Potential of solar power hailed
Solar power could outstrip fossil fuels, other renewables and nuclear to be the biggest source of electricity by mid-century, the International Energy Agency has said.
Solar technologies could generate more than a quarter of the world's electricity, with 16% from photovoltaic (PV) panels and a further 11% from solar thermal electricity systems, which collect the sun's rays to heat fluids that drive electricity turbines.
The two technologies could save six billion tonnes of carbon dioxide emissions a year by 2050, more than all of the emissions currently generated by the US energy system, or almost all of the emissions of the world's transport sector, the IEA said.
But to achieve the large scale deployment of solar power, governments need to set clear, credible and consistent signals about solar, including long term targets for PV deployment and predictable incentives, the IEA said.
A "roadmap" report from the IEA on solar PV said that since 2010, the world has installed more of the technology than in the previous four decades, and that the price of PV systems had fallen by two-thirds in most markets in just six years.
A separate roadmap on solar thermal electricity (STE) said the systems had the benefit of being able to store thermal energy to produce electricity later, for example in the peak evening hours after the sun had set.
Deployment of STE systems was dwarfed by solar PV, with just four gigawatts installed worldwide, compared to 150 gigawatts of photovoltaic panels, but new markets were emerging in the Americas, Australia, China, India, Middle East and Africa.
IEA executive director Maria van der Hoeven said: "The rapid cost decrease of photovoltaic modules and systems in the last few years has opened new perspectives for using solar energy as a major source of electricity in the coming years and decades.
"However, both technologies are very capital intensive: almost all expenditures are made upfront. Lowering the cost of capital is thus of primary importance for achieving the vision in these roadmaps."
She said that clear signals can lower deployment risks to investors and inspire confidence in building up solar technology - which once it is installed is very cheap as the sun that creates the energy is free.
"By contrast, where there is a record of policy incoherence, confusing signals or stop-and-go policy cycles, investors end up paying more for their investment, consumers pay more for their energy and some projects that are needed simply will not go ahead."
Sven Teske, senior energy expert for Greenpeace International said: "Greenpeace welcomes the IEA's conclusion that solar energy will be the dominant form of power generation within 35 years.
"Following last week's UN Climate Summit, it is precisely the kind of good news that everyone concerned about climate change will want to hear.
"Wind and solar power will continue to dominate the renewable energy market as the cheapest ways of generating power.
"Greenpeace calls on global energy policy makers to accept the reality of renewable energy and adapt the energy market accordingly.
"Phasing out fossil and nuclear fuels is an environmental and an economic necessity, and not a burden. The stellar economic performance of solar and wind power means that those who back coal-fired power plants seriously risk stranded investments."
Friends of the Earth renewable energy campaigner Alasdair Cameron said: "Solar panels are more affordable than ever - every public building should have them.
"But our cash-strapped schools still need help to meet upfront costs. The Government should act now to allow all schools to borrow money to invest in solar panels.
"This simple change could bring in up to £240 million a year for schools across the country, and prevent the emission of more than half a million tonnes of carbon dioxide."