ISSN Vol.03,Issue.10 May-2014, Pages:

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1 ISSN Vol.03,Issue.10 May-2014, Pages: MAY ZIN PHYU 1, AUNG ZE YA 2 1 Dept of Electrical Power Engineering, Mandalay Technological University, Mandalay, Myanmar, winnerboy.mzp@gmail.com. 2 Dept of Electrical Power Engineering, Mandalay Technological University, Mandalay, Myanmar, dr.aungzeya010@gmail.com. Abstract: For domestic consumers in the remote areas that are not served by the main electrical grid network, diesel generators are the usual choice for electrical supply. As a result, plenty of servicing and maintenance needed to be done onto these diesel generators. Thus, researchers have come out with the ideas of introducing wind turbine working together with the diesel generators to form a hybrid power system. The propose hybrid system was studied on the availability of wind energy resource data and designed the optimal system according to the demand load. A case study of a typical wind-diesel hybrid system is presented. It is shown that the reductions in operating costs achieved by using storage can be significantly increased using the HOMER Software. Modeling is completed using the simulation tool HOMER and results are presented for several different system configurations. Special focus was put on sizing the optimal system which gives the lowest levelized cost of energy. Keywords: Diesel Generator, HOMER, Wind, Wind-Diesel Hybrid System. I. INTRODUCTION Our current living standard could not be maintained without energy. In numerous remote and rural areas in the world, a noteworthy number of domestic consumers, farms and small businesses are not connected to a main electrical grid system. This is exceptionally real in the developing countries, where large distances and the lack of capital are some of the obstacles to the development of a grid system. In recent years, hybrid wind-diesel system has become viable alternatives to meet environmental protection requirement and electricity demands. A combination of one or more resources of renewable energy, called hybrid, will improve load factors and help saving on maintenance and replacement costs as the renewable can complement each other. High initial capital of the hybrid is a barrier to adopt the system thus the needs for long lasting, reliable and cost-effective system. Designing of a hybrid system require correct components selection and sizing with appropriate operation strategy. In Proposed the optimal configuration for hybrid systems should be determined by minimizing the kilowatt-hour (kwh) cost. Software, hybrid optimization model for electric renewable (HOMER) is to find optimum sizing and minimizing cost for hybrid power system with specific load demand. Studies on genetic algorithm are done to find the optimum sizing as well as the suitable operation strategies to meet different load demand. Applications of hybrid systems range from small power supplies for remote households providing electricity for lighting or water pumping and water supply to village electrification for remote communities. Mixed combinations of renewable energy systems are also possible, that is applications where different renewable energy technologies are applied in one location without the systems being necessarily interconnected in one electricity grid. II. CONFIGURATION OF WIND-DIESEL HYBRID SYSTEM A power system with electricity production from both a diesel generator and a wind turbine is more accurately described as a hybrid power system or hybrid energy system. Hybrid power systems incorporate more than one piece of equipment for electricity production as well as storage, power conditioning components, and system controls. The classic hybrid system is based on a fossil fuel engine generator, energy storage in the form of batteries and a power converter. The configuration of the system can vary based on the system size. Small systems usually focus on a DC bus bar and include small renewable generation devices and enough storage for a few days. The production of AC power comes from a power converter or diesel generator. Large systems focus on the AC bus bar. These systems utilize larger equipment and storage in order to cover fluctuations in power production. Hybrid systems installed in remote communities follow these guidelines as well. In all cases, the overall efficiency and expected maintenance costs of the fossil fuel engine generator will depend on the number of starts and stops it experiences. A. AC Based Hybrid Power System A new development for small remote communities has been the deployment of smart power electronics. Utilizing an 2014 SEMAR GROUPS TECHNICAL SOCIETY. All rights reserved.

