LONDON, June 23 (Reuters) - Global greenhouse gas emissions from the power sector are expected to peak in 2029 and then start falling, but will still be some way above levels needed to limit temperature rise, research showed on Tuesday.

Electricity generation worldwide is forecast to rise by 56 percent by 2040 as economies develop and populations grow, which will hit a peak in power sector emissions of 15.3 gigatonnes in 2029 from 13.1 gigatonnes now, a report by Bloomberg New Energy Finance said.

World emissions will start to fall after 2029 to 14.8 gigatonnes in 2040, which is 13 percent above 2014 levels.

This will make it very unlikely that the world will be able to limit average the rise in temperature to within 2 degrees Celsius, a threshold seen by scientists as necessary to avoid the worst effects of climate change.

“We will see tremendous progress towards a decarbonised power system. Despite this, coal will continue to play a big part in world power with emissions continuing to rise for another decade and a half, unless further radical policy action is taken,” said Michael Liebreich, chairman of Bloomberg New Energy Finance’s advisory board.

Overall, around $12.2 trillion will be invested in global power generation between 2015 and 2040. Renewables will account for two thirds of that, while $1.6 trillion will be spent on coal, $1.2 trillion on gas and $1.3 trillion on nuclear.

Fossil fuels will account for 44 percent of world power generation in 2040, down from 67 percent in 2014.

Natural gas will not be the main transition fuel to wean the world off coal, the report said. Coal-to-gas switching will mainly take place in the United States, while developing nations will use both coal and renewables.

New investment in solar capacity should rise to $179 billion in 2040 from $136 billion last year, as the cost of photovoltaic (PV) technology continues to fall.

Small-scale solar capacity, such as rooftop or local PV systems, is seen rising to nearly 1.8 terawatts in 2040 - 17 times more than the current 104 gigawatts - due to a 47 percent crash in the cost of solar projects per megawatt as new materials and more streamlined production methods improve conversion efficiency.

The full report is available at: about.bnef.com/