Fuel cell demineralizers integrated with coolant accumulator

Abstract

The water transport plates (8) of a stack of fuel cells (9) receive water from an accumulator (11) which has a vent (17) within which demineralizers (33) are disposed. The entrance to the accumulator has a conical baffle which disrupts the flow of water entering the accumulator, thereby acting as a gas separator (16). A coolant pump (23) pumps coolant through a heat exchanger (25) where it is divided between an accumulator inlet conduit (31) and a demineralizer inlet conduit (32), the flow between which may be adjusted by means of a flow restrictor (30).

Description

TECHNICAL FIELD

This invention relates to disposing fuel cell power plant water demineralizers within the coolant accumulator so as to be warmed by the fuel cell stack coolant, upon startup, particularly in sub-freezing temperatures.

BACKGROUND ART

A simplified illustration of a fuel cell power plant is shown in FIG. 1.

The cooler plates 8 within the fuel cell stack assembly 9 (CSA) receive water over a conduit 10 from an accumulator 11. The outflow from the cooler plates 8 is applied over a conduit 15 to a separator 16 having a vent, such as an atmospheric vent 17, that removes entrained gas from the coolant water. A conduit 22 provides the coolant to the input of a coolant pump 23, the outflow of which on a conduit 24 delivers the coolant to a heat exchanger 25. When a fuel cell power plant is operating, the heat exchanger will dissipate some of the heat to maintain the coolant water temperature reentering the cooler plates 8 at a suitable temperature. The heat exchanger may typically include a fan utilizing atmospheric air as the cooling medium, and may have a thermostatically controlled bypass, all as is conventional, well known in the art and not disclosed further herein for clarity.

The coolant then passes through conduits 29, 31 to the accumulator 11. A flow restrictor 30 allows balancing the flow of water between the accumulator and a demineralizer 33. In some configurations, the flow restrictor may be in the conduit 32. The demineralizers 33 contain a large mass of conventional deionizing resin so as to remove minerals from the coolant.

At temperatures below the freezing temperature of water, even though a bulk of the water system is thawed and water is flowing and becoming warmed by process heat within the CSA 9, the large thermal mass of the deionizing resin in the demineralizer, coupled with the very low flow of water through the demineralizer, cause the water flowing into the demineralizer to flash freeze, and block any further flow. Thus, the demineralizer takes an extremely long time to thaw, perhaps hours.

In order to accommodate the large, cold, mass of the demineralizer 33, it is common to provide a heater 36 on the external surface of the demineralizer, or in some other way to heat the mass of deionizing resin therein.

The heat required to raise the mass of the demineralizer to a temperature above the freezing point of water is significant, and constitutes an excessive parasitic power drain. In vehicular applications, where an electric motor is driven by a fuel cell power plant, space is at a premium and parasitic power must be kept to a minimum since the storage of fuel must be minimized. The total water volume in a vehicular system should be minimized as well.

During startup, before adequate flow is established in the demineralizers, the water becomes more and more conductive thereby reducing useful power that is generated.

Fuel cell power plants with separate deionizers are disclosed in U.S. Pat. Nos. 6,368,737, 6,428,916 and 6,656,622.

DISCLOSURE OF INVENTION

Objects of the invention include: reducing the size of fuel cell power plants; reducing parasitic power in fuel cell power plants; reducing the plumbing necessary for the water volume and temperature management system in fuel cell power plants; reducing the plumbing required in fuel cell power plant water systems; simplifying shut down strategies for draining water systems in fuel cell power plants used in subfreezing ambients; and reducing the volume required by a fuel cell power plant.

According further to the invention, a gas separator in the water flow of a fuel cell power plant water volume and temperature management system comprises a baffle disposed in the top of a vented accumulator, thereby reducing the overall volume of the power plant.

According to the present invention, one or more demineralizers of a fuel cell power plant are disposed within the water accumulator of the fuel cell power plant.

The invention utilizes heat generated by the fuel cell power plant upon startup to warm the demineralizers, by heat transfer between the coolant in the water accumulator and the demineralizers contained therein. With the invention, because the space surrounding the one or more demineralizers is used to accommodate accumulator water, rather than simply occupy cabinet space, the invention saves overall volume required for fuel cell power plants.

An advantage of the invention is that sloshing of water within the accumulator is reduced due to the baffle effect of the one or more demineralizers contained therein.

Other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of exemplary embodiments thereof, as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, stylized block diagram of a fuel cell power plant with a separate demineralizer as is known in the prior art.

FIG. 2 is a simplified, stylized schematic block diagram of a fuel cell power plant having demineralizers disposed within the water accumulator, in accordance with the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

Referring to FIG. 2, one or more demineralizers 33 are disposed directly within the accumulator 11. At the top of the accumulator, the separator 16 comprises a conical baffle, around which water flows downwardly into the accumulator, allowing gases to escape through the vent 17. It could be other shapes or a spray, in some embodiments. In the form illustrated in FIG. 2, the invention not only reduces the volume of fuel cell power plants by disposing the demineralizers within the accumulator, it also reduces volume by disposing the separator within the accumulator.

In a preferred embodiment, the flow restrictor 30 and much of the plumbing 29, 31, 32 will be disposed within the accumulator 11.

All of the aforementioned patents are incorporated herein by reference.

Thus, although the invention has been shown and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the invention.

Claims

1. A fuel cell power plant comprising:

a stack of fuel cells, each fuel cell having anode water flow channels and cathode water flow channels;

a water accumulator in fluid communication with at least some of said water flow channels and having an inlet feed conduit;

at least one demineralizer disposed within said water accumulator and having an inlet feed conduit;

and wherein said accumulator is vented and has a conical baffle disposed at an inlet of the accumulator so as to disrupt the flow of water and gas entering the accumulator, whereby gas is separated from water; and

said accumulator inlet feed conduit and said demineralizer inlet feed conduit receive water from at least some of said water flow channels.

2. A fuel cell power plant according to claim 1 further comprising a heat exchanger disposed between said water flow channels and said accumulator inlet conduit.

3. A fuel cell power plant comprising:

a stack of fuel cells, each fuel cell having anode water flow channels and cathode water flow channels;

a water accumulator in fluid communication with at least some of said water flow channels and having an inlet feed conduit; and

at least one demineralizer disposed within said water accumulator and having an inlet feed conduit; and

said accumulator inlet feed conduit and said demineralizer inlet feed conduit receive flow of water from at least some of said water flow channels.

4. A fuel cell power plant according to claim 3 wherein the flow of water into said accumulator and into said at least one demineralizer is adjusted by means of a flow restrictor in one of said inlet feed conduits.

5. A fuel cell power plant according to claim 3 further comprising a heat exchanger disposed between said water flow channels and said accumulator inlet conduit.

6. A fuel cell power plant comprising:

a stack of fuel cells, each fuel cell having anode water flow channels and cathode water flow channels;

a water accumulator, said accumulator being vented and having a conical baffle disposed at an inlet of the accumulator so as to disrupt the flow of water and gas entering the accumulator, whereby gas is separated from water; and

said accumulator inlet flow conduit receiving water from at least some of said water channels.

7. A fuel cell power plant according to claim 6 further comprising a heat exchanger disposed between said water flow channels and said accumulator inlet conduit.