Tuesday, October 26, 2010

Fuel Cells for Marine Propulsion

By Louis Lemos

Various scientific theories and subsequent discoveries have been identified as stepping stones in the evolution of what has become known as the fuel cell, which generates electricity through heat. The concept of “thermoelectric generation” discovered by Seebeck around 1821, is based on the principle that current is produced in a closed circuit of two dissimilar metals, if the two junctions are maintained at different temperatures, such as in thermocouples for measuring temperature. Potentials are produced by thermocouples, and power at efficiencies of approximately 1 percent. The Peltier effect, discovered in 1834, consists of the heating or cooling of the junction of two thermoelectric materials by passing a current through the junction. The effectiveness of thermojunction as a cooling device has been greatly increased by the application of semiconductor thermoelectric materials.

In 1915 the concept of “Thermionic Generation” was proposed by Schlicter, using a thermionic converter, which is basically a vacuum or gas-filled device with a hot electron emitter as the cathode, and a cold electron collector as the anode within a gas-tight enclosure. By heating the cathode, it imparts enough energy to some of the electrons to enable them to escape from the work-function barrier at the surface of the cathode, into the interelectrode space. Gas-filled converters can attain efficiencies as high as 17 percent but with an output voltage averaging 1 to 2 volts, several units are required to be connected in series to attain a reasonably useful voltage.

Fuel Cell Fuels
Of the various fuels available for use in fuel cell systems, hydrogen appears to be the most logical, given that (a), it is non-toxic, (b), yields a higher ratio of chemical energy per unit mass than that available from natural gas, and (c), it is abundant as an unlimited resource in atomic form. In addition to which, hydrogen is non-polluting. Liquefied Natural Gas (LNG), which is now widely used in many dual-fuel marine diesel engines, is also a strong contender for fuel cell use.

Currently, there is an ongoing initiative in Holland known as the Green Tug project, piloted by the Offshore Ship Designer Group, including participation by Bureau Veritas, featuring a hydrogen-powered fuel cell tugboat designed for near-zero exhaust emissions level, and estimated to increase propulsion efficiency by almost seventy percent compared to that of a conventional Diesel-direct-drive.

There is also a methanol-based auxiliary power system fuel cell known as METHAPU, sponsored by the European Union with the cooperation of Lloyd’s Register, Wartsila and the University of Genoa, among others. This project involves a methanol-fuelled auxiliary power system of the solid oxide fuel cell (SOFC) type, rated at 20kW, that has recently been installed aboard a Swedish car carrier. In addition thereto is the MTU Onsite Energy fuel cell developed by the Fellow-SHIP Project, consisting of Det Norske Veritas, the ship-owner Eidesvik, the system integrator Wartsila and MTU Onsite Energy, who supplied the 320 kW fuel cell powered by LNG that was installed aboard the Norwegian Offshore-Support ship Viking Lady in the latter part of 2009. Funding for the Fellow-SHIP project is provided by the Norwegian Research Council and Innovation Norway.

The essential factors governing the selection of the most appropriate fuel for use in fuel cells are those of availability and cost. Hydrogen, for instance, can be obtained from natural gas and coal, involving a process of carbon sequestration. Given that the submerged endurance of ninety days by nuclear submarines is attributable to the ability of replenishing their internal atmosphere with fresh oxygen extracted from seawater, it is conceivable that this capability may eventually be extended to surface ships powered by Marine Propulsion fuel cells. In this case, the procedure would be changed to the extraction of hydrogen from seawater, (using a form of hydrolysis), to feed the Marine Propulsion fuel cell engines. Given the inevitable trend toward Hydrogen as a preferred fuel for fuel cells, those interested in the development of fuel cell systems for Marine Prime Movers, are advised to learn all they can about the safe handling, transportation and storage of hydrogen, since this will no doubt become a primary choice of fuel for Marine fuel cell systems. A logical starting point for such information is to be found within the growing application of dual-fuel engines, and associated support systems for main propulsion of recently built European-flagged LNG carriers. Much of the current dual-fuel program consists of high-grade conventional marine diesel fuel (MDO) and Liquefied Natural Gas (LNG), of which the latter already involves practice and procedures that are applicable to hydrogen. In due course, we may expect to see publication and indeed enforcement, of a safety code of hydrogen storage and handling. Hence, it would be wise to monitor the pertinent publications from the American Bureau of Shipping (ABS) and their foreign counterparts; the US Coast Guard; International Maritime Organization (IMO), and major Marine Fuel Refiners, for the benefit of those ultimately responsible for distribution and ultimately, consumption of such fuel.

Basic Technology
When provided with fuel and air, a fuel cell converts chemical energy directly into electricity and heat, but unlike batteries, will not run down. It is an electrochemical device that converts the chemical energy of the fuel directly into electricity and heat, and does so more efficiently than conventional combustion-based technologies. The common types of fuel cells are phosphoric acid (PAFC); molten carbonate (MCFC); proton exchange membrane (PEM); and solid oxide (SOFC); all named after their respective electrolytes. Given that they rely on electrochemical reactions instead of combustion, fuel cells need an easily oxidized substance, such as hydrogen. Some fuel cells, such as solid oxide fuel cells (SOFC), can also utilize carbon monoxide (CO), making them more fuel-flexible and generally more efficient with available fuels. Hydrogen and CO can be produced from natural gas and other fuels by steam reforming. fuel cells like SOFC’s that can reform natural gas internally have significant advantages in efficiency and simplicity when using natural gas because they do not need an external reformer.

