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Air conditioning by solar absorption
Introduction
The terms Solar cooling and solar cooling refer to systems that use solar energy to cool environments. The most frequent application is air conditioning, both in buildings and mobile environments (especially vehicles). There are systems based on photovoltaics and others on solar thermal energy.
Solar cold technology is based on an apparently contradictory idea: taking advantage of heat to generate cold. Taking into account that electricity consumption rises considerably during the summer months due to the use of air conditioning units, the generalization of this technology can represent a very positive development in the implementation of new applications of renewable energy and in the reduction of said peaks in electricity consumption.
Operation
Photovoltaic-based systems
Any electric air conditioning device could work from the energy generated by photovoltaic solar modules. There are several manufacturers that sell combinations between the two technologies. The advantage is that no special devices are needed and both elements are available on the market. The disadvantage is the low performance, compared to solar thermal energy systems.
Systems based on solar thermal energy
Systems based on solar thermal energy extract greater performance from facilities - often under-utilized or at risk of overheating during the summer. It is one of the applications with solar energy in which supply best adapts to demand.
The technology used in these systems, absorption refrigeration, is based on the ability to absorb heat from certain pairs of substances, such as water and lithium bromide or water and ammonia. Its operation is based on physical-chemical reactions between a refrigerant and an absorbent, powered by thermal energy - which in the case of solar energy is hot water. Solar installations of this type require special equipment and installations in which there is increasing experience but it is advisable to have important support both in the design and in the execution, start-up and operation of the installation.
Air conditioning by solar absorption
Introduction
The terms Solar cooling and solar cooling refer to systems that use solar energy to cool environments. The most frequent application is air conditioning, both in buildings and mobile environments (especially vehicles). There are systems based on photovoltaics and others on solar thermal energy.
Solar cold technology is based on an apparently contradictory idea: taking advantage of heat to generate cold. Taking into account that electricity consumption rises considerably during the summer months due to the use of air conditioning units, the generalization of this technology can represent a very positive development in the implementation of new applications of renewable energy and in the reduction of said peaks in electricity consumption.
Operation
Photovoltaic-based systems
Any electric air conditioning device could work from the energy generated by photovoltaic solar modules. There are several manufacturers that sell combinations between the two technologies. The advantage is that no special devices are needed and both elements are available on the market. The disadvantage is the low performance, compared to solar thermal energy systems.
Systems based on solar thermal energy
Systems based on solar thermal energy extract greater performance from facilities - often under-utilized or at risk of overheating during the summer. It is one of the applications with solar energy in which supply best adapts to demand.
The technology used in these systems, absorption refrigeration, is based on the ability to absorb heat from certain pairs of substances, such as water and lithium bromide or water and ammonia. Its operation is based on physical-chemical reactions between a refrigerant and an absorbent, powered by thermal energy - which in the case of solar energy is hot water. Solar installations of this type require special equipment and installations in which there is increasing experience but it is advisable to have important support both in the design and in the execution, start-up and operation of the installation.
The operation of any absorption refrigeration machine is based on three elementary physical phenomena:
In a conventional refrigeration cycle with a mechanical compressor, the refrigerant fluid in liquid state flows through the evaporator, the medium to be cooled gives off heat, lowering its temperature, while the refrigerant evaporates. The low-pressure vapor passes to the compressor, increasing its pressure and temperature to a point at which the vapor liquefies, giving up heat to the medium to be heated used in the condenser. The refrigerant liquid goes from the condenser to an expansion element in which its pressure and temperature are reduced to those of the evaporator, completing the cycle.
If we replace the mechanical compressor of the previous refrigeration cycle with a thermal compressor composed of an absorber and a generator, also called a concentrator, we obtain an absorption refrigeration cycle.
In the cycle with water and lithium bromide as refrigerant and absorber respectively, the refrigerant vapor released in the evaporator is absorbed into the absorbent solution and this is diluted. To recover the refrigerant and reconcentrate the solution, it is pumped to the generator (concentrator) where, by adding heat (for example solar energy), the refrigerant is released by distillation. The concentrated solution is sent to the absorber to re-absorb refrigerant.
The refrigerant vapor released in the generator at higher pressure and temperature passes to the condenser.
In some industrial processes, work is done to increase heat conduction, either by using high-conductivity materials or configurations with a high contact area. In others, the desired effect is just the opposite, and it is desired to minimize the effect of conduction, for which materials with low thermal conductivity, intermediate voids (see thermos), and are arranged in configurations with a small contact area are used.
The operation of any absorption refrigeration machine is based on three elementary physical phenomena:
In a conventional refrigeration cycle with a mechanical compressor, the refrigerant fluid in liquid state flows through the evaporator, the medium to be cooled gives off heat, lowering its temperature, while the refrigerant evaporates. The low-pressure vapor passes to the compressor, increasing its pressure and temperature to a point at which the vapor liquefies, giving up heat to the medium to be heated used in the condenser. The refrigerant liquid goes from the condenser to an expansion element in which its pressure and temperature are reduced to those of the evaporator, completing the cycle.
If we replace the mechanical compressor of the previous refrigeration cycle with a thermal compressor composed of an absorber and a generator, also called a concentrator, we obtain an absorption refrigeration cycle.
In the cycle with water and lithium bromide as refrigerant and absorber respectively, the refrigerant vapor released in the evaporator is absorbed into the absorbent solution and this is diluted. To recover the refrigerant and reconcentrate the solution, it is pumped to the generator (concentrator) where, by adding heat (for example solar energy), the refrigerant is released by distillation. The concentrated solution is sent to the absorber to re-absorb refrigerant.
The refrigerant vapor released in the generator at higher pressure and temperature passes to the condenser.
In some industrial processes, work is done to increase heat conduction, either by using high-conductivity materials or configurations with a high contact area. In others, the desired effect is just the opposite, and it is desired to minimize the effect of conduction, for which materials with low thermal conductivity, intermediate voids (see thermos), and are arranged in configurations with a small contact area are used.