Inte rnatio nal Jo urnal o f Sc ie ntific & Eng inee ring Re se arc h Vo lume 3, Issue 1, January -2012 1

ISSN 2229-5518

Designing Solar Three-Wheeler for Disable

People

Md. Shahidul Islam, Zaheed Bin Rahman, Nafis Ahmad

Abs tract—Mobility of the physically disabled or crippled people is a great concern of the society. It is really diff icult to realize t he problems and sorrow s of a physically disabled/crippled person w ho is partially or f ully dependent on others or conf ining himself in a w heel cha ir w ith limited mobility. This paper provides idea of currently available three-w heelers f or disabled people and proposes a new improved design of a solar pow ered three-w heeler suitable f or countries like Bangladesh w hich is an under developed country w ith huge disabled/crippled people from w ar, accidents and diseases. This three-w heeler is operated by solar pow er and suitable f or outdoor use. Solar pow er option enables the disabled people to use it at any place, even in remote areas w here there is no electricity. A general survey had been conducted on disabled people using w heel chairs and manual three-w heelers and the opinions of the experts w orking w ith the disabled people are also taken in to consideration to identif y the needs and requirement f or designing the solar three -w heeler. The proposed solar three- w heeler is meant to match and exceed the conventional three-w heeler’s f acilities w ith a more intelligent and ef f icient design. A solar panel to produce solar electricity, a battery system f or preserving electric pow er, an eff icient motor, cushion seat, all terrain tires are used f or this solar three-w heeler. Due consideration and attention is given to better maneuverability, eff ective use of solar energy, biomechanics and comf orts, increased suspensions, all terrain traff ic ability, ease of use etc. w hile designing this solar three-w heeler f or physically disabled people of the country.

Inde x Terms— Design, Solar three-w heeler, Disabled people

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1 INTRODUCTION

lot of difficulties and hassles involved w ith the mobility of the physically disabled people in the society. It has
been observed that physically disabled people ar e basically using some assistive devices like, crutches, ar tificial limbs or legs etc. and manual wheel chair s or thr ee-wheeler s for their day-to-day movements. But, these wheel chair s or thr ee- wheelers ar e crude or of inefficient in design; not very much suitable for outdoor use or common terr ain in the country like Bangladesh. Undoubtedly these manual wheel chairs or the thr ee-wheelers ar e the blessings for cr ippled people but in the question of humanity, it is j ust “to add insult to inj ury”. B e- cause, commonly found manual w heel chair or thr ee-wheeler has a basic pr oblem that the occupant must use physical for ce to turn the wheels. This action is physically str essful, can r esult in muscle and joint pain and degr adation, tor n r otor cuffs, r e- petitive str ess injury, and carpal tunnel syndr ome; which caus- es secondary inj ury or further disability[3].
Again, Use of conventional ener gy sources and rapid devel- opment of the pr esent wor ld have some bad impacts on the surr oundings and envir onment, like depleting limited ener gy r esour ce, damage of ecosystem, envir onment pollution, global

———— ——— ——— ——— ———

 Md. Shahidul Islam is currently pursuing masters degree program in IPE

in BUET, Bangladesh, PH: +8801918401469. E-mail: mdsi208@gmail.com

 Zaheed Bin Rahman is an undergraduate student of IPE, BUET, Bangla-

desh, PH: +8801717640350. E-mail: zotonrahman@yahoo.com

 Dr. Nafis Ahmad ,PhD,Tokyo Institute of Technology,Japan, Associate

Professor, BUET, Bangladesh, PH: +880171252980. Web:

