Solar cooling consists in the combination of solar panels and a refrigerating machine. In other words, solar cooling technology allows the production of cold, in the form of chilled water or air conditioning, starting from a renewable heat source such as solar thermal collectors. The combination between the solar production and the cooling request has its best application with thermal solar solution, because periods of increased production and higher energy savings coincide.
Why solar cooling?
Solar cooling exploits the fact that the hours of the day (in summer) when there is a greater request of cold for cooling of buildings, coincide with the maximum availability of solar radiation. It is known that the electricity demand peaks occur in the summer season due to the simultaneous operation of millions of small air conditioners.
Solar cooling is beneficial on two fronts. From the point of view of the national electricity system, the large-scale deployment of this technology can help to ease the pressure on the power grid, avoiding the dangerous summer peaks. From the point of view of those who choose to install a solar cooling system, there are substantial benefits in terms of energy and cost savings. Without considering the reduction of polluting emissions and CO2 into the atmosphere.
Some technical details...
The proposed technological solution provides high-quality and proven reliability components. Solar energy is collected through the vacuum tube collectors produced by Pleion, a leading company in Italy, and is transferred through a plate heat exchanger to storage tanks in order to ensure the availability of thermal energy to be exploited even during the hours when the solar radiation is reduced, or completely absent.
The heat thus conveyed is exploited to feed an absorption chiller, working with a mixture of water and lithium bromide, which provides for the conversion of heat into cooling energy through the following phases:
- the supply water heats, bringing it to the boil, the dilute solution of water and lithium bromide contained in the generator;
- the boiling generate water vapor (refrigerant) and concentrate the lithium bromide solution;
- the concentrated solution is collected and pre-cooled, passing through the heat exchanger, before being supplied into the absorber;
- the refrigerant vapor reaches the condenser where it condenses on the surface of the coils of the cooling circuit;
- the condensation heat is removed by cooling water and expelled through the cooling tower;
- the liquid refrigerant, collected in the condenser, reaches the evaporator through a specific opening. The pressure existing in the evaporator is much lower than that of the generator and the condenser due to the influence exerted by the absorber. For this reason, the liquid refrigerant, once entered in the evaporator, boils and absorbs heat evaporating on the surface of the coil of the circuit of the water to be cooled;
- the refrigerant vapor obtained then flows into the absorber; the low pressure in the absorber is due to the chemical affinity between the concentrated solution of lithium bromide from generator and the water vapor which forms in the evaporator. The refrigerant vapor is absorbed by the concentrated solution of lithium bromide, while it lapping the surface of the absorber coil.
- The heat of condensation and dilution is removed by cooling water;
- the diluted solution of lithium bromide is then pre-heated in the heat exchanger before returning into the generator;
- the cycle re-starts from point 1.
The cooling water, in turn, is sent to a cooling tower for dissipating the heat removed from the absorption machine.
You can download from the link below a detailed technical report of an example study-case.