Practical Consideration Of Fuel Cells Engineering Essay

Practical Consideration Of Fuel Cells Engineering Essay

Introduction

Soon, legion states in the universe are seeking to pull out oil and gas from deep H2O. More operations are been carried out further from shore and field installations. Therefore, operators are progressively integrating sub production systems. However, the chief issue is that power coevals systems are required to be used in the deep surface of the sea, and this requires the use of subsea equipment. Fuel cells can be used in such state of affairs, where H or natural gas can be fed as fuel for the fuel cells. Furthermore, air or O can be used as the oxidizers. Briefly, fuel cells use electrochemical engines to change over the chemical energy into an electrical energy to be used for subsea power demands. This essay will look into the feasiblenesss of operation of system under force per unit area and determine types of fuel cell to be used in such conditions.

Practical consideration of Fuel cells in subsea conditions

Figure – Schematic of a subsea landscape [ 20 ]

The figure above indicates a subsea landscape giving a position of the operations that undergo in the deepness of the sea that may demand power demands. The oxidization reaction in all types of fuel cells requires the presence of air or O as oxidizers. If fuel cell systems are to be used in deepness of the sea it will necessitate a provender of oxidizer in order to run. Therefore, under force per unit area, the fuel cell system will work by pressurization of the air and dehumidifying it. Furthermore, an addition on the burden on the fuel cell systems will take topographic point, which will hold an consequence in the fuel cell public presentation, as the efficiency will be reduced well. Fuel cell can be used to replace conventional energy storage devices used presently, such as batteries, to provide a uninterrupted and changeless beginning of energy. Currently, regenerative liquid red-ox, lead-acid, Silver-zinc, sodium-beta and lithium-ion batteries are used to supply energy for the equipmentaa‚¬a„?s in subsea. The issues related utilizing batteries are legion, including that they are non environmentally friendly due to most of them being disposed off after usage. Furthermore, batteries lack the capablenesss to supply a changeless sum of energy. Medium to high temperature fuel cells, such as solid oxide fuel cell ( SOFC ) , liquefied carbonate fuel cell ( MCFC ) and phosphorous acid fuel cells ( PAFC ) can be used as a CHP ( combined heat and power ) systems in order to bring forth electricity in subsea conditions. Natural gas can besides be used straight in order to fuel high temperature SOFC. Though, this will ensue in add-on complications due to the high temperature of the system. However, utilizing a low to intercede temperature fuel cells, natural gas can be converted to hydrogen through the usage of a reformist, and so fed to environmentally friendly proton exchange membrane fuel cell ( PEMFC ) through gas purification membranes and can be used to extinguish toxicants such as, CO and SOx constituents by filtration. This would ideally eliminate the demand for pipes to present natural gas off from subsea wellsprings.

Talk about more issues of PAFC, MCFC and SOFC in subsea.The figure below comparisons between the common types of fuel cells.

Referee: hypertext transfer protocol: //www.efdsystems.org/Portals/25/LLNL-TR-424663 % 20Subsurface % 20Hybrid % 20Power % 20Options % 20for % 20Oil % 20 & amp ; % 20Gas % 20Production.pdf

Figure – Features of assorted types of fuel cells.18

Referee: hypertext transfer protocol: //www.efdsystems.org/Portals/25/LLNL-TR-424663 % 20Subsurface % 20Hybrid % 20Power % 20Options % 20for % 20Oil % 20 & amp ; % 20Gas % 20Production.pdf

Regenerative fuel cells systems are complex, as the system used does non depend on a specific type of fuel cell instead would necessitate an substructure that is able to present the H fuel to assorted fuel cells in used. Although, a challenge being that there is no bing substructure for such H fuel bringing and therefore, it comes with high electricity cost. Regenerative fuel cells operate by firing the stored H and O and intern bring forthing electricity and H2O. But, it has the energy punishment, which is dividing pure H2O from saltwater ( i.e. theoretical lower limit of 2.5 Wh/gal, and realistic values of 24-36 Wh/gal which is required for separation with rearward osmosis ) . Following the oxidization of H in the fuel cell, the produced pure H2O gets stored. In reloading procedure, the stored H2O gets electrolysed, organizing O and H, which is besides stored. Following this procedure the gases are stored in cylinders at a force per unit area of 10,000 lbs per square inch ( Pisa ) .

