In this proposed vehicle, electrical and thermal energy sources are combined along with micro hybrid system. As energy sources ICE and Batteries are being used. These two power sources are hybridized. The battery is charged my means of national grid and solar energy. There are several hybridization methods available like Series, parallel, series-parallel and complex; parallel hybridization is implemented here. The basic difference between a hybrid and a conventional vehicle is the braking system. Hybrid vehicles use regenerative braking system; an energy recovery module which slows down the vehicle by transforming its kinetic energy into a form and is used immediately to other works or stored for further use. Hybrid vehicles are less fuel consuming [17L.R. Brandenburg, and E.T. King, No. 5291960. U.S. Patent. Hybrid electric vehicle regenerative braking energy recovery system, 1994.]. Fig. (1) shows the schematic diagram of the vehicle power train.

Fig. (1) Schematic diagram of the vehicle power train.

The fuel saving potential might be increased by recuperating brake energy and re-using this energy, E_EBR denotes the recuperating brake energy (for electric driving). This electric energy is used for driving (E_M). Fig. (1) shows the vehicle power drive.

This recuperating/regenerating brake energy is calculated over the drive cycle in t_f time;

(1)

In the above equation (1), f_br denotes brake friction (regenerative). The subscripts denotes namely the transmission, electric motor and battery efficiency which is respectively assumed 98%, 85% and 80% average constant. The engine assumed here is “shut off kind” and has no drag losses due to electric driving and braking.

In addition to the element sizing and control engine optimization, the topology selection also plays an important role in the general hybrid drive train optimization. In Fig. (1), an understanding is given of different locations of joining the hybrid system to the drive coach. If more hybrid driving modes can be used, then fuel saving potential rises. Depending on the topology, a number hybrid functions can be utilized very well other functions increase difficulties. In Table 2, an overview is given on the pros and cons of different topologies. Through this qualitative comparison, it can be concluded that topologies 1, 3, and 5 perform the same and are therefore favorable. The topological table here is based on quality and nature of the spare parts.

A Table showing the topological analysis is give below:

Table 2
Topological Analysis

Fig. (2) shows the topology designing of the proposed vehicle. The numbering indicates the possible locations of the components of the system. Here, ICE-Internal Combustion Engine, A-Alternator, FT-Fuel Tank of the vehicle, CL-Clutch (Wet-Plate type), BAT- Battery, Aux- Auxiliary Parts, MT- Manual Transmission.

Fig. (2) Topology designing of the proposed vehicle.

The specifications of the experimental engine are given below in Table 3:

Table 3
Experimental Engine Specifications [18M.L. Baglione, "Development of System Analysis Methodologies and Tools for Modeling and Optimizing Vehicle System Efficiency", PhD Thesis, University of Michigan: Michigan, .-20C.R. Ferguson, and A.T. Kirkpatrick, Internal combustion engines: Applied thermosciences, John Wiley & Sons: New York, pp. 325-402.].

The performance of an ICE depends on various measures like bore, fuel consumption, Brake Mean Effective Pressure (BMEP), Displacement of piston and etc. Table 4 below shows the performance testing results of the engine stated in Table 3.

Fig. (3) Simulated results using Simulink platform. (a) Fuel Consumption vs time profile, (b) Velocity profile with respect to time and (c) Power consumption profile.

Vehicle simulation model driven by engine was done regarding the above data. The simulations were done using Simulink platform. For engine properties Table 3 and for vehicle properties Table 4 was used. Fig. (3) shows the simulated results.

Table 4
Engine Performance Testing [21R.S. Khurmi, and J.K. Gupta, A Textbook Of Thermal Engineering (Mechanical Technology)., S. Chand, pp. 611-632.].

The battery used as electrical energy source will be charged in two ways, from National Grid and Solar PV module, respectively. A perfect designed PV module is needed to charge the batteries. The specifications of the PV module are given in the following Table 5 below.

Table 5
Photovoltaic Module Specifications [22M.A. Green, Solar cells: Operating principles, technology, and system applications., pp. 63-94., 23Grameen Shakti Solar Co, https://www.gshakti.org , .https://www.gshakti.org last accessed- 05/11/2017].

