Secondary Energy
Energy converted from primary sources into useful forms like electricity or refined fuel.
Formula
Secondary Energy Efficiency = Secondary Energy Output ÷ Primary Energy Input × 100%
Real World
A conventional coal-fired power station like the UK's former Drax coal units converted primary coal energy into electricity at only around 35% efficiency — meaning 65% of the original energy was lost as waste heat — highlighting why the shift to combined-cycle gas turbines (55%+ efficiency) significantly reduces fuel consumption.
Exam Focus
When comparing energy sources, address conversion losses between primary and secondary energy to demonstrate understanding of real-world efficiency.
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