http://www.ahmadn.info,E-mail: nafis@ipe.buet.ac.bd
warming and so on. As a r esult, Designing for Envir onment (DFE) is the crying need of the tim e and it is very much neces- sary to develop envir onment friendly equipment or transport for better living, for better wor ld.
Consider ing the overall pr evailing situation, development of a solar thr ee-wheeler for disabled people is a vital effort w her e solar ener gy and its advantages ar e taken into account. A solar thr ee-wheeler could be a stand-alone system; it will be self- operated and independent in natur e, using unending solar ener gy fr om the sun. It is pow er ed by solar ener gy fr om at- tached solar panel at top, exposed to sunlight. It can take us off the grid; can be used in a place wher e ther e is no electr icity.
The tr ansport idea concerned her e is a solar pow er oper ated thr ee-wheeler with light structur e of moderate height-width and w eight, which suits to Bangladeshi terrain. Also due em- phasis is given to biomechanics, comforts, safety etc. while designing the seat for the solar thr ee-wheeler. These featur es give gr eater stability, bett er maneuver ability, better mobility and comforts over the available man ual thr ee-wheeler s. In a sense, a solar thr ee-wheeler can be the complete solution for the transportation of physically disabled people of the country. Use of available r esour ces (for components such as pipes for chassis/body, wheels, bear ing etc. from the local mar ket) and simplicity in designing r esult cost economy. The battery used, motor and solar panels ar e also very much available in the mar kets. All these featur es make the solar thr ee-wheeler a very cost effective and envir onment fr iendly transpor t for the daily use of the disabled people.

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2 P RES ENT SCENARIO

Since the liberation war of Bangladesh in 1971, a lar ge number of people have become disabled and vulnerable to the c ountry. The pr evalence of disability is believed to be high for basic r easons r elating to over population, extr eme pover ty, illiteracy, social security, lack of awar eness of traffic rules and above all lack of medical/health car e and services. By latest, t he number s of disabled people ar e incr easing rapidly due to incr easing r ate of r oad accidents and other r elevant diseases [1]. In the pr esent social har dship, other family members often fail to pay pr oper attention and car e to the disabled people. So, their lifestyle impr ovement and independency is very much important and ur gent too.
Although disability is a maj or social and economic phenom e- non in Bangladesh, ther e is very little r eliable data available on this issue, especially in the absence of a compr ehensive nation- al survey on disabiled persons. Basing on some data collected by the pr evailing NGOs and international or ganizations, it is commonly believed that almost 10% of the total populations of Bangladesh ar e disabled and 2.5% of which ar e cr i ppled or physically disabled [2]. Pr esently available w heel chairs ar e basically for indoor use or short distance movement and the manual thr ee-wheelers for outdoor use. But those ar e not very suitable for use and having lot of technical dr awbacks.
The number s of cr ippled/ disabled people ar e quite alar ming but the numbers of wheel chair or thr ee-wheeler users ar e not big and mostly found them in hospitals and r esidents, esp e- cially in urban ar eas. It is r evealed fr om the survey that the number s of pr esent wheel chair /thr ee-wheeler users ar e neg- ligible in all over the country. It happens because the pr esently available wheel chair s or thr ee-wheelers ar e manual and not very suitable for outdoor s use or for the r oads ar ound the country. The r oads even in the cities ar e not very smooth or ther e is no lane for wheel chairs/ thr ee-wheelers. Most of the cases the r oads ar e very rough and narr ows w ith some other limitations. Commonly Bangladesh has plain land and r oads in the villages ar e of rough condition wher e peoples ar e mov- ing w ith their bicycles, r ickshaws etc. City r oads ar e better wher e people move by r ickshaws, auto- r ickshaws, busses, taxi-cabs, cars etc.
Ther e ar e some NGOs like, Centr e for Disability Development (CDD), Centr e for Rehabilitation of the Paralyzed (CRP) etc. wor king for the physically disabled people and pr oducing some manual wheel chairs and thr ee-wheelers, somehow suit- able for outdoor use. But again the pr oblems r emain, as the users need to use the physical for ce to dr ive it. Photogr aphs of the pr esently available w heelchairs and thr ee-wheeler s in Ban- gladesh ar e shown in Figur e 1.

