SUMMARY/OVERVIEW

PHASE I REPORT

INTIAL DESIGN AND ENGINEERING-TECHNICAL FEASIBILITY

RE: GEOTHERMIC FUEL CELL IN-SITU APPLICATIONS FOR RECOVERY OF UNCOVENTIONAL HYDROCARBONS

WORK PERFORMED BY: U.S. DEPARTMENT OF ENERGY- BATTELLE/PACIFIC NORTHWEST NATIONAL LABS. (Work completed June 7, 2010).

Introduction

Independent Energy Partners Inc. (IEP) engaged the services of Battelle/Pacific Northwest National Labs (PNNL) to conduct initial design, engineering, analysis and modeling to establish the technical feasibility of IEP’s patented Geothermic Fuel Cell (GFC) technology for recovery of unconventional hydrocarbons. The basis on which PNNL began its work was the review of IEP’s US Patent No. 6,684,948 B1-Apparatus and Method for Heating Subterranean Formations Using Fuel Cells, and US Patent No. 7,182,132 Linearly Scalable Geothermic Fuel Cells, along with accompanying conceptual drawings for the Geothermic Fuel Cell process. Work began on the Phase I effort in September 2008 and was completed in June 2010. This document contains highlights and excerpts from the Phase I Report.1 .

Objective

The GFC in-situ applications for hydrocarbon recovery are similar to Shell Oil Company’s In-Situ Conversion Process (ICP), which utilizes electrical resistance heaters. The predecessor to the ICP application was developed in Sweden during the 1940s wherein significant oil and gas was produced for that county at that time. Shell has since recently reaffirmed the electrical resistance technology and successfully demonstrated the ICP process in oil shale another other unconventional hydrocarbons. Therefore the basic process of in-situ, uniform, conductive heating for production of hydrocarbons has been proven leaving only the design, economic and environmental sustainability of heater technology to be evaluated. Accordingly, the primary objective of Phase I work is directed at the packaging and operation of existing solid oxide fuel cell (SOFC) technology for the GFC configuration and planned applications. Phase I work focused on several key elements in developing a workable design, namely;

• how to provide robust seals throughout the length of a GFC stack, • how to evenly deliver fuel and air to the cells in a 500 foot long GFC stack, • how to electrically connect stack segments and extract electricity, • how to achieve start-up, and • how to control the stack temperature throughout its length.

                                                                                                                         1  The  complete  report  is  available  to  interested  parties  following  execution  of  a  Non-­‐Disclosure  Agreement.  

 

Each of these design challenges has been satisfactorily resolved. The following brief introductory sub-sections review how these resolutions have been engineered. Detailed engineering, design and analysis was also conducted in areas of SOFC cell performance, thermal/structural, fluid dynamics and systems engineering for balance of plant surface equipment, including fuel cycles and related topics. In addition, extensive modeling work was performed utilizing PNNL’s proprietary Subsurface Transport Over Multiple Phases (STOMP) code to analyze the GFC in both startup and production modes for oil shale applications. All simulations described in the final report were executed with STOMP-OS, an operational mode of the STOMP series of simulators developed for oil shale by the Pacific Northwest National Laboratory. The STOMP-OS system of nonlinear coupled governing equations comprise conservation equations for thermal energy and component mass; and a volumetric molar density equilibrium equation to analyze kerogen distillation, related products produced, timeline and yields in an in-situ environment.

Seals

The sealing challenge was met by adopting an invention from another project being conducted at Pacific Northwest National Labs. Current planar, anode-supported SOFC technology is illustrated in Figure 1-1.

cathode

anode-supported cell

cell frame

glass seal

interconnect mesh

separator plate (welded to cell frame)

Insulating seals (glass or compressive) are required between cell structures because welded steel frames are at potential of local cell anode.

cathode

anode-supported cell

cell frame

glass seal

interconnect mesh

separator plate (welded to cell frame)

Insulating seals (glass or compressive) are required between cell structures because welded steel frames are at potential of local cell anode.

Figure 1-1. Schematic representing current SOFC technology.

The cell is attached to a steel cell frame, which is then welded to a steel separator plate. Because the anode of the cell is electrically connected to the separator plate, the entire metal structure is at the electrical potential of the anode. When the repeat units are assembled together to form a stack, the steel frame structures must be kept isolated from each other to prevent electrical shorting from cell-to-cell. In current practice the repeat units are bonded using glass or compressive insulating seals. Because the fuel and oxidizer gas manifolds are contained in the frame structure, these seals necessarily have complex shapes and have proven to be problematic. These multiple manifolds must be effectively sealed to prevent cross-leaks of air and fuel, which cause local hot spots and can lead to destruction of the stack. The entire structure must be kept in compression for the seals to be effective, a requirement that would be especially challenging for the GFC stack sections, which are 15 feet long. The original patent envisioned steel compression rods passing through the periphery of the cell frames and applying compression to the cell frames and seals within the stack section, as illustrated in Figure 1-2.

