• What is the concept of cogeneration using steam?
• How does it save money?
• What are the areas of application of cogeneration?
• Will we stay connected to utility?
• How short is the payback period?
• Is it possible to use existing boiler?
• What is the effect of cogeneration on our fuel use?
• What are the benefits of cogeneration?
• Is this equipment easy to maintain?
• How old is the cogeneration concept?
• What is the future of the cogeneration?
• What do utilities have to say about cogeneration?
• What is a cost per unit?
• Steam Turbine Co-generation Systems: Synchronous vs Induction?
• Electrical Considerations?
• Transition Between Paralleling and Standalone Operation?

Cogeneration is the simultaneous production of electricity and useful thermal energy.  This means that you can generate electricity with the same steam you are now using for heating or process. You can use the same steam twice. In modern usage, cogeneration has also come to mean using waste fuel for in-plant electricity generation. Many companies produce steam for process needs at a higher pressure than it is ultimately used at. This steam is usually passed through a pressure-reducing valve, which lowers its pressure and increases its temperature. A steam turbine can take that same energy available when pressure is reduced, and turn it into valuable electricity. Steam turbine generators make electricity by converting a steam pressure drop into mechanical power. High-pressure steam enters the turbine, drives the generator and exhausts at a lower pressure for use in plant heating or process. A turbine does not consume steam; it only reduces its pressure.

Cogeneration saves money by allowing you to produce your own electricity for a fraction of the cost of utility power.  Cogenerated power is cheaper because cogeneration systems can achieve fuel efficiencies of up to 80%, whereas the best utilities can do is about 40%. 

Any company with a significant process steam use or surplus waste fuel.  Many companies are unaware of their great cogeneration potential.  Cogeneration systems can be designed into new boiler plants or can be easily added to existing boilers.  See our installation list.

It varies with the nature of the project, but it's often between one to three years.  Payback is a function of power, system price, and average steam cost.  The higher your current electric rates, the shorter be the your payback period.  Also, since equipment price per kW declines as power increases, higher the power, and the more cost effective the system

Your existing boiler can be used to make the steam for cogeneration if it is operated at 100 psig or greater.  There are even some cases where low pressure (e.g. 15 psig) boilers can be used.

The amount of fuel used depends upon the system design.  The Backpressure turbine generator sets from ANAMA, for example, are ideal for use with oil or gas boilers and increase fuel use by only a few percent.  On the other hand, if you have a waste fuel such as wood waste, a condensing turbine such as our Condensing turbine generator allows you to burn that fuel to make even more power.

Cogeneration is highly beneficial as it allows you to produce the power from things, which are normally wasted. Also the cost of power produced from cogeneration is very low compare to grid power cost. For companies using waste fuel, elimination of waste disposal costs can be a very important benefit.  Depending upon design, a cogeneration system can provide emergency standby power and can smooth out boiler load swings power.

Yes.  Steam turbines have a 20-year minimum service life; and the single stage turbines are designed for 3 years of continuous duty at full load without shutdown for maintenance.  The generator features a 20-year minimum service life, bearing life up to 100,000 hours, low vibration levels, and a premium insulation system.

No. It's been done since the beginning of the electrification of industrial America.  Originally, most electric power was co generated by individual manufacturers, not the utilities.  In the 1920's and 30's, as cheaper utility electricity became available, cogeneration waned.  With cheap oil available, power rates continued to decline through the 1950's and 1960's.  Then came the 1973-74 Arab Oil embargo. Everything changed abruptly.  Since then, electricity prices have risen.   Further upward pressure was produced by some utilities' nuclear power plant building programs.  Now many companies are getting back to their original source of power:  cogeneration.

Cogeneration systems are of very bright future. As grid power rates increase, there will more and more companies are adding cogeneration systems to their power plants.

In general they are very cooperative.  Their primary concern is making sure the cogeneration system is properly designed so as to not affect their distribution system or their other customers.  Steam turbine cogeneration systems from ANAMA feature full electric protection standards for systems of their size.

Steam turbine cogeneration system is the most efficient way of generating the electricity ever invented. The per unit cost of the power produced from the cogeneration is the cost of the energy, which is taken out of the steam by the turbine generator system which is then converted into electricity. Generally it varies with the nature of project. The power produced from the backpressure steam turbines is virtually free of cost. In condensing steam turbines cost of producing the electricity is directly depends on the average cost of steam production, that is in turn depends on the cost of fuel used for steam production.

Steam turbine cogeneration is a well-proven, viable energy conservation technology. Industry is now using hundreds, perhaps thousands of steam pressure-reducing valves that could be replaced with turbines. The current availability of packaged turbine generator system with Anama Energies can makes them easy to implement. They can be used to replace the pressure reducing valves in application with steam flow as low as one ton per hour also.

One of the most basic decisions to be made in designing a steam turbine cogeneration system is whether the generator and its associated controls will be induction or synchronous. Generators are available in two designs: Induction & Synchronous. These two types differ in how they are excited.

Induction :
An induction generator is essentially induction motor rotated above the synchronous speed by the turbine. It receives its excitation from the utility and has no means of producing voltage until it is connected to the utility. Therefore, the frequency and voltage of the power produced with this type of generator is governed by the frequency and voltage of the incoming utility line. If the utility system fails, an induction generator cannot operate.

