Proceedings of FUELCELL2006 The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY

June 19-21, 2006, Irvine, CA

FUELCELL2006-97183

A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES.

Victor Schols1 Theo Klaver2 Mark Pettitt2 Chris Ubuan2

Sape Miedema1 Kas Hemmes3 W.J. Vlasblom1

1) Delft University of Technology, Faculty of Mechanical Engineering, Delft. The Netherlands

2) Shell Global Solutions, Rijswijk , The Netherlands

3) Delft University of Technology, Faculty of technology Policy and Management, Delft. The Netherlands

ABSTRACT This paper presents the results of a study to evaluate

the feasibility of deploying fuel cells in hydrocarbon producing facilities. For the majority of hydrocarbon production facilities, electric power is generated on-site, most often, by the combustion of some of the produced hydrocarbons. To optimize its performance, Shell is continuously looking at applying new technologies, which can increase the availability of her production facilities and/or reduced lifecycle costs and/or improve safety and environmental performance. Shell has identified fuel cell technology as being capable of delivering some of these benefits because of its potential to achieve high availability, reliability and fuel efficiency when compared to conventional technologies. An inventory has been made of the specific design specifications and the state-of-the-art of commercially available fuel cell systems. Most of the required capacities fall in the range of 1kW to 1 MW, which is compatible with state of the art fuel cell developments or it can be achieved in the near future. A software-screening tool has been constructed to evaluate the various options with respect to conventional technologies. The specific design specifications can vary from production site to site, but in general availability and low maintenance are two of the main criteria to be considered and most favorable for fuel cells. Depending on the specific requirements for a particular hydrocarbon production facility a polymer fuel cell, MCFC or SOFC system are considered suitable alternatives to conventional technology. The screening tool has been applied and evaluated in a case study

of one of the unmanned production facilities of Shell. A 20 kW SOFC system was found to score higher than a commercially available gas engine of 25 kW on eight of the most important of several criteria. However, SOFC system lifecycle costs are still 15 to 20% higher due to the development costs needed for this ‘prototype’ SOFC system to make it suitable for use in hydrocarbon producing facility. When applied in more surface production facilities the SOFC system also becomes costs competitive with conventional technologies.

1. INTRODUCTION

The oil and gas demands of modern society are increasing globally. To meet this increasing demand, more and more reservoirs have to be economically produced in increasingly challenging environments. Shell has production facilities all over the world producing oil and gas to meet this demand. The location of these facilities are determined by the accumulations of hydrocarbons that are discovered and are therefore found in all variety of environments including, desert, swamp, jungle, tundra, offshore and subsea. In the processing and transportation of oil and gas, these facilities need electrical power to supply large pumps, compressors, valves, control systems, auxiliary equipment and facilities for the crew. Owing to the isolated locations of the facilities, electrical power or an electrical power grid is often not available and instead it is generated locally at the facilities themselves, often by combustion of the hydrocarbons that are

1 Copyright © 1996 by ASME

Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

produced. Shell is continually looking to optimize its performance through the application of new technologies, which can increase oil and gas production availability and/or reduce lifecycle costs and/or improve safety and environmental performance. In this regard, Shell is investigating novel fuel cell technologies and their potential for application in oil and gas production. This led to the following problem definition: Can fuel cells be economically applied in the production of hydrocarbons to increase performance, production availability, reduce lifecycle costs and improve safety, integrity and reduce the impact on environment? If so what type of fuel cell can be used and what applications are most suited for fuel cells? If not, what are the technical challenges that have to be faced for a competitive positioning of fuel cells versus conventional techniques.

NOMENCLATURE CAPEX: Capital Expenses OPEX: Operational Expenses POS: Possibility of Succes. W, kW, MW: Watts, Kilowatt, Megawatt

2. INVENTORY OF POSSIBLE APPLICATIONS FOR FUEL CELLS IN SURFACE FACILITIES.

In order to be able to determine where fuel cells could be

applicable within the surface facilities of hydrocarbon production, one needs to know what power sources are currently used and where.

In order to establish as many applications as possible for fuel cells in the widest sense a brainstorm session was held with engineers with various background, discipline and experiences. This brainstorm session not only produced a wide scope of applications but also identified the criteria that the power supplies have to fulfill. During the brainstorm session the participants were to think “out of the box” for all applications, -relevant to Shell or not- and all possible criteria that could affect the fuel cell in any way.

The following application groups were identified: Main production facilities: the main production facilities

of an oil field have their own power supply and usually produce between 10 and 20 MW. The power is commonly generated by large gas turbines that run on natural gas, which is usually present in an oil field.

Unmanned production facilities: not all fields have just one large reservoir on one location. It can occur that smaller reservoirs are located some kilometres from the main reservoir. These smaller reservoirs, called satellite fields, can be exploited with satellite production facilities. These satellite production facilities may or may not include pumps and compressors for field pressure boosting and other high power demanding equipment. Thus power supplies between a few kW and several hundred kW are required. This electric power

is presently provided on site by gas or diesel engine driven generators or provided from the main facilities through cables.

Remote wellheads: smaller satellite wellhead facilities that require low power for monitoring and control can be provided with power by pulling a cable from the main facilities as well. For these remote wellheads some hundreds of W is needed. More powerful operations such as valve control are often done with pneumatic instrumentation. Communication equipment requires a few W only and can be powered with solar panels. We categorize this as wellhead power supply.

Subsea: subsea facilities are powered by umbilicals currently. Umbilicals are large cables that contain power cables as well as data cables and sometimes small tubings for chemicals. These subsea wellheads can consume between 100 kW and several MW. As yet no feasible way has been found to produce power on site at the sea bottom.

Back up power: If the main power production fails, back up power will be provided for a proper shut down. For back up power a large battery stack is very common, but diesel engines are often used as well. These back up systems have to have a near 100% reliability for the short period of time that they are called into service.

Local instrumentation: there are production facilities that use obsolete (pneumatic equipment for monitoring and measuring values of importance for production control. Small sensors and transmitting equipment can offer a solution for this problem. To power these sensors batteries are required that can produce a very small current for several years. This power is provided by rechargeable batteries , such as Li-ion either with or without solar energy for recharging.

