What are photovoltaics? The word comes from “photo” (light) and “voltaic” (energy produced by a chemical reaction). Photovoltaic technology refers to the conversion of light into energy at the atomic level. Certain materials, such as silicon, cadmium, and selenium, have the ability to absorb light photons and release electrons. Solar photovoltaic technology harnesses these freed electrons and uses their electric current as DC electricity (NASA 2002).
Fully powered by the sun, solar photovoltaics are a free, clean, and renewable source of energy that can be used independently of or in conjunction with conventional grid energy. Unlike solar thermal systems, solar energy panels require little maintenance, necessitate no moving parts, and last for 30-40 years.
"Hot springs have been used for bathing at least since paleolithic times[9] The oldest known spa is a stone pool on China's Lisan mountain built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. In the first century AD, Romans conquered Aquae Sulis, now Bath, Somerset, England, and used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power. The world's oldest geothermal district heating system in Chaudes-Aigues, France, has been operating since the 14th century.[10] The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy."
