U.S. firm Duke Energy may be building its last two coal plants to bet instead on nuclear power, chief executive James Rogers said on Tuesday.

Rogers described his company as the third largest U.S. generator of electricity from coal and the third largest from nuclear. If Duke Energy had to choose between one technology or the other Rogers said: I'm betting on nuclear.

And I would go a step further and probably say that these two coal plants we build might well be the last two we build until we have a clear picture on CCS, he told reporters, referring to two planned coal plants.

Carbon capture and storage (CCS) technology involves trapping the greenhouse gas carbon dioxide from the flue gas of power plants and burying it underground. It is commercially untested and is a decade to 15 years off, Rogers said.

He was speaking on the sidelines of a May 24-26 meeting of more than 500 business leaders. They will issue on Tuesday a call for governments to set clear long-term climate policies when they meet in Copenhagen in December to try and sign a new global climate pact to replace the Kyoto Protocol.

Rogers said nuclear posed a smaller waste disposal problem than coal plants, because nuclear waste required a far smaller area to store waste and because CCS requires long-distance transport of carbon dioxide gas.

The extra cost of CCS may make rival, non-fossil fuel alternatives such as wind and solar competitive, said Steve Lennon, managing director of corporate affairs at South African utility Eskom.

That's probably going to take 20 years, he added.

In the nearer term renewables were too costly and not helped by a financial crisis which has raised the cost of financing.

We are looking at building in this year a pilot 100 megawatt solar thermal plant, although quite frankly we're battling with the financing. It's very difficult to borrow the kind of money which you need for these really big expansion programmes.

South Africa is in a very difficult position, we have massive coal resources. It's the biggest and the cheapest form of baseload energy.

(Reporting by Gerard Wynn; editing by James Jukwey)

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