Optimum Design and Evaluation of Hybrid Solar/Wind/Diesel Power System for Masirah Island

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1 Optimum Design and Evaluation of Hybrid Solar/Wind/Diesel Power System for Masirah Island Hussein A Kazem 1, Hamood A S Al-Badi 1 Ahmed Said Al Busaidi 2 Miqdam T Chaichan 3 1 Faculty of Engineering, Sohar University, Sultanate of Oman 2 The Research Council of Oman, Sultanate of Oman 3 University of Technology, Baghdad, Iraq Abstract This paper addresses the requirements of electrical energy for an isolated island of Masirah in Oman. The paper studied the possibility of using sources of renewable energy in combination with current diesel power plant on the island to meet the electrical load demand. There are two renewable energy sources used in this study, solar and wind energy. This study aimed to design and evaluate hybrid Solar/Wind/Diesel/Battery system in term of cost and pollution. By using HOMER software, many simulation analyses have been proposed to find and optimize different technologies that contain wind turbine, solar photovoltaic and diesel in combination with storage batteries for electrical generation. There are four different hybrid power systems were proposed, diesel generators only, wind/diesel/battery, PV/diesel/ battery, and PV/wind/diesel/battery. The results analysis shows that around 75% could reduce the cost of energy by using PV/wind/diesel hybrid power system. Also, the greenhouse emission could be reduced by around 25% compared with these by using diesel generators system that currently utilize in the Masriah Island. The Solar/Wind/Diesel hybrid system is techno-economically viable for Masirah Island. Keywords-Hybrid power system; renewable energy; cost of energy; diesel; photovoltaic; wind 1. Introduction In Oman, the electricity is mainly produced by using natural gas and diesel. There is a limitation in reserve of fossil fuel and raises the level of pollution caused by these types of fuel. Masirah Island considered as the largest island in Oman as shown in Fig. 1. It locates in the Arabian Sea about 15 km from the coast of Oman. It is about 300 km south of Muscat the capital of Oman. The Island lays latitudes and north. It is between about 5 and 15 km wide and about 65 km long. The electrical demand in Masirah Island is covered by using diesel generators power station. However, this diesel power system that depends on diesel fuel will sooner or later become a barrier for the island due to increasing in the cost of the fuel and the requirement of transportation. In spite of the geographical difficulties to deliver the fuel to the remote areas, the diesel power generation station needs maintenance. The environment pollutions issues are all factors indicate to use another type of alternative source to cover the required power demand of the Island. The main renewable energy sources available in Masirah Island are the wind and solar energies. A high level of solar power found in all regions of Oman, and this level of solar energy is varying from location to another. The solar energy density of the northern parts of Oman areas and the desert is very high compared to the coastal regions. Whereas the southern parts of Oman 1

2 areas has the lowest solar energy density [1, 2]. Also, the wind speed in Oman is relatively higher comparing with that of the other Gulf countries. The maximum wind energy in Oman becomes more economically due to the increasing in the fossil fuel cost such as gas and oil. The southern regions of Oman have the heights potential wind speed comparing with the northern regions. The wind potential in Masirah Island is one of the highest wind potential energy in Oman. The average wind speed of Masirah Island is around 5 m/s per month. This value based on measurement done for 12 years at a height of 10 m above the sea level [3]. One of the options to distribute the electrical energy for several isolated areas is the using of renewable energies alone or in combination with other systems. One of the systems used in the generation is the hybrid generation system as shown in Fig. 2. The hybrid system consists of PV modules, wind turbines, diesel generator, charge controller, batteries, inverter and the rest of the balance-ofsystems. The benefits of this system are to make the electrical system more reliability and reduce the cost of energy. There are many countries around the world including the countries with rich fossil fuel are investigating the production of electrical power for isolated areas by using renewable energy resources [4]. Figure 1. Masirah Island on the map 2. Power System and Electrical Load in Masirah Island: In Massirah Island, there is a central power station that contains ten diesel-powered generators are used to meet the electrical power demand in the Island. The power rating ranges for individual power generator starts from 265 kw to around 3136 kw. The power station total capacity is around 8478 kw. Recently, new generator added with 4000 kw rating. The commercial and government demand of power in Masirah Island is about 40% of the generated power. The residential demand consumes about 54% of the power, and the rest 6% employed in the industrial load [5]. In particular, the peak power demand is about 8.2 MW and the average demand is about MW with average consumed kwh per day equal to MWh/d. The monthly electrical load for Masirah Island in 2015 illustrated in Fig. 3.This work based on hourly 2

