Fuel Cells for Use in Automotive Applications

1 Introduction

As per the topic regarding Fuel Cells for use in Automotive Applications, lot of stuff is here to discuss and of one of them is that there is a need for accelerating the deployment of renewable energy technologies. That is our main focus form which we are going to move forward and will carry on discussion.

1.1 Renewable Energy Technologies & Problems

As per the demand of the coming new era, renewable energy technologies are on the peak to discuss and to investigate. That’s the hot topic of the upcoming years and needs to be further investigated. All know about the gasoline products, originate their actions and reactions with the combustion process, resulting too much pollution in an environment which is hazardous for animal, plants and human beings. You know the rapid increase in population all over the world. As per United Nations’ statistics (United Nations, 2019), population can reach peak at nearly 11 billion around the year 2100. This is a too much count. So, all must understand now as per population’s statistics, there is now an increase in demand regarding transport, vehicles etc, resulting too much gasoline’s product’s usage in transport like in buses or in vehicles. Governments, are now thinking over technologies from which there is no pollution just like hydrogen fuel cells instead of conventional gasoline’s products. This hydrogen fuel cell technology is basically a renewable one. Besides this, Biomass is also a renewable technology but as not much efficient as hydrogen fuel cells. It had already been discussed to think over such type of renewable technology just like hydrogen fuel cells in comparison with conventional products, said by Senate Finance Committee Chairman, Wyden (Mantzner, 2014) to facilitate hydrogen fuel cell’s vehicles and transportation. As per assignment’s requirement, our core concern is fuel cell in automotive applications just like discussed here; vehicles and transport. Besides all this, one of the major concern or key issue surrounding the fuel cell is its high cost. These all are the concerns, we are going to discuss below in further detail.

2 Fuel Cells & Their Applications

As per the fuel cell and its constituents, at first, we have to understand the terms fuel cell and its constituents. Fuel cell is basically composed of an individual cell or it may be a form of stack that is a collection of more than one cell. While its constituents means the components which make the fuel cell like electrodes (anode and cathode), membrane, electrolytic solution (may be liquid or solid) (FCHEA). Fuel cell is basically a device, used to provide energy in comparison with gasoline normal products by electrochemical chemical reactions and fuel cells provide energy very quietly in comparison with gasoline products which generate a lot of noise with pollution too. They need not to be recharged periodically but need a constant fuel supply just like hydrogen and oxygen. Working of a fuel cell include the reactions of hydrogen and oxygen, resulting usable electricity. Actually, these both gases are passed form a concentrated solution via electrodes. This process is very slow and in order to fast this whole reaction, catalyst is used. Electrons are concentrated at one electrode while protons are passed through membrane. Electrons then are made the major cause for generation of electricity (Fabio Leccese, 2013). Moreover, regarding each cell type, reactions are given below. We are going to discuss here five major and common types of fuel cells which are used widely and developments are being made on these cells for further improvement and advancements (BYJUS, 2020).

2.1 Alkaline Fuel cell (AFC)
These cells use potassium hydroxide solution in water as its electrolyte and may use non precious catalyst at anode and cathode to fast the electrochemical reaction. These are the technologies developed earlier especially for use in spacecrafts and in underwater applications as these are susceptible to carbonate formation by carbon dioxide and this resulting decline in durability and its performance too. For this reason, as per recent developments, Alkaline Membrane Fuel Cell (AMFC) were introduced to overcome corrosion and wettability factor induced by carbonate formation in order to increase its performance and durability. These cells contribute above 60% efficiency in space and underwater applications. Besides the challenge of corrosion and wettability, other challenges include higher temperature operation, power density and its membrane conductivity (EERE). As per reactions, details are given as under;
Anode reaction:H2 + 2OH → 2H2O + 2e , Cathode reaction:  ½O2 + H2O + 2e → 2OH and Overall reaction:  H2 + ½O2 → H2O (CE, 2013).
Figure 2.1.1 (AFC) (Smithsonian Institution, 2017)
                                                      

