Portable power

Portable applications of fuel cells include auxiliary power unit and emergency power systems, power tools, laptop computers, and other mobile devices including cell phones. Demands are also growing with the increased energy and power requirements for broadband mobile computing (Dyer, 2002). Power requirements may vary from a few watts ( 1 W) to a few hundred watts or kilowatts (1-5 kW). Portable fuel cells are often categorized on the basis of power requirements (DOE 2010— Record 11009) such as applications less than 2 W, applications for 10-50 W, and applications for 100-250 W. 

Some of the user-specific requirements for portable applications are as follows quick tum-on and -off capability, responsive to dynamic variation in power needs of the device, compact, lightweight, and suitable for operation over a wide range of ambient temperature and humidity conditions. Additionally, portable fuel cells are expected to operate safely, providing power without exposing users to hazardous or unpleasant emissions, high temperature, and low noise. 

Both DMFC and PEMFC are considered for portable applications. 

Aelterman, P. Microbial fuel cells for the treatment of waste streams with energy recovery. PhD Thesis, Gent University, Belgium, 2009. 

R Bennetto. Microbial fuel cells Electricity production from carbohydrates. Applied Biochemistry and Biotechnology 39-40 27-40,1993. 

Most portable electronic devices would require a fuel cell of less than 100 W output, and often considerably less. Here, effort is concentrated on perfecting the DMFC, because of the convenience of methanol as a liquid fuel. Clearly, portable power is a very promising high-value opportunity for small fuel cells, but the outcome would have little impact on overall energy consumption and is not strictly part of the hydrogen energy scene. Nevertheless, many observers believe that volume production of micro fuel cells would be a key technical and economic driver for the entire fuel-cell market. 

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Because of the low operating temperature and ease of fabrication for low power units, PFFCs are the most likely fuel cell to be introduced in portable power packs. PFFCs in sizes of 300—500 W are being considered as a power source, eg, 4-h duration, 300 W, 1.2 kW, for the modem soldier operating in the enclosed environment of a self-contained protective suit, which has faciUties for air conditioning, radio communication, etc. Analytic Power Corp. (Boston) is assessing the use of PFFCs for this appHcation. 

Esters generally tend to be readily biodegradable. This is advantageous for two-cycle engine oils which are discharged to the surroundings from power-driven recreational boats and various portable power units around the home. 

FIGURE 10.13 Basic mechanism of dielectric elastomer actuator (DEA) generator. (From Kombluh, R., Power from plastic How electroactive polymer artificial muscles will improve portable power generator in tbe 21st century military, Presented at TRI-Service Power Expo, Norfolk, Virginia, July 2003. With permission.)... 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

PEMFC Ho.CHjOH 25-100 C 0.1-200 40-50 500-1000 10,000-100,000 50-2000 Transportation, standby power, portable power, space station... 

DMFC CH30H 25-150°C 0.1-10 30-45 50-200 1,000-10,000 1000 Portable power, standby power, transportation ( )... 

Table 4 and Fig. 18 illustrate the performance levels achieved by the active players in DMFC R D. The main goal in DMFC research in the U.S. and European programs is to achieve a stable performance level of 200 mW/cm at a cell potential of 0.5 to 0.6 V. It is because of the relatively low activity of the electrocatalyst for methanol electrooxidation that this power level is less than half that of a PEMFC with Hj as a fuel. A higher power level of the DMFC is essential for a transportation application, but the present power level goal is quite adequate for small portable power sources. 

The DMFC is the most attractive type of fuel cell as a powerplant for electric vehicles and as a portable power source, because methanol is a liquid fuel with values for the specific energy and energy density being about equal to half those for liquid hydrocarbon fuels (gasoline and diesel fuel). 

Our crystal-ball predictions are that DMFCs will first be commercialized as portable power sources for military and civilian applications before the year 2010 and that there will then be a quantum jump in the technology to be in a position to drive DMFC-powered electric vehicles 10 years thereafter. 

