Design and Cost Benefit Analysis of Grid Connected Solar Pv System for the Aust Campus
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Design and Cost Benefit Analysis of Grid Connected Solar PV System for the AUST Campus
A. Muntasib Chowdhury1♦, I. Alam2♦, M. Rahman3♦, T. Rahman Khan4♦, T. Baidya5♦, A. Hasib Chowdhury6#
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Department of EEE, AUST, Tejgaon, Dhaka, Bangladesh shovon_eee_aust@hotmail.com, 2imtialam@ymail.com, 3lemon_eee@yahoo.com, 4 tarek_eee666@yahoo.com, 5tonmoy_strings@yahoo.com # Department of EEE, BUET, Dhaka, Bangladesh 6 hasib@eee.buet.ac.bd
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Abstract— This paper describes a design and detailed analysis of a grid connected solar PV system for the Ahsanullah University of Science and Technology (AUST) campus. Various design considerations are discussed including the factors and parameters with limited data and information resources available for Bangladesh. Cost analysis reveals that the proposed design is economical and cost effective for the AUST campus. Keywords— Grid-tie solar, solar insolation, sunshine duration, commercial solar power system, Bangladesh.
TABLE II DAILY AVERAGE BRIGHT SUNSHINE HOURS AT DHAKA CITY
Month January February March April May June July August September October November December Average
I. INTRODUCTION Energy is an essential element for industrial and socioeconomic development of a country. However, the linkage between energy and environmental pollution is one of the biggest challenges the world is facing today. In this context, the utilization of solar energy is important for sustainable development of Bangladesh [1]. Bangladesh is situated between 20.300 - 26.380 north latitude and 88.040 - 92.440 east which is an ideal location for solar energy utilization. Dhaka is situated at 23.70990 latitude and 90.40710 longitudes. Daily average solar radiation varies between 4 to 6.5 kWh per square meter. Maximum amount of radiation is available on the month of March-April and minimum on December-January. Monthly global solar insolation and daily average bright sunshine hour in Dhaka city are presented in Tables I and II respectively [2]. In this paper a design is proposed for the Ahsanullah University of Science and Technology (AUST) campus. Commercially available solar PV panels are considered for the design and cost analysis.
TABLE I MONTHLY GLOBAL SOLAR INSOLATION AT DHAKA
II. PV SYSTEM DESIGN FOR AUST CAMPUS The campus of Ahsanullah University of Science and Technology (AUST) is housed in a 10-storied U-shaped building with a total roof area of about 12,500 sq. ft. [3]. The PV system is designed for installation on the roof. A. Location The AUST campus is situated at Tejgaon Industrial Area at the city of Dhaka. The geographical co-ordinates of the campus are 23º45’ north, 90º24’ east. B. Irradiance Irradiance of a site is given by the following relation
Average Insolation , kWh / m 2 Average daily bright sunshine hours The irradiance of the AUST campus can be calculated from Tables I and II. The average insolation of Dhaka city around the year is 4.73kWh/m2. The average daily bright sunshine hours are 7.55 hours. So the irradiance of Dhaka is 626.5 watts per m2. Irradiance =
Month
Solar insolation kWh/m2 4.03 4.78 5.33 5.71 5.71 4.80
Month
Solar insolation kWh/m2 4.41 4.82 4.41 4.61 4.27 3.92 4.73
January February March April May June
July August September October November December
Average insolation
C. Tilt Angle and Shadow of Module Since the sun does not shine perpendicularly on every point of the earth, for maximum efficiency the PV modules are tilted with an angle which depends on the location of the installation. In the northern hemisphere,
solar panels should be tilted to face south and vice versa. An easy way to determine the tilt angle is the latitude of the location. If a place has a latitude Xº north, then panels should be tilted with Xº angle from the horizontal base to face south. The latitude of AUST is 23º45’ north; the tilt angle for the PV modules at site is 23º. The breadth of the PV module chosen for installation is 39.1 inch, if the total shadow length of a module be X, then X = 39.1/cos 23º inch = 42.5 inch.
C, D, E, F, G) is calculated. With provisions for space for maintenance walkways, it is found that a total of 963 modules can be installed. Considering matching the module number with suitable number and size of inverter, 945 modules are suggested for the design implementation E. System Design A typical grid-tie PV system is shown in Fig. 4. Table III presents components chosen for the system and the cost involved.
Sun Light
23º Shadow Tilt Angle
Fig. 1 Tilt angle and shadow of a module
Fig 1 shows the tilt angle and shadow of a module. D. Module Accommodation on Roof Area To calculate module accommodations on the roof of AUST campus, a satellite picture of the roof with dimensions is taken, as shown in Fig 3, using Google Earth [4]. The AUST campus is not parallel to the north south pole in either side. The facing angle is calculated from Google Earth and was found to be 17º.
94 ft
Fig. 4 Circuit diagram of grid-tie PV system TABLE III COST COMPONENTS FOR THE PROPSED SOLAR PV SYSTEM
53 ft
Component
83.7º 87 ft
Description Sharp NU-U235F1 [5] Sunny Mini Central 11000TL [6] Midnite Solar MNPV3 [7] --UniRac [8] GE -40% of all other cost
From the calculated shadow area for a module in Fig 2 and the dimensions of the available roof area in Fig 3 the number of modules that can be placed in each area (A, B,
F. System Capacity Calculation The nominal power output of the proposed solar PV system is 222 kW. The output of a solar PV system is different from its nominal capacity. In [9] numerical values of various factors that reduce the system nominal capacity are presented. These include site location, climatic condition, performances of the PV modules, transmission and other losses are presented. Considering
these factors the effective capacity of the system would be 94 kW. III. COST AND LOAD ANALYSIS A. Energy Consumption Data The energy consumption data for the year 2009 for AUST campus is used for payback calculation [10]. It is presented in Table IV.
