CONTAINERIZED 7.8 MW POWER PLANT CONCEPT

APPLICATION CASE STUDIES FOR A PRE-ENGINEERED

GAS TURBINE CHP PLANT

Dr. Marcus Hecken Harald Dichtl

Siemens Power Generation (PG), Germany

Abstract

Combined Heat and Power (CHP) is a highly efficient way to generate power and heat. By

linking a gas turbine with a heat recovery steam generator (HRSG) up to 90% of the fuel

energy can be converted into electric power and useful heat. This reduces Greenhouse Gas

(GHG) emissions in many cases by more than 30%.

Siemens Power Generation has developed a CHP plant concept for 5-13 MW gas turbines in

order to reflect the requirements of this market segment. In the first stage the development has

been based on the Siemens’ SGT-300 industrial gas turbine which is designed for highly

efficient combined heat and power generation. A benchmark with other industrial goods has

shown potential improvements by packaging the power plant systems into modular units.

These modules will be pre-engineered and packaged into containers which will only be

interconnected on the construction site.

Investigations have been made as to how to improve the economic value for the end user of

such a plant. Different aspects considering construction and erection time, lifecycle cost and

operational flexibility have been analyzed. This has formed the basis for the product

specification of the containerized power plant.

This paper will discuss this new power plant concept by means of case studies for the main

CHP applications. The main results of the investigation will be shown.

Keywords:

CHP, Cogeneration, Power Generation, Process Steam, Industrial Application, Siemens Gas

Turbine, Economic Evaluation

© Siemens AG 2006. All rights reserved.

1. Introduction

Increasing energy demands worldwide and simultaneous decreasing of energy resources

cause a rise of fuel prices on international resource markets. As a result of these developments

electricity prices have soared about 80% since 2004 [1]. The markets for fossil energy

resources seem to establish a clear medium-term tendency of rising prices.

Based on the Kyoto Convention an emission trading system has been established and will

influence future power plant development. Driven by the need to reduce emissions as well as

save fossil resources, power plant development has been focusing on designing highly

efficient facilities.

Combined Heat and Power (CHP) systems realize these requirements and generate both

process steam and electricity, especially for industrial applications, in an efficient way. By

linking a gas turbine with a heat recovery steam generator (HRSG) up to 90% of the fuel

energy can be converted into electric power and useful heat.

Based on these economical and ecological requirements, Siemens Power Generation has

developed a containerized CHP plant concept for 7.5 MW gas turbines. All components have

been pre-designed and pre-engineered.

2. Objective

This paper will present the containerized power plant SSC-300 Cogen concept as a

solution realizing high fuel utility ratios at economic costs. Based on various Life Cycle Cost

(LCC) calculations the profitability of CHP facilities for industrial applications will be

presented. The basic concept of the Siemens SSC-300 Cogen power plant will be shown.

3. Combined Heat and Power generation

Combined Heat and Power (CHP) generation realizes the simultaneous production of

electric power and heat. The basic element of a CHP solution is a combustion device -

predominately a gas turbine- driving an electric generator. The exhaust gases are utilized

within a Heat Recovery Boiler in order to produce process steam or hot water. A drawing

indicating the basic principles is shown in fig. 1, see below.

© Siemens AG 2006. All rights reserved.

17 % Exhaust Gas

50 % Process Steam

33 % Electric Power

Generator

HRSG

Gas Turbine

Air

Fig. 1: Basic Conc

In a standard CHP

electricity. Approx

water production.

ambient or process

Based on the princ

of industrial users

energy-intensive a

paper, or steel indu

Cogeneration offer

Environmental Ben

The global empha

strong position for

i.e. the specific a

Fuel Gas100 %

ept of a Combined Heat and Power System (CHP)

system the gas turbine generator transforms about 33% of the fuel into

imately 50% of the input energy is consumed for process steam or warm

The exhaust losses are about 17% but might be reduced, depending on

steam conditions.

iples explained above, CHP technology can be employed by different types

. This electricity / steam generating system can be adopted for supplying

pplications such as refineries, petrochemical, pharmaceutical, pulp and

stries. The process steam might be used for running thermal processes.

s a number of benefits as listed below.

efits

sis on reducing greenhouse gas emissions puts cogeneration systems in a

combined heat and power production due to its improved fuel utility ratio,

mount of emissions in relation to usable energy output. In addition,

© Siemens AG 2006. All rights reserved.

reasonably high fuel utility ratios contribute to saving fossil energy resources to a

considerably extent.