2 MAY ZIN PHYU, AUNG ZE YA AC distribution grid and a smart inverter, the system s generation equipment can meet the AC load demand without first charging batteries. In this type of system, a wind turbine, photovoltaic array, a diesel generator, or a combination of the three, can meet the AC load with the incorporation of improved power electronics and control. The benefits are that more generation equipment can be added as needed and at greater distances without much modification to the overall system structure. Disadvantages include lower efficiencies if battery storage is necessary, high costs, and the use of technologies that would be difficult to service in remote areas. [3] geographical location, the propose system is considered for Da Min Seik Gyi Village at Ye Township in Mon State which location is between latitude N and longitude E, it s altitude is ft. There are about 145 households with 550 of local people in this village. Location of Da Min Seik Gyi and Daily load profile is shown in Fig.1 and Fig.2. The average daily energy consumption is 364kWh per day. Electricity is provided for lighting, pumping and domestic facilities such as TV, DVD player, fan and refrigerator. B. DC Based Hybrid Power System For small remote communities that provide less than a few hundred kilowatt-hours per day, a battery bank is the main device of power supply. The batteries operate as a direct current bus and central connection point. Small wind turbines or photovoltaic convert available resources to electric power that is rectified to DC to charge the battery bank. A diesel generator is available to charge the battery bank when wind and solar power availability drops below demand. The AC load demand is met by inverting the DC power supplied from the battery bank. [3] C. Parallel Hybrid Power System In parallel hybrid system configuration, the diesel generator and renewable energy generators supply a portion of the load demand directly. There are two types of subconfigurations of this hybrid system. These are the DCcoupled and AC-coupled configurations. The DC-coupling configuration system utilizes a bi-directional inverter, which is operated in parallel with the diesel generator and can act as inverter and rectifier/battery charger. It is a DC-coupled configuration hybrid system in a sense that the renewable energy sources are connected together at the DC bus to the battery and supply the AC load via the bi-directional inverter. Here, the AC power from the wind turbine must be converted into DC by utilizing AC/DC converters or rectifiers before power is delivered to the DC-bus. The parallel hybrid power system with DC-coupling configuration can further be improved by connecting all of the renewable generators to the AC-bus to perform an ACcoupling configuration. The load can be supplied from the renewable energy supplies in parallel with the diesel Genset. A bidirectional inverter is utilized here such that the battery can either supply the load or be charged depending upon the load requirement and the status of other energy sources. This type of configuration is also referred to as centralized AC-bus topology in a sense that all the energy generators are connected at the AC-bus and the load is supplied at a single point. [3] III. PROPOSED SITE In this study, the south of Myanmar is selected for using renewable source of wind and diesel hybrid system including battery bank as a backup system in order to provide the sufficient energy under no wind day. According to the Fig.1. Location of Da Min Seik Gyi Village [6]. Fig. 2. Daily Load Profile. IV. SYSTEM SCHEMATIC Many individuals and organizations are now considering installing small turbines to supply electricity to their houses and commercial buildings. Small-scale wind energy refers to wind turbines rated less than 50 kw which are generally intended to supply electricity to buildings, and which may or may not be connected to the grid. This is distinct to utilityscale wind turbines, generally rated between several hundred kilowatts and a few megawatts each, which form wind farms onshore (predominantly in rural areas). For any given turbine, site and installation setting (including height), the principal factor affecting the amounts of electricity generated and carbon saved is wind speed. A wind speed data was also obtained from meteorological department in Myanmar, which showed the average wind speed of the areas to be 4 m/second at 10 meter high. The following schematic, Fig. 3 represents Wind-Diesel hybrid system.

3 Fig. 3. Wind-Diesel Hybrid System [3]. V. COMPONENTS OF THE PROPOSED SYSTEM A. Wind Resource The average wind speed for each month in Ye Township in Myanmar is shown in Fig. 4. The higher the tower height; the more increase the wind speed. At 25m height, one year wind speed data is described in Fig. 5. In this modeling, 50 kw AC rated power is used for the wind turbine. The power curve and cost curve for wind turbine is shown in Fig. 6 and Fig. 7 respectively. The life time is taken as 25 years and hub height is 25 meters for the wind turbine considered. The following Table I shows wind turbine parameters. [7] TABLE I: WIND TURBINE PARAMETERS Fig. 5. Wind Speed Data at 25m height. Fig. 6 Power Curve of a Wind Turbine. Fig. 7. Cost Curve of a Wind Turbine. B. Diesel Engines Diesel generators and combustion engines are mainly used for off-grid generation. Low installed capacity, high shaft efficiency, suitable for start-stop operation, and high exhaust heat are some of the advantages of combustion engines. These engines convert heat from the combustion into work via rotation of shaft. The shaft is directly coupled to the generator and electricity is produced. They run at a speed defined by the frequency of supply grid. In this modeling, 30kW and 20kW diesel engines are used along with the wind turbine. Fig. 8 and 9 show the cost curves of diesel generator rated for 30kW and 20kW. The design generator parameters are cleared in Table II and III. [4] Fig.4. Wind Speed Data for Da Min Seik Gyi.

