Fuel Cells as a Source of Energy

Question 1

State what fuel cells use to generate electricity

Answer 1

Chemical energy of hydrogen or other fuels to cleanly and efficiently generate electricity.

Question 2

State whether or not a fuel cell is a type of galvanic cell

Answer 2

Yes.

Question 3

State whether or not fuel cells run down or need recharging

Answer 3

No

Question 4

Electricity is available for as long as fuel cells are supplied with…

Answer 4

Fuel

Question 5

State what the major limitation of primary/secondary cells are

Answer 5

Cell must be discarded or recharged when the reaction reaches equillibrium

Question 6

State an alternative term to describe primary and secondary cells

Answer 6

Galvanic cells

Question 7

State the key difference between a fuel cell and a primary or secondary cell

Answer 7

Reactants do not have to be stored in the fuel cell, but must be continuously supplied from an external source.

Question 8

State what fuel cells transform chemical energy into

Answer 8

Electrical energy

Question 9

Compare and contrast the efficiency of fuel cells with thermal power stations

Answer 9

Fuel cells > Thermal Power Station Energy Efficiency because they directly convert chemical - electrical energy

Question 10

State what a fuel cell employing hydrogen produces

Answer 10

Electricity, water, heat and very small amount of nitrogen dioxide and other emissions

Question 11

State the 2 major parts of a fuel cell

Answer 11

1. Hydrogen gas input

2. Oxygen gas input

Question 12

State what the two gas compartments of a fuel cell are separated by

Answer 12

Two porous electrodes and an electrolyte solution

Question 13

State what the electrode at the hydrogen compartment is termed

Answer 13

Anode

Question 14

State what the electrode at the oxygen compartment is termed

Answer 14

Cathode

Question 15

State what the electrodes within a fuel cell can be classified as

Answer 15

Porous

Question 16

State whether the anode in a fuel cell is positively or negatively charged

Answer 16

Negatively

Question 17

State whether the cathode in a fuel cell is positively or negatively charged

Answer 17

Positively

Question 18

State what process occurs at the cathode of a fuel cell

Answer 18

Reduction

Question 19

State what process occurs at the anode of a fuel cell

Answer 19

Oxidation

Question 20

State how higher voltages can be obtained from fuel cells

Answer 20

Connecting a number of fuel cells in series to form a battery/fuel cell stack

Question 21

State what the electrodes within a fuel cell must be

Answer 21

• porous

- conducting

Question 22

State why electrodes within a fuel cell must be both porous and conducting

Answer 22

Allow the hydrogen and oxygen to come into contact with the ions in the electrolyte and to allow the redox half reactions to occur at their surface.

Question 23

State what the size of the current that can be drawn from a fuel cell depends upon

Answer 23

The surface area of the electrodes

Question 24

State why catalysts are employed within fuel cells

Answer 24

To increase the rate of reaction and the current that can be produced from a cell

Question 25

Outline the purpose of porous electrodes

Answer 25

Allow reactants to diffuse through them to react with ions in the electrolyte

Question 26

State what fuel most fuel cells are designed to use

Answer 26

Hydrogen

Question 27

State what a fuel cell using hydrogen as a fuel source can be described as

Answer 27

A 'zero-emission' device

Question 28

State whether the production of hydrogen can result in the production of significant levels of greenhouse gases/pollutants

Answer 28

Yes. Especially if produced via steam reforming (of natural gas, oil or coil)

Question 29

State 2 practical methods of harvesting hydrogen gas sustainably

Answer 29

1. Using electrical energy to convert water to hydrogen (electricity can be generated from renewable sources such as solar-power farms and wind farms) 2. Collecting biogas from landfill sites and converting the methane to hydrogen via steam reforming

Question 30

State what the widespread adoption of hydrogen as a primary fuel source would require

Answer 30

Massive expenditure on infrastructure

Question 31

State the major reasons supporting challenges associated with hydrogen gas storage

Answer 31

Hydrogen is a gas at room temperature

Question 32

State what temperature liquid hydrogen generally boils at

Answer 32

Extremely low temperatures

Question 33

State whether a large or small quantity of energy is needed to liquify hydrogen

Answer 33

Large quantity

Question 34

State what the requirements of a hydrogen gas tank are

Answer 34

Good insulation

Question 35

State whether or not hydrogen gas must be stored in high pressure tanks

Answer 35

Yes. Hydrogen gas must be stored in high pressure tanks,

Question 36

State why hydrogen gas pressure tanks must be so large to effectively replace a standard hydrocarbon fuel tank

