SolarReserve, based in Santa Monica, California, wants to convert 25 square miles of arid land 225 miles northwest of Las Vegas into the largest solar power plant in the world. If the proposed plant gets built, it could produce between 1,500 and 2,000 megawatts of electricity — enough to power 1,000,000 homes. That’s equivalent to the power of a nuclear power plant or Hoover Dam. The project would cost about $5 billion.

Last week, SolarReserve chief executive Kevin Smith outlined a plan Tuesday to create a 10 tower concentrated solar array dubbed Sandstone Energy X near the city of Tonopah in Nevada’s Nye County. SolarReserve already operates a single tower project on 1,600 acres of federal land outside Tonopah called the Crescent Dunes Solar Energy Plant. It can produce up to 110 megawatts of electricity by focusing a 1-mile circle of mirrors called heliostats on a 640 foot tall central tower to heat molten salt to more than 1,000 degrees Fahrenheit. The superheated salt is used to boil water to drive power turbines.

The secret to such concentrated solar power facilities is that the stored heat from the molten salt can continue to generate steam to keep the turbines running for up to 10 hours after the sun sets. SolarReserve says storing energy in molten salt is far less expensive than lithium ion batteries of similar capacity. Tesla is one of the leading providers of batteries for grid storage but there are many other companies competing in the battery storage business, including the Accumotive division of Daimler, the parent of Mercedes Benz.

Smith says a 16,000 acre Sandstone site on federal land in Nye County could be announced next year. Construction could begin by 2020. The company will explore federal loan programs and private financing options. SolarReserve’s Crescent Dunes single tower CSP installation cost about $1 billion and was backed by $737 million in federal loan guarantees. If the project goes forward, SolarReserve will need to build transmission lines to carry the electricity to market. It is expected that most of the electricity generated will be used to supply customers in California.

Concentrated solar power has been written off by many solar experts, partly because the facilities tend to be complicated and expensive to build. But the future of solar is tied directly to the issue of storage. That’s the factor that smooths out the varying output of all renewable energy sources. For renewables to meet or beat the cost of electricity made from burning fossil fuels, driving down the cost of storage will be critical.

In Spain, researchers are experimenting with using molten silicone as a storage medium instead of salt. They say the silicon can store ten times as much heat as salt. If true, the could drive the cost of solar power down below the cost of every other form of electrical energy and move the world closer to zero emissions power for all.