited States, such bicycles can be fullyelectric bicycles (e.g., [1]–[12]). The overview includespowered by a motor. In other countries such as Japan,less commonly considered topics, such as regulatory issueselectric-motor-powered bicycles are required to operatein various countries, and different performance require-with 50% human pedal power for up to 12 mi/h, and anments of electric bicycles. Using knowledge from the fieldeven higher percentage of human power is required aboveof professional bicycling as a starting point, the findingsthat speed. Such bicycles are commonly known as “ped-are supported and theoretically expanded. Theelecs” (pedal electric cycle). In this article, the term “elec-power requirements in different typi-tric bicycle” is used to describe “electric-motor-poweredcal riding situations are alsobicycles,” including both fully and partially motor-pow-identified. The results areered bicycles. Electric bicycles can be used for a variety ofconfirmed by experi-purposes, for instance, as a vehicle for police or lawmentally obtainedIEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASEenforcement in cities where parking and traffic are aproblem, as a guide bicycle during bicycle races, as a parkranger vehicle, or for leisurely rides and commuting purposes. In the United States, electric bicycles are currentlyused most commonly for short trips to grocery stores orfor leisurely rides. EYEWIRE121077-2618/07/ 25.00 2007 IEEE
TABLE 1. ASPECTS FAVORING THE USE OFELECTRIC BICYCLES.PedalsGearsEnergy yChargerMotorOther CostsVehicleAccessoriesTraffic Flow1Parallel hybrid schematic diagram [9].data that have been collected in the context of real-lifeapplications. From the results, the key parameters,needs, and challenges involved in improving the performance of electric bicycles are identified. The article thengives a summary of the different results that can serve asa roadmap for such improvements. This summaryincludes both market trends and regulations and technical-science-related aspects. Different paths of furtherresearch to build on the presented work are outlined inthe conclusion.Basic Configuration of an Electric Bicycle SystemThe basic configuration of an electric bicycle drive consists of a controller that controls the power flow from thebattery to the electric motor. This power flow acts inparallel with the power delivered by the rider via thepedal of the bike (Figure 1).The rider of an E-bike can choose to rely on the motor completely pedal and use the motor at the same time pedal only (use as a conventional bicycle).Incorporation of exercise andlonger-distance commuting*Sample cost calculation for a 100-mi trip on a 2002 Mitsubishi Lancer: Gas tank capacity: 28 mi/gal [13] Approximate gas rate as of November 2004: US 2/gal Costs for 100 mi: US 2/gal/(28 mi/gal)·100 mi US 7.1Sample cost calculation for a 100-mi trip on an electric bicycle: Power to travel at 10 mi/h: 120 W (experimentally obtained, see Figure 4) Duration: 100 mi/10 mi/h 10 h Energy usage: 1.2 kWh Madison Gas & Electric rate as of November 2004: US 0.1/kWh Costs for 100 mi: 1.2 kWh · 0.1 /kWh US 0.12law to be pedelec-type bicycles. Electric bicycles producedin Taiwan are mostly exported to Europe.In regard to the United States, electric bicycles are notas popular as in the other countries mentioned and mostelectric bicycles are imported. In some states, the federallaw and the state law for electric bicycles differ.Aspects Favoring the Use of Electric BicyclesA number of aspects favor the use of electric bicycles indifferent situations. These include lower energy cost perdistance traveled (1–2% of going by car when going byelectric bicycle) for a single rider; savings in other costssuch as insurance, licenses, registration, parking,improvement of the traffic flow; environmental friendliness; and the health benefit for the rider (Table 1).Overview of Electric Bicycles WorldwideElectric bicycles have been gaining increasing attentionworldwide, especially in China, Europe, Japan, Taiwan,and the United States. In the following, the most distinguishing aspects of electric bicycles in these countries aresummarized, based on the authors’ own studies andFrank Jamerson’s Electric Bikes Worldwide 2002 [1].Today, China is the largest manufacturer of electricbicycles, exporting the majority of the electric bicycleswhile also meeting a strong local