(a) Wheelchair (b) Thr ee-wheeler (c) Thr ee-wheeler Figur e 1. Differ ent types of available wheelchair and thr ee- wheelers
The common size and basic dimensions of the pr esently avail- able wheel chair s and thr ee-wheelers ar e shown in Table 1.
Table 1: Basic dimensions of the pr esently available wheel chairs and thr ee-wheelers

The main problems with the presently available three- wheelers are that these are manual, needs physical force to drive it; causes secondary injury such as upper extremity rep e- titive strain injuries, vibration exposure injuries, pressure ulc- ers, accidental injuries etc. There are lots of technical draw- backs of this manual three-wheeler too. However, the main drawbacks can be pointed as; crude or of inefficient design, biomechanics are not well considered, lack of safety measures, over weight and size, not suitable for outdoor use and no shed for protection to the user against adverse environment like sunshine, rain etc.

3 PROSP ECT O F S OLAR THREE-WHEELER

Scarcity of ener gy is a common pr oblem in all over the globe due to lack of conventional ener gy sour ces. So, Eco-fr iendly r enewable ener gy like solar power can be the altern ative and solve the pow er pr oblem to some ext ent. Availability of solar ener gy r adiation is the most vital consider ation for designing and development of a solar system or solar equi pment at any location on the earth. Rated solar radiation power r eceived by the earth sur face is (global r adiation flux) 1000 W /m² (AM 1.5, sun at about 48  fr om overhead position). Availability of solar ener gy radiation in all over the country is very much encour- aging for developing a solar thr ee-wheeler for disabled people in Bangladesh. The geo-location of Bangladesh is in favor of r eceiving highest amount of solar r adiation r ound the year. It is situated betw een 20.30-26.38 degr ees nor th latitude and

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88.04 - 92.44 degr ees east, w hich is an ideal location for solar ener gy utilization. Solar radiation mapping shows that the daily aver age solar radiation varies between 4-6.5 kWh/m² . Maximum amount of radiation is available on the month of Mar ch-Apr il and minimum on December-January [5].
The r esear ches have been going on to pr oduce solar car , solar plane and so on. In the tr ansportation sector , the use of solar ener gy faces differ ent pr oblems, such as the limited space for panel, batteries, transmission pr oblems etc. Many in the wor ld attempted to carry out the idea of a solar car , j ointly for ming as association and establishing a yearly r ace for solar pow er ed cars, in differ ent county each year. These w or ks show the de- sign par ameter s for a solar car only and no significant achievement yet for a suitable solar thr ee-wheeler for disabled people.
Since the solar pow er system suits w ell w ith the minimal pow- er consumption, the development of the solar thr ee-wheeler would be very much feasible as it as mini transport needs comparatively smaller power for the power system. A 100 W solar panel is good enough to support the daily p ower r e- quir ement. How ever , the most challenging par t of the solar thr ee-wheeler pr oj ect is to use the limited solar ener gy effec- tively, maximize its efficiency and ensur e suitability/traffic ability on our terrain. Successful implementation of the pr oj ect will depend on how successfully and exactly the pr oblems are indentified.

4 D ESIGNING THE SOLAR THREE- WHEELER

Designing of the solar thr ee-wheeler has two major parts/aspects. Fir stly, Designing the thr ee-wheeler and it’s components fr om mechanical and biomechanics point of view and secondly, incor poration of solar pow er system to the im- pr oved manual thr ee-wheeler to achieve automation. Draw- backs of the available manual thr ee-wheelers as well as needs and r equir ements fr om the disabled people (users) ar e s erious- ly consider ed while making definite impr ovement in design- ing. Effective use of limited solar ener gy (due to limited space/module), ener gy stor age and pow er r equir ement (load) ar e also ser iously consider ed to balance and optimize the solar pow er system of the solar thr ee-wheeler.

