They’ve amassed more wealth than most of us can even comprehend – and they’ve done so by building and running renewable energy empires. From China’s fastest-rising solar superstars to Brazil’s biggest ethanol kingpin, these 8 billionaires and multi-millionaires have a combined net worth that’s well over 10 billion dollars. Their fortunes may fluctuate with the markets, but Elon Musk, Aloys Wobben, Zhu Gongshen and the rest of the eco-entrepreneurs on this list have already proven that there’s big money to be made in clean energy technology.

Photo credit: Wikimedia Commons

1. Aloys Wobben – Enercon

Building his first wind turbine in his backyard, German entrepreneur Aloys Wobben founded wind company Enercon in 1984. Today, as sole owner of the private company, Wobben is the world’s richest green billionaire with a net worth of about $2.3 billion. Enercon produces non-polluting windmills without gears or hydraulics, and has installed more than 17,000 of them in over 30 countries. It’s now the fourth-largest windmill producer in the world, and has begun expanding into hydroelectric plants and seawater desalination projects.

Enercon windmills are distinguishable by their drop-shaped generator housings, and the green rings that are painted at the base of each tower to help them blend into their surroundings. Their gearless, direct-drive mechanisms replace the less reliable gear boxes that are used in most other wind turbines.

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2. Rubens Ometto Silveira Mello – Cosan

The world’s first ethanol billionaire, Rubens Ometto Silveira Mello is worth an estimated $2.7 billion. His company, Cosan, is one of the world’s largest growers and processors of sugarcane, some of which it turns into ethanol. It recently entered a $12 billion joint venture with Shell, which is considered the most significant collaboration between a global oil company and a Brazilian renewable energy company. The collaboration will supply more than 2.2 million liters of ethanol per year to a network of 4,500 domestic fuel stations, and is expected to expand into international markets.

3. Zhu Gongshan – GCL Poly Energy
Photo credit: GCL-Poly Energy Holdings

The third-richest green billionaire in the world behind Aloys Wobben and Rubens Ometto, Zhu Gongshan has earned $1.4 billion of his $1.7 billion overall net worth through his solar power company, GCL Poly Energy. The Hong Kong-based company is one of the world’s largest producers of polysilicon and wafers used to manufacture solar panels. Zhu built his first electricity plant in 1996, and GCL Poly Energy is involved in nearly every method of energy production except for nuclear.

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4. Elon Musk – SolarCity and Tesla Motors

Landing on Forbes’ list of billionaires for the first time in 2012, South African-born American entrepreneur Elon Musk has built his fortune through a number of ventures: Tesla Motors, PayPal and SpaceX, which he co-founded, and SolarCity, where he is chairman. According to Forbes, $1.2 billion of his $2 billion net worth was earned through green enterprises. Musk led the development of the modern era’s first viable electric car, the Tesla Roadster, and is responsible for a business strategy that aims to make electric vehicles affordable to mass-market consumers. As primary investor and chairman of the board of SolarCity, a startup that produces photovoltaic products, Musk continues to work toward his goal of aiding in the fight against global warming.

Photo credit: SolarWorld

5. Frank Asbeck – Solar World

In 2008, SolarWorld chairman and founder Frank Asbeck was worth an estimated $1.6 billion, and the German company’s current market value is about $473.4 million. While Asbeck may no longer be a billionaire, he has still built a considerable fortune from his family-owned business, which manufactures and markets photovoltaic products worldwide. Asbeck founded the company in 1988, and it’s now Germany’s largest solar panel manufacturer, with additional facilities in Sweden, California and Oregon.

Asbeck is known for being a tad eccentric, giving his employees geese for Christmas and installing a bizarre taxidermy fox wall in his office, each of the animals’ eyes set with flashing colored LED lights. “All powered by solar energy,” he says.

Photo credit: Business Week

6. Fan Zhaoxia – Beijing Jingyuntong Technology

Among China’s newest billionaires, Fan Zhaoxia and her husband cofounded Beijing Jingyuntong Technology, which produces photovoltaic equipment for the solar power industry. The company went public in September 2011, raising $400 million, and Fan’s net worth was estimated at about $1 billion late last year. Shares in the company recently dropped when it reported a 91% plunge in its quarterly net profit over last year’s numbers.

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7. Tulsi Tanti – Suzlon Energy

Tulsi Tanti was running a textile factory in Gujarat, India when he became frustrated with the high cost and unpredictable availability of electricity. In 1990, he invested in two Vestas wind turbines, and was so impressed with their performance that he started his own wind power company, Suzlon Energy, five years later. Suzlon Energy is now one of the largest wind turbine manufacturers in the world, and is currently building one of the world’s largest wind parks, with a capacity of 1,000 megawatts. Tanti’s net worth was estimated at $690 million in 2011 by Forbes. He was included among TIME Magazine’s Heroes of the Environment in 2007.

Photo credit: Ecotricity

8. Dale Vince – Ecotricity

Worth an estimated £90 million ($146.4M) thanks to his wind energy empire, Dale Vince is the United Kingdom’s richest eco-entrepreneur. Vince built his empire from a single wind turbine that he used to power the old army truck that he lived in, back in 1995. A self-described ‘hippie dropout’, Vince built increasingly complex wind turbines for friends to take to music festivals until he found himself running his own renewable power company. Vince may still live a modest lifestyle despite the success of his business, sharing a 19th century home with three other families, but he does enjoy one big perk: his own custom electric sports car, the $1.2 million Nemesis.