The Role of Renewable Resources: A Hybrid System of Wind and Solar Energy 1)

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1 The Role of Renewable Resources: A Hybrid System of Wind and Solar Energy 1) Abraham Lomi, Aryuanto Soetedjo, and Yusuf Nakhoda Department of Electrical Engineering Institut Teknologi Nasional, Malang, East Java, Indonesia abraham@itn.ac.id ABSTRACT Abstract This paper proposes a hybrid energy system combining solar photovoltaic and wind turbine as a small scale alternative source of electrical energy. By combining these two sources of renewable energy in the form of a hybrid system is expected to generate optimum energy to overcome the local energy needs. The combination of renewable energy technologies allows a more balanced electricity supply during day/night and seasonal changes. At most sites wind speed is low, when the sun is shining and reaches higher values on cloudy days. Thus the amount of energy generated by wind energy reaches its maximum in the winter months, while the output of PV-cells is significantly higher in the summer. Hybrid system are very often used for stand-alone applications at remote sites. A Simulink model of a designed system was tested under certain conditions and provided a significant results of overall system. The power output of the wind turbine generator depends on the wind speed profiles as well as the solar power depends on the solar intensity and weather conditions. A designed and constructed a hybrid system has been tested and the maximum power output approximately of about 280 Watt in the period of time at to 1500 hours. Keywords: renewable energy, solar energy, wind energy, hybrid system INTRODUCTION With the growing concern of global warming and the depletion of fossil fuel reserves, there needs to be a solution how to utilize renewable energy sources to create a green environment and convenient to preserve the earth for future generations. In addition to hydropower, wind and photovoltaic energy has great potential to meet the energy needs, especially in remote areas far from reach of PLN grid. The latest developments and trends in electrical power consumption indicates the increase of using renewable energy. Solar energy and wind energy are two sources of renewable energy that is most commonly used. Wind energy has become the most expensive technology so many scientists who are interested in doing research. Solar cells convert energy from sunlight into DC electricity. PV offers many advantages over other renewable energy in the absence of noise and minimal maintenance. Presented on Seminar Nasional Teknologi 2015 (SENATEK 2015), Institut Teknologi Nasional Malang. Indonesia has the potential of wind power is large enough that could be any time at different speeds to produce renewable energy. Similarly, solar energy is present throughout the day but the level of solar radiation varies as solar intensity uncertain because it depends on the weather cloudy or not. By combining these two sources of energy sources in the form of hybrid system is expected to generate enough energy to overcome the local energy needs. Indonesia has a thriving economy at the intersection of the Pacific and Indian oceans, between Asia and Australia. It is home to 240 million people and is the world s fourth-largest country in terms of population. Its territory covers approximately 17,500 islands. Eighty percent of the population lives on the islands of Java and Bali; the rest is scattered widely among the country s 6,000 other inhabited islands. Indonesia s economy grew 4.3 percent in 2009, in line with the country s 3 6 SENATEK 2015 Malang, 17 Januari