3 meteorological data provided by Ministry of Transport and Communications; Directorate General of Civil Aviation and Meteorology 2013, and Rural Areas Electricity Company, Oman Figure 2. PV/Wind/Diesel/Battery Hybrid System Configuration Figure 3. Monthly electrical load in Masirah Island National Renewable Energy Laboratory s (NREL) Hybrid Optimization Model for Electric Renewables (HOMER Pro) has been used to design, evaluate and perform the feasibility analysis of the hybrid system. A. The Diesel Power Station in Massirah Island: There are four types of the generator are used in Masirah Island power station with different capacities, and these types are KHD generator, Caterpillar generator, Cummins generator and MBS generator as shown in Table 1. 3

4 Table 1.The rated power capacity of existing diesel generators in Masirah Island. Engine NO Engine Ref Engine rated capacity (kw) Engine site capacity (kw) G1 KHD G2 KHD G3 Caterpillar G4 Caterpillar G5 Cummins G6 MBS G7 MBS G8 MBS G9 MBS G10 MBS The additional community of Masirah Island has no electrical load data. The total demand of energy for the entire community was estimated by using an hourly energy simulation program that utilized for load electrical generation for one residential building. The average electrical load for 500 residential buildings was estimated by using equest simulation analysis program [6]. The total electrical load in Masirah Island never remains the same of around 8 MW. However, the scientific estimations declare that it increases to more than 23 MW due to the adding of the additional community that contains around 500 residential. The current capacity of the electrical power station of the Island that contains ten generators of different types with a total capacity of 8.5 MW cannot meet the future demand [7]. B. Electrical Load of Masirah Island Figure 4 shows the average daily load (kw) profile of the Masirah Island for January month. The average daily load is varying between about 2500 kw at (10:00-11:00 and11:00-12:00) and 3350 kw at (18:00-19:00, 19:00-20:00 and 20:00-21:00). The annual peak load observed between 18:00 h and 19:00 h and it equal to 4,756 kw with the peak value of 8,200 kw. For the last eight hours starting from 16:00 o clock till the end of the day average daily load shows high power consumed by the load and it fluctuated between around 3250 kw and 3350 kw. At the morning hours, the electrical power that was consumed by the load is a little bit low comparing with that of the evening hours, and it fluctuated between around 2500 kw and 2700 kw. The average daily load profile of Masirah Island is about 2770 kw and the average power consumed by the load in (kwh/d) is about 11,435 kwh/d. 4

5 Figure 4. The average daily load profile for January month each of Masirah Island 3. Renewable Energy in Masirah Island A. Wind Energy Source The daily wind speed per one year of Masirah Island was recorded from the surface of the earth at a height of 10 m, for each day. Then, the average wind speed of days for each month was calculated, and the results listed as shown in Table 3. Table 3.The average wind speed of days for each month of Masirah Island. Month Average wind speed (m/s) January February March April May June July August September October November December The charts in Figure 5 show the average wind speed of days for each month of the year in Masirah Island. The wind speed of the Island is varying between about m/s and m/s. It is clear that the maximum average of the wind speed found in June and it equal to m/s. On the other hand, the minimum average of the wind speed is found in December and it equal to m/s. For the beginning four months of the year January, February, March and April the average wind speed approximately the same and it fluctuated between around 4.2 m/s and 4.5 m/s. Then, it increased till it achieved its maximum value in June. Then the average wind speed started to decrease till it reached the minimum average wind speed in December. The average wind speed of Masirah Island is about m/s which are good enough to use the wind turbine to generate electrical power in the island. 5