To deploy fuel cell technology in any of these application

groups, several criteria have to be taken into account and these include power output level, availability, emissions, efficiency, maintenance, size, weight, etc. Power supply availability and reliability is however very critical, since whenever power supplies fail, the production is shut down which implies high costs to Shell. Fuel cells could offer a more reliable solution for this problem, because fuel cells have a high availability in spite of being a relatively new technology and they require little or no maintenance.

3. MULTICRITERIA ANALYSIS

With various applications where fuel cells can be deployed for power generation, it is important to identify applications where the most benefit will be derived. Therefore the identified applications were ranked as shown in the ranking grid - Appendix 1, and a multicriteria analysis has been set up and performed. The ranking grid used for this purpose is a plot of importance of the application versus its quantity.

The level of importance is based prospectively on the relevance to: 1) Shell exploration and production, 2) Shell as a

2 Copyright © 1996 by ASME

Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

whole (i.e., including non oil producing busineses) and 3) all other applications; indicated on the grid by the colours blue, red and green respectively. The relevance to these three categories of applications is defined by the group of engineers that participated in the brainstorm session and is based on their experience. On the X-axis the quantity of the application is expounded. When an application is ranked on the right side of the grid, it will be applicable on many locations or purposes. It does not say anything about the financial quantity of the application, which means that the quantity on the X-axis is independent of Capital Expenses (CAPEX) that could be involved in the fuel cell application.

Here only the applications in Quadrant I represent those applications with high volume and high importance to Shell. As one can see in the grid, this means that four applications are taken into account for further research;

1. Flare gas 2. Unmanned facilities 3. Fixed batteries 4. Wellhead power supply

For the flare gas application, Shell wishes to use the gas that is currently being flared by some facilities to produce electricity in order to eliminate the gas flaring problem. During the brainstorm all possible criteria that were of any importance to fuel cells in the different applications, were listed and weighted for each application. By multiplying the weight of each criterion by the POS, it became possible to determine the application that is best for fuel cells. A low POS would indicate a low chance that the fuel cell is able to meet the criterion’s requirement.

The multi-criteria analysis showed two main, potentially viable applications i.e.: unmanned facilities and wellhead power supply. Although not in Quadrant I, subsea power supply was identified as an application that could lead to significant benefit for Shell, but was however considered to presently too technically challenging to be considered at this early stage. Using flare gas to fuel a fuel cell was considered a non-feasible option as well, because of the non-continuous inflow of fuel gas. An overcapacity of fuel cell stacks would be required in order to be able to always handle the amounts of flare gas emitted. Replacing fixed batteries with small fuel cells was also found not to be of a large interest for surface production facilities, because fuel cells do not start up quickly in general, a requirement which is needed for back-up power systems. Moreover, in general, compressed gas is needed to fuel the fuel cell back-up system, which has a negative effect on the safety of the total facility.

A further study in both main applications; unmanned facilities and wellhead power supply, was therefore performed. This study included the development of a tool that surveys the life cycle costs of the project including the fuel cell system and its impact on the environment.

4. POTENTIALLY SUITABLE FUEL CELL SYSTEMS FOR SURFACE PRODUCTION FACILITIES.

A preliminary screening of the State of the art of fuel cell systems identified the Solid Oxide Fuel Cells (SOFC), Polymer Exchange Membrane Fuel Cells (PEMFCs), Direct Methanol Fuel Cells (DMFCs) and Molten Carbonate Fuel Cells (MCFCs) as the types most likely to meet the specifications needed for production facilities. The most interesting commercially available system for each fuel cell type are listed next (for more details on the type of fuel cells see (1)).

4-1 Solid Oxide Fuel Cell

A company in the UK is developing low temperature SOFC systems suitable for application in hydrocarbon production facilities. The SOFC system is based on units of 25 kW. It is a low temperature SOFC design operating between 500-600 0C, therefore an all-metal support can be used, reducing its weight. This lower operational temperature overcomes a number of the issues associated with the higher temperature SOFC designs. The fuel cell is shown to be robust to thermal and redox cycling and capable of delivering technologically relevant power densities. Another importance advantages of the system is that it can operate effectively down to 20% of its full capacity and has a near 100% predicted availability (outside the planned maintenance). System weight and price approach the target specifications.

4-2 Proton Exchange Membrane Fuel Cell

The Dutch company Nedstack in Arnhem has developed a 20 kW fuel cell stack module named the “A-200”. There can be as much as 40 PEMFCs placed in series without any complications, yielding an electricity production power of 800 kW. The 20 kW stack has a weight of 56 kg and has operated reliably for over 40,000 hours.

4-3 Direct Methanol Fuel Cell

A German company named Udomi has specialized itself in complete Direct Methanol Fuel Cell systems and the most interesting system that is commercially available is the “Smart Fuel Cell A50-M”, which is a portable Direct Methanol Fuel Cell system that produces 50 W and has a separate small methanol tank. The weight of this complete system is 6 kg without fuel cartridge. With its 5 Litre cartridge the fuel cell can operate over 70 hours at full power output.

4-4 Molten Carbonate Fuel Cell

The German company, MTU, together with their American partner, Fuel Cell Energy (FCE), has come up with a promising fuel cell system that is commercially available. The system is called the HotModule and can provide 245 kW. It has its name because all the hot parts of this fuel cell system are accommodated in a single housing, which according to the manufacturer “not only makes parts of the periphery superfluous, but also enables new standards in efficiency to be

3 Copyright © 1996 by ASME

Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

set.” The system is claimed to have an electrical efficiency of approximately 50%. An overview of potentially suitable fuel cell systems is provided in Table 1.

Fuel cell type Fuel cell system Power (kW) SOFC 5-200 PEMFC A-200 20-800 DMFC Smart fuel cell A50-M 0.050 MCFC Hot module 245

Table 1 Overview of potentially suitable fuel cell systems

5. CASE STUDY OF ONE OF SHELL'S UNMANNED SURFACE PRODUCTION FACILITIES.

A case study was performed for a particular Shell’s surface production facility to study in more detail the feasibility of applying fuel cells, what type of fuel cell system would be most suitable in this particular case and what technical and economic challenges are still to be faced. 5-1 Background of the case study The production facility is part of a shallow, offshore field, which consists of several platforms of different sizes and capacities. Most of the platforms are satellite platforms and mostly unmanned.

