When most of us think of solar energy, we think solar panels, but there's a new way to do solar. You're not likely to see this on anyone's rooftop. It requires large amounts of land, high technology, and really high temperatures, but, it's still emissions-free and powered by the sun. It's Sandia National Laboratories' continuously recirculating falling particle receiver.
Here's how it works: In the New Mexico desert there's a massive array of mirrors. These mirrors can reflect and focus sunlight at a tower. This facility is used for all sorts of things that require extremely high temperatures, like testing heat shields for various spacecraft.
But recently a team of researchers used this facility to test a new way of collecting and this is the really big deal: storing solar energy. The team has developed a new type of ceramic particle, about the size of a grain of sand for this purpose. They are experimenting with dropping a stream of these particles through the focused beam of sunlight which heats them up to about 1,800 degrees Fahrenheit (about 1,000 degrees Celsius). The particles then fall into an insulated tank where they can store that heat energy. A similar technology has been tried before with molten salt, but researchers found that this system could only get up to about 1,112 degrees Fahrenheit, and that the molten salt didn't do a fantastic job of storing the heat due to the fact that over time the molten salt would break down. The ceramic crystals, however, do not have that problem.
The higher temperatures that the ceramic particles being able to operate at mean more available energy and cheaper storage costs because less material is needed to transfer heat. This is a big deal in that it addresses the main weaknesses with solar panels, which have kept solar from becoming a larger part of energy generation so far.
"This technology will enable higher temperatures and higher efficiency power cycles," says Sandia Cliff Ho, the project's principal investigator, "that will bring down the cost of electricity produced from concentrating solar power. In addition, the ability to cheaply and efficiently store thermal energy directly in the heated particles will enable power production at night and on cloudy days." Being able to store solar energy will allow for steady energy production from solar generating stations 24/7 just like plants that burn fossil fuels.
Things look good for Ho and her team. Their new falling particle receiver technology is expected to further advance the cutting edge of solar power. Collecting tower systems like this are expected to be capable of generating up to 100 megawatts of electricity, on par with a fossil fuel generating plant. And that is the plan, as this project is funded largely by the U.S. Department of Energy's SunShot Initiative. The goal SunShout of is to reduce solar energy costs and to expand the use of solar energy technologies nation-wide.