FORM 2
THE PATENT ACT 1970 (as amended)
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See Section 10 and Rule 13]
TITLE: “SYSTEM AND METHOD FOR CONTROLLING TEMPERATURE OF
A FUEL CELL STACK”
Name and address of the Applicant:
TATA MOTORS LIMITED, an Indian company having its registered office at
Bombay house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra,
INDIA.
Nationality: INDIAN
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

TECHINCAL FIELD
Embodiments of the present disclosure relate to fuel cell stack. More particularly, the embodiments relate to controlling temperature of a fuel cell stack.
BACKGROUND OF DISCLOSURE
The effects of operating temperature on fuel cell stack are as following: At higher operating temperatures, the fuel cell voltage increases at a given operating current density because higher the operating temperature the more active the reactants. The higher the operating temperature the water vapor present is more in the reactant stream to maintain a given relative humidity. This makes it more difficult to maintain a relative humidity at or near 100%. The higher the stack outlet temperature, the more water is evaporated in the stack, which reduces the heating load on the coolant system. Hence, the higher the temperature the more water can be evaporated. Heat is absorbed in evaporating the water; all the heat used in evaporation is heat that would otherwise have to be rejected by the coolant system.
Lower operating temperatures of the fuel cell stack results in longer stack life, which is due to better humidification. Operation at lower stack temperatures may result in water management problems. Reducing the amount of water vapor required to achieve 100% RH (relative humidity) is a mixed blessing; if the RH exceeds 100%, due to water formation in the cathode or water crossover in the anode, water droplets will form. If the quantity of liquid water present is more, it can block the cell channels and result in cell starvation.
In light of forgoing discussion, there is a need to regulate temperature of the fuel cell stack.
STATEMENT OF THE DISCLOSURE
Accordingly the present disclosure provides a system 100 to control temperature of fuel cell stack in a vehicle comprising a fuel cell stack 102; a radiator 104 connected to an inlet of the fuel cell stack 104, said radiator consisting of plurality of fans to reduce heat from the fuel cell stack 104; a coolant pump 106 connected to the fuel cell stack 102

through the radiator 104 to circulate coolant to the fuel cell stack 102; a temperature sensor 108 connected to an outlet of the fuel cell stack 104, said temperature sensor 108 measures temperature of the coolant coming out of the fuel cell stack; heater and water dispensing system 110 connected to the coolant pump 106 to heat the coolant; and a controller 112 connected to the coolant pump 106 to monitor the temperature of the fuel cell stack 102, said controller 112 receives temperature level from the temperature sensor 108, calculates temperature variation by comparing received temperature level with predefined temperature level at a given time to switch ON or OFF predetermined number of radiator fans to control the temperature of the fuel cell stack 102; and the disclosure also provides for a method of controlling temperature of a fuel cell stack system 100 comprising acts of measuring temperature of the fuel cell stack 102 at a given time; calculating temperature variation by comparing the measured temperature with predefined temperature level; switching ON a radiator fan if the temperature variation is greater than zero else switching OFF a radiator fan; and repeating all the above steps periodically at a predefined time interval to control the temperature of a fuel cell stack system.
OBJECTIVES OF THE DISCLOSURE
The main object of the instant disclosure is to obviate the above mentioned drawbacks.
Another object of the present disclosure is to provide a system to control temperature of fuel cell stack.
Yet another object of the present disclosure is to provide a method for controlling temperature of fuel cell stack.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example

only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:
Figure 1 illustrates the system block diagram to control the temperature of the fuel cell stack.
Figure 2 illustrates schematic of piping and instrumentation of the fuel cell stack system.
Figure 3 illustrates flow chart for method of controlling the temperature in the fuel cell stack system.
The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the accompanying figures, which form a part hereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, figures, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.
One embodiment of the present disclosure provides a system 100 to control temperature of fuel cell stack in a vehicle comprising a fuel cell stack 102; a radiator 104 connected to an inlet of the fuel cell stack 104, said radiator consisting of plurality of fans to reduce heat from the fuel cell stack 104; a coolant pump 106 connected to the fuel cell stack 102 through the radiator 104 to circulate coolant to the fuel cell stack 102; a temperature