demand. According toChina’s Electric Bike General Technical QualificationGB17761-1999 [9], Chinese electric bicycles may notexceed 20 km/h and may not be heavier than 40 kg.In Europe, most electric bicycles are manufactured inGermany and the Netherlands, and pedelec-type electricbicycles are more common.In Japan, most electric bicycles are produced by theautomotive industry, and electric bicycles are required byPerformance Range of CommerciallyAvailable Electric BicyclesTable 2 gives a comparative overview of the performance ranges of today’s commercially available electricbicycles according to the authors’ market research. Itillustrates how widely the specifications of electricbicycles vary according to the bicycle design and theriding conditions for which the electric bicycle isdesigned. The influence of several factors and parameters on the different criteria and performance requirements are discussed in the “Investigation of TechnicalPerformance Requirements” section.Criteria for Classification of Electric BicyclesCriteria for classification of electric bicycles have beendetermined such that they are independent of thecountry and the purpose of use. These are the bicycleIEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASEvaluation of the State of the ArtEnvironmentalFriendlinessHealth BenefitAveraging, costs* are US 7.1/100 mi US 4.4/100 kmfor going by car, but only US 0.12/100 mi US 0.7/100 kmfor going by electric bicycle.Generally, no insurance, license,registration, and parking areneeded.Most states allow electric bicycleson bicycle paths; avoidance oftraffic jams.Zero-emission vehicle13
kit type, motor type, motor assembly, assist type,throttle type, motor placement, and battery type(Table 3). The assets and drawbacks of these criteriaare shown for each subcategory in Tables 4–10 (bicycleBatteryPackAnemometerPowerTap CPUMultimeterThumbThrottleTABLE 3. CRITERIA FOR CLASSIFICATIONOF ELECTRIC BICYCLES.ControllerBrushed Hub MotorPowerTap Hubkit, motor, motor assembly, assist, throttle, motorplacement, and battery types). In these tables, severalaspects should be pointed out: In general, bothbrushed and brushless dc motors are used by manufacturers of electric bicycles, but, as far at the authorsknow, synchronous motors and induction motors arenot being used. Even though technical aspects doexist, both the assist and the throttle types dependlargely on the rider’s personal preference. The designof the assist type can be significantly influenced bythe country’s regulation. Unless close attention ispaid, both full- and half-assist types can look the sameat first glance.Bicycle Kit Type Custom built Add onMotor Type*** Brushed dc machine Table 5 Brushless dc machineMotor Assembly Gear Hub FrictionTable 6Assist Type Full-assist Half-assistTable 7Throttle Type Thumb throttle Twist throttle Push buttonTable 82Electric bicycle test set-up used for the experimentalinvestigation.TABLE 2. PERFORMANCE RANGE OF COMMERCIALLYAVAILABLE ELECTRIC BICYCLES.IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASSpeed14Table 4Average speed12 mi/h19 km/h20 mi/h32 km/hMotor Placement Front wheel Rear wheelTable 9Maximum speed**Travel range(Full charge)10–50 mi16–80 kmBattery TypeTable 10BatteriesCharging time***At large, both brushed and brushless dc motors are used by most electricbicycle or electric bicycle kit manufacturers. To the authors’ knowledge,induction motors and synchronous motors are rarely used in commercially available electric bicycles and, thus, they are not discussed here.2–6 hCycles of charge/discharge Lead acid NiMH OthersUp to 400PowerPower consumption(Each full charge)On-board power supply100–500 WhTABLE 4. ASSETS AND DRAWBACKSOF DIFFERENT BICYCLE KIT TYPES.12–36 VTorqueHill climbing abilityCustom BuiltWeightElectric bicycle kitexcluding originalbicycle weightBicycle Kit Typeup to 6% slope10–50 lbs4.6–22.8 kgPrice rangeElectric bicycle kit onlyUS 250–US 800Electric bicycle kit andbicycle (Custom builtelectric bicycles)US 800–US 2600**Sec. 2085 of the federal law [14] defines a “low-speed electric bicycle” as “atwo- or three-wheeled vehicle with fully operable pedals and an electric motor ofless than 750 W, whose maximum speed on a paved level surface, when powered solely by such a motor while ridden by an operator who weighs 170 pounds,is less than 20 mi/h.”Add OnAssets:Assets: High-end bicycles Good appearance Safety features Little/no installationrequired Comparatively inexpensive Mounting flexibility Suitable for differentbicycle types Bicycle can be reconverted to a conventionalbicycleDrawbacks: Installation needed Connections may not berobustDrawback: Comparativelyhigh costs
