Clear Science!

A current (simplified) view of the electrical grid shows that the demand for electricity and the amount of electricity generated must essentially match. This is done by ramping power plants up and down as people change how much electricity they want.

Solar power and wind power are not easy to regulate. But we want to be able to make them a large part of the grid, since they’re green. One way to do this is add electrical storage to the grid, which is like being able to put electricity in a box and save it for later. During periods of low demand you fill up the storage and then use it during high demand. A charged battery is an example of “stored” electricity.

We are going to talk about energy for a while. Humanity uses energy a few ways. Sometimes we make electricity first and then power things with that. Other times we burn fuel directly to power an engine or a heater. But let’s step back and ask: where does energy come from in the first place?

Shown above are several primary generation methods for making electricity. What’s actually happening is that we are taking energy from somewhere else and converting it to a more useful form.

Fossil fuels like coal or oil have energy stored in the chemical bonds inside them. When we use fossil fuels, we are claiming that energy. Nuclear generation is similar, but it’s from the atomic bonds within the nuclei of the fuel materials.

If a material is high in a gravitational field it also has energy, and that is what we’re claiming with hydroelectric generation. Water up high is being lowered, and we get the energy liberated by lowering it. Wind generation claims the kinetic energy from blowing wind. Solar generation claims the radiation energy emitted by the sun.

We talked about windmills, and how much air they have blowing through them. (A lot.) The air particles have kinetic energy because of their mass and velocity.

(And by “particles” we mean nitrogen and oxygen molecules, not particulate matter, although that is definitely there too.)

The particles hit the windmill blades or sails and bounce off. Newton’s laws of motion tell us that every action has an equal and opposite reaction, meaning that when the air bounces off, it moves the blade the other way. This way, the blade gets some of the air’s kinetic energy.

PS This is exactly how a fan works, in reverse.

Things that move fast have energy. This is due to their:

• velocity (how fast they are going)
• mass (how much they weigh)

Wind is moving air. It may not seem like it weighs a lot, but think again. Make a windmill 80 meters in diameter, and you can do a little math to estimate the mass of air going through it.

Assuming 30 km/hr average wind speed, it’s about 110,000 pounds of air per second blowing through the windmill blades. That’s a lot of air, and consequently a lot of energy.