| 摘要 |
<p>The foil for preventing evaporation can float on the surface of a body of water. It is also stabilised against wind and its evaporation protection varies with given weather conditions. At night dew can be collected through the foil. It may have projections on its underside and a reflecting side facing the sun. A reflecting coating can be applied. This foil has perforations to drain any leaked or rainwater on the foil underside, in the main body of the water. Alternatively the air side can be a dark colour and its underside a bright reflecting colour. The foil material may have high expansion characteristics so that the holes in the foil can be almost closed under hot sunshine. On cooling for example in the evenings the perforations open.</p> |
