1. Solar cooling systems

2. INTRODUCTION
In solar cooling systems, solar heat is used to drive the cooling process.
Thermally driven cooling machines, such as absorption- or ad-sorption chillers have been used for decades, but have been powered mainly by industrial waste heat or by district heat.

3. In recent years, demonstration projects have shown the potential to use solar thermal energy to drive those chillers. Because most of the available thermal chillers have large cooling capacities (often several hundred kW), the focus of R&D was largely on developing smaller cooling units as well as to improve the system design.
About 100 systems have been installed in Europe and several companies are offering solar cooling solutions as part of their product and service portfolio.

4. Why solar cooling?
Dramatic increase of air conditioning since the early 80’s
Cost of energy
Issues related to environmental pollution
Due to energy production
Due to the use of CFC’s and HCFC’s
Matches demand with source availability
Crucial for improving life standards in developing countries

5. Solar cooling systems
In solar cooling systems, solar heat is used to drive the cooling process. Thermally driven cooling machines, such as absorption- or ad-sorption chillers have been used for decades, but have been powered mainly by industrial waste heat or by district heat.

6. Components of a solar cooling systems
A solar cooling installation consists of a typical solar thermal system made up of
Solar collectors
Storage tank
Control unit
Pipes and pumps
Thermally driven cooling machine-chillers

8. Solar Collectors
Solar collectors are the key component of active solar- heating and cooling systems. They gather the sun's energy, transform its radiation into heat, then transfer that heat to a fluid (usually water or air). The solar thermal energy can be used in solar water-heating systems, solar cooling systems,solar pool heaters, and solar space-heating systems .

9. classification
Flat-plate collectors – the absorbing surface is approximately as large as the overall collector area that intercepts the sun's rays.
Concentrating collectors – large areas of mirrors or lenses focus the sunlight onto a smaller absorber.

11. Chillers Chillers are the core of solar cooling plants.
If solar panels provide necessary energy input to the plant, chillers are those machines that are able to produce cooling by utilizing the hot water coming from solar panels.

12. chiller
A chiller is a machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. Most often water is chilled, but this water may also contain ~20% glycol and corrosion inhibitors. Other fluids such as thin oils can be chilled as well.

13. Types of chillers There are different types of chillers:
absorption type
adsorption type
They been used for decades but have been
powered mainly by electric motors, steam or gas turbines.

14. Adsorption chillers

15. How does the absorption chiller works?
Absorption chillers use solar heat energy instead of mechanical energy to provide cooling. A thermal compressor consists of an absorber, a generator, a pump, and a throttling device, and replaces the mechanical vapor compressor.

16. Continue….
refrigerant vapor from the evaporator is absorbed by a solution mixture in the absorber. This solution is then pumped to the generator. There the refrigerant re-vaporizes using a waste steam heat source. The refrigerant-depleted solution then returns to the absorber via a throttling device.

17. Absorbents commonly used
The two most common refrigerant/ absorbent mixtures used in absorption chillers are
water/lithium bromide.
ammonia/water.

18. Schematic diagram of single effect solar absorption chiller- air conditioning system

19. Remarks
absorption chillers have a low coefficient of performance (COP = chiller load/heat input).
Cop is around only
absorption chillers can substantially reduce operating costs because they are powered by low-grade waste heat.

20. Adsorption chillers

21. What is adsorption chillers?
Adsorption chillers apply solid sorption materials instead of a liquid solution.
Market available systems use water as a refrigerant and silica gel as a sorption material.

22. Components of adsorption refrigerator
Solar collector,
adsorber/generator module/s,
condenser and evaporator

23. Working procedure Step 1: Desorption – Drying of the adsorbent
Step 2: Adsorption – water vapour is adsorbed at the surface of the adsorbent
Step 3: Return of condensate

24. Working process of the adsorption chiller

25. Remarks
Under typical operation conditions, with a driving heat temperature of about 80°C,adsorption chillers can achieve a COP of about 0.6, but operation is possible even at heat source temperatures of approx. 60°C.
The capacity of these chillers ranges
from 50 kW to 500 kW chilling power.

26. Other solar cooling applications
SOLID DESICCANT COOLING WITH ROTATING WHEELS

27. What is desiccant cooling systems?
Desiccant cooling systems combine sorptive dehumidification, heat recovery, evaporation and heating to create a cooling process which can offer energy savings compared to conventional air conditioning systems.
Waste heat or solar energy can be used for the required regeneration of the sorbens in the dehumidifier, leading to further energy savings.

28. Continue….
Desiccant cooling systems (DEC) are basically open cycle systems, using water as a refrigerant in direct contact with air.
The thermally driven cooling cycle is a combination of evaporative cooling with air dehumidification by a desiccant.

30. Adavantages of desiccant cooling systems
Cost effective systems
Low energy consumption
Continuosly repeating cycle
Commonly used dessiccants are
Silica gel
zeolite

31. Comparison of the main sorption and desiccant technologies

33. solar cooling applications

34. Wine store cooling Use: cooling of a wine store
Site: Banyuls (south France)
Solar thermal collector field: 130 m² evacuated tube collectors
Chiller: absorption chiller with 52 kW cooling capacity

35. Air-conditioning of a factory
Use: air conditioning of the production facilities in a cosmetics factory
Site: Inofita Viotias (appr. 50 km north-east of Athens)
Solar thermal collector field: 2700 m² flat plate collectors
Chillers:
2 adsorptions chillers with 350 kW each
3 compression chillers with 350 kW each

39. Hotel air-conditioning
Use: air-conditioning of a hotel and steam supply for the hotel laundry
Site: Dalaman (Mediterranean coast Turkey)
Solar thermal collector field: 180 m² parabolic through collectors (aperture area)
Chiller: double effect absorption chiller (cooling capacity 116 kW, 4 bar)

41. THANKS