POWER-GEN Russia 2015 Moscow, Russia 3 - 5 March 2015

Copyright © 2015 AZG Consulting GmbH

Efficient CHP Plant Concepts with High Operating Flexibility

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Efficient CHP Plant Concepts with High Operating Flexibility

Presented at Power-Gen Russia, Moscow, March 2015

Authors: Marina Darozhka, Frank Rossig, Nicholas Bellamy,

SSS Gears Ltd./AZG Consulting GmbH

CHP is one of the world’s most efficient energy technologies with overall efficiency of

up to 80% or more. Numerous successful installations are operating throughout the

world and are proving its reliability, as well as the reduction of energy cost and

greenhouse emissions.

1. General introduction.

Combined Heat and Power (CHP) is a very general term covering various

technologies and applications. Technologies can be distinguished based on the

prime mover, which can be reciprocation engine, fuel cells, microturbine, gas turbine

or steam turbine with boiler. Gas turbine and steam turbine driven technologies are

making up to nearly 90 percent of the complete CHP generated capacity worldwide.

These two technologies will be in focus of this paper.

Fig.1 – CHP Efficiency Advantages [1]

Thinking on operation systems of Combined Heat and Power plants, it can be

distinguished between:

- Toppingcycle, where electricity is produced utilizing high temperature and pressure

steam energy, and the waste heat is used for thermal energy generation purposes;

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- Bottomingcycle, where the energy source is used in the first line to supply a high

temperature thermal energy, and the excessive or waste heat energy is used for

electricity production.

Gas turbines for CHP plants can be used in a variety of configurations, whereas the

thermal energy from the exhaust heat is a byproduct from electrical power

generation:

- Simple cycle operations with CHP, where fuel is combusted in the gas turbine

and the exhaust gases are led to the heat recovery steam generator to produce

useful thermal energy, or the exhaust gases are used directly in some process

applications;

- Combined-cycle operations, where the high pressure steam is generated from the

gas turbine exhaust within the heat recovery steam generator and used for driving a

steam turbine to generate additional electrical power. Lower pressure steam can be

extracted from the steam turbine and used directly in a process or for district heating,

or can be converted to other forms of thermal energy including hot or chilled water.

Steam turbines within the CHP plants often generate electricity as a byproduct of

heat and steam generation. Steam turbines do not directly convert fuel to electric

energy but operate on the high pressure steam generated within the steam

generators such as boilers. Steam turbine driven CHP plants can operate on a vast

variety of fuels, like natural gas, solid waste, all types of coal, wood, wood waste and

agricultural byproducts.

Depending on the desired plant performance and specification a variety of steam

turbine designs can be used. Basically it can be distinguished between following

steam turbine types:

- Backpressure steam turbines with the fixed pressure ratio, the power generation

capability of those depends on the steam flow. Should the heat production drop, the

power generation will be also reduced;

- Condensing steam turbines expand the pressurized steam down to well below

atmospheric pressure, at which point steam is exhausted to a condenser at vacuum

conditions;

- Condensing turbines with extraction options. In these turbines portion of steam

can be extracted at an intermediate or low pressure level in order to supply steam at

certain pressures and temperatures for process and district heating.

Steam turbines may have one or several pressure casings, and the design has to be

chosen based on efficiency and flexibility optimization of the power plant.

Nowadays the demand for electrical power is rarely constant and generating plants

may have to operate at reduced power for significant periods. Power plant designed

primarily for power generation can, however, be a valuable energy source for other

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consumers. Processes and heating systems can use steam available from

periodically under-loaded power plants. Also the demand for steam can be as

variable as the demand for electrical power. A Combined Heat and Power plant

should, therefore, be capable of easily accommodating daily or seasonal changes in

demand for both heat and power.

A Combined Heat and Power Plant designed to operate with maximum flexibility

could incorporate a connectable and disconnectable device between the low

pressure and high pressure turbine cylinders. At times of reduced electrical demand,

the steam exhausting from the high pressure turbine is diverted for other uses and

the low pressure turbine cylinder is disconnected. When full electrical output is

demanded, steam flow to the low pressure turbine cylinder is restored and the turbine

is automatically reconnected to drive the generator. Such a system has cost

advantages over a plant comprising two separate turbines each driving its own

generator. The key element in such system is a reliable device for disengaging and

re-engaging the low pressure turbine cylinder.

