Global climate change is here, and it’s only going to get worse, according to a White House report released on Tuesday. To combat rising sea levels and blistering summers, the Obama administration has been pushing for clean, renewable energy sources that cut down on carbon emissions. Now one of its projects is poised to pan out: Agua Caliente, the largest photovoltaic solar power facility in the world, was completed last week in Arizona.



The plant comprises more than five million solar panels that span the equivalent of two Central Parks in the desert between Yuma and Phoenix. It generates 290 megawatts of power—enough electricity to fuel 230,000 homes in neighboring California at peak capacity. The Agua Caliente Solar Project represents a significant advance in the technology compared with just four years ago, when the largest solar facility in the U.S. generated only 20 megawatts. “Solar has completely arrived as a competitive energy resource,” says Peter Davidson, executive director of the Loan Programs Office at the U.S. Department of Energy (DoE).



The project, which cost a total of $1.8 billion to construct, received a million-dollar loan from the Loan Programs Office. Under its “SunShot” initiative (so-named in the spirit of president John F. Kennedy’s “moon shot” program), the DoE provides guaranteed loans to unproved ventures in solar power in the hopes of promoting innovation and making the technology more cost-effective.* Although Agua Caliente (owned by U.S. energy giant NRG Energy and partner MidAmerican Solar) is now the largest photovoltaic solar facility in the world, it probably will not hold that distinction for long. Other massive solar panel facilities, such as Antelope Valley Solar Ranch One in California’s Mojave Desert, are rapidly springing up across the Southwest. “This series of large plants that are being built really mark the transition from the technology being something experimental to real energy on the grid,” agrees Robert Margolis, a senior analyst at the National Renewable Energy Laboratory (NREL). Solar power currently accounts for 1 percent of U.S. energy production, but it is the fastest-growing sector of the energy landscape. Margolis says that Agua Caliente proves that investing in solar power on a large scale is an effective way to make it more viable in the current market.



The energy contained in just one hour of sunlight could power the world for a year, if only it could be harnessed. Traditional solar panels made from silicon—the gold standard of semiconducting material—are expensive, however, particularly in comparison with cheap but dirty coal and natural gas. Agua Caliente, which is operated and maintained for NRG by Tempe, Ariz.–based First Solar, uses newer, thin-film panels that that absorb the same amount of sunlight with a fraction of the material, boosting the array’s efficiency.



NRG has a deal with utility company Pacific Gas & Electric to sell them the energy generated by the plant for 25 years. California law mandates that utilities get 33 percent of their electricity from renewable sources by 2020.



The massive scale of facilities like Agua Caliente enables energy companies to buy the construction materials in bulk, which reduces costs. But there are downsides to this arrangement. The sheer magnitude of such complexes makes them difficult to maintain, and some environmental groups argue that the immense structures displace local wildlife. Many California legislators therefore prefer small-scale plants that can be built closer to the places they supply.



And as with traditional solar power plants, there is still the issue of what to do when the sky is overcast. One of the most interesting things about Agua Caliente, says John Karam, senior director of asset management at NRG Solar (an NRG subsidiary), is how it deals with cloudy days. There are extra panels built into the site, so “when the plant is partially covered by clouds, the control system can actually call upon the portion of the panels that is not impacted” and recruit the extras there to make up the difference.



“The systems are getting smarter,” NREL’s Margolis notes. “One of the next frontiers in research and development is integrating very large quantities of solar into the system by having smarter controls, and also improving the ability to forecast when clouds will come and what the behavior of the system will be so that utilities can prepare.”



Consumers won’t notice much of a difference right away, as utility companies typically draw from a wide array of energy sources, DoE’s Davidson says. “Its like pouring water into a pool: It all gets blended in and then patched out.”



But as solar power becomes cheaper, Davidson predicts that utilities will pass those savings on to consumers. And as the technological advancements emerging from megaplants like Agua Caliente become more widely available, individual solar power adopters may eventually see savings as well.



*Correction (5/9/14): This and the previous sentence have been edited since posting to correct an error. They originally stated that the Department of Energy's SunShot initiative granted the loan rather than the DoE's Loan Programs Office.