The current power supply, a Copper Turbine Generator (CTG), on this platform delivers 7.2 kW but is obsolete and requires replacement within 2 or 3 years. This power is used for cathodic protection of the steel construction, a Remote Telecom Unit (RTU) and lighting. If the power shuts down, the production of this platform will not be directly affected. Therefore this case has been identified as an opportunity for a fuel cell system trial. The platform is unmanned, but is visited weekly for inspection. The platform has space in a safe area to install a non-certified fuel cell system. This case study was required to identify where the fuel cell should be installed, what fuel gas treatment is necessary and what performance characteristic is expected from the fuel cell system. Other benefits, in addition to cost and reliability, were also investigated. Comparison between 20 kW SOFC system and Gas Engine

Table 2: Criteria for power sources in unmanned facilities.

For the general comparison between the gas engine and the fuel cell system, we used a general multi-criteria analysis procedure developed in this work to evaluate the various possibilities for the application of fuel cells. Table 2 shows the seven most important criteria used in this procedure including their weighing factors.

F u e l c e ll s y s te m (2 0 k W )lo w e r u p p e r

P ro je c t m a n a g e m e n t (8 % ) 1 8 1 2 0D e s ig n , E n g in e e r in g , F a b r ic a tio n & M a te r ia ls 1 5 0 1 0 0 0In s ta lla t io n (3 0 % ) 4 5 3 0 0In s p e c t io n & o th e rs (5 % ) 1 0 6 5T o t C A P E X 2 0 5 1 3 6 5C o n tin g e n c y (1 5 % ) 3 1 2 0 5T o t C A P E X ($ K , in c lu d in g c o n tin g e n c y ) 2 3 5 1 5 7 0

Table 3: General comparison of a gas engine with a fuel cell

system. Fairley

25 kW gas engine for Fairley 25 kW FC-system for Fairley Fairley field requirement

Availability +/- ++ High, cathodic protectionTolerance to impurities + ++ Medium, clean gas (no H2S and very little Hg)Appl in Hazardous area - + Low, safe area and zone 2 availableEuro/kW -- -- Medium, trialSafety + + High, weekly visitedPower/Weight + + Low, up to 2 ton availableAvailabilty of fuel ++ ++ High, always G/L gas present from FBPP-01Turn down ratio - ++ high, operation between 7.2 kW and 25 kW

Table 4: Comparison of gas engine and fuel cell system for the

case study. Error! Reference source not found.

These are listed again in table 3 and given “++” or “+” in case the condition is excellent or good respectively and “-“ when the criterion is not fulfilled. This table indicates that normally the fuel cell system is not doing well in the weight/power ratio and euro/power ratio, where the gas engine is scoring better.

For the case study application the situation looks different. The scorings are based on preliminary estimates of the SOFC’s manufacturer. The scorings of the gas engine are based on a previous investigation carried out on the production facility using a commercially available 25 kW gas engine-driven generator. The third column of Table 4 shows the requirements of the case study field for each criterion. Table 4 an extra criterion is added; the “turn down ratio”, which reflects the requirements that the power source must be able to operate at part load. Since the normal power output will be around 7.2 kW and occasional peaks occur up to 20 kW, the power system has to be capable of operating at this lower capacity whilst still able to provide the required peak power. Also future power demand is expected to grow to 20KW on a continous basis. Gas engines tend to rapidly loose efficiency once operating under 60% of their nominal power, but in general this is not the case for fuel cells. The low temp SOFC fuel cell system can operate with almost the same efficiency down to 20% of its nominal capacity. Below 20%, the fuel cell’s auxillary power consumption becomes relatively high and the system’s efficiency drops quickly.

Unmanned facilitiesWeightings Demand of condition POS Score WeightingAvailability High 10 34 8.29%Tolerance to impurities High 6 29 7.07%Appl in Hazardous area High 5 28 6.83%Euro/kW Medium 8 27 6.59%Safety High 6 26 6.34%Power/Weight High 6 25 6.10%Availabilty of fuel High 6 23 5.61%

Other remarkable scorings are that the fuel cell system can handle a variety of input gasses. A fuel cell requires clean

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Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

gas, but this system contains a reformer that can reform methane, to hydrogen, in the presence of contaminants such as heavy hydrocarbons and water. The gas from this particular production site does not contain H2S.

The availability is scored high as well, which is based on the fact that the low temp SOFC manufacturer expects an availability of over 99.5%. An additional advantage of the fuel cell system is that it produces DC-current. In this application a DC-current is useful, because a large part of the power requirement is for cathodic protection of the structural steel against corrosion. Another well-known advantage of the fuel cell system is that its emissions are lower than for the gas engine. The fuel cell system produces no SOx or NOx emissions and less CO2. 5-2 Lifecycle cost comparison between gas engine and low temp SOFC fuel cell system. Life cycle costs comparison is often used to screen or evaluate projects and take cognisance of CAPital EEpenses (CAPEX) and also OPerational EXpenses (OPEX) such as overhauls, maintenance, spares, etc.

The lifecycle costs are calculated with the fuel cell screening tool, developed in this work, using the data from the low temp SOFC manufacturer and the owner of the asset used for this case study. The asset owner’s data are shown in Table 5 below:

Table 5: CAPEX of a 25 kW gas engine for FAPP-02 The low temp SOFC manufacturer has made estimations

for the costs of their 20 kW fuel cell system primarily based on the information about the power requirement and gas composition of the case study asset.

A rough estimation for a lower and an upper boundary of the CAPEX of the fuel cell system as shown in

Table 6 are provided by the SOFC manufacturer using a 20 kW power requirement for continuous power and short power output peaks with short response times and the asset’s fuel gas composition. The SOFC manufacturer estimates the purchase costs for the low temp SOFC system at between 7.500, -$/kW for the purchase of several units and 50.000$/kW -for a one-off prototype fuel-cell of 20 kW. This estimate includes development costs. This relatively large difference is primarily caused by high development costs to modify the

manufacturer’s existing products for usage in a hydrocarbon production facility. The range cannot be narrowed down at the moment, because the fuel cell manufacturer does not completely know what to expect during development, but the upper boundary is more likely to happen in case Shell buys 1 or 2 units and the lower boundary for significantly more units.

