PICO-HYDRO GENERATION - Selection of Components for Pico-hydro Project, Thesis of Engineering

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PICO-HYDRO GENERATION IN KAHULUGAN SPRING RESORT:

Selection of Components for Pico-hydro Project

Chapter 1 Introduction 1.1 Background What is hydropower system? A hydropower system captures the energy of moving water for some useful purpose like converting it to mechanical power or electrical power without polluting the air or water. Wherever there is mountain and streams hydropower can be capture to utilize as an alternative renewable source. People have been obtaining the energy from the water for a long time and still being used now a day on many different scales for many purposes, from small grain grinding facilities to huge hydroelectric dams that provide an entire city. Hydropower plant has been growing all over the world because of its important role to help the current issue of the global warming. The hydropower plant can be classified according to the size of electrical power it produces as shown in the table. Table 1. 1 Classification of hydro power plant Power Class More than 10 MW Large 1MW to 10MW Small 100kW to 1MW Mini 5kW to 100kW Micro Less than 5kW Pico Pico hydro is the term use to describe the smallest system that covers hydroelectric generation of less than 5 kilowatt. Depending on its size, a Pico-hydropower system may provide a small, remote community with adequate electricity to power light bulbs, radios, and televisions, among other appliances. Pico-hydro is small compared to hydropower classification but it has significance in contributing for free electricity for household or community. The system does not require dam, instead its uses run- off the river application through penstock to provide the head and flow rate to the turbine.

 Electricity of the Philippines is one of the most expensive electricity in the world Electricity is now a necessity now a day. Philippines is currently facing an power shortage that challenges electrical engineer to resolve the issue. In addition, Philippines electricity belongs to one of the most expensive electricity in the world which is bad for the economy of the country. The issue make sense to have alternative renewable source in order to have cheaper electricity and help the power shortage in the country. It encourages the use of alternative renewable source like pico hydro which the municipality of Jasaan specially kahulugan spring resort has the potential to acquire this renewable source because of the abundance of the water. The potential of the resort will not be utilize unless obtaining the right components to harness the energy and to prevent the loads for damage. In this research study, the problem must be response the proper components which is available in the market that will be used to get the potential of the excess water of the resort. 1.3 Objectives The objectives of this research study is  To select components for pico-hydro that is available in the market  To select components that can be reproduced by other resort.  To select components that can accumulate the change in flow rate Renewable energy sources such as wind and solar are being scaled up from residential to electric utility size. In contrast, hydro power is being scaled down to residential size. Because of this instance the components must not available in the market for the residential. This is the objective of the research study to select component that is available in the market that will suit to the demand of the selected load. 1.4 Significance of the study  Introduce the idea of pico hydro as an alternative renewable source which can be harness from the excess water of the resort

 Because of the decrease of study for the design for pico hydro, the research helps to select components that is available in the market and help to the development for small hydro power plants  It is responsible for less environmental impact  There is lack in development of pico hydro in the municipality. It gives useful idea how to harness the energy from the water which is abundant in the municipality.  Other resort or residential housed may use of the research to have alternative renewable energy provided that the setting is similar. 1.5 Scope and Limitation The research will introduce the available components that are available in the market to produce supply electricity to the selected load in the resort. It is limited in getting the maximum power output of the excess water due to imperfect civil works. The research is restricted only in selecting the components of the pico hydro system that are available in the market. It only provides the potential alternative renewable source of electricity in selected load in kahulugan spring resort by the use of its excess water from the pool. Selecting of the turbine for the generation of renewable energy is excluded in the research project . The power output of the selected components is based on the data collected and it is limited to provide electricity in the entire area. The research provides the components that can be used to harness the potential power for an alternative renewable source of electricity. The components of the research are restricted only for off-grid generation that will provide the electricity in the selected loads. The loads that can be operated of this study are limited only in non-motor driven load like cfl. Simulation in the system is not performed in this research. The researcher limits in the performance of the alternator.

