Ton Hoff, manager of the Energy Research Center of the Netherlands, said it could take decades to make alternatives affordable to the point where they can be used widely, although high oil prices were already stimulating such research.

"If we run out of fossil fuels -- by the time the oil price hits 100 dollars or plus, people will be screaming for alternatives, but whether they will be available at that moment of time -- that's my biggest worry," Hoff said.

"That's why we need to use fossil fuels in a more efficient way to have some more time to develop these alternatives up to a level where the robustness is guaranteed and their price has come down ... This could take decades for some technologies."

Stubbornly high oil prices have renewed worldwide interest in sustainable energy sources, such as solar, wind and biomass as well as biofuels.

But the world currently covers just some two percent of its energy needs with renewables as high costs and mixed policy initiatives hinder a wide-spread usage.

"The high oil price makes people at least think about alternatives ... For us it's a definitely a stimulus to work even harder than before," Hoff said.

LOWERING COSTS

ECN, one of Europe's leading energy research institutes, is working to improve or develop new technologies to boost efficiency and lower the costs of power production from wind, solar and biomass, he said.

ECN researchers are trying to raise the energy conversion efficiency of solar panels to above 20 percent from the current 17 percent, while reducing costs.

"In 10-15 years, I expect that solar energy conversion could be in competition with electricity produced from coal," Hoff said. He believes the Netherlands has the potential to cover a large part of its power needs with solar energy.

ECN is also researching to increase the size of wind power turbines from the 3 megawatt a turbine produces now to 5 or 6 MW. This could be done by raising the height to 100 meters from 70 now and enlarging wings span to 120 meters from 90, he said.

ECN is also part of the $225 million "Global Climate and Energy Project" led by the U.S. University of Stanford and financed by General Electric, Toyota, Schlumberger and ExxonMobil.

The project aims to crack new technologies on fuel cells, which make electricity from hydrogen and emit only water vapor, energy production from biomass and separation and storage of carbon dioxide (CO2). The greenhouse CO2 gas is released when burning fossil fuels and is blamed for global warming.

Under the project, ECN will develop a new type of membrane reactor, which will separate CO2 during the process of producing hydrogen from fossil fuels, Hoff said. The CO2 could later be stored by companies in depleted gas or oil fields.

Hoff and other researchers say a transition to the so-called hydrogen economy could take decades as the cost of building new hydrogen-burning cars and power plants and storing CO2 are huge.

To test hydrogen usage in real life, ECN is in talks with the northern Dutch island of Texel to install hydrogen-based facilities, which would supply electricity to homes and offices.

"The idea is to see the pitfalls, fix them ... and prepare for the future. My hopes are that this will stimulate the usage of this type of new technology because it is extremely important to have it in real life rather than in laboratories," Hoff said.