April 28 (Reuters) - U.S. buyout firm KKR has reached a deal to buy France's Albioma for 50 euros per share, the renewables power producer said on Thursday, sending its shares up 15% in morning trade.

The stock was trading at 50.30 euros at 0900 GMT.

Albioma said the offer - which includes an additional 84 cent cash dividend - represents a 52% premium to its closing price on March 7, before reports that KKR was in the early stages of discussing a bid sent prices soaring.

"The offer price seems to us rather ungenerous, given the group's fundamentals, the ongoing shift towards 100% renewable and anticipated earnings growth from 2023," said Portzamparc analyst Nicolas Royot.

Midcap Partners, however, called the premium "generous" in light of the group's ongoing exposure to coal which has weighed on its share price.

Albioma's market value after the announcement had risen to around 1.7 billion euros ($1.8 billion).

Albioma operates a hybrid coal thermal plant in Reunion, which it is in the process of converting to 100% biomass using bagasse, forest wood and imported pellets.

It aims to completely stop using coal there by the end of 2023.

"KKR fully supports the group's strategy to approach 100% renewable energy by 2030," Albioma said in a statement, adding that the firm would preserve the company's jobs and corporate identity.

It said state-owned bank and shareholder Bpifrance would be investing alongside KKR.

European countries have been looking increasingly to renewable energy as an escalating economic war following Russia's invasion of Ukraine threatens the region's gas supplies.

($1 = 0.9511 euros) (Reporting by Sarah Morland; editing by Jacqueline Wong and Jason Neely)