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[[File:Vaporizer.jpg|thumb|center|upright=4|Figure 1: Vaporizer for the Solar distillation system ]]
[[File:Vaporizer.jpg|thumb|center|upright=4|Figure 1: Vaporizer for the Solar distillation system ]]
</center>
</center>
'''Condenser''' is design to condense vaporization into liquid water.The attention should taken when designing the slope of the roof. If the slope of the roof is too small, water condensation may not able to steam down to the edge of the condenser.   
<center>
[[File:Condenser top.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
</center>
The condenser is supported by 4 screwed on stands at two opposite wall and should be made as thin as possible for the heat exchange ability.
<center>
[[File:Condenser bottom.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
</center>


'''Water groove''' is used to collect condensed water from the condenser as they drip down from the edge of the condenser. For that, the dimension of the groove should be designed so that the position of the groove is under the edge of the condenser.
'''Water groove''' is used to collect condensed water from the condenser as they drip down from the edge of the condenser. For that, the dimension of the groove should be designed so that the position of the groove is under the edge of the condenser.
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The water groove is design to sit on the vaporizer and to provide support to the condenser. To secure the water groove on the vaporizer, a protrusion that fit the inner dimension of the vaporizer is added to the bottom of the groove.  
The water groove is design to sit on the vaporizer and to provide support to the condenser. To secure the water groove on the vaporizer, a protrusion that fit the inner dimension of the vaporizer is added to the bottom of the groove.  
<center>
<center>
[[File:Groove bottom view.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
[[File:Groove bottom view.jpg|thumb|center|upright=4|Figure 1: Water groove of the solar distillation system (bottom view)]]
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</center>


A cut out is placed on the wall of the groove that is tangential to the groove bed for water drainage. Distilled water then would be collected for the solar disinfection process.   
A cut out is placed on the wall of the groove that is tangential to the groove bed for water drainage. Distilled water then would be collected for the solar disinfection process.   
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<center>
[[File:Cut out for water outlet.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
[[File:Cut out for water outlet.jpg|thumb|center|upright=4|Figure 1: Drainage design of the water groove]]
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<center>
[[File:Condenser top.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
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<center>
[[File:Condenser bottom.jpg|thumb|center|upright=4|Figure 1: SODIS with Solar Distillation Schematic Layout]]
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Revision as of 21:04, 2 April 2010

Template:425inprogress

Solar Water Disinfection System with Solar distillation

Introduction

Similar to Solar Water Disinfection System (SODIS) initiated by Professor Aftim Acra, Solar Water Disinfection System with solar distillation is a water purification system at household level based on solar radiations with additional use of solar heating. Since SODIS is only ideal to disinfect small quantities of micro-biologically contaminated water of low turbidity, a solar heated distillation process is combined with the conventional SODIS. Contaminated water is first distilled by using a solar heated low-temperature distillation system to remove any non-volatile solid impurities such as salts, sediment and heavy metals. However, the distilled water is not drinkable since the water may still contain some pathogenic microorganisms . To address this problem, the distilled water is then contained in clean and transparent PET bottles or glass bottles and are exposed to the sun light for a certain amount time (depending on the intensity of the sun light) allowing the radiations to deactivate any waterborne pathogens[1] in the contaminated water. Solar water disinfection is an effective way to purify drinking water as it is recommended by World Health Organization[2]. It uses only solar energy and can be built using only recycling materials, thus, the system is environmentally sustainable.

Theory

Water distillation is a physical process that filter solid impurities out of fluid based on differences in the volatility. At a given temperature, substances with higher volatility (water in this case) vaporizes more readily than substances(solid impurities) with lower volatility. The water vapor would be directed to a cool region which would condense the water vapor back into liquid state, leaving all the non-volatile solid impurities such as salts, sediment and heavy metals behind. However, the distilled water may not be suitable for drinking since it may still contain some volatile organic compounds[3] or/and pathogenic microorganisms (bacteria, viruses and in some cases protozoans) The rate of vaporization is proportional to the vapor pressure and the fluid temperature.

The principle of SODIS is based on Ultraviolet water treatment . It uses two components of the sunlight for the water disinfection process :Ultraviolet radiationand infrared radiation. UV-A radiation(wavelength 320-400 nm) interacts with the DNA, nucleic acids and enzymes of the organic cell, destroys the cell molecular structures which leads to cell deaths. UV-A radiation also reacts with oxygen dissolved in the water producing highly reactive forms of oxygen (oxygen free radicals and Hydrogen peroxide], that can help the germicidal process. Infrared radiation is a long-wave form of sun radiation, it can be felt as heat, as it is responsible for raising the fluid temperature. Studies had proven that 99.9%[4] of microorganisms within water are eliminated if the water is heat heated to 50-60°C for one hour. In order to disinfect contaminated water for drinking, it is recommended to expose the contaminated water to full sunlight using clear Polyethylene terephthalate (PET) bottles for 6[5] hours.If water temperatures exceed 50°C, one hour of exposure is sufficient to obtain safe drinking water.When the weather is cloudy for more than 50% , the contaminated water need to be exposed for 2 consecutive days. The treatment efficiency can be improved by raising the fluid temperature and exposing the contaminated water to additional reflecting surfaces such as aluminium- or corrugated iron sheets.