4.1 D ESIGN PHAS ES

The overall designing of the solar thr ee-wheeler is done through differ ent phases as: r ecognition of the needs, defini- tion of pr oblem, synthesis, analysis and optimization, evalua- tion and pr esentation Fir stly, the demand or r equir ements fr om the disabled people ar e identified. Then the human r e- quir ements ar e tr anslated to technical r equir ements, which
include all the specifications or character istics for the solar thr ee-wheeler to be designed. Then the solar thr ee-wheeler under design has been analyzed to whether it complies with specifications. Once complied, then it was optimized and leaded to a successful design. Sometimes, the analysis may r eveal that the system is not an optimum one. In evaluation phase, testing of the solar thr ee-wheeler is done and finally it is pr esented to others.

4.2 US ER’S N EEDS AND R EQUIREM ENTS

A general survey had been conducted among disabled people who ar e using wheel chair s and manual thr ee-wheelers. They had been interviewed on some specific questions and their pr oblems/needs had been investigated and identified. They came out with their pr oblems, r equir ements, opinions as well. Basically these ar e the r equir ements fr om the physically dis- abled persons using manual w heel cha ir /thr ee-wheelers. The opinions and advices of the experts wor king w ith the disabled people ar e also taken in to consideration. Their overall needs and r equir ements can be descr ibed as: the thr ee-wheeler should be power dr iven to avoid physical force, it c an be used at any time either in day or night, having lighter weight with better safety and stability, easy to contr ol and better maneuv e- rability in case of narr ow space/r oads, comfortable, all terr ain traffic ability/mobility and suitable for indoor as w ell as out- door use, having available solar power to drive the thr ee- wheeler in average15~20 km distance per day, able to pr otect the user fr om the adver se environment like sunshine, r ain etc., having availability of spar es, ease of maintenance and finally cheaper pr ice.

4.3 D ESIGN CONSIDERATIONS

Design considerations r efer to some character istics, which in- fluence the design of the element or , perhaps the entir e system. The str ength of each element, its dimension and geometry ar e impor tant design consider ation fr om the mechanical point of view . As a transpor t for the physically disabled people the overall safety, stability, r eliability, contr ol, comforts etc ar e a very much impor tant and taken in to consideration w hile d e- signing it. How ever , the general points of consideration during the designing of the solar thr ee-wheeler ar e: simplicity, str ength, stability, safety, corr osion and w ear , w eight, size, flexibility, ease of contr ol, modular ity, efficient extraction of solar ener gy, effective use of solar ener gy and ener gy storage, all terr ain tir es for all terrain traffic ability/mobility, incr eased suspensions, biomechanics and comfor ts and cost.

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4.4 DIFFERENT PARTS/COMP ONENTS O F THE SOLAR

THREE- WHEELER

The main components of the solar thr ee-wheeler ar e: Chas- sis/Frame, W heels, Body, Seat, Solar panel mounting frame, Solar Panel, Char ge contr oller, Battery, Motor , Chain, Steering System, Speed Controller , Br eak System, lights etc.

