2nd Int'l Conf. on Electrical Engineering and Information & Communication Technology (ICEEICT) 2015 Jahangirnagar University, Dhaka-1342, Bangladesh, 21-23 May 2015
Optimization of Grid-Tied Distributed Microgrid System with EV Charging Facility for the stadiums of Bangladesh Sourav Barua, Chowdhury Akram Hossain, and Md. Mahfuzur Rahman
Department of Electrical and Electronic Engineering American International University-Bangladesh Dhaka, Bangladesh Email:
[email protected]
Abstract- Photovoltaic system and wind power are the bright future of hybrid distributed renewable power generation for dreaming
a
decontaminated
green
world.
Modern
world's
enhanced commercial activities and rapid industrialization are increasing the peak of electricity demand in a significant way. Integration
of
battery
operated
vehicles
and
upgraded
automation technologies to conventional power systems are also consuming large amount of power from grids. On the verge of producing clean energy, the civilized world has all the reasons to generate power from hybrid power systems. Coping with the technological advancement and obsolescence, Bangladesh is also progressing to extract power from existing renewable energy resources and their integration to the national grid. To assist country's
distributed
generation
plan,
installation
of
photovoltaic-wind power based hybrid systems with charging facility for Electric vehicles in major stadiums in Bangladesh is proposed in this paper. Cost analysis is executed in HOMER. Proposals
validity
and
usefulness
both
are
also
explicitly
discussed.
Keywords- Distributed power generation system, Microgrid, Solar Power, Wind Power, Stadium
I.
INTRODUCTION
At present, power crisis in Bangladesh is at its peak. Due to less production of conventional power plants with de-rated machineries, consumers as well as industries are not provided with needed power. Moreover, peoples of remote areas like villages and coastal areas are still deprived of electricity. Load shedding is occurring more and more often. There is always remaining a gap of 1000-1500MW between generated power and demanded power [1]. If this situation continues, then in future government will have to supply power from distributed renewable power generation resources to household consumers. So, now it is a good time to produce electricity from hybrid distributed systems and integrate most of the systems to the national grid. Photovoltaic system and wind turbine installation on outdoor stadiums are not a new concept. World's many developed countries achieved success by adopting this planning. Recently, the world's largest solar energy powered sport stadium has been completed in Kaohsiung, Taiwan and 2 put in use promptly. Covering a surface area of 14,155m , 8,844 solar panels are used to make this epitome of engineering ingenuity [2]. Its solar energy system meets 1MW-p (megawatt peak) capacity and can generate l.lMkWh of
978-1-4673-6676-2/15/$31.00 ©2015 IEEE
electricity annually. Environmentally, the 1.14MkWh of electricity generated by solar PV reduces approximately 660 tons of CO2 emissions per year. On the other hand, the hosting country of FIFA world cup 2014, Brazil also installed solar panels in one of its big and attractive stadiums named 2 Maracana Stadium. With a mounting area of 2380m , 1554 solar modules have been installed to produce 390kW-p which can supply power to 240 ordinary homes on average and can save approximately 2,560 metric tons of CO2 [3]. Many popular stadiums of North America are also using wind turbines to assist the required power. In our paper we have proposed to use a solar and wind system in Zahur Ahmed Chowdhury Stadium, Chittagong so that we can generate electricity from renewable sources. Besides that we have also proposed to use the generated electricity from the proposed system to charge electric vehicles so that it reduces the CO2 emission from existing traditional fuel vehicles. Our work has focused on new idea to use renewable sources which is the main idea behind smart city or smart management of electricity. We have proposed a unique technique to properly utilize renewable sources for electricity generation as well as proper use to help the environment for a greener tomorrow. II. STADIUMS IN BANGLADESH Similar to other countries, Bangladesh has also some major stadiums in six divisions where the international and national level games are played all the year around. The stadiums situated in different location of Bangladesh are enlisted in Table I. TABLE 1: LIST
OF MAJOR
Location
STADIUMS IN BANGLADESH
Dhaka
1. 2. 3. 4.
Name of the stadiums Sher-e-Bangla stadium, Mirpur Bangabondhu National Stadium. Army Stadium, Dhaka cantonment Fatullah Stadium, Narayangonj.
Chittagong
1. 2. 3.
Zahur Ahmed Chowdhury stadium M. A Aziz Stadium. Cox's bazaar stadiurn, Cox's bazaar.
Khulna
Sheikh Abu Naser stadium.
Sylhet
Sylhet Divisional stadium.
Rajshahi
Shaheed Karuzzaman Stadium.
Barisal
Abdur Rab Serniabad stadium.
