Power Systems - Electrical and Electronic Engineering - Term Paper Example

Name Course Date Title: A combined Solar Hydro based energy scheme Table of Contents Table of Contents 2 Chapter 1: Literature Review 3 Generation of renewable energy in UK 6 Chapter 2: Energy Evaluation 8 The basic energy needs of the settlement 8 Power loads in rural area 8 Connected load 9 Chapter 3: Solar Scheme 9 a)Pico PV systems 9 b)Classical home systems 10 c)Solar residential system 11 Chapter 4: Hydro Scheme 11 Installation 12 Chapter 5: Scheme Interconnection 12 Summary 13 References 15 Chapter 1: Literature Review UK has enormous potential to produce renewable energy as it has the world’s largest source of tidal, wind and wave energy (Abramsky, 2010). Wind turbines in the countryside, for example, can generate more than 20% of the national electricity. In addition, UK has a significant amount of solar energy potentials by installing passive solar houses. Stand alone units have already been put in place in most parts of the country. For example, generation of renewable electricity in UK has increased in the past 10 years by more than 24% to 24.6 GW. The sources of increase include offshore and onshore wind, biomass, and photovoltaic (Gov.UK, 2014). However, the operation of these isolated power units may not be valuable in terms of reliability, cost and efficiency. A more viable solution is to combine different renewable sources of energy into hybrid energy systems. This research is mainly on power supply systems for small areas in UK. Remote places that are not electrified through grid, may be due to capacity shortage, can receive electricity through non-conventional energy sources such as wind, solar or micro-hydro systems. This paper explores the use of different energy sources such as biomass, solar PV panels and small hydro plants to produce power required in the remote settlement in mid UK (Gov.UK, 2014). A hybrid energy system combines different energy sources to generate power. The sources can be operated together and includes a storage unit. The system may also be connected to an AC power distribution network grid. Inverter device is used to convert a DC output from PV power output to AC before being connected to an AC grid. The converter controls the generation of power and storage systems. A combined power sources system offer advantage of a balanced and stable power derived from different power sources that complement each other. The goal is to maintain constant power supply in a remote place. This system is free from pollution, less costly and is user friendly. It can be used to provide electrical power to clinics, shops, homes and schools in areas where electrical grid has not been connected (Johansson, 2012). To ensure that the hybrid system can produce electricity reliably at a low cost, it must be design to produce optimum energy in terms of component selection and operation. Many studies have been done aimed at exploring the simple techniques for producing a combined energy systems. Borrowsy and Salameh (1994) studied the use of algorithm based on energy concept to produce optimum size for solar photovoltaic array in an energy hybrid system that uses solar photovoltaic (PV) and wind. Ali, Razak and Sopia (2007) studied on ways used to optimize hybrid energy systems by minimizing the cost of production and maintenance, and reducing excess energy (Sopia et al., 2007). Yuanrui and Jie (2008) focused their study on grid connected solar/wind hybrid power systems. The system had four subsystems that include solar photovoltaic (PV), wind turbine batteries and loads with each having AC and DC operation modes. The system employed agent based cooperate control strategy to obtain optimum power, energy management, agent and load systems, battery storage systems and solar photovoltaic systems. The system is decentralized and complex, thus, it requires distributed energy management that can be implemented using PLC, meters and microcontrollers (Yuanrui and Jie, 2008). A complex connection of hybrid systems was provided by Hoomen et al. (2003). In this system, a small scale wind generators and solar photovoltaic are connected to AC bus that is also connected to battery storage and engine driven generators in series or parallel connection like as shown below. Parallel connection of combined power sources This connection is widely accepted as the most practicable alternative to the conventional power supply. The system provides enough storage that allows the load to be shifted, so that the there is a continuous supply of electrical energy. This system is more reliable compared to single source system. It application range from small power supply for a single household, which provides electrical power for lighting and other application, to a village power grid. Since the panels operate at high DC voltage, the cost of wiring is reduced and it has a better overall efficiency. The wind turbine extract more energy at low wind speed, has reactive