Solar energy can trace its roots to the early 19th century, when in 1838 French physicist Edmund Becquerel , published his findings about the nature of materials being able to turn light into energy. He discovered the photovoltaic effect while experimenting with an electrolytic cell made up of two metal electrodes. Becquerel found that certain materials would produce small amounts of electric current when exposed to light. At the time this was an interesting discovery that was not appreciated. Twenty years passed before Auguste Mouchout , a French mathematics teacher, designed and patented the first machine that generated electricity using the sun. Mouchout began his work with solar energy in 1860. He produced steam by heating water using a glass-enclosed, water-filled iron cauldron. Mouchout then added a reflector to concentrate additional radiation onto the cauldron, thus increasing the steam output. He succeeded in using his apparatus to operate a small steam engine. At the 1878 Paris Exhibition, he demonstrated a solar generator that powered a steam engine, similar to the one shown in Figure 5.1. This engine included a mirror and a boiler that drove an ice-maker that produced a block of ice. Later in 1869, Mouchot wrote one of the first books devoted to solar energy: “Le Chaleur Solaire et les Applications Industrielles.” Mouchout's work help lay the foundation for our current understanding of the conversion of solar radiation into mechanical power driven by steam.