Solid absorption solar refrigeration

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Solar refrigeration overview

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Solid absorption solar refrigeration

  1. 1. Solid Absorption Solar Refrigeration<br />Presented by: Conor Kennedy<br />
  2. 2. Introduction<br />Advantages<br />Ecologically-friendly refrigerants <br />No CFCs or HCFCs involved which contribute to ozone depletion.<br />Powered by solar energy or waste heat<br />Energy input requirements are significantly lower than the common vapor-compression cycle.<br />Well suited for operation in remote locations<br />Low maintenance<br />It is possible to construct a system with no moving components.<br />
  3. 3. Introduction<br />Disadvantages<br />Low Efficiency compared to vapor-compression refrigerators<br />High initial cost of production<br />Applications<br />Off-grid or remote locations where electricity is either unreliable or unavailable.<br />Absorption refrigerators have been used to preserve vaccines in rural underdeveloped locations as well as serve as cooling systems on boats using the waste heat of the motor.<br />
  4. 4. Refrigeration Fundamentals<br />Objective is to remove heat from a controlled space<br />First Law of Thermodynamics<br />Energy can be transformed but never destroyed (Conservation of Energy)<br />Second Law of Thermodynamics<br />“No Process is possible whose sole result is the transfer of heat from a body of lower temperature to a body of higher temperature.” (Clausius statement)<br />Differences in heat will always reach an equilibrium <br />Example: If you place a hot pan in a cool room, the pan and its surroundings will eventually become the same temperature.<br />COP (Coefficient of Performance)<br /> Expresses the efficiency of a refrigerator<br />𝐶𝑂𝑃=𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑜𝑢𝑡𝑝𝑢𝑡𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑖𝑛𝑝𝑢𝑡=𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑝𝑜𝑤𝑒𝑟𝑃𝑜𝑤𝑒𝑟 𝑟𝑒𝑐𝑖𝑣𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑎𝑟 𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟<br /> <br />
  5. 5. Absorption Refrigerators<br />Overview<br />Three Phases<br />Absorption<br />Refrigerant as a low-pressure vapor dissolves into the liquid absorbent.<br />Regeneration<br />The liquid mixture of refrigerant and absorbent is heated and the refrigerant evaporates out. <br />The pure refrigerant then condenses back into a liquid through a heat exchanger and flows into the evaporator<br />Evaporation <br />The attraction between the refrigerant and absorbent causes the refrigerant to evaporate as at low pressures which removes heat from the refrigeration space<br />This lo pressure vapor then returns to the absorption phase<br />
  6. 6. Absorption Refrigeration<br />This Schematic shows the process or heat transfer for a absorption refrigerator. <br />
  7. 7. Absorption Refrigeration<br />Common Working Pairs (Refrigerant/Absorbent)<br />Activated Carbon and Methanol<br />Ammonia and Water<br />Silica Gel and Water<br />Zeolite and Water<br />
  8. 8. Refrigerator Models (commercial)<br />Simple solar powered ice maker using Activated-carbon and Methanol<br />
  9. 9. Refrigerator Models (commercial)<br />Photo of Model shown <br />on previous slide<br />This model has been designed with no valves or pumps<br />Comparable COP to other absorption refrigerators (COP is 0.09 to 0.13)<br />
  10. 10. Conclusions<br />Methods for Improvement<br />Heat and Mass Transfer in the Absorber<br />This may be done with a parabolic solar collector as opposed to a flat plate collector<br />Absorption Properties of Working Pairs<br />Silica-gel and water have produced the highest recorded COPs for solar driven ice generation.<br />Air conditioning applications show zeolite and water to be most favorable.<br />Heat Management During Absorption<br />Heat loss due to poor insulation will lower efficiency of the system.<br />

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