Bioenergy Agreement Task XI11

Biomass Utilization

Technologies for Small Scale WOOd-FUdled Combined Heat and Power Systems

Henrik Houmann Jakobsen Serren Houmerller Lars Thaaning Pedersen dk-TEKNIK, Energy & Environment Gladsaxe Msllevej 15 dk-2860 Sarborg Denmark dk-TEKNIK . GLADSAXE MBLLEVEJ 15. DK-2860 S0BORG . TEL t45 39 69 65 11 . FAX t45 39 69 60 02 DISCLAIMER

Portions of this document may be illegible electronic image products. Images are produced from the best available original document. Introduction

The aim of this study is to describe and compare different technologies for small cogeneration systems (up to 2-3 We),based on wood as fuel.

For decentralized cogeneration, i.e. for recovering energy from saw mill wood wastes or heat supply for small villages, it is vital to know the advantages and disadvantages of the different technologies. Also, for the decision-makers it is of importance to know the price levels of the different technologies.

A typical obstacle for small wood cogeneration systems is the installation costs. The specific price (per kW) is usually higher than for larger plants or plants using fossil fuels. For a saw mill choosing between cogeneration and simple heat production, however, the larger installation costs are counterweighed by the sale of electricity, while the fuel consumption is the same. Whether it is profitable or not to invest in cogeneration is often hard to decide.

For many years small wood cogeneration systems have been too expensive, leading to the construction of only heat producing systems due to too high price levels of small steam turbines.

In recent years a great deal of effort has been put into research and developing of new technologies to replace this traditional steam turbine. Among these are: e Steam engines e Stirling engines e Indirectly fired gas turbines e Pressurized down draft combustion.

Along with the small scale traditional steam turbines, these technologies will be evaluated in this study.

When some or all these technologies are fully developed and commercial, a strong means of reducing the strain on the environment and the greenhouse effect will be available, as the total efficiency is high (up to 90%)and wood is an energy source in balance with nature.

The study has been performed by dk-TEKNIK, Denmark, within the framework of the IEA Bioenergy Agreement Task X, Combustion activity. All countries represented in the Technical Committee of the task have contributed with guidelines, facts and informations to the project.

In this version more detailed economical calculations including a sensitivity analysis is presented compared to previous versions.

Authors are Henrik Houmann Jakobsen Lars Thaaning Pedersen / Ssren Houmller

EA Task X - Technologies for Small Wood Co-Generation Systems Page 1 TABLE OF CONTENTS

1. Scope of Work ...... 4

2 . Watch Out! ...... 5

3 . Steam Turbines ...... 6 3.1 Basic Principles ...... 6 3.1.1 The Rankine cycle ...... 6 3.1.2 The Steam Turbine ...... 7 3.2 Sites of R&D ...... 8 3.3 Stage of Development ...... 9 3.4 Economy ...... 9 3.5 Feasibility ...... 10 3.6 Major Barriers for Technical Adaptability to Existing Energy Infrastructure...... 10

4. Steam Engines ...... 11 4.1 Sites of R&D ...... 11 4.1.1 Traditional Engines ...... 11 4.1.2 Modified Traditional Engines...... 12 4.1.3 Diesel Based Systems...... 13 4.1.4 Modern Steam Engines ...... 14 4.2 Stage of Development...... 14 4.3 Economy...... 14 4.4 Feasibility ...... 15 4.4.1 Advantages and Disadvantages of the Steam Engine...... 15 4.4.2 Necessary Innovations...... 16 4.5 Major Barriers for Technical Adaptability to Existing Energy Infrastructure...... 16

r m .. .. 3 . stirling mgmes...... W 5.1 Sites of R&D ...... 19 ?an e- . 3.~stage or ueveiopment ...... LL"1 5.3 Economy ...... 22 5.4 Feasibility ...... 23 5.4.1 Advantages and Disadvantages of the Stirling Engine ...... 23 5.4.2 Necessary Innovations ...... 25 5.5 Major Barriers for Technical Adaptability to Existing Energy Infrastructure...... 25

6 . Indirectly Fired Gas Turbines ...... 26 6.1 Sites of R&D ...... 26 6.2 Stage of Development...... 27

6.3.1 Canadian investigation ...... 28 6.3.2 Belgian investigation ...... 28 6.4 Feasibility ...... 29 6.4.1 Advantages and Disadvantages of the Indirectly Fired Gas Turbine 29 1 ...... 6.4.2 Necessary Innovations ...... 30 6.5 Major Barriers for Technical Adaptability to Existing Energy Infrastructure...... 30

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 2 7 . Direct Fired Pressurized Gas Turbines ...... 31 7.1 Sites of R&D ...... 31 7.2 Stage of Development...... 32 7.3 Economy...... 32 7.4 Pressurized Direct Fired Gas Turbine. The PGI Concept ...... 33 7.4.1 Stage of development...... 34 7.4.2 Economy ...... 34 7.5 Feasibility ...... 34 7.5.1 Advantages and Disadvantages of Pressurized Down Draft Combustion ...... 34 7.5.2 Advantages and Disadvantages of Pressurized Direct Fired Gas Turbine ...... 35 7.6 Major Barriers for Technical Adaptability to Existing Energy Infrastructure...... 36

8 . Economical comparison of different technologies ...... 37 8.1 Introduction ...... 37 8.1.1 Definition of economical optimum size ...... 37 8.2 Duration graph ...... 38 8.3 Introduction ...... 39 8.4 Example ...... 39

9 . Economical calculations ...... 41 9.1 Def~tionof heating market ...... 41 9.2 Choice of individual technology for economical calculations ...... 41 9.2.1 Steam turbine ...... 41 9.2.2 Steam engine ...... 41 9.2.3 Stirling engine ...... 41 9.2.4 Indirectly fired gas turbine ...... 41 9.2.5 Overview ...... 42 9.3 Assumptions ...... 42 9.3.1 Prices ...... 42 9.3.2 Operation and maintenance ...... 42 9.3.3 CHP-plant data ...... 42 9.3.4 Modulation of CHP-plant ...... 43 9.4 Calculation of operational pattern ...... 43 9.5 Discussion ...... 44

10 . Optimum size of CHP-plant ...... 46 10.1 General data ...... 46 10.2 Steam turbine ...... 47 10.3 Steam engine ...... 48 10.4 Stirling engine ...... 49 10.5 Indirectly fired gas turbine ...... 50 10.5.1 Comparison of annual production expenses ...... 51 10.6 Sensitivity analysis ...... 51 10.7 Discussion ...... 52 10.8 Conclusion ...... 52

11. List of Literature ...... 54

IEA Task X .Technologies for Small Wood Co-Generation Systems Page 3 1. Scope of Work

The treatment of the different technologies will to a great extent follow the main lines described below:

Where R&D goes on. Description of companies, universities etc. with R&D on the technology. A short presentation of results.

Stage of development. The present stage of development evaluated on basis of the informations above.

Economical aspects. The capital costs and maintenance costs for the technology are outlined. An economical evaluation of the technology is made, so that it can be compared with the other technologies.

Feasibility. The feasibility, Le. the possibilities for introducing the technology, is described. For instance, what are the possibilities for making the technology commercial? Advantages and disadvantages connected with the technology are described.

Major barriers for technical adaptability to existing energy infrastructure. Description of barriers making technical adaption of the technology to the existing energy supply difficult, both overall and specifically for the given technology.

Especially for the economical aspects there is some deviation from point to point as different sources use different methods for estimating the costs. From the sources the necessary costs and other values have been extracted, so the economical data should be comparable. In some cases elaborate data is given if a source has made significant calculations.

All technologies are technically and economically compared in the end of the study.

EA Task X - Technologies for Small Wood Co-Generation Systems Page 4 2. Watch Out!

It is important to remember that the information given in this report is based on information obtained from various sources such as producers, papers, books and reports; no innovative research has been under- taken.

Furthermore, as many of the technologies are not yet fully developed, values and numbers are to a great extent based on estimates, mostly made by producers and researchers. The results presented here must therefore only be considered as guide lines.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 5 3. Steam Turbines

The traditional steam turbine is practically absolute in the larger power- and cogeneration plants although combined cycle with gasturbines are getting increasingly popular. In the steam turbine the energy is contained in the steam, which is converted into a rotational motion by the steam turbine. This motion is then converted into electrical energy by an electric generator.

3.1 Basic Principles

3.1.1 The Rankine cycle

5 5 T

Figure 1. The simple Rankine cycle. A pump is pumping the water around (I -2).

The basic steam cycle is based on the closed Rankine process, shown in Figure 1, also showing the cycle in the T-s diagram. In the Rankine process water heated up (from 2 to 3), evaporated (3-4) and superheated (4-5) in a boiler forming steam, which is then expanded through the turbine (5-6). After the expansion the steam is led through a condensator, where the steam is cooled, turning it into liquid water again (6-1). Now the cycle can start again.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 6 5 5b 5a I 6 1 I-t I &. cz 5b 1 < r;oollng

S

Figure 2. The Rankine cycle with superheating.

In practice the steam cycle is refined to a certain degree, depending on the use of the plant, its size etc. Usually the cycle has some feed water preheaters and some superheaters. The preheaters are placed between points 2 and 3, while the superheating is taking place by leading the steam through the boiler after it has expanded somewhat, i.e. to point 5a in Figure 2. These components are increasing the efficiency of the plant, but also the investments in it. As a consequence, base load plants are equipped with a larger amount of auxiliary heaters etc. than peak load plants because of longer operation hours of the former, thereby enabling the plant to produce more power in a given period of time.

3.1.2 The Steam Turbine

Runner Axial steamflow Axial steamflow

Figure 3. Schematic of a steam turbine and a turbine step.

As mentioned above the steam expands through the turbine. The turbine is a complicated piece of turbo machinery and is therefore an economically significant part of a power- or cogeneration plant. A schematic of a steam turbine and a view through a step in the turbine is shown in Figure 3. In the turbine the steam is moving relatively slow (about 60 m/s) into some stationary blades, working as nozzles, thereby increasing the velocity to about 300 m/s, decreasing the pressure and forming a whirl. The next

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 7 set of blades are now converting the velocity into a rotating motion, while the steam leaves the set of blades in axial direction, ready for the next step. As it can be seen from the velocities, the enthalpy drop over a step is quite small, which means that a turbine must consist of several steps, depending on the conditions under which the turbine must work.

The steam turbine can be made to bigger power outputs than any other prime mover, making it without competition in large scale plants. Furthermore, turbines can be made with high efficiencies. For smaller plants, however, the turbine efficiency decreases and becomes much less efficient than i.e. a steam engine. For partial load the efficiency of the turbine decreases fast while the efficiency of i.e. the steam engine is practically linear.

3.2 Sites of R&D.

Due to the extensive use of steam turbines in larger power plants there is a continued ongoing research within the large turbine area. There is, however, also some development in the small steam turbine range from 0.25 MW to 10 MW,. In [l] a survey has been carried out over steam turbines in the 2-10 MWe range and 0.25-2 MW, range for back pressure turbines. The survey aimed at finding companies supplying small turbines, the steam quantities required for operation and an estimation of the capital costs for the equipment. The results of the survey are shortly introduced here.

40 bar condensing 20 bar condensing 40 bar back pressure 20 bar back pressure - 5 bar out - 5 bar out I Rating (MWd 2 5 10 2 5 10 2 5 10 2 5 10

9.8 25.9 46.1 12.3 29.7 58.0 21.5 51.5 99.6 36.1 86.8 160.3

4.9 5.2 4.6 6.1 5.9 5.8 10.7 10.3 10.0 18.0 17.4 16.0 (t/MW,*h)

Average cost (lo00 US$) 708 1,287 2,006 713 1,255 1,972 571 810 1,365 510 891 1,408

Specific costs (US$/kW> 353 257 201 356 251 197 285 162 137 255 177 141 Zggure 4. Quoted steam consumption and capital costs, 2 10 MW,. At 40 bar: Ti,=400"C. At 20 bar: Tin=300"C. Note: Prices only include the turbine itself.

The steam consumption and capital costs for turbines between 2 and 10 MW, are shown in Figure 4. For back pressure turbines between 0.25 and 2 MW, the corresponding values are given in Figure 5.

Figure 4 and Figure 5 show some well-known observations; larger turbines are more efficient than smaller ones, less steam is used at high pressures and steam consumption for a given electrical output increases significantly where there is a substantial requirement for steam at lower pressure. The cost information (not all available here) shows significant price differences between manufacturers. Average costs decreases with increased turbine rating, while costs are virtually independent of steam input pressures.

