Fuel cell system with a single coolant loop

Embodiments of the present invention provide a single coolant loop (40) that can be used for cooling at least two systems (100, 26) that are generally operable at two different temperatures. Rather than providing two separate cooling loops that can provide the two different cooling temperatures, there is provided a single cooling loop (40) that can route, harness, and mix heated coolant so that the two system can be served by a single loop.

FIELD OF THE DISCLOSURE

Embodiments of the present disclosure relate generally to a system that provides a single cooling loop for cooling at least two systems. In a particular embodiment, the systems to be cooled may be a fuel cell system and one or more of its related electronic components. The cooling loop may be used on-board a vehicle, such as an aircraft.

BACKGROUND

Vast numbers of people travel every day via aircraft, trains, buses, and other vehicles. Such vehicles are often provided with components that are important for passenger comfort and satisfaction. For example, passenger aircraft (both commercial and private aircraft) can have catering equipment, heating/cooling systems, lavatories, water heaters, power seats, passenger entertainment units, lighting systems, and other components. A number of these components on-board an aircraft require electrical power for their activation. Although many of these components are separate from the electrical components that are actually required to run the aircraft (i.e., the navigation system, fuel gauges, flight controls, and hydraulic systems), an ongoing concern with these components is their energy consumption. Frequently, such systems require more power than can be drawn from the aircraft engines' drive generators, necessitating additional power sources, such as a kerosene-burning auxiliary power unit (APU) (or by a ground power unit if the aircraft is not yet in flight). Energy from these power sources may have to travel a significant distance to reach the power-consuming components, resulting in loss of power during transmission and a reduction in overall efficiency of power systems. The total energy consumption can also be rather large, particularly for long flights with hundreds of passengers, and may require significant amounts of fossil fuels for operation. Additionally, use of aircraft power typically produces noise and CO2emissions, both of which are desirably reduced.

The relatively new technology of fuel cell systems provides a promising cleaner and quieter way to supplement energy sources already aboard commercial crafts. A fuel cell system produces electrical energy as a main product by combining a fuel source of liquid, gaseous, or solid hydrogen with a source of oxygen, such as oxygen in the air, compressed oxygen, or chemical oxygen generation. A fuel cell system has several outputs in addition to electrical power, and these other outputs often are not utilized and therefore become waste. For example, thermal power (heat), water, and oxygen-depleted air (ODA) are produced as by-products. These by-products are far less harmful than CO2emissions from current aircraft power generation processes.

However, fuel cell systems and their related electronic components need to be cooled at some points during their use to prevent overheating. It has commonly been the case to provide two separate cooling loops—one for the fuel cell system and one for its related electronic components. However, this adds weight and additional complexity to aircraft systems, which is undesireable.

BRIEF SUMMARY

Embodiments described herein thus provide a single coolant loop that can be used for cooling at least two systems that are generally operable at two different temperatures. Rather than providing two separate cooling loops that can provide the two different cooling temperatures, there is provided a single cooling loop that can route, harness, and mix heated coolant at various temperatures so that the two systems can be served by a single loop.

In a specific embodiment, there is provided a single coolant loop for cooling a fuel cell system and one or more electronic components in the same loop. The coolant loop may include a coolant pump for moving coolant fluid through the loop and a distributor for routing coolant fluid through one of two paths. The first path may be delivery of coolant fluid through a low temperature heat exchanger and then along the path to cool the one or more electronics components. The second path may be by-pass of the electronics components. This path maintains a higher temperature, as it does not pass the low temperature heat exchanger. The first and second paths can converge at a coolant mixer, which combines coolant from the first path with coolant from the second path. Coolant exiting the coolant mixer is of a desired temperature for cooling the fuel cell system, and it may be delivered to the fuel cell system.

The coolant used to cool the fuel cell system exits the fuel cell system at a higher temperature than at which it entered. The warmer coolant exiting the fuel cell is either (i) routed to a heat storage unit or (ii) by-passes the heat storage unit. The by-passed fluid may be delivered to the distributor to be re-routed through the system again, or it may be delivered through a pre-heat loop, wherein the by-passed fluid is delivered back to the fuel cell in order to deliver warmth for its start up.

DETAILED DESCRIPTION

While the embodiments described herein find particular use on-board a passenger aircraft and are generally described in relation thereto, it should be understood that the systems may be used on other vehicles, such as buses, trains, spacecraft, water vessels, or any other appropriate transport vehicle equipped with one or more fuel cell systems. Thus, while the fuel cell technology is discussed herein in relation to use in aircrafts, it is by no means so limited and may be used in any other vehicle.