2 percent growth rate since the Asian financial crisis of the late 1990s [1]. Future growth is likely to accelerate as the world recovers from the global recession of Although Indonesia lacks strong policy incentives for renewable energy, it provides companies with a stable political system and a growing economy in which to do business. Projects range from large-scale power plants with power purchase agreements (PPAs) negotiated with PLN, the state-owned utility company, to development projects coordinated by multilateral development banks or local governments. The Government s political decision to retain the oil price subsidy has hampered other energy programs and remains a major barrier for energy diversification and conservation. Geothermal 1,50% Hydro 3,29% Coal 26,38% OIL 46,93% Gas 21,90% Fig. 1. Current Energy Condition. Lack of enforcement in environmental regulation is observed in the implementation of PLN s 10,000 MW fast-track program. In 2008, fossil fuels provided 93 percent of the economy s total energy capacity (29.5 GW). But unlike previous years when excess energy was exported to neighboring markets, aging wells and limited investment forced Indonesia to import oil and to eventually remove itself from the Organization of the Petroleum Exporting Countries (OPEC). INDONESIA RENEWABLE ENERGY POLICY A Strategy on Renewable Energy will be developed, which will translate the goals, objectives and deliverables set out herein into a practical implementation plan. Underpinning the Renewable Energy Strategy is a Macro-economic analysis to guide cost efficient Government financial assistance based on a least-cost and employment maximizing supply model in reaching the target. A number of important investigations will be undertaken during the strategy development, how the renewable energy target will be periodically reviewed with respect to the different primary energy carriers, the mechanism that is selected for the feed-in of electricity generated from renewable resources into the national electricity grid, and the modalities of the various financial, legal and regulatory instruments to be employed as part of the enabling framework of mechanisms to support the promotion of renewable energy. The main aim of the policy is to create the conditions for the development and commercial implementation of renewable technologies. Government will use a phased, managed and partnership approach to renewable energy projects that are well conceived and show the potential to provide acceptable social, environmental and financial returns for all investors and stakeholders. Renewable energy will contribute to the diversification of energy resources through the implementation of a properly managed programme of action that will provide sufficient incentive for the sustainable development of the renewable energy-based industries. Today, renewable energy accounts for a small but growing portion of Indonesia s electricity portfolio. Most renewable energy comes from the hydropower and geothermal industries, but growth in other sectors is likely. Presidential Decree No. 5 mandates an increase in renewable energy production from 7 percent to 15 percent of generating capacity by SENATEK 2015 Malang, 17 Januari

3 Fig. 2. Current Energy Mix vs. Future Energy Goals. To accomplish that goal, 6.7 GW of new renewable energy capacity must be installed in the next 15 years based on current growth projections [2]. To encourage development and utilization of renewable energy and to improve efficiency of energy utilization, a Policy on Renewable Energy and Energy Conservation also called the Green Energy Policy was promulgated by the Ministry of Energy and Natural Resources on December 23, This policy provides the reference for renewable energy development and energy conservation in Indonesia to support sustainable development. Under the Green Energy Policy, renewable energy in Indonesia has been classified into three types: (a) already developed commercially (biomass, geothermal, and hydro energy); (b) already developed but still limited (solar, wind); and (c) still at the research stage (ocean energy). The Green Energy Policy defines action steps consisting of formulation of more specific policies and programs. These include policies for: (a) investment and funding; (b) incentives; (c) energy pricing; (d) human resources; (e) information dissemination; (f) standardization and certification; (g) research and development; and (i) institutional development. Following the Green Energy Policy, the Blueprint on Energy published by ESDM set forth a roadmap for development of different energy resources, described strategies for incentives such as a carbon tax, and provided an overview of available and potential resources and target energy mix. This document was the basis for Presidential Regulation on National Energy Policy in 2006 as shown in Table-I. TABLE I: TYPE OF ENERGY Type of Energy Unit Year Geothermal MW 3,442 4,600 6,000 9,500 Wind MW PV MW Micro-Hydro MW INDONESIA RENEWABLE ENERGY POTENTIAL Indonesia is a country rich of natural resources with a primary energy source that can be managed and used to meet national energy needs, especially the needs of electrical energy to remote communities. But reliance on energy derived from fossil thinned provides opportunities to develop environmentally friendly energy sources, i.e., sources of energy derived from new and renewable energy sources. SENATEK 2015 Malang, 17 Januari

