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Cogeneration means combined heat and power (CHP). Cogeneration is defined as the sequential generation of two different forms of useful energy from a single primary energy source. It produces electricity and thermal energy at high efficiencies using a range of technologies and fuels. Cogeneration used for many years all over the globe across different industries in several forms like steam boilers and steam turbines, gas turbines, reciprocating engines, and heat recovery systems. In Cogeneration, the fuel is used first to drive the prime mover to generate electricity and produce heat. The heat is then used to boil water and generate steam. Some of the steam is used to support a process while the remaining steam is used to drive a steam turbine to generate additional power.
Cogeneration is very efficiently helpful by using waste heat recovery technology to capture wasted heat associated with electricity production. Cogeneration systems typically achieve total system efficiencies of 60 to 80%. For micro-cogeneration systems, the main output is heat, with some electricity generation, at a typical ratio of about 6.1 for domestic appliances.
In the case of steam turbines, cogeneration technologies widely commercialized include extraction and backpressure steam turbines. The capital cost to build a cogeneration plant and the size of the plant required to demand a constant load 24/7 for viability and financial advantages, but the main advantage of this type of cogeneration is the long plant life for the steam turbines due to low wear and tear. In steam cogeneration systems the fossil fuels mostly used are coal, oil, and natural gas.
Cogeneration is likely to be most attractive because the requirement of demand for both steam and power is balanced which is consistent with the range of steam. And also power output ratios that can be obtained from only suitable cogeneration. Cogeneration is also most likely to be attractive for a single plant or group of plants that has sufficient demand for steam and power to permit economies of scale to be achieved. Cogeneration also helps peaks and troughs in demand can be managed or, in the case of electricity, adequate backup supplies can be obtained from the utility company.
The ratio of heat to the power required by a site may vary during different times of the day and seasons of the year. Importing power from the grid can make up a shortfall in electrical output from the cogeneration unit and firing standby boilers can also satisfy additional heat demand.
Turtle Turbines is one of the most reputed Steam Turbine Manufacturers In India. Turtle Turbines has been in the business of supplying Steam Turbines for Cogeneration and Micro Cogeneration. Turtle Turbines has supplied numerous Steam Turbine Cogeneration plants across India, South East Asia, and African Countries.

A governor is the component of the steam turbine control system that regulates the rotational speed in response to changing load conditions. The governor output signal manipulates the position of the steam inlet valve or nozzles which in turn regulates the steam flow to the turbine. The governing of the turbine is necessary as a turbine is directly coupled to an electric generator which is required to run at a constant speed under all fluctuating load conditions
In a steam turbine, there are three types of governors are used.
Throttle Governing of Steam Turbine
Nozzle Control Governing Of Steam Turbine
Bypass Governing of Steam Turbine.
Throttle Governing of steam turbine
In this governing system, the pressure of the steam turbine is reduced at the Turbine entry thereby decreasing the availability of energy. In this method, steam is pass through the restricted passage thereby reducing its pressure across the governing valve. The flow rate is control through a partially opened steam turbine control valve. Throttle governing is used for small turbines. Its cost is less and it has a simple mechanism. In throttle governing the steam is throttled whenever the load falls below the design load to maintain turbine speed constant. In this system, a centrifugal governor is driven from the main shaft of the turbine by belt or gear arrangement. A control valve is used to control the direction of oil flow.
Nozzle control governing steam turbine
Nozzle control governing of steam turbine is basically used for part-load condition. Some sets of nozzles are grouped together and each group of the nozzle is supplied steam controlled by valves.
Bypass governing of steam turbine
The bypass line is provided for passing the steam from the first stage nozzle box into a later stage where work output increases. This bypass steam is automatically regulated by the lift of the valve which is under the control of the speed of the governor for all loads within its range.

The rotor is statically and dynamically balanced when it is assembled with blades. Each bladed disc is individually balanced prior to assembly for built-up rotors.
Static balance means that the weight is evenly disposed around the axis of the shaft. It can be checked by rolling the rotor on horizontal knife-edge supports.
Dynamic balance means that the moments of the out-of-balance weights along the axis about either bearing add up to zero. This is checked by spinning the rotor on resilient bearings, detecting the vibration, and adding or subtracting weights until the vibration is negligible.

