The Sierra Sun Tower in Lancaster is an example of how sustainability is always being refined and re-evaluated.
The project revolves around a high tower that has a 60-ton boiler on top. On both the north and south sides of the tower, on the ground level, are 6,000 mirrors that track the sun. Each mirror tracks the sun from sun up to sun down. The main plant pumps water to the top of the tower and the water is then flash boiled to 1,000 degrees. The steam turns a steam turbine and is then collected, cooled, and sent back into the system once again. The power plant generates enough power to run the plant as well as export power onto the local grid without emitting any green house gases.