6 Figure 5. The average wind speed of days for each month in Masirah Island. The average of the wind speed considered as a good indicator of the suitability of the installation of a wind turbine in a given area or location. Most months of the year have average wind speed in Masirah Island is above 4 m/s. In general, the values of the average wind speed above 5 m/s with few months below 4 m/s considered a good indicator to use the wind turbine in a specific location [7]. There are five months have average wind speed greater than 5 m/s and only two months have average wind speed below 4 m/s. According to these results, the average wind speed of Masirah Island is considered an excellent indicator to use the wind turbine on the island. B. Solar Energy Source Table 4 shows the position parameters that should considered as the input of the solar resource of Masirah Island. HOMER software has been used to model the system in this study [8, 9]. HOMER provides directly the solar resources from NASA Surface meteorology and Solar Energy database by entering the GPS coordinates [10, 11]. Table 5 shows the daily radiation of solar energy in Masirah Island. Table 4.The parameters used for input of the solar resource of Masirah Island. The parameter The value Latitude 20 o 40 North Longitude 58 o 53 East Time zone GMT + 4:00 Table 5. The average radiation for each month of the year of Masirah Island Month The daily radiation (kwh/m 2 /d) January February March April May June

7 July August September October November December The charts in Figure 6 show the average daily radiation (kwh/ m 2 /d) of days for each month on Masirah Island. The average daily radiation is varying between about kwh/ m 2 /d and kwh/ m 2 /d. The maximum average of the daily radiation found in March, and it is equal to kwh/ m 2 /d. On the other hand, the minimum average of the daily radiation was found in December and it equal to kwh/ m 2 /d. For the first half of the year from January to June, the average daily radiation was approximately the same. It fluctuated between around 6.38 kwh/m 2 /d and 6.58 kwh/m 2 /d, and then it decreased till it reached the minimum value in December. The average daily radiation of Masirah Island is about 6.38 kwh/m 2 /d. Figure 6. The average daily radiation of solar energy in Masirah Island The average of the wind speed considered as a good indicator of the suitability of the installation of a wind turbine in a given area or location. The average daily solar radiation of most months of the year in Masirah Island is above 5 kwh/m 2 /d. A reliable power comes from the photovoltaic needs that the average solar radiation should have the annual radiation of above 4 kwh/m 2 /d and a constant trend all the days of the year. All months have average solar radiation above 4.5 kwh/m 2 /d.there are seven months have average solar radiation above 6 kwh/m 2 /d and only two months have average solar radiation below 5 kwh/m 2 /d. According to these results, the average solar radiation in Masirah Island is considered a superb indicator to use the photovoltaic on the island. 4. Discussion of different Power systems used for Masirah Island Load A. Diesel Generators Power System Various scenarios with several simulations have been made by considering different PV and wind turbine capacities with and without battery storage systems. HOMER schematic diagrams for Masirah Island diesel power station presents in Figure 7. The load demand indicated in the diagram. In this simulation only Masirah power station which contains diesel generators are used. There are ten generators used with different capacities; two generators of type KHD with rated capacity of 3136 kw and site capacity of 2509 kw. Five generators of type MBS used with rated capacity of 265 kw and site capacity of 212 kw. Two generators of type Caterpillar with 7

