Models for Integration of Renewable Energy Sources for Residential Low Power Applications PRATHAP THANIKONDA #1, SUBRAMANYA SARMA S *2

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1 Models for Integration of Renewable Energy Sources for Residential Low Power Applications PRATHAP THANIKONDA #1, SUBRAMANYA SARMA S *2 # 1 Assistant Professor, EEE Department, Ramachandra College of Engineering, Eluru, A.P., India. # 1Associate Professor, EEE Department, Ramachandra College of Engineering, Eluru, A.P., India. 1 prathapthanikonda@gmail.com 2 sssarma.eee@gmail.com Abstract Renewable energy sources (RES) have emerged as an alternative source of energy generation and an effective replacement for conventional fossil fuel based power generation systems. Immense development has been made in renewable energy fields and methods to harvest it. To replace conventional power generation system, these renewable energy resources must be reliable, sustainable, stable, and efficient. But these resources have their own individual distinguished characteristics. Due to intermittent nature of renewable energy resources, the uninterrupted power availability cannot be guaranteed especially for residential consumers. Handling and integration of such diversified renewable power sources is not a trivial process. It requires high degree of efficiency in power extraction, transformation, and utilization. These objectives can only be achieved with the use of highly efficient, efficient, reliable, secure and cost-effective power electronic interface. This research work presents various models for integration of renewable energy sources to meet the requirements of off-grid connected residential low power applications. Keywords Green technologies, Residential loads, Solar PV system, Wind Turbine Generation, Fuel Cell, Energy Storage. I. INTRODUCTION Energy is one of the important and essential inputs for industrialization and economic development. Fossil fuels are the major resources and play a vital role to supply global energy demand. However, fossil fuel reserves are limited, and usage of fossil fuel sources has negative environmental and economic impacts. Renewable energy resources can be defined as energy resources that are replaced periodically by natural processes and are practically inexhaustible so that their reserves are not depleted when used. Renewable energy is also called as clean energy or green energy because it does not pollute the environment in the manner that non-renewable energy resources do. All forms of renewable energies are derived directly or indirectly from sun s energy and hence, renewable energy can be termed as infinite energy [3]. A. Disadvantage of using Non-Renewable energy sources The Non-renewable sources of energy those are using today are limited and are bound to exhaust some day The speed at which such resources are being utilized can have serious environmental changes. Non-renewable sources release toxic gases in the air when burnt which are the major cause for global warming. Since these sources are going to exhaust soon, prices of these sources are soaring day by day. Thus there is a great need for electric power which has to be produced in a clean way that is through the Renewable energy sources like solar, wind, tidal, geothermal, biomass energy sources. These resources are very cheap and are abundant in nature. B. Advantages of Renewable Energy Sources The sun, wind, geothermal, ocean energy are available in the abundant quantity and free to use. Renewable sources have low carbon emissions, therefore they are considered as green and environment friendly. Renewable sources help in stimulating the economy and creating job opportunities. No need to rely on any other countries for the supply of renewable sources. Renewable sources can cost less than consuming the local electrical supply. So availing renewable sources can cut electricity bills. Various tax incentives in the form of tax waivers, credit deductions are available for individuals and businesses who wish to go green. 149

2 II.RENEWABLE ENERGY SOURCES Energy sources can be classified into Conventional and Renewable sources. The conventional sources like fossil fuel based generations have been widely deployed in distribution systems as cogeneration or backup generation without having significant interaction with distribution networks. On the flip side, the renewable energy sources such as wind turbine generation, solar PV generation and micro turbines and clean fuel based generations are also seen to be increasingly employed in distribution networks due to their environmental concerns and associated incentives. Table 1 Various types of energy sources and their advantages and disadvantages Type of source Type of technology Description Advantages: Fossil fuel based Readily available with continuous production generators Controllable and dispatchable Conventional ( Diesel / Coal / Gas / Relatively low capital investment sources Combined heat & Disadvantages: Power ) High operation and maintenance cost High emissions and noise pollution Renewable energy Sources Wind turbine (WT) based Generating units Solar (PV) based Generating units Clean Fuel based Generating units ( Biomass / Fuel Cells / Micro turbines ) A. Wind Turbine (WT) Power Generation Advantages: No emissions and No fuel cost Low operation and maintenance cost Possible to export reactive power to grid for network support Disadvantages: Intermittent and low capacity power generation Difficult to predict power generation and not suitable for all locations Advantages: No emissions ; No fuel cost ; No noise impact Capacity augmentation is easy Possible to export reactive power to grid for network support Disadvantages: Non firm power generation ; low efficiency ; requires large area High capital investment on PV modules and ancillary equipments Advantages: Readily available with continuous production ; less emissions Controllable and dispatchable Possible to export reactive power to grid for network support Disadvantages: High capital investment ; High fuel cost Risk associated with fuel availability Wind generation is rapidly gaining a share in electricity supply worldwide. Wind power is sometimes considered to be energy source for residential consumers, because the size and location of some wind farms make it suitable for connection at distribution voltages. Wind energy conversion systems (WECS) transform the energy present in the blowing wind to electrical energy. Wind is a highly variable resource that cannot be stored and wind energy conversion systems must be operated accordingly. Wind energy is transformed into mechanical energy by means of a wind turbine that has one or several blades (three is the most usual number). The turbine coupled to the generator by means of a mechanical drive train, usually includes a gearbox. 150