The information given here should be used as background material only. Specific information should be obtained from supplyers before making basis for decisions. A market review can be found in [2]

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 8 ~ ~ ~ 40 bar back pressure - 2 bar out 20 bar back pressure - 2 bar out Rating (MW3 l2 1 0,5 0,25 2 1 0,5 0,25 Avg. steam consumption (tih) 22.8 11.7 6.6 3.7 35.3 17.8 9.7 5.1

Specific steam consumption 11.4 11.8 13.2 14.8 17.6 17.8 19.4 20.5 (t/MW,*h) 267 168 104 70 273 159 87 70

Specific costs (US$/kWe) 168 208 278 136 159 174 278 133 I1L! I Figure 5. Quoted steam consumption and capital costs, 0.25- MW,. At 40 bar: Ti,=400"C. At 20 bar: Ti,=200"C. Note: Prices only include the turbine itself.

3.3 Stage of Development

Several companies are manufacturing steam turbines and since a large turbine is likely to cost about 100 million US dollars, these companies are depending on the sale of their turbines. As a consequence the turbines are continuously being refined and improved. Although most research is being done in larger turbines, the smaller ones are also being developed. For small turbines the main hurdle is the price of the turbines, being as small as 250 kWe. At present several small turbines suitable for CHP-schemes are available on the market, so the steam turbine is at a stage where it is fully commercial and can be bought on standard terms.

3.4 Economy

On basis of [ 13, [4] has calculated the specific costs and efficiency of some small steam turbines, using a generator efficiency of 92%. The result is shown in Figure 6. Actual efficiency: Measured efficiency under practical circumstances. Rankine efficiency: Ideal thermal efficiency. Actual to Rankine efficiency expresses the ratio between the two.

The conclusions in [l] are that for 2-10 MW, turbines there are no clear advantage of any one manufacturer. The most efficient turbine was only 2-3 % more efficient than the average, but price variations were substantial. As an example was the most efficient turbine 132% more expensive than another turbine only 2.2% less efficient. For the 0.25-2 MW, turbines the steam consumption varied up to 25 % and cost variations were wide and strongly depending on frame sizes.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 9 In general, it is suggested that the capital costs for small turbines up to 10 MW, would be in the range $150-300/kWe in 1988 prices, corresponding to 520% of the total project costs, Economical calculations for a 620 kW, plant can be found in [3]

output Steam Steam Back Actual Rankine Actual to costs pressure temp. pressure efficiency efficiency Rankine eff.

250 40 400 2 9.8 24 40 279 250 20 300 2 7.6 18 42 278 500 40 400 2 11.0 24 46 207 500 20 300 2 8.0 18 45 174 Figure 6. Specific costs and efficiencies for small steam turbines. Note: Prices only include the turbine itself.

3.5 Feasibility.

The steam turbine is the most feasible of the technologies in this text, as it is the reference technology all the other technologies are compared to. Small turbines are based on experiences from the large turbine industry and has therefore got a head start, which is the reason that the turbine is the most advanced technology. It is, however, likely that some of the other technologies may prove to be more feasible in the future. To illustrate the potentials of the steam turbine, it's advantages and disadvantages are described here. Advantages are: The steam turbines often have lower installation costs in the 0-5 MW, range than other small size technologies for steam of good quality (40 bar). For lower pressures (10-20 bar) the steam turbine efficiency decreases significantly. The turbine can withstand high pressures and temperatures. No oscillating masses forces reduce strain on the foundation.

Disadvantages include: Small single stage turbines have a bad efficiency. Multi stage turbines are too big for the power range considered here. The part load efficiency is poor compared to the other technologies. The turbine is highly dependent on the quality of the steam available. Steam of poor quality can be used with better performance with other technologies. At 10 bar the efficiency of the turbine decrease to about 6 per cent. Also the steam humidity is important as the turbine blades will be damaged at a water content of more than 15 per cent.

3.6 Major Barriers for Technical Adaptability to Existing Energy Infrastruc- ture.

As the existing energy infrastructure is based primarily on the steam turbine, there are no technical barriers.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 10 4. Steam Engines

The steam engine is based on the original Newcomen design from 1712 used for the draining of tin mines. This steam engine used the atmospheric pressure to effect the engine's power stroke. Later James Watt improved the steam engine to work with higher pressures, making it more compact and usable for Le. locomotive's engines.

The steam engine is a proven technology able to withstand constant operation in industrial environments. They are only produced in small numbers making them relatively expensive. The efficiency of the steam engine is depending more on the quality of the steam available than the engine design. As a result of this the efficiency can be raised by using other boilers with better steam data. The steam engines are reliable, only demanding small maintenance costs.

The principle behind the steam engine is similar to that of the ordinary internal combustion engines known from cars. The main difference is that in the steam engine the working fluid is steam, while it is hot combustion products in the internal combustion engine. After leaving the steam engine cylinder the steam is condensed to water by extracting heat and can be returned to the boiler. In contrast to the internal combustion engine - where the forces of the hot combustion products only act on in one direction of the piston movement - most steam engines are double-acting. This means that the steam expands in both the forward and backward stroke of the piston. Therefore the double-acting steam engine is lighter and smaller than the internal combustion engine at a given output.

The steam engine and the future aspects and possibilities connected with it are thoroughly described in [4].

4.1 Sites of R&D.

A british review [4] compares the steam engine and Stirling engine technologies for producing electricity from wood waste. The review identifies 11 manufacturers and research organisations producing or developing commercial steam engines. Of these, only 5 offer an engine that could be considered a commercial product, while the rest only have prototypes or paper projects. Also engines for the leisure market are in production, but these are unsuitable for CHP purposes.

Figure 7 summarises the main operating conditions and commercial status of the engines. The engines have been categorized into 4 groups: traditional, modified traditional, diesel based and modern, depending on the degree of departure from the traditional steam engine design.

A summary of steam engine organisations can be found in Enclosure 1.

4.1.1 Traditional Engines. The main markets for the traditional engines are CHP using excess biomass in quantities too small for economical operation of steam turbines in places with unreliable or costly grid electricity supply.

EATask X - Technologies for Small Wood Co-Generation Systems Page 11 ~~ ~ ~~ ~ ~ Manufacturer Size (kW,) Pressure (bar) Speed (rpm) status Category Fezer 50-400 16 450 Commercial Mernak 26-600 10-15 240 Commercial Traditional

Skinner ' 275-1000 10-20 400 Commercial Thai n.d.a. n.d.a. n.d.a. Commercial SwedSteam 125 n.d.a. n.d.a. Prototype DanSteam 500 26 n.d.a. Prototype Modified BEST 50 13 1500 Prototype traditional Spilling 27-1400 6-60 750-1500 Commercial ANU 15-115 24-42 600 Commercial Adelaide University n.d.a. n.d.a. n.d.a. Paper Diesel Skinner 250 10-20 1000 Commercial ESD Engines 25-300 10 1500 Paper Modern n.d.a.: no details available; Commercial: commercial product available; Prototype: prototype built; Paper: paper design. Figure 7. Operating conditions for different steam engines.

Four manufacturers/researchers have been identified.

Fezer SA, Steam Engines Division, Industrias Mecanicas, Cacador City, Santa Catalina, Brazil. Traditional, low speed, vertical cylinder engine. Rating: 310 kW, at 19 bar inlet pressure. Part load down to 80 kW,, superheating makes output of 400 kW, possible.

Mernak SA, Steam Engines Division, Industria Brasiliera de Maquinas, Cachoeira do Sul City, Riogrande do SUI, Brazil. Single cylinder, double acting, slow speed horizontal "locomobile" engines.

Skinner Engine Company, Power Division, PO Box 1149, Erie, PA 16512, USA. Long established manufacturer of traditional vertical cylinder double acting industrial engines. Recent developments are improved materials and bearing and seal technology.

Thai steam engine manufacturers. At least 10 companies are known to have produced traditional horizontal steam engines with 5 meter flywheels in the power range from 80 to 300 kW,. The efficiency was not very important with examples of efficiencies of 2 % . At least one company still exists.

4.1.2 Modified Traditional Engines. Also four companies are working with this kind of steam engine. Only the Spilling engine is commercially developed.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 12 Biomass Energy Services and Technology (BEST) Pty. Ltd., 5 Kenneth Avenue, Saratoga NSW 2251, Australia. An extensive test program on a 25 kWe prototype has been completed. Designed to avoid lubrication using PTFE sealing rings. Trials with dry bearing materials are being undertaken.

SpiIIing GmbH, Werfstrasse 5,2000 Hamburg 11, Germany. The Spilling engine is based on a single cylinder module, which can be put together with other modules making larger engines. With three different module sizes, up to 5 or 6 modules can be put together, making the effect range starting at 27 kWe and ending at 1400 kWe. The main market is industrial CHP and Spilling is probably the largest manufacturer of steam engines today. The engines are claimed to run 24 hours a day, 365 days per year and last for 30-40 years. A Danish investigation [5], however suggests that the data supplied by Spilling should be evaluated with caution.

SwedSteam AB, Box 4072, S-183 04 Taby, Sweden. SwedSteam is developing a steam engine technology in the 100-1000 kWe range for use in developing countries and for CHP in developed countries. A 125 kW, prototype was built and a 250 kWe engine designed, but all activities ceased a few years ago. In 1994 new owners reactivated the company. At present SwedSteam is making tailored wood fuelled power plants up to a few me.

DanSteam, Milton Andersen AIS, Kornmarksvej 8-10,2605 Brandby, Denmark. The DanSteam engine is based on the SwedSteam design, building a 500 kWe prototype. This engine is designed to run with an inlet pressure of 26 bar and a temperature of 380°C, leading to an electrical efficiency of 18.2% [6]. The seallings have been refined so that no contamination of the steam by the oil takes place. The development of the engine is sponsered by the EC. A complete CHP-plant based on a revised engine design by dk-TEKNIK is being built and is planned to begin operation in 1997 [7].

4.1.3 Diesel Based Systems. The main advantage of the diesel based systems is the use of traditional diesel engine blocks and other components, thereby decreasing the production costs.

Adelaide University, Dept. of Mechanical Engineering, GPO Box 498, Adelaide, SA 5001, Australia. Dept. of Mechanical Engineering are developing a small steam engine to be used with their research in fluidized bed combustion. The present plans are aiming at a 4 kW, experimental engine, and it is unlikely that larger engines will be developed.

Australian National University (ANU), Pty. Ltd., GPO Box 4, Canberra ACT 2601, Australia. This engine was designed to run on steam produced by a solar power station in the Australian desert. The engine is based on a Lister and a General Motors 53N diesel engines. At present a three cylinder 40 kWe and a four cylinder 60 kWe have been produced. A six cylinder engine is planned. For outputs up to 200 kWe two or more engines can be coupled together. The latest information is that seven engines have been sold, but none of them for commercial operation.

Skinner Engine Company, Power Division, PO Box 1149, Erie, PA 16512, USA. The Skinner Engine Company also develops engines based on diesel engines. The piston speed is here increased to 6 m/s from the 1-3 m/s of the traditional steam engine, though considerably slower than the 9 m/s expected from the ordinary diesel engine. Skinner claims to be able to supply a 250 kWe steam engine.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 13 4.1.4 Modern Steam Engines. The modern steam engine category includes engines with a design far from the traditional engine.

SES (former ESD) Engines Ltd., 51 Artesian Road, London W2 SDB, United Kingdom. The range of the ESD engines is from 25-300 kWe for CHP purposes in both industrial and developing countries. The aim is to develop a low cost, high speed, efficient and low friction engine to use saturated steam at up to 15 bar. Later versions will use higher pressures and super- heated steam.

4.2 Stage of Development.

The steam engine is based on the original Newcomen principles. The reason why the use of steam engines declined since the twentieth century was the development of the internal combustion engine. Compared to this, the capital and maintenance costs of the steam engine are too high and the efficiency too low to be competitive. The main uses today are for applications where internal combustion engines cannot be used, ie. the making of electricity from wastes or surplus steam in the industry. As it is not possible to buy a commercial steam engine on the same terms as the steam turbine, the stage of development is not as high. Much work must be done before the engine is commercially viable.

4.3 Economy.

For the steam engines available on the market at present, [4] has calculated the sales price and the specific sales price shown in Figure 8. The actual efficiency cannot be compared from engine to engine, as it depends on inlet and outlet conditions; higher steam temperature and pressure increase efficiency. To compare the engines, the Rankine efficiency and ratio of actual to Rankine efficiency should be used. The DanSteam engine, which was not developed when the mentioned report was made, has an actual to Rankine effiency of about 80% and an actual efficiency of 18.2%

When comparing the specific costs (last column in Figure 8) it appears that the modular construction of the Spilling engine and the diesel approach by ANU does not give smaller installation costs compared to the Fezer engine. As the ANU engine is still under development, it can be assumed that the prices of this engine will decrease further.

Only few data are available on maintenance costs. Spilling claims these to be around the same as for diesel based CHP systems.

In [4] a cross-over point at around 3-400 kW,, based on British conditions, has been found. Below this the steam engine is cheaper than the steam turbine and above the steam turbine is the cheaper. This is partly because the steam engine can use steam in a wide range, while the turbine requires at least 20-40 bar.