Performance Evaluation of Electric BicyclesCriteria have been defined to evaluate the performance ofelectric bicycles. These are technical performance, practicability, design, environmental friendliness, and cost andeconomics (Table 11). The subcategories of all criteria,with the exception of the technical performance and costand economics, are commented upon individually inTables 12–14 (practicability, design, and environmentalcriteria). The technical performance characteristics such aspower, torque, and speed have been investigated both theoretically and experimentally and are discussed in the“Investigation of Technical Performance Requirements”section. Cost and economics are discussed in Table 1.TABLE 5. ASSETS AND DRAWBACKSOF DIFFERENT MOTOR TYPES.Even though the technical maturity of electric bicycleshas been, and is still, improving, still more work needs tobe done to make electric bicycles competitive with othervehicles. This includes more research on the durabilityand lifetime of such bicycles, the long charging time ofbatteries, and the sparse availability of charging stations.Investigation of TechnicalPerformance RequirementsTheoretical BackgroundThe total power Ptotal required to drive the bicycle isgiven by the sum of the power to overcome the air dragTABLE 7. ASSETS AND DRAWBACKSOF DIFFERENT ASSIST TYPES.Motor TypeBrushed dc MotorAssist TypeFull-AssistHalf-AssistAsset:Assets: Simple controller Higher efficiency andbrushed motor Reduced size whencompared withbrushed motorDrawback: More complex controllerthan brushed dc motorChoices of modesof operation: Pedaling only Motor operation only Pedaling and motoroperation in parallelChoices of modes ofoperation: Motor assistance is onlyavailable when theuser is pedaling Level of assistance isdetermined by the userinputAsset: Meets the lawrequirements in morecountries than thefull-assist typeDrawback: Rider always has topedalDrawbacks: Lower efficiencythan brushless motor Brushes increase themotor size and canincrease the difficultyof mounting the motorinto the fork of the bicycleAsset: Increased number ofchoices of modesof operationDrawback: Not legally allowed inall countriesTABLE 6. ASSETS AND DRAWBACKSOF DIFFERENT MOTOR ASSEMBLY TYPES.Motor Assembly TypeGearHubFrictionAssets:Assets: Provides desiredgear reductionratio Enables easiertorque sensing/adjustment/assists Motor Lightintegratedweightin the wheel Easy mounting MinimalmaintenanceDrawbacks: Chain/belt mayget entangledDrawbacks: Can beheavy Chain/beltmay needmaintenance:lubrication/tensionPower TapReceiverAsset:Drawbacks: Lessefficientdue tofriction loss Significant shift Tires wearof the centerout easilyof gravityPower Tap Hub3Power Tap hub [15] used for the experimental investigation.IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASBrushless dc Motor15
Pdrag , the power to overcome the slope Phill , and thepower to overcome the friction Pfriction . Equations (1)–(4)show the relationships as discussed in [6] and [8], wherethe symbols for the parameters, their units, and someremarks are summarized in Table 15.Ptotal Pdrag Phill Pfriction ,Cd · D · A· (v g v w )2 · v g ,Pdrag 2Phill 9.81 · G · v g · m,Pfriction 9.81 · m · R c · v g .(1)(2)(3)(4)The three cases that can be distinguished according toWilson’s Bicycle Science [8] correspond to the following riding conditions: Case 1At speeds greater than 3 m/s ( 6 mi/h), the majorityof the power is used to overcome the air drag Flat ground, high speed: Pdrag , Phill , 0, Pdrag Pfriction . Case 2At speeds less than 3 m/s ( 6 mi/h) and at level surfaces, the majority of the power is used to overcomethe rolling resistanceIEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASTABLE 8. ASSETS AND DRAWBACKSOF DIFFERENT THROTTLE TYPES.16 Flat ground, low speed: Pfriction , Phill , 0, Pfriction Pdrag . Case 3On steep hills, the power required for overcoming airdrag and rolling resistance is small when comparedwith the power required to overcome the slope Hilly ground, low speed: Phill , Phill , Pdrag , Phill Pfriction .Experimental Evaluation of the TechnicalPerformance of Electric