Fuel cell systems may be used on-board an aircraft (or other vehicle) for generating power. The power may be routed to any appropriate use. More specifically, a fuel cell system is a device that converts chemical energy from a chemical reaction involving hydrogen or other fuel source and oxygen-rich gas (e.g., air) into electrical energy. As illustrated inFIG. 1, a fuel cell system100combines an input of hydrogen or another fuel source110with an input of oxygen and/or air120to generate electrical energy (power)160.

As shown, along with the generated electrical energy160, the fuel cell system100produces water170, thermal power (heat)150, and oxygen-depleted air (ODA)140as by-products. As further illustrated inFIG. 1, some or all of the fuel cell output products of electrical energy160, heat150, water170, and ODA140may be used to operate systems aboard the aircraft.

For example, the fuel cell output products can be supplied to operational systems of the aircraft, such as, but not limited to, systems of a lavatory182or a galley184aboard the aircraft. Output products can additionally and/or alternatively be routed to other operational systems or areas for use where such output products are useful, including, but not limited to, routing heat or heated water to aircraft wings for ice protection, to showers, to the water tank for warming water for hand washing, to the galley for warming water for hot water boilers, to passenger cabins, to passenger seats, or any other location. In other embodiments, the oxygen depleted air may be routed to fuel tanks, passenger seats, or any other location. One or more than one output product can be utilized in any given location, and any given output product may be utilized in one or more locations.

Exemplary, but non-limiting, examples of aircraft systems utilizing fuel cell output products are disclosed in at least the following co-pending applications: International Patent Application No. PCT/US13/030638, entitled “Fuel Cell System Powered Lavatory,” filed Mar. 13, 2013; International Patent Application No. PCT/IB2013/052004, entitled “Power Management For Galley With Fuel Cell,” filed Mar. 13, 2013; International Patent Application No. PCT/IB2013/051981, entitled “Wing Ice Protection System Based On A Fuel Cell,” filed Mar. 13, 2013; and International Patent Application No. PCT/IB2013/051979, entitled “Vehicle Seat Powered By Fuel Cell,” filed Mar. 13, 2013.

Accordingly, by-products from the fuel cell system power generation (such as heat150, water170, and ODA140) may be routed to other systems on-board the aircraft (or other vehicle) for further use. Without directing the heat150to an on-board beneficial use, the heat would otherwise be expelled into the environment. This can have an adverse effect on electronics and other equipment (in the area where the heat is expelled) that may need to be cooled in use.

Because of the heat generated by their operation, fuel cell systems100need to be cooled during use. A standard low temperature fuel cell operates at about 60-80° C. As shown inFIG. 2, a fuel cell cooling loop10may be provided. This cooling loop10uses a cooling fluid that flows along the path shown. The cooling fluid can be routed along the path via a coolant pump12. The coolant pump12routes the fluid to a valve14. This valve14is commonly a 3-way valve that can route the cooling fluid to a deionizer system16or to allow the fluid to travel along to a high temperature heat exchanger18.

The fuel cell100is generally cooled with a water based coolant fluid (e.g., often Glysantin), for which electric conductivity has to be maintained at low level. Accordingly, the valve may route fluid to the deionizer system16to remove ions that make the fluid conductive (because conductive fluid can be detrimental to the fuel cell system100). For example, if the conductivity of the fluid is increasing, the valve14may route the fluid to the system16. If the conductivity of the fluid is at an acceptable level, the valve14may instead direct the fluid to the heat exchanger18.

The high temperature heat exchanger18can transfer heat from the fluid to ambient air in order to deliver fluid that has been cooled to the fuel cell system100. The fuel cell100is then cooled to the desired temperature by the cooled fluid that exits the heat exchanger18. After the fluid cools the fuel cell system100, it is thermally conditioned by a fuel cell system thermal conditioning unit20. This may be necessary because a fuel cell system100needs oxygen and/or air fed to it to create the desired reaction. The gasses fed to it the fuel cell100or that are a by-product of the fuel cell reaction may need to be conditioned. The coolant pump12then continues to move the fluid through the system as required.

FIG. 2also shows an unrelated second cooling loop22that is used to cool electronics systems on-board the vehicle. Most electronics systems operate at between about 50-60° C. This second cooling loop22also uses a coolant pump24to move fluid through the loop22. The coolant pump24delivers cooled fluid to the electronic components26to be cooled. After the fluid cools the electronic components26, it may be thermally conditioned by a thermal conditioning unit28. In one embodiment, the thermal conditioning unit may be an air cooler. The coolant pump12then continues to move the fluid through a low temperature heat exchanger30.

Use of these two separate cooling loops12,22had generally been necessary because of the different cooling temperatures of the different systems to be cooled. The coolant fluid used may be a mixture of glycol and water, Glysantin, ethylene glycol, or any other coolant.