Let, The total weight of the proposed Vehicle =500 kg (including all mountings and passengers)

Average speed = 35 kmph

Total Power = Total weight of vehicle × g × speed × gradient of velocity

= 500 × 9.8 ×35 kmph × .03 Watts

= 500 × 9.8 × 9.7 kmps × .03 Watts

= 1426 Watts

Here, the induction motor used is of 12V-1kW rated.

42 Amp.

Load Current per Day = Current Flow × Running Time per Day × 1.2

= 42 × 5 hrs × 1.2 250 Amp.hrs/Day

Capacity of the Battery = Load Current per Day × 1.2 ≈ 300 Amp.hrs/Day (overall 25% losses)

Power required to run the motor = Capacity of Battery × Voltage Difference

= 250 × 36 = 9000 Whrs/Day

Now, here The Capacity of Solar Panel is 12V-180W,

Current Flow = (180/12)/4 = 3.75 Amp to each Battery

Charging Time = 250/3.75 = 66.67 hrs

If one Solar Panel is used then in 8 hrs of daylight the system will be charged or 12%. But if the numbers of solar panels are increased then this charging would be more efficient. This percentage of charging can be increased by increasing the number of solar panels. If two solar panels are used, then the system will be charged 24% using PV module.

In this section, installation cost of micro-hybrid system to a conventional engine operated vehicle is shown. Table 7 shows the cost assumptions for installing micro-hybrid system:

Table 7
Cost estimation of new component installation.

Here, as micro-hybrid system costs nearly the same of conventional gearing arrangement of ICE operated auto-rickshaw, so this cost can be omitted for the simplicity of cost estimation of new component installation.

In this system, it typically needs:

1-2 pcs of PV Panel(s) + 4 pcs of Battery + 1 pcs of Induction Motor = 46000-53000 BDT (554-638 USD approximately)

Thus, maximum installation cost of the proposed vehicle is 53000 BDT (Nearly 638 USD).

Payback period is the time required for the amount invested in an asset to be repaid by the net cash flow generated by the asset. It is a very simple way to evaluate the risk associated with a proposed project. An investment with a shorter payback period is considered to be better, since the investor’s initial outlay is at risk for a shorter period of time [28Payback Period (Accounting Tools), www.accountingtools.com/articles/2017/5/17/payback-method-payback-period-formula Last accessed- 04/10/2017, 29M.U. Khan, M. Saleem, and N. Khan, "Establishment process strategies and profit or loss calculation of transport & logistics company: a case of s-transporter of aligarh", Int. J. Manage. Res. Rev., vol. 7, no. 2, p. 134.].

Formula of payback period is,

Here,

n_y = The number of years after the initial investment at which the last negative value of cumulative cash flow occurs.

n = The value of cumulative cash flow at which the last negative value of cumulative cash flow occurs.

p = The value of cash flow at which the first positive value of cumulative cash flow occurs.

In this proposed vehicle,

Total power calculated to run the system = 1426 Watts

Power required to run the motor 9 kwatts.hr/day = 9 unit

In Bangladesh, commercial electric line cost 25 bdt/unit [Source: DESCO, https://www.desco.org.bd/ ]

Requires = 9000/ 5* 36* 4 = 12.5 hours to charge the full battery.

Cost to charge the battery= 12.5*25 = 312.5 bdt/day

Table 8 shows the payback period for the system.

Table 8
Estimation of payback period against new installing cost.

From the analysis above, Case-2 is more favorable.

Fig. (7) shows a graphical representation of Payback Period and Installation Cost.

Fig. (7) Payback Period vs Installation Cost graph.

So, the payback time of this proposed system is between 2-2.5 years (approximately). A typical auto-rickshaw running age is between 18-20 years without much fluctuation in its performance [30M.A. Rahim, M.U.H. Joardder, S.M. Houque, M.M. Rahman, and N.A. Sumon, "Socio-economic & environmental impacts of battery driven auto rickshaw at Rajshahi city in Bangladesh", In: International Conference on Mechanical, Industrial and Energy Engineering, KUET, Khulna, 2013.]. Fig. (8) shows the relation between the running age and performance of a typical auto-rickshaw of Bangladesh.

