German conglomerate Robert Bosch GmbH has agreed to buy a 50.5 per cent stake in solar-cell maker Ersol Solar Energy AG from its private equity owner for around €546.4 million ($846.9 million).

Bosh said it would also make a bid for the outstanding shares as it expands its portfolio of environment-friendly products.

Bosh made the acquisition from equity fund Ventizz Capital Fund II LP and its Channel Island-based subsidiary Ventizz II Jersey Holding LP.

In a communique to the management board of Ersol Solar Energy AG, the buy-out funds said they have signed agreements with Robert Bosch GmbH ) regarding the sale of its 50.45 per cent holdings in Ersol share capital.

Stuttgart-based Bosch said it would launch a public offer at €101 per share, the same price it paid Ventizz for its holding. The offer represents a substantial 63 per cent premium to the stock's Friday close.

Germany is already the world¹s biggest supplier of solar equipment and Bosch recently announced plans to become the world's biggest maker of hybrid drivetrains for vehicles. The company already makes gears and other parts for wind turbines and is hoping to offer ocean-energy generation gear, a technology still under development.

''With its existing activities in this area, Bosch plans to generate sales of some €750 million in 2008,'' the company said.

''I have no doubt that Ersol will continue its successful path with the new majority shareholder. My fellow board members and I are looking forward to working together with Bosch,'' said Claus Beneking, CEO of Ersol Solar Energy AG.

Ersol generated revenue of €52.4 million in the first quarter, twice as much as in the first quarter of 2007, and an EBIT of €7.7 million, an 80 per cent increase over the first three months of 2007.

The group, which employs about 1,000, expects total 2008 sales of €300 million, up from €160 million last year.

The board Ersol is recommending that shareholders accept the offer.

The transaction is subject to the approval of the customary antitrust authorities.