According to global investment numbers from 2010, wind power is the green energy industry garnering the most attention from investors [source: Bloomberg New Energy Finance]. New turbine technology, coupled with a more efficient supply chain for producing and installing the sleek towering windmills, makes wind power cost-competitive with conventional energy sources like coal and natural gas [source: Zwilling].
Solar power is another huge driver of global business growth. Decades of research and development in photovoltaic (PV) cell technology has increased the efficiency of solar panels by five times their 1980s strength and new manufacturing techniques promise to lower the production costs of PV cells by 50 percent [source: EERE]. China has leapt headlong into the solar market, producing more than half of the world's solar panels. Since the Chinese government heavily subsidizes its solar industry, the price of solar panels has fallen by two-thirds over the past three years, driving some American solar companies to move production overseas [source: Bradsher].
Geothermal energy holds significant potential for U.S. power generation. An enhanced geothermal system taps underground pockets of superheated rock and uses the Earth's inexhaustible energy to boil water, which then creates steam to power turbines. There are vast fields of potential geothermal sites in the western U.S., but concerns over safety (critics say that tinkering with geological hotspots can trigger earthquakes) require more investment into research and development. Google invested $10.25 million in enhanced geothermal systems technology in 2008 [source: Rubens].
Biomass energy is a broad category that includes any fuel course derived from plants. Ethanol is the most widely known example of biomass energy. In the U.S., it's made from corn, but it can be derived from any plant material, such as sugar cane. While ethanol has run into some strong opposition (too much land and water used to grow corn, too many tax credits for the oil industries,), there is increased investor interest in biodiesel, a cleaner-burning fuel derived from any number of vegetable-based oils, including recycled cooking oil.
Other green energy industries include hydropower, ocean energy captured with tidal generators, landfill gas and hydrogen fuel cells.
The rise in green energy investment has led to the promise of more green-collar jobs. On the next page, we'll see how green energy is fueling job growth.