4.5 MECHANICAL D ES IGN

The Chassis/Frame of the pr esently available thr ee-wheeler is heavy and w heels ar e of big sizes. So w hile designing, unn e- cessary weight is r educed to meet the r equir ement. Compara- tively smaller wheels ar e selected; keeping in mind that the weight of the solar thr ee-wheeler should be as low as possible and must have r equir ed str ength. The solar thr ee-wheeler chassis is designed by using steel pipes r einfor ced with angle bar s wher e necessary. The chassis can withstand necessary loads as w ell as absorbs shocks. The overall length and width ar e also r educed to some extent. Finally, the chassis is made by steel pipes having 19 mm diameter w ith 2 mm thickness. Rein- for cement in bends etc. is done by 19 mm×19 mm angle bar s as necessary. To avoid accidents and ensur e safety, the shar p edges, bends etc. ar e rounded. Total w eight of the loaded solar thr ee-wheeler (w ith a person) will be 150 kg. Four ir on pipes (Steel ASTM-A36) ar e to bear the load as frame/chassis and the maximum static deflection of the used pipes w ill ar ound 0.66 mm, which is acceptable. Due to shock, these pipes will also deflect mor e and act as a shock absorber.
Figur e 4: Design of the proposed solar thr ee-wheeler
Overall r oad condition including bumps, pot-holes etc. ar ound the country is duly consider ed while choosing the wheel as well as it’s size. All the thr ee wheels ar e of equal size having the diameter of 40 cm each. All terrain tir es ar e used for better traffic ability. The body of the solar thr ee-wheeler is made of pipes, steel sheets of minimum possible thickness and w oods for lighter w eight. Tw o leaf spr ings ar e added to the r ear axle for better suspension. An adjustable waterpr oof cus hioned seat is attached with the chassis. The solar panel is set on the top (over head) with panel mounting fr ame made of light steel pipes duly attached to the main fr ame/chassis. While model- ing; shar p edges, bends, nails ar e avoided to avoid acc idents
and ensur e better safety. The basic size and dimensions of the solar thr ee-wheeler ar e set to: Length: 132 cm, Width: 86 cm, Height: 137 cm with the gr ound clear ance of 20 cm as shown in Figur e 4.
A nor mal handle bar decorated w ith br ake lever , accelerator , sw itches etc. and attached with fr ont wheel is used her e as steering. The speed of the solar thr ee-wheeler is contr olled by acceler ator thr ough cont inuous change in voltage by a twist throttle. Due to voltage change the motor pow er also changes and ther eby speed is contr olled by incr easing or decr easing the voltage. Normal fr iction type br aking system (as used in bi- cycle) is used in fr ont as w ell as in r ear-left wheel of this solar thr ee-wheeler for better safety. The hand liver attached with handle/steer ing is used to actuate the br ake. One hea dlight, indicator lights and backlights ar e attached to the solar thr ee- wheeler , which get pow er fr om the battery. High-gr ade wir es ar e used to make necessary cir cuits/wir ings for electrical sys- tem of the solar thr ee-wheeler.

4.6 D ESIRED SP EED AND POWER R EQUIREM ENT

In consider ing the physical condition of a disabled person, over all terrain condition, safety etc., the speed of the solar thr ee-wheeler is set to 6 km/hr or 100 m/min. This speed will ensur e better stability as w ell as comfort for the user. Pract ical- ly it is experienced and measur ed that the total force (F ) r e- quir ed for moving the loaded solar thr ee-wheeler on smooth r oad is almost 6kg. Her e r ear wheel diameter is 0.4 m; speed of the thr ee-wheeler is 6 km/hr or 100 m/min. So, wheel rpm and tor que will be 80 r ev./min and 12 N-m r espectively. Finally r equir ed pow er is 134W. If pow er loss due to chain dr ive is
10% then desir ed pow er r equir ement for dr iving the solar
thr ee-wheeler will be ar ound 149 W.

4.7 MOTOR

The pr ime mover to be used in this solar thr ee-wheeler is a permanent magnet D.C. motor. The main r eason for using this motor is that it is highly efficient and the flux density does not decr ease with time. It’s per formance char act eristics suite very well to the r equir ement of our solar thr ee-wheeler. At standar d load condition, the motor needs 149Watts. This pow er will cover the r equir ed power n eeded to r un the solar thr ee- wheeler at a speed of 6 km/hr. If the load incr eases or the thr ee-wheeler climbs up-war d slope, then the curr ent will also incr ease and pow er output of the motor w ill also incr ease. How ever , consider ing standard pow er r equir ement and the safety, the designed motor power capacity is set to 200 W.

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4.8 THE SOLAR POW ER S YSTEM

The solar pow er system of the solar thr ee-wheeler consists of solar panel (100W ), MPPT solar char ge controller , Lead-acid battery (12V-80Ahr.) etc. The typical solar pow er system is shown in Figur e 5.
12.2 amps, which is a very r easonable r ate of withdrawal fr om a lead-acid battery of intermediate range for meeting nor mal playing load. The solar thr ee-wheeler r equir es 149 W for r un- ning a distance of 6 km. Ther efor e, w ith a single lead-acid bat- tery (12 V, 80 A-hr.), it can cover a distance of 39 km in full char ge. It is experienced fr om the survey r epor t that a disabled person normally travels maximum 15~20 km per day. So a 12 volt 80 A-hr lead-acid battery once fully char ged can r un for 2 days easily.

