Thirsty work

By 2025, the United Nations forecasts that 1.8 billion people will be living in countries or regions with water scarcity and two thirds of the world's population could be under conditions of water stress. Climate change is expected to aggravate water problems via more extreme weather events. For this reason, there is currently a rush to arrive at any intelligent and improved management options to overcome these challenges. The need to retain water in the most apparently dry conditions is therefore paramount. Even the driest air contains water molecules which can be extracted by lowering the air's temperature to the point of condensation. The only question is 'how'? The Challenge The challenge this month is therefore to come up with a means of collecting the water molecules in the air and harnessing them in such a way that they can be used to irrigate water-starved areas. The solution is obviously based on the collection of condensation. After all, collecting condensation on a plastic groundsheet has long been standard practice among survival experts in even the driest conditions, but such a method is far from efficient and where water is scarce, efficiency is everything. And, of course, collecting this water is only the first step. The real difficulty arises in working out how to collect this water and use it to irrigate land. Clearly, the greatest problem with any storage system will be in preventing the water from evaporating when exposed to the desert sun. And, once that problem is overcome, how does one distribute it in such a way that ensures it is not wasted? A solution to this problem has been developed that uses biomimicry to achieve excellent results. Indeed, trials have been carried out that have shown that the invention can return 10% of lost water and lead to cuts in energy bills for nearby buildings by reducing a city's heat sink effect. But none of that means that you can't do better, of course. The solution will be revealed in our February issue, but in the meantime, see if you can improve on it. -Solution- Solution to January's Coffee Time Challenge The solution to the Challenge of how to harvest water in arid conditions has won The James Dyson Award for 2011 and is a clever piece of biomimicry developed by Edward Linacre of Swinburne University of Technology in Melbourne has tapped the Namib beetle--a desert dwelling species that survives in the most arid conditions on Earth--to create an irrigation system that can pull liquid moisture straight out of dry desert air. Airdrop, as the system is known, borrows a trick from the Namib beetle, which can live in areas that receive just half an inch of rain per year by harvesting the moisture from the air that condenses on its back during the early morning hours. A hydrophilic skin helps to snare water molecules passing on the breeze, which then accumulate into droplets of consumable liquid water. First, a turbine draws air underneath the ground into a network of pipes. When the air reaches condensation point the water pours down into a underwater tank. A submersible pump pumps the water back up through the central column of the piping and this is pumped through to the roots of plants through a process called sub-surface drip irrigation – which is the most efficient method of irrigating crops because you don't get evaporation. A huge breakthrough was made by putting copper wool inside the pipes. The wool was cooled by the pipes and this increased the surface area within the pipes that was cool enough to cause condensation to take place.