Water may be utilized for power generation if it possesses enough potential energy. As water flows from highlands to lower elevations, its potential energy is reduced by evaporation, drop in elevation, friction, and turbulence. The remaining part can be converted into mechanical energy by turbines and generators convert this mechanical energy into electrical energy. [5] 2.2 Renewable Energy Renewable energy is from an energy resource that is replaced by a natural process at a rate that is equal to or faster than the rate at which that resource is being consumed. Hydropower is considered as a renewable source of energy because it uses the earth’s natural water cycle to generate electricity. Water constantly moves through a vast global cycle evaporating from lakes and oceans, forming clouds, precipitating as rain, and then falling back to the ocean. One third of the solar radiation reaching the Earth is responsible for running of the hydrologic cycle [5]. Because of the hydrologic cycle the water will never fade that consider it a renewable energy source. Moreover hydro power is the largest renewable use to generate electricity. All hydropower plants whether a run-of-river or a storage plants is a renewable energy. Small-scale hydropower is one of the most cost-effective and reliable energy technologies to be considered for providing clean electricity generation [6]. Currently, many developing countries rapidly have implementing the pico-hydro generation system due to anxiety of the fossil fuels shortage and the volatile of oil prices. Furthermore, pico hydro system has become one of the most people’s choices because 70% of the earth's surface is covered by water [3]. Since water is a domestic resource, hydropower provides independency in terms of energy and fosters energy security and price stability [5]. 2.3 Principal operation of run-off river plant This type of plant generally does not have storage. By means of a diversion weir, water is diverted from the river and given to the transmission canal [5]. At the end of the transmission canal there is a forebay which facilitate the gentle flow for the intake. Moreover forebay serve also as a filter for the debris from the weir. The general layout of the run-off river plant is given if figure 2.1. Penstock is a pressurize pipe that delivers the water from the forebay to turbine, this result to the turbine to rotate and convert the water energy to mechanical energy All installations need to

have a valve or sluice gate at the top of the penstock which can be closed when the turbine needs to be shut down and emptied of water for maintenance. When this valve is closed, the water is diverted back to the river down a spillway [6]. The torque and rotation of the runner and shaft rotate a generator, directly or with a mechanical transmission, and the mechanical power is converted to electrical power [11]. Figure 2. 1 run-off river schematic diagram The power output of the system depends on the head and flow rate of the river. The higher the head and the more flow rate the more power can be generated in the system. [11]

2.4 Stand-alone system Pico hydro can alternatively be used for providing energy to remote locations like mountain refuges, isolated houses etc. In stand-alone systems, as the energy is directly used by the loads, an effective regulation of the output voltage and frequency is important for the electrical loads in order to ensure a stable voltage and frequency, equal to 230 V and 60 Hz respectively [10]. Water energy that is converted to electrical energy can provide electricity for stand-alone application. The most common loads for stand-alone application are the lightings and entertainment loads for the residential houses. The voltage and frequency of the system must be stable to avoid short in life span and damage in the loads. Effective speed regulation and control are important in electricity generating systems to ensure that the voltage and frequency remain constant. In autonomous micro hydro power plant it is difficult to maintain constant voltage and frequency at load terminals due to the fluctuating load conditions and variable output power with the change in water discharge[6]. When the plant does not match the electricity demand, a solution can be represented by the utilization of DC batteries. This arrangement enhances the flexibility of the plant despite a greater technical complexity and more instrumentation requirements [8]. 2.5 Hydropower Potential Hydropower potential is generally evaluated in three categories, namely theoretical, technical and economic potential. Theoretical potential is defined as the sum of the annual energy potentially available from all natural flows from the largest rivers to the smallest creek, regardless of the losses. Technical potential is the part of theoretical potential which can be utilized with the current technology regardless of economic and other considerations. This definition of potential subtracts friction losses in water ways and efficiencies in the electro-mechanical equipment as well as the extreme low heads which are considered as infeasible.

Technical potential is a function of theoretical potential. Since changes in hydropower technology is not rapid and no big changes are expected in the near future, technical potential can be accepted as constant. In other words, it does not vary with time, Estimates the effect of these inevitable losses as 50 %. Economic potential is the part of the technical potential which can be regarded as economic when compared to alternative sources of power like oil and coal. It is dependent on the cost of alternative sources. Therefore, it may change with time and should be updated regularly.[5] 2.6 Generators for pico hydro In pico hydro applications turbines come generally with generators as a single unit, sometimes directly coupled some others with driven belts. There are cases in which turbine and generator are chosen separately and matched together. Generators are divided into synchronous generators and asynchronous generators (induction generators). The produced output is AC (Alternate Current) that is the unique possibility to limit losses when long distances must be covered. A third typology is DC generator (like common truck alternator). They are generally used to charge batteries. Most electric loads are AC but sometimes it is possible to find DC electric loads. 2.6.1 Generators Generators use an armature (wire wound around and around) surrounded by a set of unmoving field coils, likes a DC motor. The field coils are powered, and the regulator controls current to the fields to control the output of the generator. As the armature turns, electrical current is induced in its windings.