Fuel cell system (20 kW )low er upper

Project management (8%) 18 120Design, Engineering, Fabrication & Materials 150 1000Installation (30%) 45 300Inspection & others (5%) 10 65Tot CAPEX 205 1365Contingency (15%) 31 205Tot CAPEX ($ K, including contingency) 235 1570

Table 6: CAPEX estimations for the 20 kW low temp SOFC

fuel cell system 5-3 Lifetime of power source: The asset owner report indicated a gas engine lifetime of 15 years. The fuel cell manufacturer has targeted the fuel cell system at 80.000 hrs (~ nine years) before a major re-fit is required. The manufacturer estimates the cost of a major re-fit as one-third of the initial CAPEX. After 15 years 1 * CAPEX gas engine should be paid again to replace the gas engine. ith a project life of 30 years, the lifecycle costs would be as indicated in Table 7, below:

Gas engine (25 kW )1 x 100% 2 x 100%

Project management 24 31Design & Engineering 46 58Materia l 167 194Fabrication and insta lla tion & HUC 139 194Inspection & others (5%) 16 19Tot CAPEX 392 496Contingency (15%) 58 77Tot CAPEX ($ K, including 15% contingency) 450 573

Options Fuel Cell system Gas engine

lower boundary Upper boundaryAvailability >99.5% >99.5% 86% 98%N x 100% 1 x 100% 1 x 100% 1 x 100% 2 x 100%CAPEX ($ K) 235 1570 450 573OPEX ($ K, annum) 3.5 3.5 39 78

Lifecycle costs ($ K) over 30 years (7%) 305 1835 955 1510

If ordered in small numbers upper Low turn down ratio,Limitation boundary costs is more likely maintenance intensive

to happen and long developmenttime required

Table 7 Lifecycle costs of a 25 kW gas engine and 20 kW SOFC compared.

The breakdown of gas engine CAPEX shows that raw materials are a small percentage of the total CAPEX of the gas engines. Therefore the cost difference between 25 kW gas engines and 20 kW is negligible and certainly not as large as it would be for the fuel cell system. It is therefore justified to compare a 25 kW gas engine with a 20 kW fuel cell system. 5-4 Sensitivity analysis. The case study involved an effort to determine if an SOFC system would fit in an unmanned platform and what the

5 Copyright © 1996 by ASME

Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

technical challenges would be. By adjusting several parameters it became clear what criteria have an impact on the fuel cell system’s performance and design and what parameters have a insignificant impact on the performance, with respect to the relevant criteria The price, size and weight of a 20 kW SOFC-stack is fixed by the manufacturer. To optimise the system for its application other parameters can be adjusted. This sensitivity analysis led to the following conclusions for the low temp SOFC system used for this case study: Fuel cell stack: The fuel cell stack of the SOFC-system has a significant influence on the price, size and weight of the material of the fuel cell system. The fuel cell stack determines almost 50% of the material price, size and weight. If one needs twice as much maximum power output capacity, that would mean twice as much fuel cell stacks and almost 150% of the material price, seize and weight of the system. Load requirements: Load cycle data are of substantial importance to the system’s design. With load cycle data, the manufacturer can determine whether the fuel cell system is required to have a 20 kW fuel cell stack capacity or not and how large the battery pack is required to be. Both battery pack and fuel cell stack have a large impact on size, weight and material costs. As mentioned before, the fuel cell stack can add almost 50% to the material weight, size and costs. The battery pack can include up to 20 % of the material weight, size and costs. Gas quality: The platform used for this case study has two gas streams. Both gas streams have different pressures, temperatures and different compositions. It turned out that processing the gas to fuel gas for the SOFC-stack does not require especially different processing facilities for both cases. To bring the gas to the required pressure and temperature will not alter the system design drastically. The composition also does not have a large effect on the system. Heavier hydrocarbons in the gas apart from CH4, and components such as CO2, H2O, O2 and N2 can easily be adjusted to the right concentrations for the system. Thus the gas composition, temperature and pressure do not have a significant impact on the fuel cell systems price, weight, size, design or performance. It can be concluded that the largest cost factor for the fuel cell system is the development and upscaling costs of the prototype. The fuel cell stack and battery pack largely determine weight and size of the power system.

5-5 Case study: conclusions and recommendation The lifecycle costs of the 20 kW fuel cell system are estimated to be only 15-20% higher than the lifecycle costs of a 25 kW gas engine for for this case study if only one prototype fuel cell system, including the high development costs is bought by Shell. A purchase order for several fuel-cell systems would immediately reduce the cost per system significantly. In general, the estimates on the eight most important criteria of the fuel cell system score higher than the gas engine. These criteria are: power/Euro ratio, availability, tolerance to impurities, applicability in hazardous areas, turn down ratio, safety, power/weight ratio and availability of fuel. In order to make the material cost estimate more accurate, load cycle data are required to make better estimates for the size of the fuel cell stack and battery stack. The technical challenge for this fuel cell system is to develop a system suitable for use in a hydrocarbon processing facility from existing technology. The fuel cell stack has been manufactured and tested already on a 5 kW scale, as well as an autothermal reformer with pre-reforming, but the development of a system suitable for this application with a capacity of 20 kW and other case specific requirements is a technical challenge. The lifecycle costs are rough estimates. We propose that these estimates should be further refined. The upper and lower estimate boundaries for the CAPEX of the fuel cell system should be narrowed down. If the more accurate estimates show that the fuel cell system’s lifecycle costs will not be considerably higher than the gas engine’s lifecycle costs, Shell should proceed with this trial.

A closer look at the safety zone requirement issues should be taken in as well. An ATEX-certification means that the certified apparatus can officially be operative in a zone 2 hazardous area. A system that is certified as zone 2 safe cannot ignite any gas mix that might be in the area, so for example all electrical parts have to be sealed extremely well, and the temperature of any exhaust gas stream may not be above a certain temperature level and the fuel gas stream will have a different classification than a methane gas stream, because it contains heavier hydrocarbons (C2-C7) as well.

The fact that the fuel cell system does have lower CO2-emissions and no NOx or SOx-emmisions and provides a DC-current which is ideal for cathodic protection applications was not yet expressed in terms of economical benefits but should be taken into account in a further detailed feasibility study.

