7 a When the energy input to a gas-fi red power station is
1000 MJ, the electrical energy output is 300 MJ. What
is the effi ciency of the power station in changing the
energy in gas into electrical energy?
b What form does the 700 MJ of ‘lost’ energy take?
c What is the fate of the ‘lost’ energy?
a. Efficiency can be calculated using the formula Efficiency = (Useful energy output / Total energy input) x 100%. In this case, the useful energy output is 300 MJ and the total energy input is 1000 MJ.
Efficiency = (300 / 1000) x 100% = 30%
Therefore, the efficiency of the power station in converting the energy in gas into electrical energy is 30%.
b. The 700 MJ of 'lost' energy likely takes the form of waste heat. In any energy conversion process, some of the energy input is inevitably lost as waste heat.
c. The fate of the 'lost' energy in the form of waste heat is typically dissipated into the surrounding environment. This waste heat can contribute to environmental issues such as global warming by adding to the overall heat in the atmosphere.