EATask X - Technologies for Small Wood Co-Generation Systems Page 14 Power Inlet Inlet Back Actual Rankine Act./ Invest- Spec. output pres. temp. pres. eff. eff. Rankine ment invest. Company' eff. ratio costs costs

(kW3 (bar) ("C) bar) (%I (%I (%) (US$) (US$/kW) Fezer 16 201 sat 1.o 8.7 20 43 54,000 672

Fezer 16 201 sat 1.o 8.1 20 41 67,200 240z

13 ? ? ? ? > 30,000 600

BEST 16 14 195 sat 1.o 1.6 19 40 12,000 750

Spilling 675 10 180 sat 1 .o 11 17 65 397,500 588

Spilling 40 350 sup 6.5 11.3 17 66 405.000 405

Spilling 40 250 sat 6.5 9.2 16 58 364,800 696

24 220 sat 0.25 10.5 22 48 55,500 6,938 ANU I 50 42 415 sup 0.25 22 33 67 55,500 1,110 75 42 415 sup 0.25 22 33 67 64,500 849

la0 42 415 sup 0.25 22 33 67 87,000 870

250 18 ? sat 1 '? ? 95,000 380

26 380 sup 1 16,7 '? 192,400 385

40 380 sup 1 21,2 ? 192,400 303

40 380 sup 1 21,2 '? ? 340,400 268 sat: saturated steam, sup: superheated steam Prices supplied June to December 1991. Exchange rate: 1&= 1.5 US$, 1 DKK = 0.148 US$. 1) Spilling and Fezer data based on manufacturers claims, BEST and ANU data from actual tests. 2) The two Fezer systems are based on the same engine. For the 80 kW, model the steam rate is reduced. 3) The two smallest DanSteam engines are the same, but uses different steam qualities.

Figure 8. Data and prices for some steam engines. Note: Prices only include the engine itself.

4.4 Feasibility.

4.4.1 Advantages and Disadvantages of the Steam Engine. For a steam engine to be used with small biomass fueled CHP systems, the advantages are: The traditional steam engine is a proven, robust technology that can withstand constant operation in an industrial environment. The gaseous combustion products do not pass through the steam engine and contaminate the interior as

it is the case for internal combustion engines and directly fired gas turbines. I The poor efficiency of some engines may relatively easy be improved by the use of good internal combustion engine design practice. This can be done by incorporating modern materials and modern automatic controls without decreasing lifetime or reliability. For smaller engines using standard industrial boilers (less than 26 bar pressure) the efficiency is reasonably good. The DanSteam engine has an expected efficiency of 18.2% using a standard boiler.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 15 The disadvantages are: The efficiency is usually quite low, sometimes AS than 10 % . This is not due to bad engine design, but to the fact that the steam quality is vital for the efficiency. It is no big problem to design steam engines to use steam at 100 bar, but then custom made boilers must replace standard industrial boilers, which will increase costs considerably. Most existing manufacturers use old designs and outdated technology. Furthermore, the engines are only produced in small numbers with many machined parts.

4.4.2 Necessary Innovations. The steam engine is capable of withstanding constant operation in an industrial environment and is considered a reliable prime mover. At present, companies and researchers are introducing the following three innovations to reduce the capital and maintenance costs, as well as the efficiency.

1) Dry bearing materials for piston rings and piston rod neck socks to allow oil-free cylinder lubrication. The aim of this exercise is to reduce lubrication and maintenance costs and to prevent contamination of the steam. This will eliminate the need for removing oil from the condensate water and reduce both capital costs and maintenance costs. Carbon rings and PTFE filled materials are currently being tested by some companies.

2) Using diesel engine components will reduce costs and help increasing the engine speed as they are mass-fabricated, thoroughly-tested pieces of equipment. In contrast to the best traditional steam engines, however, steam engines based on diesel components can only be singleacting. As a consequence, the power-to-weight ratio is lower and the costs generally higher. The cost- benefits of the diesel approach are still to be demonstrated (ANU, Adelaide University, Skinner).

3) Using modular construction allows the development of a wide range of power outputs with very few basic engine sizes. This will reduce tooling costs and make the production more efficient.

Four Spilling engines installed at Shell's Stanlowe refinery in Liverpool have been running continuously for the past 30 years and given a full overhaul every three years, indicating that the engines are highly reliable. It appears that the problems connected with the steam engine can be overcome. It must be concluded that steam engines can be quite feasible, especially if the costs can be reduced and the efficiency improved. As it looks now the steam engine is too expensive to be competitive with especially the steam turbine for smaller plants. For engines larger than about 500 kW, a boiler of the same type used with turbines must be chosen. When this is the case the steam engine is not feasible anymore. A good bit of research and testing must be carried out, and although the Stanlowe engines have had lots of operating hours, duration tests on new designs have to be made.

4.5 Major Barriers for Technical Adaptability to Existing Energy Infrastruc- ture.

The only absolute requirement for the steam engine is the presence of steam with a pressure of at least 10 bar and a temperature of at least 180°C. Is this the case there are usually no problems connected with installing a steam engine. The number of installed engines is low primarily due to competition from other prime movers, Le. internal combustion engines and steam turbines. In smaller plants with lower electrical efficiencies it is important for the economy of the plant that the heating market is sufficient as a large amount of heat is present here. This also applies to other technologies with small electrical power outputs.

EA Task X - Technologies for Small Wood Co-Generation Systems Page 16 5. Stirling Engines.

The Stirling engine is thoroughly described in [4] along with the steam engine, and for more eloborate information please consult this source. Here, only a short description will be found.

Hot space Regenerator. Cold space Pressure

3

Gas volume

Volume Theoretical Dressurelvolume curve

Pressure

3

Volume Actual Dressurelvolume curve

Figure 9. Schematic diagram of the Stirling engine cycle.

By the late 19th and early 20th century several thousand Stirling engines with a maximum output of 4 kW were in operation in Europe and USA, based on the Scottish Stirling brothers' developments in the first half of the 19th century. As it was the case with the steam engine, the Stirling engine was manouvered out by the more efficient and lighter internal combustion engine. An interest was still maintained as the Striling engine is quiet and has low emissions, leading to a revival of the engine in the 1930s by Philips. Since then, Philips has sold licenses to companies in USA and Europe wanting to apply the engine for

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 17 automotive use. Other applications are for submarine applications (low noise), solar powered engines for electricity generation and Stirling cycle coolers.

The Stirling engine differs from the steam- and IC-engine by being an external combustion engine in which the fuel is combusted outside the engine and the heat then transferred into the cylinder through a heat exchanger or the cylinder wall. This means that the Stirling engine can utilize any heat source of sufficiently high temperature.

The working principle of the Stirling engine is shown in Figure 9 (taken from [8]). The working gas, which is enclosed by the two pistons, moves continuously back and forth between the hot and cold spaces and is continuously heated or cooled. In the regenerator heat is stored when the gas moves from the hot space to the cold, and is given off when the gas moves the opposite direction. Compression takes place when most of the working gas is in the cold space at low pressure. Expansion takes place when the working gas is in the hot space at high pressure. The pistons are mechanical connected so that the proper volume deviation is achieved. In most engines the pistons have two fbnctions: They move the gas back and forth between the hot and cold spaces and they transfer mechanical work to the drive shaft. This dual function piston systems is known as the double-acting piston principle. A four cylinder double acting Stirling engine can be seen in Figure 10 [8].

.ce 'd'Cooler Figure 10. 4-cylinder double-acting Stirling engine principle.

The expected high efficiency (up to 40 per cent shaft power to infeed fuel), low maintenance costs and low noise level of the Stirling engine concept point towards a promising future.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 18 5. Sites of R&D.

In [4] 20 commercial companies and 11 research institutes have been identified, indicating more activity within the development of Stirling engines than within steam engines. Most of the research has been based on the Philips innovations from the 1950s and '60s. The designs have become quite complex and use exotic materials, making them dificult and expensive to manufacture. As a result of this much effort is now used in reducing the costs.

Of the 20 commercial companies 17 still are still active. These are listed in Figure 11 along with others identified from other sources. The research by the companies can be summarized as the following. For a list over research institutes please consult enclosure 2.

Quite recently the American company Allison has bought the license to produce Stirling engines for use in vehicles to meet the tough future environmental regulations in Los Angeles, as the engine has low emissions.

Company Engine Size Pressure Speed Charge gas Engine status We) Cod (rPm) Kockums (Sweden) V-160 8 150 1800 He PP 4-95 40 150 3000 PP 4-275 118 PP CMCITEM (Sweden) SCP-75 3 125 3000 He D MWM (Germany) n.d.a. n.d.a. n.d.a. n.d.a. n.d.a. n.d.a. ESD Engines (UK) RFK 4/20 20 10 750 Air PT Schlaich (Germany) v-160 n.d.a. n.d.a. n.d.a. n.d.a. PP SPS (Italy) V- 160 n.d.a. n.d.a. n.d.a. n.d.a. PP

I.T. Power (UK) n.d.a. 0.5 10 800 Air PT Stirling Dyn. (India) ST-5 3.8 5 650 Air PP

MTI (USA) Mod. I1 60 150 4000 H2 PD Mod. 111 112 n.d.a. 2800 HZ PP STM (USA) 4-120 20 110 1800 He D STI (USA) ST-5 3.8 5 650 Ais PP Sunpower (USA) n.d.a. 4.9 n.d.a. n.d.a. Ais D Akin Seiki (Japan) NS30A 30 120 1500 He D Mitsubishi (Japan) NS-03M 3.6 21 400 He D Sanden (Japan) n.d.a. 4 20 1000 N2 PT Sanyo (Japan) NS30S 30 150 1500 He D Toshiba (Japan) NS-03T 3 50 1300 He D D: Paper design; PT: Prototype; D:Demonstrated; PP: Preproduction; n.d.a.: No details available. Figure 11. Stirling engines developed by commercial companies.

EA Task X - Technologies for Small Wood Co-Generation Systems Page 19 Kockums AB, Stirling Engine Division, 20555 Malmo, Sweden. Until 1988 Kockums was involved in the US automotive Stirling engine programme, but when the funds were withdrawn Kockums terminated its US activities. Being a shipbuilder, Kockums now concentrate on 75 kW Stirling engines for submarine use, using diesel oil and liquid oxygen as fuel. However, it is in principle possible to convert the combustion system to use wood as fuel and has been tested by Kochums with different types of combustion systems. Kochums estimate a period of 5 to 10 years to develop a larger 250 kW, Stirling engine for biomass combustion to commercialization.

CMC c/o TEM - Malmo Research Centre, Nya Agnesfridsvagen 220, S-21579 Malmo, Sweden. This small company is in partnership with the University of Lund working on a 3 kW, hermetically sealed engine called SCP-75. The advantage of this design is that only the electric cables penetrate the crankcase, while a major disadvantage is that the crankcase must be designed to withstand the mean cycle pressure (125 bar). The engine is now at prototype stage and the company is focussing on British CHP-plants as their potential market using gas as fuel.

Schlaich Bergermann und Partner, Hohernzollernstrasse 1, D-7000 Stuttgart 1, Germany. Schlaich have licensed the Kochums V-160 engine to use in solar dish Stirling generator systems, and their aim is to make the engine more reliable and not to increase the engine output. The engine manufacturer Solo GmbH is refining the engine for mass production.

SES (former ESD) Engines Ltd., 51 Artesian Road, London W2 5DB, United Kingdom. SES aims at developing a Stirling engine at low cost, even at relatively low production levels. An innovative sealing mechanism and drive claims to increase both mechanical and sealing efficiency. The reliability will be improved and the engine will be simple to manufacture. SES is now testing a prototype and is well into the final design of the second generation of engines. The power range is 0.5-1000 kW,

IT Power, UK (adress unknown). IT Power built a 300 kW, single acting engine aimed at developing countries, but the cylinder head was damaged before testing. There has been no further work since 1988.

Toshiba Corp. & Consumer Products, Sales Division - Stirling Engines, 8 Shinsugita-cho, Isogo-cho, Yokohama 235, Japan. In building a 3 kW, gas fueled engine for domestic heat pump use, Toshiba is focussing on reducing costs and developing a suitable control system.

Mitsubishi Electric Corp., Central Research Laboratory, Stirling Engine Division, 1-1 Tsukaguchi honmachi S-chome, Amagasaki 661, Japan. The company is working on a 3 kW, domestic heat pump and focussing on control. Mitsubishi is trying to perfect a system that relies on changing both heater temperature and charge gas pressure.

Sanyo Electric Company Ltd., Air Conditioning Head Quarters, R&D Centre, 180 Sakata, Oizumi- Machi, Ora-Gun, Gunma, Japan. Sanyo is developing a 30 kW, natural gas fueled generator using a hairpin type tubular heat exchanger.

