Index

Abstract

The cost of Electric Vehicle Charging Station (EVCS) infrastructure is one of the problems which stand as a barrier in the way of widespread Electric Vehicles (EV). In this paper, the optimal design and operation of a renewable-powered EVCS will be introduced with minimizing cost and air pollution. By considering the station located in isolated area and will be supplied by hybrid Energy Sources. Configuration, sizing, economic optimization, operation and its effect on the environment are discussed. The proposed hybrid micro-grid consists of, photovoltaic panels, storage batteries, wind turbines, biogas generator and also a diesel generator. The case study of this work is to satisfy the 1056 KWh/day demand of EVCS for using at the selected site. Five different configurations of energy sources are studied to get the optimum case. HOMER software is used to implement the simulation model; the model is based on economic and environmental factors. Finally, the study introduces a cost-effective, socially and sustainable accepted design that can be useful in specifying the appropriateness of optimal design for other EVCSs.

Keywords: Electric vehicle, Electric vehicle charging station, Renewable energy net present cost, Cost of energy, HOMER software.

Received: 11 January 2021 / Revised: 5 February 2021 / Accepted: 22 February 2021/ Published: 3 March 2021 

Contribution/ Originality

This study is one of very few that investigated an optimal hybrid energy configuring the power system to operate the electric vehicle charging station in Egypt. This study documents that renewable energy sources are effective option to reduce the emissions from burning fossil fuels and also minimize cost of energy.


1. INTRODUCTION

The transportation sector is considered one of the major consumers of world oil between different sectors. In 1973, the transportation sector consumed 45% of world oil and this value in 2017 was reached 65.2% according to the International Energy Agency (IEA).  It represented more than 20% of Co2 (International Energy Agency, 2019).

In Egypt, there are 9.3 million street vehicles and presented 32 % of the emissions. 110bn EGP had been allocated to subsidize petroleum products in 2017, highlighting the substantial financial burden of fuel consumption (El-Dorghamy, 2018). So, the transportation sector in Egypt consumed 60.3% of its oil (International Energy Agency, 2019).

EV with Renewable Energy Sources (RES) is a promise solution for green transportation. As Egypt is endowed with a various abundant RES for example: the solar radiation intensity annual is 1970-3200 kWh/m2, wind speed varies between 5 and 8 m/s and can reach to 10 m/s in the Gulf of Suez area, so wind energy is suitable for electricity generation moreover the biomass as Egypt has large resources of it from agricultural waste which present 35 million tons annually (IRENA, 2018). Egypt making significant efforts to get benefit from its RES by encouraging investment in RES, through the existing Feed-In-Tariff (FIT) program. Egypt's government as the same as the governments in all world moves toward increasing the number of EVs and also EVCS to ensure the form of the sustainable transportation system in the next few years. If the uncoordinated EVs are supplied from the conventional generation, the emissions from the transportation sector will shift to the generation sector. For that, the EVCSs shall be integrated with RESs.

This paper checks the creating EVCS based on the existing infrastructure of fuel station (FS) on highways powered with RES. Using FS infrastructure will encourage EV drivers to take a long trip with more confidence and also help to avoid the initial cost of building new infrastructure for the public charging station. The motivation of this idea is to maximize the use of RES for charging the EVs with minimizing the energy demand from the grid, minimize the cost of energy (COE) and also minimize the emissions of CO2.

In this study, HOMER software was used to investigate five different cases to reach the optimum configuration according to economic and environmental views. As a significant contribution is made in this paper as follows:

This paper is arranged as follows: Part 1 shows the introduction, which includes the background of the study, problem statement, and objectives of this study. Section 2 describes the literature review, while Section 3 discusses the research methodology and defines the whole system parameters. Section 4 discusses the simulation results, whereas the last Section 5 depicts the conclusion, along with future guidelines.