2.2 Polymer Electrolyte Membrane Fuel Cell (PEM)
These cells use solid polymer as an electrolyte as compare to liquid electrolyte used in AKF due to which its conductivity is improved. For this reason, there is no any challenge faced regarding power density. Platinum catalyst is used in these cells which make these costly in comparison with AKF. These operate at lower temperatures means these cells take lower start up time, due to this, these are best for use in transportation like buses or in vehicles (EERE). Reactions are given as under;
Anode reaction: H2 → 2H+ + 2e , Cathode reaction: ½O2 +2H+ + 2e → H2O and Overall reaction: H2 + ½O2 → H2O (CE, 2013).
Figure 2.2.1(Smithsonian Institution, 2017)
                                                                   

2.3 Phosphoric Acid Fuel Cell (PAFC)
Regarding electrolyte, in these cells, liquid phosphoric acid is used for this purpose. Platinum catalyst is used in it due to which its cost is increased than other cells that use non precious catalyst. Instead of using these cells alone, at which they produce an efficiency of around 42%, these are used in co generation to produce by products in terms of heat and water besides electricity generation and this results an efficiency of around 85%. These are mostly operated at lower temperatures due to which these are used mostly in transport like bused or in vehicles. You may refer figure 2.2.1 for PAFC (EERE). Reactions are given as under;
Anode reaction: H2 → 2H+ + 2e , Cathode reaction: ½O2 +2H+ + 2e → H2O and Overall reaction:H2 + ½O2 → H2O (CE, 2013).

2.4 Molten Carbonate Fuel Cell (MCFC)
These basically use an electrolyte composed of molten carbonate salt mixture suspended in lithium aluminum oxide. They usually operate at higher temperatures than other cells due to which their start up time is not as much fast as in other cells, for which, these are used in industrial and in military applications. But the cost is reduced as due to high temperature, non precious catalyst may be easily used. The high temperature reaches at around 650 degree centigrade and this is too much to use such type of catalysts (EERE). Reactions are given as under;
Anode reaction: H2 + CO32  → CO2 + H2O + 2e , Cathode reaction: ½O2 + CO2 + 2e → CO32 and  Overall reaction:  H2 + ½O2 → H2O (CE, 2013).
Figure 2.4.1 (Smithsonian Institution, 2017)

2.5 Solid Oxide Fuel Cell (SOFC)

These cells use non porous ceramic compound as an electrolyte but operate at high temperatures a around 1000 degree centigrade. This high temperature makes anyone enable to use non precious catalyst. Due to its high temperature, there is no need of any reformer which is used to produce hydrogen for its fuel. So, no precious catalyst and this reformer reason reduces its cost and makes it cheaper than others. These are used in co generation instead for use in alone to produce high efficiency of around 85%. The challenge due to its high temperature is its durability issues on which scientists are working (EERE). Reaction are given as under;
Anode reactions: H2 + O2 → H2O +2e and CO + O2  → CO2 + 2e , Cathode reaction: O2 + 4e → 22 and Overall reaction:  H2 + O2 + CO → H2O + CO2 (CE, 2013).
Figure 2.5.1 (Smithsonian Institution, 2017)

                                                          


