3.1.2 HISTORY

Solar energy has been used since the beginning of humanity when the sun was used to dry skins and foods. Archaeologists have shown that glass lenses were used no later than the 7th century BCE to concentrate the light of the sun and burn small pieces of wood to start a fire.

In the first modern development (1767), Horace de Saussure, a noted Swiss scientist, observed that a room or a carriage is hotter when the rays of the sun pass through glass. He built a rectangular box out of half-inch pine, insulated the inside, covered the top with glass, and placed two smaller boxes inside. When exposed to the sun, the bottom box reached 228 ^oF (109 °C) (or 9 °C above the boiling point of water).

Figure 3.1 Hot boxes for cooking

 

Renowned astronomer Sir John Herschel used solar hot boxes (fig 3.1) to cook food during his expedition to Southern Africa in the 1830s. Solar thermal energy became important in parts of Africa for cooking and water distillation.

Although more than a dozen inventors filed patents during 1900-1911 that improved upon the hot box, the heating and storage units always remained one and the same and both stayed exposed to the weather and the cold night air. Hence, water heated by the sun the night before never stayed hot enough for washing the next morning or to heat the bath. In 1909, William J. Bailey patented a revolutionary solar water heater by separating it into two parts: a heating element exposed to the sun and an insulated storage unit tucked away in the house so families could have sun heated water day and night and early the next morning.

Solar water heating thrived during the years of high energy prices arising from the oil crisis in the 1970s. Many EU companies were created to manufacture, sell and install new solar water heaters in private houses, public buildings and swimming pools, and were backed up by government sponsored research and development projects. Great hopes were built on this growing market, but by the mid-1980s the situation changed, oil prices started to fall and the public fear of energy shortage slowly died out.

The solar industry suffered badly and most of the new companies disappeared. Those that managed to survive improved their products, production methods and quality controls in order to satisfy more exacting customer demands. The market

stabilised, but at a rather low level. During the 1980s evacuated tube collectors were developed to improve efficiency but at greater cost. This new technology has taken an increasing share of the EU market during the last decade, particularly in Germany, Greece and Austria.