Economic Benefit

As will be shown in chapter. 4 the cost savings of CHP applications might be very attractive

compared to purchasing steam and electricity. Considering increasing energy prices on global

markets, the highly efficient CHP solution might give a better profitability than external

supply.

Improving Power Autonomy

CHP unites usually are located near to the production facility. The power plant and the

production sites are linked closely together. The industrial user is not dependent on an

external supplier and can act more flexibly on process load changes.

© Siemens AG 2006. All rights reserved.

4. Economic Evaluation of Cogeneration Processes - Case Study

In order to indicate the benefit for employing cogeneration (CHP) power plants a

yearly-cost analysis will be presented. For comparison reasons an industrial user will be

defined. The assumptions for the electrical power and steam demand are listed below.

Boundary Conditions and Assumptions

Unit Value

Average Electric Power demand kWel 7,500

t/h 18.5 Average Steam demand

MWth 12.5

Process Steam Pressure bara 17

Process Steam Temperature Saturated Steam

Operation Period per year h/a 8760

Operation Mode Base Load

Table 1: General Boundary Conditions

Based on these boundary conditions two different cases might be considered. These scenarios

form a general comparison between buying power or producing autonomously.

Case 1: Reference: Buying electric power from a supplier & producing process steam from a small fired boiler

In the first scenario electricity will be provided by an external power supplier. The steam for

the industrial application is produced by a small boiler. These conditions define the reference

case.

The process steam is generated at an estimated rate of about 30 €/MWh including fuel,

operation, and maintenance costs. The value is based on an average thermal efficiency of 85%

and a fuel purchase price 7 €/GJ [2].

Case 2: CHP Power Plant Generating process steam & electric power in a CHP facility

In scenario 2 a cogeneration system will replace the existing boiler for steam generation and

electricity purchases. Electric power and steam are generated by a small cogeneration power

plant based on all the performance values listed in the table below. The existing boiler might

be used as a back-up steam generator.

© Siemens AG 2006. All rights reserved.

Due to power plant outages for maintenance and service it might be necessary to buy electric

power temporarily from a supplier. Additionally process steam needs to be generated

elsewhere. The estimated time period for power plant failures is assumed to be around 500h

per year.

The economic calculations are based on all values listed in the table below.

Case 1 Reference Unit Comments

Price for purchasing electric power €/MWh 73 [3], Price also includes suppliers’ surcharges

Electric power: Escalation rate per year % 2

Average steam generation costs with conventional boiler

€/MWh 30 average thermal efficiency 85%

Steam generation costs Escalation rate per year

% 2

Fuel Price €/GJ 7

Fuel Price: Escalation rate per year % 2

Operation Period per year h/a 8760

Table 2: Boundary Conditions Case 1

Case 2 CHP Unit Comments

Fuel Price €/GJ 7

Fuel Price: Escalation rate per year % 2

Fuel input kWth 25,400 Fuel utility ratio about 84%

Price for purchasing electric power in case of power plant outages

€/MWh 95

Electric power: Escalation rate per year % 2

Estimated time of power plant outages h/a 500

Maintenance costs €/MWh 4.5

Miscellaneous costs (i.e. personnel, …) per year

k€/a 200

Plant operation period per year h/a 8260

Equity ratio % 100 debt payments not considered, investment will be paid completely at project start

Table 3: Boundary Conditions Case 2

These values seem to be a good estimation for the German power generation market but in

principle should be valid for all other European countries as well. Emission trading provides

the operation of a cogeneration power plant with some additional benefits. However, since the

domestic legislation is not uniform for all European countries, the emission trading has not

© Siemens AG 2006. All rights reserved.

been taken into consideration for these calculations. Probable subsidies for cogeneration

power generation are also disregarded.

Results

The annual costs for each case are shown in fig. 2 below.

2,000

4,000

6,000

8,000

10,000

Case 1 - reference Case 2 - CHP

Costs per year Costs for Outages (i.e. power purchase) k€

Fixed Costs (i.e. personnel)

Maintenance

∆=1,900 k€Process steam

Electric Power

Fuel

Fig. 2: Comparison: Costs per year

In the reference case (Case 1) only two main cost groups have been considered - expenses for

generating process steam and charges for purchasing electricity. These expenses sum up to an

overall value of about € 8 million/year.

In Case 2 a Cogeneration power plant will be employed. Fuel will form the major portion of

the overall expenses. Additionally maintenance costs and other fixed payments (i.e.

personnel, insurances…) have been taken into considation. In the event of outages, electricity

needs to be bought from a supplier. Steam will also be provided either from an external

source or by an existing back-up steam boiler. These costs are evaluated at. € 0.5 million

annually.