BicyclesTwo types of measurements were designed to experimentally evaluate electric bicycle performance during reallife applications:1) The requirements in terms of power P versus groundspeed v g with respect to the influence of the load m,slope grade G, and head wind speed vw are experimentally determined.2) The riding profiles in terms of power P, torque T, andground speed v g are measured during riding intervalsof different riders, where the bicycle is used for a shortleisurely ride, grocery shopping, or commuting.Test Vehicle Description and InstrumentationFor the experimental investigation, an electric bicyclewith a brushed dc motor installed in the front hub, aTABLE 9. ASSETS AND DRAWBACKSOF DIFFERENT MOTOR PLACEMENT TYPES.Throttle TypeMotor Placement TypeThumb ThrottleTwist ThrottlePush ButtonFrontRearAsset:Asset:Asset:Assets:Assets: Reduced risk Feels likeof accidentalmoped/accelerationmotorcycle InexpensiveDrawback:Drawback: May be less Throttle cancomfortablebe turnedthan otheraccidentallytypes (personalpreference)Drawback: Need topush buttonrepetitivelyfor moreprecisecontrol Comparatively easyinstallation Good weightdistribution Suitable for lowlandand hilly regions withgood roads Best for lightweightvehicles in general,including bicycles Better traction for hillclimbing Suitable for mountainousregions and poorground conditionsDrawback: Comparatively complexinstallationDrawback: Front wheel slidesare more dangerousthan rear wheel slidesTABLE 10. ASSETS AND DRAWBACKS OF DIFFERENT BATTERY TYPES.Battery TypeLead-AcidNiMHOthersRegenerative BrakingAsset: InexpensiveAssets: Light Good performanceAssets and drawbacksdepend on typeAssets: Recovered energy increases thebicycle performanceDrawback: HeavyDrawback: CostDrawback: More complex controller thannonregenerative type
controller, thumb throttle, and battery pack are used(Figure 2). This bicycle is a commercially available bicycle that has been available in the laboratory. All experiments were carried out using this test vehicle. Theelectric hub motor in the front wheel is not used duringthe measurements, yet, using this bicycle, the actual setup of an electric bicycle is represented. For all measurements, the tire pressure was kept at 50–60 psi, which istypical for bicycles that are used for leisure and commuting and that are commonly not reinflated beforeeach ride. The torque and speed are directly measured inthe hub of the rear wheel of the test bicycle, using apower tap hub (Figure 3) [15]. The measurement information is transmitted to the Power Tap central processing unit (CPU) through the receiver. Furthermore, therelative head-wind speed as seen while riding is measured by means of an anemometer. The head-wind speedis then obtained from the difference of anemometer andpower tap speed.Experimental Investigation of Power Requirementas a Function of Load, Speed, and Head WindTABLE 11. CRITERIA FOR PERFORMANCE EVALUATIONOF ELECTRIC BICYCLES.Technical PowerPerformance Torque Speed Efficiency Distance/chargePracticability Technical maturity Battery charging Operating condition Service/maintenanceDesign Ergonomics Safety BatteryEnvironment Pollution NoiseCost and Unit priceEconomics Other costsTextTable 7Table 13Table 14Table 1TABLE 12. ASPECTS OF THE DIFFERENTPRACTICABILITY CRITERIA.Practicability CriteriaTechnical Maturity Technical performance is improving, yet morework is needed to be competitive with othervehicles. More research is needed on the durability/lifetime of electric bicycles.Battery Charging Long charging time; typically four hours compared with four minutes for a gasoline-fueledvehicle. Sparse availability of charging stations; recharging can often only be done at home.Operating ConditionAssets: no age limit generally no license required easy to operateDrawbacks: weather dependence not winter/wet weather/rain friendlyService/MaintenanceAsset: Conventional bicycle parts can beserviced by a conventional bicycle shop.Drawback: After-sales service and maintenanceare not well established today.TABLE 13. ASPECTS OF THE DIFFERENTDESIGN CRITERIA.Design CriteriaErgonomic Bicycle size is small. Parking is easy comparedwith other bicycles. Honks, headlights, and disk breaks can beadded for safety purposes.SafetyAsset: not as explosive as fuel vehicles (accidents)Drawback: More tests on general road safety andcrash tests on electric bicycles traveling at