|SCIENCE & TECHNOLOGY||Thursday, October 23, 2003, Chandigarh, India|
Harvesting fog for water
Winter clouds have always been a source of misery. The ambient temperature falls, leaving people exposed to biting cold. Fog sets in, reducing visibility to a few metres, resulting in a numbers of accidents, cancellation of flights and delay in reaching offices. Rainwater has been harnessed successfully for our daily needs.
substitutes from bamboo
fog for water
Winter clouds have always been a source of misery. The ambient temperature falls, leaving people exposed to biting cold. Fog sets in, reducing visibility to a few metres, resulting in a numbers of accidents, cancellation of flights and delay in reaching offices. Rainwater has been harnessed successfully for our daily needs. Rivers, ponds and wells are all fed by rain. But isn’t fog also a source of water? Unfortunately, a source that has not been tapped to its fullest potential!
After all, what is fog? Fog is nothing but a mass of water vapour condensed into small droplets. The white blanket that sweeps our cities, green areas and forests is laden with water droplets varying in size from 1 mm to 40 mm. Sometimes, it completely envelops a whole town or a big forest, depending on the frequency of its occurrence or the velocity of the wind that carries it. In the forest, when fog sets in, the tree leaves are laden with water droplets. Whatever comes in the way of fog, traps the water droplets and lets the wind pass. Can we collect this water? It is difficult, but not impossible.
A simple net or a series of nets made up of nylon or polypropylene are put against the direction of wind. The mesh in weaned in triangular shape, which has a thickness of about 0.5mm. The mesh is then tied at two posts in a double layer. The water is collected in a tank underneath. The life of the mesh can be extended up to 10 years.
Fog collectors work best along the coasts because the fog rolls in from the sea or the ocean seasonally and in mountains where water is present in the clouds at an altitude of about 80 metres.
The idea of designing a nylon mesh was conceived from the behaviour of the stenocara beetle, that lives in Namibia; which is generally a dense morning fog area. The beetle tilts its body towards the wind. Droplets of water are formed on its wings that then travel down the body to its mouth. In the same way, each cubic metre of nylon mesh installed at a high elevation can collect more than 150 litres of water in a month.
The largest project of collecting up to 1000 litres of water daily has been installed in a coastal desert of Chile, where 75 fog collectors have been installed. The common collecting tank is connected to a village through approx. 6 km of pipeline.
Though this is a highly
unconventional technology, a seasonal one and requires large funding,
yet it can solve the winter water shortage problem in many areas. The
need of the hour is, after all, unconventional sources for the
conventional needs of human life. Those who laughed at solar energy
are today begging for power. Who knows, the fog exploiter may be the
Messiah of tomorrow’s thirsty world?
substitutes from bamboo
Since timber can no more be made available from natural forests for environmental considerations, wood scarcity is being faced by the industrial units and there is urgent demand for finding suitable substitutes.
Since bamboo can be grown in any part of the country in a short rotation of 3-4 years, it is emerging as a serious contender for providing substitutes for wood.
The potential of bamboo has been known since long and considerable research projects had been undertaken by the various research institutes for converting low-cost bamboo into valuable wood substitutes.
Now technology is available for commercial manufacture of products which can be converted into wood substitutes.
Bamboo is emerging as the material of the future due to the fact that it is fast growing, quick maturing, light yet strong, naturally structured "tube" material in ready-to-use form which is highly elastic. India has the largest resource of bamboo, both in term of diversity and distribution. Apart from being available in natural forests, it is now being raised in plantations. Bamboo is considered suitable for restoration of degraded and waste lands. India accounts for about 120 species, out of which 30 are known to have commercial potential.
China, with a much lower area under bamboo, is at present recognised as the world leader in supply of bamboo products. In India though bamboo is made use of but it is in the form of low-cost products.
Development of appropriate techniques for manufacture of both horizontal and vertical laminations using UF (Urea Formaldehyde) and PF (Phenol formaldehyde) resins have been developed by IPIRTI (Indian Polywood Industries Research & Training) Bangalore. Tests carried out show that material obtained is superior to plantation timber product. Bamboo processing machines were imported from Taiwan and these were found to give good processed material involving less wastage.
Bamboo Mat Board (BMB)
It is the basic material for many other products. In this case woven bamboo mat, is dipped in PH resin binder and then subjected to high temperature curing. Sheets up to 6 mm thickness can be produced in cost-effective mode which provide alternative to polywood panels. The product obtained is water-proof, resistant to insects and to fire. The material possess an excellent physical and mechanical strength properties. The Bureau of Indian Standards have issued I.S. 19958-1994 to cover this product.
