Renewable Energy: Solar-Cooling Technologies
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What is the primary function of solar-cooling technologies?

Solar-cooling technologies are designed to produce 'cold' through the use of solar energy.

What are the two main types of solar-cooling systems based on their heat input and COP?

  • High-temperature and low-temperature
  • Single-effect and double-effect (correct)
  • Absorption and adsorption
  • Direct-fired and indirect-fired
  • Solar-electric cooling is often considered as part of the 'solar-cooling' category.

    False

    What are the main advantages of solar-cooling systems?

    <p>Solar-cooling systems offer significant reductions in electricity consumption, pollutant emissions, and greenhouse gas emissions. They also exhibit an overlap between solar radiation availability and cooling demand.</p> Signup and view all the answers

    What are the critical issues associated with solar-cooling systems?

    <p>High installation costs, heat rejection challenges, lack of technological understanding, and non-self-sufficiency.</p> Signup and view all the answers

    What is the difference between absorption and adsorption in terms of the process involved?

    <p>Absorption involves incorporating a substance from one phase into another substance of a different phase, whereas adsorption utilizes a solid to adhere or bond ions and molecules of another substance onto its surface.</p> Signup and view all the answers

    Desiccant cooling is considered a new type of thermally activated technology.

    <p>True</p> Signup and view all the answers

    What is the primary function of adsorption in thermal compression regarding refrigeration?

    <p>Adsorption offers a method for achieving thermal compression of the refrigerant, acting as an alternative to mechanical compression.</p> Signup and view all the answers

    Solar-cooling systems based on absorption chillers are typically categorized as open-circuit systems.

    <p>False</p> Signup and view all the answers

    Explain the difference between single-effect and double-effect absorption chillers.

    <p>Single-effect absorption chillers rely on a lower temperature heat input, achieving moderate COP values. Double-effect systems operate at higher temperatures, resulting in a higher COP but often necessitating more complex design and operation.</p> Signup and view all the answers

    Which of these pairs of substance combinations are commonly employed in absorption chillers?

    <p>Water/ammonia, LiBr/water, LiCl/water</p> Signup and view all the answers

    What is the primary purpose of the expansion valve in an absorption cycle?

    <p>The expansion valve plays a crucial role in reducing the pressure of the refrigerant as it transitions from the condenser to the evaporator, facilitating the evaporation process and achieving cooling.</p> Signup and view all the answers

    Which of the following is NOT a primary component of the absorption cycle?

    <p>Compressor</p> Signup and view all the answers

    What is the primary purpose of the absorber in an absorption cycle?

    <p>The absorber functions to absorb the refrigerant vapor into a solution, facilitated by the presence of an absorbent.</p> Signup and view all the answers

    What is the significance of the COP (Coefficient of Performance) in the context of an absorption cycle?

    <p>The COP of an absorption cycle represents the ratio of useful cooling output to the heat input required to drive the cycle, serving as a measure of the system's efficiency.</p> Signup and view all the answers

    The maximum ideal COP achievable in an absorption cycle is directly proportional to the heat input temperature.

    <p>False</p> Signup and view all the answers

    What are the primary advantages of using lithium bromide-water absorption systems?

    <p>Lithium bromide-water absorption systems are simple, widely used, and commercially proven, offering a relatively efficient and reliable method for cooling.</p> Signup and view all the answers

    What is the primary reason for using water as a refrigerant in lithium bromide-water absorption systems?

    <p>Water is readily available and environmentally friendly.</p> Signup and view all the answers

    Why is a water-cooled absorber important in lithium bromide-water absorption systems?

    <p>A water-cooled absorber is essential for preventing crystallization of the lithium bromide solution at high concentrations, ensuring the system's stability and performance.</p> Signup and view all the answers

    Triple-effect lithium bromide-water absorption systems are considered more complex than single-effect systems.

    <p>True</p> Signup and view all the answers

    Explain why double-effect lithium bromide-water absorption systems are generally regarded as having higher performance than single-effect systems.

