Challenge

Week 2 Challenge

PPraveen Kumar E S6 Feb 2022

Question 1:
Compare four different types of fuel cells and state their applications.

An electrical current is produced via redox reactions occurring on the electrodes of the fuel cell. The most common fuel cell is the hydrogen fuel cell.
On the anode, hydrogen molecules, which are fed to the anode from an external supply, dissociate to protons and electrons on catalytic material deposited on the anode (expensive noble metal Pt) and protons travel towards the cathode through the electrolyte, which in the most common cases is a polymer electrolyte membrane (PEMFC). The electrons travel in the external circuit, thus creating a current, eventually reaching the cathode. At the cathode protons, oxygen atoms from dissociated oxygen molecules and electrons combine to form water.
The cathode also requests a suitable catalyst for the reactions there (oxygen reduction reaction, ORR). O2 (air) is supplied to the cathode from an external supply. Thus, a fuel cell generates a current by using energy-rich hydrogen molecules, i.e., converts chemical energy to electricity. It should be noted that it is the fuel cell together with its fuel tank and oxygen supply that constitutes an energy storage system, not the fuel cell alone.

Types of Fuel Cell	Advantages	Disadvantages	Operating Temperature, Stack Size , Efficiency.	Application
Proton Exchange Membrane Fuel Cell (PEMFC)	Solid Electrolyte eliminating possibility of corrosion, no replishment needed due to it being solid. Works well at low temperature too in countries like canada and sweden. Quick startup time irrespective of condition.	Expensive Catalyst(biggest cost factor in FC production) Sensitive to fuel impurities such as hydrogen supplied must be as pure as possible.	<120 C <1-100 Kw 60% direct H2, 40% reformed fuel.	Suitable for the automotive because: PEMFCs offer high power density, low weight and Volume. Operate at low temperature (around 80C) and thus quick startup time, results in less wear and tear and it increased the durability.
Solid oxide Fuel Cell (SOFC)	High efficiency Can accept various fuels like methanol, ethanol, methane etc. Solid electrolyte	Corrosion and breakdown of cell components at high temperatures. Required Significant thermal Shielding. Long Startup time have to wait until a decent amount of power is generated. Can produce CO2 if taken the fuels like ethanol, methanol, methane due to the presence of Carbon.	500C-1000C 1Kw-2Mw 60%	Suitable for the stationary power generation and utility because: Operate at extremely high temperatures ( around 1000C) and thus slow startup. These properties already make it unsuitable for the automotive. Produces natural heat which can be recirculated and it used to heat homes in cold climates. High temperature reduces need for the catalyst and reformer for the fuels and hence reducing system cost
Alkaline Fuel Cell (AFC)	Made up of various materials, allowing flexibility in minimizing cost. Low startup time.	Sensitive to CO2 can poison the AFC. Liquid electrolyte maintenance needed to ensure it is at the right level. Electrolyte Conductivity is not the best	<100C 1-100Kw 60%	Electrical power for onboard systems in spacecrafts.
Direct Methanol Fuel Cell (DMFC)	Low cost fuel. Can Operate at low temperatures. Higher energy density than hydrigen. Easier to store and transport using current infrastructure due to its liquid form.	Contains Carbon so it emits CO2 Reaction of methanol with oxygen is much slower, so response is sluggish. Methanol crossover from anode to cathode easily, reducing the cell Voltage.	60C-90C <1-100W 40%	Due to methanol crossover,power produced is limited. However, DMFCs Compactness allows high power density, Which can be supplied in small amounts for a long time. Ideal for smaller vehicles like forklifts, auxiliary systems in automobiles, consumer electronics like laptops and cameras.

Question 2:

Using a plot with energy density and power density on the X and Y axis, arrange various battery types like lithium ion, lead acid, Nickel Cadmium, Ultracapacitor, fuel cell.

Energy density:

If a system has a high energy density then it is able to store a lot of energy in a small amount of mass. A high energy density does not necessarily mean a high power density. An object with a high energy density, but low power density can perform work for a relatively long period of time.An example of this type of energy storage is a mobile phone.
Its power will last most of the day, but to recharge the device, it must be connected to another power source for an hour or more.

Power density:

If a system has a high power density, than it can output large amounts of energy based on its mass. For example, a tiny Capacitor may have the same power output as a large battery.
However, since the capacitor is so much smaller, it has a higher power density. Since they release their energy quickly, high power density systems can also recharge quickly.
An example application of this type of energy storage is a camera flash. It has to be small enough to fit inside the camera (or cell phone) but have a high enough power output to light up the subject of your photo. this makes a system with a high power density ideal.

Thus from the above graph we found that,

Lithium ion, lead acid, Nickel Cadmium batteries have a low power density and the moderate energy density.
Ultra Capacitor or Super Capacitor have a moderate power density and moderate energy density.
Fuel cell have low power density and the high energy density.

Week 2 Challenge

Ship work like this
in your own course.

Talk to a career counsellor

Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.