Eco Harvester

Start - Finish:

June 2008

Project Members

Wai Ting Chan, Dan O’Connell and Yingying Seow

Keywords:

water, harvester, drinking

Useful Websites:

Story bank

Aims & Objectives:

Science has contributed immensely to human progress and to the development of modern society. However, ninety-five percent of the new science in the world is created in countries comprising only one-fifth of the world's population (Moreno-Borchart, 2004). As these countries continually progress in their technical innovation, allowing them to achieve enormous advancement in both economic development and standards of living. This trend has caused a continually enlarging gap between the wealthy and poorer countries, as the latter do not have the monetary resources to invest in technology development.

Many poor families in developing countries are still deprived of services that are considered essential and basic in many countries, such as water, sanitation, energy, education and health – as well as lacking adequate shelter. It is often the case that their livelihoods are reliant upon their skills to manipulate the local resources. Therefore, they are most vulnerable to changes in the climate, natural disasters, resource depletion and the spread of infectious diseases.

Research projects such as Story Bank, funded by the Engineering and Physical Sciences Research (EPSRC), has documented the local community life of an Indian village, Budikote, mainly in the form of multi-media. The aims of the archiving are to develop more globally inclusive technology for information sharing, as well as providing insights into the lives and needs of the villagers, to educate and inspire engineers and designers, which has subsequently provided the context for this project.

This project explores the needs of the villagers highlighted by the Story Bank, to develop a concept solution for the most pressing need.

Project Abstract

Water is one of the main prerequisites of life on earth. However, fresh clean water is not an abundant resource in some parts of the world. The lack of access to clean water and sanitation leads to preventable diseases and death for many. More than 2.2 million people, mostly in developing countries, die each year from diseases associated with poor water and sanitary conditions. (Azapagic et al. 2004)

In Budikote, India, the majority of the villagers do not have water supply directly to their homes. They have to retrieve water from bore-wells with containers to their houses for drinking and domestic purposes. As water is heavy to carry, the women would minimise the amount trips they have to make to and fro, by bringing their cloths and vessels to wash in the bore-wells or the tanks.
The weather in Budikote is hot and dry most of the year. Water can be scarce at certain times of the year. As consequence, villagers attempt to dig their own bore-wells, risking contamination with fluoride and heavy metals if not dug properly.

This project proposes a water generating solution to ease the current water problems in Budikote. This product provides a complimentary solution to the water pumps in the village, as the supply of which is limited, inefficient and often ineffective during the drier seasons.

The water generating system uses a salt solution to collect the moisture from the air, and then to be extracted for personal consumption via solar re-generation. The preliminary experiments show that the salt can generate 142% of its own weight in water, and perhaps has potential to generate more.

With the traditional sources of water becoming less reliable and more polluted, this radical but proven approach of extracting water from air could hold the key to the future of water management, providing a dependable source of water for generations to come.

Development and Experimentation

The final design adapts the shape of the water pots the villagers currently possess. The conical part of the collector can be retained, and a much larger volume used for condensing the water vapour.

The two handles on the side of the product serve a dual purpose, both as carrying handles and as a means of delivering the water collected by the condensing surfaces to the water container below. Each of the collecting surfaces has a small hole that allows liquid water to travel down to the level below, and eventually collect on the upper surface of the lowest pink fin where the handle drains the water into the container. This design allows a larger amount of collecting surfaces to be used, maximising the surface area for the vapour to condense. The surfaces are also overlapped, creating a convoluted path that the vapour has to travel. This increases the probability of it making contact and condensing on one of the cool surfaces.

As with the earlier versions of the design, natural convection is used to move the air around the internal areas. The lower areas of the collector apparatus absorb more of the sun’s radiant energy and increase the air temperature inside the assembly. This increase in temperature evaporates the water in the desiccant, and then the air then rises with the water vapour into the upper part of the collector. This draws humid air in from the external environment and moves it across the desiccant in the trays, with the chemical absorbing the water vapour in the air. This air is then heated by the radiant heat from the walls of the lower chamber, starting the cycle again. Once the air from the lower area has moved up into the upper area of the assembly, it hits the condensing surfaces as described above.

In order to provide quick access to the trays containing the desiccant chemical, the collecting assembly (the black and pink sections) can be quickly removed by a simple twist and lift unlock mechanism. While access to the chemical will not usually be needed during normal operation, the chemical will occasionally need to be serviced or even replaced.

Results

The final design of the product will be evaluated against the PDS to determine if it has fulfilled the requirements specified at the start of the project. The results of the evaluation are summarised below; a green highlight indicates that the design has met the specifications, a yellow highlight the design has only partially met the specifications and red means it has not been fulfilled. The design has met all the compulsory requirements listed in the PDS and have met majority of the desirable requirements.

In terms of functionality, the design has eliminated the need for the transportation of water from a well or a water pump as it now serves as a source of water for the user. The use of liquid desiccant as the foundation of the design is a well established technology typically applied in ventilation systems for air conditioning. The radical application of the technology to water generation, albeit new, has been backed with positive experimental results that have shown up to 100% of its own weight in water can be extracted from the liquid desiccant, Magnesium Chloride.

Once the product is manufactured, no electricity is required for operation as it is driven purely by solar energy. The distillation of water from the salt solution provides a constant supply of fresh drinkable water, whilst the process is not instantaneous, the experiments in Section 13 proves even at Budikote’s most extreme low humidity, 38% of the salts weight in water can be regenerated from the salt, and 142% at higher humidity levels.

The continuous nature of the process coupled with its ability to operate under low humidity means it is able to provide a constant supply of water to the user, without having to replace the salt. The product is simple and intuitive to use as little involvement is required by the user during the water regeneration process, except pouring the water out from the collection bowl once water has been collected. Initial training maybe required to educate the user on the handling of the system, which would be keeping the product level and attaching and removing the lid after which the actual use of the product should not require further training. Finally, MgCl2 found abundantly in seawater is innocuous and poses little health and safety issues during the operation of the product.
 

Conclusions

The water issues observed in Budikote are not just specific to the village but to many other rural places where the infrastructure has not been established to support the needs of the people. The United Nations has recognized access to water as a basic human right, stating that water is a social and cultural good, not merely an economic commodity (Sampath et al., 2008). At present more than one billion people on earth lack access to fresh drinking water. By the year 2025 the demand for freshwater is expected to rise to 56% above what currently available water can deliver, if current trends persist (Barlow, 2003).

The use of hygroscopic salts (Concept W2) was first proposed as a response to the limited water supply in Budikote but as can be seen from the evaluation table, it not only addresses the issue with supply but also with quality and transport. If the potential of the technology is optimised to reach its full potential, the villagers and possibly others in drought stricken areas would be able to generate they own water from an untapped resource that is in abundance, water vapour.