3. Cussons’ P9040 Unit
                                                   

3.1 Introduction of Equipment & its Constituents

The above figure; figure 3.1 is basically a Cussons P9040 Unit which we are going to discuss here as per experimental purpose to study fuel cell. Besides too many useful calculations, performance, means the efficiency parameter is also calculated by using this unit. Many physical quantities are encountered in this fuel cell’s experiment like voltage, load, power, hydrogen consumption rate in cc/minute, efficiency and current. These are helpful in calculating the value of the required ones. Furthermore, working of a fuel cell can be easily understood by this demonstration unit. Must be keep in mind that hydrogen gas is used as a fuel in this system which is highly flammable, so, must be careful regarding leakage of hydrogen gas which may be dangerous as there must be no leakage when hydrogen is supplied to the system. Moreover, this all experiment must be done in a ventilated environment or room because of hydrogen gas. The cussons unit is basically composed of a control unit at which voltmeter and an ammeter is embedded in order to note down the voltage and current in amperes respectively. Fuel cells in a form of stack (a stack of 10 connected cells ) are mounted on the top of the control unit to give an output of 10 to 12watts at 6V DC (Direct Current). A quantity of 2 psi (pounds per square inch, unit of pressure) and a flowrate of 160 cc/min (cubic centimter per minute) is used as a fuel for hydrogen gas. This is a self contained system, that means it does not require external electrical supply but use hydrogen fuel as its energy and operation. This is brief knowhow about little bit information regarding cussons’ equipment. Carry forward, we are going to discuss fuel cells working as per cussons unit, graphs; which will be helpful in understanding the comparisons between different quantities by putting some values extracted from this experiment and finally we will discuss a little bit regarding formulae for efficiencies’ calculations. These all will finally help greater in understanding the whole scenario of fuel cell system by P9040 unit (Cussons Technology LTD, 2004).

3.2 Working of Unit with Results’ Analysis

Analysis of Units’ results are basically extracted from calculations (given in the below tables) and form graphs which are very helpful for study regarding quantities involved and their comparison. First of all, working of a unit is very important to understand the concept of fuel cell with P9040 unit. To start the whole system, spray the distilled water from the air holes. Pass hydrogen gas with specified pressure as indicated above with a given flowrate. We must have to pass the gas roughly from 1 to 2 seconds by removing the pipe on the outlet. Now this is the mode, you may say that the system is running. On the contrary, in order to stop the stack, select the selector switch; a switch which is used to on or off the whole operation, then increase the value of its load to its maximum value by keeping in mind that to not supply any further hydrogen gas in this state and when the value of the voltage reaches to zero, set the selector switch to its off state. Everyone, who is performing this experiment must keep in mind that to dismantle the hydrogen gas kit from the system as for now, system is not in running mode. This also ensures safety as after all this, hydrogen supplied kit must be isolated in order to avoid any explosion (Cussons Technology LTD, 2004). Do the experiment with and without fan assistance to conclude concrete results. With fan, there will be a pressure of air blow, gives more oxygen and thus finally produce good power output. On the contrary, if we will use the whole experiment without any fan assistance, this gives us the less power output in comparison with the power output produced in fan assistance. Now we will move towards the results, shared in terms of table and graph that will provide us better understanding.

Table 3.2.2

Table 3.2.3

Table 3.2.4

First of all, we will have to understand the terminologies used in tables. After that, we will move forward. L means Load, V means Voltage, A means Ampere, FR means Flowrate, P means Power, TC means Theoretical Current, CE means Current Efficiency, VE means Voltage Efficiency, TP means Theoretical Power while TE means Thermal Efficiency. Figure 3.2.1 and its corresponding table which is related without fan assistance; depicts that by increase in current, values of power and voltage are reduced. Though values are high in start, but are being reduced by further increment in current physical quantity’s value. Comparison may also be easily understood by watching graph with its associated table in which thorough calculations are made in order to understand the scenario regarding each and every physical quantity involved in the experiment. In comparison with the same values but with the assistance of fan(refer fig 3.2.2 and its corresponding table), now the scenario has become changed as fan is included and due to which there is increased in power quantity as all know that flow of air will produce more oxygen resulting more power. Moving forward, for the case given in fig 3.2.3 and in fig 3.2.4 with their corresponding tables, in both the above plotted cases with their tables, hydrogen’s consumption rate is being increased with the increase in power. Though there is a slight power values’ increment in the case with fan assistance but both are nearly showing the same results. For precise values, graphs and tables may be referred. Now the last one, fig 3.2.5, in which comparison is made between load and power. We all know that there is a direct relationship between load and power, that means increment in one value causes an increment in other value too. Finally, efficiencies’ equations are given here to calculate efficiencies; for current efficiency, CE=(Observed Current/Theoretical Current)*100 while overall efficiency is; OE=(Observed Efficiency/Theoretical Efficiency)*100. All of these calculations are made and graphs are plotted in order to go through the efficiency resulting to go through the overall performance of the fuel cell, which is the major concern of this cussons experiment.