Figure 1-2. Original concept with perforated plates and compression rods.

The new concept is illustrated in Figure 1-3. In this design, the steel separator plate, like the cell itself, is bonded to a steel frame using an insulating glass seal. When the repeat units are stacked, the cells, separator plates and interconnect meshes are electrically isolated from the frame components so that the frames can be welded together, forming a rigid structure surrounding and supporting the inner column of cells and interconnects.

interconnect mesh

separator plate frame (welded to cell frame)

separator plate

glass seal

separator plateframe

Cell frames and separator plate frames can be welded together because both cells and separator plates are isolated from their frames by glass seals.

interconnect mesh

separator plate frame (welded to cell frame)

separator plate

glass seal

separator plateframe

Cell frames and separator plate frames can be welded together because both cells and separator plates are isolated from their frames by glass seals.

Figure 1-3. Schematic of welded frame structure concept.

Compression rods are thus eliminated and the glass seals that bond the cells and separator plates to their respective frames will have simple shapes and add reliability over the more complex seals of the current technology.

Gas Distribution

It is important that all cells - approximately 10,000 in a 500 foot long stack - are supplied with the same flow of fuel (hydrogen) to the anodes and air to the cathodes. Otherwise, the starved sections will run cooler than intended and the well-fed sections hotter.

One initial concept for gas distribution in the GFC stack was to provide precisely sized orifices at the fuel and air entrance to each cell, as illustrated in Figures 1-4 and 1-5 (a). These orifices would connect to the higher-pressure gas inlet manifolds.

Insert  C ontaining  O rifice  for  F low  C ontrol

•Walls of high-pressure inlet chimneys are penetrated only by machined orifices.

•Joints that would otherwise require compressive seals are now welded seams.

• Nozzle part can be welded into frame plate prior to stack assembly.

gas inlet chimney

Figure 1-4. Original machined orifice concept.

The pressure drop across each orifice would control the gas flow rate. Because the pressure in the manifolds would decrease as gas was bled off down through the stack, the orifices would have to have a range of diameters over the length of the stack. Though technically feasible from a gas distribution standpoint, obvious disadvantages of this approach include probable high cost and the potential for plugging of the 20,000 or so relatively small, precisely sized orifices.

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

small, precise orifice required for each cell

cell

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

lowpressuresupplyplenum

large orifice controls flow to plenum

(a) (b)

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

small, precise orifice required for each cell

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

small, precise orifice required for each cell

cell

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

lowpressuresupplyplenum

large orifice controls flow to plenum

cell

incominghigh

pressuregas

manifold

lowpressure

streamto each

cell

lowpressuresupplyplenum

large orifice controls flow to plenum

(a) (b)

Figure 1-5. (a) Schematic of gas distribution scheme requiring precise orifices at every cell. (b) Scheme using low pressure plenum supplying an entire stack section. Here the pressure drop

is controlled by a few large orifices into the supply plenum.

However, a refinement of this approach alleviates those concerns. Each 15 foot stack module will contain a plenum that will be supplied from the main inlet manifold and will, in turn, supply the individual cells within the module, as illustrated in Figure 1-5 (b). Most of the flow control and pressure drop will be handled by several relatively large holes in the wall between the plenum and the manifold. The orifices connecting the cells to the plenum can then be made relatively large and will not be critical to flow control. The design calls for holes drilled or punched into the plenum walls, with spacing determined by the manifold pressure in the local stack module.

The resulting design, not only dramatically reduces GFC stack materials required and corresponding savings, but provides a simple and predicable method of gas distribution within the GFC stack. Figures 1-6, 1-7 and 1-8 show design modifications from patent concept to the design developed during Phase I.

Geothermic Fuel Cell stack—25 cells

Fuel cells

Gas/air/exhaust conduits

Electrode wafer

7.5 inch diameter

5 in.

Pitch = 5 cells per inch

Figure 1-6 Geothermic Fuel Cell—Patent Concept Drawing

Figure 1-7 New Design with Plenum Features for Gas Flow Conduits

Figure 1-8 New GFC Stack Design with Outer Casing, Welded Cell Stack and Electrical Conductor

Electrical Wiring & Power Management

The original concept described in the patents had all of the cells in the 500 foot stack connected in series. This approach would accumulate potential to over 5000 volts at the top of the stack. Preventing dielectric breakdown with 5000 volts potential at the high temperatures and in a steam environment would present a major technological barrier. The current design avoids this problem by connecting sections of stack in parallel.

