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Saving energy

Energy and power · level 3, lesson 6 of 6

A question to start

If energy is never destroyed, why do people talk about "saving energy"? And why would a family on Mars care about it even more than a family on Earth?

The idea

"Saving energy" means getting the job done using less of the energy we have to make or buy: electricity, fuel, the charge in a battery. Every bit of it ends up as spread-out heat in the end; saving means wasting less on the way.

Ways to save energy at home:

  • Keep heat in. Wrap the house in insulation, shut doors and windows in winter, wear a jumper.
  • Use machines that waste less. LED lamps, good fridges, well-made motors.
  • Switch things off when nobody is using them.
  • Use waste heat. Some buildings use the warm air going out to heat the cold air coming in.
leaky: needs lots of heatinginsulated: needs little

On Mars, saving energy matters even more:

  • There is no grid to buy power from. Every watt must come from panels or a power unit that was flown from Earth at great cost, or built on Mars.
  • It is far colder outside, so heat leaks out faster. Good insulation, such as a thick layer of soil over the roof, saves a huge amount of heating.
  • During a dust storm, solar power can drop for weeks. A home that wastes little can last longer on its batteries.

Worked examples

1. Insulating a loft. A house that loses 100 units of heat a day through its roof might lose only 30 after the loft is insulated. The heating has to make 70 fewer units.

2. Lights in a greenhouse. Swapping old lamps for LEDs can give plants the same light for much less energy, and less waste heat.

Try it

  1. What does "saving energy" really mean, if energy is never destroyed?
  2. Give three ways to save energy at home.
  3. Why does a home on Mars lose heat faster than one on Earth?
  4. How could the heat from computers be useful in a Mars habitat?
Answers
  1. Doing the same jobs while making or buying less energy, by wasting less.
  2. For example: insulation, LED lamps, switching things off, closing doors in winter.
  3. It is much colder outside, so heat flows out faster.
  4. It helps to warm the habitat, so the heaters need to do less.

Common mistake

"Switching off a light saves a little bit of energy for later." Switching off does not store anything up; it just stops the power station (or battery) having to supply that energy at all.

Where it leads