21-08-2012, 05:06 PM
SOLAR WATER DISTILLATION
SOLAR WATER DISTILLATION.pptx (Size: 341.11 KB / Downloads: 36)
INTRODUCTION
Clean drinking water is the basic necessity for every human being, but about 1.1 billion people in the world lacked proper drinking water. There are many different types of water purification processes such as filtration, reverse osmosis, carbon absorption, but the most reliable process is distillation by solar energy.
General theory of solar distillation
In solar distillation water is evaporated; using the energy of the sun then the vapor condenses as pure water. This process removes salts and other impurities. Solar energy is allowed into the collector to heat the water. The water evaporates only to condense on the underside of the glass. When water evaporates, only the water vapor rises, leaving contaminants behind. The gentle slope of the glass directs the condensate to a collection trough, which in turn delivers the water to the collection bottle.
technical description
The sun's energy in the form of short electromagnetic waves passes through a clear glazing surface such as glass. Upon striking a darkened surface, this light changes wavelength, becoming long waves of heat which is added to the water in a shallow basin below the glazing. As the water heats up, it begins to evaporate.
The warmed vapor rises to a cooler area. Almost all impurities are left behind in the basin.
The vapor condenses onto the underside of the cooler glazing and accumulates into water droplets or sheets of water.
The combination of gravity and the tilted glazing surface allows the water to run down the cover and into a collection trough, where it is channeled into storage.
Solar still design variation
There are many designs for solar stills, and four general categories are:
Concentrating collector stills
Multiple tray tilted stills
Tilted wick solar stills
basin stills
95 percent of all functioning stills are of the basin type
Multiple tray tilted still
A multiple tray tilted still consists of a series of shallow horizontal black trays enclosed in an insulated container with a transparent top glazing cover. The vapor condenses onto the cover and flows down to the collection channel for eventual storage.
TILTED WICK SOLAR STILL
A tilted wick solar still draws upon the capillary action of fibers to distribute feed water over the entire surface of the wick in a thin layer. The water is then exposed to sunlight.
FACTORS INFLUENCING SOLAR STILL OPERATING PERFORMANCE
Climate Factors
Radiation: Its Effect on Efficiency. The amount of solar radiation a solar still receives is the single most important factor affecting its performance. The greater the amount of energy received, the greater will be the quantity of water distilled.
Solar stills produce less distilled water in winter than in summer, which is a problem.
For each 6 [degrees] increase in ambient temperature, the production rate increases by 7 to 8 percent.
Thermal Loss Factors
Production is also associated with the thermal efficiency of the still itself. This efficiency may range from 30 to 60 percent, depending on still construction, ambient temperatures, wind velocity, and solar energy availability. Thermal losses for a typical still vary by season.
Solar Still Design Factors
Slope of the Transparent Cover. The angle at which the transparent cover is set influences the amount of solar radiation entering a solar still. When sunlight strikes glass straight on, at 90 [degrees] to the surface, about 90 percent of the light passes through.
A glass cover that is no more than 5 to 7 centimeters from the water surface will allow the still to operate efficiently. Conversely, as glass-to-water distance increases, heat loss due to convection becomes greater, causing the still's efficiency to drop.
SOLAR WATER DISTILLATION.pptx (Size: 341.11 KB / Downloads: 36)
INTRODUCTION
Clean drinking water is the basic necessity for every human being, but about 1.1 billion people in the world lacked proper drinking water. There are many different types of water purification processes such as filtration, reverse osmosis, carbon absorption, but the most reliable process is distillation by solar energy.
General theory of solar distillation
In solar distillation water is evaporated; using the energy of the sun then the vapor condenses as pure water. This process removes salts and other impurities. Solar energy is allowed into the collector to heat the water. The water evaporates only to condense on the underside of the glass. When water evaporates, only the water vapor rises, leaving contaminants behind. The gentle slope of the glass directs the condensate to a collection trough, which in turn delivers the water to the collection bottle.
technical description
The sun's energy in the form of short electromagnetic waves passes through a clear glazing surface such as glass. Upon striking a darkened surface, this light changes wavelength, becoming long waves of heat which is added to the water in a shallow basin below the glazing. As the water heats up, it begins to evaporate.
The warmed vapor rises to a cooler area. Almost all impurities are left behind in the basin.
The vapor condenses onto the underside of the cooler glazing and accumulates into water droplets or sheets of water.
The combination of gravity and the tilted glazing surface allows the water to run down the cover and into a collection trough, where it is channeled into storage.
Solar still design variation
There are many designs for solar stills, and four general categories are:
Concentrating collector stills
Multiple tray tilted stills
Tilted wick solar stills
basin stills
95 percent of all functioning stills are of the basin type
Multiple tray tilted still
A multiple tray tilted still consists of a series of shallow horizontal black trays enclosed in an insulated container with a transparent top glazing cover. The vapor condenses onto the cover and flows down to the collection channel for eventual storage.
TILTED WICK SOLAR STILL
A tilted wick solar still draws upon the capillary action of fibers to distribute feed water over the entire surface of the wick in a thin layer. The water is then exposed to sunlight.
FACTORS INFLUENCING SOLAR STILL OPERATING PERFORMANCE
Climate Factors
Radiation: Its Effect on Efficiency. The amount of solar radiation a solar still receives is the single most important factor affecting its performance. The greater the amount of energy received, the greater will be the quantity of water distilled.
Solar stills produce less distilled water in winter than in summer, which is a problem.
For each 6 [degrees] increase in ambient temperature, the production rate increases by 7 to 8 percent.
Thermal Loss Factors
Production is also associated with the thermal efficiency of the still itself. This efficiency may range from 30 to 60 percent, depending on still construction, ambient temperatures, wind velocity, and solar energy availability. Thermal losses for a typical still vary by season.
Solar Still Design Factors
Slope of the Transparent Cover. The angle at which the transparent cover is set influences the amount of solar radiation entering a solar still. When sunlight strikes glass straight on, at 90 [degrees] to the surface, about 90 percent of the light passes through.
A glass cover that is no more than 5 to 7 centimeters from the water surface will allow the still to operate efficiently. Conversely, as glass-to-water distance increases, heat loss due to convection becomes greater, causing the still's efficiency to drop.