The largest solar power plant is appearing now in Las Vegas. It spread over 3600 acres, and it will generate370 megawatts of electricity on the sunny days. The big project will be built Oakland, California-based Brightsource.
The project has been a long time coming. Brightsource first filed an application for the project in the summer of 2007. Approval took three years. Construction was temporarily slowed to accommodate the care and relocation of desert tortoises—a threatened species—found in larger numbers than expected. The project, which will generate electricity by using mirrors to concentrate sunlight to heat up water and drive steam turbines, is now expected to be finished next year.
Even as the project nears completion, the future of solar thermal power plants is in doubt. That’s in large part because prices for solar panels—which convert sunlight to electricity directly—have dropped quickly in the last few years, causing at least one company to abandon plans to build solar thermal plants in favor of making ones that use solar panels.
Yet solar thermal has at least one great strength compared to many other types of solar power: the heat it produces is easy to store, so electricity can be generated even after the sun goes down, and power can be dispatched to the grid whenever it’s most needed.
The new cell design is a variation on the Grätzel cell(named after the Swiss chemist Michel Grätzel), a type of dye-sensitized solar cell that replaces silicon with the semiconductor titanium oxide, which is more abundant, cheaper and less toxic, further improving solar energy’s green credentials. However, there is a problem with the Grätzel design: its electrolyte is made of an organic liquid that leaks, threatening to corrode the cell. Northwestern University researchers have solved the problem by using a new material that solidifies, thus avoiding leaks and making the solid-state cell more stable. The material is a thin-film compound called CsSnI3, a combination of cesium, tin and iodine.
It is added in liquid form to dye-coated nanoparticles and then it turns into a solid mass.
At 10.2 percent, the conversion rate leaves something to be desired when compared to silicon cells that can achieve around 20 percent, but it nearly matches the performance of a Grätzel cell, which reaches around 11 or 12 percent. The technology is projected to improve, however. “This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the Grätzel cell,” researcher Robert P. H. Chang said. “Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we’ve seen so far.” The CsSnl3 compound can absorb more light than the dye used in Grätzel cells, increasing the cell’s conversion potential.