2. LITERATURE REVIEW

Many studies were discussed the area of integration RES with EVCS. An economic evaluation for using vehicle-to-grid (V2G) services with PV by particle swarm optimization (PSO) algorithm is presented in Ghofrani, Arabali, and Ghayekhloo (2014). A comparison among different possible system architecture for a PV-EV charger is investigated in Chandra, Bauer, and Zeman (2015).

The design EVCS integrated with PV for workplaces is proposed in Chandra., Bauer, and Zeman (2016). The EV integrated with PV under uncontrolled charging with a smart charging application and V2G strategy is studied in Fattori, Anglani, and Muliere (2014). Charging Control strategy for EVs with PV and grid utility is proposed in Goli and Shireen (2014); Jin, Sheng, and Ghosh (2014). The EVs powered by wind energy and PV is presented in Capasso and Veneri (2015).

An experimental study of a DC charging station taking into account the integration of RESs with stationary energy storage systems and fleets of road EVs is proposed in Omar and Bhattacharya (2017). Optimal designs EVCS integrated with various energy sources rely on HOMER software to minimize life cycle cost is presented in Aldhanhani, Al-Durra, and El-Saadan (2017); Alghoul, Hammadi, Amin, and Asim (2018).
The use of the infrastructure of a petrol station with solar energy as an EVCS is evaluated in Domínguez-Navarro, Dufo-López, Yusta-Loyo, Artal-Sevil, and Bernal-Agustín (2019). Using a genetic algorithm (GA) to optimize the operation and installation of a fast-charging station with hybrid RES and storage systems is presented in Fathabadi (2020). Atallah, Farahat, Lotfy, and Senjyu (2020) Replaced storage battery bank by a s cell (FC) with a PV system and wind turbines to charge PHEVs. The feasibility of charging alternatives for PHEVs from PV and the grid is studied in ElNozahy and Salama (2014); Masrur et al. (2020).

3. METHODOLOGY

Some stages are taken into account as shown in Figure 2. to obtain the objectives of this paper. The pre-feasibility study of the proposed site was performed including the new estimated demand load on the existing power system of FS to charge EV, metrological input data as monthly average wind speed, global horizontal irradiation (GHI) and ambient temperature obtained from NASA Prediction of Worldwide Energy Resources (POWER) database as HOMER software used plus system constrains with economic parameter. Then, optimal design simulation considering technical and economic factors are performed and compared with the basic powered system.

4. LOAD, CLIMATE & ENERGY RESOURCES SPECIFICATION OF PROPOSED SITE

FS on the highway from New Cairo to Alamein selected as a case study and as a sample in this paper located at Wadi El-Natrun-El Alamein Rd, Alexandria Desert, Egypt to be EVCS as Figure 1. The station has an area of nearly 5000 m2 and supplied from diesel generator (DG) 50 KW to meet 295 KWh/day which presented the existing load as FS is isolated from grid.

For this research, the existing electrical load plus
Electric Vehicle Supply Equipment (EVSE) as a new added electric load required for charging EVs, were detailed in Table 1. For the charging units EVSEs, A 2.5% random variability is considered for both day-to-day and time step analysis to provide more reliability. The daily total energy demand of 1056 kWh/day, a daily average of 44 kW, and a peak load of 110 kW are found.

Figure-1. Satellite view of the proposed location of EVCS.

Figure-2. Stages of research.

Figure-3. Proposed Energy Sources.

Table-1. Detailed of existing & new electric load.

Status of Load Electric Load Rated in KW
Existing Four of Petrol pumps 1.5 KW/pump
Twenty of Flood lighting fixtures 150 W/fixture
Security Room 2 KW
Supermarket and Coffee (shop) 24 KW
New Two of EVSEs 50 KW/unit

For climate specification and energy resources for the selected site (30˚36.9`N latitude 29˚48.8`E longitude) as the annual average wind speed is 5 m/s at 50 m above the surface of the earth, the annual average GHI is 5.5 KWh/m2/day and the annual average temperature is 20.5˚c. The annual average for biomass can be provided per day is nearly 50 tons.

