Laddermill facts for kids

A laddermill kite system is a special type of airborne wind turbine. It uses a long string or loop of many power kites. Think of it like a giant ladder made of kites!

These kites are launched into the sky. Their strong lift pulls the "ladder" upwards until it's fully unrolled. It can reach very high, sometimes over 9,000 meters (about 30,000 feet)! The idea is to capture strong winds high up in the air. A company called kPower, Inc. even built and flew a laddermill kite system.

How Laddermills Work

Laddermills are designed to turn wind energy from high in the sky into electricity on the ground. There are two main ways they can do this:

Pulling a String

• Imagine a long string with kites attached. The kites pull this string upwards with great force. This pulling force is then used to power an electric generator, which makes electricity.
• When the string reaches its highest point, the kites change their shape. This makes them pull less. Then, the string is wound back down. The electric generator can even act like a motor to help rewind it.
• Once the string is fully rewound, the kites change their shape again to catch the wind and start the next energy-making cycle.

Rotating a Loop

• Another way is to use an endless loop of wire with kites on it. Kites on one side of the loop catch the wind and pull hard.
• Kites on the other side of the loop change their shape so they don't pull as much. This difference in pull makes the whole loop rotate.
• As the loop spins, it turns an electric generator, creating electricity.

Who Invented the Laddermill?

A "rotating loop" laddermill project was designed by a Dutch ex-astronaut and physicist named Wubbo Ockels. He believed that the air high above us holds a huge amount of energy.

He said that the LadderMill was created to use this energy from high altitudes (up to 10 kilometers or about 6 miles high). The goal was to turn this wind energy into electricity in a way that is good for the environment and not too expensive.

Laddermill Timeline

• The idea for the laddermill was first shared on April 3, 1977.
• On September 21, 1979, an inventor named Douglas Selsam officially recorded his idea for a similar system. He called it a HAWP system, which used kites to lift an endless chain of airfoils (like wings).
• Wubbo Ockels later described his LadderMill device in a patent from 1997, which was a type of system similar to what Douglas Selsam had thought of earlier.