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Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

6. CONCLUSIONS REFERENCES Our estimates show that fuel cell systems can become more economically than conventional power supplies if fuel cell systems are produced in larger quantities. In particular, the high availability pays of rapidly in unmanned facilities due to a strong reduction in operational costs. The DC power provided by fuel cells can be an additional advantage when the oil and gas production facilities use cathodic protection for corrosion prevention.

[1] Hirschenhofer, J. H.; Stauffer, D. B.; Engleman, R. R. Fuel Cells, A Handbook (5th edition); P2-1 ed.; US Department of Energy: 2000. ~~

ANNEX A: RANKING GRID FOR IDENTIFIED FUEL CELL APPLICATIONS.

Figure 1 Ranking grid for identified fuel cell applications, qualitatively indicating the importance of the application for Shell

respectively others and an indication of its potential quantity worldwide.

Importance

High Large power

Flare gascars

Spacecraft(underground) trains

Subsea unmanned facilities

Household applications (Central Heating)artic power fixed batteries

HospitalDownhole

wellhead power

Back-up power data

Portable

medial

Low Cars trains

Low High Quantity

Shell exploration and production

Other

I II

IV III

Shell as a whole incl non-oil and gas

7 Copyright © 1996 by ASME

Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

Copyright: Dr.ir. S.A. Miedema

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5. Miedema, S.A. "The mathematical modeling of the soil reaction forces on a cutterhead and the development of the computer program DREDMO" (PDF in Dutch 25 MB). CO/82/125, Delft University of Technology, 1982, with appendices 600 pages.

6. Miedema, S.A.,"The Interaction between Cutterhead and Soil at Sea" (In Dutch). Proc. Dredging Day November 19th, Delft University of Technology 1982.

7. Miedema, S.A., "A comparison of an underwater centrifugal pump and an ejector pump" (PDF in Dutch 3.2 MB). Delft University of Technology, 1982, 18 pages.

8. Miedema, S.A., "Computer simulation of Dredging Vessels" (In Dutch). De Ingenieur, Dec. 1983. (Kivi/Misset).

9. Koning, J. de, Miedema, S.A., & Zwartbol, A., "Soil/Cutterhead Interaction under Wave Conditions (Adobe Acrobat PDF-File 1 MB)". Proc. WODCON X, Singapore 1983.

10. Miedema, S.A. "Basic design of a swell compensated cutter suction dredge with axial and radial compensation on the cutterhead" (PDF in Dutch 20 MB). CO/82/134, Delft University of Technology, 1983, 64 pages.

11. Miedema, S.A., "Design of a seagoing cutter suction dredge with a swell compensated ladder" (PDF in Dutch 27 MB). IO/83/107, Delft University of Technology, 1983, 51 pages.

12. Miedema, S.A., "Mathematical Modeling of a Seagoing Cutter Suction Dredge" (In Dutch). Published: The Hague, 18-9-1984, KIVI Lectures, Section Under Water Technology.

13. Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.

14. Miedema, S.A., "Longitudinal and Transverse Swell Compensation of a Cutter Suction Dredge" (In Dutch). Proc. Dredging Day November 9th 1984, Delft University of Technology 1984.

15. Miedema, S.A., "Compensation of Velocity Variations". Patent application no. 8403418, Hydromeer B.V. Oosterhout, 1984.

16. Miedema, S.A., "Mathematical Modeling of the Cutting of Densely Compacted Sand Under Water". Dredging & Port Construction, July 1985, pp. 22-26.

17. Miedema, S.A., "Derivation of the Differential Equation for Sand Pore Pressures". Dredging & Port Construction, September 1985, pp. 35.

18. Miedema, S.A., "The Application of a Cutting Theory on a Dredging Wheel (Adobe Acrobat 4.0 PDF-File 745 kB)". Proc. WODCON XI, Brighton 1986.

19. Miedema, S.A., "Underwater Soil Cutting: a Study in Continuity". Dredging & Port Construction, June 1986, pp. 47-53.

20. Miedema, S.A., "The cutting of water saturated sand, laboratory research" (In Dutch). Delft University of Technology, 1986, 17 pages.

21. Miedema, S.A., "The forces on a trenching wheel, a feasibility study" (In Dutch). Delft, 1986, 57 pages + software.

22. Miedema, S.A., "The translation and restructuring of the computer program DREDMO from ALGOL to FORTRAN" (In Dutch). Delft Hydraulics, 1986, 150 pages + software.

23. Miedema, S.A., "Calculation of the Cutting Forces when Cutting Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 16 MB)". Basic Theory and Applications for 3-D Blade Movements and Periodically Varying Velocities for, in Dredging Commonly used Excavating Means. Ph.D. Thesis, Delft University of Technology, September 15th 1987.

24. Bakker, A. & Miedema, S.A., "The Specific Energy of the Dredging Process of a Grab Dredge". Delft University of Technology, 1988, 30 pages.

25. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Proc. WODCON XII, Orlando, Florida, USA, April 1989. This paper was given the IADC Award for the best technical paper on the subject of dredging in 1989.

26. Miedema, S.A., "The development of equipment for the determination of the wear on pick-points" (In Dutch). Delft University of Technology, 1990, 30 pages (90.3.GV.2749, BAGT 462).

27. Miedema, S.A., "Excavating Bulk Materials" (In Dutch). Syllabus PATO course, 1989 & 1991, PATO The Hague, The Netherlands.

28. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Terra et Aqua No. 41, December 1989, Elseviers Scientific Publishers.

29. Miedema, S.A., "New Developments of Cutting Theories with respect to Dredging, the Cutting of Clay (Adobe Acrobat 4.0 PDF-File 640 kB)". Proc. WODCON XIII, Bombay, India, 1992.

30. Davids, S.W. & Koning, J. de & Miedema, S.A. & Rosenbrand, W.F., "Encapsulation: A New Method for the Disposal of Contaminated Sediment, a Feasibility Study (Adobe Acrobat 4.0 PDF-File 3MB)". Proc. WODCON XIII, Bombay, India, 1992.

31. Miedema, S.A. & Journee, J.M.J. & Schuurmans, S., "On the Motions of a Seagoing Cutter Dredge, a Study in Continuity (Adobe Acrobat 4.0 PDF-File 396 kB)". Proc. WODCON XIII, Bombay, India, 1992.

32. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "On the Closing Process of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 1 MB)". Proc. WODCON XIII, Bombay, India, 1992. This paper was given the IADC Award for the best technical paper on the subject of dredging in 1992.

33. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "The Closing Process of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 1 MB)". Terra et Aqua No. 49, September 1992, IADC, The Hague.

34. Miedema, S.A., "Modeling and Simulation of Dredging Processes and Systems". Symposium "Zicht op Baggerprocessen", Delft University of Technology, Delft, The Netherlands, 29 October 1992.

35. Miedema, S.A., "Dredmo User Interface, Operators Manual". Report: 92.3.GV.2995. Delft University of Technology, 1992, 77 pages.

36. Miedema, S.A., "Inleiding Mechatronica, college WBM202" Delft University of Technology, 1992.

37. Miedema, S.A. & Becker, S., "The Use of Modeling and Simulation in the Dredging Industry, in Particular the Closing Process of Clamshell Dredges", CEDA Dredging Days 1993, Amsterdam, Holland, 1993.

38. Miedema, S.A., "On the Snow-Plough Effect when Cutting Water Saturated Sand with Inclined Straight Blades (Adobe Acrobat 4.0 PDF-File 503 kB)". ASCE Proc. Dredging 94, Orlando, Florida, USA, November 1994. Additional Measurement Graphs. (Adobe Acrobat 4.0 PDF-File 209 kB).

39. Riet, E. van, Matousek, V. & Miedema, S.A., "A Reconstruction of and Sensitivity Analysis on the Wilson Model for Hydraulic Particle Transport (Adobe Acrobat 4.0 PDF-File 50 kB)". Proc. 8th Int. Conf. on Transport and Sedimentation of Solid Particles, 24-26 January 1995, Prague, Czech Republic.

40. Vlasblom, W.J. & Miedema, S.A., "A Theory for Determining Sedimentation and Overflow Losses in Hoppers (Adobe Acrobat 4.0 PDF-File 304 kB)". Proc. WODCON IV, November 1995, Amsterdam, The Netherlands 1995.

41. Miedema, S.A., "Production Estimation Based on Cutting Theories for Cutting Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 423 kB)". Proc. WODCON IV, November 1995, Amsterdam, The Netherlands 1995. Additional Specific Energy and Production Graphs. (Adobe Acrobat 4.0 PDF-File 145 kB).

42. Riet, E.J. van, Matousek, V. & Miedema, S.A., "A Theoretical Description and Numerical Sensitivity Analysis on Wilson's Model for Hydraulic Transport in Pipelines (Adobe Acrobat 4.0 PDF-File 50 kB)". Journal of Hydrology & Hydromechanics, Slovak Ac. of Science, Bratislava, June 1996.

43. Miedema, S.A. & Vlasblom, W.J., "Theory for Hopper Sedimentation (Adobe Acrobat 4.0 PDF-File 304 kB)". 29th Annual Texas A&M Dredging Seminar. New Orleans, June 1996.

44. Miedema, S.A., "Modeling and Simulation of the Dynamic Behavior of a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 318 kB)". 17th Annual Meeting & Technical Conference of the Western Dredging Association. New Orleans, June 1996.

45. Miedema, S.A., "Education of Mechanical Engineering, an Integral Vision". Faculty O.C.P., Delft University of Technology, 1997 (in Dutch).

46. Miedema, S.A., "Educational Policy and Implementation 1998-2003 (versions 1998, 1999 and 2000) (Adobe Acrobat 4.0 PDF_File 195 kB)". Faculty O.C.P., Delft University of Technology, 1998, 1999 and 2000 (in Dutch).

47. Keulen, H. van & Miedema, S.A. & Werff, K. van der, "Redesigning the curriculum of the first three years of the mechanical engineering curriculum". Proceedings of the International Seminar on Design in Engineering Education, SEFI-Document no.21, page 122, ISBN 2-87352-024-8, Editors: V. John & K. Lassithiotakis, Odense, 22-24 October 1998.

48. Miedema, S.A. & Klein Woud, H.K.W. & van Bemmel, N.J. & Nijveld, D., "Self Assesment Educational Programme Mechanical Engineering (Adobe Acrobat 4.0 PDF-File 400 kB)". Faculty O.C.P., Delft University of Technology, 1999.

49. Van Dijk, J.A. & Miedema, S.A. & Bout, G., "Curriculum Development Mechanical Engineering". MHO 5/CTU/DUT/Civil Engineering. Cantho University Vietnam, CICAT Delft, April 1999.

50. Miedema, S.A., "Considerations in building and using dredge simulators (Adobe Acrobat 4.0 PDF-File 296 kB)". Texas A&M 31st Annual Dredging Seminar. Louisville Kentucky, May 16-18, 1999.

51. Miedema, S.A., "Considerations on limits of dredging processes (Adobe Acrobat 4.0 PDF-File 523 kB)". 19th Annual Meeting & Technical Conference of the Western Dredging Association. Louisville Kentucky, May 16-18, 1999.

52. Miedema, S.A. & Ruijtenbeek, M.G. v.d., "Quality management in reality", "Kwaliteitszorg in de praktijk". AKO conference on quality management in education. Delft University of Technology, November 3rd 1999.

53. Miedema, S.A., "Curriculum Development Mechanical Engineering (Adobe Acrobat 4.0 PDF-File 4 MB)". MHO 5-6/CTU/DUT. Cantho University Vietnam, CICAT Delft, Mission October 1999.

54. Vlasblom, W.J., Miedema, S.A., Ni, F., "Course Development on Topic 5: Dredging Technology, Dredging Equipment and Dredging Processes". Delft University of Technology and CICAT, Delft July 2000.

55. Miedema, S.A., Vlasblom, W.J., Bian, X., "Course Development on Topic 5: Dredging Technology, Power Drives, Instrumentation and Automation". Delft University of Technology and CICAT, Delft July 2000.

56. Randall, R. & Jong, P. de & Miedema, S.A., "Experience with cutter suction dredge simulator training (Adobe Acrobat 4.0 PDF-File 1.1 MB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

57. Miedema, S.A., "The modelling of the swing winches of a cutter dredge in relation with simulators (Adobe Acrobat 4.0 PDF-File 814 kB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

58. Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the position of backhoe dredges (Adobe Acrobat 4.0 PDF-File 257 kB)". Texas A&M 32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.

