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Dew Harvesting


By Editor-In-Chief,Technomic Review


Many arid regions in the world suffer from chronic shortage of drinking water. Some of them which are on the coast get dew during many nights in an year. Harvesting of such dew can provide additional drinking water for those regions. Late Prof. Girija Sharan and his team have built a variety of dew harvesting plants in the Kutch region of Gujarat, India to demonstrate that the above idea is feasible.


Many areas of the world suffer from acute shortage of drinking water. The shortage occurs because the conventional sources of water such as rivers, lakes, tanks, and wells are non-existent, inadequate, or polluted. In such cases, one essential means of survival for the affected people is to tap unconventional sources of water, if possible.  Collection of water from such sources is not easy, and involves technical innovations. This article describes one such innovation; the unconventional source is atmospheric moisture,  the geographical area where the innovation has been used is the Kutch region of the Gujarat State in India, and the innovators are late Professor Girija Sharan and his colleagues at IIMA and  Dhirubhai Ambani Institute for Information and Communication Technology (DAIICT), the two Institutes at which Girija Sharan worked during the period of the above innovation.

  Water Scarcity in the World
  1. No. of people who lack safe water = 1.8 billion
  2. No. of people with no access  to sanitation = 2.4 billion
  3. No. of people dying from water related diseases  annually = 840,000
  4. Average time for which women and children walk every  day to get drinking water in some areas =  4 hours
 

Kutch district suffers from acute lack of water, and is classified as a desert. However, its southern and western parts are close to the coast, and the air there is humid, which means the air contains some water vapour, the proportion of the water vapour depending on the season, place, temperature and a variety of other factors.  At night, this moisture condenses in to water droplets, on surfaces near the ground, which are cooler than the surrounding air. Such drops are called dew.

Dew condensing plants

Plates of suitable material can capture the dew in appreciable quantities, which can be collected in

  Dew Condenser
  1. A metallic or plastic plate insulated on the underside
  2. Capable of losing heat at night by radiation
  3. Causes dew to be formed when it reaches dew point
  4. Set at an inclination to horizontal. 
 

containers, and further processed to get drinking water. The condenser plate should be made of a material which can cool fast at night when facing cloudless open sky, and should be light in weight. Typically the plate consists of two layers: the top one is the surface on which the moisture condenses, and is made of plain metal or special plastic; the bottom one is a thermal insulator, like 25 mm thick styrene foam. The surface of the condenser is set at an inclination to the horizontal, so that it faces the sky for cooling by radiation, while at the same time permitting the condensed water to flow down into the water storage unit (Sharan, 2006).

Girija Sharan and his colleagues have worked for more than ten years to design and install a variety of dew harvesting plants. They have talked to professional and lay people in and around Kutch, investigated into literature on similar attempts, experimented with various materials and configurations for condensing the atmospheric moisture, set up pilot production units in Kothara, a village 20 KM from the coast,  to demonstrate the technology and gain acceptance of the local population.

During the above period, the innovators experimented with various materials for dew condensation, various locations for installation of condensers, and various configurations of the equipment. They have produced various designs of dew harvesting systems, each meant for a different site of installation, and each having a different capacity of water production.

Finally, in 2014 they claimed that their latest system produced water safe to drink, comparable in quality and price to the water produced by the Reverse Osmosis technology that some residents of Kothara currently use. The production plant consistsof a condenser field, water storage unit, and a water filtering system. Once the plant is made complete with a packaging unit, the water produced would be ready to sell. The water produced by the plane is tested to be safe to drink, and is affordable (Sharan and Roy, 2014).

Every drop of water counts

The severity of the drinking water problem in the above region can be understood by the fact that, women and children routinely need to walk a few kilometres to the nearest water source to fetch water every day. The effort in walking to the water source and carrying the weight of water leads to health problems in women children. The time needed for the above activity cuts in to the time that they should spend on other normal activities like play and studies. Rain fall in such regions is very scant;

  
 

Figure 1:  Dew plant Frame (Source: Photograph sent by  Sharan to Venkata Rao)

 

the average rainfall in Kutch is estimated to be less than 400 mille-meters an year, and the evaporation is much higher, about 2000 mm per year. As a result, the few tanks that are the only surface water sources go dry often. Ground water is also equally undependable, because the water table is getting depleted fast, and its quality poor. A few families, who can afford it, get their drinking water through Reverse Osmosis plants installed in their houses. Some buy water from a vendor. Others get their water supply from water tanker trucks that visit each village aperiodically. The cost of such water is borne by public authorities. About 150 villages around Kothara, the place where Girija Sharan and his team conducted most of their experiments, have no water source of their own. They depend solely on water tankers for their drinking needs. Therefore, in such places, every drop of water counts.

