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imagelinks[3]="http://www.empf.org/helpline/helpline.htm" imagelinks[4]="http://www.aciusa.org/ana/ana_home.htm" imagelinks[5]="http://www.empf.org/empfasis/subscribe.htm" var ry=Math.floor(Math.random()*myimages.length) if (ry==0) ry=1 document.write('<a href='+'"'+imagelinks[ry]+'"'+'><img src="'+myimages[ry]+'" border=0></a>') } random_imglink() //--> </script></p> </div></td> </tr> <tr> <td colspan="2"><div align="center"><span class="style5">ACI Technologies Inc.</span><br> One International Plaza<br> Suite 600 <br> Philadelphia, PA 19113 <br> (610) 362-1200 <br> <span class="style6">FAX: </span>(610) 362-1290<br> <span class="style6">HELPLINE: </span>(610) 362-1320<br> <span class="style6">WEBSITE: </span><a href="http://www.empf.org">www.empf.org</a><br> <a href="http://www.aciusa.org">www.aciusa.org</a></div></td> </tr> </table> <p>&nbsp;</p> <p><br> <br> </p> <div align="center"> <p align="center" class="style7">Michael D. Frederickson<br> <strong><em>EMPF Director </em></strong><br> <br> Barry Thaler, PhD.<br> bthaler@aciusa.org <br> <strong><em>Empfasis Technical Editor<br> </em></strong><br> Paul Bratt<br> pbratt@aciusa.org <br> <strong><em>Empfasis Editor</em></strong><br> </p> <p align="center" class="style7"><img src="http://www.empf.org/empfasis/archive/images/iab_sm.gif" alt="IAB" width="100" height="52"><br> <span class="style9">Industrial Advisory Board</span><br> <span class="style14"><em>Gerald R. Aschoff</em>, The Boeing Company<br> <em>Dennis M. Kox</em>, Raytheon<br> <em>Gregory X. Krieger</em>, BAE Systems<br> <em>Edward A. Morris</em>, Lockheed Martin<br> <em>Jane Krueger </em>, Rockwell Collins<br> <em>Gary Kirchner</em>, Honeywell<br> <em>Andrew Paradise</em>, Northrop Grumman<br> <em>Richard Kidwell </em>, ITT Industries</span></p> </div> <p align="center" class="style7"><br> </p> </div> </td> </tr> </table> </div></td> <!-- InstanceBeginEditable name="Body1" --><td width="70%" rowspan="2" valign="top"><div class="body_style" id="body_content"> <p><img src="images/optimizing.gif" alt="title"></p> <p class="body_text"><span class="style20">A</span>t the Naval Energy Forum in October 2009, Secretary of the Navy Ray Mabus committed "the Navy and Marine Corps to meet bold, ambitious goals" focused around key themes tied to energy: security, efficiency, and environmental stewardship.</p> <p>The five energy targets include:</p> <ul> <li>Considering the lifetime energy cost of a system when awarding contracts during the acquisition process. </li> <li>Deploying a "Green Strike Group" fleet of nuclear vessels and ships powered by biofuels by 2016.</li> <li>Phasing in hybrid fuel and electric vehicles in its commercial vehicle fleet to reduce petroleum use by 50 percent. </li> <li>Using renewable sources of energy (such as solar, wind and ocean) to provide 50 percent of the shore-based energy requirements.</li> <li>Ensuring 40 percent of the Navy's total energy consumption comes from alternative sources by 2020.</li> </ul> <p>The Department of the Navy [the second largest fuel user in the Department of Defense (DoD)] uses almost a third of the total DoD petroleum consumption at about 100,000 barrels per day. Seeking quieter and more efficient sources of energy, the Office of Naval Research (ONR) is leading the research efforts for alternative fuels and has been a key supporter of fuel cells for 20 years. Fuel cells have the ability to deliver clean and efficient power for Naval and DoD applications.</p> <p><b>Fuel Cell Design</b></p> <p>While batteries chemically store electrical energy in a closed system, a fuel cell reacts fuel with an oxidizer in the presence of an electrolyte (a substance designed to allow ion flow but prevent electron flow) and electrochemically converts it into electrical current. By maintaining the flow of reactant and oxidizer, fuel cells can continuously output electric current. <p>A hydrogen fuel cell reacts hydrogen with oxygen (usually from air), but many other combinations of fuels and oxidants are possible. Many designs exist for fuel cells but they all consist of an anode, electrolyte, and cathode. Hydrogen is catalyzed at the anode to become a positive ion and a free electron. The electrolyte carries the ion to the anode while the electrons travel through an external wire generating an electric current. At the cathode, the ion and electron are reunited and react with oxygen to form water. <p>One of the more common types of fuel cell is the polymer electrolyte membrane or proton exchange membrane (PEM) fuel cell (Figure 3-1). The electrolyte membrane in the PEM fuel cell is like a moist, thin piece of plastic wrap that allows charged ions (protons) to pass through. A typical PEM fuel cell produces approximately 0.6V and can be combined in parallel and series circuits (a fuel cell stack) to provide higher currents and higher voltages, respectively. Increasing the surface area of the cell can also produce higher currents from each cell. <p align="center"><img src="images/fig3-1.gif"></p> <p><b>Fuel Cell Controller</b></p> <p>As the current increases the voltage decreases due to activation loss, ohmic loss (resistance of the cell components and interconnects), and depletion of reactants at catalyst sites. So it is necessary to control the system to operate in conditions which match up with the fuel cell maximum power point (MPP). In order to operate efficiently, electronics must be designed to carefully control several factors. </p> <ul> <li>Use the fuel cell at maximum efficiency by drawing current at a constant value.