power support, load voltage stability minimum converter power rating that result in low cost. It can also operate in grid connected or stand alone modes (Lal, Dash & Akella, 2011). Different studies on optimization of renewable energy hybrid based on their size as well as their operation technique of generating power have also been studied. Morea et al. (2007) gave an algorithm technique to size and analyze the cost of a standalone solar PV, wind hybrid system. They applied design technique of energy generation that supplies local household. The system provides optimized hybrid power systems. The only set back is the number of variables which depends on each other intrinsically. However, this dependency can be useful when there is a need to evaluate different models or prices of the components. The potentials of PV-wind hybrid power systems can be evaluated using conventional design technique to evaluate if the technology or the cost of various components. an optimum size of hybrid of PV/wind power system can be obtained by recording the power output in an hourly basis or average daily power output in a month. The difference between the PV array capacity and the battery bank assist in calculating the optimum value at least cost. Linear programming has been employed in minimizing the load requirements. It was found that load requirements are meet in a most reliable manner (Morea et al., 2007, 439-441). Unit sizing of integrated power supply is important when deciding on the cost and reliability of the system. Zelinka, Vasant, & Barsoum, (2013) discussed different approaches used to determine the wind generation capacity and the number of solar PV and batteries required for a standalone system. They proposed a design that produces optimum hybrid wind-solar power for a standalone unit or for connection to grid. They used a linear programming technique to reduce the cost of production of electricity at the same time producing the required load in a reliable way, taking environmental issues into consideration. Bansal, Bhatti, & Kothari (2004) research on ways of optimizing the capacity of sizes for different components of a hybrid solar – wind power systems using power bank. HOMER software has been used for sizing. It has a range of energy components and can be used to evaluate a specific technology based on the availability of resources and the cost. This analysis requires the information about the economic and resources constraints, and other controls. It requires information about the components types, their longevity, efficiency and costs. HOMER software has also been used in analysis of solar/wind hybrid power systems. The cost per kilowatt of utility supply is also determined (Zelinka, Vasant, & Barsoum, 2013). Generation of renewable energy in UK There has been steady increase in the use of renewable energy sources in UK. The amount of electrical power produced from renewable sources in 2014 increased by 64,654 GWh over that of 2013. The largest contributor was wind generation with a total generation of 32,016 GWh. This is attributed to an increase in installation compared to the previous years. Hydro generation recorded an increase of 25% to 5,885 GWh, because of high amount of rain in the catchment areas. Biomass contributed an increase of 4,176 GWh from 2013, while solar photovoltaic generated 4,050 GWh. Generally, in 2014, the generation of electrical energy by wind represented 50% of the total sum of the renewable energy, biomass contributed 35%, hydro generation contributed 9.1% and solar photovoltaic contributed 6.3%. The progress of generation of electrical energy since 2004 is shown below. Most of the electrical energy obtained from renewable sources in UK, comes from medium and large hydro electric plants. There is also a potential to expand these plants, but there is increase more focus on the use of wind to produce electrical energy and waste to produce biogas energy. The government had relegated wave and offshore energy to a long term process due to the cost involved, but to the history of UK’s maritime, this energy sources may not be ignored for long. Information about solar, hydro and wind energy indicates that there is a lot of potential for installation of hybrid energy systems design in most parts. Chapter 2: Energy Evaluation The basic energy needs of the settlement The basic function of energy for a settlement in remote places include power for pumping water and energy for cooking, flour mill and pumping water. The settlement is located far from power grid and has low loads. One of the options that can be used to meet the energy needs of rural electrification, flour mill and pumping in rural areas is to install stand alone units based on available sources of energy. There are different options that can be used in this project. They include the solar systems, wood gas and biogas. Power loads in rural area The common load for a rural community mainly composed of peaks in morning and evening, mostly due to