Design

Solar Energy Collector is a device that collects solar radiation and converts it into thermal energy for the SODIS and the solar distillation process. The solar energy collector is composed of columns of painted black pop aluminum can, a frame to hold the cans and a ventilation for the heat transportation. Before all the cans are glued together to form a collected column, the top and the bottom of aluminum can is need to be removed. When placed under the sunlight, the columns absorb the solar radiation and heat is convected to the air inside the columns. Due to difference in the air density , warm air would raise to the top of the columns and cool air would be sucked into the columns from the bottom. The warm air flow is then collected at the top of the columns. The columns are painted in black to enhance the radiation absorbability and the size of the columns can be varied for different requirement.


Figure 1: SODIS with Solar Distillation Schematic Layout


Solar Distillation system is similar to the conventional water distillation system. It is composed of a vaporizer that holds holds the water, a vapor collector that collects and condenses steam and a water collector that collects distilled water. The rate of vaporization is proportional to the fluid surface area and the fluid temperature. The improve the performance of the still, the vaporizer should be made as large as possible and at the bottom of the vaporizer, there are some serpentine gas channels where warm air flow is directed into. Due to the temperature difference between the water and the air flow, heat is transfered into the vaporizer, causing the water temperature to raise, thus, speed up the vaporization process. Other methods such as using a thermal conductive materials, painting the vaporizer to black and using some reflective surface to concentrate the radiation can be used to improve the performance of the system.


Figure 1: SODIS with Solar Distillation Schematic Layout


The evaporation rate can be calculated as below [6]:

where

  • Q is the daily output of distilled water ()
  • is the efficiency of the still, as the fraction of the energy transfered to the water to the total absorbed solar energy.
  • G is the daily global solar irradiation (see solar insolation) (). The typical solar insolation at the Earth's surface is approximately 1,000 [7] [8] watts per square meter for a surface perpendicular to the Sun's rays at sea level on a clear day. Based on the assumption of 5 hours of sunlight per day, the daily solar irradiation is approximately 18 MJ/m^2.
  • A is the total fluid surface area.
  • S is the thermal energy obtained from the solar energy collector. It can be calculated using Enthalpy:
ΔH = HfinalHinitial = Cp x (T2 - T2)

where

  • ΔH  is the enthalpy change.
  • Hfinal is the final enthalpy of the system, expressed in MJ.
  • Hinitial is the initial enthalpy of the system, expressed in MJ.
  • T2 is the flow outlet temperature of the solar energy collector in Kelvin scale.
  • T1 is the flow inlet temperature of the solar energy collector in Kelvin scale.


Solar water disinfection system takes the distilled water from the solar distillation system and disinfects it to drinkable water with utilization of solar radiation. To improve the efficiency of the disinfection system, reflective surfaces can be used to intensify the solar radiation toward the contaminated water. It is recommended by WHO to expose the contaminated water to full sunlight using clear Polyethylene terephthalate (PET) bottles for 6 hours.When the weather is cloudy for more than 50% , the contaminated water need to be exposed for 2 consecutive days. Another way to improve the system performance is to increase the fluid temperature. According to study, if water temperatures exceed 50°C, one hour of exposure is sufficient to obtain safe drinking water. This is when the solar energy comes in place. A portion of the thermal energy collected from the solar energy collector is directed to the heat up the bottled distilled water.

Solar Energy Collector

The construction of the solar energy collector starts with preparing the aluminum cans. The materials and tools required are shown as follow:

  • Wire cutter and for
Figure 1: SODIS with Solar Distillation Schematic Layout
Figure 1: SODIS with Solar Distillation Schematic Layout


Figure 1: SODIS with Solar Distillation Schematic Layout
Figure 1: SODIS with Solar Distillation Schematic Layout


Figure 1: SODIS with Solar Distillation Schematic Layout


Figure 1: SODIS with Solar Distillation Schematic Layout

Solar Distillation System

The solar distillation system consisted of 4 main parts: vaporizer, condenser, water groove and channel manifold. The design shown below is for concept demonstration. It can be manufactured with metal sheet and can be resized for difference needs. Thermal conductive materials such as aluminum, cooper or zinc are recommended for manufacture to maximize the thermal conductivity of the system.


Vaporizer is used to contain and vaporized contaminated water. After all the water has been vaporized, residuals in the vaporizer must be removed before loading another tank of contaminated water.

Figure 1: Vaporizer for the Solar distillation system



Condenser is design to condense vaporization into liquid water.The attention should taken when designing the slope of the roof. If the slope of the roof is too small, water condensation may not able to steam down to the edge of the condenser.


Figure 1: SODIS with Solar Distillation Schematic Layout

The condenser is supported by 4 screwed on stands at two opposite wall and should be made as thin as possible for the heat exchange ability.

Figure 1: SODIS with Solar Distillation Schematic Layout



Water groove is used to collect condensed water from the condenser as they drip down from the edge of the condenser. For that, the dimension of the groove should be designed so that the position of the groove is under the edge of the condenser.

Figure 1: Water groove of the solar distillation system

The water groove is design to sit on the vaporizer and to provide support to the condenser. To secure the water groove on the vaporizer, a protrusion that fit the inner dimension of the vaporizer is added to the bottom of the groove.

Figure 1: Water groove of the solar distillation system (bottom view)

A cut out is placed on the wall of the groove that is tangential to the groove bed for water drainage. Distilled water then would be collected for the solar disinfection process.

Figure 1: Drainage design of the water groove



Figure 1: SODIS with Solar Distillation Schematic Layout
Figure 1: SODIS with Solar Distillation Schematic Layout
Figure 1: Solar distillation system assembly

Solar Water Disinfection System

Figures

Materials Selection

  • Paints
  • Transparent, smooth surface PET bottle
  • Concerns about PET bottle safety under UV light

Limitation

References

Template:Reflist

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