Technical University of Denmark @TU), Dept. of Energy Engineering, Building 403, 2800 Lyngby, Denmark in cooperation with Ansaldo V0lund R&D, Centervej 2, 6000 Kolding and REKA NS, Vestvej 7, 9600 Aars, Denmark. The Stirling engines developed in this project are designed specifically for small CHP-plants with direct combustion of biomass. The design of the engines is a 4-cylinder hermetic design with alternator integrated in crank casing. Two different sizes are being developed. A 36 kW engine with 21 % electrical

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 20 efficiency and a 150 kW engine with 26% electrical efficiency [9]. Both engines can be used in a modular construction.

&in Seiki Co. Ltd, 2nd R&D Centre, IWmni-nakane, Nkhio, Aichi 446, Japan. Aisin Seiki is working on reducing costs in a small free-piston engine for satellite applications and a 30 kWe helium-charged four cylinder engine. Among other things, Aisin Seiki is working with a wobble- plate drive and multi-stage seals on the piston rods.

Sanden Corporation, Stirling Engines Division, Iseaki Gunma 372, Japan. Sanden has been working with Stirling engines for more than 10 years. A 3 kW, domestic heat pump and a 30 kWe generator for incineration of solid industrial wastes have been built. A small demonstration engine for use in classrooms is being manufactured.

Stirling Thermal Motors Inc., 2841 Boardwalk, Ann Arbor, Michigan 48104, USA. When Ford's Stirling engine programme ended, Rolf Meijer founded STM in 1979. STM is now working with Detroit Diesel Company to develop general purpose commercial Striling engines using mass production techniques to reduce costs. STM has now established a Dutch company and a holding company for both the older companies, and is also working with a German company. STM is working on a 25 kWe helium charged engine with variable swashplate drive. The output is controlled by the angle of this plate, adjusting the piston stroke. The model name is STM 4-120.

Sandia National Laboratories (adress unknown). Sandia is testing a STM 4-120 engine in gas-fired operation and is preparing initial solar tests with this engine.

Cummins Power Generation, Inc. (adress unknown) Since 1991 Cummins of USA, the world's biggest manufacturer of diesel engines, has been developing a 5 kW, dish/Stirling unit.

Sunpower Inc., 6 Byard Street, Athens, Ohio 45701, USA. The Sunpower engines are mainly for use in space and military applications and have outputs less than 5 kW,, although a 25 kWe engine is being designed. Sunpower is working with the free piston engine system.

Mechanical Technology, Inc., Stirling Engine Division, 968 Albany Shaker Road, Latham NY 12110, USA. MTI has been doing research on Stirling engines for more than 10 years. The newest model is Mod. I11 with a power output of 112 kW,. The expected efficiency is 40%. The engine is close to be commercial.

Stirling Technology Corporation, Sales Division, 2952 George Washington Way, Richland WA 99352, USA. STC is designing a 25 kW, free piston engine for use with a solar dish Stirling system.

Stirling Technology Inc., PO Box 2633, Athens, Ohio 45701, USA. STI imported the Indian ST-5 engine, but is now not active.

Stirling Dynamics, India. The ST-5 engine developed by Sunpower was designed for local production in developing countries under the USAID programme. The first prototypes did not meet the production standards and funding stopped. In the late 1980s an Indian company and the Government of India developed the engine further by

EATask X - Technologies for Small Wood Co-Generation Systems Page 21 purchasing more than 100 ST-5s from the new company, Stirling Dynamics. Production has now ceased, but discussions with the Government may provide new funding.

Detailed information about the ST-5 engine can be obtained through [lo]

5.2 Stage of Development.

Although quite a large number of research institutes and companies are working with the Stirling engine the concept still has a long way to go. Only a few engines have been introduced to the market and none of them have been commercially viable. Some of the engines look promising with respect to price level and development stage. Unfortunately, no manufacturer can produce evidence that their engine is able to withstand constant operation the 25,000 hours of lifetime the Stirling engine is claimed to have. The engine is still not commercial. A summary of existing data are shown in Figure 12 taken from [4].

Company Engine Shaft Shaft Noise Specific Reliability power efficiency (dBA) Power MTBF &We) (%) (kWW (hr9 Kochums V-160 8 35-42 60 0.15 2900 4-95 40 35 1700 4-275 118 47 84 0.15 2000 CMC/TEM SCP 75 3 38

MTI Mod. I1 60 38.5 0.29 Mod. I11 112 40 0.23 STM 4-120 20 40 76 0.3 STI ST-5 3.8 11 0.02 2000 Aisin Seiki NS-30A 33 38 64-74 0.13 700 Mitsubishi NS-03M 3.6 34 60-70 0.06 Sanden 4 Sanyo NS-30s 30 37 84-96 0.12 Toshiba NS-03T 3 34 64-74 0.05

Figure 12. Selected data for Stirling engines.

5.3 Economy

As Stirling engines have only been produced in small numbers and not mass produced, the prices available on the market are far too high to be competitive. To illustrate this, the present production costs of the V-160 engine is 37,500 US$ or 4,690 US$/kWe, while forecasts show costs around 62-240 US$/kW, for commercially viable V-160 engines. These costs are based on an expected sale of between 1,000 and 200,000 units per year. In their investigation [4] has made some estimations on other expected production prices based on different numbers of produced units per year, but the V-160 seems to be the most competitive. See Figure 13.

EA Task X - Technologies for Small Wood Co-Generation Systems Page 22 The most promising engine on the market is perhaps the MTI model I11 engine mentioned above. Some preliminary estimates state the price to be 7,500 US$ or 67 US$/kWe, based on an expected sale of between 6,000 and 9,OOO units per year.

Maintenance costs are difficult to estimate at the present stage of development. The lack of data on reliability means that maintenance costs have not been established.1 It must be assumed, however, that maintenance costs will be considerably lower than those for internal combustion engines as oil changes or replacement of bearings will be needed only after extremely long intervals. The more cyclic regular pres- sure of the Stirling engine decrease bearing loads and the absence of valves, timing belts or cams eliminates the adjustments needed on internal combustion engines.

An Austrian investigation [ll] has compared the economy of a Stirling engine plant with that of a traditional steam plants (turbine or engine) and a hot air turbine. Some important economical results from the investigation are repeated in Figure 14.

0 0 4 8 12 ' 16 3 2 6 10 14 18 Production (Units/yr) (Thousands)

Figure 13. Unit price as a finction of production volume.

5.4 Feasibility.

5.4.1 Advantages and Disadvantages of the Stirling Engine. As the Stirling engines have had only few operating hours it is difficult to evaluate the reliability of the engine concept. Instead, this lack of reliability data is presented as a disadvantage. In other respects, the Stirling engine has potentials of being a good prime mover.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 23 System Steam Hot air Stirling turbine turbine engine output 100 100 100 Investment costs US$ 250,000 300,000 233,333 Spec. investment costs US$/kWe 2,500 3,000 2,333 Building costs US$ 33,333 20,833 8,333 Capital costs US$/yr 33,083 37,500 28,250 (8 %, 20 years) Reinvestment costs US$/yr 15,000 18,000 14,000 (8% of investment costs) Maintenance US$/yr 100,000 21,000 16,333 Fuel costs US$/yr 10,417 10,417 10,417 Annual costs US$/yr 158,500 86,917 69,000 Electricity costs US$/MWh, 396 217 173 Exchange rate: 1US$ = 12,O OS. Figure 14. Electricity costs with 4000 full load hours per year for small plants. Note: Prices include all plant.

The advantages of the Stirling engine are: The overall efficiencies are around 30%, which is comparabIe to that of the internal combustion engine and 3 times that of the steam engine. Efficiencies of 40% (fuel to shaft output) have been reported for natural gas. The value of the energy produced by a Stirling engine will usually be higher than that of a steam engine as also the electrical efficiency is higher. The part load efficiency is good. The noise level of the Stirling engine is low and the operation safe. The maintenance costs are expected to be low for various reasons. First, the working fluid is hermetically sealed inside the Stirling engine, making the ancillary equipment used in other types of engines unneccessary. Compared to i.e. a steam engine it is not necessary to apply condenser, oil separator, water conditioning plant, expansion tank, blowdown gear and the valve pumps and controls. Second, the hermetical sealing prevents the lubrication oil from entering the cylinders, thereby preventing contamination and heating of these. The use of oil filter and pump is then unnecessary and oil changes will only be needed at very long intervals. A wide range of fuels can be used as the combustion is external. The engine is expected to have a lifetime of 25,000 operating hours.

The disadvantages of the Stirling engine are: Only a few fuels have been tested (mostly LPG and natural gas). Problems are expected to emerge when fuels from wastes are to be used as these may cause problems with the heat exchangers. Soot, tar and particles are likely to reduce the efficiency of the heat exchangers, and as these are the keys to a good overall efficiency of the Stirling engine, more research must be carried out in this field. Until now only engines too small for CHP-plant use have been built. Until more experience has been obtained it is unlikely that any manufacturer will start making larger engines.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 24 Only few data on reliability and lifetime is available. For the Indian ST-5 engine no reliable performance data are available. For the 4-95 engine extensive field data was obtained, but the project was terminated as the operator saw now economical prospect for the technology. To raise the efficiency the heat exchanger temperature must be high. This may cause high temperature corrosion. Until now is has not been possible to find a way to make sealings sufficiently tight.

5.4.2 Necessary Innovations. The Stirling engine is still at a level where it is not commercially viable, but the advantages of the engine show great potentials. To convert these potentials into a reliable prime mover, research is at present aiming at the following: Improving heat exchangers as these are vital in increasing the overall efficiencies. Improving piston rod seals to withstand the heat and pressures present in the Stirling engine. Reduce production costs and increase reliability.

In the future the research must investigate the following problems to fit the Stirling engine to biomass fuels : The design of the heat exchangers must be refined to optimize their efficiencies, also after longer periods of use with unclean fuels.

The Stirling engine appears to have a great potential of becoming a feasible future energy producer; both installation and maintenance costs are expected to be low and the lifetime is considered to be good. Unfortunately, only few data on reliability are available. This is probably the most important disadvantage of the Stirling engine: Before any company will introduce a larger engine to the market, it is vital that data for long operation hours for the smaller engines are present to prevent expensive mistakes on larger engines. At present the largest engine on the market has an output of 118 kW,, hardly enough for any CHP-scheme. When i.e. 3 Stirling engines of 300 kW, can be coupled together the Stirling engine will be a hard competitor to existing technologies. Another necessary improvement to present designs is the sealings in the Stirling engine. The problems with making the sealings tight must be solved before the Stirling engine will be feasible.

5.5 Major Barriers for Technical Adaptability to Existing Energy Infrastruc- ture.

The Stirling engine is considered to be easy to adapt to the existing energy infrastructure as it can be used with almost any fuel. Based on wood the Stirling engine will have only few problems. It has about the same principal constructions as an internal combustion engine, so except from possible specialized parts, it does not require excessive maintenance. As the part load efficiency is good, the Stirling engine will be well suited for the existing energy infrastructure.

For the Stirling engine the efficiency is quite good, so it is not as important with the heating market as it is with the steam engine. The fact that a Stirling engine can use all kinds of fuels will make a choice for other schemes based on coal, oil etc. The expected quicker distribution because of this makes it easier to adapt it to the existing system.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 25 The indirectly fired gas turbine is based on the conventional gas turbine, but with the combustion chamber replaced by a heat exchanger. The heat is then produced by external combustion. The system is based on the open Brayton cycle gas turbine to generate power, while the gas turbine exhaust gas is as the fuel combustion air. The process can look as the example given in Figure 15. All of the components are standard, although the high temperatures in the heat exchanger have been known to cause problems.

HEAT EXCHANGER I 4-8

WOOO- - -3 - WASTE COMBUSTOR r 1 t5 \t GAS TURBINE

Figure 15. Indirectly fired gas turbine.

The first systems of this kind were commenced in the 1930's with ordinary metal heat exchangers, but now also sophisticated ceramic heat exchangers are being used to raise efficiencies.

6.1 Sites of R&D.

Only few R&D sites have been identified as the indirectly fired gas turbine is just a variation of the ordinary gas turbine, which is a known and proven technology. The research is therefore aimed at the heat exchanging system because the other components to a great extent are found mass-produced. The heat exchanging system consists of the heat exchanger and a system to clean the hot combustion products before entering the heat exchanger. This is done to protect the expensive heat exchanger from particles that would precipitate on the heating surfaces and reduce the efficiency considerably. The cleaning system is, however, also exposed to the hot combustion products and may therefore also be

EATask X - Technologies for Small Wood Co-Generation Systems Page 26 damaged by particles. With wood as fuel this system is yet to be proven, but a commercial system can be found for coal. The following researchers and manufacturers have been identified.

Hague International, 3 Adams Street, South Portland, ME 04106, USA. During the last three decades, Hague International has been working with the externally fired combined cycle concept, now using ceramic heat exchangers [12]. Hague was recently awarded a contract to build a 66 MW, power plant for Pennsylvania Electric based on an externally fired topping cycle added to an existing steam plant. Hague's ceramic heat exchangers eliminate the high temperature problems known from ordinary heat exchangers. In a combined cycle plant the ceramic heat exchanger is claimed to ensure up to 60% electricity efficiency [13]. For smaller plants (without combined cycle) the efficiency is about 18.4% [14].