highspeed are required.Battery Significant component to increase the electricbicycle performance significantly. Lighter-weight, higher-energy-density batteriesare needed.IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASFor these experiments, four different riders rode the testbicycle without using the hub motor under different riding conditions. The experiments were conducted forspeeds up to 12 mi/h (19 km/h), which is typical for cityrides. The air density is approximated to be constant.Furthermore, based on the theoretical results, rolling anddrag coefficients are assumed to be almost constant andare not investigated in detail. For each measurementpoint, five to ten measurements were conducted and theaverage value was taken. Usually, the deviation of theindividual measurements for one point was in the orderof less than 20%. Three series of measurements were carried out:1) total power Ptotal versus ground speed v g as a functionof load m (Figure 4)2) total power Ptotal versus ground speed v g as a functionof slope grade G (Figure 5)3) total power Ptotal versus ground speed v g as a functionof wind speed vw (Figure 6).In the following, the measurement results are discussed.The series of measurements for total power Ptotal versusground speed v g as a function of load m (Figure 4) illustrates (3) and (4). For a given ground speed v g, small variations in load result in small variations in power17
Power (W)100TABLE 14. ASPECTS OF THE DIFFERENTENVIRONMENTAL CRITERIA.500Environmental Criteria56789Speed (mi/h)10114Influence of the weight of the rider and bicycle influenceon the power versus speed curve; no wind, constant slopePollution No gas emissionNoise 55–60 dB compared with fuel/gas vehicle levelsof 65–70 dBG er (W)250Power (W)IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IAS18ilar results have also been obtainedrequirement (20 W difference ofwith other riders than the one ofrequired power for 15-kg load variaFigure 5, but the results of Figure 5tion). For doubled load, twice theELECTRIChave been selected as they are thepower is required, as is illustrated byMOTORmost complete set of measurementscomparing the curves for (64 20) kgillustrating this analysis.) For aand (154 20) kg load. Generally, aPOWEREDgiven ground speed v g , Pfriction isheavier rider also has a larger effectivearea A which increases the power needconstant, but Phill is directly proporBICYCLES HAVEed to overcome the air drag (2) andtional to the slope grade G. Thus,accounts for the nonlinear increase fromneglecting the Pdrag , Ptotal increasesBEEN MAKINGthe curves obtained for (64 20) kglinearly with the slope grade G. Forand (154 20) kg load.approximately an 80-kg weight ofTHEIR WAY INTOAn addition of 10 kg to the bicyclerider and bicycle, 320 W (47 Nmsystems requires additional power oftorque) are required to climb up aTHE U.S. MARKETapproximately 10–15 W. Thus, there isreasonable slope of 4% at 10 mi/h.FOR ABOUT TWOnot a significantly larger amount of enerWith electric bicycles rated at thegy needed to propel the bike if the loadmaximum power allowed by federalDECADES.difference is less than a few kilograms.law of 750 W, the maximum torqueThe series of measurements, totalcapability at 10 mi/h is 110 Nm. As apower Ptotal versus ground speed v g asresult, the steepest slope electric bicycles can climb at 10 mi/h grounda function of the slope grade G (Figure 5), visualizes the correlation of (3). (Note that sim- speed is 8%. It is important to note that unless riding onhilly terrain, city rides usually need high torques only fora short period of time. Therefore, motors designed forcity rides can have rated power below the federal law154 20 kgprovisions.30075 20 kgThe measurement results for total power Ptotal versus64 20 kgground speed v g as a function of head wind vw (Figure 6)25061 20 kgare in line with (2). (Note that similar results have also200 (Rider Bicycle)been obtained with riders other than the one of Figure 6,but the results of Figure 6 have been selected as they are15020015010050056789Speed (mi/h)101 mi/h3 mi/h5 mi/h6 mi/h31145786Speed (mi/h)9101156Influence of the slope of the path on the power versus speedInfluence of the head wind on the power versus speedcurve; no wind, weight of rider and bicycle m 81 kg, allcurve; no wind, weight of rider and bicycle m 81 kg, allslopes taken as average.head wind speeds taken as average.