The same principle can be applicable for CHP systems with several single casing

steam turbines each driving a single generator.

2. CHP applications.

When considering diverse CHP applications, the combination of following categories

can be used:

- District heating and cooling;

- Process heat and steam supply;

- Electricity supply to buildings and districts.

Fig.2 – Typical CHP Process Steam / District Heating Schematic Drawing

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2.1 District Heating and Cooling.

Space heating of buildings is a popular use for CHP heat. Homes, offices and leisure

and shopping complexes are all consumers. District heating grids are particularly

popular in developed countries with generally low ambient temperatures especially

when building developments mix residential, retail and leisure construction close to

industrialised zones.

As well as heating applications, CHP heat may also be used for cooling applications.

In this case, the heat is used to induce flash evaporation of a working fluid to its

saturation point. The evaporation of course causes auto-refrigeration, thus cooling

the working fluid, which may then form part of a cooling grid.

District heating and cooling are generally “groundwork up” solutions, where the

building developer considers a complete building and energy supply solution, as

opposed to building only. Consequently, district heating and cooling examples are

most common in expanding areas which already have district heating available.

As the heat consumed in district heating and cooling cycles is generally at a lower

temperature and pressure than that used for process applications, larger quantities of

the plant waste heat can be used and therefore higher efficiencies are achieved.

District heating demand can fluctuate seasonally.

2.2 Process Heat and Steam.

Industry consumes large amounts of heat. This heat consumption is not only limited

to space heating requirements of offices and factories, but also industrial processes.

Industrial process applications include paper production, sugar refining, drying (e.g.

paint and processed chemicals) chemical and petrochemical engineering applications

(e.g. steam turbine driven machines) and sterilizing and cleaning equipment.

Unlike district heating, whose demand will typically fluctuate with seasonal weather

patterns, process steam requirements tend to have predictable demand. However,

agriculturally dependent industrial processes (e.g. sugar refining) can yield seasonal

demands consistent with crop cycles, especially where processing is geographically

close to the source material growth.

This shows that Combined Heat and Power plants might contribute to improving

energy efficiency in situations where the alternative production is represented by

conventional thermal power plants.

3. SSS Clutches as a device to connect and disconnect steam turbines.

Arrangements with automatic main drive synchronising self-shifting clutches to

connect and disconnect different drivers have been successfully applied worldwide

for more than 60 years. These automatic SSS Clutches have proven to be extremely

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reliable throughout the lifetime of the power plant even with daily connection and

disconnection of the driver. When installed on CHP plants, SSS Clutches disconnect

steam turbines or its cylinders from the generator train whenever the steam from the

steam generator is needed for district heating or process steam applications. When

additional electrical power generation is needed, the SSS Clutch will automatically re-

connect the steam turbine to the generator without disturbing the electrical power

generation from the main drive.

During the shut-down sequences of the turbine the SSS Clutch disengages

automatically, leaving the generator rotating being driven by the remaining driving

machine - gas turbine or steam turbine.

The SSS Clutch is a bespoke freewheel mechanism, which automatically engages

and disengages through shaft speed control only. SSS Clutches in operation range in

power from a few kW up to 320 MW and from operation speeds between 1 rpm to

16000 rpm.

When the SSS Clutch input speed attempts to rotate faster than that of the output

side, a pawl and ratchet mechanism synchronises the main clutch driving teeth into

alignment so that the helical splines will shift the main clutch driving teeth

automatically into mesh, thus engaging the clutch. When the input side slows down

relative to the output side, the main driving teeth are automatically moved out of

mesh, thus disengaging the SSS Clutch.