According to Bangladesh Power Development Board (BPDB), 80-100 kW internal power supply (without floodlights) is required for conducting a regular match or other events (e.g. Concerts) in these stadiums. So, the aim of our work is to build a national grid integrated microgrid system with the combination of a large photovoltaic system on the rooftop of the stadiums and wind turbines in the empty spaces beside the stadiums. A charging station with electric vehicles charging facility is also proposed which will also be connected to that microgrid system. For the convenience of our research work, Zahur Ahmed Chowdhury stadium in Chittagong has been taken into account and surveyed properly for making a standard load profile.
B. Battery Operated Auto-Rickshaw (Easy Bike)
Battery operated auto rickshaws (locally called Easy bikes) are very popular, cost effective transport of general people as it provides reasonable safety and comfort during travel. Due to its noiseless, pollution free operation, lightweight and limited speed, it does not produce any fatal accidents as the speed is limited for this type of vehicles.
III. ELECTRIC VEHICLES IN BANGLADESH Sustainable Transportation Infrastructure (ST!) is developing rapidly throughout the world. Eco-friendly transportation system is more immune to noise, emission and thus helps to reduce the up growing demand of fossil fuels. Researches on Plug-in Hybrid vehicles (PREV) and Ultra capacitor buses are improving rapidly in all sectors of the transport system. According to the Bangladesh Road Transport Authority (BRTA), more than fifty thousand Electric Vehicles (EV) are available in each major cities of Bangladesh which include battery operated Auto rickshaw, electric motorized rickshaw, electric two wheelers and electric bicycles [4]. But there are no charging stations like other fuel stations, for these vehicles to recharge the batteries. As a consequence, the batteries of these EV's are illegally charged by the owners in their garages without the permission of the authority, which are drawing a significant amount of power from the grid and causing power crisis frequently. So, Integrating EV charging stations with a microgrid system developed for any stadium will be an alternative way and innovative idea to launch in Bangladeshi market. Specifications of all the electric vehicles running in Bangladesh are discussed in this section. A.
Figure 2: Battery Operated Auto-rickshaw (Easy Bike) TABLE II.
CONFIGURATION OF BATTERY OPERATED AUTO-RICKSHAW
[S]
2890* IISO* 1860 mm
Vehicle size
120-ISO km per full charge
Mileage
8-10 hours
Charging time
2S-38 km/h. (Top speed: SOkm/h)
Max. Speed
60V, 1100W
Motor power
60V, I100W
Controller
12V, 140 Ah, * S batteries per one tricyclel
Battery
(5 pcs 12V, 120Ah).
S-6 person
Capacity
11 kWh
Power consumption
C.
Electric Two Wheelers
Electric two wheeler shown in Figure 3 is becoming an essential private vehicle for youths in the South Asian subcontinent. In table III, electric two wheeler's specifications are given in details.
Electric Motorized Rickshaw
Two passengers carrying electric motorized rickshaws are popular means of conveyance for the common peoples of Bangladesh. It is a three wheeled electric vehicle with 48V, 20Ah lead battery and 800W powered Brushless DC motor driving system shown in Figure 1.
Figure 3: Electric Bike TABLE III. Mileage Charging time Max. Speed Motor power
[6]
70-7Skmlh 4-Shours 45-50 kmlh Brushless DC, IS00W, 48V
Charger
IIOV/220V (SOI60Hz)
Battery
Lead Acid Battery, 48V, 960watt h
Capacity
Figure 1: Electric Motorized Rickshaw (Tricycle)
CONFIGURATION OF ELECTRIC BIKE (SCOOTY)
Controller
2 person Digital electronic controller and motor drive system
IV. RENEWABLE ENERGY RESOURCES, LOAD PROFILE AND SIMULATlON TOOL A.
Simulation Tool
Hybrid Optimization Model for Electric Renewable (HOMER) beta 2.68 versions is a widely used simulation tool for designing Microgrid system with grid connection. Based on component cost, installation and maintenance cost, resource availability and connection charges, HOMER generates [7] feasible model with minimum per unit energy production cost. B. Load Profiles Based on Collected Data
Two distinctive load profiles have been made relying on the survey data. For supplying power to the stadiums internal loads (AC loads), average kWh per day required is 1180 with a peak demand of 179 kW and load factor of 0.3. As the rainy season prevails for three months (June-August) in a year, so there are no matches held in the stadium and thus power demand is very low for that season. On the other hand, for EV charging station (DC load), the average kWh / day is 431 with a peak demand of 79kW and load factor of 0.23. In figure 4 and 5, scaled data monthly averages for both load profiles are provided [7].