CANMET, Energy, Mines and Resources Canada, 580 Booth Street, 7th Floor, Ottawa, Ontario, KIA OE4, Canada. CANMET has been working with financial analyses and engineering designs of indirectly fired gas turbine systems to find designs suitable for CHP-schemes in sawmills. CANMET is only looking at consequences of different systems and not working directly with development of heat exchangers etc.

KMW Energy Systems, 150 Oak Rd., London, Ontario, Canada N6E 3A1. KMW is working on small cogeneration system using a gas cycle and is now preparing for fabrication of a prototype. The information on this prototype is confidential at this time.

Vrije Universiteit Brussel, Dept. of Mechanical Engineering, Brussels, Belgium. Vrije Universiteit Brussels (VUB) has built a demonstration plant. The CHP-plant consists of an indirectly fired gasturbine fueled by a biomass fluidized bed gasifier designed for sawdust. The demonstration plant targets 500 kW,, and the commercial scale targets the range from 2 MW, to 5 MW,. If operated solely on biomass, electrical efficiency is limited to 13%, with an overall efficiency of 65%, because of the maximum allowable temperature in the metallic heat exchanger. To achieve higher performance the performance the system is equipped with a dual-fuel option for firing natural gas to boost temperature. The dual-fuel option raises the temperature to 100OoC,greatly improving electrical efficiency to 23 % with an overall efficiency of 69%. By injecting water peak electrical efficiences of up to 30% are aimed at 1151.

Also other concept are seen. Among these is a system using several ordinary small metallic gas turbines (turbo chargers) and heat exchangers at their maximum operating temperatures. By reheating the air after each step efficiencies comparable to those of the high temperature ceramic heat exchanger are obtainable.

6.2 Stage of Development.

As mentioned above all components but the heat exchanger system are standard. The research is therefore concentrated on these components. Also the gas turbine itself is receiving some attention as most gas turbines are dimensioned for the use of either natural gas or coal firing, and the combustion chamber of the gas turbine must therefore be adapted to use hot air. At present only few experiences on heat exchangers exposed to hot combustion products are available.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 27 6.3 Economy.

Unfortunately, only little information is found on the economical side of indirectly fired gas turbines. A Canadian project [16] has looked into the problems and economy of an indirectly fired gas turbine for sawmill applications. It treats 4 different fuel mixes, namely 100% wood, 100% natural gas, 27% natural gas and 50% gas. The Belgian project at VUB has economical calculations for a full scale plant, based on the demonstration plant, with a power output of 1.8 MW,

6.3.1 Canadian investigation The Canadian investigation looks at the economical impacts of four different fuels. Some results will shortly be presented here.

System Case 1 Case 2 output kwe 530 972 Investment costs US$ 2,398,438 5,9 14,063 Spec. investment costs 4,525 6,084 ll Maintenace costs US$/yr 91,211 91,211 Exchange rate: 1US$= 1.28 Can.$. Case 1 is system with ordinary heat exchanger. Case 2 is system with ceramic heat exchanger (10 times more expensive than the ordinary heat exchanger). Figure 16. Electricity costs for indirectly fired gas turbine based on 4000 full load hours per year. Note: Prices include all plant.

As basis the investigation uses a Kawasaki M1A-01 gas turbine rated at 1122 kW, output at full load. When solely natural gas is being used 1122 kW, is the output with a turbine inlet temperature of 900°C. When solely wood as fuel the output is decreased to 530 kW, due to temperature limitations in the heat exchanger (760°C). When dual-fuel cases are considered the wood combustor raises the temperature to 760°C and the natural gas is combusted directly to raise the temperature to 900°C. Auxiliary systems reduce power output of these intermediate systems to 972 kW,. The straight gas fired system is reduced to an ordinary directly fired gas turbine, thereby reducing installation costs considerably. The economical impacts of the system is difficult to compare with other systems. First, the calculations are based on Canadian conditions and, second, the gas turbine system is neither based on small but several turbo chargers as explained page 27, nor on ceramic heat exchangers to raise the turbine inlet temperature. The power output is more than halved and the efficiency is reduced likewise. In Figure 16 results taken from [16] and estimated values if the heat exchanger is replaced by a ceramic one are presented. For case 2 the heat exchanger price is 10 times that of case 1 1131. This system is hardly competitive.

6.3.2 Belgian investigation In [15] economical data are given for both a 500 kW, demonstration plant and a 1.8 MW, system study based on experiences from the demonstration plant. The economic data are listed in Figure 17.

EA Task X - Technologies for Small Wood Co-Generation Systems Page 28 For both plants it is possible to increase the power output considerably by adding water to the hot products, although it does not increase electrical efficiency very much. Adding water makes it more

System Demonstration plant Planned Commer- cial Plant Electrical output kwe 5 80 1800 Investment costs Gas turbine US$ 950,250 1,093,000 Gasifier and peripherals US$ 1,026,270 1,177,000 HT heat exchanger US$ 532,140 572,000 Ductwork US$ 228,060 168,000 Combustor US$ 228,060 437,000 LT heat exchanger US$ 152,040 202,000 Civils, electric and other US$ 684,180 1,227,000 Total US$ 3,801,000' 4,876,0001 Spec. investment US$/kWe 6,553 2,709

ECU = 1.267 US$, 1996 rates 1) prices inciude overhead difficult to use the gasturbine in a CHP-system since it is not possible to extract as much energy for heating as with a dry setup. Figure 17. Prices for CHP-plants of direrent size.

The 500 kW, demonstration plant is based on the Volvo VT600 gas turbine adapted for external firing. The gas produced from the fluidized bed gasifier heats up the compressed air to 850°C. The temperature of the compressed air is raised to 1000°C by a topping combustor using natural gas. As with most gasifier based CHP-plants the system is not technically suitable for daily startups. Shut downs are considered feasible during weekends and summertime only. Successful testruns with this demonstration plant has been made. It is not clear why a gasifier has been chosen for producing energy. It could be speculated that a more reliable and simple system could be achieved using a more conventional combustion system instead.

6.4 Feasibility.

6.4.1 Advantages and Disadvantages of the Indirectly Fired Gas Turbine. The indirectly fired gas turbines can be divided into two main groups: The simple system described by CANMET (page 27) and the advanced combined cycle plant, Hague International is working with. Hague designs plants not smaller than 50 MW,, while the simpler systems are better suited for small scale CHP- schemes, and therefore more relevant to this investigation. Error! Reference source not found. illustrates the effect of introducing a ceramic heat exchanger to the simple system. Although achieving higher efficiency, this plant design is not economical competitive. In 1995 Hague will introduce the ceramic heat exchanger on the Danish Harboore gasifier, designed to about 1.5 MW,. If this down scaling

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 29 of the Hague system is successful, disadvantages as poor down load efficiency and too high installation costs can very well be eliminated. At this stage the advantages and disadvantages of the simple indirectly fired gas turbine can be summarized as below. Advantages: Most parts in an indirectly fired gas turbine plant are standard, mass-produced components. If natural gas or coal is used as fuel all components are standard. When used as booster for using fossil fuels, the residues from biomass and fossil fuels are kept apart and can be utilized as fertilizer and for cement production, respectively. When mixed in a combustion process the residue must be treated as industrial waste. If the temperature in the gas turbine inlet can be increased to that of directly fired gas turbines (by the use of ceramic heat exchangers), the efficiency is equal to that of ordinary gas turbines.

Disadvantages: With standard metal heat exchangers the gas turbine inlet temperature is lowered, leading to lower efficiencies. As relatively high pressures are often found in heat exchangers, ceramic heat exchangers must be reinforced. Such heat exchangers have not yet been tested with wood as fuel. The heat exchanger is very large. In existing plants the heat exchanger is comparable to the boiler in size although the cost is reported to be as less as 14%of the total investment [15] if ordinary metallic heat exchangers are applied. The particle cleaning system must work at high temperatures. An American company has introduced a ceramic cleaning system to be used with their ceramic heat exchanger. Here the particles precipitates on ceramic rods at app. 1500°C. The rods are then periodically electrically heated, causing the accumulated deposits to detach and fall off. It might cause problems to regulate the gas turbine as these are designed to be controlled by the amount of fuel supplied. By the use of a heat exchanger this process is expected to be more complicated.

6.4.2 Necessary Innovations. The indirectly fired gas turbine is almost ready for introduction to the market. The main area to set in with innovations is the gas turbine. Gas turbines for stationary use are designed to run on an internal com- bustion of a clean fuel. When hot air, and not hot combustion products, is used, the gas turbines must be adopted.

The general feasibility appears to be good as components necessary to make indirectly fired gas turbines with acceptable efficiencies are already commercial. With respect to the economy this cannot be estimated yet. It appears that the gas turbines on the market will make the lower power output limit.

6.5 Major Barriers for Technical Adaptability to Existing Energy Infrastruc- ture.

No particular problems with respect to the technical adaptability can be seen. For base load applications the efficiency decreases, and this must be considered when evaluating the turbine in the existing energy system.

EATask X - Technologies for Small Wood Co-Generation Systems Page 30 7. Direct Fired Pressurized Gas Turbines.

One representative for this technique is the pressurized downdraft combustion. In a pressurized down draft reactor wood chips or waste is fed at the top of the reactor and onto the bed, usually consisting of sand or gravel. Heated air flows through the woodchips, dries the top layer, devolatilizes the next layer of wood chips and oxidizes the layer on top of the bed material. The pyrolyzed gases combust with the air and char particles entrained by the air flow are trapped and burned in the gravel bed. The hot combustion products are then led to a gas turbine that generates power. As the temperature of the combustion products are usually higher than the maximum allowable gas turbine inlet temperature, the combustion products are mixed with cooler air. A schematic diagram of a laboratory plant can be seen in Figure 18, taken from 1171.

7.1 Sites of R&D.

Three sites of research and development have been found:

Department of Mechanical Engineering, University of Wisconsin, Madison, WI 53706 USA. The department has been working with the pressurized down draft combustion technique since 1983. In 1991 experiments with a 300 kW, gas turbine were made and after that the department has made some preliminary studies of a 3.5 MW, system using a modified Allison 501-KB turbine.

t- EWS7 Figure 18. Gravel bed gas turbine downdraft gasifier system.

Aerospace Research Corporation, 5454 Aerospace Road, Roanoke, VA 24014, USA. ARC owns the gas turbine test plant run by RBS Electric of Red Boiling Spring. The gas tuihe is llison T-56 aircraft turbine (the industrial version is 501-K) coupled to a 3 MW, generator.

Power Generating Incoporated, Att: Robert L. MeCarroll & William E. Partanen, 2501 Parkview Drive, Suite 500, Fort Worth, Texas USA 76102-5824. PGI is developing a pressurized direct-fired gas turbine power system designed to operate on solid fuel. PGI uses a Garrett gas turbine coupled to a generator ranging from 500 kW, - 3,5 MW,. This system is described i paragraph 0.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 31 7.2 Stage of Developmen,.

The stage of development appears to be quite high as demonstration plants have been built a couple of places. There are some problems with obtaining steady operations, but nevertheless larger plants are being planned. Aerospace Research Corporations claims that their system is now ready for a commercial version as of June 1993.

7.3 Economy.

Estimates on economical aspects are sparse. In [17] estimated costs for a 3.5 MW, system are calculated on basis of the 300 kW, system now in operation. The costs of the combustor were obtained by multiplying the costs of the present combustor with the increase in cross sectional area. The results are shown briefly in Figure 19.