59. Miedema, S.A., "Automation of a Cutter Dredge, Applied to the Dynamic Behaviour of a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 254 kB)". Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.

60. Heggeler, O.W.J. ten, Vercruysse, P.M., Miedema, S.A., "On the Motions of Suction Pipe Constructions a Dynamic Analysis (Adobe Acrobat 4.0 PDF-File 110 kB)". Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.

61. Miedema, S.A. & Zhao Yi, "An Analytical Method of Pore Pressure Calculations when Cutting Water Saturated Sand (Adobe Acrobat PDF-File 2.2 MB)". Texas A&M 33nd Annual Dredging Seminar, June 2001, Houston, USA 2001.

62. Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport (Adobe Acrobat PDF-File 246 kB)". 21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.

63. Zhao Yi, & Miedema, S.A., "Finite Element Calculations To Determine The Pore Pressures When Cutting Water Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB)". CEDA Dredging Day 2001, November 2001, Amsterdam, The Netherlands.

64. Miedema, S.A., "Mission Report Cantho University". MHO5/6, Phase Two, Mission to Vietnam by Dr.ir. S.A. Miedema DUT/OCP Project Supervisor, 27 September-8 October 2001, Delft University/CICAT.

65. (Zhao Yi), & (Miedema, S.A.), "

" (Finite Element Calculations To Determine The Pore Pressures When Cutting Water

Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB))". To be published in 2002.

66. Miedema, S.A., & Riet, E.J. van, & Matousek, V., "Theoretical Description And Numerical Sensitivity Analysis On Wilson Model For Hydraulic Transport Of Solids In Pipelines (Adobe Acrobat PDF-File 147 kB)". WEDA Journal of Dredging Engineering, March 2002.

67. Miedema, S.A., & Ma, Y., "The Cutting of Water Saturated Sand at Large Cutting Angles (Adobe Acrobat PDF-File 3.6 MB)". Proc. Dredging02, May 5-8, Orlando, Florida, USA.

68. Miedema, S.A., & Lu, Z., "The Dynamic Behavior of a Diesel Engine (Adobe Acrobat PDF-File 363 kB)". Proc. WEDA XXII Technical Conference & 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.

69. Miedema, S.A., & He, Y., "The Existance of Kinematic Wedges at Large Cutting Angles (Adobe Acrobat PDF-File 4 MB)". Proc. WEDA XXII Technical Conference & 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.

70. Ma, Y., Vlasblom, W.J., Miedema, S.A., Matousek, V., "Measurement of Density and Velocity in Hydraulic Transport using Tomography". Dredging Days 2002, Dredging without boundaries, Casablanca, Morocco, V64-V73, 22-24 October 2002.

71. Ma, Y., Miedema, S.A., Vlasblom, W.J., "Theoretical Simulation of the Measurements Process of Electrical Impedance Tomography". Asian Simulation Conference/5th International Conference on System Simulation and Scientific Computing, Shanghai, 3-6 November 2002, p. 261-265, ISBN 7-5062-5571-5/TP.75.

72. Thanh, N.Q., & Miedema, S.A., "Automotive Electricity and Electronics". Delft University of Technology and CICAT, Delft December 2002.

73. Miedema, S.A., Willemse, H.R., "Report on MHO5/6 Mission to Vietnam". Delft University of Technology and CICAT, Delft Januari 2003.

74. Ma, Y., Miedema, S.A., Matousek, V., Vlasblom, W.J., "Tomography as a Measurement Method for Density and Velocity Distributions". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

75. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of a Development of a Density Wave in a Long Slurry Pipeline". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

76. Miedema, S.A., Lu, Z., Matousek, V., "Numerical simulation of the development of density waves in a long pipeline and the dynamic system behavior". Terra et Aqua, No. 93, p. 11-23.

77. Miedema, S.A., Frijters, D., "The Mechanism of Kinematic Wedges at Large Cutting Angles - Velocity and Friction Measurements". 23rd WEDA Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.

78. Tri, Nguyen Van, Miedema, S.A., Heijer, J. den, "Machine Manufacturing Technology". Lecture notes, Delft University of Technology, Cicat and Cantho University Vietnam, August 2003.

79. Miedema, S.A., "MHO5/6 Phase Two Mission Report". Report on a mission to Cantho University Vietnam October 2003. Delft University of Technology and CICAT, November 2003.

80. Zwanenburg, M., Holstein, J.D., Miedema, S.A., Vlasblom, W.J., "The Exploitation of Cockle Shells". CEDA Dredging Days 2003, Amsterdam, The Netherlands, November 2003.

81. Zhi, L., Miedema, S.A., Vlasblom, W.J., Verheul, C.H., "Modeling and Simulation of the Dynamic Behaviour of TSHD's Suction Pipe System by using Adams". CHIDA Dredging Days, Shanghai, China, november 2003.

82. Miedema, S.A., "The Existence of Kinematic Wedges at Large Cutting Angles". CHIDA Dredging Days, Shanghai, China, november 2003.

83. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of the Development of Density Waves in a Long Pipeline and the Dynamic System Behaviour". Terra et Aqua 93, December 2003.

84. Miedema, S.A. & Frijters, D.D.J., "The wedge mechanism for cutting of water saturated sand at large cutting angles". WODCON XVII, September 2004, Hamburg Germany.

85. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "The development of a concept for accurate and efficient dredging at great water depths". WODCON XVII, September 2004, Hamburg Germany.

86. Miedema, S.A., "THE CUTTING MECHANISMS OF WATER SATURATED SAND AT SMALL AND LARGE CUTTING ANGLES". International Conference on Coastal Infrastructure Development - Challenges in the 21st Century. HongKong, november 2004.

87. Ir. M. Zwanenburg , Dr. Ir. S.A. Miedema , Ir J.D. Holstein , Prof.ir. W.J.Vlasblom, "REDUCING THE DAMAGE TO THE SEA FLOOR WHEN DREDGING COCKLE SHELLS". WEDAXXIV & TAMU36, Orlando, Florida, USA, July 2004.

88. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "A new concept for accurate and efficient dredging in deep water". Ports & Dredging, IHC, 2005, E163.