It is, however, not optimal to provide two separate cooling loops. The use of two separate loops requires two separate cooling pumps and two separate heat exchanger units with blowers. However, reducing weight on-board vehicles, and particularly aircraft, is of primary concern. Yet because the operating temperatures of the fuel cell and its associated electronic components (or other electronic components on-board the aircraft) are not identical, combining the cooling loops has not been possible to date.

The present inventors determined how to combine the cooling systems into one coolant loop40, as shown inFIG. 3. This single coolant loop40routes cooling fluid to both the fuel cell system100and to on-board electronic components26(which may be fuel cell electronics or any other electronics). It is beneficial due to its use of a single pump and a single heat exchanger.

One way for this single cooling loop40to achieve the desired temperature differential is by harnessing the heat150generated by the fuel cell system100for later use on-board the vehicle in a heat storage unit34. Operation of the fuel cell system100generates heat150. This heat may be used to condition or re-condition gasses for use in the system by being passed through a fuel cell system thermal conditioning unit44. Then this heat may be stored in a heat storage unit34. Heat storage unit34may be a water reservoir, a thermodynamic cycle, a phase change material, or any other means for storing the heat for later use. For example, the heat may be used for other uses, such as for re-filling of the water boiler, to warm hand-washing water, or any other on-board use. This re-use of heat can help decrease the electricity energy required to be supplied by the fuel cell100and can improve the global system efficiency.

A system controller46may be provided that can coordinate the flow through the cooling loop40, depending upon the needs of the aircraft for heat150as a fuel cell by-product. For example, the system controller may receive temperature information from the higher and lower temperature systems (i.e., the fuel cell system and the electronics components) and can route coolant fluid through the coolant loop as needed based on the temperature information. If heat is not needed for use on-board (nor expected to be needed based on the current air temperatures or flight schedule), then the controller46may cause the heat storage unit34to be by-passed. Instead, the heat150may be delivered to the coolant fluid, which is routed through the coolant loop system40via a single coolant pump48.

Although the controller46and coolant pump48is shown at a particular locations inFIG. 3, it should be understood that they may be located anywhere along the coolant loop40as necessary. It is generally desired that only a single coolant pump48be used in order to reduce system weight and cost, although this is not required. Moreover, other components in the schematic shown may be moved elsewhere. The general goal is to provide the desired flow of coolant fluid and the desired exchange of heat prior to delivery of the coolant fluid to the particular systems described.

The coolant fluid used in the system may be any appropriate coolant fluid. However, in one embodiment, it has been found particularly useful to use a dielectric coolant fluid. This can render the coolant fluid circuit more simple, reliable, and permits removal of the deionizer system16of the prior art system. The dielectric coolant can be mixed into the single coolant loop40disclosed, for cooling the two primary systems (the fuel cell system100and the electronic components26). The dielectric property of the coolant means that it does not conduct electricity and will not generate ions. Such coolants are generally more inert and do not degrade as easily as some other fluids. The fluid used can be temporarily or permanently dielectric. Non-limiting examples of potential coolants that may be used in connection with the disclosed coolant loop40include but are not limited to Galden, which is a PFPE (perfluoropolyether), PAO (polyaromatic polyolefin), petroleum derived coolants, oil based coolants, or any other appropriate coolant fluid.

If the coolant fluid bypasses the heat storage unit34, it may be routed appropriately via a distributor50. Distributor50may be a valve or any structure with outlets sized to separate inflow of fluid into outward sub-flows. In one particular embodiment, the distributor50may be an electronically controlled valve that adjusts positions based on temperature and other inputs. In flow route A, the fluid is routed to a low temperature heat exchanger52and then on to the electronic components26.

In flow route B, the fluid bypasses flow route A and is routed to a coolant mixer56for delivery to the fuel cell system100. The distributor50determines where to send the fluid based on temperature needs from the electronic components26and the fuel cell system100. For example, if cooling of the electronic components26is required, the distributor50generally routes fluid along path A. If cooling of the electronic components26is not required, the distributor50may then route fluid along path B. The distributor50may receive temperature input in any form. For example, the distributor50may receive temperature input in the form of an inlet temperature reading from the fuel cell100. As another example, the distributor50may receive temperature input in the form of a temperature reading from the electronic components26. Any appropriate temperature feedback loop may be provided so that the distributor can route the fluid as appropriate.

Referring now to flow route A, the low temperature heat exchanger52causes the fluid to be cooled to about 50-60° C., due to input of ambient air into the heat exchanger52. The incoming ambient air can be replaced by any cold source or source of air that has a generally low temperature. Cooling the fluid to about 50-60° C. provides fluid at the desired temperature for routing through the electronic components26in order to lower their temperature due to heat generated by their operation. Because heat is transferred to the cooling fluid during the electronics cooling step, a second fuel cell thermal conditioning unit54may be provided. This unit54may be provided in order to lower the temperature of the fluid leaving the electronic components26.

