Xtreme Energetics has investigated the possibility of using mechanical trackers to perform the same light-focusing duties as other solar array manufacturers have. However, HP’s transparent transistor can do the job electronically, rather than mechanically, and significantly reduce the costs of such an installation. Such a solar array is known as a concentrating photovoltaic (or CPV) solar array. To date, CPV arrays are fairly expensive and cannot store energy, making them less useful. They also work best in specific sections of the world — those with the highest levels of solar radiation, such as the southwest United States and northern Africa.