The base of this fuel cell system is a proton exchange member fuel cell ( PEMFC ) . The air cathode, which is used here, has a dispersed Pt accelerator on a porous C substrate, The H anode which is used here includes spread Pt or platinum-ruthenium accelerator on a porous substrate it besides consists of a electrolyte which is a polymeric cation-exchange membrane made of a stuff such as NafionTM. The operating temperature such a PEMFC is in the scope 30-120oC. The unfastened circuit electromotive force of this fuel cell is about 1.2 V, but under burden the operating electromotive force expected in the scope of 0.5-0.7V. The power denseness, specific energy and energy denseness of this type of fuel system are approximated to be

17-27 W/kg, 326 Wh/kg and 209 Wh/L severally. This fuel system provides greater specific energy and energy denseness than province of the art batteries. However, the fuel system lacks nice power denseness. That is, it has restrictions with power denseness. The power denseness dictates the size of such systems in high power applications.

Figure aa‚¬ ” Specific energy against specific power for non-nuclear subsea energy transition and storage systems.

In general, intercrossed systems use energy transition devices that have high specific power in order to efficaciously obtain high degree of currents. Energy storage devices that have a great specific energy would enable dependable operation in the event of primary power system failure. The figure above illustrates the typical power and energy densenesss. The fuel cell systems tend to hold a high specific energy compared to the other systems. Whereas, gas turbine has the high specific power compared to the remainder. Soon, there is a undertaking carried out by NASA to construct a lightweight, efficient regenerative fuel cell that is to be used on the Helios aeroplane that can wing in the attitudes closer to 100,000 foot. Therefore, such system could be used for subsea energy demands in the close hereafter. [ Ref: hypertext transfer protocol: //www.fctec.com/fctec_types_rfc.asp ]

Harmonizing to Lawrence Livermore National Laboratory [ ] , the following tabular array shows fuel cells used to change over energy and hive away them. The survey assessed intercrossed systems that are used to power the oil and gas production operation in sub sea degree. FC1, consist of

Table – Hybrid system incorporating fuel cells

Hybrid Systems

Components

FC1

Line for Surface O2

Well Head Gas

Reformer

PEMFC

Lead-Acid and/or Li-Ion Batteries

FC2

Stored O2

Well Head Gas

Reformer

Fuel Cell

Lead-Acid & A ; Li-Ion Batteries

Figure – 2D schematic of a subsea vas.

The above diagram shows a conventional representation of a fuel powered subsea vas. It does exemplify the needed systems that operate the vas, including an O storage armored combat vehicle, H storage cylinders, fuel cells and batteries. The PEMFC used in the above subsea vas, developed by Siemens, uses a solid province ( FeTi ) H storage and liquid O. This give the chances of holding fuel cell power coevals options aboard a deep sea vehicle that can be deployed from ocean surface to the floor of the ocean.

Fuel Cell Components

Briefly, fuel cells undergo an electrochemical reaction that involves a fuel and an oxidizer in a cell. It includes an anode, a cathode, and an electrolyte. The fuel cells are stacked together in groups of cells, either in a series or parallel connexions, depending on the stacking design and the power demand. The electrolyte is sandwiched between the anode and the cathode, which provide a medium for ion exchange and a centrifuge for the anode and cathode compartments. In the anode, the oxidization reaction occurs, which provides a negative charge toward the cathode through the membrane.

In the subsea conditions, the fuel cell constituents consist of a fuel vas and an oxidant vas. One attack is that the fuel vas may incorporate a metal hydride, in order to supply a high-density means for the storage of the fuel. There are legion advantages related to the usage of the metal hydride, over conventional hard-hitting gas storage systems. Therefore, this metal hydride would supply greater storage capableness per unit volume and lower force per unit area metal hydride will turn out a safer type of operation particularly in an environment of high temperature. Whereas, the oxidant vas that can be used in the subsea vehicle consist of air or pure O under immense force per unit area up in the scope of ( 5,000 to 15,000 psig ) .

The following tabular array summarizes the constituent used in a subsea fuel cell.

Components

Description

Use

Manifolds

Pipe used to provide gas to a burner, which an either internal or external in a fuel cell.

Even distribution of fuel and oxidizer to electrode surface

Heat Exchangers

Cool down the fuel cell system. ( i.e. Humidifiers ) .

Maintain the operating temperature.

Reformer

Vessel where recycle watercourses are reacted with heat and H2O vapour.

Producing H gas.

Filters

Device composed of hempen stuff the can take particulates.

Remove unwanted solid stuffs, such as sulfur, diesel filtration ( transit ) , and natural gas ( power coevals ) .

Seals & A ; Gaskets

Prevention of escape in the fuel cell system.

Prevent gases and liquid within the system from get awaying, therefore increasing safety and extra disbursals.