TABLE IV ENERGY CONSUMPTION DATA FOR AUST CAMPUS (2009)
Weekends, holidays and semester breaks sum up to an average of 120 days a year for AUST. During these days excess electricity generated by the solar PV system may be fed back to the utility. The government of Bangladesh has yet to finalize the unit rate of buying electricity from a third party solar power provider. Using the load profile in Fig. 5 and the consumption data in Table IV annual average excess energy available for feed back to utility is calculated and presented in Table VI. It is seen that there is practically no excess energy for feed back.
TABLE V DAILY AND MONTHLY AVERAGE ELECTRICITY GENERATION CONSIDERING ESTIMATED CAPACITY
Month January February March April May June July August September October November December
B. Load Profile The load profile for a typical working day is shown in Fig. 5. It is proportionately altered to estimate the load profiles for the different months based on AUST data for the year 2009.
Power Hourly Electrical Load Curve - Typical Working (Kw) Day 150 125 100 75 50 25 0
2: 00 4: 00 6: 00 8: 00 10 :0 0 12 :0 0 14 :0 0 16 :0 0 18 :0 0 20 :0 0 22 24 :00 :0 0: 00
January February March April May June July August September October November December TOTAL
PV Energy estimated production (kWh/day) 1165.8 1219.4 1179.2 1192.6 1098.8 656.6 683.4 777.2 804 1018.4 1152.4 1192.6
Annual Excess production (kWh) 139.5 4088 554.9 4782.4
Hour
Electrical load (Kw)
Fig. 5 Load profile for a typical weekday at the AUST campus
C. Electricity Production Estimation The estimated capacity of the solar PV system is around 94 kW. Electricity tariff for medium voltage, general purpose (11 kV) consumer is USD 0.055/kWh [USD 1 = BDT 69.06] [11]. Using this info together with daily average bright sunshine hours for each month for Dhaka, daily and monthly average electrical energy generation presented in Table V. It is seen that the yearly average energy generation is 258,783 kWh with a value of 14240 USD.
D. Simple Payback Analysis A simplified form of cost/benefit analysis is the simple payback technique. This method yields the number of years required for the improvement to pay for itself [12].
Simple payback time = Cost of the system , years Annual savings
IV. CONCLUSION This paper presents a solar PV system for the AUST campus. Detailed design including system specification has been worked out. Detailed energy generation and cost analysis shows that though the payback time is high for the estimated capacity, yet the cost per unit is somewhat feasible for 25 years scale under the present state. REFERENCES
[1] [2] [3] [4] [5] L. Pillay , Kh.S.Karimov, "Photo-voltaic System," in ICECE 2004, paper 045, p. 179. (2009) REEIN website. [Online]. Available: http://www.reein.org/ solar/resource/index.htm. (2010), AUST website. [Online]. Available: http://www.aust.edu/ campus_info.htm. (2010) Google Earth website. [Online]. Available: earth.google.com “Sharp NU-U235F1 datasheet,” Sharp Electronics Corporation, CA. “Sunny Mini Central 11000TL datasheet,” SMA Solar Technology, USA. “Midnite Solar MNPV3 datasheet,” Midnight Solar, USA. “Master Price List,” U-LA, Unirac, 2008. M. Rezwan Khan, M. Fayyaz Khan, “Design considerations for solar PV home systems in Bangladesh,” Proc. ICECE 2002, pp. 208-211, 2002. Meter Reading Book, Engineers’ Office, Ahsanullah University of Science and Technology, Dhaka. Tariff Rates on DPDC, available at: http://www.dpdc.org.bd/dpdc/tariff.php. Leena Cholakkal, Cost-benefit analysis of a Building Integrated Photovoltaic Roofing System for a school located in Blacksburg, Virginia, M.Eng.Thesis,Virginia Polytechnic Institute and State University, Blacksburg, Virginia,May 9, 2006. Monthly electricity bill, Ahsanullah University of Science and Technology, Dhaka.
Table VI shows the savings achieved from the electricity bills with and without PV output. The electricity bills considered here are of 2009[13].
TABLE VI SAVINGS COMPARING ELECTRICITY BILL WITH AND WITHOUT PV
Month
Electricity bill without PV (USD) 1981 1651 1981 2641 4044 5038 5840 4998 2701 3962 3632 2641 TOTAL
January February March April May June July August September October November December
Electricity bill with estimated PV production (USD) 586 332 570 1260 2730 4278 5023 4068 1770 2743 2297 1214
Total cost of the system, USD Annual savings from Electricity bills For nominal capacity, USD For estimated capacity, USD Simple Payback Time (Estimated), Years
: 1126571 : 33643 : 14240 : 79.11
The payback time is as usual on the higher side. E. Energy Cost Per Unit Considering 25 years as the system life, the cost per unit of energy produced by the solar PV system is calculated and presented in Table below. Total system cost, USD Average daily bright sun hours, hr Estimated capacity of the system, kW Avg. energy generated per day, kWh Energy generated in 25 years, kWh Cost per unit energy, USD : 1,126,571 : 7.55 : 94 : 709.7 : 6,476,013 : 0.17396