</li> <li>Determine the fuel cell MPP in "real-time."</li> <li>Control the flow of water, oxygen, and hydrogen into and out of the fuel cell.</li> <li>Control the charging and discharging of the auxiliary battery by monitoring the output voltage.</li> <li>Provide the power level as required by the load.</li> <li>Maintain the cell temperature.</li> </ul> <p align="center"><img src="images/fig3-2.gif"></p> <p>A three stage converter can be used to provide this control (Figure 3-3).</p> <p align="center"><img src="images/fig3-3.gif"></p> <p>The main component (first DC/DC converter stage) regulates the current drawn from the fuel cell regardless of the load (which leads to a fluctuating voltage on the DC bus). This stage is based on a boost converter switching-mode power supply (SMPS) containing two semiconductor switches (a diode and a transistor) and two energy storage elements (a bobbin and the output condenser) and provides a higher output voltage to the DC bus than the fuel cell input (Figure 3-4).</p> <p align="center"><img src="images/fig3-4.gif"></p> <p>The bi-directional DC/DC converter (Figure 3-3) is used to keep the DC bus voltage within defined limits. When the bus voltage goes high the excess is directed to charge an auxiliary battery. When the bus voltage goes low the battery provides additional energy to maintain the DC bus voltage within limits. The inverter then converts the DC energy to whatever waveform the load requires.</p> <p><b>Ion Tiger - Unmanned Aerial Vehicle (UAV)</b></p> <p>Significantly improved battlefield surveillance capabilities can be obtained by incorporating the hydrogen fuel cell into the Navy's unmanned aerial vehicle program. The Naval Research Laboratory (ONR's corporate laboratory) has demonstrated a reduced noise and heat signature during test flights of their Ion Tiger UAV (Figure 3-5). The relatively small 550-watt fuel cells provide a greater range than earlier battery designs, give off no emissions, and allow the smaller UAV to lift heavier payloads.</p> <p align="center"><img src="images/fig3-5.gif"></p> <p>Fuel cell power generation systems have the potential to provide the electrical power needs of future naval systems, as well as Marine Corps land-based and man portable system. Substantially reduced life cycle costs are expected as a result of greater system efficiencies, lower maintenance costs, and lower emissions when compared with other power generation systems.</p> <p>References:</p> <ul type=1> <li>"FCT Fuel Cells: Basics." <i>The Office of Energy Efficiency and Renewable Energy</i>. U.S. Department of Energy. Web. 23 June 2010. <a href="http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/basics.html">http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/basics.html</a>.</li> <li>DONCA, Radu, Radu BALAN, Vistrian MATIES, and Olimpiu HANCU. "Control Method for the Improvement of the Efficiency of a Fuel Cell." Technical University of Cluj-Napoca, Romania. Web. <www.icrepq.com/icrepq-08/373-Donca.pdf>.</li> <li>"ONR Fact Sheet: Ion Tiger - Office of Naval Research." Office of Naval Research. Web. 23 June 2010. <a href="http://www.onr.navy.mil/en/Media-Center/Fact-Sheets/Ion-Tiger.aspx">http://www.onr.navy.mil/en/Media-Center/Fact-Sheets/Ion-Tiger.aspx</a>.</li> </ul> <p class="body_text"><img src="../../archive/updated/pbratt.gif"></p> </div> </td> <!-- InstanceEndEditable --> </tr> <tr> </tr> </table> <br> <table width="100%" border="0"> <tr> <td colspan="2"><div align="center"> <p><em>The EMPF is a U.S. Navy-sponsored National Electronics Manufacturing Center of Excellence focused on the development,<br> application, and transfer of new electronics manufacturing technology by partnering with industry,<br> academia, and government centers and laboratories in the U.S</em></p> </div></td> </tr> <tr> <td class="footer">ACI Technologies, Inc. - - <a href="http://www.aciusa.org">www.aciusa.org</a> - - (610)362-1200</td> <td><div align="right"><a href="http://www.navymantech.com"><img src="http://www.empf.org/empfasis/archive/images/mantech.gif" width="144" height="42" border="0"></a></div></td> </tr> </table> <div align="right"> <!-- Start of StatCounter Code --> <script type="text/javascript" language="javascript"> var sc_project=350643; var sc_partition=1; </script> <script type="text/javascript" language="javascript" src="http://www.statcounter.com/counter/counter.js"></script> <noscript> <a href="http://www.statcounter.com/free_hit_counter.html" target="_blank"><img src="http://c2.statcounter.com/counter.php?sc_project=350643&amp;amp;java=0" alt="hit counter" border="0"></a> </noscript> <a href="http://www.empf.org/sitemap.htm"><em>[site map] </em></a> <!-- End of StatCounter Code --> <!-- Start of StatCounter Code --> <script type="text/javascript" language="javascript"> var sc_project=1902214; var sc_invisible=1; var sc_partition=17; var sc_security="759b802c"; </script> <script type="text/javascript" language="javascript" src="http://www.statcounter.com/counter/counter.js"></script><noscript><a href="http://www.statcounter.com/" target="_blank"><img src="http://c18.statcounter.com/counter.php?sc_project=1902214&java=0&security=759b802c&invisible=1" alt="website statistics" border="0"></a> </noscript> <!-- End of StatCounter Code --> </div> </body> <!-- InstanceEnd --></html>