    <p>Double-effect systems benefit from the ability to utilize the heat of condensation from the initial stage as input for the second stage, leading to a more efficient use of heat and ultimately a higher COP.</p> Signup and view all the answers

    What is the primary factor that influences the COP of absorption chillers?

    <p>Heat supply temperature</p> Signup and view all the answers

    What is the main advantage of adsorption chillers compared to absorption chillers, despite having a lower COP?

    <p>Adsorption chillers offer the advantage of operating at lower temperatures (55-65°C), making them suitable for applications where high-temperature heat sources are not readily available.</p> Signup and view all the answers

    What is the primary role of desiccant materials in adsorption chillers?

    <p>To absorb and release moisture from the air</p> Signup and view all the answers

    Explain the main difference between desiccant cooling systems (DEC) and adsorption chillers, despite their shared use of desiccant materials.

    <p>DEC systems operate on an open circuit, directly treating the air taken from the external environment, whereas adsorption chillers operate within a closed circuit, producing chilled water as the final product.</p> Signup and view all the answers

    DEC systems rely on the combined processes of dehumidification and evaporative cooling to achieve their cooling effect.

    <p>True</p> Signup and view all the answers

    What is the primary purpose of the silica gel matrix in an adsorption chiller?

    <p>The silica gel matrix serves as a high surface area material to adsorb moisture from the air stream, facilitating the dehumidification process.</p> Signup and view all the answers

    Which of the following statements accurately describes the functioning of desiccant cooling systems?

    <p>They utilize a desiccant to remove moisture from the air stream.</p> Signup and view all the answers

    The heating of the outgoing air stream in desiccant cooling systems is a necessary step to ensure efficient dehumidification of the incoming air.

    <p>True</p> Signup and view all the answers

    What is the primary function of the air heater in a desiccant cooling system?

    <p>The air heater is responsible for heating the outgoing air stream, reducing its relative humidity and increasing its capacity to absorb moisture from the incoming air.</p> Signup and view all the answers

    The operation of a solid desiccant dehumidifier is based on the process of adsorption, where moisture is removed from the air and adsorbed by the desiccant material.

    <p>True</p> Signup and view all the answers

    Explain the main function of the desiccant wheel in a solid desiccant system for air dehumidification.

    <p>The desiccant wheel acts as a rotating drum containing a desiccant material, facilitating the adsorption and regeneration of moisture from the air stream.</p> Signup and view all the answers

    What is the primary driving force for the moisture removal process in a solid desiccant dehumidifier?

    <p>Desiccant's affinity for moisture</p> Signup and view all the answers

    Study Notes

    Renewable Energy Technologies: Solar-Cooling

    • Solar-cooling technologies use solar energy for refrigeration, air conditioning, and food preservation.
    • A solar-cooling example is a refrigeration system with solar collectors providing heat input.

    Solar Cooling Systems

    • Absorption Cycle: A diagram shows the components: condenser, vaporizer, absorber, generator, solution throttle valve, restrictor valve. These components are part of a closed-circuit system. Relevant heat is labeled (Qcond, Qvap, Qabsorb).

    • Solar-Cooling Technologies: Use solar energy for cooling.

    • Example Systems:

      • Refrigeration systems combined with solar collectors provide heat input.
      • Diagrams illustrate the system, showing components like solar collectors, hot storage, cold storage, and a user area.

    Additional Solar-Cooling Systems

    • Electric Solar: Uses photovoltaic modules and inverters for power, and an electric refrigerator for cooling. This has a battery storage component.
    • Thermal Solar: Uses thermal collectors and a thermal storage component. The diagram shows components like solar collectors, storage, and a user zone. A thermal component is included.
    • Diagrams illustrate these types of systems, connecting the components in a circuit for cooling applications (cooling and dehumidification).