The second example describes distributed, mobile and portable power-generation systems for proton-exchange membrane (PEM) fuel cells [106]. A main application is fuel processing units for fuel cell-powered automobiles it is hoped that such processing units may be achieved with a volume of less than 8 1. 

Rozmiarek, R. T., LaMont, M.J., Tonkovich, A. L. Y, MicroChannel fuel processing for man portable power, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 364-359 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Cameras, rechargeable appliances such as portable power tools, hand-held vacuums, etc. 

Possible Submarines, Portable Power stations Power Vehicles, Power... 

The modular design of the HyPM fuel cells allows scaling for higher power requirements using a variety of configurations, such as series and parallel systems. Potential applications for the technology include vehicle propulsion, auxiliary power units (APU), stationary applications including backup and standby power units, combined heat and power units and portable power applications for the construction industry and the military. 

Portable power and stationary or transport systems are validated infrastructure investment begins with governmental policies. 

The overarching drivers for the development of hydrogen technologies are climate change and reductions in oil consumption with additional benefits in emissions reductions. The use of hydrogen in fuel cell vehicles can reduce oil use and carbon plus other emissions in the transportation sector, while hydrogen can enable clean, reliable energy for stationary and portable power applications. 

Dahm, W. J. A., Ni, J., Mijit, K., Mayor, R., Qiao, G., Benjamin, A., Gu, Y., Lei, Y., and Papke, M., Micro internal combustion swing engine (MICSE) for portable power generation systems. In the 40th AIAA Aerospace Sciences Meeting and Exhibit, Reno, 2002. 

Therefore, methanol is the top candidate because of its low price, less toxicity, high energy density and easy handling. Although direct methanol fuel cells may need an auxiliary system to treat unoxidized or partially oxidized fuel in the exhaust gas, direct methanol fuel cells are still a very attractive system as a portable power source. 

Because of the modular nature of fuel cells, they are attractive for use in small portable units, ranging in size from 5 W or smaller to 100 W power levels. Examples of uses include the Ballard fuel cell, demonstrating 20 hour operation of a portable power unit (32), and an IFC military backpack. There has also been technology transfer from fuel cell system components. The best example is a joint IFC and Praxair, Inc., venture to develop a unit that converts natural gas to 99.999% pure hydrogen based on using fuel cell reformer technology and pressure swing adsorption process. 

One further degradation mode related to catalysis is a consequence of operating at low current densities typical of portable power application. Under these conditions, overoxidation of the Pt cathode catalyst occurs, reducing cathode and overall MEA performance. Zelenay has shown that starving the cathode of air flow lowers the cathode potential to low values, causing reduction of Pt oxides and restoring cathode activity. ... 

Fuel cells are electrochemical devices that convert the chemical energy of the fuels directly into electrical energy, and are considered to be the key technology for power generation in stationary, automotive, portable and even microscale systems. Among all kinds of fuel cells, direct methanol fuel cells have really exhibited the potential to replace current portable power sources and micropower sources in the market (Yao et al., 2006). 

A fuel cell that has desirable features for transportation and portable power is the polymer electrolyte membrane (PEM) system. The core of this technology is a polymer membrane that conducts... 

Finally, in order for PEM fuel cell systems to be affordable for portable power applications, a source... 

One of the lessons learned in the 1990s was that the enormous need for high-performance portable power is not diminishing. Consumer electronics continues to be a vibrant, worldwide market force, leading to ever-increasing demands for portable power. The inability of lithium ion batteries to fully satisfy consumer electronics has been one of the principal motivations for the dramatic rise in fuelcell research and development. As the dimensions of devices continue to shrink, the question arises as to... 

Three-dimensional batteries offer a different approach to the portable power field. In this paper we have presented 3-D designs that emphasize power sources with small areal footprints but do not compromise power and energy density. While this approach may not help solve the power needs for cell phones and laptop computers, it will have a significant impact on current and future generations of microdevices. In particular, distributed sensor networks and wireless communication systems are representative areas where 3-D batteries would be welcomed enthusiastically because the power supplies currently in use are many times the size of the device. 

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