4.8.3 SOLAR C HARGE CONTROLLER (MPPT TYP E)

Solar Panel

DC Mo tor

Charge Controller Battery

Pow er Tr ans- mission to
A MPPT solar char ge contr oller is chosen for the solar pow er system of the solar thr ee-wheeler to extr act maximum pow er fr om solar panel thr oughout the day. This is operated by mi- cr opr ocessor s for sensing and r ecor ding the panel voltage and curr ent at fr equent intervals for computing and adj usting the pow er output. This solar char ge contr oller takes the uncertain voltage fr om the solar panel and conditions it to char ge the lead-acid battery safely. It cuts out the batter ies fr om the load when the lead acid batter ies ar e depleted to pr event damage to the battery and also pr otect the panels fr om the batteries after the sun goes down. Her e, it collects char ges fr om solar panels and char ges the 12 volt lead-acid battery. It has LED bar r ea-
dout to show the status of the solar char ging system and batt e-
W heel thr ough
Chain Dr ive
Figur e 5: Diagr am of solar pow er system

Wheel

r ies. W ith the help of this MPPT solar char ge contr oller about
20 to 30% mor e ener gy can be generated than that of a com-
mon type char ge contr oller.

4.8.1 BATTERY

A solar thr ee-wheeler is the stand-alone system. To make prac- tical use of the solar ener gy gener ated fr om solar panels, batt e- r ies ar e used to stor e the ener gy to meet up motor pow er r e- quir ement as needed at any time either in day or night. A 12- volt , 80 A-hr lead-acid battery is pr eferr ed and used her e in solar thr ee-wheeler power system as used in most of the PV systems. Main r eason of using such lead acid battery is, it’s availability and comparatively cheaper cost .

4.8.2 ENERGY/POW ER AVAILABLE FROM A LEAD-ACID

BATTERY

An aver age 12 volts 80 A-hr capacity Lead-acid battery (car battery) should supply about 960Wh, pr ovided that the ener gy withdrawal is at low level curr ent. For the speed of 6 km/hr , the solar thr ee-wheeler r equir es 149 watts in full load condi- tion. Thus a 12 volt battery has to supply amps appr oximately

4.8.4 SOLAR PANELS (M ODULES)

Solar PV panels ar e designed to gener ate/collect desir ed ener- gy r equir ed by the solar thr ee-wheeler. Pow er needed to run the solar thr ee-wheeler is indir ectly supplied fr om solar panel. Basically this solar panel when exposed to the sunlight pro- duces DC cur r ent (solar electr icity) which is stor ed in a battery and used by motor as per the r equir ement, as and when r e- quir ed basis. Now, it is important to design the solar panel size and it’s power output in w or king condition. The solar panel consists of solar cells. The amount of pow er output of a solar cell depends on solar cell efficiency and solar cell ar ea. Usually
30~36 solar cells connected in series ar e laminated together to make a so-called solar PV module. Commer cially available single solar cell normally having the dimensions of (3"× 6"), (10 cm ×10 cm) etc. A (10 cm ×10 cm) solar cell's electr icity output is likely r ated at 0.50 to 0.55 volts with 3 to 3.3 amps. Her e, in the module, 36 cells ar e connected (in series) together so that in all oper ating conditions a PV module gives w ell above 12 volts, w hich is the r equir ed to char ge a 12 V battery. As w e

