Popular Science magazine's award for the best invention of 2010 was won by Dutch horticulturalist Pieter Hoff with a contraption that collects dew which then irrigates plants. This dish like apparatus is designed to allow plants to be grown in arid and semi-arid environments without recourse to irrigation. That could be useful for agriculture or ecological restoration in arid areas.
Dew catching is not new. In 1900 near the Ukranian city of Theodosia a large piles of stones were discovered which appeared to be condensers used to collect dew to supply drinking water. The discover, an engineer called Zibold conducted an experiment to demonstrate the technique. His 'air well' produced 360 litres a day and inspired others to copy, building similar structures around the Mediterranean. These high mass air wells worked promoting condensation of mopsiture from the air. They didn't catch on but used no energy or moving parts.
Dew tower of belgian engineer Achile Knappen in Trans-en-Provence Var. Photo: © Dr Michel Royon / Wikimedia Commons
They were replaced by lightweight, radiative collectors which lose heat quickly and were made from plastic sheeting or foil. They became popular in Israel and India in the 1980s. Researchers found that condensers should have high surface area, be low in mass and hydrophilic so as to shed water quickly. These installations have been used in desert areas to provide drinking water or more often, water for irrigation.
As well as being useful in providing water in arid areas, I believe that dew catching will have a future in combination with green roofs and living walls, where water will be increasingly important for evapo-transpirative cooling. Already skyscrapers are being designed with sail like structures to collect dew (like the rather sterile Blooming Tower in Dubai ) so it will be a short step to take a version of Pieter Hoff's waterboxx and cover buildings in it. In this way the water collected will not only provide evapo-transpirative cooling but the other benefits of building-integrated vegetation, including beauty, biodiversity and attenuation of rainfall will still be enjoyed. Kevin Songer in Florida is experimenting with dew catchers working in combination with green roofs . A relatively new approach to green roofs in hot and dry climates has been developed in Greece by Oikostges. The approach is very focussed on the creation of dew to help the plants make it through the day. A good example of this is a green roof in the southern suburbs of Athens. There are also some interesting water storing materials coming onto the market (for example Huntsman's water storing foam) so we can see the various components needed for pioneers to make their first tentative steps in this direction.
I predict a future with many buildings covered with feathery hydrophilic materials that capture the morning dew, which in turn nurtures water-soaked mats of vegetation and roofs and walls.