The annual costs savings of operating a CHP system compared to external electricity supply

are about € 1.9 million.

© Siemens AG 2006. All rights reserved.

To indicate the economic benefit for an extended time period the yearly expenses have been

accumulated. The results are shown in fig. 3.

20

40

60

80

100

0 2 4 6 8 10

mil.€/a Costs savings: € 18.5 mil after 10 years of operation

Case 1-Reference

Case 2-CHP

Cost Accumulation

Year of Operation

Fig. 3: Comparison: Cost Accumulation

Due to lower annual costs Case 2 reveals an economic benefit of about € 18.5 million after 10

years’ operation time. Regarding initial investments the pay-off period seems to be between

about 3 to 5 years.

5. Siemens’ Containerized CHP Concept

Based on the given considerations, Siemens is developing a small containerized power plant

for industrial applications. The target is to provide a Cogeneration power plant for industrial

applications which supplies the user with electric power as well as process steam. The main

technical data of the SSC-300 Cogen are given in table 4, see below.

SSC-300 Cogen, technical data

Electric Output 7.5 MWel

Process Steam Output 12.5 MWth

18.5 t/h, 13-22 bara

Fuel Utility Ratio 81 %

Table. 4: SSC-300 Cogen, technical data © Siemens AG 2006. All rights reserved.

Technical Concept Description

Generating process steam & electric power in a CHP facility

The SSC-300 Cogen design has been based on the SSC-300 gas turbine (formerly named

Tempest). In a Heat Recovery Steam Generator (HRSG) the process steam will be generated

on a slightly superheated level. The Balance of Plant components, the electrical,

instrumentation, and control units are enclosed within different containers. A drawing of the

general concept is shown in fig. 4, below.

Balance of Plant

I&C

Gas Turbine SGT-300

HRSG

Fig. 4: SSC-300 Cogen, Containerized Concept

For generating power and steam in a most efficient way the investment and delivery periods

need to be optimized. Therefore the different units have been pre-designed and pre-engineered

in order to reduce the overall project time.

© Siemens AG 2006. All rights reserved.

The SSC-300 Gas Turbine will be delivered in a packaged arrangement. This compact design

reduces site time for erection and commissioning.

The Heat Recovery Steam Generator (HRSG) will be pre-designed at a very advanced level.

Different options such as by-pass stack may be added if necessary. Due to a high degree of

pre-fabrication the HRSG will be delivered only in a few pieces and assembled quickly on

site.

In order to optimize costs for the auxiliary systems all units are located in containers. The

containers are a standardized size can be transported easily. As for the HRSG, the auxiliaries

are at an advanced stage of pre-design and pre-engineering. The different systems are split

into logical units and located in these containers. For instance, the deaerator and control room

are attached to separated boxes.

This containerized and modular design forms a compact system. The units are designed to be

pre-fabricated and assembled on site quickly.

Fig. 5: SSC-300 Cogen, Containerized Concept © Siemens AG 2006. All rights reserved.

Advantages and Characteristics of the SSC-300 Cogen Concept

The SCC-300 has been developed for industrial applications with steam and electricity

demand. For common industrial applications power generation is only a necessity in order to

supply the production lines. Therefore the SSC-300 has been designed as simply and robustly

as possible.

Besides easy handling and robust construction, the economic benefit is a main advantage. Due

to the thermodynamic design an overall fuel utility ratio of about 81 % has been realized, with

resulting low specific fuel costs. Furthermore, due to these efficiency values, specific

emissions will be reduced. For the economic evaluation in chapter 4 neither emission trading

nor subsidies have been taken into account. These issues might also significantly increase the

economic advantages for combined heat and power systems.

6. Conclusion

Combined Heat and Power systems (CHP) generate process steam as well as electricity,

especially for industrial applications, in an efficient way. By linking a gas turbine with a heat

recovery steam generator (HRSG) up to 90% of the fuel energy can be converted into electric

power and usable heat.

Siemens Power Generation has developed the containerized SSC-300 Cogen Power Plant

system for such applications. The basic concept has been presented and discussed in detail.

Based on a Life Cycle Cost calculation the profitability of the SSC-300 has been investigated

and the economic attractiveness shown.

7. References

[1] VIK Verband der industriellen Energie- und Kraftwirtschaft e.V.: Strompreisindex

[2] APX group, fuel price February, 28th, 2006, see also www.apx.nl

[3] EEX-European Energy exchange, electricity price February 28th, 2006, www.eex.de