Most renewable sources are abundant, practically inexhaustible and far more climate friendly than fossil fuels. Some companies making equipment to harness these energies are growing rapidly.

Last month, experts advising the United Nations said renewable sources could deliver nearly 80 percent of world’s total energy demand by the middle of the century. That report, by the Intergovernmental Panel on Climate Change — the most authoritative body of experts, scientists and engineers specialized in climate change — was a welcome signal for an industry that has faltered in previous decades after government subsidies dried up and lower-cost fossil fuels made their technologies uncompetitive.

The report “is a big thumbs up for an industry that’s making huge advances in lowering costs and improving efficiency,” said Maja Wessels, global head of government affairs for First Solar, one of the largest makers of solar panels. “The experts have said that reaching high renewables targets will become very achievable.”

She said that the report should serve as basis for governments and lenders like the World Bank to plan investment in energy systems and infrastructure.

Governments staking out a low-carbon future also welcomed the findings.

Charles Hendry, the British minister for energy and climate change, said the report “makes it completely clear that this is a massively growing area” that could deliver “a turnaround moment for many parts of the economy.”

Even so, some financiers and environmental groups said the report underplayed the potential for renewable energy. The panel “wasn’t aggressive enough and the data were two years old,” said Gerard Reid, an analyst at Jefferies, an investment bank. “For solar panels, and offshore wind and concentrating solar power, we can get the costs down even quicker.”

WWF, an environmental group, emphasized that it had developed plans for generating 100 percent renewable energy by 2050.

Ottmar Edenhofer, co-chairman of the climate panel that wrote the report, said the findings were realistic. “Under no circumstances can we afford to omit or neglect renewables,” Mr. Edenhofer said by telephone. “But we must remember that there is more than one way to achieve a low greenhouse gas economy.” He was referring to alternatives to renewable sources like nuclear power and technologies under development to limit the damage of fossil fuel use by capturing and storing carbon dioxide before it reaches the atmosphere.

Some of the renewable sources with the greatest potential to deliver large amounts of energy, like certain kinds of solar power, remain expensive compared with burning fossil fuels, he said. And integrating a wide variety of renewable sources into existing power grids would be a huge technical and financial challenge, he added.

That caution was echoed by separate report released on May 24 by the International Energy Agency. While the agency found that biomass, geothermal and hydropower provide a steady stream of power and pose no greater challenge than conventional power to integrate into grids, other renewable sources — wind, solar, wave and tidal energy — fluctuate with the weather and are often in places that lack grids.

“When shares of variable renewables amount to just a few percent, a philosophy of ‘connect and manage’ will usually suffice,” said Nobua Tanaka, executive director of the I.E.A. Greater use of renewable sources means that “this will need to change,” he said.

A summary of the climate panel’s report was published on May 9, after 194 governments agreed to the text. The report was based on a comparison of 164 evaluations of the technology and provided the most comprehensive analysis to date of trends and perspectives for renewable energy. The panel was expected to publish a full report of more than 900 pages by mid-June, once scientists have completed final checks.

The report found that six sources — bioenergy, wind, solar, geothermal energy, hydropower and ocean energy — currently accounted for 13 percent of global energy supply. In one of the least optimistic outlooks for the sector examined by the panel, the world would generate 15 percent of its energy needs from those same six sources by 2050. But in one of the most optimistic projections, the world could generate 43 percent of its energy needs from those six sources by 2030 and 77 percent by 2050.

Renewable energy also would create jobs and help accelerate access to energy for 1.4 billion people without electricity.

Article source: http://www.nytimes.com/2011/06/03/business/energy-environment/03iht-RBOG-Kanter03.html?partner=rss&emc=rss