3 Figure 1 Fixed speed wind turbine generator equipped with soft starter and reactive power compensator Figure 2 Wind turbine generating system equipped with back to back AC/DC/AC convertors Figure 3 Wind turbine generating system equipped with wound rotor synchronous generator Figure 4 Wind turbine generating system using wound rotor induction generator with slip control circuit Figure 5 Doubly fed induction generator typical installation diagram as a wind generator Figure 6 Permanent magnet synchronous generator based wind turbine generating system 151

4 Figure 7 Schematic diagram of wind turbines start up controller B. Solar Photo Voltaic (PV) Power Generation The photovoltaic (PV) technology uses semiconductor cells (wafers), each of which is a large area p-n diode with the junction positioned close to the top surface. The PV effect results in the generation of direct voltage and current from the light falling on the cell. Multiple cells are assembled in modules to generate sufficient voltage and current. Most of the present PV technology utilizes crystalline semiconductor material similar to that used in integrated circuits. Hence, the cost of PV cells has been quite high. PV systems are more attractive for remote and isolated areas where utility power is not available and grid connection cost is higher. Figure 8 Schematic diagram of PV generating system supplying power to off-grid connected loads Figure 9 Schematic diagram of multiple PV module based generating system supplying power to utility grid C. Fuel Cell (FC) generating system A fuel cell (FC) is an electrochemical energy conversion system, where chemical energy is converted directly into electrical energy and heat. Resulting advantages of this technology are high efficiency (almost at partial load), low emission and noiselessness (due to non existence of moving parts). 152

5 Figure 10 Block diagram of integration of FC system with 1-ф grid Figure 10 Block diagram of FC system supplying power to 1-Φ AC loads III. INTEGRTAED ARCHITECTURES A. Architecture for integration of Renewable energy sources to supply power to islanded AC & DC loads using AC link Figure 11 Schematic of PV, Wind and other renewable sources integrated to supply power to AC and DC loads B. Architecture for integration of Renewable energy sources to supply power to islanded AC & DC loads using DC link Figure 12 Schematic of PV, Wind and other renewable sources integrated to supply power to AC and DC loads 153

6 Figure 13 Ring type architecture for integrating renewable sources to supply power to AC and DC loads C. Architecture for integration of Renewable energy sources to supply power to islanded AC & DC loads (AC & DC links) Figure 14 Schematic of PV, Wind and other renewable sources integrated to supply power to AC and DC loads Figure 15 Radial type architecture for integrating renewable sources to supply power to AC and DC loads Figure 16 Feeder type architecture for integrating renewable sources to supply power to AC and DC loads 154

7 Figure 17 Proposed architecture for integrating renewable sources to supply power to AC and DC loads Figure 18 Proposed architecture for integrating renewable sources to supply power to AC and DC loads Figure 19 Complementary architecture for integrating renewable sources to supply power to AC and DC loads IV. CONCLUSION This article has briefly discussed various models for integration of renewable energy sources to meet the requirements of low power application residential loads. The proposed architectures discussed in this article are suitable for satisfying the power requirements of off-grid connected low power residential consumers in rural areas. V. REFERENCES [1] Yavanoglu Kapalan, "Renewable Energy Research Applications," in IEEE international conference on digital object identifier, Nagasaki, 2012, pp [2] Ramakumar, "renewable energy sources and developing countries," IEEE transactions on power apparatus and systems, vol. 3, no. 2, pp , July [3] Tuo Lin, Yang Yu, and Sha "Global trends of new energy development in view of Expo 2010 Shanghai," in International Conference on Electrical and Control Engineering (ICECE), Yichang, 2011, pp

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