Business Green: The US and South Africa this week have each moved a step closer to building two giant new solar farms, both of which will lay a claim to being the world’s largest and could serve to establish the countries as solar technology hubs. The US looks set to secure the title first after the Department of the Interior yesterday gave final approval to a proposed 1GW solar project planned for Blythe, California. The giant project is backed by German solar firm Solar Millennium and is …