4 TABLE II: DIESEL GENERATOR PARAMETERS Size (kw) 30 Total Capital cost ($) Replacement cost($) Annual maintenance cost($) 1.2 Lifetime(hrs) MAY ZIN PHYU, AUNG ZE YA Fig. 8. Cost Curve of 30 kw Diesel Generator. TABLE III: DIESEL GENERATOR PARAMETERS Size (kw) 20 Total Capital cost ($) Replacement cost($) 8014 Annual maintenance cost($) 1.0 Lifetime(hrs) Fig.10. Cost Curve of 6FM200D Battery. TABLE IV: BATTERY PARAMETERS Nominal capacity (Ah) 200Ah Nominal voltage(v) 12V Round tip efficiency (%) 80% Min. state of charge (%) 40% Max charge rate 1A/Ah Total capital cost($) 480 Replacement cost($) 480 Annual maintenance cost($) 20 Life time(yrs) 5 D. Power Converter A power electronic converter is used to keep the flow of energy among AC and DC components. The parameters of the converter are shown in Table V. Cost Curve of converter is shown in Fig. 11. TABLE V: POWER CONVERTER PARAMETERS Size (kw) Total Capital cost ($) 900 Replacement cost($) 850 Annual maintenance cost($) 20 Lifetime(yrs) 15 Fig.9. Cost Curve of 20 kw Diesel Generator. C. Battery The lead acid battery is considered for this study and the style of battery that used for the system is Vision 6FM200D model, Table IV is provided the battery parameters. Cost Curve of 6FM200D Battery is shown in Fig. 10. Fig. 11. Cost Curve of Converter.

5 E. Load Details The load details for the hybrid system are shown in Fig. 12. The seasonal profile of load is considered with peak load as 47.1 kw. Load factor = F. Equations The power generated by a wind turbine can be expressed as: Where A is the area of the rotor blade, v wind is the wind speed, ρ is the air density and Cp is the power coefficient. The power coefficient Cp is a function of the tip speed ratio λ and the blade pitch angle β. [1] (1) TABLE VI: OPTIMAL MICRO-GRID PLAN CONFIGURATION FOR VARIOUS CASES The above Table VI describes optimal micro-grid plan configuration for various cases. The other major component of the wind-diesel hybrid system after diesel generation set is the wind energy conversion system or wind turbine. The modern wind machines are very efficient and found in big sizes, capacity wise. The following figure, Fig. 14 is configuration of simulation results at optimal condition. Fig. 12. Load Details for hybrid Wind-Diesel System. Induction generators are very populated in wind turbine applications. They are reliable and well developed. Induction generators are loosely coupled devices i.e. heavily damped and can have ability to absorb slight changes in the rotor speed whilst remaining connected to electric grid. [2] Fig.14. Configuration of Simulation Results. VI. CASE STUDY OF HYBRID SYSTEM The main components of a micro-grid connected winddiesel hybrid system are diesel generators, wind turbine, battery, and converter to link AC and DC bus. A typical wind-diesel hybrid system used in homer software is shown in Fig. 13. Fig. 13. Equipment of the hybrid energy system. Fig. 15 Component Cost of Case-3. Simulation results of case-1, case-2 and case-3 are shown in Table VII and comparisons of environmental emissions from various configurations is shown in Table VIII. For case- 3, component cost, monthly average energy and cash flow are shown in Fig. 15, 16 and 17.