4. Conclusion

Every experiment is made to judge the scope of efficiency resulting performance. Above experiment is done to judge these elements. If we discuss performance parameter regarding fuel cell in comparison with gasoline products, performance of fuel cells is at high pace in comparison with conventional gasoline usage in which combustion is taken place resulting around 30 to 35 percent of efficiency. While in fuel cells, efficiency may reach up to 80 85 percent. Such a marvelous achievement, a fuel cell is in which developments are still being made for further improvement. Regarding transportation, especially in public buses or in local vehicles, scientists are making their efforts at their best to overcome the key issues surround the fuel cell renewable technology. Moreover, in developed countries, higher authorities just like UK, are thinking over to ban gasoline usage which produces a lot of pollution with noisy environment with decreased performance. No doubt, there too many challenges that come into play while introducing fuel cell renewable technology, just like key issues with durability, temperature, conductivity, cost and many more than that. As per transportation’s perspective, the best fuel cells are PEM in which hydrogen is used as a fuel. One of the best key performance’s parameter is its P/W ratio or power by weight ratio which is very good, resulting excellent power with low weights. This quality of cell makes this special in front of the others. As vehicles and transport, like buses require immediate start and stops, which may be fulfilled by these cells as these operate at low temperatures due to which immediate start and stops are possible with these types of cells. But still there are a lot of challenges with these cells and one of them is its high cost. Due to precious catalyst, it costs high. Engineers and scientists are still trying their best in order to cope up with this serious problem and developments are still being made to find the best solution.
Another fuel cell which may be used in comparison with PEM, is AFC or AMFC. These cells use liquid electrolyte instead of solid electrolyte just as used in PEM resulting water and electrolyte management’s issues are generated. These are just like PEM which operate at lower temperatures due to which these are also best fir for vehicles and for in local transport just as in buses. Due to its liquid electrolyte, these cells may face corrosion formed by carbonate formation. This is the challenge which scientists are trying to mitigate. Furthermore, due to liquid electrolyte, there are conductivity issues too. To overcome such type of problems, faced by AFC, scientists have introduced AMFC stands for Alkaline Membrane Fuel Cell which have lower corrosion factor as in AFC but still, there are challenges in these cells, discussed above.
Furthermore, with PEM and AFC, MCFC and SOFC are also the major concerns and developments are being made regarding the later ones too. As discussed, there are a lot of challenges faced by scientists but the major one which prevents the commercialization of a fuel cell is its cost which is high due to the usage of precious catalyst just like platinum. Besides this, durability also plays an important role for commercialization of fuel cell. These two factors are very important in respect of commercialization. Engineers and scientists are trying their best to overcome on the durability issue and to introduce no precious catalyst for PEM and for AFC so that these may be easily used in transportation or vehicles. Besides all this, there are issues with conductivity too just like in AFC that’s why AMFC is introduced. Due to all this, as in AMFC, membrane factor was introduced to overcome or to mitigate the low conductivity issue. If we discuss about PEM, engineers are trying to increase mechanical, chemical and thermal stability with improving its conductivity too. Different types of models (like one discussed above; P9040), tools and diagnostic’s equipments are being made to test for the best fuel cell. All these developments are being made in order to provide good transportation to the public especially in terms of public buses.
As per concerns regarding durability and cost which are the major barriers (as discussed earlier) in the process of commercialization of fuel cells, the target for bus transport or for vehicles is 5000 hours durability which is a very healthy durable count. Regarding cost, not just platinum like electrolytes plays role in increasing the cost but membrane of fuel cell, hardware used, reformers used (in case of gas is reformed into hydrogen gas), reactors, bi polar plates, all these factors play role in cost increment. As compared to traditional gasoline’s transport, these fuel cells are very costly but are very favorable in creating pollution and noise free environment but engineers need to think over all such stated factors due to which we have to pay too much for these fuel cells and no doubt, as discussed before, developments are still being made to induce improvements and betterment. Durability factor actually come over due to frequent start and stop of buses/vehicles, impurities in the fuel, chemical and mechanical in stability, materials and components, all these play their role to introduce durability issues. These are actually the technical barriers which are being faced.