A modern balance machine allows for high-precision balancing and, to a significant part, removes the trial-and-error methods of the past.
Rotors are normally balanced at low speed and weight adjustments are made in two convenient planes, one at each end of the rotor. This adjustment may be by varying screwed plugs in tapped holes, or by adding balance weights at specific circumferential positions. Tee slots are machined circumferentially in the periphery of the rotor front and rear half-coupling flanges to permit the weights to be positioned and retained.

The aim of balancing is to reduce the amplitude of vibration to a tolerable level, which can be taken to be about 25 /mi at the bearing pedestals.
As rotors become larger and more flexible, it is increasingly important to understand their modal behavior so that balancing can ensure smooth running over the speed range.

Larger LP and generator rotors with essential speeds below running speed are overseeded and, if necessary, balanced in a vacuum chamber in the fully-bladed condition, where they may be run without being overheated owing to windage.

Rotors are run in bearing bushes and pedestals as closely as possible to simulate site conditions in the vacuum chamber and the high-speed pit. Measurement of journal or pedestal vibration is possible, and balancing can be done at precisely controlled speeds anywhere in the range required. The vibration margin provided by the balancing standards obtained during factory testing must be sufficient to accommodate site conditions.

Turtle Turbines balances its Rotors using the best the class technology from Schenk Germany to stringent ISO Grades.

Heat rate is defined as the total amount of energy required to produce one-kilowatt hour (kWh) of electricity by electric generators or power plants that convert fuel into heat and into electricity. The heat rate is equal to the (input energy) / (output energy). Steam Turbine heat rate is the ratio of total heat rate energy utilized in the steam turbine divided by electricity generation through the steam turbine. Heat rate is one measure of the efficiency of electrical. Turbine heat rate tells the cyclic efficiency of the steam turbine as well as the thermal efficiency of the power plant.

If the heat rate is less then the cyclic efficiency of the Rankine cycle is more and thermal efficiency is also higher in the thermal power plant. Different data is measured in thermal power plants like flow, pressure, and temperature of main steam, cold reheat steam, hot reheat steam, and feed water to calculate turbine heat rate. Cold reheat steam flow needs to be calculated from the heat balance diagram.
It is the input rate required for generating unit power. The heat rate can also be described as the ratio of thermal inputs to electrical Output. The lower the heat rate higher the efficiency of a steam turbine. In a thermal generating system, incoming and outgoing energy typically exist in the same value or unit. The formula of heat rate is Rh = Ws x c x ∆T.
Heat rate is also important for boiler performance because net heat rate permits a better comparison of units using steam-driven components to those using electrical motors, as the steam used to drive large components is typically less expensive than electricity. But it robs the steam turbine of some capacity.
A heat rate is the inverse of efficiency. A lower heat rate is better. Heat rate is used to define the efficiency of a steam turbine.

The steam turbines are used in oil and gas, distillery, chemical plants, food processing industry, or in industries where the steam is a by-product. While operating the steam turbine at maximum load, different losses of steam occur in a steam turbine. The turbine uses every single bit of heat drop produced by steam. But practically turbine work done is much less than the isentropic heat drop of steam used. Because at the time of operation some internal losses occurred. Practically 100% gross efficiency is not possible for any turbine. When the turbine works some factors have reduced the output of the turbine, known as the losses in a steam turbine.
Following are the major losses that occur in a steam turbine.
Admission losses, Leakage losses, Nozzle Friction losses, Blade losses, Wheel Friction losses, losses due to Mechanical friction, Residual Velocity loss, losses in regulating valves, loss due to wetness of steam, Governing losses, Exhaust losses, Radiation and convection losses, Losses due to moisture, Carryover losses.
Leakage loss – Leakage loss occurs between the shaft, bearings, nozzles, and stationary diaphragms.
Windage losses – windage loss occurs when moving rotor blades come in contact with inactive steam then there is a move of energy as of blade to steam.
Nozzle Losses – When fluid is transferring from convergent to divergent or reverse then its momentum might be lost. Pressure losses occur when fluid flows from convergent to divergent. Head losses that occur in nozzles are due to pipelines.
Friction losses occur due to the flow of steam through nozzles on moving and stationary blades.
Blade friction loss – It is due to steam gliding over the blades and friction on the surface of the blades.
Wheel friction loss – When steam passes through the rotating turbine wheel, it produces some resistance on the turbine wheel.
Losses due to mechanical fraction – This loss is for turbine bearing. It is due to the shaft and wheel bearing and also the regulating valve of the turbine. This loss may be reduced by proper lubrication of the moving parts of the turbine.
Loss in regulating valves – Before entering the steam to the turbine, it passes through the boiler’s stop and regulating valve. Steam gets throttled in these regulating valves and as a result, steam pressure will be less than the boiler pressure at the entry of the turbine.
Loss due to wetness of steam – It is due to the moisture present in the turbine. When steam passes through the lower stage of the turbine, it becomes wet. At the lower stage, the velocity of water and steam are different and will not form a homogeneous mixture. That’s why the velocity of water particle is less than that of steam and water particle has to be dragged with the steam and some part of the kinetic energy of steam is lost.
Governing loss – This loss is due to the throttling of the steam at the main stop valve of the governor.
Turtle Turbines designs and manufactures Steam Turbines with required attention towards reducing the internal losses, thus our Steam Turbines deliver the highest efficiency in their class. . Turtle Turbines provide solutions for all types of failures in a steam turbine. For more information please visit https://turtleturbines.com

