You cannot make energy, only change it
One of the firmest rules in science is that energy can never be created or destroyed, only changed from one form into another. In the 1840s an English brewer's son, James Joule, proved it with careful experiments, such as using a falling weight to turn paddles in a tank of water and measuring the tiny rise in temperature. The unit of energy, the JOULE, is named after him.
A roller coaster shows the idea. Hauled to the top of the first hill, the car stores POTENTIAL energy; as it plunges down, that turns into KINETIC energy, the energy of movement, and back again on the next climb. Food stores CHEMICAL energy, a battery stores it too, and burning FUEL turns it into HEAT, or THERMAL energy.
A mountain full of water
Electricity is hard to store in large amounts, so power stations must make exactly as much as people are using, second by second. When millions of kettles go on at once during a big television event, as our hot drinks page describes, demand jumps within minutes. One answer is hidden inside a mountain in Snowdonia in Wales. At Dinorwig power station, water is pumped up to a high lake when electricity is cheap and plentiful. When a surge comes, the water is released down tunnels through TURBINE generators deep inside the mountain. The station, opened in 1984 inside a disused slate quarry, has one of the largest man-made caverns in Europe for its machinery, and with its turbines already spinning the station can reach full POWER in a matter of seconds.
Sunshine, wind, hot rocks and atoms
More SUNLIGHT reaches the Earth in about an hour than all the world's people use in energy in a year. A SOLAR PANEL turns a small share of it straight into ELECTRIC current. WIND turbines now stand far out at sea, where the wind is steadier, with blades longer than a football pitch. HYDRO power uses falling water, and China's Three Gorges Dam is the biggest power station on Earth; and Iceland, sitting on volcanic rock, heats most of its homes with GEOTHERMAL heat from underground. BIOMASS power burns plants and wood, which regrow.
FOSSIL fuels, coal, oil and gas, are the remains of plants and tiny sea creatures buried for millions of years. They store a lot of energy, but burning them releases carbon dioxide that warms the climate, so countries are switching to RENEWABLE sources that will not run out.
NUCLEAR power stations split atoms of uranium to release heat, which boils water to spin turbines. A single uranium fuel pellet, about the size of a fingertip, can release roughly as much energy as a tonne of coal. The WATT, the unit of POWER, measures how fast energy is used, and a power station's OUTPUT is counted in millions of them. The switch to cleaner energy also changes transport, as our electric cars page explains. Fusion, the joining of atoms that powers the Sun, releases even more; in 2022 a laboratory in California got more energy out of a fusion reaction than its lasers put in, for the first time, though a working fusion power station is still a long way off.