autocorrelation factor is 0.85, diurnal pattern strength 0.25 and 2 hours of peak wind speed is taken as 15 ms· . In figure 6, monthly wind speed [7] of Chittagong city with an anemometer height of 20m is given. Based on wind speed data, WES 5 Tulipo model of wind turbine is selected which is 2.5kW rated and 3-bladed upwind turbine. It is a wind turbine of 5m diameter blade with the variable speed asynchronous generator connected to IGBT converter [7]. Hub height and lifetime are taken as 16m (Including 3.75m basement) and 15 years. The Installation and capital, replacement and Operation and maintenance (0 and M) costs for a single wind turbine are found as $ 19,350; $ 19,000 and $ 100 [9]. The numbers of wind turbines considered for simulations are 2, 5, 10, 15, 18, 20, 22, 25, 28, 30, and 32. D. Solar Radiation Data and Size o/the Photovoltaic System
Port City Chittagong has a latitude of 22°22' North and 2 Longitude of 91°48' east. Solar radiation (kWh/m /day) data are obtained by HOMER software via Internet. In figure 8, Global Horizontal Radiation curve [7] with Sky clearness (red line in the curve) is presented.
Figure 6: Monthly wind speed of Chittagong city [8] Figure 4: Load profile curve of the stadium (monthly) [7]
Figure 7: Power of WES 5 Tulipo wind turbine [7] Figure 5: Load profile curve of EV charging station (monthly) [7] C.
Wind Resource and Size o/The Wind Farm
Chittagong city is the nearest city of the Bay of Bengal 2 with an average wind speed of 4.65ms· [8]. The stadium is also located in a congenial place to install wind turbines. Altitude of Chittagong is 4m, the wei bulk value is 2,
Photovoltaic system is an integral part of any Microgrid or hybrid power system. Solar panel requires more space than any other renewable power generating system, hence the size of the photovoltaic system is a major concern in our work. On the roof top of any stadium, there is enough space to install a photovoltaic system which in turn saves a huge amount of land. Depending on the solar radiation pattern, considerable photovoltaic system sizes are, 250kW-p, 300kW-p, 350kW-p,
400kW-p, 450kW-p, 500kW-p, 550kW-p, 600kW-p, 650kW p, 700kW-p, 750kW-p and 800kW-p. With a derating factor of 80% and slope of 23.8 degrees, the lifetime of this large scale photovoltaic system is 20 years and ground reflectance is 20%. The capital, replacement and 0 and M cost of I kW solar panel are $ 1154; $ 1050 and $ 2.0 per year [10].
F.
Converter
Converter is an essential part of this large scale renewable power generating system. A converter can be an inverter, rectifier or both. It is required for systems in which DC components serve an AC load or vice versa. Converter sizes considered in the simulations are 20kW, 50kW, 80kW, 100kW, 120kW, 150kW, 180kW, 200kW, 220kW and 250kW. Inverter lifetime and efficiency are taken as 15 years and 90%. Rectifier capacity relative to inverter is considered 100% and efficiency is considered as 85%. The capital, replacement, 0 and M costs are $ 250; $220 and $ 20 per year [12]. G. Grid Connection to Microgrid System
Figure 8: Solar Radiation of each month [7]
E.
Energy Storage Device (Battery bank)
Trojan L16 deep cycle battery is selected for its high ampere-hour rating and long lifetime. Other specifications of Trojan Ll6 battery are Nominal capacity 360Ah, Nominal voltage 6V, and Round trip efficiency 85%, Minimum state of charge 30%, and Float life 10 years, Maximum Charge rate 1A/Ah, Maximum charge current 18A, Lifetime throughput 1,075kWh and Suggested Throughput 1,165 kWh [7]. Figure 9 show the capacity vs. discharge current curve for Trojan L16 battery.
Grid Integrated distributed generation has become a new trend in recent times. In spite of all complicacy, we have considered to connect the whole microgrid system of the stadium to fork out the remaining power to the national grid of Bangladesh for countries up growing economic development with a profitable sell back price. Maximum grid demand is kept zero, which means that the micro-grid system cannot draw power from the grid rather than sales of maximum 200kW per year to the grid. Grid interconnection charge and stand by charges are estimated as $1,87,650 (considering $270/l(W) [13] and $ 100 per year. Scheduled rates of electricity in Bangladesh are given below in Table IV. Figure 10 shows the off-peak and peak period curve of the grid. TABLE IV: SCHEDULED RATES OF NATIONAL GRID ELECTRICITY IN BANGLADESH
[14]
Grid Power Price ($/kWh)
Sell back Rate ($/kWh)
($/kW/month)
Off peak
0.085
0.050
0.577
Flat rate
0.094
0.060
0.577
Peak
0.120
0.080
0.577
Rate (for
llKV line)
Demand Rate
..
