Solid absorption solar refrigeration uses solar energy or waste heat to power refrigeration through an absorption process rather than vapor compression. It has advantages of being ecologically friendly without CFCs or HCFCs, requiring low energy input, and being well suited for remote off-grid locations. While it has lower efficiency than vapor compression, it has applications for preserving vaccines and cooling boats using waste heat. The absorption process involves dissolving a refrigerant into an absorbent, then heating to evaporate the refrigerant which cools an evaporator space before returning to the absorbent. Common working pairs include activated carbon/methanol or ammonia/water. Commercial models include an ice maker using activated carbon/methanol with no pumps or valves

1. Solid Absorption Solar Refrigeration Presented by: Conor Kennedy

2. Introduction Advantages Ecologically-friendly refrigerants No CFCs or HCFCs involved which contribute to ozone depletion. Powered by solar energy or waste heat Energy input requirements are significantly lower than the common vapor-compression cycle. Well suited for operation in remote locations Low maintenance It is possible to construct a system with no moving components.

3. Introduction Disadvantages Low Efficiency compared to vapor-compression refrigerators High initial cost of production Applications Off-grid or remote locations where electricity is either unreliable or unavailable. 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.

4. Refrigeration Fundamentals Objective is to remove heat from a controlled space First Law of Thermodynamics Energy can be transformed but never destroyed (Conservation of Energy) Second Law of Thermodynamics “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) Differences in heat will always reach an equilibrium Example: If you place a hot pan in a cool room, the pan and its surroundings will eventually become the same temperature. COP (Coefficient of Performance) Expresses the efficiency of a refrigerator 𝐶𝑂𝑃=𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑜𝑢𝑡𝑝𝑢𝑡𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑖𝑛𝑝𝑢𝑡=𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑝𝑜𝑤𝑒𝑟𝑃𝑜𝑤𝑒𝑟 𝑟𝑒𝑐𝑖𝑣𝑒𝑑 𝑏𝑦 𝑠𝑜𝑙𝑎𝑟 𝑐𝑜𝑙𝑙𝑒𝑐𝑡𝑜𝑟

5. Absorption Refrigerators Overview Three Phases Absorption Refrigerant as a low-pressure vapor dissolves into the liquid absorbent. Regeneration The liquid mixture of refrigerant and absorbent is heated and the refrigerant evaporates out. The pure refrigerant then condenses back into a liquid through a heat exchanger and flows into the evaporator Evaporation The attraction between the refrigerant and absorbent causes the refrigerant to evaporate as at low pressures which removes heat from the refrigeration space This lo pressure vapor then returns to the absorption phase

6. Absorption Refrigeration This Schematic shows the process or heat transfer for a absorption refrigerator.

7. Absorption Refrigeration Common Working Pairs (Refrigerant/Absorbent) Activated Carbon and Methanol Ammonia and Water Silica Gel and Water Zeolite and Water

8. Refrigerator Models (commercial) Simple solar powered ice maker using Activated-carbon and Methanol

9. Refrigerator Models (commercial) Photo of Model shown on previous slide This model has been designed with no valves or pumps Comparable COP to other absorption refrigerators (COP is 0.09 to 0.13)

10. Conclusions Methods for Improvement Heat and Mass Transfer in the Absorber This may be done with a parabolic solar collector as opposed to a flat plate collector Absorption Properties of Working Pairs Silica-gel and water have produced the highest recorded COPs for solar driven ice generation. Air conditioning applications show zeolite and water to be most favorable. Heat Management During Absorption Heat loss due to poor insulation will lower efficiency of the system.