Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.

Difference between revisions of "Solar distillation"

From Appropedia
Jump to: navigation, search
Line 1: Line 1:
{{topic header||Solar distillation}}
+
{{topic header| default.png | Solar Distillation}}
 +
 
  
 
{{merge to|Solar stills}}  
 
{{merge to|Solar stills}}  

Revision as of 18:08, 16 December 2012


Default.png    See also the Solar Distillation category.
for subtopics, how-tos, project pages, designs, organization pages and more.



Merge-arrow.gif
It has been suggested that this page or section be merged into Solar stills. (Discuss).


Introduction

Solar Still Distilled Water.jpg

Solar distillation is the use of solar energy to evaporate water and collect its condensate within the same closed system. Unlike other forms of water purification it can turn salt or brackish water into fresh drinking water (i.e. desalination). The structure that houses the process is known as a solar still and although the size, dimensions, materials, and configuration are varied, all rely on the simple procedure wherein an influent solution enters the system and the more volatile solvents leave in the effluent leaving behind the salty solute behind[1].

Solar distillation differs from other forms of desalination in its comparatively low energy needs due to the use of free energy as opposed to the much more energy-intensive methods such as reverse osmosis, or simply boiling the water.[2][3]

History

The earliest onset of solar energy use to desalinate or distill water is widely accredited to Aristotle during the fourth century B.C.E.[4][5][6][7] Earlier attributions reference the Bible & Moses’ use of a piece of wood to remove the “bitterness” from water (Exodus 15:25, English Standard Version). The first documented account of solar distillation use for desalination was by Giovani Batista Della Porta in 1958.[4]However, the Father of solar distillation is Carlos Wilson, the creator of the first modern sun-powered desalination plant, one built in Las Salinas, Chile


Design

The main design challenge is keeping the distiller airtight. If not airtight, efficiency drops severely.[verification needed]

Often a shallow trough is used, painted black, and flooded. A slanted pane of glass covering, allowing condensed water vapor to slide down into an output channel. Expect 1 gallon per day per square meter of glass.

Another approach is molded plastic, e.g. the Watercone (see below). This has the advantage that it is can be more easily made airtight, and mass production should make it affordable.

Modifications

Cost has been a major barrier to implementing this. Recent work using CPCs has shown that solar distillation can be economically viable in some locations.

Watercone

The Watercone®[1] is a solar powered water desalinator. It is claimed to be simple to use, lightweight and mobile. It is designed to produce 1.5 liters a day.

The WATERCONE® is a long lasting UV resistant Poly Carbonate product and can be used up to 5 years daily. The material is non-toxic, non-flammable and 100% recyclable. The black pan for the saltwater is already made out of 100% recycled PC. Even when the WATERCONE® becomes old and tarnished, it can still be used to collect rain water, as a roof panel or container for other goods.
The Watercone® project is looking for investors and companies to initiate mass production tooling and distribution. So the Watercone can be manufactured for a lower price and become affordable to the people in need... Single products are not available at the moment![2]

Cost: The planned price is below € 20,[3]. Solar distillation needs to become much cheaper than this before it can achieve widespread use by the poor. The website states that this works out cheaper than bottled water at 50c per liter once it is used for a number of months; however the target market cannot afford to buy bottled water, so this is not a useful comparison. If they do buy water, it is more likely to be from water refill stations which charge around 3 c per liter in major cities in Asia. In isolated areas, the costs increase a lot, but they would need to increase far beyond 3c per liter to justify the investment by a poor person or family - especially when it would be difficult to guard against theft. Thus it looks like they’re only useful where safe water is exceptionally expensive, or simply unavailable. Even then, other options for purifying the water would need to be weighed up. If these things were mass-produced for more like 1 euro or less each, they might be an option for widespread use - and this would be a more reasonable price for mass-produced pieces of molded plastic (even if they are very cleverly designed pieces of molded plastic).

Watercone external links

Solar distillation in Mexico

Florence Cassassuce, of La Paz, Mexico, who invented a five-gallon bucket that can purify several days' worth of water in four minutes.

She was one of 18 people listed as one of CNN Heroes finalists in 2007.

This is her site.

[4]

Interwiki links

External links

Project links

References

  1. (2008). Desalination, a national perspective. National Research Council of the National Academies.
  2. Abu-Arabi, M. (2007). Status and prospects for solar desalination in the MENA region. Solar Desalination for the 21 st Century, 163-178.
  3. Paton, C., & Davies, P. (2006). The seawater greenhouse cooling, fresh water and fresh produce from seawater. In The 2nd International Conference on Water Resources in Arid Environments, Riyadh.
  4. 4.0 4.1 Delyannis, E. (2003). Historic background of desalination and renewable energies. Solar Energy, 75(5), 357-366.
  5. Tiwari, G. N., Singh, H. N., & Tripathi, R. (2003). Present status of solar distillation. Solar Energy, 75(5), 367-373.
  6. Velmurugan, V., & Srithar, K. (2011). Performance analysis of solar stills based on various factors affecting the productivity—A review. Renewable and Sustainable Energy Reviews, 15(2), 1294-1304.
  7. Gordes, J., & McCracken, H. (1985). Understanding Solar Stills. Volunteers in Technical Assistance (VITA).

This topic needs a topic expert