Bamboo Mat Veneer Composite (BMVC)
It is a variant of BMB which makes use of veneers from fast growing plantations, used in combinations with bamboo mat for obtaining product for high strength applications, especially for manufacturing of thick panels. Using veneers to the extent of 40 per cent in place of bamboo makes the panels economical for thickness exceeding 6 mm. Relevant Indian Standard for this product is IS 14588-1999.
Bamboo Mat Corrugated Sheets (BMCS)
This is a unique product made from woven bamboo mats. It is moulded under high pressure and high temperature in a specially designed hot process with corrugated plates. Product obtained is waterproof, resistant to decay, termite and insect attack. It is also fire-proof. It possesses high strength and also high resilience.
Bamboo Mat Trays (BMT)
This is a moulded variant of BMB and products are available in the form trays, plates and other items used in household and serve as substitute for plastic products.
Some of the applications accepted by consumers are:
Door-Shutters: It is easy to make low-cost panelled doors by laminating panels of BMBs and stiles and rails of these sections of wood with either gluing or nail gluings. A 7-ply 5 mm thick board is adequate for a single panel. While 3-ply 2.5 mm thick board can be used safely for double door shutter having maximum panel width of 30 cm. The bamboo and board is of two ply and three ply make an excellent skin for hollow core flush doors due to high modules of rigidity and good impact resistance of the board. Doors of thin type used under exterior conditions were found to be in good condition even after ten years’ use.
Grain Storage Bins made from BMB can be used for grain storage. 1.5 tonne capacity grain storage bins made from BMBs has been tested for storing paddy and sorghum. The bins were located in the area having annual rainfall of 100 cm, humidity over 80 per cent and temperature ranging around 28°C. Even in the severe conditions the bins gave good performance.
Packing cases for apples made from BMBs have been found to good service and are economical as the wood content is reduced.
Technology has been developed for
commercial production of BMB, BMVC, BMCS and BMT. The products
obtained have good physical and mechanical properties compared to the
traditional products made from timber wood. Bamboo based products have
been used for making furniture as well.
If the earth attracts each and every thing into its centre, why is water not absorbed completely from seas and rivers?
The earth attracts everything towards its centre, not into its centre. The result is that things pile up on each other. They cannot get into the centre. Another effect of this is that heavier things are closer to the centre, while lighter things are on the outside. Water is much lighter than rock. Which is lighter than some metals like iron. It is believed that the innermost core of the earth is mostly iron. Who knows the innermost part might be uranium, even though it is not as abundant as iron. In any case water would become steam long before it travels deep into the earth because of the high temperature. The centre of the earth is perhaps hotter than the surface of the sun.
You can easily test this phenomenon through an experiment of simple decantation. If you put some mud, soil, sand stones and iron filings in a glass of water. Every thing is attracted towards the bottom. But you will find that after some time the heavier things are at the bottom and the lightest are on top. Indeed this is one of the methods of cleaning muddy water — through simple decantation.
It is said that reading in a moving vehicle affects our vision. Do the objects in the same moving car or bus also have an impact on our eyes?
It is true that reading during a bumpy ride in a car or a bus puts a strain on the eyes. We are continually trying to keep our eyes trained on the words and lines we are reading. If different portions of the text keep jumping across the focus of our eyes the vision processing system of our brain is also challenged. But the problem is not in the fact that the car or bus is moving. It arises because the motion is not smooth. For example in a high-flying modern airplane the flight is so smooth that there is no problem whatsoever in reading to your heart’s content. Remember that even when we read at home or in office or school we are passengers on the spaceship earth whirling through space.
The objects in the moving vehicle have no effect whatsoever. Of course during a bumpy ride, concentrating on small or big things in the vehicle can also be strenuous.
When TV is switched on sound is heard first and picture follows. Why?
The sound is produced using receivers and other circuits that begin to work instantaneously. The transistors and integrated circuits do not have much inertia, in the sense that do not have macro elements to be heated. For generating pictures we use tubes in which electron beams are swept across the fluorescent screen of the picture tube by a scan mechanism. The electron beams are produced by heating tiny filaments to high temperature. This takes a little time. That is the reason for the slight delay in appearance of the picture.
Does lightning affect artificial satellites?
Once you are a satellite you are outside the atmosphere. Lightning is an atmospheric phenomenon. A rocket carrying a satellite through a thundercloud might suffer some electrical malfunction. But that is brief period and you do not launch at that time because of atmospheric turbulence. On the other hand one does worry about electrostatic charge build up on the satellite due the effect of the solar wind and ultraviolet radiation from the sun. This problem can be avoided by proper design.