OUTPUT h4Wp 3.0

~~~~ ~ CAPITAL COSTS Chip feeder US$ 180,000 Gravel bed combustor US$ 150,000 Turbine and generator US$ 3,200,000 Baghouse US$ 280,000 Waste heat boiler US$ 750,000

Total US$ 4,560,000 Spec. costs US$/kW, 1,300

~ ~ ~ ANNUAL OPERATING COSTS

Labor US$/yr 1 50,000 Maintenance US$/yr 160,000 Taxes and insurance US$/yr 180,000 Fuel US$/yr 570,000 Total US$/yr 1,060,OOO Electricity costs US$/MW,h 88

Figure 19. Summary of costs for pressurized down draft combustion system based on 4000 full load hours pr. year. Note: Prices include all plant.

Also CADDET has given some values of which some are found in Figure 20 [ 181. Please note that the figures are based on a future setup where the Allison gas turbine has been replaced with a larger turbine able to withstand higher inlet temperatures. Note also that the costs are only for the gas turbine. If the costs of combustor, feeder etc. are 43% of that of the gas turbine (as it is in Figure 19) the total costs will be 5,130,000 US$ or 855 US$/kW,h.

EA Task X - Technologies for Small Wood Co-Generation System Page 32 Capital costs US$ 3,609,000 spec. costs US$/kWe 600 Operating costs US$/yr 638,208 5

Figure 20. Projected economic data for G.E. LM1500 gas turbine. Note: Prices only include the gas turbine itself.

7.4 Pressurized Direct Fired Gas Turbine. The PGI Concept.

Ff-0It8

Figure 21. The PGI prototype.

The PGI system is very much like traditional direct fired gas turbines but fired on biomass instead of high- end fossil fuels, i.e. light oil or natural gas. The key to success of any solid fuel fired gas turbine is the ability to protect the gas turbine from impurities in the dirty fuel. Description of the technique can be seen in [18].

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 33 The System patented by PGI will initially run on dry (less than 10 % moisture) white wood (no bark) pulverized to 1/8" prior to firing and later coal with a low content of sulphur, both fuels containing small but not unimportant impurities when fired directly into the turbine. Research done on PFBC- and DCFT- plants have shown, that it is possible to develop hot gas clean-up systems that can solve this problem. PGI has chosen an so called axial centrifuge cyclone delivered by Dyna-Therm Corp., which will have a particulate removal efficiency of 100%down to particle sizes of five microns and 99.6% efficiency down to three microns. This is within the acceptable particulate limits specified by most gas turbine manufac- turers.

The gas turbine used for the prototype is delivered by Garrett (model IE831-800) rated at 550 kW with 73 bar inlet pressure and 935°C inlet temperature. The prototype system is expected to bum approximately 400 kg of dry wood fuel per hour. The Garrett turbine was chosen on its ability to accommodate an off-base pressurized combustor as needed in the PGI system.

The ambient air supplied by the compressor is mostly used to cool the high temperature combustion gasses to avoid damage to the turbine blades. Approximately 25% of the air is used for combustion and 75% used for cooling.

Overall efficiency in CHP operation is said to be in excess of 70%. It should be noted that the exhaust products are at about 500°C when leaving the turbine, making them very suited for co-generation. The prototype, shown in Figure 21, is supposed to be running since mid 1993 and is scheduled for three years of operating, before a commercial model will enter the market.

7.4.1 Stage of development. In 1993 PGI announced the system to be commercially available within three to four years, i.e. mid 1996/97.

7.4.2 Economy. There is no information regarding costs on a commercially available CHP-plant. The only cost figures is the price for the demonstration plant, which is estimated at US$ 5.1 million for the demonstration plant fitted with the 550 kW Garrett gas turbine.

7.5 Feasibility.

The main advantages and disadvantages are mentioned below.

7.5.1 Advantages and Disadvantages of Pressurized Down Draft Combustion. Advantages: The installation costs appear to be reasonable. The producers claim that the gas produced is very clean. The pressurized down draft principle offers a way to combust wood fast enough and with a content of ash so low that it can drive a gas turbine directly. Upscaling is simple as a larger plant only requires a larger combustion chamber and a larger gas turbine.

Disadvantages:

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 34 Only few plants are in operation and these have only had few operating hours. The power output is very sensitive to operating conditions. Tests have shown that for normal combustion chambers the pressure drop is too large for combustion chambers used with a 300 kWe gas turbine. The lower limit for power output is then expected to be at least 300 kWe. The systems found are based on aspen wood chips or sawmill dust as fuel. No results for tests with a wide range of fuels have been found.

Unfortunately, neither reliable data for efficiencies nor maintenance costs have been found.

As with the indirectly fired gas turbine most components are standard. The main R&D effort has been put into design of the combustion chamber, usually with primary and secondary combustors. For some of the manufacturers this design problem appears to have been overcome. At least one producer is ready to put a sawdust fired system on the market. Apart from the lack of data on reliability, maintenance costs and perhaps unforeseen fuel problems, the pressurized down draft combustion process appears feasible.

7.5.2 Advantages and Disadvantages of Pressurized Direct Fired Gas Turbine. The main advantages and disadvantages of the pressurized direct fired gas turbine are mentioned below,

Advantages : By using direct firing, there is no costs associated with construction and maintenance of a pressurized steam ducting system. A standard gas turbine can be used. No errosion, corrosion or deposition on turbine blades due to effective hot gas clean-up sytem. The residues from the cyclone can be utilized for fertilizer.

Disadvantages: Only planned fuel is white wood and coal with a low content of sulphur.

Unfortunately, neither reliable data for efficiencies nor maintenance costs have been found. Concerning the pressurized direct fired gas turbine most R&D-effort has been put into fuel feed valves, Erosion, corrosion, deposition, hot gas ducting, gas turbine manifolding and sytem control.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 35 7.6 Major Barriers for Technical Adaptability to Existing Energy Infrastruc- ture.

As efficiencies and part load behaviour have not been found it is difficult to evaluate if these things might cause any problems. Otherwise no problems seem apparent as to adaptability to the existing energy infrastructure.

It is crucial for the adaptability of this technique that the claimed high efficiency in cleaning the hot gas is accurate. .

For base load applications none of the pressurised direct fired gas turbines are suited as the part load efficiency of the gas turbine is bad, and this must be considered when evaluating the turbine in the existing energy system.

IEA Task X - Technologies for Small Wood Co-Generation Systems Page 36 8. Economical comparison of different technologies

Economical comparisons will be done between 4 different small scale technologies for cogeneration. They will be compared for equal sizes of maximum heat output assuming the heat was supplied to the same district heating network. First it is clarified, how the economical optimum size of a CHP-plant (Combined Beat and Power plants) can be determinated for a given market of heat demand. When the economical optimum size is determined, detailed calculations will made for each of the technologies on the economical optimal size.

8.1 Introduction In the proces of collecting information for this investigation it has proven to be quite difficult to obtain reliable data on economical figures, i.e. cost of a stirling engine. There are many reasons for this. First of all is only the proven steam turbine technology commercially available on the market, and second will the cost of both the stirling and steam engine rely heavily on how many engines will be produced per year and to which degree standard automotive parts can be integrated in the commercial design of these engines.

Instead of trying to estimate how much a engine, boiler, flue gas handling etc. will cost when commercially available, it will be calculated what the annual production expenses are, without capital costs and before heat sale. In doing so one can eliminate the uncertainties associated with estimating costs for technologies not yet developed, thus giving more reliable figures. Therefore is the cost of the actual CHP-plant, Le. buildings, electrical installations, prime mover etc., not included in the calculations.

The annual production expenses without capital costs and before heat sales allows a comparison to be made with other existing technologies for producing district heat. The larger the difference between the annual production expenses on a wood-fired CHP-technology and production expenses on other competing technologies, i.e. natural gas, the more economically viable the CHP- technology is. The annual production expenses also gives the opportunity to compare the performance of the individual technologies. If for example a stirling engine-based CHP-plant is more expensive than a steam turbine plant, the stirling engine plant can still be the best technology if it can generate lower annaual production expenses.

8.1.1 Definition of economical optimum size The economical optimum size can be defined as the size of the CHP-plant, which results in the lowest total cost when covering a defined heating market with all the necessary amount of heat to@@ll the complete demand.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 37 8.2 Duration graph

Basically it is assumed that the heat demand over the year can be described by the following graph, named the duration graph.

0 '1 I""1 I ,'I 11'' -r~-i-TTTI i-T- '-TTTT' 0 1000 2000 3000 4000 5000 6000 7000 goo0 i'"''rr Figure 22. Duration graph showing a typical variationY in heat demand during a year. In the graph the required power output for the supply to the heating network is plotted from left to the right with the values in descending order.

The area below the graph in Figure 22 represents the annual heat demand (in MWh). The shape of the above shown duration graph is correlated to common Danish weather conditions.

Approximately 40 % of the yearly heat demand is assumed to be independent of the outdoor tem- perature. This part of the energy is used for heat losses from the network and for hot tap water. The remaining app. 60 % of the demand is proportionate to the difference between the in- and outdoor temperature.

The duration graph can be described mathematical by linear equations derived from following fixed coordinates: Oh 400 h 4.400 h 6.500 h 8.760 h 3.2*R+K 2.13.R+K 1.13*R+K K K

Figure 23. Approximation of duration graph by linear equations Where: R= Average demand for space heating [MW] K = Average demand for network loses and tap water [MW].

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 38 8.3 Introduction

In the following is assumed that the complete energy plant consists of two units:

The CHP-plant for the base load production An oil fired boiler for peak load production

Together the two plants are producing all the necessary heat to satisfy the need for energy as described by the duration graph. All electricity produced at the CHP-plant is assumed to be sold at a fixed price to the public electricity grid.

If the introduction of CHP-production shall make sense, it is apparent that both technical and economical circumstances must encourage to as much as possible CHP-production at the defined heating market. For instance must the value of electricity be significantly higher than the value of heat.

Before determination of the optimum size, it is necessary to make assumptions for the below mentioned variables:

Cost of fuels Electricity sales price to public grid Electric and heat efficiency of the plant Cost of labour for operation Maintenance costs The CHP-plants capability to modulate the electric and thermal load. 8.4 Example

The easiest way to illustrate the procedure in the calculation is by means of an example.The determination is done in five steps:

1) First is a certain size of a heating market defined and described by a duration graph. 2) Then economical calculations for a number of different sizes of CHP-plants in a range of 20 - 100%of the peak load are made. 3) For each size of CHP-plant must then be calculated: 0 How much the CHP-plant can cover of the total heat demand 0 How much the oilfired boiler must cover of the total heat demand (the residual part). After that follows a calculation of annual expenses without capital costs for each size of 4) CHP-plant in the analysis, as shown in Figure 24. 5) Finally are the results for heat sales prices for different sizes of CHP-plants plotted in a graph to illustrate the dependency of the size.

Hence, the calculation of the heat sales price without capital costs is done by:

- Annual production expenses Heat sa'es price(withour capital co.si,s) - Annual heat production

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 39 Annual Expenses before income from heat sale wtihout capital costs. Expenses Fuel costs (CHP-plant) + Fuel costs (oil boiler) + Labour for operation + Maintenance + Power consumption Income - Electricity sales = budproduction expenses (before heat sales - without capital costs) Figure 3. Method for calculating annual production expenses

Please keep in mind, that the price calculated by the above method express the total costs for supplying the whole annual demand of heat to the defined network.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 40 9. Economical calculations