Answer 36

High pressure hydrogen storage tanks need to be large to meet the energy availability within smaller hydrocarbon fuel tanks

Question 37

Compare and contrast the energy availability of liquid hydrogen and a liquid hydrocarbon (e.g. petrol)

Answer 37

Petrol has a energy availability of four times greater

Question 38

State what hydrogen can absorb to

Answer 38

The surface of materials such as metal hydrides, either as hydrogen molecules or as hydrogen atoms

Question 39

State whether or not hydrogen can dissociate

Answer 39

Yes

Question 40

State what hydrogen would dissociate and become absorbed into

Answer 40

Lattice structure of some solid materials

Question 41

State whether or not hydrogen can react reversibly with a range of different chemicals

Answer 41

Yes.

Question 42

Provide reasons supporting the levels of danger associated with hydrogen

Answer 42

Hydrogen burns more readily and a flame/spark will ignite almost any combination of hydrogen and air

Question 43

State what the low density of hydrogen means for its levels of flammability

Answer 43

Low density means that hydrogen can rise rapidly and quickly disperse in ventilated areas - often without ignition

Question 44

Compare and contrast danger associated with a fire in a petrol powered vehicle vs a hydrogen powered vehicle

Answer 44

Hydrogen-powered vehicle is less dangerous due to low density of hydrogen gas

Question 45

Compare and contrast the fuel efficiency and emissions of fuel cells with internal combustion engines

Answer 45

Higher fuel efficiency and lower emissions overall from fuel cells

Question 46

State what fuel cells convert chemical energy directly into

Answer 46

Electrical energy

Question 47

State why the electrical energy conversion in fuel cells is more efficient than the series of energy conversions that take place in power stations

Answer 47

Fuel cells: chemical - electrical energy | Power stations: chemical - heat - mechanical - electrical energy

Question 48

State what hydrogen fuel cells produce as by products

Answer 48

Water and heat

Question 49

State whether any greenhouse gases are released from hydrogen fuel cells

Answer 49

No greenhouse gases are released

Question 50

State for how long fuel cells will generate electricity

Answer 50

As long as the fuel is supplied

Question 51

State whether or not fuel cells can use a variety of fuels

Answer 51

Yes

Question 52

State whether or not fuel cells are expensive.

Answer 52

Yes. Still a developing technology.

Question 53

State what alterations will be required for fuel cells to be used extensively for transport

Answer 53

Extensive network of hydrogen filling stations will need to be established

Question 54

State a possible disadvantage of fuel cells generation of DC current

Answer 54

Many electrical appliances in the home require AC current and an inverter is thus required to change DC to AC at the appropriate voltage.

Question 55

Identify a possible disadvantage associated with the sourcing of hydrogen for fuel cells

Answer 55

Mainly sourced from fossil fuels - which involves energy losses and generates greenhouse gases

Question 56

State the major disadvantage of using hydrogen fuel in fuel cells

Answer 56

Safety associated with storage of fuel

Question 57

Compare and contrast the function of primary/secondary cell with fuel cells

Answer 57

Primary/secondary cells - source of portable electrical energy Fuel cells - continuous source of high electric current for portable/fixed applications

Question 58

Compare and contrasts the life of the reactants within primary/secondary cells and fuel cells

Answer 58

Primary/secondary cells - reactants in primary & secondary cells are contained and can thus be depleted Fuel cells - air/oxygen are supplied continuously

Question 59

Compare and contrast the site of oxidation in primary/secondary cells and fuel cells

Answer 59

Primary/secondary cells - negatively charged anode | Fuel cells - negatively charged anode

Question 60

Compare and contrast the site of reduction in primary/secondary cells and fuel cells

Answer 60

Primary/secondary cells - positively charged cathode | Fuel cells - positively charged cathode

Question 61

Compare and contrast the porous region of primary/secondary cells and fuel cells

Answer 61

Primary/secondary cells - salt bridge | Fuel cells - porous electrodes

Question 62

Compare and contrast the position of the electrolyte for primary/secondary cells and fuel cells

Answer 62

Primary/secondary cells - salt bridge (carries charge between electrodes) Fuel cells - between two porous electrodes (carries charge between electrodes)

Question 63

Compare and contrast the energy transformations of primary/secondary cells and fuel cells

Answer 63

Chemical - electrical energy

Question 64

Compare and contrast the energy efficiency of primary/secondary cells and fuel cells

Answer 64

Primary/secondary cells - 60-90% efficient | Fuel cells - 40-60% efficient