89. Miedema, S.A., "Scrapped?". Dredging & Port Construction, September 2005. 90. Miedema, S.A. & Vlasblom, W.J., " Bureaustudie Overvloeiverliezen". In opdracht

van Havenbedrijf Rotterdam, September 2005, Confidential. 91. He, J., Miedema, S.A. & Vlasblom, W.J., "FEM Analyses Of Cutting Of Anisotropic

Densely Compacted and Saturated Sand", WEDAXXV & TAMU37, New Orleans, USA, June 2005.

92. Miedema, S.A., "The Cutting of Water Saturated Sand, the FINAL Solution". WEDAXXV & TAMU37, New Orleans, USA, June 2005.

93. Miedema, S.A. & Massie, W., "Selfassesment MSc Offshore Engineering", Delft University of Technology, October 2005.

94. Miedema, S.A., "THE CUTTING OF WATER SATURATED SAND, THE SOLUTION". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

95. Miedema, S.A., "La solution de prélèvement par désagrégation du sable saturé en eau". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

96. Miedema, S.A. & Vlasblom, W.J., "THE CLOSING PROCESS OF CLAMSHELL DREDGES IN WATER-SATURATED SAND". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

97. Miedema, S.A. & Vlasblom, W.J., "Le processus de fermeture des dragues à benne preneuse en sable saturé". CEDA African Section: Dredging Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.

98. Miedema, S.A. "THE CUTTING OF WATER SATURATED SAND, THE SOLUTION". The 2nd China Dredging Association International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

99. Ma, Y, Ni, F. & Miedema, S.A., "Calculation of the Blade Cutting Force for small Cutting Angles based on MATLAB". The 2nd China Dredging Association

International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

100. ,"" (download). The 2nd China Dredging

Association International Conference & Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou, China, May 17-18 2006.

101. Miedema, S.A. , Kerkvliet, J., Strijbis, D., Jonkman, B., Hatert, M. v/d, "THE DIGGING AND HOLDING CAPACITY OF ANCHORS". WEDA XXVI AND TAMU 38, San Diego, California, June 25-28, 2006.

102. Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K. & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE, ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.

103. Miedema, S.A., "Polytechnisch Zakboek 51ste druk, Hoofdstuk G: Werktuigbouwkunde", pG1-G88, Reed Business Information, ISBN-10: 90.6228.613.5, ISBN-13: 978.90.6228.613.3. Redactie: Fortuin, J.B., van Herwijnen, F., Leijendeckers, P.H.H., de Roeck, G. & Schwippert, G.A.

104. MA Ya-sheng, NI Fu-sheng, S.A. Miedema, "Mechanical Model of Water Saturated Sand Cutting at Blade Large Cutting Angles", Journal of Hohai University Changzhou, ISSN 1009-1130, CN 32-1591, 2006. 绞刀片大角度切削水饱和沙的力学模型, 马亚生[1] 倪福生[1] S.A.Miedema[2], 《河海大学常州分校学报》-2006年20卷3期 -59-61页

105. Miedema, S.A., Lager, G.H.G., Kerkvliet, J., “An Overview of Drag Embedded Anchor Holding Capacity for Dredging and Offshore Applications”. WODCON, Orlando, USA, 2007.

106. Miedema, S.A., Rhee, C. van, “A SENSITIVITY ANALYSIS ON THE EFFECTS OF DIMENSIONS AND GEOMETRY OF TRAILING SUCTION HOPPER DREDGES”. WODCON ORLANDO, USA, 2007.

107. Miedema, S.A., Bookreview: Useless arithmetic, why environmental scientists can't predict the future, by Orrin H. Pilkey & Linda Pilkey-Jarvis. Terra et Aqua 108, September 2007, IADC, The Hague, Netherlands.

108. Miedema, S.A., Bookreview: The rock manual: The use of rock in hydraulic engineering, by CIRIA, CUR, CETMEF. Terra et Aqua 110, March 2008, IADC, The Hague, Netherlands.

109. Miedema, S.A., "An Analytical Method To Determine Scour". WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.

110. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells". WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.

111. Miedema, S.A., "An Analytical Approach To The Sedimentation Process In Trailing Suction Hopper Dredgers". Terra et Aqua 112, September 2008, IADC, The Hague, Netherlands.

112. Hofstra, C.F., & Rhee, C. van, & Miedema, S.A. & Talmon, A.M., "On The Particle Trajectories In Dredge Pump Impellers". 14th International Conference Transport & Sedimentation Of Solid Particles. June 23-27 2008, St. Petersburg, Russia.

113. Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells". WEDA Journal of Dredging Engineering, December 2008.

114. Miedema, S.A., "New Developments Of Cutting Theories With Respect To Dredging, The Cutting Of Clay And Rock". WEDA XXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.

115. Miedema, S.A., "A Sensitivity Analysis Of The Scaling Of TSHD's". WEDA XXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.

116. Liu, Z., Ni, F., Miedema, S.A., “Optimized design method for TSHD’s swell compensator, basing on modelling and simulation”. International Conference on Industrial Mechatronics and Automation, pp. 48-52. Chengdu, China, May 15-16, 2009.

117. Miedema, S.A., "The effect of the bed rise velocity on the sedimentation process in hopper dredges". Journal of Dredging Engineering, Vol. 10, No. 1 , 10-31, 2009.

118. Miedema, S.A., “New developments of cutting theories with respect to offshore applications, the cutting of sand, clay and rock”. ISOPE 2010, Beijing China, June 2010.

119. Miedema, S.A., “The influence of the strain rate on cutting processes”. ISOPE 2010, Beijing China, June 2010.

120. Ramsdell, R.C., Miedema, S.A., “Hydraulic transport of sand/shell mixtures”. WODCON XIX, Beijing China, September 2010.

121. Abdeli, M., Miedema, S.A., Schott, D., Alvarez Grima, M., “The application of discrete element modeling in dredging”. WODCON XIX, Beijing China, September 2010.

122. Hofstra, C.F., Miedema, S.A., Rhee, C. van, “Particle trajectories near impeller blades in centrifugal pumps. WODCON XIX, Beijing China, September 2010.

123. Miedema, S.A., “Constructing the Shields curve, a new theoretical approach and its applications”. WODCON XIX, Beijing China, September 2010.

124. Miedema, S.A., “The effect of the bed rise velocity on the sedimentation process in hopper dredges”. WODCON XIX, Beijing China, September 2010.