Electricity generation is the process of generating from sources of. For in the, it is the stage prior to its (,, etc.) to end users or its, using for example, the method. Consumable electricity is not freely available in nature, so it must be "produced", tra. The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce, such as experiments by. installed the world's first rooftop photovoltaic solar array, using 1%-efficient cells, on a New York City roof in 1884. However, development of solar technologies stagnated in the early 20th century in the face of the increasing a.