06. At what cost?

Outcomes:

> Calculate specific energy values for different fuels.

> Produce a chart to compare the relative amounts of energy released by each fuel.

> Compare the costs of the fuels with the amounts of energy they produce to draw a conclusion about which fuel is the most cost effective.

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The specific energy is a measure of the amount of energy contained per unit mass of a fuel.

It can be calculated using the following formula:

specific energy = energy released from fuel / mass of fuel consumed

As we saw in lesson 05. "Our Nuclear Future", 1 mole (238 g) of uranium can release 2 000 GJ of energy

(1 GJ = 1 000 000 000 J)

For uranium:

specific energy = 2 000 GJ / 238 g = 8.4 GJ g^-1

Activity 1: Calculate the specific energy of anthracite.

The standard amount of energy released by anthracite (one of the purest forms of coal) is 394 kJ mol^-1. Assuming that anthracite is 100% carbon, what is the specific energy for 1 mole of anthracite?

Step 1: calculate the mass of 1 mole of anthracite (pure carbon).

Step 2: calculate the specific energy of anthracite by dividing the amount of energy released by the mass of 1 mole.

Activity 2: Calculate the specific energy of octane.

The standard amount of energy released by octane (petrol, formula C₈H₁₈) is 5471 kJ mol^-1. What is the specific energy for 1 mole of octane?

Step 1: calculate the mass of 1 mole of octane (C₈H₁₈).

Step 2: calculate the specific energy of octane by dividing the amount of energy released by the mass of 1 mole.

Activity 3: Calculate the specific energy of methane.

The standard amount of energy released by methane (natural gas, formula CH₄) is 74.7 kJ mol^-1. What is the specific energy for 1 mole of methane?

Step 1: calculate the mass of 1 mole of methane (CH₄).

Step 2: calculate the specific energy of methane by dividing the amount of energy released by the mass of 1 mole.

Activity 4: Using Google Sheets, plot a suitable chart to compare the relative amounts of energy available per gram from each of the four fuels.

Activity 5: Use the information in the table below to produce a chart that compares the cost to the amount of energy each fuel can produce and therefore draw a conclusion as to which fuel is the most cost effective to use to produce electricity.

Homework: Use the sustainability compass to consider the potential impacts of using uranium in nuclear power stations as a fuel for generating electricity. Present your findings as an infographic.