Fig. (8) Age vs Performance graph for sub-continental auto-rickshaws.

This proposed system needs 2-2.5 years to gain the installation cost, this payback time is only about 11-14% or less than 1/5^Th of the total running lifetime of an auto-rickshaw. So, this proposed system seems to be a profitable one by cost estimation.

Environmental impact analysis of a system is a mathematical prediction of that shows how much environment friendly that system is or how much harm can it cause. It is a very important factor regarding feasibility measurement of a system. This research is mainly focused on lessen the conventional energy consumption via using renewable energy in Bangladesh.

In Bangladesh, electricity is mainly produced by using thermal power plants. Those thermal power plants are a key source of CO₂ gas emission resulting in enhanced greenhouse effect [4I.R. Mujawar, and M. Avijit, "Case study on greenhouse process, gases, effect and control management", Int. J. Innovative Res. Adv. Stud., vol. 4, no. 5, pp. 430-440.]. A 500 MW thermal power plant can produce up to 1 kg/kWhr production of electricity [31A.B. Rao, and E.S. Rubin, "A technical, economic, and environmental assessment of amine-based CO₂ capture technology for power plant greenhouse gas control", Environ. Sci. Technol., vol. 36, no. 20, pp. 4467-4475.
[http://dx.doi.org/10.1021/es0158861] [PMID: 12387425] ].

Fig. (9) gives a complete knowledge about CO₂ emission from the power plants of Bangladesh.

Fig. (9) CO2 emission rates of various power plants in Bangladesh [31A.B. Rao, and E.S. Rubin, "A technical, economic, and environmental assessment of amine-based CO2 capture technology for power plant greenhouse gas control", Environ. Sci. Technol., vol. 36, no. 20, pp. 4467-4475. [http://dx.doi.org/10.1021/es0158861] [PMID: 12387425] -35P.S. Norman, Evaluation of the Barapukuria coal deposit NW Bangladesh.Case Histories and Methods in Mineral Resource evaluation.”, Geological Society., vol. 63, Special Publication, pp. 107-120. [http://dx.doi.org/10.1144/GSL.SP.1992.063.01.10] ].

All these properties are approximate and some are estimated.

Our proposed vehicle system offers about 24% less power consumption from National Grid. So, a huge number of these proposed vehicles will save more electrical energy resulting in less emission of CO₂ from the fuel fired power plants.

Here, Katakhali Power Plant (Rajshahi) of 50MW capacity will be kept under consideration for calculation.

Assuming the plant as a 24 hrs/day working system,

Maximum electricity supplied by the plant = 50000 kWhr

The daily CO₂ emission from Katakhali = 0.72399 tons

Now, if this proposed vehicle system is implemented on Rajshahi City then, let, the numbers of proposed auto-rickshaws = 2000 (estimated)

Energy savings per day per vehicle = 2.16 kWh [From previous feasibility calculation]

Total energy savings per day = (2000*2.16) kWh = 4320 kWh

CO₂ emission to produce 4320 kWh supply is = tons = 0.062553 tons (w.r.t. Katakhali Plant)

Lessen of CO₂ emission from Katakhali via using this system

From the above analysis, it can be surely said that the proposed vehicle system if implemented in Rajshahi City, then per day CO₂ emission can be reduced upto 8.64% and power can be saved upto 4320 kWhr per day. This analysis was performed considering no system loss; there remains a 25% system loss in thermal power plants. If the system loss is considered then actual percentage of CO₂ emission lessens from Katakhali Plant will be about 20-22%.

This feasibility analysis shows this system not only a cost effective but also an environment friendly one. This analysis mathematically proofs that vehicle system to be an effective one.

Below Fig. (10), shows the special properties of the proposed vehicle.

Fig. (10) Advantage of proposed vehicle.

Table 9 shows the differences among various types of auto-rickshaws with the proposed one’s.

Table 9
Differences among typical (ICE), electrical and hybrid auto rickshaw.