*Spanish government boosts solar power Madrid — Oil major Shell and utilities Naturgy (NTGY.MC) and Verbund (VERB.VI) are preparing binding bids to buy renewable energy assets in Spain valued at about 1 billion euros ($1.1 billion), three sources close to the matter told Reuters. Spanish fund manager Q-Energy is selling the portfolio, taking advantage of strong appetite among European energy companies feeling increasing pressure from investors and governments to tackle climate change. Competition for market share is intensifying as oil and gas companies set ambitious green targets, jostling with utilities and existing renewables businesses to lead the energy transition. Binding bids are due by the end of April, the sources said. Shell, Naturgy and Q-Energy declined to comment. Verbund did not immediately respond to a request for comment.