The fluid leaving the second fuel cell thermal conditioning unit54is delivered to a coolant mixer56. Coolant mixer56is provided in order to mix the fluid leaving the second fuel cell thermal conditioning unit54with fluid that enters the coolant mixer through path B, which bypasses electronic components. The fluid in path B is warmer than the fluid in path A. Path B fluid has bypassed the electronic components, and it generally contains at least some warmth from heat150leaving the fuel cell system100. The coolant mixer56combines cooled fluid from path A with warmer fluid from path B. The coolant temperature from the two incoming streams of coolant (flow path A and flow path B) is generally homogeneous at the outlet of the mixer. Fluid exiting the coolant mixer56is thus between about 60-80° C., which is the desired operating temperature for the fuel cell.

FIG. 3also shows a short pre-heat loop58. This pre-heat loop58is provided to deliver heat to the fuel cell system100for start-up. In some instances, it may be desirable to start the fuel cell system100when it is cold. However, the preferable operational temperature for the fuel cell system100is between about 60-80° C. In this case, the fuel cell needs to have an amount of heat delivered to it in order to be functional. Accordingly, pre-heat loop58routes heat leaving the fuel cell system100before it reaches the distributor50. The loop58may harness heat from the heat storage unit34. The loop58may harness heat from the warmed coolant leaving the fuel cell system100. The loop58routes one or more sources of this heat back to the fuel cell through the pre-heat loop58in order to provide warmth for fuel cell start-up.

Although one potential arrangement of the various components of the coolant loop40has been shown, it should be understood that the components may be arranged differently. It is generally desired that the coolant flow function as described in order to cool the fuel cell system100and the electronic components26.

The systems described herein are useful in connection with any appropriate fuel cell system100, which may include but is not limited to a Proton Exchange Membrane Fuel Cell (PEMFC), a Solid Oxide Fuel Cell (SOFC), a Molten Carbonate Fuel Cell (MCFC), a Direct Methanol Fuel Cell (DMFC), an Alkaline Fuel Cell (AFC), or a Phosphoric Acid Fuel Cell (PAFC). Any other existing or future fuel cell system technology, including, but not limited to, a hybrid solution, may also be used.

In summary, the use of a single low temperature heat exchanger52with a passive (or active) distributor50and a by-pass way allows management of the fuel cell temperature and the electronics temperatures in their respective optimal temperature ranges. This can achieved using only a single coolant pump48and a single air blower (for the low temperature heat exchanger52). Depending upon the environmental conditions, at least one or more components can be removed due to natural and efficient cooling. The cooling circuit is not limited to cooling a fuel cell and/or its electronics system, but may be used for any and all applications that may need cooling or heating on-board an aircraft.

A single coolant loop for cooling at least two systems having different operating temperatures, the single coolant loop comprising:

(a) a coolant pump for moving coolant fluid through the loop;(b) a distributor for routing coolant fluid through one of two paths;(c) a first path, comprising delivery of coolant fluid through a heat exchanger and to cool a first system;(d) a second path, comprising by-pass of the first system;(e) wherein the first and second paths converge at a coolant mixer, wherein the coolant mixer combines coolant from the first and second paths.

In this example, the first system may be one or more electronic components and the second system may be a fuel cell system.

A single coolant loop for cooling a fuel cell system and one or more electronic components in the same loop, comprising:

(a) a coolant pump for moving coolant fluid through the loop;(b) a distributor for routing coolant fluid through one of two paths;(c) a first path, comprising delivery of coolant fluid through a low temperature heat exchanger and then to cool the one or more electronics components;(d) a second path, comprising by-pass of the electronics components;(e) wherein the first and second paths converge at a coolant mixer, wherein the coolant mixer combines coolant from the first and second paths;(f) wherein coolant exiting the coolant mixer is delivered to the fuel cell system;(g) wherein warmer coolant exiting the fuel cell either (i) is routed to a heat storage unit or (ii) by-passes the heat storage unit.

As shown inFIG. 4, the disclosure also relates to a method of routing coolant along a single loop for cooling a higher temperature system and a lower temperature system. The method includes (a) routing warmed coolant fluid from the higher temperature system to either (i) a heat storage unit (ii) a distributor, or (iii) back to the higher temperature system for start-up warmth; (b) routing the coolant from the distributor either to (i) the lower temperature system via way of a low temperature heat exchanger or (ii) by-passing the lower temperature system; (c) routing coolant fluid from the lower temperature system to a coolant mixer; and (d) routing coolant fluid from the coolant mixer to the higher temperature system.

Changes and modifications, additions and deletions may be made to the structures and methods recited above and shown in the drawings without departing from the scope or spirit of the invention and the following claims.