In the above context, the contribution of Girija Sharan and his team is to be highly valued, because the dew provides a supplemental source of drinking water to the already stressed existing sources. It is the dire need of the Kutch region for additional drinking water that motivated Prof. Sharan to initiate the above research programme, and to continue with it relentlessly for more than a decade. That their innovation is considered commercially viable is good news; even otherwise, their efforts are highly commendable, because, now that the team has demonstrated convincingly the feasibility of harvesting dew, their ideas can be scaled up and commercialized by other agencies. Their innovation is no less significant than the invention of a lifesaving drug.

The innovators at work

The entire dew harvesting project from the origin of the idea to its successful demonstration was constituted by a series of interesting events (Dixit, Sharan, 2007).

The idea for developing dew harvesting systems was triggered in Girija Sharan’s mind, one day in 2000, when he accidentally noticed dew condensation in Kutch. At that time, Prof. Sharan was in Kothara on a project to install Green Houses, and was already familiar with the severity of the drinking water shortage there. He thought that the problem could be alleviated by dew water harvesting.

While he was confident that his idea would work, heidentified two practical problems:

  1. In order for the dew condenser to become viable, the quantity of dew formation in a year should be appreciable; at that time, no reliable estimates were available on the amount of dew formation in a year in Kutch. Opinions varied widely: some felt the dew was significant, whereas some others thought otherwise.
  2. Even if dew could be successfully harvested, acceptability of water from dew was a major issue. Most people in Kothara thought it was not safe for drinking.

Figure 2: Dew Condensation Plant (Source: Photograph sent by Sharan to Venkata Rao)

Prof. Sharan collected data on dew condensation, over several nights, on the roof of the green house that he was experimenting with and concluded that the quantity of dew condensation was significant. In a year, there were 100 nights during which dew formed, and these occurred during the nine month period of September to May. Funds from Cummins Foundation for the Green House project could be partly used for the data collection. However, for further work, more funding was needed.

In the meantime, literature search revealed that in 1990’s useful work on dew condensation was reported from France, Israel, and Chile. Interestingly, some experimenters tried to developed materials that mimicked those of the desert beetles back. Prof .Sharan could not obtain details on the materials, as the material was developed for a company, and hence confidential. Nevertheless, hewas significantly benefitted by a report by Nilsson,T. (1996) that the PETB film, a film made of polyethylene mixed with small amounts of titanium oxide and barium sulphate would make a good surface for the condenser.

With funding of Rs 1,92,000 (US$ 2,870) from the Gujarat Energy Development Board, Girija Sharan conducted further experiments to study the effect of various materials for condensation surfaces, the effect of the orientation of a surface, and the effect of ambient conditions. A little later, in 2004, Prof. Sharan won, in the innovative ideas competition, a cash prize of US $ 20,000 from the World Bank, for his proposed work on dew harvesting. The prize money came in quite handy for further experiments.

A team of three people, consisting of an agricultural engineer, a field worker, and Prof. Sharan, worked on experimenting with various types of condensers. First they experimented with 24 condensers each having a surface area of 1 square-meter, and then with larger prototypes with surface area of 18 square-meters.

 

Figure 3: UV stabilized ribbons (Source: Photograph sent by Sharan to Venkata Rao)

 

The team faced two additional difficulties in building their experimental systems: The plastic film that formed the condenser surfaces did not stick well to the insulating material, when conventional adhesive was used; second, the size of the plastic film needed by them was much smaller than the minimum size that the plastic film vendors were willing to sell. The first problem was overcome by using special ribbons, made of UV stabilized plastic, which were already in use in their work on green houses. The second was solved when the president of the plastic processors association intervened on behalf of Prof. Sharan in his negotiations with the vendors, and convinced them to be flexible, as the current project was for a worthwhile cause.

At this stage, the team issued three designs meant for different uses: the first was for domestic use, and was to be installed on existing house roofs; the second was meant for community use and was to be installed on an open ground, or on waste lands near the coast, low hills or stable embankments. The third was to be built on large properties like fodder ware houses, or schools, with metal roofs usually made of galvanized iron. The domestic system could collect twenty litres of water per night, whereas the community systems could collect upto 100 litres per night.