5. SYSTEM COMPONENT SPECIFICATION OF PROPOSED CONFIGURATIONS

The proposed configurations with different schemes are composed of a wind turbine, PV with batteries, DG, biogas generator and converter to meet the electrical load as Figure 3. For capacity, the HOMER software optimizer finds the optimal sizing of each component. The technical specifications of each component are shown in Table 2.

6. MATHEMATICAL MODEL OF PROPOSED CONFIGURATIONS

Economics plays a vital role to have an optimal combination of the RES components which based on net present cost (NPC) for EVCS. NPC is the present value of all the costs of installing and operating the component over the EVCS lifetime, minus the present value of all the revenues that it includes salvage value and grid sales revenue over the EVCS lifetime. Costs include capital costs, replacement costs, operation, maintenance costs, fuel costs and emission penalties. So, NPC is considered one of the most significant methods for the economic evaluation of the project over the entire operating life. The formula of the total NPC ($) is calculated as follows:

Equation 1

6.1. The Following Technical Constraints are Considered in Charging Station Design

7. RESULTS AND DISCUSSION

Various designs of EVCS supplied from different energy sources are presented in this section from the standpoint of economics, operation performance and emissions. HOMER software is used in simulation the EVCS for each hour every year. 289,240 solutions were simulated via HOMER with 281,172 were feasible and 8,068 were infeasible due to the capacity shortage constraint. The comparison criteria for the different configurations which are considered as mentioned earlier will be the COE produced, total net present cost, operation cost, initial cost as well as emissions. Table 3 is presented the detailed analysis of the optimal EVCS design of each case.

Table-2. Economic & technical specification of each component.

Description
Specification
Unit
Wind turbine
Type
AWS HC
----
Rated power
1.5
kW
Rated wind speed
10.5
m/s
Capital cost
15000
$/unit
Replacement cost
15000
$/unit
O&M cost
150
$/year
Life time
20
year
PV modules
PV model
Jinko Eagle
----
Rated power
300
W
Temp. coefficient
-0.39
%/℃
Operating temp.
45
℃
Capital cost
120
$/module
Replacement cost
120
$/module
O&M cost
1
$/year
Life time
25
year
Diesel Generator
Generator model
Generic
---
Rated power
Auto sized
---
Capital cost
500
$/kW
Replacement cost
500
$/kW
O&M cost
0.03
$/hour
Life time
15000
hours
Fuel curve slope
0.251
L/hr./kW
Fuel price
0.431
$/L
Storage battery
Type of battery
Trojan lead acid
---
Nominal voltage
12
V
Nominal capacity
2.02
kWh
Capital cost
300
$/unit
Replacement cost
300
$/unit
O&M cost
3
$/year
Lifetime
4
year
Converter
Converter model
Generic
--
Inverter efficiency
90
%
Rectifier efficiency
85
%
Capital cost
300
$/kW
Replacement cost
300
$/kW
O&M cost
1
$/year
Lifetime
10
year
Biogas Generator
Generator model
Generic biogas fixed capacity
---
Rated power
Auto sized
---
Capital cost
1000
$/kW
Replacement cost
800
$/kW
O&M cost
0.03
$/hour
Lifetime
20000
hours
Fuel curve slope
2
Kg/hr./kW
Biomass price
0.01
$/t

Table 4 presents the COE, NPC, REF and operation and maintenance cost for different configurations with the existing 50 KW DG. For case (a), the wind system is added to existing DG to meet the modified load with 85% renewable energy. Case (a) ranks the 1st of high net present cost as 52.8 M$ and also cost of energy as 7.88 $/kWh but ranks 2nd of low emissions. For case (b), the biogas generator supported the existing DG.  It ranks 2nd of high NPC (0.936 M$) and also COE (0.135 $). When connected the existing DG with PV panels as the case (c), it ranked 3rd of high NPC (0.798M$) and COE (0.118 $) and also ranks the 1st of high CO2 emission due to the least of all configurations in Renewable Energy Fraction (REF).