lighting, midday peak, and night and day load. The demand of energy in rural places in night hours is very low and hence the load during night hours is quite low compared to evening and morning. The typical electrical power load in a rural settlement is shown in the graph below. Power generation using diesel engines are not usually run to supply low power over a long time, due to the fact that, the engines may suffer from degradation due to low factor, together with unnecessary consumption of fuel which may not be economical in the long run. Thus, different energy sources are used in different hours during the day to better match the load levels. In this perspective, a hybrid of solar PV and battery bank provides a low electrical power suitable for low loads for many hours. Diesel generator is used to provide power to meet the evening peak and may also charge the batteries where necessary. Connected load The village community would use two lights for each house with working rate of 4 hr per day. The total load in the settlement in kilowatt-hour = 14 households x power consumption in a day. The power consumption per household per day is given below. Fluorescent lamp 1 x 40 = 40W Bulb 1 x 15 = 15 W Street lights, 8 x 40 W = 320 W The total power demand per household = 375W Total power required in the village = 375 x 14= 5.25 kW To cover for the power demand for the settlement, a turbine that can produce 10kW of wind power at night will be useful. To cover for the fluctuation in the wind speed, PV system that can produce 10 kW can be installed. When the wind is strong, PV systems and batteries should be put off, unless the demand exceeds the power produced by the turbine. Chapter 3: Solar Scheme A solar scheme consists of a standalone Photovoltaic system with one or several solar PV modules connected to electrical appliances in a homestead. They can be put into different categories depending on their power dimensions. a) Pico PV systems This system is a small solar home system that produces a power output of between 1 to 10W, which can be used essentially for lighting. It is meant to replace inefficient and unhealthy sources of light such as candles and kerosene. Small ICT appliances such as a radio or a mobile phone can also be added. The system has a solar panel and a battery which can also be used as a lamp. The devices are arranged as shown below. This system has advantages such as its low costs, it is easy to install, its flexibility to use, require little maintenance, friendly to the user and has high degree of expandability (Rolland, 2011; Poullikkas, 2013). b) Classical home systems This system produces a maximum output of 250W. It has different components such as the battery, charger controller, loads and PV modules like as shown below. Charger controller is the central component in the system and its work is to manage the overall energy. The advantages of these systems include its direct use by DC loads such as radio, fridge, TV and lamps without any need of conversion, increasing the efficiency of the system. AC loads can also be integrated through the use of DC/AC inverter, though they are often oversized and inefficient, which may affect the storage capacity of the systems in the long run, and might cause permanent damage (Rolland, 2011). c) Solar residential system This is a large stand alone PV system which provides electricity to larger installations like schools, hospitals and factories, and provides a wider range of application loads. It consists of an inverter that allows the use of AC loads. It can be used to power larger working machines and instruments. Its power output range from 500W to 4000W, and usually integrated with 12V and 24V batteries. They are arranged as shown below. (Rolland, 2011) Chapter 4: Hydro Scheme A hydropower system consists of a turbine and a generator. The turbines are in the capacity range of 0.2kW to 800kW, and thus can provide solutions to different local situations, given that there is availability of water flow. Small hydro plant has a capacity of 10MW, mini hydro plant is below 1kW, micro hydro plant is below 100kW, and pico is below 20kW. The common types of turbines are Pelton, Kaplan, Banki and Francis turbines. Banki is also called cross-flow and is used in high heads, while Kaplan is mainly used for low heads. The turbines convert kinetic energy into mechanical energy, which can be used by a generator to produce electrical energy (Rolland, 2011). The turbines that can be used include an asynchronous grid type for grid connected plants, synchronous generator for larger units and a permanent magnet generator used in smaller units (Poullikkas, 2013). Installation Small hydro plant is located on a river with steady flow. Sites that are best suited for the installation of this plant are places that has elevation drop, catchment area where water will drain into the river, and an area with high precipitation in a year. There are three types of hydropower plants that can be used. This