A worker is silhoutted as he works on the construction of a boiler at the building site of a 240 meter (787 feet) solar-power tower in Israel's southern Negev Desert, February 8, 2016. The world's tallest solar-power tower is being built off a highway in the Negev Desert in southern Israel, its backers hoping the technology will gain a foothold in the solar market even if it remains a small player for now. Picture taken February 8, 2016. REUTERS/Amir Cohen