Patent Application
20060141329
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.
A simplified illustration of a fuel cell power plant is shown in
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.
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.
Referring to
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.