9.1 Definition of heating market

In the economical analysis it is assumed that heat must be supplied to a 3120 kWu, heating market, corresponding to approx. 120 houses under danish weather conditions. The heating demand is assumed to be described by the duration graph shown in Figure 22.

9.2 Choice of individual technology for economical calculations

In the following it will be argumented how the data for the economical calculations have been chosen for each technology considered in this survey 1. Steam turbine 2. Steam engine 3. Stirling engine 4. Indirectly fired gas turbine

The direct fired pressurized gas turbine is not included in the economical calculations as there are only 1 or 2 companies involved in developing this technology and it furthermore seems to be the technology with the least potential to become a commercial product in the near fututre.

The main criterias for selecting the specific ‘product’ are: Commercially available or at least tested prototype Maximum output dose to 2 MWh

9.2.1 Steam turbine The data for the steam turbine has been taken from [3] describing a 620 kW, wood waste fired steam turbine plant. The electrical efficiency is 15 % and the overall efficiency is 81 % .

9.2.2 Steam engine In [6] can be found data on the DanSteam engine. The newest data from [7] gives an electrical efficiency of 17 % and an overall efficiency of 86 % .

9.2.3 Stirling engine The stirling engine project at the Technical University of Denmark has run tests on their prototype engine in 1997. Data from [9] gives an electrical efficiency of 26% and an overall efficiency of 90%.

9.2.4 Indirectly fired gas turbine Data from Vrije Universiteit Brussels [15] reports an electrical efficiency of 13 % with an overall efficiency of 65 % achieved in test-runs with a prototype plant. According to [ 151 higher efficiencies can be achieved by using natural gas topping combustion. Those figures have not been used in this report as it is only the aim of this investigation to look into wood chip fired technologies.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 41 9.2.5 Overview Electrical efficiency [ %] Heating efficiency Overall utilization [%I [%I Steam turbine 15 66 81 Steam engine 17 69 86 Stirling engine 26 64 90 Ind. fired gas turbine 13 52 65 Figure 25. Eflciency data used for economical calculations

9.3 Assumptions

9.3.1 Prices Exchange rate [DKK/US$l 6.00 Heating market to cover, maximum production rate [kwtberma~l 3 120 Lower heating value, wood chips 45 % moist. [GJ/t] 9.37 Price wood chips [US$/GJ] 6.00 Gasoil lower heating value [GJ/m3] 35.60 Gasoil price [US$/GJ] 14.49 Electricity sales price [US$/kWh] 0.05 Power consumption ratio [kme/Mmthl 19.00 Power consumption price [US$/kWl 0.069 NB. Prices quoted are acl. dznish energy taxes and VAT

9.3.2 Operation and maintenance To calculate the need for manpower to operate the plants figures from a danish survey of wood chip fired district heating plants [191 are being used as a 'best available guess'. Specific manpower need is : 0.55 man/MWU, Time-ratio spent on operating plant (Le. not time spent on net-installations): 0.7 Wages for personnel (including insurance): 50.000 US$/yr Expenses for personnel : 0.55*MWU,*50.000*0.7[US$/yr]

To calculate the expenses for operation of the CHP-plant thefollowing empirical formula is used Expenses for Operation & maintenance: 0.0278 [US$/kw]

9.3.3 CHP-plant data In order to have a reasonable economy heat-storage must be available to a CHP-plant. It has been assumed that the CHP-plant is equipped with a water-tank operated with a 40 "C temperature difference. This gives the following heat storage capacities,Figure 26.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 42 Plant size Heat storage capacity Percentage of Max. thermal Volume at Energy storage max. demand ouput AT=40 "C capacity [GJ] [%I [kWtkll [m31 20 624 120 20 40 1248 240 40 60 1872 360 60 80 2496 480 80 100 3 120 600 100 Figure 26. CHP-plant data used for calculations

9.3.4 Modulation of CHP-plant It is assumed that the modulation capacities of the different CHP-plants are in the range 25-1 0%. It is furthermore assumed that the heating and electrical efficiencies are constant troughout that range. This is not a valid assumption for all types of CHP-plants, but the assumption is made for simplification.

When the heating demand - taken as a monthly average - is lower than 25 % of maximum thermal output (the minimum load) it is assumed that the CHP-plant is taken out of operation and the heat is supplied by the oilfired boiler.

Jan. Feb. Mar. Apr. May June July Aug. Sep. Oct. Nov. Dec. 5843.7 5389.8 5052.8 3933.1 3075.5 1445.5 1493.7 1493.7 2234.8 3421.6 4315.8 5300.0 Figure 2 7. Monthly heating demand [GJ/month]

It can be seen from Figure 26 and Figure 27 that only plants sizes 80% and 100%have to be shut down during the summer period.

Plant size. Percentage of 25 % of maximum thermal Period out of operation maximum heating demand output (minimum load) [%I [GJ/month] 20 405 None 40 810 None 60 1215 None 80 1620 June-August 100 2025 June-August Figure 28. Operation periods for different plant sizes.

9.4 Calculation of operational pattern

For the purpose of calculating the annual production of heat and electricity and the annual consumption of gasoil and woodchips the software KV-Design version 4.14 has been used. X- design (KV = CHP) optimizes the heat and power production over the year based on restrictions entered by the user, i.e. heat storage capacity, electricity price variations etc.

Because it has been assumed that the electricity sales price to the public grid is uniform throughout the day (and the week) the most relevant information is the fraction of heat produced respectively by the CHP-plant and the oilfired boiler. From this information it is possible to extract information on electricity production and other data neccessary to perform the economical calculations.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 43 Plant size. Percentage of Fraction of heat produced by Fraction of heat produced by maximum heating demand CHP-plant oilfired boiler [%I [%I [%I 20 44,6 55,4 40 773 22,5 60 94,8 5 32 80 89,8 10,2 100 89,8 10,2 Figure 29. Results porn calculations with KV-Design

In Figure 29 and Figure 30 the results are shown. Figure 30 indicates that 60 % of the duration graphs peak load value is a proper choice for a CHP-plant.

16

--b- Ind. fired GT - * - Steam turbine ---Steam engine Stirling engine

0 20 40 60 80 100 Plant size. Percentage of maximum heating demand ph]

Figure 30. Annual production expenses as a function of plant size

Although it seems that larger plant sizes than 80% of maximum heating demand will have the same annual production expenses this is not true. Larger plants will have higher production expenses because of increasing substitution of the wood chip fired CHP-plant by the oilfired boiler. This is due to the increasing number of periods, where the demand is below 25% of the maximum output. But since this is a 'stepwise' function, it is not clear on Figure 30 as the largest plant size considered is 100% of maximum demand.

9.5 Discussion

By the subsequent considerations it may be realized, why the shape of the graph for annual production expenses has a tendency to reach a minimum value between the upper and lower limits.

If the CHP-plant gets small in relation to the peak load, the plant may get many full load production hours, but still it will only be able to deliver a minor part of the complete demand of heat in during the winter. In that situation the residual heat demand must be served by the more costly heat

IEA Task X - TexfmoIogies for SmaIl Wood Co-Generation Systems. Economical calculations. Page 44 production at the oilfired boiler. The final result will be high overall heat production cost. This explains why the heat production expenses are high for smaller sizes of plants.

If the CHP-plant on the other hand gets large, the minimum load of the CHP-plant will exceed the demand in the summer period. In that case it will be necessary to close down the CHP-plant completely in the summer period and instead turn on the oilfired boiler (another solution could be to blow off the surplus of heat in the summer period, but that will normally neither be economically feasible). Therefore also larger plants will result in higher oil consumption, so despite a large plant is capable to produce more electricity, it will - with the above presumed energy price-relation - not be attractive to make a plant to large.

When capital costs are included in the picture, the conclusion may be changed, but: For most technologies, a large plant size concept will cost relative less than a smaller version of same concept (but the total capital costs are still increasing, when the size becomes larger).

For this reason the 60 % of peak demand has been used in the economical comparison in this report. This was done despite it from a scientifically point of view would have been appropriate to make a recalculation with origin in the key data for the four technologies. It was estimated that the error caused in not doing so was of small order compared to other estimates in the survey.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 45 10. Optimum size of CHP-plant

Because this investigation focuses on a CHP-plant to cover a given heating market, CHP-plants based on each of the four technologies will have the same maximum heat production rate, despite the infeed rate varies from technology to technology. This means that each of the technologies will have the same number of operating hours as they, from a 'heat production' point of view are identical. The infeed rate and electricity production though will vary greatly because of the varying electrical and overall efficiencies.

10.1 General data

The general data can be found in the various tables presented in this survey, but they are presented here for reasons of clarity.

Assumptions Heating market to cover, maximum production rate BWthermal] 3120 Plant size. Percentage of maximum heating demand [%I 60 Lower heating value, wood chips 45% moist. [GJ/t] 9.37 Price wood chips [US$/GJ] 6.0 Gasoil lower heating value [GJ/m3] 35.6 Gasoil price [US$/GJ] 14.49 Heat sales price [US$/GJ] 12.3 Electricity sales price [US$/kWh] 0.05 Percentage heat produced on CHP [%I 94.8 Percentage heat produced by oilfired boiler [%I 5.2 Power consumption ratio [krn,/MWh,l 19.0

Figure 31. General data used for economical calculations

EATask X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 46 10.2 Steam turbine

Plant Data Unit Maximum heat production rate W/Sl 1872 Electrical efficiency [%I 15 Heating efficiency [%I 66 Overall Utilization [%I 81 Infeed rate [kJ/sl 2836 Maximum electricity production rate [kWI 425 Production period Wyrl 6048 Operation Heat production @J/Y rl 43040 Electricity production [Wyrl 2576 Woodchip consumption FJ/Yrl 61821 Gasoil consumption [GJ/Y rl 2487 Economy Expenses Woodchips [ 1000 US$/yr] 370.9 Gasoil [lo00 US$/yr] 36.0 Operation & maintenance [lo00 US$/yr] 71.6 Wages for personnel [ 1000 US$/yr] 36.0 Power consumption [lo00 US$/yr] 15.6 Total expenses [loo0 US$/yr] 530.2 Income Electricity sales [ 1000 US$/yr] 128.8 Result Annual production expenses (without capital costs) IUS$/GJI 9.33 Figure 32. Steam turbine calculation results.

Page IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. 47 10.3 Steam engine

Plant Data Unit Maximum heat production rate WSI 1872 Electrical efficiency [%I 17 Heating efficiency [%I 65 Overall Utilization [%I 86 Infeed rate WSI 2713 Maximum electricity production rate [kWI 46 1 Production period Ilhr/yrI 6048 Operation Heat production PJ/Yrl 4304C Electricity production [MWWyrI 2792 Woodchip consumption [GJ/yrI 59133 Gasoil consumption [GJ/yrI 2487 Economy Expenses Woodchips [ 1000 US$/yr] 354.8 Gasoil [ 1000 US$/yr] 36.0 Operation & maintenance [ 1000 US$/yr] 77.6 Wages for personnel [lo00 US$/yr] 36.0 Power consumption [ 1000 US$/yr] 15.6 Total expenses [ 1000 US$/yr] 520.1 Income Electricity sales [ 1000 US$/yrj 139.6 Result Annual production expenses (without capital costs) IUS$/GJI 8.84 Figure 12. Steam engine calculation results.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 48 I 10.4 Stirling engine

Plant Data Unit Maximum heat production rate WSl 1872 Electrical efficiency [%I 26 Heating efficiency ["/.I 64 Overall Utilization [%I 90 Infeed rate WSl 2925 Maximum electricity production rate [kWI 76 1 Production period WYrl 6048 Operation Heat production PJ/Y rl 43040 Electricity production [MWh/yr] 4604 Woodchip consumption [GJ/yrI 63753 Gasoil consumption [GJ/Y rl 2487 Economy Expenses Woodchips [lo00 US$/yr] 382.5 Gasoil [lo00 US$/yr] 36.a Operation & maintenance [ 1000 US$/yr] i28.a Wages for personnel [lo00 US$/yrj 36.a Power consumption [lo00 US$/yr] 15.6 Total expenses [ 1000 US$/yr] 598.2 Income Electricity sales [1000 US$/yr] 230.2 Result

Annual production expenses (without capital costs) ICTS$/GJI 8.55 Figure 13. Stirling engine calculation results.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 49 10.5 Indirectly fired gas turbine

Plant Data Unit Maximum heat production rate [kJ/sl 1872 Electrical efficiency [%I 13 Heating efficiency [%I 52 Overall Utilization [%I 65 Infeed rate [kJ/Sl 3600 Maximum electricity production rate [kw1 468 Production period chr/Y rl 6048

Heat production 43040 Electricity production 2833 Woodchip consumption 78465 Gasoil consumption 2487 Economy Expenses Woodchips [ 1000 US$/yr] 470.8 Gasoil [IO00 US$/yr] 36.0 Operation & maintenance [lo00 US$/yr] 78.8 Wages for personnel [ 1000 US$/yr] 36.0 Power consumption [ 1000 US$/yr] 15.6 Total expenses [lo00 US$/yr] 637.2 Income Electricity sales [lo00 US$/yr] 141.7 Result Annual production expenses (without capital costs) [US$/GJI 11.51 Figure 14. Indirectly Bred gas turbine calculation results.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 50 /GJ,,, JZ&LA&'' 10.5.1 Comparison of annual production expenses YG5 &&&-& CHP-technology Steam turbine Steam engine Stirling engine Indirectly fired GT Annual production 9.33 8.84 8.55 11.51 expenses [US$/GJ] Figure 36. Annual production expenses for plant size 60% of maximum heating demand.

