When a company wants a green data center, it often has to build its own energy sources. Google knows that's sometimes not practical, even for a company its size. To that end, it's partnering with Duke Energy on a proposed business model that would let companies explicitly purchase renewable electricity: companies could demand eco-friendly power sources, whether or not they're the most cost-efficient. The Duke approach goes to a state commission for approval within 90 days, and it might let Google expand a Lenoir, North Carolina data center (above) with a clearer conscience and minimal costs. The real challenge may be getting other utilities to follow in Duke's footsteps -- even if there are no legal hurdles, local power providers still have to implement clean energy on a large enough scale. If they do, however, environmental responsibility may be within reach to those businesses more interested in building server farms than solar farms.