sensor 108 connected to an outlet of the fuel cell stack 104, said temperature sensor 108 measures temperature of the coolant coming out of the fuel cell stack; heater and water dispensing system 110 connected to the coolant pump 106 to heat the coolant; and a controller 112 connected to the coolant pump 106 to monitor the temperature of the fuel cell stack 102, said controller 112 receives temperature level from the temperature sensor 108, calculates temperature variation by comparing received temperature level with predefined temperature level at a given time to switch ON or OFF predetermined number of radiator fans to control the temperature of the fuel cell stack 102.
In one embodiment of the present disclosure, the predefined temperature level ranges between 65ºC to 75ºC.
In one embodiment of the present disclosure, the predetermined number of radiator fans ranges between 1 to 12.
In one embodiment of the present disclosure, the controller 112 switches ON the heater 110 to heat the coolant if the temperature is less than 40º C.
In one embodiment of the present disclosure, the heater and water dispensing system 110 is connected with a humidifier system 114 to control humidity in the fuel cell stack 102.
The present disclosure is also in relation with a method of controlling temperature of a fuel cell stack system 100 comprising acts of measuring temperature of the fuel cell stack 102 at a given time; calculating temperature variation by comparing the measured temperature with predefined temperature level; switching ON a radiator fan if the temperature variation is greater than zero else switching OFF a radiator fan; and repeating all the above steps periodically at a predefined time interval to control the temperature of a fuel cell stack system.
In one embodiment of the present disclosure, the system is heated if the measured temperature is less than 40º C.

In one embodiment of the present disclosure, the predefined temperature level ranges between 65ºC to 75ºC.
In one embodiment of the present disclosure, number of radiator fans ranges between 1 to 12.
In one embodiment of the present disclosure, the predefined time interval ranges between 5 to 30 seconds, which depends on the capacity of radiator fan heat rejection capacity.
To over come the drawbacks mentioned in the background, the fuel cell stack must be operated within the range of its operating temperature and maintain an optimum mass flow rate for coolant in the fuel cell stack. Power demand for the vehicle varies with time; as the current drawn from the fuel cell stack varies, the excess heat generated in the stack also varies with time. This heat needs to be carried out of the stack by the coolant and thus its mass flow rate has to be carefully decided.
In one embodiment, the thermal management system removes heat from the fuel cell stack by providing coolant at the correct inlet temperature to the stack. Optimum temperature range of operation for PEM (Proton Exchange Membrane) fuel cell ranges in between 65°C to 75°C. Heat generated in the fuel cell stack must be removed to maintain the optimal operating temperature of the fuel cell stack.
In one embodiment, figure 1 shows a system block diagram 100 to heat and regulate or control the temperature of fuel cell stack 102. The fuel cell stack 102 is an electrochemical device, which generates the tower and heat. For optimum performance and extended durability of stack it is required to maintain its temperature between 65oC to 75oC.
The system 100 comprises a coolant pump 106 to circulate the coolant into system 100 with variable speed drive to vary the flow rate of the coolant. A radiator 104 connected to the stack removes the excess heat from the system by means of throwing the heat into atmosphere through fans. Heat dissipation of radiator 104 depends on no of fans switched on and flow rate of coolant running into system. At any given time, any number of the

fans can be switched on using a controller. Thus by deciding the number of fans to be switched on, desired amount of heat can be dissipated by the radiator. The radiator fans can be driven by Electrical/Pneumatic/Hydraulic. The number of fans range in between 1 and 12.
The system 100 further comprises of a heater and water dispensing system 110 comprising a heater to heat the coolant, if the coolant is below 40º C. Water dispensing system 110 sprays the water in mist form into humidifier system 114. An air compressor 116 is connected to the heater and water dispensing system 110 for supplying required air flow to the system based on demand. A humidification system or humidifier 114 is connected to the heater and water dispensing system to humidify the air and takes required heat for humidification from the hot fluid coming out of the stack. By regulation of temperature of coolant which also regulates the humidity.
A temperature sensor 108 is connected to outlet of the fuel cell stack 102 to sense the temperature of the coolant or fluid coming out of the fuel cell stack102. A controller 112 comprising of an electronics control unit (ECU) which takes the input from sensors and generates the control signals for the radiator fans and the coolant pump 106. The system 100 is designed in such a way that to work at any ambient condition/ temperature.
For optimum performance and extended durability of fuel cell stack system 100, it is required to maintain the temperature between 65oC to 75oC. As the fuel cell stack 102 generates powers as by-products it generates the heat also. Higher the generated power, higher the heat generation. To remove the generated heat from system a cooling system is required. Based on change of temperature and temperature, increase/decrease the no of fans in operation.
Figure 2 shows piping and instrument diagram (P & ID) replicating the flow diagram with all instruments and equipments 200. The P & ID shows that testing arrangement has been done for testing the controller. The heater 210 with coolant tank 202 mimics the heat generated by stack during operation. In order to remove heat from the stack, radiator 206 with at least 6 fans 212 has been joined to series to coolant tank 202 with two coolant