2.6.3 Asynchronous generators (inductions generators) The Cage Rotor The key component of the asynchronous generator is the cage rotor (it used to be called a squirrel cage rotor but after it became politically incorrect to exercise your domestic rodents in a treadmill, we only have this less captivating name). It is the rotor that makes the asynchronous generator different from the synchronous generator. The rotor consists of a number of copper or aluminium bars which are connected electrically by aluminium end rings. The rotor is provided with an "iron" core, using a stack of thin insulated steel laminations, with holes punched for the conducting aluminium bars. The rotor is placed in the middle of the stator, which in this case, once again, is a 4-pole stator which is directly connected to the three phases of the electrical grid [12]. Motor Operation When the current is connected, the machine will start turning like a motor at a speed which is just slightly below the synchronous speed of the rotating magnetic field from the stator. If we look at the rotor bars from the previous picture, there is a magnetic field which moves relative to the rotor. This induces a very strong current in the rotor bars which offer very little resistance to the current, since they are short circuited by the end rings. The rotor then develops its own magnetic poles, which in turn become dragged along by the electromagnetic force from the rotating magnetic field in the stator. Generator Operation If we manually crank this rotor around at exactly the synchronous speed of the generator, e.g. 1500 rpm, as we saw for the 4-pole synchronous generator on the previous page nothing will happen. Since the magnetic field rotates at exactly the same speed as the rotor, there will be no induction phenomena in the rotor and it will not interact with the stator.

If speed is increased above 1500 rpm then the rotor moves faster than the rotating magnetic field from the stator, which means that once again the stator induces a strong current in the rotor. The harder is cranked the rotor, the more power will be transferred as an electromagnetic force to the stator, and in turn converted to electricity which is fed into the electrical grid[12]. Generator Slip The speed of the asynchronous generator will vary with the turning force (moment, or torque) applied to it. In practice, the difference between the rotational speed at peak power and at idle is very small, about 1%. This difference in per cent of the synchronous speed, is called the generator's slip. Thus a 4-pole generator will run idle at 1500 rpm if it is attached to a grid with a 50 Hz current. It is a very useful mechanical property that the generator will increase or decrease its speed slightly if the torque varies. This means that there will be less tear and wear on the gearbox, because of lower peak torque. This is one of the most important reasons for using an asynchronous generator rather than a synchronous generator on a wind turbine which is directly connected to the electrical grid [12]. 2.6.4 Alternators An alternator differs from a dc motor in that it contains no permanent magnets. Instead, there are two concentric wound coils of wire within the alternator: a stator coil (the outside coil which does not rotate) and a rotor coil (the inside coil, attached to the alternator’s pulley, which does rotate). The rotor is also referred to as the alternator’s "field." An electromagnet is created when current flows through the field coil. The strength of the magnet is directly proportional to the amount of current flowing through the field. As the rotor moves clockwise, the resultant magnetic field sweeps clockwise through the outer coil of wire, and electricity is generated in the stator coil. Since the magnetic field sweeps back and forth through the stator coil, an alternating current is produced. The alternating current has a frequency equal to the frequency with which the alternator’s pulley is rotating.

2.6.5.2 The difference between asynchronous and synchronous generator A synchronous generator is called “synchronous” because the waveform of the generated voltage is synchronized with the rotation of the generator. Each peak of the sinusoidal waveform corresponds to a physical position of the rotor. The frequency is exactly determined by the formula f = RPM x p / 120 where f is the frequency (Hz), RPM is the rotor speed (revolutions per minute) and p is the number of poles formed by the stator windings. A synchronous generator is essentially the same machine as a synchronous motor. The magnetic field of the rotor is supplied by direct current or permanent magnets. The output frequency of an asynchronous generator is slightly (usually about 2 or 3%) lower than the frequency calculated from f = RPM x p / 120. If the RPM is held constant, the frequency varies depending on the power level. The peaks of the waveform have no fixed relationship with the rotor position. An asynchronous generator is essentially the same machine as an asynchronous or induction motor. The magnetic field of the rotor is supplied by the stator through electromagnetic induction. The output frequency of a synchronous generator can be more easily regulated to remain at a constant value. Synchronous generators (large ones at least) are more efficient than asynchronous generators. Synchronous generators can more easily accommodate load power factor variations. Synchronous generators can be started by supplying the rotor field excitation from a battery. Permanent magnet synchronous generators require no rotor field excitation. The construction of asynchronous generators is less complicated than the construction of synchronous generators. Asynchronous generators require no brushes and thus no brush maintenance. Asynchronous generators require relatively complicated electronic controllers. They are usually not started without an energized connection to an electric power grid, unless they are designed to work with a battery bank energy storage system. With an asynchronous generator and an electronic controller, the speed of the generator can be allowed to vary with the speed of the wind. The cost and

