The South African government on Thursday opened a bidding process for private companies to launch \"green\" energy projects to feed the national grid, in a bid to improve the power supply.The government will accept proposals for wind, solar and small hydro-electric projects, as well as projects to create energy from gases emitted by landfills and biological waste, the department of energy said in a statement.The process is part of the government\'s plan to double South Africa\'s power supply by adding more than 50,000 megawatts of electricity to the grid, with 30 percent of new power generation slated to come from independent power producers. The government plans to generate 3,725 megawatts of power from \"green\" renewable energy sources, which the energy department said will contribute \"towards socio-economic and environmentally sustainable growth, and to start and stimulate the renewable industry in South Africa.\"The government is spending 860 billion rands ($127 billion, 89 billion euro) over the next two decades to overhaul the national electricity system. Among its most ambitious proposals is the creation of what could become the world\'s biggest solar project at the edge of the Kalahari Desert, which would be built by private investors with government support for the infrastructure around it.South Africa\'s power generation relies heavily on coal-fired power stations, and the facilities have over the past years battled to cope with the increasing demand, causing rolling blackouts in January 2008.The state-owned power utility Eskom says the power supply will remain tight over the next five years, especially in 2011 and 2012, as the firm upgrades its aging infrastructure.