A solar furnace is any structure that catches sunlight and uses it to produce high temperatures. These are primarily used for industry, and vary greatly in size and power.
Solar furnaces can be made out of specially constructed curved mirrors or out of many small flat mirrors arranged in a curve. These mirrors catch sunlight and focus it on one point. In a test by the Massachusetts Institute of Technology, a solar furnace was able to burn a hole through 1-inch oak planks. The same technology works in miniature in a solar cooker or solar oven.
Solar furnaces can reach extremely high temperatures. The world's largest solar furnace in the Pyrenees can produce temperatures up to 2999 degrees Celsius, according to Atlas Obscura. The U.S. Army has a solar furnace in New Mexico that creates temperatures close to 6,000 degrees.
Solar furnaces have a number of different uses. The Army furnace in White Sands, New Mexico is used for defence research. They can also be used to pasteurise water and create steam for electricity production.