Fig.3 – SSS Clutch Operating Principle

Clever use of internal oil distribution and centrifugal force prevent metal to metal

contact when the clutch is overrunning. Engagement and disengagement are

cushioned by an internal dashpot action where required, and the main driving teeth

are designed with conservative loading. These steps prolong clutch life, therefore

under normal operation an SSS Clutch will outlive the life of the plant main

machinery.

A – Pawl

B – Main driving teeth

C – Helical Sliding Component

D – Helical Spline

E – Input Component

F – Output Component

G – Ratchet Teeth

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There are different designs of SSS Clutches available:

- Semi-rigid SSS Clutches:

These clutches can be used within the installations

where alignment is closely controlled. For example,

the clutches can be mounted within the steam

turbine bearing pedestal or inside a gearbox. This

type of clutches can be in-line or quill-shaft mounted.

The semi-rigid SSS Clutch design accepts small

angular and axial expansion movements of the

adjacent machine shafts to compensate for thermal

growth requirements.

For the semi-rigid SSS Clutch designs, when engaged and transmitting torque, the

clutch should be considered as a solid shaft.

- Spacer type SSS Clutches:

These clutches are suitable to be installed

between shafts subject to misalignment. These

clutches have a double set of teeth and act as a

flexible coupling. Also these clutches can

accommodate large axial expansions if

necessary.

- Encased SSS Clutch packages:

These clutches are supplied as self-

supporting units within the casings. The

package includes an input and output shaft,

each supported and located by combined

white metal journal / thrust casing bearings.

The input and output shafts support the

overhung mass of the clutch input and

output sub-assemblies respectively. Although the 4 bearing Encased SSS Clutch

design extends the train length when compared with a solution incorporated within

the turbine pedestals, standardized steam turbine designs can be used thus greatly

reducing design time and cost. Therefore, in return this concept offers reduced

engineering input and therefore total installation costs and realization time for the

customized CHP plant application.

Alternatively, Encased SSS Clutch packages can be designed self-lubricated with

ball bearings.

- SSS Clutch couplings:

This clutch design can accept radial misalignment and axial growth between each

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Fig.4– Fredrikstad Bio-El CHP Power plant Photo courtesy of Hafslund

steam turbine and the generator through

two single element flexible membranes,

one at each end. Two ball bearings are

located on the clutch input shaft, which in

turn support the clutch output assembly.

This SSS Clutch Coupling design is

therefore shaft mounted, self supporting

and includes seals to contain an integral, self-lubricating oil supply which removes

the need for any pressurized oil supply to the SSS Clutch or any additional oil tight

casing.

4. CHP Experience with disconnectable steam turbines.

Steam consumption can often vary depending on seasonal, industrial and agricultural

demands. These demand fluctuations create a challenge for CHP station designers

who must satisfy varying heat, electrical power and process steam demands. In

addition to achieving high plant efficiency, short payback periods and limited

installation costs, the solution may also require significant operational flexibility to

cope with these fluctuating demands.

The following examples describe seven CHP facilities ranging low and high powers,

where total operational flexibility and high efficiency were prime concerns for the

designer.

4.1 Bottomingcycle.

As described in Chapter 1, in so called bottoming cycle the CHP plant primary goal is

to produce the heat energy. Power generation is possible as utilization of the

excessive heat or industrial steam.

4.1.1 Waste to power: Fredrikstad Bio-El CHP Plant, Norway.

The city of Fredrikstad is situated in the south-west of Norway close to the Swedish

border and is having nearly 78000 inhabitants. The Fredrikstad CHP plant

commissioned in 2008 has a thermal generation capacity of 25 MW and is fired on

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homogenous, sorted waste, of which 80% origin from the industry and 20% is

municipality waste [2]. Each year the plant recycles energy from around 45000 to

60000 tonnes of waste-based fuel. This results in an annual supply of 110 GWh of

industrial steam to industrial customers in Øra and district heating to Fredrikstad,

together with some electricity generation.

The plant has a main goal to deliver heat to a district heating network and process

steam. Electricity generation is a byproduct. The operational strategy is influenced by

district heating demand, process steam demand and electricity prices.