When wind energy is added to case (c), the results of case (d) nearly like case (c). The COE and NPC are decreased by nearly 30% when biogas generator is used with a battery system and added to case (d) to become hybrid renewable energy system with96.2% REF so, it ranked as 1st of low emissions and also from point of view cost analysis. So, case (e) is the optimal design for isolated hybrid micro-grid EVCS as shown from Table 4, Table 5. The total output power from the diesel system included existing and the new added is 18.9 MWh/year, from biogas generator is 210.8 MWh/year and from the PV system is 436.8 MWh/year as shown in Figure 4. The battery system in cases (e) is charged from the excess PV power generation, biogas and the diesel system to meet the electrical load, so this optimal case is operated under the Load Following (LF) strategy. Other cases are operated under CC strategy.

8. CONCLUSION

EVCS on highways plays a vital role to achieve the reliability for EV owners and help them to travel long distance with full confidence. This paper studied the optimal design for EVCSs depended on FS infrastructure by adding EVSE as a new electric load will be added to the existing load. The power supply system is needed to be modified to meet the new load with minimum COE and also minimum CO2 emissions. By facilitating different energy sources such as PV modules with a battery system, wind turbines, biomass and diesel system as a stand-alone and hybrid system. Case (e) Hybrid PV with a storage battery system, biogas and diesel generators for isolated EVCS achieved the economic and environmental factors successfully.

The following points are the major outcomes of the present study and can be applied for all EVCSs on the road of Wadi El-Natrun-El Alamein:

Table-3. Optimal design of isolated hybrid micro-grid EVCS with different configurations.

EQUIPMENT
(a)
(b)
(c)
(d)
(e)
Wind turbine (Numbers)
2703
0
0
2
0
PV modules (kW)
0
0
388
383
248
DG (kW)
50
50
50
50
60
Converter (kW)
0
0
144
144
136
Storage battery (Numbers)
0
0
0
0
44
Biogas Generator (KW)
0
90
0
0
50

Table-4. Emissions quantity (Ton/year) comparison of isolated hybrid micro-grid EVCS with different configurations.

 
(a)
(b)
(c)
(d)
(e)
Carbon dioxide
60.1
89.2
165.7
164
16
Carbon monoxide
0.375
0.558
1
1
0.1
Unburned hydrocarbons
0.016
0.024
0.046
0.045
0.004
Particulate matter
0.002
0.003
0.006
0.006
0
Sulfur dioxide
0.147
0.218
0.401
0.403
0.039
Nitrogen oxides
0.353
0.524
0.972
0.967
0.094

Table-5. Cost component comparison of isolated hybrid micro-grid EVCS with different configurations.

 
(a)
(b)
(c)
(d)
(e)
COE ($/kWh)
7.88
0.135
0.118
0.123
0.085
NPC (M$)
52.8
0.936
0.798
0.833
0.589
O&M (M$/yr.)
0.864
0.058
0.04
0.041
0.025
REF (%)
85
80
59.5
60
96.2

The excess electricity of case (e) Hybrid PV module with storage battery, biogas and diesel generators of isolated EVCS can be stored in the battery system as batteries bank depends on the LF control strategy that improved the reliability and stability of the system.

The Egyptian government can use this study to expand the use of renewable energy generation to compensate for the shortage in petroleum products. Moreover, practical implementation of this study will contribute in the increasing of EVs using in car market in Egypt. The concept of this paper can be used for any location in the World.

Figure-4. Electric Production.

Figure-5. Cumulative cash flow over project lifetime.

Funding: This study received no specific financial support.  

Competing Interests: The authors declare that they have no competing interests.

Acknowledgement: All authors contributed equally to the conception and design of the study.

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