Lesson 01 · 4 min · 6 things to do
Nothing is made, only moved
Trace energy through a conversion and account for what is lost.
A power station burns coal and sends electricity to your house. Where did the energy come from?
- Yes.Coal is a battery charged by ancient photosynthesis. Nothing in the station creates energy — it releases what was already there and moves it into a different form.
- Not quite.Nothing makes energy. A power station is a converter, and every converter starts with something that already had it.
- Not quite.The grid is the delivery, not the source. It carries energy and holds almost none.
Energy is never created or destroyed, only moved and converted. Every argument about energy is really an argument about conversions and losses.
Follow 100 units of energy in coal, all the way to a room. Slide through the steps.
In the coalAfter burningAfter the turbineAt the socketStill available100 unitsLost as heat so far0 unitsIn the coal100 units of chemical energy, sitting in the fuel.
- Still available90 units · 90%
- Lost as heat so far10 units · 10%
After burningHeat in steam. Some has already gone up the chimney.
- Still available38 units · 38%
- Lost as heat so far62 units · 62%
After the turbineAbout 38 units are now electricity. The rest left as warm water and warm air.
- Still available35 units · 35%
- Lost as heat so far65 units · 65%
At the socketAbout 35 arrive. The wires took a few per cent on the way.
Nearly two thirds was lost before it reached the room. Where did it go?
- Yes.Nothing was destroyed. It became heat spread so thinly that no machine can do anything with it, which is the one direction energy conversions always drift in.
- Not quite.Inefficiency does not destroy anything. It describes how much ended up as heat you cannot use.
- Not quite.A large share of that loss is a physical limit on any heat engine, not a fixable mistake. Better engineering moves it a few points.
Move the control to see what changes.
An electric motor turns electricity into movement at about 90% efficiency. A petrol engine manages about 30%. What does that comparison tell you?
- Yes.If the electricity came from a coal station at 38%, the chain to the wheels is closer to 34%. Efficiency is a property of a chain, and the honest version names both ends of it.
- Not quite.At the motor, yes. The question is what had to happen upstream to deliver that electricity.
- Not quite.It tells you a great deal — as long as the boundary is stated. Comparisons with different boundaries are the most common trick in energy arguments.
Which of these are sources of energy, and which are carriers that must be filled from somewhere?
Sunlight.
Electricity.
Hydrogen.
Wind.
A charged battery.
Yes.Carriers are enormously useful and they are never free energy. Every carrier has to be filled by a source, at a loss — which is why 'we will run it on hydrogen' is a question about electricity, not an answer.A power station converts fuel to electricity at 38% efficiency. To deliver 38 units of electricity, how many units of fuel energy must go in?
unitsYes.The efficiency is the ratio, so the fuel is always the bigger number. This is why saving one unit at the socket saves nearly three at the mine — the biggest lever in the whole chain is at the far end.Why is reducing demand such a powerful move in an energy system?
- Yes.The saving multiplies backwards through the chain. It is the least visible intervention in energy policy and arithmetically among the largest.
- Not quite.Often true, and it is a separate argument about cost. The multiplication happens whatever the price.
- Not quite.Supply is built and chosen all the time. The force of this point is in the arithmetic, not in what is controllable.
Lesson complete
Nothing makes energy. Everything converts it, and every conversion leaks heat.
Next: The grid balances every second →