Solar can provide 22 per cent of power: IEA

Solar power currently accounts for 0.5 percent of world supply, but the IEA said this needed to grow in order to cut greenhouse gas emissions and dependence on fossil fuels.

"Without decisive action, energy-related emissions of CO2 will more than double by 2050 and increased oil demand will heighten concerns over the security of supplies," an IEA report said.

Leading solar producers like Spain and Germany pay solar plants "feed-in tariffs," a subsidy designed to gradually cut the technology's costs to the level of conventional power, a condition known as "grid parity."

The IEA, adviser to industrialized nations on energy policy, predicts roof-mounted photovoltaic PV panels will not reach grid parity until 2020, and utility-scale PV not until 2030.

Concentrated solar power CSP can achieve grid parity at times of peak demand by 2020 in sunny places, the IEA added in a series of "road maps" unveiled at a conference hosted by the Spanish government in the eastern city of Valencia.

The German and Spanish governments have already announced that they will cut back on feed-in tariffs, which has sent solar power stocks tumbling across the world.

"The problem is to give a clearer predictable future, a gradual decline in subsidies," IEA Executive Director Nobuo Tanaka said in an interview.

"Without decline you cannot give an incentive for the industry to innovate. Just providing subsidies doesn't make sense."

PV technology directly converts the sun's rays into electricity, whereas CSP plants collect sunshine to boil water and drive an electricity generator.

Both technologies can produce 9,000 terawatt-hours of electricity by 2050, or almost a quarter of global demand, which the IEA estimates will cut carbon emissions by almost 6 billion tonnes.

The IEA estimates that solar power output in 2010 will be 37 TWh, almost all of it from PV plants, which it expects to account for 5 percent of global electricity by 2030.

Few CSP plants have been built yet, but they can produce much more than PV installations. The IEA predicts they will account for 5 percent of electricity consumption by 2020 in parts of Central Asia, India, Latin America and the United States.

Between them, the IEA says CSP and PV can provide 2.3 percent of the world's power by 2020, rising to 8.8 percent in 2030, when grid parity kicks in.

By 2050, PV and CSP can each provide 11 percent of global electricity, the IEA added.