8 rated capacity of 1000 kw and site capacity of 800 kw. Also, one generator of type Cummins with rated capacity of 1000 kw and site capacity of 800 kw. Figure 7. Masirah Island diesel power station (diesel generators) After running the model, the number of feasible solutions that found is 16. Out of these solutions, there are 3 best solutions arranged according the minimum system cost of energy (COE) and net present cost (NPC) as shown in Table 6. In the optimal solution, all generators are chosen. The total net present cost (NPC) is $102,872,600 with operation cost of 8,639,100 $/year and the cost of energy equals to $/kwh. Table 7 shows greenhouse gases for diesel generators system for this case. Table 6.The optimum solution for Masirah Island load demand by using diesel generators Table 7. Greenhouse gases for diesel generators system Pollutant Emission (kg/yr) Carbone dioxide 5,887,234 Carbone monoxide 16,247 Unburned 1,563 hydrocarbons Particular matter 1,036 Sulfur dioxide 11,058 Nitrogen oxides 138,615 Total 6,055,753 B. PV/Diesel Generators Hybrid Power System 8

9 HOMER schematic diagrams for Masirah Island diesel power station with PV array presented in Figure 8.In addition to the diesel generators and PV panel, there is battery bank and converter. Figure 5.PV/Diesel power system In this simulation the quantities of the batteries considered are (100, 200, 250,300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 and 2000). The cost of one battery is 1250$ with the maintenance cost of 10$/yr. The installation cost and maintenance cost for chosen 1kW converter are taken as 900$ and 8$ respectively. Twenty-one different sizes of converter (4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900 and 6000) are taken in the model and the lifetime of the unit is considered to be 15 years with 90% efficiency. The size of the photovoltaic panels is considered to vary between 5000 kw and kw. The installation cost of the solar energy system took as 2000$ per kw, and the replacement cost assumed as 1750$ per kw. The lifetime of the PV array is considered to be 25 years. After running the model for the number of feasible solutions that were found as Out of these solutions, there are 3 best solutions arranged according the minimum system cost of energy (COE) and net present cost (NPC) as shown in Table 8. In the optimal solution, all generators are chosen, and the size of the PV panel is 7000 KW. The total net present cost (NPC) is $95,492,448 with operation cost of 6,194,544 $/year and the cost of energy equals to $/kwh. Table 9 shows greenhouse gases for the hybrid system (PV/Diesel system). Table 8. Best 3 optimum solutions for Masirah Island load demand by using PV/diesel generators system Table 9. Greenhouse gases for hybrid system (Diesel generators and PV system) 9

10 Pollutant Emission (kg/yr) Carbone dioxide 5,297,382 Carbone monoxide 12,746 Unburned hydrocarbons 1,286 Particular matter 984 Sulfur dioxide 10,341 Nitrogen oxides 113,864 Total 5,436,599 C. Wind/Diesel Generators Power System HOMER schematic diagrams for Masirah Island diesel power station with wind turbines presents in Figure 6. Each generator type is indicated in the diagram as well the load demand. Figure 6. diesel power station with wind turbine system In this simulation the quantities of the wind turbine considered are (100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500 and 1600). The installation cost of the wind turbine system is taken as 2000$ for each wind turbine, and the replacement cost considered as 1750$ for each wind turbine. The lifetime of the wind turbine system is considered to be 20 years. After running the model, the number of possible solutions that found is 272. Also, out of these solutions there are 3 best solutions are arranged according to the minimum net present cost (NPC) of the system and the cost of energy (CEO) as shown in Table 10. In the optimal solution, all generators were chosen. MBS with total site capacity of 1060 kw, and Caterpillar with total site capacity of 1600 kw. KHD with total site capacity of 5018 kw and Cummins with total site capacity of 800 kw. The total net present cost (NPC) is $89,015,264 with operation cost of 2,885,259 $/year and the cost of energy equals to $/kwh as shown in Table 10. Table 11 shows greenhouse gases for hybrid (Diesel generators and wind turbine system). 10