The facility consists of a 25 MW steam boiler, one generator of 5,68 MW, one back

pressure turbine and one condensing turbine. The turbines are connected to the

generator as shown on the picture. The back pressure steam turbine is a Dresser

Rand B5S-5 is solidly coupled with the generator and the condensing steam turbine

is a Dresser Rand B7S-3 connected to the generator through the Size 92FT Spacer

SSS Clutch. This allows the plant to be operated with or without condensing steam

turbine.

During winter periods the plant has to produce high amount of process and district

heat, therefore the condensing turbine is stopped and the low pressure steam is led

to the heating grid. In summer this excessive heat is not required, therefore the

condensing LP turbine can be connected to the generator in order to produce

additional electricity.

The supply temperature of the district heating water varies between 120 and 90 °C

according to outdoor temperature, usually not above 115°C. The return temperature

varies between 60 and 80 °C.

The production in 2010 was 53 GWh of district heating, 49,8 GWh of steam and 14,2

GWh of electricity. Total energy recovery rate is 70,1%. This relatively low energy

recovery rate is caused by the plant operating based on the certain amount of

incoming waste and the demand for heat or electricity. During low heat demand

seasons not all the excessive heat can be utilized for electric power generation and

thus needs to be cooled, which results in the reduced total energy recovery rate [3].

For this application a size 92FT Spacer SSS Clutch of a spacer type was chosen.

This clutch can accommodate some radial misalignment and has a relatively small

installation length and light weight which has to be supported by the shafts of the

adjacent machines.

4.1.2 Natural Gas fired CHP plant Plauen, Germany.

The city of Plauen is located in central east part of Germany, in Saxony, inhabited by

approximately 68,000 people. The city is supplied with heat via 50 km of district

heating pipes to 13,400 private households. Other consumers include the City’s

hospital, administration offices, and large industrial facilities including Plauen Steel

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Steam - 60 t/h to grid - 5,7 Bar pressure to grid - 240°C to grid

Electricity - 1 MWe Backpressure turbine - 0,32 MWe Backpressure turbine - 1500 rpm generator

Technology, WeMa Vogtland (instrument machines plant) and Schneider Textile

Coloration and Finishing. The power plant was originally built in 1988 as coal fired

power plant. In 1994 the plant was upgraded to operate on natural gas (or on light oil

as a reserve). Heat generators are 4 boilers with total power of 28 MW. The complete

power plant is supplying up to 150 MWth to the grid. One of the features of the district

heat grid is that it has more than 90m of altitude differences [4].

In year 2000 the owner decided to upgrade a plant with a steam turbine which could

utilize the existing differences between the fresh steam conditions from the boilers

and the steam conditioned required for district heat to generate electricity for the own

needs of the plant.

Today two backpressure steam turbines drive one common generator at Plauen

within the Hammerstrasse plant. Both turbines are Kühnle, Kopp & Kausch (now

Siemens Frankenthal) back pressure turbines. The AFA4 steam turbine can produce

0.32 MWe, whereas the AFA6 machine can provide 1.0 MWe via a 1500 rpm

generator.

Fig.5 –CHP Plant Hammerstraase Plauen (Germany) Photo courtesy of Siemens Frankenthal

The ST tandem train can generate between 50 kW and 1300 kW of electricity,

depending on the requirements of the grid in heat. I.e. the more steam is generated

for the grid, the more electricity can be produced.

The maximal total amount of fresh steam is 60t/h, and if the grid demand is smaller,

the not required turbine can be stopped. Ca. 6 t/h are already sufficient to drive one

of the turbines and to generate 50kW or more of electricity. So, depending on

winter/summer operation mode, the plant can operate larger or smaller turbine, or

both.

Splitting the steam turbine demand either side of one generator, with an SSS Clutch

connecting or disconnecting each turbine as required, allows a wide range of CHP

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operating modes which promotes higher operational flexibility with regards to

seasonal changing district heat requirements.

One major consideration of the turbine packager was to keep the design of the steam

turbines standard. The SSS Clutch design chosen was an “off the shelf” unit, an SSS

Clutch Coupling, which can accept radial misalignment and axial growth between

each steam turbine and the generator through two single element flexible

membranes, one at each clutch end. Two ball bearings are located on the clutch

input shaft, which in turn support the clutch output assembly.

