They turn the generator on.

That generator creates electricity.

With such basic principles, building the turbines should have been easy.

But as engineers soon discovered, it took a complex mix of strength and aerodynamics.

The blades of a wind turbine may look simple, but they've been perfectly designed to harness as much power from the wind as possible.

First, to extract the maximum energy from the wind, the blades have to be at the right angle known as pitch.

Getting the pitch right is crucial, as Professor Lawrence Coats demonstrates.

Hey, we have a model wind turbine, the typical three blades, these Airil flat in a real turbine you'd find as you go along the length they twist to try and keep the angle of Attackers close to optimum as possible.

What are aiming to show is the effect that the picture of the blades that's that orientation can have on the actual power you get out.

These are 45 degrees.

Let me just say about the voltages.

We're getting a reasonable amount of power out there now.

The professor reduces the pitch from 45 degrees to 22 a half, so the blade should catch more wind and generate more power.

So now that it's moving, the angle of attack is actually more close to optimal, and we're now getting significantly more power.

In fact, reducing the pitch by 22 degrees doubles the power output.

Optimal pitch also changes with air flow.

The pitch of most wind turbines is adjusted automatically, with wind speed increasing or decreasing the angle to extract the maximum possible energy from the air.

Working hard exposed to the elements 24 7 the blades experience huge amounts of stress, creating strong enough blades is demanding even with high tech materials.

As turbine engineer Craig Siddons explains, so most commonly later made off glass fibre on the poxy solution.

So what we see up top here is the fiberglass fiber itself that's no impregnated with epoxy on this.

This green color here is the impregnated fiber.

So this this this appear is obviously not impregnated.

It's quite nasty to touch, so I had to put my gloves on to touch it can get into his skin into your pores, and it's sort of it's quiet Nazi stuff.

So the reason we used glass fibre epoxy is cause for the strength that gives is from that much weight, so we can build blades that are very, very long extracts.

Much anything is possible.

For three decades ago, turbines began to spring up in remote, windy locations worldwide and started generating power.

As energy consultant Simon Gray explains.

Behind me here today, we have the scrubby sounds wind farm.

This is one of the early wind farms.

One first injured Facts Gulf Shore So typically on the daylight today, he seems fairly windy.

We're talking about this particular ray here, generating enough for about 40,000 homes overall, if we averages out across the year, I would say offshore wind on onshore wind is generating some 15 to 20% of the U.

K's energy.

As materials have become lighter and stronger, turbines have grown larger.

So if you imagine a building the size of Off the Gherkin in London, he's about the size of towers.

And if you think that the diamonds of the blades about the same size of slightly larger in the London eye, a single rotation of the largest turbine and power a house for a day.

But if they're not turning their worthless wind turbines on cheek.

To make them pay, engineers have to kick them working constantly.

Any downtime is extremely costly.

But only decades after the first wind farms were built, engineers worldwide discovered they had underestimated the power of Mother Nature.

Engineers are still finding teething problems with their original designs, and some of those problems are potentially huge, most concerning these giants all over the planet.

We're showing unexpected signs of aging caused by particles in the wind.

You might expect the giant turbine blades could easily cope with a bit of dust in Maine.

But being exposed 24 7 365 days a year takes its toll.

Believe it or not, when engineers first installed winter lines, they thought they'd be pretty much maintenance free.

But they are wrong.

Inspections revealed that in many cases, the front of the blade, the leading edge, was suffering catastrophic damage.

To keep the power flowing around the world.

A solution is needed and fast.

Any damage to the blades leading edge means that it doesn't cut the air so smoothly, and that means the blade doesn't turn as quickly.

Slower blade needs less electricity generated.

So the leading edge here is very sensitive.

In terms of dynamics.

Just a small defect can cause a defect in the lift that goes right the way down the blade so it can have a huge impact on performance of the blade.

The problem comes down to the speed at which the turbines spin.

It might look slow, but size is deceptive.

The blades are spinning.

That's up 280 miles per hour.

That's almost 290 kilometers per hour.

At that speed.

Anything that hits the blades could cause massive damage, something these turbines off the coast of England were witnessing firsthand.

When you don't remember, the middle of the southern North Sea is a fairly hostile environments.

Effectively, we have sea spray.

We have salt water.

We have wind.

All of these combined to cause major erosion on all sorts of structure with the oil and gas, or whether the offshore wind and particularly the leading edge of the blade is particularly prone to this.

Given that it has that proximity to salt water on dhe with energy, Way might call it thin air, but the sky is full of impurities from dust toe lumps of frozen water.

A simple example helps demonstrate what is happening on a large scale.

Imagine that you're going to send drop of water, possibly even a small hailstone, and you're moving along with the flow and you approaching the very front or so called leading edge of this plate on in order to go over the top underneath, you have to have a force applied to move you.

But there's no time for that because the turbine blade is hurtling toward you 250 miles an hour.

So you hit it so it's only one hailstone.

It's not going to make much difference, but there's hundreds off them on.

After about two or three years, these may create a larger whole wind, will catch that and start to de laminate.

The turbine blades with blades so precisely shaped delamination or splitting open of the material layers causes massive interruptions, toe airflow and loss of power.

It's amazing that these tiny pieces of dirt can cause such huge problems for these giant machines.

Renewable energy is the future, so engineers are working hard on solutions, from long term, tougher materials to short term fixes.