11 Table 10. Best optimum solution for Masirah Island load demand by using diesel generators and wind turbine system Table 11. Greenhouse gases for hybrid (Diesel generators and wind turbine system) Pollutant Emission (kg/yr) Carbone dioxide 4,628,352 Carbone monoxide 13,836 Unburned hydrocarbons 1,406 Particular matter 926 Sulfur dioxide 9,984 Nitrogen oxides 119,318 Total 4,773,822 D. PV/Wind/Diesel Generators Power System HOMER schematic diagrams for Masirah Island diesel power station with PV/Wind presented in Figure 7. Each generator type indicated in the diagram. Figure 7. Diesel power station with wind turbine and PV system In this simulation the quantities of the wind turbine considered are (100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500 and 1600). The installation cost of the wind turbine system is taken as 2000$ for each wind turbine, and the replacement cost considered as 1750$ for each wind turbine. The lifetime of the wind turbine system is considered to be 20 years. The size of the photovoltaic panels is considered to vary between 5000 kw and kw. The installation cost of the solar energy system is taken as 2000$ per kw, and the replacement cost deemed as 1750$ per kw. The lifetime of the PV panel is considered to be 25 11

12 years. The quantities of the batteries considered are (100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900 and 2000). The cost of one battery is 1250$ with the maintenance cost of 10$/yr. The installation cost and maintenance cost for chosen 1kW converter are taken as 900$ and 8$ respectively. Twenty-one different sizes of converter (4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900 and 6000) are taken in the model and the lifetime of the unit is considered to be 15 years with 90% efficiency. After running the model, the number of possible solutions that found is Out of these solutions, there are 3 best solutions arranged according to the minimum net present cost (NPC) of the system and the cost of energy (CEO) as shown in Table 12. In the optimal solution, the PV/Wind/Battery/Diesel generators are chosen. The total net present cost (NPC) is $28,106,230 with operation cost of 1,343,659 $/year and the cost of energy equals to $/kwh as shown in Table 12. Table 13 shows the greenhouse gases for the hybrid system (Diesel generators, the wind turbine and PV system). Table 12. Best optimum solution for Masirah Island load demand by using diesel generators, wind turbine and PV system Table 13. Greenhouse gases for hybrid system (Diesel generators, wind turbine and PV system) Pollutant Emission (kg/yr) Carbone dioxide 4,397,692 Carbone monoxide 12,763 Unburned hydrocarbons 1,327 Particular matter 872 Sulfur dioxide 9,369 Nitrogen oxides 110,081 Total 4,532, Results and Discussion Using different options for the generator with different capacity, wind turbines with several capacities, PV panel with various sizes, varied quantities of batteries and variation sizes of converters. There are four different systems used to meet the load demand of Masirah Island. These systems were diesel generators only (the central power station in Masirah Island); hybrid power system contains diesel generators with PV array. Also, hybrid power system contains diesel generators with wind turbine system, and hybrid power system contains diesel generators 12

13 with PV array and wind turbine system. Table 14 shows the simulation results summary for the optimal alternative systems that were used. Table 14. The simulation results summary for the optimal alternative systems System Type Net present cost (NPC)($) Operation Cost ($/year) Cost Of Energy (COE)($/kWh) Diesel 102,872,600 8,639, PV/Diesel 95,492,448 6,194, Wind/Diesel 89,015,264 2,885, PV/Wind/Battery/Diesel 28,106,230 1,343, Table 14 shows that the minimum cost of generated energy when hybrid power system using generators with PV array, a wind turbine and battery system is equal to $/kwh. Also, the net present cost was the heights when the diesel generator only was used and the lowest when hybrid power system using generators with PV array and wind turbine system. When hybrid power system using generators with PV array system the net present cost is equal to 95,492,448 $. The operation cost is equal to 6,194,544$/year, and the cost of energy is equal to $/kwh. The comparison of this system with the system that employs diesel generators only, there is an improvement in the net present cost (NPC), the operation cost, and the cost of energy (COE). The employment of a hybrid power system using generators with wind turbine system, the net present cost is equal to 89,015,264$. The operation cost is equal to 2,885,259$/year, and the cost of energy is equal to 0.192$/kWh. The comparison of this system with the diesel generators system and the diesel generators and PV array system, this system has less net present cost (NPC). It has lower operation cost and the cost of energy (COE). PV/Wind/Battery/Diesel is the best solution with NPC, OC and COE are $, $/year and $/kwh, respectively. Table15.Greenhouse gases for the different type of hybrid systems Pollutant Emission Diesel (kg/yr) Emission PV/Diesel (kg/yr) Emission Wind/Diesel (kg/yr) Emission PV/Wind Battery/Diesel (kg/yr) Carbone dioxide 5,887,234 5,297,382 4,628,352 4,397,692 Carbone monoxide 16,247 12,746 13,836 12,763 Unburned 1,563 1,286 1,406 1,327 hydrocarbons Particular matter 1, Sulfur dioxide 11,058 10,341 9,984 9,369 Nitrogen oxides 138, , , ,081 Total 60,55,753 5,436,599 4,773,822 4,532,104 Table 15 illustrates the greenhouse gases for the different type of hybrid systems. The emission of CO, CO 2, unburned hydrocarbons, particular matter, sulfur dioxide and Nitrogen oxides by 13