4.2 Toppingcycle.

In topping cycle, as described above, electricity is produced utilizing high temperature

and pressure energy, and the waste heat is used for thermal energy generation

purposes.

4.2.1 Vuosaari ‘B’, Finland: a multishaft CCGT plant with high operation

flexibility.

Finland is a world leader in CHP. In 2007, 65% of Finland’s thermal electricity

production, 74% of the heat needed for district heating and 29% of the Finnish

electricity supply was provided by CHP. In 2004, CHP saved Finland 8 million tonnes

of carbon dioxide emissions [1].

Vuosaari is a district of Eastern Helsinki in Finland noted for its rapid residential

growth, although also renowned for retaining large areas of unspoilt landscape with a

population of approximately 35000 people. District heating is particularly popular and

well established in Helsinki providing approximately 90% of the city’s heating needs.

Fig.6– Helsingin Energia / Siemens Finspäng, Vuosaari ‘B’ (Finland) CHP Plant Schematic Drawing

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Helsingin Energia, winner of a European Regional Energy Champion Award from the

European Parliament in November 2008, owns and operates the Vuosaari ‘B’ CHP

plant. Vuosaari ‘B’ provides up to 470 MWe of electricity and 400 MWth of district

heat from a multi-shaft combined cycle plant incorporating 2 x Siemens V94.3 gas

turbines (rated 163 MWe each) and an ABB Stal (now Siemens Finspäng) steam

turbine train (rated 172 MWe).The challenge of providing both peak district heating

demand and peak electricity demand can be fulfilled by Vuosaari ‘B’ concurrently.

This feat is possible because a hot water accumulating tower has been included. The

tower can store up to 25000 m3 of hot water just below 100°C which equates to

around 1400 MWth of energy [5].

The basic principle behind CHP with a hot water accumulator is simple and similar to

that of a domestic heating supply utilizing off-peak electricity to store heat overnight.

When peak electricity is not required, the LP steam turbine is shut down, allowing

100% of the LP steam to be used to heat water, which is stored in the hot water

accumulator.

Shutting down the LP turbine in this case is only possible because of the SSS clutch

located between the LP and IP sections of the ABB Stal steam turbine train, which

drives one common generator. Even when district heating and peak electricity

requirements coincide, the station is capable of fulfilling both demands. The heat

energy is already stored and available for supply, whereas the LP turbine can be

restarted to produce peak electricity as the SSS clutch automatically re-engages.

Consequently, the generating process of the plant is not interrupted whilst the LP is

reconnected through the clutch to the generator system.

During warmer periods, when district heating is required less, or not at all, the LP

turbine is automatically connected to the generator by the SSS Clutch to produce

maximum electricity.

In this case, an SSS Spacer Clutch type was supplied, which in addition to the

normal automated engaging and disengaging mechanism features two sets of torque

transmitting gear teeth allowing the clutch to take up radial and axial misalignment.

This capability allows the SSS Clutch to absorb the thermal growth of the LP and

HP/IP steam turbines, similar to the function of a geared, spacer type flexible

coupling.

To summarise, Vuosaari “B” provides peak and base load electrical power, district

heat requirements and offers flexible operation from a plant which has a 92%

maximum design efficiency. These features make Vuosaari ‘B’ one of the most

versatile CHP plants in the world and an excellent example of total plant flexibility.

4.2.2 MHI / KDHC Hwaseong, South Korea.

Many CHP plants exist in Scandinavia, in particular Finland. Cold winters and

existing CHP infrastructure make this area ideal for CHP expansion. However, other

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Steam - 472,1 t/h to grid - 410 MWth power heat - 4,6 Bar pressure to grid - 292°C to grid

ST Electricity - 425 MWe HP turbine power - 97,4 MWe LP turbine power - 3600 rpm generator

countries are also well versed with CHP. In fact, 60% of South Korea’s households

are supplied with heating energy by Korea District Heating Company (KDHC) through

a network of 1164 km of twin row pipes. In 2006, CHP saved South Korea 2644

tonnes of air pollutants and 1739 tonnes of greenhouse when compared with

conventional heating alternatives [6].