4 Based on ESDM data (2013), Indonesian geothermal reserves amounted to 16,502 MW and geothermal potential of about 29 MW. Installed capacity of geothermal power plant (until May 2013) is 1,341 MW. Electricity potency from large scale hydro power amounted at 75 GW, while the potential of mini/micro hydro was about MW. Meanwhile, the potential of electricity from biomass amounted to 13,662 MWe and the installed capacity of on grid power plant is 75.5 MWe. Hydropower energy resource is grouped into large scale (can be developed for power plants above 10 MW per location) and small-scale/ micro (potential electricity generation less than 10 MW). The potential for large-scale hydropower and small-scale/micro estimated respectively at about 75 GW and 450 MW. The potential is fairly spread in various parts of Indonesia. The use of hydropower resource is still relatively low at 4.2 GW of large-scale and small-scale of about 84 MW. Utilization of hydropower resources should be developed primarily with small-scale power spread schemes to meet local electricity needs. Constraints that may limit the increase of using water as energy power for the future is the fact that the location of resources does not coincide with the demand for electricity. Indonesia has a potential for biomass power of about 49,810 MW is currently undeveloped, but only 443 MW have been commercially developed. By 2025, Indonesia has targeted to install about 810 MW of biomass power, an increase of 80 percent, but that amount is still far less than the potential contribution [3]. Large-scale biomass projects would likely require new infrastructure to gather and deliver what is now considered a waste item. As a tropical country, the potential of solar power in Indonesia is quite high with an intensity of 4.8 kwh/m2/day and current installed capacity of solar power plant is MW (in 2013). Indonesia offers significant solar power resources (4.8 kilowatt-hours per square meter per day [kwh/m2/day]), but the country has yet to develop a strong market. To date, Indonesia has installed 12.1 MW of solar power, which is mostly from roof-mounted solar photovoltaic (PV) cells in urban areas [3]. Today, the use of solar energy in Indonesia is still very low at about 8 MW in the form of Solar Home System for the supply of electricity in rural areas. The low utilization of solar energy potential due to the cost of equipment (solar panels) is still expensive. With the growing market demand for solar panels in the world, estimated future prices of solar panels will tend to fall. Therefore, solar energy utilization in Indonesia should be developed including the possible use of the integrated scheme with grid. The total installed capacity of solar energy from 2005 to 2009 of MWp and in 2009 is increased of 4.83 MWp (or 35.8%) as shown in Table-II TABLE II: INSTALLED CAPACITY OF SOLAR ENERGY [6] Indonesia s potential for wind energy is limited because of the lack of wind along the equator. The country s windiest regions tend to be the less populated, eastern islands, which lack a transmission infrastructure capable of sustaining large wind farms. Wind power opportunities are thus limited to small or medium-sized projects requiring lower wind speeds. Based on the wind speed in many areas, wind energy resource in Indonesia ranges between m/sec at an altitude of 24 meters above the ground, such as NTB, NTT, Yogyakarta, Central Java, North Sulawesi and Southeast Sulawesi. The speed of wind energy resources in Indonesia is categorized SENATEK 2015 Malang, 17 Januari

5 of low-grade wind speed to medium. Overall, the wind energy potential is estimated at about 9,290 MW Indonesia, but only a few small-scale wind farms have been attempted and they account for only 9.59 MW of installed capacity [3]. Based on EBTKE (2011) the development of installed renewable capacity wind energy of 9, kw, an increase of kilowatts (or 4.71%) on the previous year. Over the previous 5 years, the total installed renewable capacity of wind energy has increased by 9, kilowatts as shown in Table-III. TABLE III: INSTALLED CAPACITY OF WIND ENERGY [6] HYBRID SYSTEM ARCHITECTURE The hybrid system of energy generation is a system that combines multiple sources of energy to supply electrical energy to the load center. The main goal is to optimize the energy output of each source with low cost, free of pollution, good power quality, and sustainable energy supply. Due to different characteristic of each plant, it creates advantage and disadvantage of operational system as described in Fig. 3 [4]. In Fig. 3(a), all the plants (wind, solar, diesel) and the battery are connected to the main bus before they distribute to the load bus. This architecture is referred to as main grid architecture, because the power generated by all plants is connected to the load through a single point. Because PV and battery output is a DC voltage, it is necessary to convert to AC voltage. Figure 3(b), shows all the plants are decentralized connected where each plant directly supply the energy to the load without centralized. This system architecture is difficult to control the system if the diesel engine is in off condition. In figure 3(c), the generating system is connected to a load through a central DC bus. With this architecture, the AC voltage generated by wind energy and diesel generator have to be converted into a DC voltage. Furthermore, the inverter is used to convert the DC voltage into AC voltage at the load. The advantage of this system is not required a control of frequency and voltage on the bus and allows the use of variable speed generator in the system. In other hand, the disadvantage of this system is that there are two stage processes in conversion the voltage. This is of course inefficiency the system SENATEK 2015 Malang, 17 Januari