14 using only diesel generators are the largest comparing with the other types of hybrid systems. The utilization of a wind turbine, PV array, and diesel generators system produces the lowest emissions compared with the other types of the hybrid systems. The emission of unburned hydrocarbons is the minimum by using the hybrid power system that has diesel generators and PV array system comparing with the other types systems. 6. Conclusions The additional load, 500 new residential buildings, to the Masirah Island load increased the electrical power demand. Based on the simulation analysis the additional load was estimated. The current peak of diesel power generation plant is 8.4 MW, and it realized that the peak of the additional electrical load is around 16 MW. There are many optimization analysis were done to come out with the optimal hybrid power system to met the load demand. The results analysis shows that one of the most important elements that must exist in any combination in the system is the battery bank. The present of the wind turbine reduced the cost of energy of the system by around 13.5% comparing with that found using the system that uses only diesel generators. The use of PV panel system reduced the net present cost by around 7% and the cost of energy by around 7.2%. The analysis of the optimum sizing using PV/Wind/Batter/Diesel hybrid system showed that the system has the lowest cost of energy (CEO) compared to the other hybrid systems for Masirah Island. Also, the emission of the greenhouse gasses was reduced by using a hybrid power system that consists of renewable energy source since it reduces the usage of diesel generators. In conclusion, the hybrid system of renewable energy leads to high improvement in the efficiency of the system, make the system s power more reliability and reduce the net present cost and the cost of energy. Also using the hybrid power system reduces the emission of greenhouse gasses. ACKNOWLEDGMENT The recent research leads to the former results has received Research Project Grant Funding from the Research Council of the Sultanate of Oman, Research Grant Agreement No. ORG/EI/13/011. The authors would like to acknowledge support from the Research Council of Oman. The acknowledgment also extended to the Directorate General of Civil Aviation and Meteorology, Department of Meteorology, and Rural Areas Electricity Company, Oman. References: [1] Hussein A. Kazem and Tamer Khatib, Photovoltaic Power System Prospective in Oman, Technical and Economical Study, 1st Edition, ISBN: , LAP LAMBERT Academic Publishing, Germany. [2] Hussein A Kazem, Tamer Khatib, K. Sopian and Wilfried Elmenreich, Performance and feasibility assessment of a 1.4kW roof top grid-connected photovoltaic power system under desertic weather conditions, Energy and Building, 2014, Vol. 82, pp [3] A. H. Al-Badi, M. H. Albadi, A. M. Al-Lawati and A. S. Malik, "Economic Perspective for PV Electricity in Oman", The International Journal of Energy, 2011, Vol. 36, No. 1, pp [4]A. H. Al-Badi, Hybrid (solar and wind) energy system for Al Hallaniyat Island electrification, Journal of Sustainable Energy, 2011,Vol. 30,No. 4, pp

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