Hwaseong City is situated in the south west corner of the Gyeonggi-do province,

approximately 40 km south west of Seoul. Large local companies include Kia and

Hyundai cars and Samsung Semiconductor. Geographic location, shallow coastal

water levels and exposure to Siberian air streams give rise to low winter

temperatures.

Fig.7 – KDHC / MHI Hwaseong (Korea) CHP Plant, Photograph courtesy of MHI

KDHC own and operate a CHP power plant in Hwaseong City which consists of 2 x

MHI MW501F gas turbines supplying exhaust heat through an HRSG to an MHI

steam turbine train consisting of 425 MWe HP and a clutched 97,4 MWe dual flow LP

steam turbine arrangement.

As well as supplying up to 522 MWe (rated) of electricity to Korea Electric Power

Corporation, the steam section of the plant provides up to 410 MWth in hot water and

domestic heating requirements to approximately 51000 households

The clutched LP turbine allows Hwaseong power plant to choose between supplying

steam for district heating or generating extra electricity, all from one steam turbine

train.

Some may argue that the SSS Clutch may be replaced with a generic spacer

coupling which is disconnected when district heat is required. However, a clutched

LP turbine provides several advantages:

- Instantly flexible to accommodate daily changes in weather patterns;

- Possibility for instant LP turbine disconnection in case of trip/failure etc.;

- Automated and therefore:

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- No requirements to interrupt generation during disconnection or

reconnection of LP turbine;

- No risk of damage to equipment during coupling removal;

- No intensive labour required.

MHI selected a “between pedestal bearings” positioning of the SSS Clutch to provide

adequate support for the SSS Clutch which behaves like two separate overhung

masses when operating in the disengaged condition.

This particular semi rigid SSS Clutch includes a Lock-In facility to assist with dual

(HP+LP) turbines starting mode. Normally, when starting the HP and LP turbines

simultaneously, the LP turbine speed lags behind that of the HP section. This occurs

because the LP machine is much heavier and therefore slower to accelerate, so the

SSS Clutch would normally disengage. To avoid this condition, this SSS Clutch can

be locked into engagement before starting and accelerated to nominal speed without

LP turbine disconnection occurring.

Fig.8 – HP + LP Startup Graphs with and without SSS Clutch Lock-In

Once at full speed, the SSS Clutch Lock-In is deactivated to allow automatic LP

turbine disconnection and subsequent reconnection as required.

4.2.3 KauVo, Lappeenranta, Finland.

Both examples cited above in section 4.2.1 and 4.2.2 include large steam turbines

fired by the exhaust heat from gas turbines. Plants in toppingcycle fired by the heat

from combusted waste products also exist. The following example is fired entirely

with byproducts of the wood and paper industry - bark, residual peat, wood

stampings and chippings.

Electricity consumption in Finland is increasing and some existing plants are being

decommissioned. Also, neighboring Sweden produces half its electricity from nuclear

plant, some of which are more than 30 years old. If Swedish nuclear plants are

decommissioned, opportunities will arise for Finland to export electricity across the

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Steam - 295 m

3 paper mill

- 385 MW Total power: 110 MWth district heat 150 MWth process steam 125 MWe electrical power -- 16,5 + 12 + 4,5 Bar pressure to paper mill - 547°C to paper mill

Electricity - 95+30 MWe condensing turbine power - 20 MWe Backpressure turbine power - 3000 rpm generator

border into Sweden.

This potential is giving current electrical generation facilities more scope for

expanding their capabilities. KauVo is one such expansion.

Lappeenranta is a city of approximately 60000 inhabitants in South-East Finland,

about 30 kilometres away from the Russian border. The local economy is mainly

industrial including paper mills owned by UPM, city facilities and a local university

which specialises in forest and energy technology.

Kaukas is one of the many paper and sawmills owned and operated by UPM, who

are also operating CHP power plant at Kaukaan Voima or “KauVo”.