Rural areas and remote Villages are often at a disadvantage in terms of access to electricity. The high cost of providing this service in low populated, remote places with difficult terrain and low consumption results in rural electricity schemes that are usually more costly to implement than urban schemes.

Solar power is the conversion of sunlight into electricity. Concentrated Solar Power (CSP), in which sunlight is focused on an area containing water which is converted into steam and is used to generate power, as in a thermal power plant. CSP produces concentrated solar beam irradiation to heat liquid, solid, or gas as in a regular TPS. The best sites for CSP are in equatorial belt cloud-free regions.

Solar thermal power plants use the sun’s rays to heat a fluid to high temperatures. The fluid is then circulated through pipes so that it can transfer its heat to water and produce steam. The steam is converted into mechanical energy in a Steam Turbine which is then converted into electricity by a conventional generator.

Thus providing power to remote villages which can be effectively used for Irrigation, improves the individual quality of life, facilitates community services such as health and education, and enables business entities to carry out professional activities for rural populations.

Turtle Turbines have supplied Steam Turbine to Solar Thermal Plant at Shive in Pune with Thermax. The project was funded by the Government of India.

Better performance throughout the steam turbines’ operational life improves cost-efficiency. Today, better control is even more important than before, as older turbines operate beyond their original life expectancy.
The modern turbine control system (TCS) is designed to control the main steam flow to the steam turbine in all operational conditions by means of the turbine throttle, governor, admission, and or extraction control valves. Simplex electrical functions included within the TCS software and hardware are used to carry out the control functions. During all operating phases, such as unit start-up, shutdown, parallel operation, Island mode, and so on, the TCS system assures stable operation. Full load rejections caused by a sudden separation from the grid are regulated by the TCS in generation applications, preventing an over-speed condition and collateral damage.
The principal features of the TCS system are summarized as follows:-

1. Speed Control
2. Inlet/Admission Pressure Control-two channel selection that facilitates initial pressure and limits pressure functions
3. Load Control-via either a load setpoint command from the Control System, or can be configured to receive MW input for utilization of the load control function developed within the system, or can be configured stand-alone as an MW or Speed Droop function.
4. Turbine Stress Influence
5. Frequency Influence
6. Valve Lift Control

The brain of the steam turbine controller should be a high-speed digital processor. The TCS should provide automatic and manual shutdown. In automatic shutdown, the system must lower the load until the generator breaker opens on reverse current. On manual shutdown, the operator will open the generator breaker manually once the turbine is at minimum load.

Normally, Steam Turbine speed is reduced to 1500 rpm to generate power by Alternator by using a Gear Box in between if the frequency is 50 Hz and 1800 rom if it is 60 Hz. For speed reduction purposes a gearbox system is followed by lubrication system which demands maintenance as well.

In case the power generation potential is up to or around 400 kW an Induction Generator instead of an Alternator can be used to generate power. For this the Turbines are designed to operate at 3025 or 3600 rpm based on the generation frequency required as 50 Hz or 60 Hz respectively. Such a Turbine is directly coupled to the Induction Generator without using the gearbox in between. This makes the system very simple in construction and operation as well.

An Induction Generator requires 2-3 times starting current for less than 3 seconds. Thus it is important to take this into consideration while deciding to use an Induction Generator.

Turtle Turbines has many successful installations in various industries with Induction Generator.