Seems counterintuitive, but solar energy can be harnessed to make ice cubes. An electricity-free alternative to refrigeration and air-conditioning, solar icemakers use the sun's heat during the day to drive a chemical reaction that separates a liquid refrigerant from a solid absorbent. The solid absorbent stays in the solar collector, while the liquid refrigerant is driven away and stored in a separate component called the evaporator. At night, the chemical reaction runs in reverse; the solid absorbent sucks the liquid refrigerant back into the collector. The movement happens through natural convection - without pumps, valves or any mechanical components. In the process, the liquid refrigerant evaporates and gets very cold. Any water touching the outside of the evaporator is frozen to ice, in an intermittent absorption refrigeration cycle. Basically, the two materials (absorbent and refrigerant) create a chemical reaction that becomes so cold that anything near the chemical reaction freezes - like water. To create ice continuously, the chemical reaction is produced over and over again by separating the two chemicals, using the heat of the sun, and then combining them again, at night. Once the icemaker is constructed, it has a zero carbon footprint. Greenhouse gases are not emitted during its operation nor are there any chemicals emitted that would deplete the ozone layer.
Three Types of Solar Ice Makers
Solar ice makers use one of 3 different methods: Zeolite/water - vacuum, CaCl /ammonia, or carbon/methanol. The zeolite/water under a vacuum is the easiest to implement since it doesn't include a hazardous chemical like methanol or ammonia. The carbon/methanol needs 1 square meter of collecting area to generate around 20 lbs of ice. While the ice is generated over night with these intermittent refrigeration cycles, you can cover the solar collector after a few hours to start the process.
How They Work
The plumbing of the ice maker can be divided into three parts: a generator for heating the salt-ammonia mixture, a condenser coil, and an evaporator, where the distilled ammonia collects during generation. Ammonia needs to flow back and forth between the generator and evaporator.These ice makers operate in a day/night cycle, generating distilled ammonia during the daytime and then re-absorbing it at night. The gas condenses in the condenser coil and drips down into the storage tank where, ideally, 3/4 of the absorbed ammonia collects by the end of the day. As the generator cools, the night cycle begins. The calcium chloride re-absorbs ammonia gas, pulling it back through the condenser coil as it evaporates out of the tank in the insulated box. The evaporation of the ammonia removes large quantities of heat from the collector tank and the water surrounding it. Water in bags around the tank turns to ice. In the morning the ice is removed and replaced with new water for the next cycle.
Self-Cooling Beer Kegs
An example of a Zeolite ice maker has been incorporated into the Self Cooling Beer Keg. The self-cooling keg contains three chambers. A reservoir of water in an evacuated chamber surrounds the inner chamber containing the beer. This water reservoir is connected by a tube to the outer chamber containing Zeolite. Since this tube is also evacuated it contains water vapor. By opening a valve the water vapor flows to the Zeolite where it will be absorbed. As this happens, the Zeolite warms up, absorbing heat from the water reservoir as it does so. The reaction is sufficiently intense to cool the water in the reservoir enough so that it freezes. After 30 minutes, a cold glass of beer can be tapped and the keg will keep a perfect drinking temperature for at least 12 hours. There aren't any commercially available models of these ice makers yet that aren't rather large and cost $1000 or more. The first viable product is the beer keg($35) but soon will we see other products. If you can chill 5 gallons for 8 hours with no power, they would be perfect for chilled drinks while camping or boondocking.
Source : http://www.solaripedia.com
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| Many off grid applications exist for solar ice makers using the zeolite/water-vacuum process diagrammed here. A reservoir of water in an evacuated chamber is used to make the ice. This water reservoir is connected by a tube to another chamber containing Zeolite. Since this tube is also evacuated it contains water vapor. The chilling process is started by opening a valve so the water vapor flows to the Zeolite where it will be absorbed. As this happens, the Zeolite warms up, absorbing heat from the water reservoir as it does so. The reaction is sufficiently intense to cool the water in the reservoir enough so that it freezes. For each square meter of solar collecting area, these ice makers can generate over 10 lbs of ice. ©2012 Squidoo |
Three Types of Solar Ice Makers
Solar ice makers use one of 3 different methods: Zeolite/water - vacuum, CaCl /ammonia, or carbon/methanol. The zeolite/water under a vacuum is the easiest to implement since it doesn't include a hazardous chemical like methanol or ammonia. The carbon/methanol needs 1 square meter of collecting area to generate around 20 lbs of ice. While the ice is generated over night with these intermittent refrigeration cycles, you can cover the solar collector after a few hours to start the process.
How They Work
The plumbing of the ice maker can be divided into three parts: a generator for heating the salt-ammonia mixture, a condenser coil, and an evaporator, where the distilled ammonia collects during generation. Ammonia needs to flow back and forth between the generator and evaporator.These ice makers operate in a day/night cycle, generating distilled ammonia during the daytime and then re-absorbing it at night. The gas condenses in the condenser coil and drips down into the storage tank where, ideally, 3/4 of the absorbed ammonia collects by the end of the day. As the generator cools, the night cycle begins. The calcium chloride re-absorbs ammonia gas, pulling it back through the condenser coil as it evaporates out of the tank in the insulated box. The evaporation of the ammonia removes large quantities of heat from the collector tank and the water surrounding it. Water in bags around the tank turns to ice. In the morning the ice is removed and replaced with new water for the next cycle.
Self-Cooling Beer Kegs
An example of a Zeolite ice maker has been incorporated into the Self Cooling Beer Keg. The self-cooling keg contains three chambers. A reservoir of water in an evacuated chamber surrounds the inner chamber containing the beer. This water reservoir is connected by a tube to the outer chamber containing Zeolite. Since this tube is also evacuated it contains water vapor. By opening a valve the water vapor flows to the Zeolite where it will be absorbed. As this happens, the Zeolite warms up, absorbing heat from the water reservoir as it does so. The reaction is sufficiently intense to cool the water in the reservoir enough so that it freezes. After 30 minutes, a cold glass of beer can be tapped and the keg will keep a perfect drinking temperature for at least 12 hours. There aren't any commercially available models of these ice makers yet that aren't rather large and cost $1000 or more. The first viable product is the beer keg($35) but soon will we see other products. If you can chill 5 gallons for 8 hours with no power, they would be perfect for chilled drinks while camping or boondocking.
Source : http://www.solaripedia.com