For the second group of measurements, four differentriders rode the test bicycle around the city of Madison,TABLE 15. SYMBOL AND PARAMETER DEFINITION.Symbol ParameterCdvgvwGmRc9.81RemarksThe drag coefficient issmall for aerodynamic bodies. Typical values are:Passenger car:Cd 0.3, recumbent bicyclist:Cd 0.77, uprightcyclist: Cd 1 [6],and Cd 0.5 for acyclist [3].Density of air kg/m3The frontal area is theFrontal area m2area of the massencountered by theair. Typical valuesare A 0.5 m2 [3]and A 0.4 m2 [6].Groundm/sspeedHead windm/sspeedSlope grade –The slope grade isrise/run. For steepgrades, G should beexpressed by arctan(rise/run).Weight****kgRolling–The rolling coefficientcoefficientdepends on frictioneffects. For example, compactedgravel and smoothasphalt paths havedifferent rollingcoefficient of 0.004[3] and 0.014 [6],respectively.Gravitym/s2acceleration**** Rider and bicycle, including accessoriesRider 1Rider weight[kg]Pave [W]Pmax [W]Tave [Nm]Tmax [Nm]vg,av [mi/h]vg,max [mi/h]vg,av [km/h]vg,max [km/h]Interval time[min]Energy [Wh]Rider 2Rider 29.42211.935.7Rider 49524.31179.0857.09.950.213.024.2 20.939.02577.6 Above the speed limit for low-speed electric bicycles according to U.S. federallaw (Table 2).9008007006005004003002001000051015Time (min)20257Power versus time profile of Rider 1 (same scales as Figure 8by intention).9008007006005004003002001000051015Time (min)20258Power versus time profile of Rider 4.IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IASDAUnitDrag–coefficientTABLE 16. RESULTS OF INTERVAL RIDING ANALYSIS.Power (W)Experimental Riding Interval AnalysisWisconsin, for 16–26 min. The average and maximumtotal power requirements Pave /Pmax , torques Tave / Tmax ,and ground speeds vave /vmax are summarized in Table 16.For illustration, Figures 7 and 8 show the power versusPower (W)the most complete set of measurements illustrating thisanalysis.) With increasing vw , the power requirementincreases. However, due to the very stochastic nature ofwind, this experiment only provides a rough idea of thetrend. Furthermore, crouching or an upright positionaffects the frontal area A. Yet, at relatively low groundspeed this significantly affects the power requirement,notably with flat ground. Future work to obtain accurateresults can be done by using wind tunnels.It is important to note that head wind does not seem tobe a major criterion for city-ride electric bicycles, giventhe usual profiles of city rides.19
IEEE INDUSTRY APPLICATIONS MAGAZINE JULY AUG 2007 WWW.IEEE.ORG/IAStime profiles of the two rides of Riders 1 and 4. Thesetwo rides represent the two extremes in terms of powerrequirements that are covered (same scales on both figuresby intention). It should be noted that the maximumspeed of the ride of Rider 4 exceeds the speed limit for lowspeed electric bicycles according to U.S. law of 20 mi/h(Table 2).The four riding profiles cover a broad spectrum ofPave , Pmax , Tave , Tmax , vave , and vmax . Neglecting the athletic figure of Rider 4, a maximum torque of 30 Nm,along with a maximum power of somewhat less than400 W, an average torque of 6–8 Nm, and an averagepower in the order of 100 W, reflects the requirementsof an average ride. It is noticeable that the ride of Rider1 is shorter than the ride of Rider 3 and about as long asthe ride of Rider 2, but consumes less than 50% of theenergy because of the lower weight of the rider. Evenwith assuming an efficiency of the drive of 50%, theenergy requirement of the rides of Riders 1–3 could bemet by a laptop-size battery. Such an energy sourcecould be easily put on and taken off the bicycle and thebicycle can be recharged in a similar way as is todaycommon