The plant rotating machinery consists of two steam turbines separated by an SSS

Clutch. One steam turbine is a condensing machine, the other a heating turbine and

both drive one common generator through one single shaft line.

The machine supplies up to 295 m3 max of steam at 547°C to the paper mill at 3

pressures: 16.5, 12 and 4.5 Bar. Total power output for the plant is 385 MW, which

can be broken down to 110 MWth district heat, 150 MWth process steam and 125

MWe generator output.

Fig.9 – UPM Lappreenranta “KauVo” (Finland) / Siemens Goerlitz CHP Plant, 3D drawing courtesy of Siemens

All the desired flexibility is available at this plant, again due to a clutched turbine,

which in this case is a double flow heating turbine. The heating turbine should run for

approximately 8000 hours per annum. As the heating turbine is connected and

disconnected through an SSS Clutch, the system can cope almost instantly with any

changes in the predicted operation hours, promoting further plant flexibility.

Of course, 8000 hours equates to almost 1 constant year running, so it is important to

define that a major factor for including an SSS Clutch at this plant was the added

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benefit of being able to service the heating turbine whilst the condensing turbine

continues running.

The condensing turbine is fitted with a switchable condensing section which allows

the choice of operation as a non condensing turbine at 95 MWe with 30 MWth

passing to the steam supply route or as a 125 MWe full condensing turbine. The

condensing turbine steam supply pressure is 112 Bar.

This plant shows another SSS Clutch design configuration for CHP plant with the

integration of a 4 bearing Encased SSS Clutch package. Because of this particular

clutch package, as described above, standardised steam turbine designs were used

which was greatly reducing design time and cost. This concept offers reduced

engineering input and therefore total installation costs and realisation time for the

customised CHP plant application.

4.2.4 Köln Nieh 3 Combined cycle gas turbine plant KA26-1 SS DH Ecoheat ™.

Köln Niehl 3 power plant is planned for commissioning in 2016 and is situated in the

city of Cologne, Germany and is going to operate by German energy supplier

RheinEnergie. The power plant should produce 453 MWe and around 265 MWth and

supply up to one million households with electricity and 50000 households with

district heat [7].

Fig.10 – Köln Niehl 3 construction site and schematic machinery arrangement, Photograph courtesy of Alstom

The power plant is being build straight next to the operating Niehl 2 power plant

within the densely packed area. One of the challenges for designers were limited

road access and space available for construction of the new power plant. This was

one of the reasons why a single shaft CCGT plant concept, where the gas turbine

and the steam turbine are driving the same generator, was chosen.

Electrical efficiency of the power plant is projected to be over 60% which will make it

one of the most efficient nowadays working power plants. Total fuel utilization rate of

the plant will be over 88% due to its district heat integration.

The power plant consists of one Alstom GT26 gas turbine, one hydrogen cooled

TOPGAS generator and a compact three casing STF30C reheat steam turbine

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connected to the shaft train via a Size 340T SSS Clutch.

During the summer periods the plant is going to operate in the condensing mode

providing full power generation to the electrical grid. During winters the plant will

operate in heating mode for maximal heat production to the district heating grid. In

this operation mode a maximal steam extraction from the three-casing ST is required.

In order to minimize ventilation losses for this operation regime, the double flow LP

section was optimized for very low steam flow and pressures. It is also possible to

operate the plant in simple cycle GT mode only.

This high operational flexibility, fast start up and high efficiency is feasible because of

the SSS Clutch connecting and disconnecting the ST during the plant start up and

changing operation modes. This semi-rigid SSS Clutch design of the size 340T is

installed within the ST bearing pedestal ensuring the shortest possible machinery

train length.

4.2.5 Concept: Single shaft CCGT power plant PGU-165 with Saturn (Russia)

GT-110.

Fig.11– Saturn PGU 165 plant arrangement, drawing courtesy of Saturn, ODK

Russian GT manufacturers haven’t practically realized the single shaft combined

cycle concepts yet. The largest gas turbine which is manufactured in Russia by

Saturn (part of ODK) is the GT-110. This gas turbine is being supplied as a simple

cycle package together with a 110 MW generator.

