Optimized Design of a Hybrid PV-Wind-Diesel Energy System for Sustainable Development at Coastal Areas in Bangladesh

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1 Optimized Design of a Hybrid PV-Wind-Diesel Energy System for Sustainable Development at Coastal Areas in Bangladesh Sumon Rashid, a S. Rana, b S.K.A. Shezan, c Sayuti A.B. Karim, c and Shamim Anower d a Department of Electrical and Electronic Engineering, Pabna University of Science and Technology, Pabna, 6600, Bangladesh b Department of Electrical Engineering, University of Malaya, Malaya 50603, Kuala Lumpur c Department of Mechanical Engineering, University of Malaya, Malaya 50603, Kuala Lumpur; shezan.ict@gmail.com (for correspondence) d Department of Electrical and Electronic Engineering, Rajshahi University of Engineering and Technology, Rahshahi 6204, Bangladesh Published online 00 Month 2016 in Wiley Online Library (wileyonlinelibrary.com). DOI /ep Power generation capacity of Bangladesh needs to be enhanced to support the rising electricity demand. Bangladesh has predominantly used fossil fuel generators for the past decades. Saint Martin s Island and Kuakata are two significant areas that lie at or near the coast of Bangladesh with an average annual solar radiation of 4.81 and 4.65 kwh m 22 day 21, respectively. The monthly average wind speeds at a height of 25 meters are 4.79 and 4.54 m s 21, respectively. Considering this data and the benefits of the optimized hybrid systems, HOMER (Hybrid Optimization Model for Electric Renewable) is used to optimize a system for each of these areas. The costs of energy found from the proposed optimized PV-wind-diesel hybrid Energy system for Saint Martin s island and Kuakata are and USD kw 21 h 21, respectively, the net present cost (NPC) also has been evaluated as USD which are quite reasonable with respect to the present situation in Bangladesh. The major objective of this proposed optimized design is to supply the maximum load demand using renewable sources with the minimum cost of energy (COE) and reduce the burning of fuel and also reduce the emission of CO 2. The proposed energy system is able to meet 67.3 and 62.3% load demand using renewable sources, which helps to reduce the GHG (Green Houses Gas) emission by 67 and 64% for Saint Martin s island and Kuakata, respectively when compared to a diesel system. Total load served throughout the year is 33,611 kwh, which is 16% higher than the previously designed system with approximately equivalent COE. VC 2016 American Institute of Chemical Engineers Environ Prog, 00: , 2016 Keywords: hybrid system, PV-wind-diesel, renewable and sustainable energy, optimization, feasibility INTRODUCTION In recent years, due to rapid technological development, declining cost of equipment needed for renewable energy systems, government economic incentives, and pollution free VC 2016 American Institute of Chemical Engineers characteristic of resources, significant worldwide attention has been directed toward power production from the renewable sources, such as PV, wind, biomass, geothermal, ocean wave, tides, etc. Many countries have set up or demonstrated large, small and micro power generation systems using exploitable renewable resources [1,2]. In Bangladesh, to establish the use of alternative and sustainable energy sources, several NGOs and government organizations are working continuously to develop the solar and wind power sector. In 2004, a survey carried out by the Local Government Engineering Department (LGED) under the Sustainable Rural Energy (SRE) program recorded that, Saint Martin s island (situated just south off the coast of Cox s Bazar) houses 778 families with an annual energy demand of 359 MWh. To meet this demand, the Bangladesh Power Development Board (BPDB) installed a 30 kw diesel generator, which is currently out of service [3]. Therefore, it is evident that a more suitable solution is needed to fulfill the demands of these areas. The annual average solar radiation is similar throughout the coastal region of Bangladesh. Average annual global solar radiations at Saint Martin and Kuakata are 4.81 and 4.65 kwh m 22 day 21, respectively, and monthly average wind speed at 25-m height are 4.79 and 4.54 m s 21, respectively. Given that, the solar radiation and wind speed data is consistent, it should be enough to produce electricity to meet the energy demand in coastal areas by setting up off-grid hybrid systems. Integration of multiple renewable energy sources with equipment presently available may possibly help to improve the load factors, debilitate individual fluctuation and provide higher reliability and operational flexibility while lowering production, maintenance and replacement costs. It also reduces the pollutant emission to the atmosphere. For most of the cases, this combination behaves, like a full complement system between various energy sources. This is known as a hybrid system [4]. Because the hybrid system contains various costly components needed for renewable energy systems, perfectly optimized system designs are needed to lower net present cost (NPC) and the cost of energy (COE). Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep Month