 

Figure 4: Dew Water (Source: Photograph sent by Sharan to Venkata Rao)

 

Two systems, one in a school, and the other in a temple were built to demonstrate the idea of dew harvesting to the local residents. The principal of the school was first convinced when he saw the system in the temple in operation. He then allowed the system to be installed in his premises, and convinced the locals that the water produced by it was fit for drinking, by actually drinking it himself in front of a crowd of onlookers.

The innovators participated in several local fairs by putting up stalls on dew harvesting, and the stalls caught the attention of media, through which they got free publicity.

 

 

Conclusions from the Experiments

 

Places for Dew condenser Installation

  1. Open grounds
  2. Existing roofs
  3. Embankments
  1. Sites for installation: The site should be characterized by high humidity, clear night skies, light winds and low air pollution for a significant part of the year. The harvesting system could be installed at or near user’s homes, or in waste lands near coasts.
  2. Elevations at which to install: The condensers installed at ground level, which is just 2 or 3 meters above the ground level, have higher yield of water than those installed at roof level, which is 5 to 6m above ground.
  3. In Kutch, condensers facing north and west have better yield than those with different orientations.
  4. Condenser Material: Thin metal sheet or plastic film (poly carbonate sheet, fibre reinforced plastic, Polyethylene film, the last being the most affordable) insulated on the underside are the most suitable. Metal sheets are more expensive and less output yielding than plastic ones. Among the metal ones, galvanised iron and aluminium are most effective. Metal sheet is to be used only if it forms an already existing roof, or meant for additional uses; by itself, it is not to be preferred.

Costs and Benefits

The total cost of the system incurred an installation cost of Rs. 1.5 million (US $ 22,000).

The installation cost was split between the four components of condenser and panel material, frame mounting, civil works, and site supervision:

 

16.7% for condenser panel material, fabrication etc.

13.3% for mounting frames

54% for civil works

16% for site supervision

 

The rate of production of water was estimated to be 500 litres/day.

Assuming that the per capita drinking water requirement is 4 litres/day, the plant can meet the drinking water requirements of 125 people, which is of 1/60th of the population of Kothara village.

The operational cost is 0.55 KWh/litre, which compares reasonably with Rs. 0.5/ litre, the cost of existing RO water supply. The quality of the water meets the WHO standards for drinking water.

According to Times of India (Tewari , 2015),In just four months, 13,500 litres of drinking water is produced and the cost for this is Rs. 30 per 20 litre container”. Thus, the quality of water produced and the operational cost of the above system are comparable to existing sources.  The real issue is the installation cost of large systems.

This innovation is the first effort in India to produce drinking water from dew, although dew harvesting has been attempted and is actively being pursued in other parts of the world. The condensers are the largest among those existing in the world today. The quantity of condensation is quite appreciable, unlike that in other condensers. The technology developed can be implemented close to the homes of consumers, sometimes right on their roof tops. If an existing roof is used for installing the system, the extra investment needed is minimal. Commercial cost of extracted water per litre is comparable to that of existing RO systems. It is hoped that the installation cost would be brought down by further innovations in the design of the systems, and by scaling up the plant size.

References

  1. Dixit, M., Sharan, G. 2007. Leveraged Innovation Management: Key Themes from the Journey of Dew rain Harvest Systems; W.P. No.2007-01-04, Indian Institute of Management, Ahmedabad, January 2007.
  2. Sharan, G., Roy A. K., 2014. Production of High Quality Potable Water for Sale fromAtmospheric Moisture in Coastal Areas of Semi-Arid North-WestIndia,2nd International Conference on Arid Lands Studies Innovations for sustainability and food security in arid and semiarid lands, 10-14 September 2014.
  3. Tewari ,Ankur, ,2015. Getting drinking water from humidity in this Kutch village, http://timesofindia.indiatimes.com/city/ahmedabad/Getting-drinking-water-from-humidity-in-this-Kutch-village/articleshow/49029953.cms, TNN, Sep 20, 2015, 03.23 AM IST, (accessed on 15 March 2016).
  4. Sharan, G., 2006. Dew Harvest: To Supplement Drinking Water Sources in Arid Coastal Belt of Kutch, Foundation Books Pvt. Ltd., Bangalore.
  5. Nilsson, T. (1996). Initial experiments on dew collection in Sweden and Tanzania,Sol. Energy Mat. Sol. Cells, Vol. 40, 23-32.

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June 03,2016

The content is very interesting, however, the writing style seems to focus excessively on the struggles of the team that worked on this project. Somewhere, I had thought that the objective of this project was to focus on being educational and not as much about storytelling.

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