Russia is well known for a large district heating network and thus for vast demand of

thermal energy supply. Additionally, the average age of the electricity generating

plants in Russia is still very high and the main focus of the authorities for generation

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capacities replacement are the combined-cycle power plants fired by natural gas.

Saturn has fulfilled a large concept work to design a modern modular CCGT power

plant of a single shaft design. The new package is meant to be flexible in terms of

choice variety of steam turbines and includes the GT-110 gas turbine solidly coupled

with the new design hydrogen cooled generator ТТК-165-2УЗ-ГП (165MW) and pre-

planned Skoda 55MW MTD40SA steam turbine [8].

This new power plant can be operated in base load supplying the total electrical

power generation capacity of 165MW to the grid or can operate in heating mode with

simultaneous generation of 110 MW electrical and 35 MW thermal power. The total

machinery train length is 75 m.

Fig.12 – SSS Clutch Encased package with integrated TG device for GT turning

The challenge for designers was the rework of the existing simple cycle concept,

replacing the turning gear devices for the GT and generator which was previously

installed on the free end of generator. Changing the GT design was not possible and

therefore was not considered. Another task was ensuring the option of including any

desired standard ST of the suitable power but keeping the compact length of the

machinery train. Thus the special Size 216T Encased SSS Clutch design with three

bearings and integrated turning gear device with an electrical motor for GT and

generator turning was developed. The weight of the clutch output shaft has to be

supported by the generator bearing on the exciter side. Therefore the clutch package

and the generator together with the GT will be mounted on the same base plate.

Any standard ST of the suitable power and required operation mode can be installed

on the input side of the SSS Clutch package, connected through a suitable tooth

coupling providing additional modularization flexibility.

The calculated efficiency of the plant will be over 52% together with the high fuel

utilization ratio.

18

5 Conclusions.

All of the above examples demonstrate the broad versatility of CHP Plants. Although

they may appear complex, they all possess diverse operational flexibility giving rise to

higher efficiency rates when compared with separated electrical, heat and industrial

steam generation. In all cases studied, SSS Clutches are a key component which

assists in offering extended flexibility of the plant.

As indicated in several examples above, the CHP Plants discussed in this paper

have reduced carbon emissions when compared with separate generation.

A big challenge for new CHP development exists where the construction, electrical

generation as well as domestic heating and process steam industries need to work in

unison during town and city planning. This is especially true of areas which are not

yet familiar with CHP. The prize for a successful collusion is the opportunity to

receive government sponsorship in the form of carbon credits, tax benefits in the form

of enhanced capital allowance, popularity amongst the public from “green

advertising” and the potential to offer less expensive utility bills for residents and

industrial steam consumers.

References :

/1/ Finnish energy industries. Combined Heat and Power Production.

/2/ Renewable solid fuels replacing electricity and oil in an existing thermal energy

market, – Arild Dahlberg, Hafslund.

/3/ Analysis on Methods and the Influence of Different System Data When

Calculating Primary Energy Factors for Heat from District Heating Systems, -

Magnhild Kallhovd, 2011.

/4/ Die Summe macht’s: Nachrüsten von Dampfturbinen im Heizwerk lohnt sich. –

Energiespektrum 09/2002.

/5/ “Local Warming: Helsingin Energia Uses CHP to Heat the City” - Drew Robb,

PowerMag 2010.

/6/ KDHC website - http://www.kdhc.co.kr/eng/

/7/ “Alstom liefert und wartet eine der weltweit effizientesten Gasund

Dampfturbinenanlagen in Deutschland“, - Alstom Communication, 2012.

/8/ Концепция создания моноблока ПГУ-165 нв базе серийного газотурбинного

двигателя ГТД-110. – М.Р. Гасуль, М.Н. Леонов, Газотурбинные технологии

2012.

/8/ CHP Plant – Optimum Efficiency, Total Flexibility. – Nicholas Bellamy, Power-Gen

Europe 2009.