Safety Codes and Standards
As fuel cells become successfully adopted by the US maritime Industry, for purposes of main propulsion and auxiliary power generation, we should expect to see the promulgation and enforcement of US Coast Guard Rules and Regulations applicable thereto, as well as comparable Rules and Standards issued by the American Bureau of Shipping, for fuel cell-powered American flag vessels. In addition to the aforementioned Guidelines for fuel cell systems on board commercial ships, proposed by Bureau Veritas, there are various codes and standards (non-marine) that may be applicable to basic fuel cells with particular emphasis on the safe handling, transportation, storage and usage of hydrogen and related fuels. The US Department of Energy is currently developing and testing complete system solutions that address all elements of infrastructure and vehicle technology, validating integrated hydrogen and fuel cell technologies transportation, infrastructure and electric generation in a systems context under real-world operating conditions. Data will be collected under realistic operating conditions to provide feedback on progress and to efficiently manage the research elements of the program while providing re-direction as needed.

Comparative Properties of Gasoline, Natural Gas and Hydrogen

Gasoline Natural Gas Hydrogen
Heating Value (low)
(Btu/lb) 18,500 21,250 51,500
Density (lbs./gal.) 6.25 0.005 0.0007
Toxicity to humans Poisonous Non-toxic Non-toxic

The above factors are based on data provided by the Alternative Fuels Data Center, of the U.S. Department of Energy.

Fuel Cell Guidelines
Bureau Veritas (BV), one of the world’s largest Classification Societies, has proposed guidelines for the safe operation of fuel cells for marine propulsion, according to BV Product Manger Gijsbert de Jong. The intent being to establish a regulatory framework within which, building and testing of prototype fuel cell systems can be safely conducted while ensuring that the technology is developed and applied in accordance with safe performance-criteria. In his comments Mr. de Jong stated that “BV’s guidelines for the safe application of fuel cells on ships take into account all relevant existing IMO conventions and guidelines together with a wide range of international non-marine standards. They reflect BV’s in-house knowledge and expertise, and could have important commercial – as well as environmental – implications for ship-owners and operators.” He further explained “The object of the BV guidelines is to provide criteria for the arrangement and installation of machinery for propulsion and auxiliary purposes, using fuel cell installations, which have an equivalent level of integrity in terms of safety, reliability and dependability as that which can be achieved with new and comparable conventional oil-fuelled main and auxiliary machinery. The guidelines currently have preliminary status and are subject to internal and external review. After taking into account all relevant feed-back, they will be published as a Bureau Veritas Guidance Note entitled “Guidelines for fuel cell systems on board commercial ships.”

Fuel Cell Operation
Basic requirements for a hydrogen fuel cell are fuel, oxidant and an electrolyte, plus a negative anode and a positive anode. In a typical Polymer Electrolyte Membrane fuel cell (PEMFC), such as that developed for Space Missions of the 1960’s, the system works as follows:

• Hydrogen is fed into the anode, which is the electrically negative post of the Fuel Cell.
• In the center of the fuel cell the electrolyte absorbs an electron from the hydrogen atom using it to make electricity.
• The cathode, as the electrically positive post of the fuel cell, is where the electrons recombine with the hydrogen and oxygen to make water, which is the exhaust effluent. This transition of protons and electrons is referred to as ionic conduction wherein there is a transmission of electrons (electrically-charged atoms) or protons, produced by dissolution of electrolytes, a characteristic of fuel cells.

Fuel Cell Transplant
Given the eventual phase-out of fossil fuels and the conventional marine propulsion plants (of existing vessels) the latter could be replaced by fuel cell power plants with electric drive motors. Feasibility of such transplant would of course be contingent upon successful reduction of current fuel cell systems to a size compatible with that of existing internal combustion engines, but of comparable power range. The original diesel fuel tanks would have to be replaced with specifically designed high-pressure vessels for storage of hydrogen, with matching high-pressure piping, valves, gauges, etc. This would be somewhat similar to the new high-pressure LNG tanks and piping systems now in use. Meanwhile, the entire existing diesel fuel refinery, distribution, transportation, storage and retail infra-structure as we know it, will have to be re-designed to cope with hydrogen and/or LNG instead. Studies along these lines are currently in progress, coordinated by the California fuel cell Partnership consisting of British Petroleum; Chevron-Texaco; Exxon-Mobil; Shell; California Air Resources Board and the US Department of Energy (D.O.E.). Fuel cell propulsion is being viewed within D.O.E. as the transportation technology of the future, based on the findings of studies being conducted by the Argonne National Laboratory.

Fuel Cell Information
Within the US Department of Energy, under the heading of “Energy Efficiency & Renewable Energy,” there is a fuel cell technologies program to which one may apply for specific data regarding information resources, technologies, financial opportunities and market transformation, etc. Further information may be found within the “California Fuel Cell Partnership” that combines the resources of the California Air Resources Board, the US Department of Energy and that of prominent oil companies.

In addition to several years’ service as engineering officer, British Merchant Navy and as Chief Engineer, US Merchant Marine, Louis Lemos is a US Navy certified Ship Superintendent (MINS); former Marine Engineering Advisor to the South Vietnamese Navy; a licensed Stationary Engineer; Commissioned Inspector of Boilers and Pressure Vessels; former Port Engineer with Military Sealift Command. Mr. Lemos can be reached at 415-897-9056 or l.lemos@att.net.