From the calculations and the overview in Figure 36 it is clear that a CHP-plant based on the Stirling engine technology would be the most feasible option. The Stirling engine has the highest electrical efficiency and the highest overall utilization, so it is not surprising it comes out as the most feasible technology.

The opposite can be said about the indirectly fired gas turbine: It has the lowest electrical efficiency and the lowest overall utilization, so it has to come up as the least favourable option.

Because the electricity sales price is higher than the heat sales price, the technologies with a high electrical efficiency are the most favourable, although a low overall utilization will counteract the benefits of a high electrical efficiency.

The annual production expense without capital costs and before heat sales can be compared to f. ex. the annual production expenses from danish district heating plants including capital costs.. If the district heating plants is based on a natural gas fired boiler the annual production expense is between 12 and 13 US$/GJ. If compared to production expenses from danish CHP-plants based on natural gas engines with an electrical efficiency of 38 % , the production expense is between 10 and 11 US$/GJ.

10.6 Sensitivity analysis

In order to evaluate the uncertainties in the economical calculations a sensitivity analysis has been performed on 4 parameters important for the economical calculations. Expenses for manning Electricity sales price Gas oil price Wood chips price

Each of these parameters have been increased with 10% and the effect on the annual production expense have been studied for each of the four technologies. The results of the sensitivity analysis is summarized in Figure 37 and graphically shown in Figure 38. If a parameter variation gives a negative impact on the production expense, i.e. the production expense is lowered, this variation is beneficial for the technology and vice versa.

Technology Wood chip price Gasoil price Electricity sales price Extra manning Steam turbine 9,20% 0,86% -3,24% 0,86% Steam Engine 9,33 % 0,95 % -3,67% 0,95 % Stirling engine 10,39% 0,98% -6,26% 0,98% Ind. fired GT 934% 0,76% -2,82% 0,76 % Figure 37. Results of sensitivity analysis. Figures show changes in annual production expense due to a 10% increase in cost for the relevant factor.

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 51 Sensitivity Analysis

0,76% 0,98% 0,95% I Ind. fired GT 0,86% I !a Stirling engine Steam Engine Steam turbine

0,76% 0,98% 0,95% 0,86% 1 10.3

920% 1

15,00% 1O,OO% -1O,OO% -15,00%

Figure 38. Results of sensitivity analysis.

10.7 Discussion

It can be seen that the wood chip price has the largest influence on the annual production expenses. This was to expect as the cost of wood chips is the biggest expense for the CHP-plant. Approximately 95 % of the fuel consumed by the CHP-plant is wood chips whereas only 5 % of the fuel is gas oil. The electricity sales price is also an important factor, because the only source of income is the electricity sale to the public grid.

It is maybe surprising that the cost for manpower has little or no effect on the annual production expense. The estimated manpower needed for operation of the CHP-plant can have been estimated too low, but even a doubling of the cost would not give a change of 2% on the production expenses.

10.8 Conclusion

This economical survey of four different small scale co-generetion technologies has given data on annual production expenses without capital costs. Based solely on the production expenses a ranking from 1-4 would be like this (1 being the best technology)

1. Stirling engine 2. Steam engine 3. Steam turbine 4. Indirectly fired gas turbine

Only one of the technologies surveyed is commercially available for this range of thermal output, and that is the steam turbine. It is a well proven technology, but for the plant size considered here it

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 52 has some severe limitations in efficiency (described elsewhere in this report) that does not make it an ideal choice.

The Stirling engine in contrary has a much larger potential when commercially available. It has a high electrical efficiency and a wide spectrum of power ranges can be covered due to the modular construction. Also very important is the fact that stabdard automotive parts and manufacturing methods can be used in the production thus giving the potential for a low production cost. The Stirling engine would have an even lower production expense if the electricity sales price was differentiated like f.es. in Denmark. Due to the heat storage of the CHP-plant the engine could run maximum load during the high- and mediumload periods of the day where the electricity price is the highest .

The Steam engine is demonstrated technology, but to achieve high electrical efficiencies, high steam pressure is necessary. Electrical efficiencies in the order of 25 % would require pressures above what can be achieved with standard industrial boilers. Custom made boilers would make it economically unattractive to build a CHP-plant based on a steam engine.

The indirectly fired gas turbine will not be an option fueled solely by wood chips until the problem of high temperature heat exchangers have been solved. Therefore this technology is not considered an economically viable option in the near future.

EATask X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 53 11. List of Literature

1. “Review of Small Steam turbines (0.25-10 MWJ ” , Peter J . Scott. Energy Efficiency Office of the Environment, 1991. Available from the Energy Efficiency Enquiries Bureau, Energy Technology Support Unit (ETSU), Hanvell Laboratory, Didcot, OX11 ORA, England.

2. “Product Guide - Small and Medium Turbines”, Modern Power Systems, January and February 1991 (2 issues). Order from Industrial & Electronics Publications, Wilmington house, Church Hill, Wilmington, Dartford, Kent DA2 7EF, England.

3. “AflaldifjtretKraftvrmevwk 620 kW ” (Waste Fueled CHP-plant 620 kW) 1992. Henning Andersen, Mogens Wee1 Hansen, dk-TEKNIK, Gladsaxe Marllevej 15, DK-2860 Sarborg, Denmark.

4. “Reviewof Steam and Stirling Engines for Energy from Waste Systems”, 1992. ETSU B 1347, Hanvell Oxfordshire OX1 1 ORA, England (prepared by Energy for Sustainable Development Ltd.) .

5. “Sdhalmfjtrede krafo/armevm-ker”(Small Straw-fueled CHP-Plants”, 1989. Dennnis Rasmussen, Jens Bjerrum, Technical College of Copenhagen, Denmark.

6. “Sdhalmkra@vamevcerker 100-1000 kW (Small Straw-fueled CHP-Plants IOO- lo00 kw). dk-TEKNZK, Gladsaxe Mnrllevej 15, 2860 Sarborg, Denmark.

7. Personal conversation with mr. Nils Peter Astrupgaard. Nils Peter Astrupgaard, dk-TEKNIK, Gladsaxe Marllevej 15, DK-2860 Sarborg , Denmark.

8. “Air- Independent Stirling Engine-powered Energy Supply System for Underwater Applications”, H. Nilsson, S. Gummesson, United Striling AB, Trans. I. Mar. E., VOI 100 pp 227-239.

9. “Stirling engines for biomass: state-of-the-art with focus on resultsfrom danish projects”, Biomass for Energy and the Environment (Proceedings of the 9th European Bioenergy Conference), Pergamon Press, 1996, vol. 1, pp 278-284.

10. “ Co-Generation with a Wood Chips Fueled Stirling Engine”, Christian Gaegauf, Hanspeter Zumsteg , Center for Appropriate Technology amd Social Ecology, CH-4438 Langenbruch, Switzerland

11. “Dezentrale Warme-Kraft-Kopplung mit Stirlingmotoren an Biomassefeuerungen”, 1993. Dr. Erich Podesser, Joanneum Research Forschungsgesellschaft m.b.H. , Elisabethstrasse 11, A-8010 Graz, Austria

12. LL Ceramic Air Heater for an Indirectly Fired Gas TurbineUsing Low Rank Fuels, N.J. Orozco and C.L. Vandervort, Hague International, 3 Adams Street, South Portland, ME 04106, USA

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 54 13. Personal conversation in Copenhagen with mr. Paul G. Lahaye, Chairman, Hague International, May 9th and MAy loth, 1994.

14. Data sheets from Hague International, 3 Adams Street, South Portland, ME 04106, USA.

15. “An Externally Fired Evaporative Gas Turbine for Small Scale Biomass Gasi~kation”.Report to CEC DG XVIII, Thennie contact BM/367/92/BE, J. de Ruyck, Vrije Universiteit Brussels, Dept. of Mech. Engineering, Brussels, Belgium

16. “ Wood-Waste Fueled, Indirectly-Fired Gas Turbine Cogeneration Plant for Sawmill Applications, Phase ZIZ:Preliminary Engineering and Financial Analysis of Alternative Con$igurations”, 1990. DSS contract no. 57SZ.23283-8-6058, Efficiency and Alternative Energy Technology Branch, CANMET. Energy, Mines and Ressources Canada, 580 Botth Street, 7th floor, Ottawa, Ontario, K1A OM, Canada.

17. Evaluation of a Woodchip Fired Co-Generation System Using a Gravel Bed Combustor”, 1991. Kenneth W. Ragland, Dannay H. Aetrs, Carl A. Palmer, Dpt. of Mech. Engineering, University of Wisconsin, Madison, WI 53706 USA

18. “Turbine Generator uses Clean Gasfrom Sawdust Combustion ”, 1993. Information brochure from CADDET, Swentiboldstraat 21, 6137 AE Sittard. P.O. Box 17, 6130 AA Sittard, The Netherlands.

19. “Facts on Installation, Operation and Economy for Wood Chip Fired District Heating Plants in Denmark”, 1993. dk-TEKNIK, Gladsaxe Mdlevej 15, DK-2860 S~borg, Denmark

IEA Task X - Texhnologies for Small Wood Co-Generation Systems. Economical calculations. Page 55 Enclosures. ANNEX 1: Steam engine organisations

This list of organisations is not exhaustive. The listing of an organisation does not constitute an endorsement by ETSU of its competence, and non-listing of an organisation does not discriminate against its competence.

Adelaide University Dr R. Sanderson Dept of Mechanical Engineering Tel: 010 61 8 228 5460 GPO Box 498 Fax: 010 61 8 224 0464 Adelaide, SA 5001 AUSTRALIA

Anutech Pty Ltd Professor Kaneff GPO Box 4 Tel: 010 61 6 249 2476 Canberra ACT 2601 Fax: 010 61 6 249 1884 AUSTRALIA

BEST Pty Ltd Dr Stephen Joseph 5 Kenneth Avenue Tel: 010 61 43 695108 Saratoga NSW 2251 Fax: 010 61 43 843996 AUSTRALIA

DanSteam Unknown Milton Andersen AIS Kornmarksvej 8-10 2605 Brandby DENMARK

ESD Engines Ltd Drummond Hislop 51 Artesian Road TeI: 071 792 2241 London W2 5DB Fax: 071 792 2543 UNITED KINGDOM

Fezer SA Fernando Fezer Steam Engines Division Tel: 010 55 496 62 2222 Industrias Mecanicas Fax: 010 55 496 62 1386 Cacador City Santa Catalina BRAZIL

Mernak SA Waldomilo Bilhar Steam Engines Division Tel: 010 55 51 722 2144 Industria Brasiliera de Maquinas Fax: 010 55 51 722 2971 Cachoeira do Sul City Riogrande do Sul BRAZIL Alex Ritchie Tel: 0255 880426 Ley House Rectory Road Rabness, Harwich UNITED KINGDOM Fred Prahl Skinner Engine Company Power Division Tel: 010 1 814 454 7103 PO Box 1149 Erie, PA 16512 USA

Spillingwerk GmbH Gerhard Gneuss Werfstrasse 5 Tel: 010 49 40 789 1750 2000-Hamburg 11 Fax: 010 49 40 789 2836 GERMANY

SwedSteam AB kif Palm Box 4072 TeUFax: +46 - 8 756 7081 S-1 83-04 Taby Sweden

Tharnes Steam Launch Ltd 12A Spring Grove London W4 UNITED KINGDOM ANNEX 2: Stirling engine organisations

This list of organisations is not exhaustive. Listing of an organisation does not constitute an endorsement by ETSU of its competence, and non-listing of an organisation does not discriminate against its competence.

Akin-Seiki Co. Ltd Dr T. Watanabe 2nd R&D Centre Minami-nakane Nishio Aichi 446 JAPAN

British Cod Corporation M. E. Crowther Coal Research Establishment Tel: 0242 673361 Stoke Orchard, Cheltenham Fax: 0242 676506 Gloucestershire GL52 4RZ UNITED KINGDOM

CMC (see TEM)

ESD Engines Ltd Drummond HisIop 51 Artesian Road Tel: 071 792 2241 London W2 5DB Fax: 071 792 2543 UNITED KINGDOM

Kockums AB Christer Bratt Stirling Engine Division Tel: 010 46 40 348000 20555 Malmo Fax: 010 46 40 973281 SWEDEN

Matsushita Electrical Ind. Co. Ltd Dr Kenichi Inoda Central Research Laboratory 3-15 Yagurno Nakamachi Moriguchi Osaka JAPAN

Mechanical Technology, Inc. Mr Steven P. Upham III S tirling Engine Division Tel: 010 1 518 785 2211 968 Albany Shaker Road Fax: 010 1 518 785 2297 Latham NY 12110 USA Mitsubishi Electric Corp. Dr Takuya Suganami Central Research Laboratory Stirling Engine Division 1-1 Tsukaguchi honmachi 8-chome Arnagasaki 661 JAPAN

Mitsubishi Electric Corp. Dr Mikio Mori Nagasaki Works Stirling Engine Division 6-14 MXUO Nagasaki 850-91 JAPAN

Sanden Corporation Dr H. Kojirna Stirling Engines Division Isesalu Gunma 372 JAPAN

Sanyo Electric Company Ltd Dr Junji Matsue Air Conditioning Business Headquarters R & D Centre 180 Sakata, Oizurni-Machi Ora-Gun, Gunma JAPAN

Schlaich Bergermann und Partner Wolfgang Schiel HohernzollernstraBe 1 Tel: 010 49 711 648710 D-7000 Stuttgart 1 Fax: 010 49 711 648 7166 GERMANY

Ship Research Institute Dr Shigeji Tsukahara Shinkawa Mitaka Tokyo 181 JAPAN

Stirling Motors Europe BV Robert Verhey Postbus 16350 Tel: 010 31 70 381 9394 2500 BJ Den Haag Fax: 010 31 70 382 4321 NETHERLANDS

Sistemi e Prodotti Stirling ltalia Roberto Mari via De Cnstofons, 13 Tel: 010 39 2 738 5519 20124 Milano Fax: 010 39 2 701 23111 ITALY Stirling Technology Cop. Brad Ross Sales Division Tel: 010 1 509 375 4000 2952 George Washington Way Richland WA 99352 USA Kinzelman Stirling Technology Inc. Craig PO Box 2633 Tel: OiO 1 614 594 2277 Athens Ohio 45701 USA

Stirling Thermal Motors Inc. Lennart N. 3ohansson 2841 Boardwalk Tel: 010 1313 995 1755 Ann Arbor Michigan 48104 USA

Sunpower Inc. John G. Crawford 6 Bywd Street . Tel: 010 1 614 594 2221 Athens Fax: 010 1 614 593 7531 Ohio 45701 USA

TEM - Malmo Research Centre blr kif Erlanesson Nya Agnesfridsvagen 220 Tel: 010 46 40 313401 S-21579 Malmo Fax: 010 46 40 948960 SWEDEN

Toshiba Corp. & Consumer Products Sales Division - Stirling Engines 8 Shinsugita-cho Isogo-ku Yokohama 235 JAPAN