Energy Conversion Efficiency
Energy Conversion Efficiency is how much of one kind of energy a device turns into the kind you want.
A toaster pulls in electric power and turns some into heat for your bread. But some of that power leaks out as warm air around the sides. Picture a box with bright dots filling the inside. A few dots drift out through the walls as waste. The share of dots that reach the bread, out of all dots that went in, is the efficiency.
Explaining energy conversion efficiency by grade level
When you pour water on a wheel, it spins. Some of the water's push turns the wheel. Some push gets lost as splash and sound. No wheel catches all the push from the water.
Projects that explore energy conversion efficiency
When you burn bioethanol, gasoline, diesel, and kerosene and record the highest water temperature each flame produces, you're measuring how much of the fuel's stored chemical energy actually becomes useful heat. Gasoline heats the water the most, while bioethanol produces the smallest temperature rise of the four. That gap in peak temperature shows that bioethanol converts less of its chemical energy into heat than gasoline, diesel, or kerosene do.
A water wheel generator and a wind turbine generator each receive 15 watts of input power, but they don't produce the same electrical output. You measure the output voltage and current from each, then calculate how much of that input energy each device turns into usable electricity. The comparison reveals which generator converts more of its input into the kind of energy you actually want.