Figure 9: Capacity (Ah) vs. Discharge current (A) curve of Trojan L16 Battery
To make a battery bank, batteries per string is taken as 10 (60V). The sizes of the battery bank (strings) for simulation are 40, 60, 80, 100, 120, 150, 180, 200, 250, 300, 320,350 and 380. Capital, replacement and 0 and M costs are $300; $250 and $20 per year [II].
Figure 10: Off peak and peak period curve of grid (without flat rate) [14]
V. HOMER MODEL FOR STADIUM AND SIMULATION RESULTS A. Microgrid Model
The micro grid system for the stadium is designed in HOMER software choosing the option "System is connected to grid". All the components of producing renewable energy are stored in HOMER library. In figure II, designed system is shown with proper arrangement to generate clean energy.
in HOMER simulation tool to find out the optimal size of the system. After simulations are done, HOMER finally showed the exact size and combination to build up the system with minimum production cost of energy of $0.424 (BOT 33.07; I USO= BOT 78) and a renewable fraction of 1.00 which means the system is 100% noiseless and decontaminated power generating project [14]. In figure 12, 13 and 14 final results are presented in details and in Table V and VI shows the production from each resource and elaborately remarked consumption percentages of different loads.
Figure 11: HOMER model for Chittagong stadium. B. Simulation Results
Before the simulations were initiated, all the costs of components and monthly data's of resources were mentioned
Figure 12: Optimized sizes of Components for the stadium’s Microgrid system
Initial Ca pital 700
1&
2000
220
0
Operating Cost (S/yr)
$ 1,99&}5O
92,&G2
Total NPC
Ren. Frac.
$3,1&5,&40
0. 424
1.00
Figure 13: Optimized results for the system
TABLE VI:
ENERGY CONSUMPTIONS OF STADIUM
AND EV CHARGING
STATION
Consumption
kWh/yr
%
AC primary load
430,306
49
DC primary load
157,222
18
Grid Sales
289,262
33
Total
876,790
100
C. Result Analysis
Figure 14: Monthly Average Electricity Production by the system.
TABLE V'
GENERATION FROM DISTINCTIVE ENERGY RESOURCES
Production
kWh/yr
%
PV array
1,021, 381
91 9
Wind farm
97,464
Grid Purchase
0
0
Total
1,118,844
100
In year 2008, BPDB had triggered country's first wind power plant in Kutubdiya, where per unit cost of energy was calculated 40 taka [16] based on total project expenditure and total generating units of each year simultaneously. Meanwhile, to set up a complete solar home system in any residential or commercial area, it expenses 20.14 to 40 taka [17] per unit in accordance with consumptions after government's subsidy of 34% on total infrastructure cost. But HOMER depicts only 33.07 ($0.424) taka per unit cost for harnessing energy from the hybrid microgrid system deployed in the stadium with a
feasible net present cost (NPC) of $3,185,840 equivalents to BDT 24,84,95,520. The system provides 33% of its generation to the grid per year which is really remarkable. D. Limitations to Overcome in Future
Although it is a congenial system to produce clean energy, but it also has some drawbacks which will be our major concerns for any future research work. As stadiums floodlights consume large amount of power, so lighting system should be replaced with LEDs to make a complete standalone system. HOMER illustrates a Battery bank of 2000 batteries that requires large space in spite of selecting the cheapest battery model. In future, high ampere rating and high energy density batteries with cost effective price will be given priority. Besides, Grid Integration of Stadiums microgrid system is also a big challenge. If it is not possible to interconnect the system to the national grid, then stored energy will be sold out keeping a good profit margin [3]. VI. CONCLUSION Achievements in renewable energy technology are now motivating and inspiring us to generate more power for securing our future generation. Advancements in sustainable energy production have enabled us to successfully promote solar home system (SHS) and wind farm of 1MW capacity in Kutubdiya, Chittagong. That is why, installation of large scale renewable power generation through Stadiums Microgrid system is also an advantageous proposed project as it will save a large space for photovoltaic system. Moreover, Electric vehicle charging stations will prevent consumers to consume power from the grid rather than recharging point. As a result, Government has also a chance to impose tax on charging stations for providing legal charging system as being a good practice around the globe. At last, if it is possible to generate 200kW per year from one micro-grid system, then all of the eight major stadiums can contribute more than 1500kW power to the national grid and will save 4562 metric tons of CO2 per year.
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