2 Figure 1. Complementary nature of wind and solar energy source at Saint Martin s Island and Kuakata. [Color figure can be viewed at wileyonlinelibrary.com] Several hybrid system optimization techniques and simulation programs have been developed so far. Because of the incorporation of non-linear components with many optimization parameters and failure of classical methods, genetic algorithms based design and operation control techniques are used for solving complex problems [5]. Computer aided simulating programs, such as HYBRID-2 developed by the National Renewable Energy Laboratory (NREL) from USA and TRNSYS by the University of Wisconsin from USA were developed to simulate the hybrid system [6]. Though HYBRID-2 is unable to optimize the system, a very accurate simulation of a hybrid model is possible with this tool. Initially, TRNSYS was developed for thermal system simulation and later, PV system was included with TRNSYS to simulate the hybrid system. However, this tool is also unable to optimize the system [7].The operation and control of PV-diesel, hybrid system is achieved through an artificial neural network. For optimization purposes, a dispatch strategy has been applied by setting a starting and stopping point of the diesel generator [8]. To optimize a solar-wind hybrid system, iterative and probabilistic calculation techniques considering the loss of power supply probability (LPSP) were proposed. Using these techniques, the optimized system with minimized system cost was designed [9]. Worldwide several studies have been done on hybrid system optimization techniques and developed simulation programs for power supply in off-grid area [10]. The major drawback associated with wind and solar is their unreliable nature, site dependence, dependence on weather and climatic changes, which make the optimization process more complex and demands better optimization technique [11]. Yang et al. proposed iterative and probabilistic calculation techniques considering the loss of power supply probability (LPSP) to optimize a solar-wind hybrid system [12]. In another research study carried by Kellog et al. for unit sizing and cost analysis of an off-grid wind-solar-pv hybrid system proposed simple numerical algorithms [13]. For Hybrid System power pinch analysis a new tool outsourced and storage electricity curves (OSEC) introduced by Al-Alawi A et al. which able to perform correct load shifting. For optimization purposes, Ashari et al. has been applied a dispatch strategy by setting a starting and stopping point of the diesel generator [14]. Al-Alawi A et al. applied artificial neural network for operation and control of PV-diesel, hybrid system [15]. HOMER (hybrid optimization model for electric renewable) simulation program was developed by NREL, USA to optimize the micro-power hybrid system using a kinetic battery model [16]. This model is widely used as a hybrid system optimization program and continuously updated with the new features. Technically, HOMER always finds the most energy efficient combination of hybrid system based on the energy source models, load profile, data of solar radiation, wind speed, fuel price, and component details. It also performs sensitivity analysis to visualize the impact on COE by varying parameters (wind speed, solar radiation, fuel price, maximum annual capacity shortage, and hub height) [17]. In 2012, for Saint Martin Island, an optimized design has been carried out using HOMER, while this author s efforts were concentrated to reduce the COE. They were able to extract only 31% load demand (31% renewable fraction) using 2 Month 2016 Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep

3 Figure 2. Schematic block diagram of a hybrid solar PV-wind-diesel energy system. [Color figure can be viewed at wileyonlinelibrary.com] renewable energy and the rest of the energy demands weremetbydiesel[18].asthefuelpricewaslow(0.715 USD L 21 ),theproposedmodelwasfeasibleforthattime. Considering a significant increase in the price of diesel and the demand of a more environmentally friendly system, the model become obsolete at present and the need for an alternate optimized system has become obvious [18]. The main objective of the present work is to design a sustainable optimized hybrid system design by focusing the maximum power production using renewable sources with minimum COE. Using HOMER micro-power optimization model, we have been able to optimize a hybrid system for a specific load demand that minimizes the COE and net present cost, increases renewable fraction and reduces emission of gases to a great extent by reducing the excess energy generation for Saint Martin s island and Kuakata. Here, an individual optimized design of a hybrid system is proposed for Saint Martin and Kuakata; which are the most resourceful remote coastal areas of Bangladesh. This design canbeappliedtoothercoastlineareasandalso,someother remote areas of Bangladesh. As a first step, to find out the most suitable sources and plan a hybrid system accordingly, renewable energy sources are analyzing at individual locations. Then a hybrid system is designed and components optimization of the designed system with energy balance calculation is carried out using HOMER micro-power optimization model to minimize the COE [19]. To estimate the system cost and production cost of energy, cost calculations studies are done. This includes costs, such as capital, operation, maintenance, replacement, fuel and interest. This economic analysis is carried out to determine the feasibility of the proposed system. Finally, a comparative study is shown with other hybrid energy systems for confirming the practicability of the proposed optimized system [20,21]. SELECTION OF ENERGY SOURCE Figure 1 shows the relation between the solar radiation and the wind speed over the course of a year. It also shows a complementary relationship between the wind and solar systems illustrating a negative correlation between the two resources in Saint Martin and Kuakata. So, for implementation of a renewable energy system at Saint Martin s island and Kuakata, a combined wind and photovoltaic system along with diesel system would be the most feasible option [22]. From the figure it can be observed that the changes between the solar and wind energy resources and fluctuation of the two curves it indicates the variation and operational differences of the solar irradiation and average wind speeds [23]. OPTIMIZED DESIGN OF A HYBRID MODEL Before starting the computer aided simulation, mathematical models of each component of hybrid systems are studied throughly (based on Figure 3 [24]). Figure 2 shows the schematic visual diagram of a complete solar wind hybrid energy system. The hybrid energy system consist of Wind turbine, Solar (PV) module, Load demand, diesel generator as power back-up, Battery back-up and converter to convert the power dc to ac. The load demand depends on the specific locality, community and number of people living in that particular area. When the solar panel is unable to fulfill the demand of the power for the specific area, the wind energy and diesel generator can support to fulfill the expected load demand. Figure 3 shows the proposed structure of hybrid system for Saint Martin s Island and Kuakata. In the structure, we have included diesel generators with renewable power generators (wind and solar). During design the system, we concentrate to maximize the output power from the renewable sources for minimizing per unit COE. For operating feasibility, quick start, small size, good thermal efficiency and good load support diesel generator have been chosen. Diesel generator, battery bank, and converter (inverter and rectifier) are added as part of back-up and storage systems during adverse weather conditions. This proposed system structure used in HOMER to optimize it for specific system requirements. Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep Month