6 MAY ZIN PHYU, AUNG ZE YA TABLE VIII: COMPARISONS OF ENVIRONMENTAL EMISSIONS FROM VARIOUS CONFIGURATIONS Fig.16. Monthly Average Energy of Case-3. Fig.17. Cash Flow of Case-3. TABLE VII: SIMULATION RESULTS OF CASE-1, CASE-2 AND CASE-3 VII. DISCUSSIONS According to the Table VII and VIII, the Case-3 is the best optimum model among the three Case Studies. The unit cost of electricity of Case-3 is less than the two other Case Studies because the cost per unit of Case-3 is $ On the other hand, fuel consumptions of diesel generation for Case-1 and Case-2 are more than for Case-3 because the Case-3 needs to generate only one diesel generator. As the pollutant emission, the Case-3 is also less than the two other Case Studies. As mentioned before, one of the main objectives of this work is to reduce emissions by using green energy sources. The results presented in Table VIII shown that the renewable micro-grid in Case-2 significantly reduces the total system emissions as compared to Case-1. However, although Case-3 emits more than the renewable micro-grid, it is still quite environmentally friendly when compared to the diesel micro-grid. The mixed micro-grid (Case-3) is the most economic optimal choice. VIII. CONCLUSIONS The hybrid system, case-3, becomes feasible when wind speed is greater than 11 m/s and the fuel price is less than 0.9 $/L. The maximum annual capacity shortage did not have any impact on the system optimization. Since the wind data was not available for the village, so it was taken from a nearby the city and used for simulation purpose. However, the scope of the case study did not focus on the implementation issues, but instead makes the cases for further investigation and surveying the actual data for the planning of the proposed project. According to this analysis, the case study 3, wind-diesel-battery hybrid system, is generally a viable option for rural area in Ye township, Mon state. Finally, HOMER is found to be a very helpful tool for the micro-grid planning and dispatching. IX. ACKNOWLEDGMENT First of all, the author is grateful to express her deepest gratitude to His Excellency Dr. Ko Ko Oo, Ministry of Science and Technology, for the opening of Special

7 Intensive Courses leading to Doctor of Philosophy of Engineering program at Mandalay Technological University. Special thanks are due to, Dr. Myint Thein, Pro Rector of Mandalay Technological University, for his motivation, supports, guidance and for giving the permission to submit this paper for the Doctor of Philosophy of Engineering (PhD), degree at Mandalay Technological University. Special thanks are offered to Dr. Khin Thuzar Soe, Associate Professor and Head of Department of Electrical Power Engineering, Mandalay Technological University, for her encouragement, constructive guidance and kindly advice throughout the preparation of this paper. The author especially indebted and grateful to supervisor Dr. Aung Ze Ya, Associate Professor, Department of Electrical Power Engineering, Mandalay Technological University, for his encouragement, valuable supervision, suggestions, kindly permission and guideline during the entire course for the preparation of this paper. And the author would like to convey her gratitude to all persons who were directly or indirectly involved towards the successful completion of this paper. X. REFERENCES [1] John Twidell and Tony Weir, Renewable Energy Resources, 2 nd edition, New York, [2] J.F. Manwell, J.G. McGowan, A.L. Rogers, Wind Energy Explained:Theory, Design and Application, 2 nd edition, New York, [3] Leake E. Weldemariam, Genset-Solar-Wind Hybrid Power System of Off- Grid Power Station for Rural Applications, Delft, the Netherlands, July [4] Perkins Diesel Generator Price List. Available [Online]: Gnerat or-price-list.html. [5] Getting Started Guide for HOMER Beta Version 2.68, Feb 8, [6] [7] [8] [9] Author s Profile: Ms. May Zin Phyu, Date of Birth , BE (Electrical Power Engineering) from Technological University (Mawlamyine), Myanmar, ME (Electrical Power Engineering) from Technological University (Mawlamyine), Myanmar, Currently she is an assistant lecturer in the department of Electrical Power Engineering, Technological University of Mawlamyine, Myanmar. She is now attending Ph.D degree (Electrical Power Engineering) in Mandalay Technological University, Myanmar. Her field of interest is Renewable energy, Power system protection and High Voltage Engineering.