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know, Watts equals to Volts multiplied by amps and a (10 cm
×10 cm) solar cell’s output is 0.5 volts and 3 amps in general.
So, a single module (consists of 36 cells) w ill have 18 volt r ated output and 54W rated pow er. If oper ating factor cons ider ed as
0.9, then the actual (practical) output voltage and power will be 16.2 V and 48.6W. How ever , this 16.2V output in pr actical
field matches and good enough to meet up the r equir ements of char ging 12V lead-acid batteries. Thus two 50W solar panels in parallel connection w ill give us 100 watts w ith 16.2 volts and 6 amps.
Now, The size of the single panel = (36×0.1×0.1) sq-m. = 0.36 sq- m in general. So, total ar ea needed for 2 panels = (0.36 ×2) sq-m
= 0.72 sq-m, which fits w ell in the space available at the r oof of the solar thr ee-wheeler.

4.8.5 BATTERY C HARGING VOLTAGES AND CURRENTS

To char ge a battery, the char ging voltage must be higher than the battery voltage or at least equal. As per the motor pow er r equir ement, a 12 V- 80 A-hr. lead acid battery is very much feasible for the solar thr ee-wheeler. “Tr ickle char ging” (char g- ing in low amps, 2 to 10 amps) is always better for any battery char ging; it incr eases battery life and decr eases electr icity pil- fer age. Her e, the char ge contr oller will char ge the battery at ar ound 16.2 volts and 6 amps. A full day of sunlight (6 hours) will char ge it fully if it’s not fully dischar ged when hooked up.

4.8.6 IMPOTANT FEATURES AND MAJOR

SPECIFICATIONS

The main featur es of the solar thr ee-wheeler ar e: a) Aut omatic (solar pow er ed) and envir onment fr iendly. b) A Standalone system- can be used at r emote places w her e ther e is no electr ic- ity. c) Biomechanics- comfortable and suitable for the health of the disabled. d) Having better safety, stability, maneuverability and modular ity in design. e) Suitable for Bangladeshi-terr ain and having pr otection fr om sunshine, rain etc. and f) Econom- ic as no power cost and easy maintenance. The maj or specifica- tions ar e summar ized in Table 2.

5 CONCLUSION

Development of the solar thr ee-wheeler is a blessing for the disabled people and w ill have significant change in their mo- bility as w ell as life style. The over all designing of the solar thr ee-wheeler is done with a view to pr ovide maximum possi- b le facilities to it’s user - the disabled people. Automation by solar power , biomechanics, comforts and safety get maximum
Table 2. Maj or specifications of the pr oposed solar thr ee- wheeler

prior ity in designing. Other attractions of this solar thr ee- wheeler ar e flexible and modular designing. Because of flex- ibility and modularity in design, desir ed modification (change of wheels, seat, height of the chassis etc.) if needed, can easily be done to meet up any individual r equir ement. Though it is solar oper ated but it can also be char ged w ith grid electr icity if desir ed. Long distance (over 35 km/day) travelling is not poss- ible by this solar thr ee-wheeler due to limited ener gy stor age and it may not per form w ell dur ing consecutive cloudy/r ainy days. Again, the volume/size of the solar panel cannot be in- cr eased for incr eased ener gy demand due to limited space over head (r oof). How ever , mor e efficient solar panel or solar pow er tr acker can be used to extract mor e (maximum possible) ener gy fr om the sun to meet up incr eased ener gy demand. Nickel-cadmium batter ies though expensive ar e ideally mor e suited to PV system than the lead-acid battery and can be used for better per formance; it also has less of w eight and no dam- age if the battery r emains fully dischar ged for long per iods. As a “stand alone system”- all the disabled people at any cor ner of the country can enj oy the benefits or advantages of this solar thr ee-wheeler for their daily use. Though the solar thr ee- wheeler has been designed and developed in consideration of the disabled people of Bangladesh but disabled people at di f- fer ent corner s of the w orld can use it provided that ther e is sufficient amount of solar radiation. Finally it is important to mention that the solar thr ee-wheeler is not only envir onment fr iendly transport for disabled people but also pr event the sec- ondary disability as auto power transport. So, it is a complete solution for mobility of the disabled people of the society.

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