pump, to meet the flow requirements. The coolant flows from coolant tank 202 to radiator 206 by means of coolant pump 204. Temperature sensors are placed in between to measure the temperature of coolant before and after coolant tank 202. Based on the temperature measured the fans 212 are switched ON and OFF.
In one embodiment, a method of heating is described as follows; the fuel cell stack generates continuous power if its operating temperature is more than specified limit, around 40oC. For cold climatic conditions, ambient temperature will be far below the specified limit. For the rapid start up of the system or vehicle, heater is required to raise the temperature of the system. Heater comprises of a resistor. Power required by the heater is supplied by battery.
Figure 3 shows the flow chart for the method of controlling or regulating of temperature
300.
As shown in the flow chart i.e. in figure 3, initially, none of the radiator fan is switched
ON, as shown in step 302 in the fuel cell stack system. Let the temperature of coolant (T)
is monitored at predefined set time duration, as shown in step 304, i.e. ranging between 5
to 30 seconds and calculate change in temperature (∆T) as shown in step 310.
Upon measuring the change in temperature as shown in step 310, action is taken based on the following condition:
In step 306, if the monitored temperature T is less than 40o C, switch ON the heater to heat the coolant.
If T is lesser than predefined temperature value i.e. 65o C and ∆T equals to zero then no change in current radiator state, as shown in step 316;
If T is greater than 65o C and ∆T is greater than zero, then increase radiator state by one in current radiator state, as shown in step 314.
If T is greater than 65o C and ∆T is less than zero, then decrease radiator state by one from current radiator state, as shown in step 312.

Next, the radiator state is changed to the current radiator state. State one means i.e. as shown in step 314, providing a signal to the controller to switch ON a fan. Maximum number of states is six or twelve, as there are six or twelve fans in the radiator. If the state changes, the number of fans in operation also changes.
In step 306, if the monitored temperature is less than 40o C, switch ON the heater to heat the coolant.
The larger the load current drawn from the fuel cell stack, it generate more heat. Therefore, more heat has to be rejected by the radiator. Increase in coolant Pump rpm will rotate more coolant in the coolant circuit and as result it remove more heat from system. So, directly link load current drawn from stack and heat generation by stack by means of temperature to coolant pump speed.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

We claim
1. A system 100 to control temperature of fuel cell stack in a vehicle comprising:
a fuel cell stack 102;
a radiator 104 connected to an inlet of the fuel cell stack 104, said radiator consisting of plurality of fans to reduce heat from the fuel cell stack 104;
a coolant pump 106 connected to the fuel cell stack 102 through the radiator 104 to circulate coolant to the fuel cell stack 102;
a temperature sensor 108 connected to an outlet of the fuel cell stack 104, said temperature sensor 108 measures temperature of the coolant coming out of the fuel cell stack;
heater and water dispensing system 110 connected to the coolant pump 106 to heat the coolant; and
a controller 112 connected to the coolant pump 106 to monitor the temperature of the fuel cell stack 102, said controller 112 receives temperature level from the temperature sensor 108, calculates temperature variation by comparing received temperature level with predefined temperature level at a given time to switch ON or OFF predetermined number of radiator fans to control the temperature of the fuel cell stack 102.
2. The system as claimed in claim 1, wherein the predefined temperature level ranges between 65ºC to 75ºC.
3. The system as claimed in claim 1, wherein the predetermined number of radiator fans ranges between 1 to 12.
4. The system as claimed in claim 1, wherein the controller 112 switches ON the heater 110 to heat the coolant if the temperature is less than 40º C.
5. The system as claimed in claim 1, wherein the heater and water dispensing system 110 is connected with a humidifier system 114 to control humidity in the fuel cell stack 102.

6. A method of controlling temperature of a fuel cell stack system 100 comprising acts
of:
measuring temperature of the fuel cell stack 102 at a given time;
calculating temperature variation by comparing the measured temperature with predefined temperature level;
switching ON a radiator fan if the temperature variation is greater than zero else switching OFF a radiator fan; and
repeating all the above steps periodically at a predefined time interval to control the temperature of a fuel cell stack system.
7. The method as claimed in claim 6, wherein the system is heated if the measured temperature is less than 40º C.
8. The method as claimed in claim 6, wherein the predefined temperature level ranges between 65ºC to 75ºC.
9. The method as claimed in claim 6, wherein number of radiator fans ranges between 1 to 12.
10. The method as claimed in claim 6, wherein the predefined time interval ranges between 5 to 30 seconds, which depends on the capacity of radiator fan heat rejection capacity.
11. A system to control temperature of fuel cell stack in a vehicle and a method of controlling temperature of a fuel cell stack system are substantially as herein above described and as illustrated in accompanying drawings.