    Traditional Electric Chiller

    • A traditional electrically powered chiller with photovoltaic modules is depicted. This diagram details the photovoltaic module input and the conventional compressor, condenser, and evaporator components.

    Advantages of Solar Cooling

    • Reduces electricity consumption for air conditioning in buildings.
    • Reduces emissions of pollutants (NOx, SO2), and greenhouse gases (CO2).
    • Overlap between solar radiation availability and cooling demand.
    • Large solar collector surfaces enhance winter heating/DHW (Domestic Hot Water) contribution.

    Critical Issues of Solar Cooling

    • Installation costs are greater than traditional systems.
    • Heat rejection is a crucial aspect.
    • Limited knowledge base of the technology.
    • The solar-cooling system may not be self-sufficient.

    Absorption Cycle: Max Ideal COP

    • Mathematical formulas show the ideal Coefficient of Performance (COP) calculations for different parameters in an absorption cycle.
    • Equations demonstrate the relationship between heat transfer (q0, q8, qC,), temperatures (To, TAMB, TG), and COP.

    Absorption Systems and Subsystems

    • Refrigerating absorption systems are present. Desiccant evaporative cooling is a type of system.
    • DEC (Desiccant Evaporative Cooling) Systems: Open circuit systems use to condition air from external environments. Combining dehumidification and evaporative cooling in AHUs (air handling units.)

    Sorption Technologies

    • Absorption is the process of incorporating a substance into another phase (gases absorbed by a liquid).
    • Adsorption uses solids to adhere or bond other substances to their surfaces.
    • Desiccant cooling is a type of thermally activated technology, using the principles of absorption and adsorption.

    Solar-Cooling Systems, Based on Absorption Chillers

    • Closed-circuit systems are used to produce chilled water.
    • They combine with various distribution methods (air treatment units, etc.).
    • Absorption chillers are single or double effect, using lower or higher temperature inputs.

    Thermally Activated Cooling Technologies: Summary

    • Tables summarizing different sorption technologies, including types, heat sources, refrigeration capacity, cooling methods, and COP ranges.
    • Specific details about lithium bromide-water absorption systems, including cooling temperature, heat source temperature, cooling capacity, thermal COP, and other characteristics. The table distinguishes single, double, and triple-effect absorption chillers.

    Coefficient of Performance (COP) in Absorption Chillers

    • Diagrams show the COP variation with heat supply temperature for single effect, double effect, and triple effect absorption chillers. Diagrams display the relationship between the heat supply temperature and COP.

    Desiccant Cooling (DEC) Systems

    • The system uses desiccants for air conditioning.
    • It utilizes an open cycle, operating with humid air, and does not require refrigerants to cool.
    • The system uses external heat source and internally transfers heat to achieve cooling.
    • The system features a dehumidifier to reduce humidity.

    Materials for Adsorption Chillers

    • Lists different adsorbents (e.g., silica gel, zeolite) and refrigerants (e.g., water, methanol).
    • Different characteristics (heat of adsorption, toxicity, generation temperature) for these materials are presented in the context of applications.

    Diagrams and Schematics

    • Various diagrams illustrating the different types of solar cooling systems (absorption, adsorption). The diagrams typically show components involved in the systems, such as heat exchangers, condensers, evaporators, and regulators.

    Air Dehumidification with Solid Desiccants

    • Air dehumidification process using solid dessicant is shown in a diagram, with details of the regeneration cycle.

    DEC Systems (Desiccant Evaporative Cooling)

    • Open circuit systems for direct air treatment, combining dehumidification and evaporative cooling.
    • Applied to air handling units (AHUs) requiring adequate air distribution systems.

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    Solar-Cooling Technologies PDF

    Description

    This quiz explores solar-cooling technologies involving the use of solar energy for refrigeration, air conditioning, and food preservation. You'll learn about various systems, including absorption cycles and electric solar cooling, complete with diagrams and key components. Test your knowledge on how solar collectors integrate into these systems.

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