includes kinetic power, diversion and weir plant. Diversion and weir uses gravitational energy of water because of elevation drop. The kinetic energy from water moving in a river can be utilized by kinetic energy devices. Diversion and weir are most suitable for mountainous or hilly places, because they produce more energy with an increase in elevation, while for a kinetic turbine; the best site for their location is a plain. However, the river must be free from sediments, have solid riverbed, its velocity must be greater than 1m/s, appropriate depth and flow continuously all year round. The strongest river current is located close to the surface and at the centre where they are not impeded by friction with riverbed or river banks. Water flowing at a corner accelerates on the outside than the inside (Poullikkas, 2013). Apart from choosing the type of scheme to be used in power generation, the knowledge of the surrounding and its layout are important in hydropower, as it interact with its environment. Information about hydrology cycle is important in order to predict the time distribution and availability of flow rates. The hydrological work should include the maximum flood of the river so as to prevent damage to equipment (Poullikkas, 2013). Chapter 5: Scheme Interconnection A hybrid grid ensures the continuous and reliable supply of electrical energy that can be used for domestic use such as water supply, lighting and refrigeration. They can also be used in public services such as for irrigation hospitals and schools. In this connection, electrical power produced from solar photovoltaic is feed into DC bus line and charge battery. A charge controller controls and protects the battery from discharge and overcharge. The batteries supplies electrical energy to AC loads through AC/DC inverter. However, DC bus can also supply power to directly to DC loads. The overall connection between hydropower plant and a PV system is as shown below. A parallel connection between PV systems and hydropower plant The hydro power plant is connected to an AC bus line which is also connected to AC loads. The PV systems, on the other hand, are connected to the battery bank which is also connected to a DC bus line. DC power is also supplied by other sources connected to DC bus line. PV systems supply energy mainly during the day to the batteries and to the loads. The battery banks acts as power backup source, and are useful when the sun has gone down. Thus, the hybrid power plant supplies constant power throughout the day (Lal, Dash & Akella, 2011). Summary This paper has presented a framework for the development of renewable energy technology in a remote statement which is not connected to the main power grid system. A hybrid system is a design that provides power from renewable energy sources at a low cost. The unique system produces a sufficient amount of electrical energy to meet the demand of remote settlement. It gives a healthy environment if it is used over energy resources, as well as improves the economy in rural areas. The performance of a hybrid system may be affected by environmental conditions. This result is power variation. By integrating different energy sources, more reliable supply of electrical power is maintained. References Abramsky, K. (2010). Sparking a worldwide energy revolution: Social struggles in the transition to a post-petrol world. Oakland, CA: AK Press. Bansal, R. C., bhatti, T. S., & kothari, D. P. (January 01, 2004). Automatic Reactive Power Control of Isolated Wind-Diesel Hybrid Power Systems for Variable Wind Speed/Slip. Electric Power Components and Systems, 32, 9, 901-912. GOV.UK, Special feature – Renewable energy in 2014 Johansson, T. B., Patwardhan, A., Nakićenović, N., Gomez-Echeverri, L., & International Institute for Applied Systems Analysis. (2012). Global Energy Assessment (GEA). Cambridge: Cambridge University Press. Lal, D. K., Dash, B. B., & Akella, A. K. (December 01, 2011). Optimization of PV/Wind/Micro-Hydro/diesel hybrid power system in homer for the study area. International Journal on Electrical Engineering and Informatics, 3, 3, 307-325. Markvart, T. (2000). Solar electricity. Chichester: Wiley. Morea, F., Viciguerra, G., Cucchi, D., Valencia, C., & International Telecommunications Energy Conference. (September 01, 2007). Life cycle cost evaluation of off-grid PV-wind hybrid power systems. 439-441. Rolland S., (2011). Rural Electrification with Renewable Energy, Alliance for Rural Electrification, Brussels, Belgium Poullikkas, A. (2013). Renewable energy: Economics, emerging technologies, and global practices. Hauppauge, New York: Nova Science Publishers, Inc. Yuanrui, C., Jie, W., & 2008 11th International Conference on Electrical Machines and Systems (ICEMS 2008). (October 01, 2008). Agent-based energy management and control of a grid-connected wind/solar hybrid power system. 2362-2365. Zelinka, I., Vasant, P., & Barsoum, N. N. (2013). Power, control, and optimization. Cham: Springer. Read More