The series-parallel arrangement is illustrated schematically in Figure 1-9. Within each 15 foot stack module, the cells and interconnect assemblies form a continuous series circuit. The central cell/interconnect column is electrically insulated from the surrounding welded frame structure by the glass seals discussed previously. The welded frame structure contains a copper conductor and is itself isolated from the casing by electrical insulation. Each pair of 15 foot stack modules will be connected in series through a coupling. Each 30 foot pair will be connected to the current carrying bus through a different type of coupling with the top of the lower cell/interconnect column connected to the copper conductor and the bottom of the upper cell/interconnect column connected to the casing.

The casings and coupling sleeves form a continuous conductor at ground potential. The copper current conductor and the welded frame structure form a continuous conductor at approximately 300 volts potential. The voltage in each 30 foot cell/interconnect series builds from ground potential at the bottom to near 300 volts at the top, where it adds its approximately 46 amperes current into the 300 volt buss. The current in the copper buss increases at each parallel coupling until it reaches approximately 1460 amperes at the top of the 500 foot stack.

Current return is accommodated through the grounded exterior steel casing. The original design concept envisioned a current return cable, which the new electrical design has eliminated.

This wiring scheme enables the electrical power to be extracted from the stack at a manageable maximum voltage and with minimal ohmic losses and external and internal cabling eliminated or minimized.

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Figure 1-9. Series-parallel wiring scheme for GFC stack.

Stack Start-Up and Temperature Control

SOFCs inherently become more electrochemically active as temperature increases, and therefore tend to produce even more heat, so active temperature control is necessary. SOFC stacks of the types for above-ground applications are typically contained in insulated boxes and are instrumented with several thermocouples. Temperatures are controlled by adjusting the flow of cathode air, which is supplied in excess and carries away heat. Another possible approach to controlling stack temperature is to adjust stack voltage as less heat is produced at higher voltages.

One concern with the GFC concept was that some stack sections would inevitably become hotter than others, whether during start-up or during sustained operation due to variability in thermal conductivity of the surrounding geology. However, it will not be possible to selectively increase either air flow or voltage in hotter sections of the GFC stack. Instead, hotter sections will be prevented from overheating by limiting the flow of air to the entire stack so that all cells in the stack are oxygen limited. Cells slightly hotter than average will deplete the oxygen over a shorter path length than average. The air flow rate will need to be sufficient such that the stack produces heat at the rate that heat is absorbed by the formation. As the temperatures increase in the surrounding formation, the stack heating rate can be gradually decreased by increasing the overall stack voltage or by further decreasing the air flow rate or by a combination of both.

Solid oxide fuel cells do not contain any noble metal catalysts or other expensive ingredients that enable activation at low temperatures in the manner of some other fuel cell types (PEM cells, etc.). Therefore SOFCs must be pre-heated to a minimum operating temperature (500 C.) before they will begin oxidizing fuel and producing electricity and heat. The original operating concept involved circulating hot air or other gases from the surface to pre-heat the GFC stack. Near-field computer modeling showed that this approach was not practical. Various concepts were explored before the development of a viable solution as discussed below.

Start-up can be accomplished by inserting electric resistance heaters into the annulus between the inner and outer casings. Thermal modeling indicates that three heaters, each 30 feet long and producing 20 kW each would be sufficient to start up the stack within three days. Starting at the bottom of the stack, the heaters will be withdrawn up the stack as each section heats up and becomes active. Additionally, a 100 kW gas pre-heater was considered at the top of the stack and would continue running after start-up to prevent the cool inlet air and hydrogen from quenching (over-cooling) the top of the stack.

It is expected that the size of this pre-heater can be decreased significantly or omitted by improving the heat exchange between the outgoing and incoming gasses just above the top of the stack. Optimization of the above scenario is planned in Phase II with an objective of using a

different scheme for startup than the electrical resistance heaters and deleting the requirement for a gas pre-heater.

Startup Design and Protocol Alternatives

The standard startup design and protocol yields system startup in approximately 3 days, but uses an operating voltage that results in a high current density and yields relatively high operational stack-frame temperatures. Longevity of the fuel cell material decreases with higher current density and higher fuel cell temperatures; therefore, alternatives to the standard startup design and protocol were investigated. Reducing the current density requires increasing the operational voltage, which correspondingly reduces the fuel cell heat generation rate. The fuel cell heat generation rate can be increased by increasing the maximum temperature or limiting oxidant flow.

 

Figure 1-10. Temperature profiles along the heat exchanger and fuel cell stack 4.0 days after heater ignition for the gravel (i.e., fill between outer casing and borehole), fuel inlet, fuel outlet,

air outlet, stack frame, insulation, inner casing, and outer casing.

