The Boy Who Harnessed the Wind is a biography of William Kamkwamba, an engineer and inventor from Malwai, a small, poor country in southeast Africa. The biography details William’s efforts, as a self-taught teenager, to put together a windmill that will harness wind power and bring electricity to his impoverished region which had been plagued with drought and famine. The story begins with a prologue, in which William, having built the windmill, is about to perform a test run among a crowd of local villagers. The windmill works, lighting up a small attached blub, much to the crowd’s amazement.
The narrative then backtracks to the late 1990s, where William begins to describe his childhood in a small village called Masitala. He lives there with his siblings and parents, who are subsistence farmers, growing maize, tobacco, and other kinds of crops. William is imaginative and curious about the world. He is split between his tradition, cultural and superstitious beliefs, and science.
William turns thirteen and becomes interested in taking apart and repairing radios. The community has no steady source of electricity and relies on batteries. The Malawian government does little to support farming families like Williams, even as famine and drought spread across Malawi. People were starving, rationing meals, and selling their animals to make ends meet. At a distribution depot, William witnesses how desperate people have become, fighting and cheating one another over food.
As William grows hungrier, his schoolwork suffers. He attends the lowest-ranked school until his family, unfortunately, can no longer pay the tuition. He begins visiting a library where he sits for hours studying the collection of textbooks, with a particular interest in science. He discovers "the building blocks of electricity", including the use of windmills to generate power. William realizes that he could build his own windmill, which would bring electricity to his house and also function as a pump for their well. He goes to local dumps and scavages for materials while people observe, laugh at, and make jokes about him. William is able to use money from the harvest to purchase more materials, with the last of his materials covered by Gilbert, a friend, and son of a local chief.
William builds the windmill with the help of his friends, then builds a tower to house it. Neighbors try to discourage him saying that it would never work. The moment finally arrives and William’s windmill successfully lights up a small blub. As William continues to read the electrical books, he discovers a way to connect the windmill’s electricity into the family home, and eventually sending light to every room in the house through a series of wires, cogs, and switches. He forms a small business, allowing community members to pay for electricity and charge their cell phones. William continues to study at the library and conduct new experiments and ways to improve his electrical system.
The crop yield is poor, and the village, fearing another famine, blames William’s windmill saying that "it was blowing the rain clouds away".
Government officials come to tour the local elementary schools. Dr. Mchazime, a man involved with education in Malawi, hears about William's and goes to see the windmill. He invites William to give a speech at a conference on innovation. He also arranges for William to attend a local boarding school. William delivers his speech and receives a standing ovation. Several influential entrepreneurs and innovators supply William with finances to continue with further research and living expenses. William uses the money not just for experiments, but to equip his village with new roofs and water wells. William is given the opportunity to tour in the United States, visiting New York City, and wind farms in California.
After a series of international conferences, William returns home to repair his windmill, weathered and slightly eaten by termites. He prepares to enter a prestigious high school for African innovators, where he and his classmates discuss how to create “a new kind of Africa…a home of innovation rather than charity (270).”