Sun Microsystems co-founder and notable Internet technologist Bill Joy has decided that green tech is a far more worthy investment than Internet companies.

Joy gave a talk on why he is exploring a wide range of green technologies as a partner at venture capital firm Kleiner, Perkins, Caufield AND Byers. He spoke at the Lux Research conference on nanotechnology where he also predicted major changes in transportation industry and solar energy.

Joy, credited with inventing several Internet technologies as a co-founder of Sun Microsystems, joined the high-profile Silicon Valley venture capital firm in 2005.

By contrast, the urgent problem of global warming means that energy and green tech investments represent a great opportunity for innovation, he said.

In an interview after his presentation, Joy said that energy and green tech makes for appealing venture investments because there is a large technology component and the markets are huge.

He said it's more likely that these electric cars will take hold in Europe before the United States because Americans drive longer distances, have heavier cars and drive more trucks as passenger cars.

In solar energy, his long-term bet is on photovoltaicsmaterials to convert light into electricity.

Solar panels right now require hefty upfront investment, typically for homeowners who don't have as many financing options as large organisations.

Although the efficiency of panels is improving, companies are pursuing solar technologies, such as solar thermal and solar concentrators, which can be more cost-effective.

Kleiner Perkins, in fact, has invested in both solar thermal and photovoltaics. But Joy sees photovoltaics winning out in the end.

Cells made from silicon the most widely used material for solar panels have an efficiency of about 20 percent. Joy predicts that advances in materials can boost the efficiency while keeping costs low.

"It's much easier in the long run to get higher efficiency from photovoltaics. The cost is prohibitive today because we're making high- efficiency photovoltaics out of high-purity crystalline silicon which is very expensive to make," he said. "That's not inherent in physics. Physics will win ultimately, I think