Fuel cells having water passageways, with water permeable wick layers between them, provide water to reactant gas flow passageways wherein the water is evaporated in proportion to the waste heat generated in the cells; the water condensed from the exhausted reactant gas is returned to the water passageways. Optionally, the passageways may be in the form of an interdigitated flow field, to increase removal of water from the wick during water purging, at shutdown.
It is known in the proton exchange membrane fuel cell art to evaporatively cool fuel cells, thereby deriving the benefit of the heat of vaporization, in contrast with conveying sensible heat to circulating water passing through the cells or coolant passing through coolant plates. One example is shown in U.S. Pat. No. 7,504,170, which is incorporated herein by reference.
In some applications, such as in vehicles, extremely high current densities are preferred in order to support high vehicle performance. High current densities increase water production, which requires assured flow through porous, hydrophilic reactant gas flow field plates, hereafter also referred to as “water transport plates”. Furthermore, increased power density requires assured cooling and humidification of the membrane.
For high performance, the very best communication of water between water passageways and the water transport plates is beneficial.
According to the subject matter hereof, fuel cells in a fuel cell power plant are evaporatively cooled by means of water present in passageways which are adjacent to or within a first surface of at least one of the hydrophilic, porous reactant gas flow field plates, which have reactant gas flow channels opening at a second surface of the flow field plates, opposite to said first surface. Each passageway is in fluid communication with a water reservoir. In addition, the water uptake by the flow field plates is increased by a water permeable wick layer between the flow field plates, and in intimate contact with all of the water passageways. The water supply in the passageways is enhanced by means of the water permeable wick layer adjacent to water in one or more of the passageways.
It has been found that a fuel cell power plant in a climate which may fall below the freezing temperature of water requires removal of at least most of the water from the fuel cell stack during shutdown. This reduces the propensity to have potentially catastrophic mechanical stresses during the period of non-use of the fuel cell, and blockage (by ice) of reactant gas at startup. The reduction of water in a fuel cell stack employing a water permeable wick by blowing air through the water passageways has been found to provide an inadequate removal of water from the water permeable wicks.
The subject matter herein further includes utilization of interdigitated coolant water flow fields which ensure that the purging air will transfer into and flow through the water permeable wick, thereby forcing more water therefrom. In one embodiment, normal conventional interdigitated flow fields are used. In another embodiment, interdigitated flow fields having less than a complete blockage at the outlet ends of the inlet flow fields assures the ability of gas (typically leaking into water passageways from the reactant flow fields) to escape the flow fields, thereby avoiding blockage of water flow and dry out of the membrane.
Other variations will become more apparent in the light of the following detailed description of exemplary embodiments, as illustrated in the accompanying drawings.
Referring now to
In this embodiment, fuel is provided to a fuel inlet 42 and flows to the right in a first fuel pass, and then flows downwardly and to the left through a fuel outlet 47. The fuel may flow through a recycle pump (not shown) back to the fuel inlet, and may be periodically purged to ambient through a valve (not shown). Single pass, triple pass or other fuel flow configurations may be used.
In the embodiment of
Although there is a water inlet 66, there is no water outlet, the water is simply present in each fuel cell. In
In the embodiment of
In accordance with a first aspect of the subject matter herein, the fuel cells 38 of
The water permeable wicks 90 may comprise a suitable, readily available carbon paper, such as Toray H-060 which has been suitably treated, such as with tin, or a tin-containing compound or mixture, to render it sufficiently hydrophilic so to assure the desired permeability to water.
With the water permeable wick 90 adjacent to the lands or ribs 92 of the water transport plates 75, 81, the lands 92 provide additional surface area of the water transport plates which assist in transferring water. In contrast, in the aforesaid patent, water transfers between the water passageways and the water transport plates only through the surfaces of the water passageways.
In the embodiment of
Referring to
To improve the clearance of water from the fuel cell stack, and particularly from the water permeable wicks 90, the passageways may be formed in an interdigitated fashion, as illustrated in
Another embodiment of the invention similar to
Instead of a blockage 104, the outlet end 101 of the inlet water passageways 83d may simply have a small hole 106 therein, as illustrated in
Since changes and variations of the disclosed embodiments may be made without departing from the concept's intent, it is not intended to limit the disclosure other than as required by the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2010/002691 | 10/6/2010 | WO | 00 | 4/1/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/047184 | 4/12/2012 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
6472095 | Margiott | Oct 2002 | B2 |
7504170 | Reiser et al. | Mar 2009 | B2 |
20010041281 | Wilkinson et al. | Nov 2001 | A1 |
20020106546 | Perry et al. | Aug 2002 | A1 |
20030039877 | Dufner et al. | Feb 2003 | A1 |
20030129468 | Issacci et al. | Jul 2003 | A1 |
20040067405 | Turpin et al. | Apr 2004 | A1 |
20050106434 | Shimotori et al. | May 2005 | A1 |
20060141331 | Reiser et al. | Jun 2006 | A1 |
20070154744 | Darling et al. | Jul 2007 | A1 |
20080038610 | Darling | Feb 2008 | A1 |
20100015483 | Yang | Jan 2010 | A1 |
20100119911 | Reiser et al. | May 2010 | A1 |
Number | Date | Country |
---|---|---|
101107743 | Jan 2008 | CN |
2007086828 | Aug 2007 | WO |
2008105751 | Sep 2008 | WO |
2009128832 | Oct 2009 | WO |
2009131581 | Oct 2009 | WO |
Entry |
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Interdigitate. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/interdigitate (accessed: Jul. 21, 2015). |
Intersperse. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/intersperse (accessed: Oct. 8, 2015). |
Mingle. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/mingle (accessed: Oct. 8, 2015). |
Intermingle. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/intermingle (accessed: Oct. 8, 2015). |
Interweave. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/interweave (accessed: Oct. 8, 2015). |
Interlock. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/interlock (accessed: Oct. 8, 2015). |
Interlace. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/interlace (accessed: Oct. 9, 2015). |
International Search Report, mailed Jul. 18, 2011, for International Application No. PCT/US2010/002691, 2 pages. |
Number | Date | Country | |
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20130224622 A1 | Aug 2013 | US |