(Recasts with quotes, detail) MADRID, Feb 19 (Reuters) - Spanish engineering group Acciona aims to hive off and sell shares in its energy unit in the first half of this year in a bid to ramp up its clean power capacity and cut debt, its chief executive said on Friday. Acciona makes most of its profit from renewable energy, which policymakers around the world are increasingly recommending to help phase out carbon. It now plans to sell at least 25% of that business to help fund the near doubling of its generation fleet, currently dominated by wind farms in the United States, Australia, Spain, Chile and Mexico, to reach 20 gigawatts (GW) capacity by 2025. Asked when the deal would take place, Chief Executive Jose Manuel Entrecanales told reporters the company was aiming for the first half of the year, but that this would depend on factors beyond his control. He declined to discuss price, but bankers in the sector expect the unit could be valued at least 10 times its core earnings of 831 million euros ($1.01 billion). Beyond wind and solar, Acciona is working on nascent technologies including producing hydrogen from renewable sources, and wants to capture 20% of the hydrogen market in Spain and Portugal through a joint venture signed earlier this week with U.S. firm Plug Power. The new listed entity “will continue to consider additional potential M&A operations that will allow us to secure our growth in the decade”, Acciona Energia Chief Executive Rafael Mateo said. Spanish oil and gas firm Repsol is also working on spinning off its low-carbon business and selling a stake either to a partner or on a public exchange. Acciona has not hired financial advisers, a typical early step in the process of listing a company, Entrecanales said. The parent company intends to keep a majority stake in the long term. Shares in Acciona leapt on news of the planned listing on Thursday and stayed 16% higher than Wednesday’s close on Friday. The stock regained its pre-pandemic peak in early January. Some of the proceeds will go to paying down debt, which exceeded 4.2 times core earnings at the end of 2020. The company also hopes the deal will give it access to cheaper capital. ($1 = 0.8241 euros) (Reporting by Isla Binnie and Nathan Allen; Editing by Jan Harvey)