Synchronous :
Synchronous generator has its own exciter that enables the generator to produce its own reactive power and regulate its voltage, even when it is not connected to another power source. This means that it can operate either in parallel with the utility or in "stand-alone" mode (independent of any other power source). So synchronous generator system can be used as emergency backup generator. Another advantage of a synchronous generator is that, since it creates reactive power, it can improve the plant power factor.

In small steam turbine cogeneration systems, the generator system is usually interconnected with the plant electrical system so that both utility & cogeneration system simultaneously feed the complete plant load. As the turbine produces more power, less is purchased from utility. This is in contrast to stand-alone systems, where the generator is tied to specific electrical loads that are isolated from the utility.

Parallel operation of the generator allows turbine output to be controlled by the steam demand rather than being limited by the demand of a particular load. This maximizes the turbine operating efficiency & increases the total power output. Another advantage of parallel operation is that can be tied into the plant electrical system at any point where there is a sufficient conductor capacity. It is not necessary to bring the generator output back to the main service entrance. The generator can be interconnected at any nearby distribution panel. Parallel operation of the generator provides greater security, since the utility is instantaneously available to meet all electrical loads if the cogeneration system should go off-line.

If the generator will not be interconnected with a utility or other power source you must use a synchronous generator. The steam flow through the turbine will be controlled by the demand for electricity, & not the demand for low-pressure steam. As a result, in cases where the low-pressure turbine exhaust steam will be used for process, the steam piping must be specially designed to include a controlled bypass (PRV), and low-pressure vent valve or condenser.

Many systems are operated in both parallel and stand-alone mode. During normal operation the system is run in parallel with the utility, and during utility power outages it is operated in stand-alone mode. A utility tiebreaker must be present to separate the generator and the emergency loads from the utility during power outages. Once utility power is restored the generator is re-synchronized with the utility across the tiebreaker, either manually or automatically. These systems need a bypass PRV, and a low-pressure condenser or vent valve to balance the steam to the system during stand-alone operation.

When the utility power fails, a turbine-driven synchronous generator can provide emergency back-up power. The plant as a whole, however, must be prepared to coordinate with the turbine generator in providing that power. For instance, provisions must be made for maintenance of sufficient steam supply. Unless the generator capacity is great enough for the full plant, non-critical loads must be shed, since the plant’s electrical load, (including starting KVA), cannot exceed the capacity of the generator(s) providing that power. The generator and critical loads must be isolated from the dead utility line, and the generator must be re-synchronized with the utility when it returns.

It is important to understand that when the turbine generator is the primary source of power, it is controlled by electrical load, rather than steam load, as is otherwise the case. This means that as the plant requires more or less electricity, the turbine will use more or less steam. If the steam used for electricity exceeds the plant’s process steam requirements, the excess steam must be vented or sent to a condenser. For the case when the process requires more steam than the turbine, a by-pass pressure-reducing valve is needed to send steam around the turbine to the process.

Perhaps the most intricate aspect of running stand-alone is the transition from paralleling to stand-alone and back again. A variety of schemes are possible, two of which are outlined below.

Black Transition Scheme
The simplest scheme involves allowing the turbine generator to go down when the utility power is lost. Any sheddable electrical loads are turned off, leaving only loads within the turbine generator’s capacity. A source of power, typically a diesel generator, is then used to power the boiler. The turbine generator is then synchronized with the diesel generator. The diesel can be shut down or left running. When the utility comes back on line, the entire system may need to be brought down again. In this case utility power is used to power the boiler, and the turbine generator is restarted and then synchronized with the utility. Figure 1 shows a system that can make a black transition

Ride-through Capability
In order to "ride through" a utility power loss, some additional components are required. The plant entrance must have an automatic utility tie-breaker and associated protective relays, as shown schematically in figure 2. When utility power is lost the utility tiebreaker opens and isolates the generator and the emergency loads from the utility.

The system for detecting a loss of utility power must be carefully designed for each application. In some cases this must take the form of a telemetry signal from the utility. In some cases it is possible use the reverse power relay, the frequency relay, and/or the over current relay at the plant entrance to detect the utility outage. The protective relays at the entrance and at the generator must be coordinated so that the utility tiebreaker opens before the generator breaker.

In addition to opening the tiebreaker, the controls must also simultaneously switch the turbine to follow the electrical load and maintain the proper electrical frequency. If required, non-critical loads must be shed instantaneously. In some plants, an automatic load control system is needed to shut down sheddable loads, to bring the electrical load to within the generator capacity.

Finally, when utility power returns, the generator must be synchronized with the utility across the utility tiebreaker, whereas under normal start-up conditions, the generator is synchronized across the generator circuit breaker. The synchronizing equipment can be designed to accommodate both situations.

If a turbine generator system is intended to provide emergency power during utility outages, special attention must be paid to the needs and functions of the plant. Anama Energies can provide your plant with a customized control system to meet your stand-alone needs. We will work with you to design a control system to optimize the utilization and reliability of your equipment.