Another major factor is performance and it must be improved further to give better output power and efficiency with cost and durability factors. Performance in degradation may result from several factors like from cell issues, stack water management, system thermal, water and air management and start up/shutdown times. We will discuss here cells’ issues and start up/shutdown times for ease and convenience which are also the key issues with respect to degradation in performances in fuel cells. Regarding cell issues, let’s take an example to understand this key issue, like bad or poor cathode’s operation resulting over potential issues of 0.4v or greater and this actually decreases the overall performance with efficiency too. Means, loss of around one third energy due to this poor cathode’s operation. Moreover, for cathodes, at high current densities with reducing quality factor of Platinum catalyst also introduce losses which are also under observation and need to be improved. Membrane issues in fuel cells regarding their conductivity also degrade performance resulting decrease in efficiency. So, a lot of factors must need to be improved to provide good results with ease in commercialization. Now moving towards the next key issue with respect to performance that is start up/shutdown times. Briefly, as discussed before in detail that automotive applications just like buses must start as soon as possible or in rapid action so there is a need of quick start up time and as all knows that vehicles/buses use immediate start and stops. So, there are cells which can do that but still, there is a need of improvements in a lot of sectors regarding this start up/shutdown times in order to finally improve the performance. The new era for the new generation will let these new ones to see this technology soon in transportation.

References

1.United Nations, U., 2019. Population. United Nations. Available at: https://www.un.org/en/sections/issues depth/population/ [Accessed December 21, 2020].

2. Mantzner, F., 2014. Tax Code of Honor: Congress Must Choose a Clean Energy Future. NRDC. Available at: https://www.nrdc.org/experts/franz matzner/tax code honor congress must choose clean energy future [Accessed December 21, 2020].
3. FCHEA, F.C.H.E.A., Fuel Cell Basics. Fuel Cell & Hydrogen Energy Association. Available at: http://www.fchea.org/fuelcells [Accessed December 21, 2020].
4. EERE, E.E.R.E., Types of Fuel Cells. Energy.gov. Available at: https://www.energy.gov/eere/fuelcells/types fuel cells [Accessed December 21, 2020].
5. CE, C.E., 2013. Types of Fuel Cells. Department of Chemical Engineering and Biotechnology. Available at: https://www.ceb.cam.ac.uk/research/groups/rg eme/Edu/fuelcells/types of fuel cells [Accessed December 21, 2020].
6. Smithsonian Institution, S.I., 2017. A Basic Overview of Fuel Cell Technology. Available at: https://americanhistory.si.edu/fuelcells/basics.htm [Accessed December 21, 2020].
7. BYJUS, B.Y.J.U.S., 2020. Fuel Cell Definition, Working, Types, and Applications of fuel cell. BYJUS. Available at: https://byjus.com/chemistry/fuel cell/ [Accessed December 21, 2020].
8. Fabio Leccese, F.L., 2013. (PDF) Fuel Cells: Technologies and Applications. ResearchGate. Available at: https://www.researchgate.net/publication/261472148_Fuel_Cells_Technologies_and_Applications [Accessed December 21, 2020].
9. Parsitek, P., ENGINE ERING EDUCATION & TRAINING DIVISION. Cussons Technology, pp.1–16.
   
10. Cussons Technology LTD, C.T.L.T.D., 2004. p9040 Fuel Cell Demonstration Unit. Available at: https://www.scribd.com/document/435032693/p9040 Fuel Cell Demonstration Unit [Accessed December 21, 2020].
11. Anon, Solid Oxide Fuel Cell Systems. Solid Oxide Fuel Cell Systems an overview | ScienceDirect Topics. Available at: https://www.sciencedirect.com/topics/engineering/solid oxide fuel cell systems [Accessed December 22, 2020].
12. Matthey, J., The Role of Platinum in Proton Exchange Membrane Fuel Cells. Johnson Matthey Technology Review. Available at: https://www.technology.matthey.com/article/57/4/259 271/ [Accessed December 22, 2020].