More in-depth review of the analysis and computer modeling is available in the compete Phase I Report.

Production Modeling –due to the highly analytical and extensive nature of the ‘far-field’ production modeling, only excerpts are provided below in connection with that portion of the Phase I Report. This work was completed as a parallel task and published in May 2010 by Battelle/Pacific Northwest National Labs titled Numerical Investigations for Field Deployment for Geothermic Well Heat Source for Oil Shale Pyrolysis and Production Technology in connection with IEP’s Phase I Report. A copy of this report is available to interested parties.

Production Modeling (Excerpt)

One concept for the in-situ production of oil shale from the Green River Formation, within the Piceance Creek Basin, in northwestern Colorado involves using a down-hole fuel-cell stack (geothermic well) as a heat source for kerogen pyrolysis (i.e., kerogen production via in-situ thermal stimulation). This report describes a newly developed numerical simulator, STOMP-OS (Subsurface Transport Over Multiple Phases - Oil Shale), for modeling the in-situ production of kerogen via thermal stimulation and its application to field configurations. The principal objectives of the investigation where to use numerical simulation: 1) to improve the understanding of subsurface processes associated with kerogen production via thermal stimulation, 2) to predict the production performance of various geothermic well configurations and operating temperatures, and 3) compare the simulator results against a previously conducted field experiments by Shell Oil Compnay..

Shell applied the commercial thermal reservoir simulator STARS, (CMG 2003) to model the MDP[s] field experiment. STARS (Steam, Thermal, and Advanced processes Reservoir

Simulator) is a commercial numerical simulator for modeling of reservoir processes. It allows for user defined chemical reaction kinetics and chemical components in one of four phases (i.e.,

gas, nonaqueous phase liquid, aqueous, and solid). The Shell production results for the MDP[s] field experiment were published (Vinegar 2006) with simulation data generated by STARS. No details of the simulations were provided, but the simulation results show excellent agreement

with both field recovery rates and integrals for liquid oils and gases.

Numerical grid within a repeating hexagonal pattern of geothermic wells and a central producing well

To investigate whether oil recovery yields of at least 60% of Fischer Assay could be achieved at lower hexagonal spacing, a series of simulations were conducted using a 10-m (32.8-ft) hexagonal spacing. A 10-m hexagonal spacing translates to 53% of the surface area of the 45-ft spacing. The time to produce 99% of the kerogen drops from 5.58 years in the 45-ft hex spacing case to 3.11 years in the 10-m hex spacing case, which is a reduction of about 56%. This indicates that for a given geothermic well temperature the kerogen production rate is proportional to the hexagonal pattern area. Comparing the time to produce 99% of the kerogen for the 450˚ C geothermic well temperature between the 10-m and 5-m hexagonal spacing a time reduction of 29% is observed for a hexagon area reduction of 25%. The component mass production profiles look similar between the 45-ft and 10-m hexagonal spacing cases.

Component mass balance during production for a 45-ft hexagonal pattern spacing with maximum geothermic well temperatures of 650 C

While this work provides valuable insight and validates the GFC for in-situ applications in oil shale, it was completed with certain simplifying assumptions and did not include such factors as fracing for more accurate predictions and shorter heat up timelines and corresponding production. IEP has arranged for further analysis to be done by Idaho National Labs in Phase II that will include fracing and a number of other geomechanical considerations for a more complete and accurate assessment of these operating variables.

Conclusions

The current design, adopting certain features developed from another project at PNNL, results in several significant advantages over the initial design based on patent concept drawings. In addition to dramatic reduction in GFC stack material requirements, the critical need to provide robust seals was addressed.

Design developments and features added within plenum sections resulted in the ability to deliver fuel and air evenly throughout the length of the GFC stack.

In addition to establishing intercell electrical interface details, the combined series/parallel designs adopted for connecting stack segments and extracting electrical power provides technically feasible methods to successfully address these items.

A technically feasible startup scenario of the GFC stack was ultimately achieved through the use of electrical resistance heaters resulting in stack start up in approximately 4 days.

Operational considerations were established for the control of stack temperature throughout its length. A combination of oxygen content and voltage level control and/or regulation will enable temperature control during operation of GFC stacks.

Numerous other design, engineering and operational considerations were addressed during the Phase I effort. While all key elements for a complete and operational GFC stack system were evaluated and feasible design decisions reached, design refinements and optimization opportunities exist for a number of areas such as startup scenarios, fuel cycles and manufacturing engineering for optimum, cost effective automated industrial manufacturing methods.

Accordingly, in addition to lab, bench and GFC module testing, Phase II efforts will include analysis and modeling to evaluate alternatives for optimization and design refinements.