The Desolenator: producing clean water

14 A Travelling around Thailand in the 1990s, William Janssen was impressed with the basic rooftop solar heating systems that were on many homes, where energy from the sun was absorbed by a plate and then used to heat water for domestic use. Two decades later, Janssen developed that basic idea he saw in Southeast Asia into a portable device that uses the power from the sun to purify water.

15 B The Desolenator operates as a mobile desalination unit that can take water from different places, such as the sea, rivers, boreholes and rain, and purify it for human consumption. It is particularly valuable in regions where natural groundwater reserves have been polluted, or where seawater is the only water source available.

Janssen saw that there was a need for a sustainable way to clean water in both the developing and the developed countries when he moved to the United Arab Emirates and saw large-scale water processing. ‘I was confronted with the enormous carbon footprint that the Gulf nations have because of all of the desalination that they do,’ he says.

16 C The Desolenator can produce 15 litres of drinking water per day, enough to sustain a family for cooking and drinking. Its main selling point is that, unlike standard desalination techniques, it does not require a generated power supply: just sunlight. It measures 120 cm by 90 cm, and is easy to transport, thanks to its two wheels. Water enters through a pipe, and flows as a thin film between a sheet of double glazing and the surface of a solar panel, where it is heated by the sun. The warm water flows into a small boiler, heated by a solar-powered battery, where it is converted to steam. When the steam cools, it becomes distilled water. The device has a very simple filter to trap particles, and this can easily be shaken to remove them. There are two tubes for liquid coming out: one for the waste -- salt from seawater, fluoride, etc. -- and another for the distilled water. The performance of the unit is shown on an LCD screen and transmitted to the company which provides servicing when necessary.

17 D A recent analysis found that at least two-thirds of the world’s population lives with severe water scarcity for at least a month every year. Janssen says that by 2030 half of the world’s population will be living with water stress -- where the demand exceeds the supply over a certain period of time. ‘It is really important that a sustainable solution is brought to the market that is able to help these people,’ he says. Many countries ‘do not have the money for desalination plants, which are very expensive to build. They do not have the money to operate them, they are very maintenance intensive, and they do not have the money to buy the diesel to run the desalination plants, so it is a really bad situation.’

18 E The device is aimed at a wide variety of users -- from homeowners in the developing world who do not have a constant supply of water to people living off the grid in rural parts of the US. The first commercial versions of the Desolenator are expected to be in operation in India early next year, after field tests are carried out. The market for the self-sufficient devices in developing countries is twofold -- those who cannot afford the money for the device outright and pay through microfinance, and middle-income homes that can lease their own equipment. ‘People in India do not pay for a fridge outright; they pay for it over six months. They would put the Desolenator on their roof and hook it up to their municipal supply and they would get very reliable drinking water on a daily basis,’ Janssen says. In the developed world, it is aimed at niche markets where tap water is unavailable -- for camping, on boats, or for the military, for instance.

19 F Prices will vary according to where it is bought. In the developing world, the price will depend on what deal aid organisations can negotiate. In developed countries, it is likely to come in at $1,000, or £685, a unit, said Janssen. ‘We are a venture with a social mission. We are aware that the product we have envisioned is mainly finding application in the developing world and humanitarian sector and that this is the way we will proceed. We do realise, though, that to be a viable company there is a bottom line to keep in mind,’ he says.

20 G The company itself is based at Imperial College London, although Janssen, its chief executive, still lives in the UAE. It has raised £340,000 in funding so far. Within two years, he says, the company aims to be selling 1,000 units a month, mainly in the humanitarian field. They are expected to be sold in areas such as Australia, northern Chile, Peru, Texas and California.

Why fairy tales are really scary tales

Some people think that fairy tales are just stories to amuse children, but their universal and enduring appeal may be due to more serious reasons.

