Another classic benefit of solar energy is the ability to pasteurize water using the sunshine, either by using a classic solar cooker or by using non-solar cooker devices.
The basic prerequisite is to elevate the temperature of water in a container or storage device to at least 149 º F (65 º C) for a period of least 6 minutes.
To successfully pasteurize water in a solar cooker one would need to carefully and accurately measure that the time-temperature relationship of 149 º F (65 º C) for a period of least 6 minutes had been attained.
In this regard the WAPI (Water Pasteurization Indicator) concept was first developed in1988 by Dr.
Fred Barrett (US Department of Agriculture) and in 1992, Dale Andreatta, a graduate engineering student at the University of California, Berkeley, improved the designed and developed the current WAPI.
The WAPI is a polycarbonate tube about 7.
5 cm (3 inches) in length, sealed at both ends, and partially filled with a soybean fat which melts at 69° C (156°F).
It also has a nylon thread and stainless steel washer attached that allows the tube to be inverted once the fat has melted and then subsequently cooled and solidified.
The tube fundamentally is buoyant, but is weighed down by the washer.
The solar cooker is then employed and potentially contaminated water in a closed water container is then heated using sunshine.
When a temperature of 65 º C (149 º F) is attained after a couple of hours and that temperature has been maintained for 6 minutes, the fat melts and migrates to the bottom of the WAPI, indicative of solar pasteurization having been successfully completed.
Solar pasteurization can also be employed using plastic containers (bottles) without using a solar cooker.
This technique is referred to as SODIS (short for Solar Water Disinfection), and was an approach initially researched and developed by Professor Aftim Acra at the American University of Beirut in the early 1980s and is currently an initiative of Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology.
Fundamentally SODIS is a technique that disinfects water using sunlight and plastic polyethylene bottles, glass bottles or clear plastic bags.
The principle is the contaminated water is filled into a transparent PET bottle, glass bottle or clear plastic bag and then exposed to direct sunlight for a minimum of 6 hours, preferably during the hottest part of the day.
Of vital importance is that it must be a cloudless day for the full 6 hours and at the hottest possible time of the day.
The basic prerequisite is to elevate the temperature of water in a container or storage device to at least 149 º F (65 º C) for a period of least 6 minutes.
To successfully pasteurize water in a solar cooker one would need to carefully and accurately measure that the time-temperature relationship of 149 º F (65 º C) for a period of least 6 minutes had been attained.
In this regard the WAPI (Water Pasteurization Indicator) concept was first developed in1988 by Dr.
Fred Barrett (US Department of Agriculture) and in 1992, Dale Andreatta, a graduate engineering student at the University of California, Berkeley, improved the designed and developed the current WAPI.
The WAPI is a polycarbonate tube about 7.
5 cm (3 inches) in length, sealed at both ends, and partially filled with a soybean fat which melts at 69° C (156°F).
It also has a nylon thread and stainless steel washer attached that allows the tube to be inverted once the fat has melted and then subsequently cooled and solidified.
The tube fundamentally is buoyant, but is weighed down by the washer.
The solar cooker is then employed and potentially contaminated water in a closed water container is then heated using sunshine.
When a temperature of 65 º C (149 º F) is attained after a couple of hours and that temperature has been maintained for 6 minutes, the fat melts and migrates to the bottom of the WAPI, indicative of solar pasteurization having been successfully completed.
Solar pasteurization can also be employed using plastic containers (bottles) without using a solar cooker.
This technique is referred to as SODIS (short for Solar Water Disinfection), and was an approach initially researched and developed by Professor Aftim Acra at the American University of Beirut in the early 1980s and is currently an initiative of Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology.
Fundamentally SODIS is a technique that disinfects water using sunlight and plastic polyethylene bottles, glass bottles or clear plastic bags.
The principle is the contaminated water is filled into a transparent PET bottle, glass bottle or clear plastic bag and then exposed to direct sunlight for a minimum of 6 hours, preferably during the hottest part of the day.
Of vital importance is that it must be a cloudless day for the full 6 hours and at the hottest possible time of the day.