with cell phones.20Summary of Performance RequirementsDrawing from the previous discussions, the electricbicycle performance evaluation is summarized in termsof different key parameters. These include market trendsand regulations, opportunities for improvement by special-purpose-design to attract customers, identificationof possibly oversized components and reduction of oversizing, and identification of areas where further researchis needed (Table 5). In a similar way as before, the subcategories of the different areas (market trends, regulations, special-purpose design, comments on oversizedcomponents and on research and development) are compared and commented upon individually in Tables17–22. Summarizing, more publicity is still needed toTABLE 17. SUMMARY: ELECTRIC BICYCLEPERFORMANCE EVALUATION.Market Trend DemandTable 18 PublicityRegulations On-road law Speedy bicycle Motor BatteryResearch and BatteryDevelopment Technical Regenerative brakingTABLE 18. COMMENTS ON MARKET TRENDS.Market TrendDemandThe market demand for electric bicycles mightincrease if nongreen vehicles are banned. Forexample, in Beijing, Tianjin, Guangzhou municipalsbanned the sale and operation of fuel-assistedvehicles.As a result, in the first half of 2000, sales of electricbicycles sales in Shanghai increased 99.14%,compared with the same period in the previousyears.PublicityMore publicity is needed to introduce the publicto electric bicycles.TABLE 19. COMMENTS ON REGULATIONS.Table 20 Distance bicycleReduction ofPossibleOversizingConclusionsThe issues associated with electric bicycles may beaddressed by custom-designed drives that are most efficient over a given operating cycle. These include citybicycles, hill bicycles, distance bicycles, and speedybicycles.The results of the studies listed here can serve as aplatform to improve electric bicycle performance ifnew drive systems are designed around key parametersthat will result in improvement of the system performance. Furthermore, they can be used for comparisonof existing drives in a systematical, comprehensive,and technical way.Table 19 Bicycle assemblySpecial-Purpose City bicycleBicycles Hill bicycleintroduce the public to electric bicycles. Also, moreattention needs to be paid to releasing electric bicyclesfrom licensing. A uniform standard/guideline fordesigners/manufacturers of electric bicycles would favoran increase in popularity and avoid the quality of electric bicycles being compromised. Custom-designedbicycles that are most efficient over a given operatingcycle, such as city, hill, and distance, and “speedy bicycles” would help to re-duce the additional cost andweight of oversized components. In this context, theelectric bicycle market would benefit from furtherresearch both on the battery and on the drive technologyand their use with electric bicycles.Table 21Table 22RegulationsOn-Road LawU.S. states have different laws for electric bicycles,particularly regarding the licensing aspect.Releasing electric bicycles from licensing wouldfavor an increase in popularity.Bicycle AssemblyA uniform standard/guideline for designers/manufacturers of electric bicycles would avoidthe quality of electric bicycles beingcompromised.
References[1] F.E. Jamerson, “Electric bikes worldwide 2002: With electric scooters &neighborhood EVs,” Electric Battery Bicycle Co, Naples, FL, 2002.[2] B. Kumar and H. Oman, “P
bicycles vary according to the bicycle design and the riding conditions for which the electric bicycle is designed. The influence of several factors and parame-ters on the different criteria and performance require-ments are discussed in the “Inve
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