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November 4, 2020
Major Components of a Hydro System A hydro system is a series of interconnected components: water flows in one end, and electricity comes out the other. This section provides a high-level overview of these components, from the water source to voltage and frequency controls.
Water Diversion (Intake)
The intake is typically the highest point of your hydro system, where water is diverted from the stream into the pipeline that feeds your turbine. In many cases a small dam is used to divert the water. (In most large hydro projects, the dam also creates the HEAD necessary to drive the turbine.) A water diversion system serves two primary purposes. The first is to provide a deep enough pool of water to create a smooth, air-free inlet to your pipeline. (Air reduces horsepower and can
cause damage to your turbine.) The second is to remove dirt and debris. Screens can help stop larger debris such as leaves and limbs, while an area of “quiet water” will allow dirt and other sediment to settle to the bottom before entering your pipeline. This helps reduce abrasive wear on Major components of a hydro system include a water your turbine.diversion, pipeline to create pressure, turbine & generator,tailrace for exiting water, and transmission wires.
The pipeline, sometimes called the penstock, is responsible for not only moving water to your turbine, but is also the enclosure that creates Head pressure with increasing vertical drop. In effect, the pipeline focuses all the water power at the bottom of the pipe where your turbine will connect. In contrast, an open stream dissipates the energy as it travels down the hill. Pipeline diameter, length, and routing all affect efficiency, and thhere are guidelines for matching the size of your pipeline to the
Design FLOW of your system. As you’ll see later, a small-diameter pipeline can considerably reduce your available horsepower, even though it can carry all available water. Larger diameter pipelines create less friction as the water travels through.
The powerhouse is simply a building that houses your turbine,generator and controls. Proper design significantly affects system efficiency, however, especially with regard to how the water enters This stainless steel intake system and exits your turbine. includes a self-cleaning screen.
Turbines and Efficiency
The turbine is the heart of the hydro system, where water power is converted into the rotational force that drives the generator. It is arguably the most important component in the system, because its efficiency determines how much electricity is generated.There are many different types of turbines, and proper selection requires considerable expertise. A Pelton design, for example, works best with high Head. A Crossflow design works better with low Head but high Flow. Likewise, other turbine types such as Francis, Turgo and Kaplan, each have optimum applications.Turbines fall into one of two major types。
Reaction turbines run fully immersed in water, and typically used in low-Head(pressure) systems with high Flow.Examples include Francis, Propeller and Kaplan.
Impulse turbines operate in air, driven by one or more high-velocity jets of water. Impulse turbines are typically used with high-Head systems and use nozzles to produce the high-velocity jets. Examples include Pelton and Turgo.A special case is the Crossflow turbine. Although technically classified as an Impulse turbine because it is not entirely immersed in water, it is used in low-Head, high-Flow systems. Pelton-type impulse turbine with housing cover removed.The water passes through a large, rectangular opening to drive the turbine blades, in contrast to the small, high-pressure jets used for Pelton and Turgo turbines.
Regardless of the turbine type, efficiency is in the details. Each turbine type can be designed to meet vastly different requirements, and minor differences in specifications can significantly impact power transfer efficiency. The turbine system is designed around Net Head and Design Flow. Net Head is the pressure available to the turbine when water is flowing (more on this later), and Design Flow is the maximum amount of Flow the hydro system is designed to accommodate. These criteria not only influence which type of turbine to use, but are critical to the design of the entire turbine system. Minor differences in specifications can significantly impact power transfer efficiency. The diameter of the runner (the rotating portion), front and back curvatures of its buckets or blades, casting materials, nozzle (if used), turbine housing, and quality of components all have a major affect on efficiency and reliability. The turbine runs most efficiently when it turns exactly fast enough to consume all the energy of the water. In turn, the water must enter the turbine at a specific velocity (typically measured in feet or meters per second) to maximize efficiency at this RPM. This velocity is determined by Head pre Optimizing Water Velocity Since power is a combination of HEAD and FLOW, it’s easy to see how a larger orifice that moves more water (Flow) at the same velocity could generate more electricity. Conversely, as Flow drops off in the dry season, the orifice must be made smaller to maintain the same optimum velocity for efficient power transfer. Keep in mind that turbine speed is not wholly dependent on water velocity; the turbine will turn at a constant speed because it is directly coupled to the generator, where a Governor is maintaining stable RPM by controlling the load. But as the disparity between actual and optimum water velocity grows, less of the energy from the water is transferred to the turbine.
The correct orifice ensures the system is operating at its most efficient level.Impulse turbines (such as a Pelton)are often equipped with a variety of fixed-orifice nozzles that can be used to accommodate changes in Flow. A disadvantage of a fixed nozzle is that the turbine must be shut down to This needle nozzle provides infinitely variable adjustments to make changes. A popular option is accommodate changes in Flow.the adjustable needle nozzle, which allows on-the-fly changes with an
infinite number of settings.If you know your Head and Flow, your turbine supplier should be able to make specific recommendations for a turbine system and provide a close estimation of efficiency.
The drive system couples the turbine to the generator. At one end, it allows the turbine to spin at its optimum RPM. At the other, it drives the generator at the RPM that produces correct voltage and frequency.The most efficient and reliable drive system is a direct, 1:1 coupling between the turbine and generator. This is possible for many sites, but not for all Head and Flow combinations. In many situations it is necessary to adjust the transfer ratio so that both turbine and generator run at
their optimum, but different, speeds. These types of drive systems can use either gears, or pulley and belts, all of which introduce additional efficiency losses into the system. Belt systems tend to be more popular because of their lower cost. Your turbine manufacturer can provide valuable guidance about matching turbine and generator RPM, and suggest options Belt drive coupling between turbine and generator.if a direct, 1:1 coupling is not possible.
The generator converts the rotational power from the turbine shaft into electrical power. Efficiency is important at this stage too, but most modern, well-built generators deliver good efficiency.There can be big differences in the type of power generated, however. DC (Direct Current) generators can be used with very small systems, but typically are augmented with batteries and inverters for converting the power into the AC (Alternating Current) power required by most appliances.
AC generators are normally used in all but the smallest systems. Common household units generate 120VAC (volts AC) and 240VAC, which can be used directly for appliances, heaters, lights, etc. AC voltage is also easily changed using transformers, which makes it relatively simple to drive other types of devices or transmit over long distances. Depending on your power requirements, you can choose either single-phase or three-phase AC generators in a variety of voltages. One critical aspect of AC power is frequency, typically measured as cycles per second (cps) or Hertz (Hz). Most household appliances and motors run on either 50Hz or 60Hz (depending on where you are in the world), as do the major grids that interconnect large power generating stations. Frequency is determined by the rotational speed of the generator shaft; faster rotation generates a higher frequency.