4 Figure 3. Solar PV-wind-diesel hybrid system. Figure 4. Proposed hybrid system in HOMER. [Color figure can be viewed at wileyonlinelibrary.com] RESULTS AND DISCUSSION Optimized Results and Analysis Using HOMER simulation tool, performance analysis of the proposed hybrid system is carried out. HOMER configured hybrid system is shown in Figure 4. HOMER represents the optimized results categorically and detailed results are shown using sensitivity parameters, like wind speed, solar radiation, fuel cost, maximum annual capacity shortage, and renewable fraction. To design the optimized hybrid system, HOMER performs thousands of simulations using sensitivity parameters. Simulations are conducted considering different values for wind speed, solar radiation, diesel price and minimum renewable fraction; providing experimental flexibility. Figure 5 shows the general process of the simulation process of a complete hybrid solar wind energy system. This diagram shows the sequential and active mechanism of solar wind hybrid energy system in HOMER platform. Figure 5. The complete flow chart of the hybrid energy system. [Color figure can be viewed at wileyonlinelibrary. com] The most feasible optimized system found by HOMER for specific load demand includes solar irradiation 4.81 kwh m 22 day 21, wind speed 4.79 m s 21, fuel price USD L 21 and hub height 30 m, as pictorially shown in Figure 6. From Figure 6, it can be observed that after performing a lengthy optimization process, HOMER arranged the most feasible optimized system at the top of the window and showed 4 Month 2016 Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep

5 Figure 6. Simulated results of PV wind diesel system for wind speed 4.79 m s 21, solar irradiation 4.81 kwh m 22 day 21, fuel price USD L 21, and maximum annual capacity shortage of 0% (In figure all the currency values were in terms of BDT). [Color figure can be viewed at wileyonlinelibrary.com] the contribution of renewable sources (renewable fraction) to the total power production. Optimized system components size for both proposed locations are listed in Table 1. At a cost of USD kwh 21 and an initial cost of USD kwh 21, the optimized hybrid wind-pvdiesel system designed for Saint Martin s island provides a much more feasible approach to meeting the energy demand there. Figure 7 shows the monthly average electric power production from the HOMER optimized hybrid system. From Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep Month

6 Figure 7. Power generated from the optimized hybrid PV wind diesel system across a year. [Color figure can be viewed at wileyonlinelibrary.com] Table 1. Optimized system architecture of solar-wind-diesel hybrid system. System component Saint martin s island (size) Kuakata (size) PV array 6 kw 6 kw Wind turbine 6 Generic 3kW 5 Generic 3kW Diesel generator 12 kw 12 kw Battery 50 Hoppecke 8 OPzS 800 Converter 10 kw 10 kw 50 Hoppecke 8 OPzS 800 Figure 7, it can be seen that the power produced by a diesel generator is almost same, while the power produced from wind and photovoltaic show their full complementary behavior across the year. Economical Feasibility Analysis HOMER analyses the system according to the minimization of COE and maximizing the power output of the system. Other factors, which influence the analysis are capital cost, operating cost, renewable energy factor, total NPC (net present cost) and diesel consumption rate. Table 2 shows the capital cost, replacement cost, operation and maintenance cost, and fuel cost of different system components. Environmental Effects The proposed solar wind diesel hybrid system reduces gas emission by a significant amount due to the reduced fuel consumption. This reduction in gas emission is determined using HOMER software. The emission of this optimized system has been decreased by 67 and 64% from the existing diesel based energy system for Saint Martin s island and Kuakata, respectively. Emissions from various pollutants of this optimized system are shown in Table 3. DESIGN ENHANCEMENT ANALYSIS Comparative Study Table 4 shows a comparison study of the proposed hybrid system with other energy systems for Saint Martin s Island. The simulation results and comparative results clearly reveal that solar-wind-diesel hybrid system is the most feasible and cost effective off-grid power system at the present situation of Bangladesh. Improvement Summary of Proposed Optimized System HOMER simulates the system configuration numerous times using given parameters to obtain the optimization results and ranks the most optimized system based on the COE and NPC. In the simulation, parameters are set up in such a manner that HOMER can find an optimized system that can deliver the maximum power using renewable sources while burning less fuel. The optimized system proposed in our work is able to serve 67.3% (renewable fraction) load demand, which is more than double compared to the previously optimized system. As maximum load demand is met up from renewable sources, the fuel burn reduces and it helps to reduce GHG emissions 67%.This reduction is higher compared to the previous optimized system (39%). 6 Month 2016 Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep

7 Table 2. Net present cost of the optimum solar-wind-diesel hybrid system (Saint Martin). Capital Replacement O & M Fuel Salvage Total Component USD USD USD USD USD USD PV Wind turbine 3kW Diesel Generator Hoppecke 8 OPzS Converter System cost Total , Table 3. Emission of various gasses from the optimized system. Pollutant Saint Martin (emission kg yr 21 ) Kuakata (emission kg yr 21 ) Carbon dioxide 15,613 17,063 Carbon monoxide Unburned hydrocarbons Particulate matter Sulfur dioxide Nitrogen oxides % reduction Table 4. Cost comparisons with other energy systems. Energy system Net present cost (USD) Fuel cost (USD) Cost of energy (USD/kWhr) Solar-wind-diesel Solar-diesel Diesel Table 5. Proposed optimized system compared to the previously optimized system. Criterion Proposed optimized system Previously optimized system [19] PV array 6 kw 8 kw Wind turbine 18 kw 3 kw Diesel generator 12 kw 15 kw Fuel price USD L 21 (present) USD L 21 (2012) Renewable fraction 67.3% 31% % GHGs reduction 67% 39% Cost of energy USD kwh USD kwh 21 (COE) Accolade served 33,611 kwh yr 21 28,394 kwh yr 21 The proposed optimized system is able to serve about 33,611 kwh yr 21 AC load, which is 16% higher compared to the previous optimized system with approximately equivalent COE, though the current diesel price is about USD L 21, which is 21% higher than the previous price (previous price was USD L 21 ). This improvement in designing an optimized system will certainly help to attract the investors to set up the commercial plants. For various important criterion the detail comparison of system improvement are shown in Table 5. CONCLUSION Pollution, emissions of greenhouse gases, and the rise of energy demands are increasing the dependence on importing energy from neighboring countries. Among the numerous renewable resources, solar and wind energy represent the most feasible option for the application of a power generation system for sustainable development. In the coastal areas where grid connection is not available or grid extension is not feasible, renewable sources, like wind and solar PV-based hybrid systems can be potential solutions. The existing single source renewable energy systems for the coastal regions of Bangladesh cannot supply the entire load and is also financially not viable. In these areas, a solar wind diesel hybrid energy system can be a cost effective solution since the renewable energy sources are abundant. It will also reduce the pressure on the national grid. Moreover, the proposed hybrid system reduces the emission of gases and helps to trim down the environmental pollution. During summer, when solar radiation is abundant with little wind energy, the solar arrays can supply most of the required energy. In winter season, when wind velocities are higher with less solar radiation, the wind turbines will supply most of the required energy. This clearly indicates a complementary relationship between the two sources in this case. Also, this optimized system can give better performances than the other systems because the generator can minimize the problem if any fault occurs in PV panel or in wind turbines. The hybrid model proposed in the present work will be able to meet the load demand with a reasonable COE of and USD kwh 21 for saint martin and Kuakata respectively. The renewable fraction of the present model is almost double compared to the previous model, which considerably reduces environmental pollution. The most significant findings from this analysis are the reduction of CO 2 emissions in comparison with the other conventional power plants. ACKNOWLEDGMENTS This work was supported by the University of Malaya Research Grant (UMRG). The project no is RP039A-15AET. NOMENCLATURE PV COE NPC SRE BPDB LGED LPSP HOMER NREL photovoltaic cost of energy net present cost sustainable rural energy Bangladesh power development board local government engineering department loss of power supply probability hybrid optimization model for electric renewable national renewable energy laboratory LITERATURE CITED 1. Li, X., Hui, D., & Lai, X. (2013). Battery energy storage station (BESS)-based smoothing control of photovoltaic (PV) and wind power generation fluctuations, Sustainable Energy, IEEE Transactions on, 4, Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI /ep Month

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