6 PV PV WEC PV Diesel Battery WEC Battery (a) Diesel (b) PV WEC Diesel Battery (c) Fig. 3. The architecture of hybrid system generation. In this paper, the hybrid system architecture was adopted from the Fig. 3(c) with some modifications [5]. The control system is focused on how the process of charging and discharging of the battery system. SYSTEM DESIGN The system design consists of few modules such as inverter modules which is converted the DC voltage to AC voltage, measurement system for current, voltage, and power. The panel box where measurement devices are mounted is to perform the current and voltage profile of the system in any certain condition during the operation. The selected modules of the system designed are shown in Fig RESULTS AND DISCUSSIONS The results of the hybrid system model design was constructed based on a Simulink simulation and measurement was proposed. The data input of wind speed profile and intensity of the sun were recorded during 7 hours and provide a significant results. The generated power of wind turbines depends on the wind speed changes. The greater the wind speed, the greater the generated power. In this model, with the average speed of wind of about 8 m/sec, the out power of the turbine generator is about 285 Watt. Fig. 4. A test system module is connected to the computer. SENATEK 2015 Malang, 17 Januari

7 Fig. 5. The converter system. Fig. 6. Panel system of measurement devices. RESULTS AND DISCUSSIONS The results of the hybrid system model design was constructed based on a Simulink simulation and measurement was proposed. The data input of wind speed profile and intensity of the sun were recorded during 7 hours and provide a significant results. The generated power of wind turbines depends on the wind speed changes. The greater the wind speed, the greater the generated power. In this model, with the average speed of wind of about 8 m/sec, the out power of the turbine generator is about 285 Watt. The renewable energy hybrid system model was constructed in the top roof of 4 th floor building of the Department of Electrical Engineering, as shown in Fig.7. Fig. 7. A model of hybrid system of renewable energy source. SENATEK 2015 Malang, 17 Januari

8 Solar generated power plant in accordance with the magnitude of the received solar intensity solar panels as shown in Fig.7. The radiation intensity of 0.8 Suns (Watt/m2) generate power of about 165 Watt. The charge/discharge power is limited by the power load, so that the excess power is used to charge the battery as indicated by the increase in battery energy and negative battery current value (charging). Between the hours of 5:00 to 06:00 greater power than the power load generator, and the battery will release its load to the load (discharge) as shown by decrease in current battery and battery positive. CONCLUSIONS Indonesia is blessed with substantial renewable resources which are distributed throughout the country. Renewable energy (RE) resources have been largely unexploited because of the high up-front costs, lack of infrastructure to produce and deliver electricity to load centers. Decentralized renewable energy systems remain the most cost-effective options in many rural areas and should attract private investment as the government continues to address the regulatory framework for selling power to PLN. Small-scale renewable energy resources, such hybrid system can help meet the rural electrification on government goals and can be implemented without access to the nation s inefficient electricity grid. Small renewable energy projects can also create jobs for rural Indonesians, who often turn to deforestation as a means of survival. ACKNOWLEDGMENT This work is supported by the research grant from Directorate General of Higher Education, Ministry of National Education and Culture, Republic of Indonesia based on Grant No. 042/SP2H/P/K7/KM/2014. References [1] Estimate from the International Monetary Fund, World Economic Outlook, October [2] National Energy Blueprint (implemented in 2006). [3] Indonesia Energy Outlook, [4] E. Ortjohann, O. Omari, R. Saiju, N. Hamsic, D. Morton, (2003). A simulation model for expandable hybrid power systems, Proceedings of 2 nd European PV-Hybrid and Mini Grid Conference, Kassel, Germany. [5] Aryuanto Soetedjo, Abraham Lomi, Yusuf I. Nakhoda and Awan U. Krismanto, Modeling of Maximum Power Point Tracking Controller for Solar Power System, Jurnal TELKOMNIKA, Vol.10, No.3, September 2012, accredited by DGHE (DIKTI). [6] Statistik EBTKE, Ditjen Energi Baru Terbarukan dan Konservasi Energi, SENATEK 2015 Malang, 17 Januari