performance of such a system is generally more attractive than the alternative systems using a synchronous generator [12]. 2 .7 Electrical Components. 2.7.1 Electronic Load Control If the voltage and frequency are not kept at the right level then the user loads connected to the generator can be damaged. Table 2. 2 Effect of voltage and frequency in loads Too High Too Low Voltage Motors, television and can be damage, lifetime of light bulbs and heaters become shorter Most appliances have reduced performance or fail to operate Frequency Will not usually cause problem with Can cause internal circuit to overheat The speed of the turbine changes when the load connected to the generator changes. For example, if more lights are switched on then the speed of the turbine will decrease. Since this change of speed affects the voltage and frequency, the load on the generator must be kept constant or the flow of water through the nozzle must be adjusted. The most reliable method of controlling the load and keeping the voltage and frequency constant is by using an electronic load controller. The speed of an induction generator can be kept near constant by using an IGC (Induction Generator Controller). This device sends any unused power to a ballast (or dump load) so that the total load on the generator remains constant. For example, if the generator produces 1000 Watts and the total load connected by the consumers is only 600W then the IGC will control the switching on and off of the ballast so that the remaining 400W is also dissipated. If the consumer load changes at any time, the IGC will automatically adjust the power diverted to the ballast so that the voltage and frequency are kept constant.

2.7.3 Batteries A car's battery is designed to provide a very large amount of current for a short period of time. This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs, so a car battery may go through its entire life without ever being drained more than 20 percent of its total capacity. Used in this way, a car battery can last a number of years. To achieve a large amount of current, a car battery uses thin plates in order to increase its surface area. A deep cycle battery is designed to provide a steady amount of current over a long period of time. A deep cycle battery can provide a surge when needed, but nothing like the surge a car battery can. A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates. A car battery typically has two ratings:  CCA (Cold Cranking Amps) - The number of amps that the battery can produce at 32 degrees F (0 degrees C) for 30 seconds  RC (Reserve Capacity) - The number of minutes that the battery can deliver 25 amps while keeping its voltage above 10.5 volts Typically, a deep cycle battery will have two or three times the RC of a car battery, but will deliver one-half or three-quarters the CCAs. In addition, a deep cycle battery can withstand several hundred total discharge/recharge cycles, while a car battery is not designed to be totally discharged [17]. 2.7.3.1 Factors in sizing Battery Banks Electrical Usage The first thing you’ll need to know is the amount of energy you’ll be consuming per day. It’s worth the time to do a careful evaluation of exactly what loads (appliances, electronics, etc.) you plan to use and for what lengths of time. Keep track of this information on a loads list; you’ll refer to this list often for sizing other components as well. Your final tally should be expressed in Watt-hours (Wh) per day. If you know the kilowatt hours (kWh)

per day just multiply that number by 1,000 to determine the Watt-hours per day. (Example: 1.2 kWh = 1,200 Wh) Days of Autonomy Next, you must determine the number of days of battery back-up that you want to have on hand. In other words, if you are unable to charge your batteries by any means, and you still need to draw power, you must provide this additional storage by increasing the size of your battery bank. For solar panel If you conclude that you need more then five days of battery backup, you may want to explore multiple sources of electricity generation or backup generator options (like a fossil-fueled generator). If your primary electricity source is wind power, determine the number of days when there is little or no wind. This information can be found in the data you’ve collected using your data- logging anenometer. Hydroelectric turbine systems are unique because they usually operate continuously, and therefore do not require extensive storage. If you’re sizing a battery bank to be used in conjunction with an on-demand fuel-powered generator, the number of days of backup will represent the number of days you wish to go without using your generator. Depth of Discharge Figure 2. 2 Battery Life based on Depth of Discharge