People of every culture tell each other fairy tales, but the same story often takes a variety of forms in different parts of the world. In the story of Little Red Riding Hood that European children are familiar with, a young girl on the way to see her grandmother meets a wolf and tells him where she is going. The wolf runs on ahead and disposes of the grandmother, then gets into bed dressed in the grandmother’s clothes to wait for Little Red Riding Hood. You may think you know the story -- but which version? In some versions, the wolf swallows up the grandmother, while in others it locks her in a cupboard. In some stories Red Riding Hood gets the better of the wolf on her own, while in others a hunter or a woodcutter hears her cries and comes to her rescue.

The universal appeal of these tales is frequently attributed to the idea that they contain cautionary messages: in the case of Little Red Riding Hood, to listen to your mother, and avoid talking to strangers. ‘It might be what we find interesting about this story is that it has got this survival-relevant information in it,’ says anthropologist Jamie Tehrani at Durham University in the UK. But his research suggests otherwise. ‘We have this huge gap in our knowledge about the history and prehistory of storytelling, despite the fact that we know this genre is an incredibly ancient one,’ he says. That has not stopped anthropologists, folklorists and other academics devising theories to explain the importance of fairy tales in human society. Now Tehrani has found a way to test these ideas, borrowing a technique from evolutionary biologists.

To work out the evolutionary history, development and relationships among groups of organisms, biologists compare the characteristics of living species in a process called ‘phylogenetic analysis’. Tehrani has used the same approach to compare related versions of fairy tales to discover how they have evolved and which elements have survived longest.

Tehrani’s analysis focused on Little Red Riding Hood in its many forms, which include another Western fairy tale known as The Wolf and the Kids. Checking for variants of these two tales and similar stories from Africa, East Asia and other regions, he ended up with 58 stories recorded from oral traditions. Once his phylogenetic analysis had established that they were indeed related, he used the same methods to explore how they have developed and altered over time.

First he tested some assumptions about which aspects of the story alter least as it evolves, indicating their importance. Folklorists believe that what happens in a story is more central to the story than the characters in it -- that visiting a relative, only to be met by a scary animal in disguise, is more fundamental than whether the visitor is a little girl or three siblings, or the animal is a tiger instead of a wolf.

However, Tehrani found no significant difference in the rate of evolution of incidents compared with that of characters. ‘Certain episodes are very stable because they are crucial to the story, but there are lots of other details that can evolve quite freely,’ he says. Neither did his analysis support the theory that the central section of a story is the most conserved part. He found no significant difference in the flexibility of events there compared with the beginning or the end.

But the really big surprise came when he looked at the cautionary elements of the story. ‘Studies on hunter-gatherer folk tales suggest that these narratives include really important information about the environment and the possible dangers that may be faced there -- stuff that is relevant to survival,’ he says. Yet in his analysis such elements were just as flexible as seemingly trivial details. What, then, is important enough to be reproduced from generation to generation?

The answer, it would appear, is fear -- blood-thirsty and gruesome aspects of the story, such as the eating of the grandmother by the wolf, turned out to be the best preserved of all. Why are these details retained by generations of storytellers, when other features are not? Tehrani has an idea: ‘In an oral context, a story will not survive because of one great teller. It also needs to be interesting when it is told by someone who is not necessarily a great storyteller.’ Maybe being swallowed whole by a wolf, then cut out of its stomach alive, is so gripping that it helps the story remain popular, no matter how badly it is told.

Jack Zipes at the University of Minnesota, Minneapolis, is unconvinced by Tehrani’s views on fairy tales. ‘Even if they are gruesome, they will not stick unless they matter,’ he says. He believes the perennial theme of women as victims in stories like Little Red Riding Hood explains why they continue to feel relevant. But Tehrani points out that although this is often the case in Western versions, it is not always true elsewhere. In Chinese and Japanese versions, often known as The Tiger Grandmother, the villain is a woman, and in both Iran and Nigeria, the victim is a boy.

Mathias Clasen at Aarhus University in Denmark is not surprised by Tehrani’s findings. ‘Habits and morals change, but the things that scare us, and the fact that we seek out entertainment that is designed to scare us -- those are constant,’ he says. Clasen believes that scary stories teach us what it feels like to be afraid without having to experience real danger, and so build up resistance to negative emotions.

Folklorists: those who study traditional stories.