* Solar desalination technologies. * Multi-Effect Distillation with solar energy * Double Effect Absorption Heat Pump use in solar MED desalination * Hybrid solar-gas desalination systems * Thermal storage to 24 h operation

1. Dr. Julián Blanco Plataforma Solar de Almeria [email_address] SOLAR DESALINATION TECHNOLOGIES Solar Desalination Webinar #1 14 October 2010

3. DESALINATION PROCESSES Thermal energy Mechanic energy Evaporation Chemical energy Multi-Stage Flash Distillation (MSF) Thermal Vapor Compression (TVC) Solar Distillation Freezing Reverse Osmosis (RO) Mechanical Vapor Compression (MVC) Membrane distillation Multi-Effect Distillation (MED) Hydrate formation Electrodialysis (ED) Ionic exchange Crystallization Filtration and evaporation Evaporation Selective filtration Electric energy Filtration Exchange DESALINATION PROCESSES

4. THERMAL DISTILLATION Parameters to measure energy efficiency of thermal distillation processes: Gain Output Ratio (G.O.R.) : kg of distillate produced for every kg of steam supplied to the distillation unit Performance Ratio (PR) : kg of distillate produce for every 2326 kJ of thermal energy supplied to the distillation unit

5. THERMAL DISTILLATION

6. Source: GWI (2008) Five countries (Saudi Arabia, UAE, United States, Spain and Kuwait) have, today, 56% of the total share of world desalted water production. WORLDWIDE CAPACITY

7. DISTRIBUTION BY PROCESS Source: GWI (2006)

8. DISTRIBUTION BY PROCESS Source: GWI (2008)

10. The desalination mechanism of a solar still is similar to that of nature. A shallow pool of brackish or seawater absorbs solar energy and as a result vapor of fresh water is formed in the space above the water. Vapor condenses on the inside of the glass cover and is collected in a side trough. A conventional solar still has a simple geometry. The still is formed of a square or rectangular box , which is equipped with a sloped glass cover . The top cover is transparent to allow passage of solar energy (radiation). SOLAR STILLS The walls and base of the box must be made from materials that can withstand the environmental influences (wood, plastic, or tolerant metal).

12. In 1870 the first American patent on solar distillation by Wheeler and Evans, describing the basic operation of the solar stills. In 1872 Carl Wilson designed and built the first large solar still in Las Salinas, Chile. Effluents from a saltpeter (KNO 3 ) mine, (salinity 140g/kg). 64 bays, 4450 m 2 surface, 7896 m 2 of land 22.7 m 3 /day. Operated for 40 years. Wood and timber frameworks. from: Delyannis, Solar Energy 75, 357-366, 2003 SOLAR STILLS

14. The H-DH (Humidification-Dehumidification) processes are based on the fact that air can be mixed with important quantities of vapor. The vapor carrying capability of air increases with temperature, i.e., 1 kg of dry air saturated with vapor can carry additional 0.26 kg of water vapor (about 208 kJ/kg) when its temperature increases from 30°C to 80°C. H-DH DESALINATION PROCESS

15. Air heated HDH system Water heated HDH system Air-heated systems have higher energy consumption than water-heated systems, because energy can be recovered from water in the humidifier but not from the air H-DH DESALINATION PROCESS

18. Membrane Distillation is an evaporative process in which water vapour, driven by a difference in vapour pressure, permeates through a hydrophobic membrane, thus separating from the salt water phase. The separation effect of these membranes is based on the hydrophobicity of the polymer material constituting the membrane. Molecular water in the form of steam can pass through the membrane. Once the vapour has passed through the membrane, it can be extracted or directly condensed in the channel on the other side of the membrane. MEMBRANE DISTILLATION

19. Membrane distillation system with internal heat recovery MEMBRANE DISTILLATION

24. WORLDWIDE EXPERIENCES Source: García-Rodríguez, Desalination 143 (2002), pp. 103-113

28. PLATAFORMA SOLAR STD PROJECT The solar collector field consists of one-axis tracking parabolic trough collectors with a total aperture area of 2672 m², model Acurex-3001. The daily thermal energy delivered by the collector field is about 6.5 MW th ·h, but the daily thermal energy requirement of the desalination plant is less than 5 MW th ·h for 24-hour daily operation.

29. The distillation plant installed at the PSA is a forward-feed, vertically-stacked, multi-effect distillation unit with 14 effects. PLATAFORMA SOLAR STD PROJECT

30. PLATAFORMA SOLAR STD PROJECT

31. Performance Ratio: 9.4 – 10.4 PLATAFORMA SOLAR STD PROJECT

32. Performance Ratio: 12 - 14 PLATAFORMA SOLAR STD PROJECT

36. MED OPERATION: SOLAR MODE

37. MED OPERATION: FOSSIL MODE

38. MED OPERATION: HYBRID MODE

39. The solar field is made up of 252 stationary solar collectors (CPC Ao Sol 1.12x) with a total surface area of 500 m 2 arranged in four rows of 63 collectors. CPC SOLAR COLLECTOR FIELD

40. The thermal storage system is made up of two interconnected 12-m 3 -capacity water tanks. This storage volume is based on the response time required by the gas boiler and the DEAHP to reach nominal operating conditions THERMAL STORAGE TANKS

41. 150 kW 78 kW 2 kW 70 kW ABSORPTION HEAT PUMPS

42. ABSORPTION HEAT PUMPS The inclusion of a Double Effect Absorption Heat Pump make possible a reduction up to 50 percent of the overall energy consume with respect to conventional MED plants. However, it requires higher steam temperature (180ºC)

43. ABSORPTION HEAT PUMPS The double effect absorption heat pump increases the energy efficiency of the distillation process by making use of the 35ºC saturated steam produced in the last MED plant effect, which otherwise involve the loss of the energy in the evacuation of the cooling fluid used for its condensation.

44. LiBr-H 2 O THERMODYNAMIC CYCLE Qg = 72 kW (gas) Qe = 78 kW (LP steam) Qa + Qc = 150 kW (MED)

45. EXPERIMENTAL RESULTS Day 1 Day 2

46. Distillate production and global thermal energy consumed by AQUASOL plant in SOLAR-ONLY MODE Average PR = 10.07 SOLAR-ONLY MODE

47. EXPERIMENTAL RESULTS Day 1 Day 2

48. Distillate production and global thermal energy consumed by AQUASOL plant in FOSSIL-ONLY MODE FOSSIL-ONLY MODE

49. Performance ratio of the AQUASOL plant in Fossil-only mode PERFORMANCE RATIO

52. LOCATION AND PARAMETERS Annual direct normal irradiation = 1990 kWh/m² year

55. SOLAR THERMAL MED PLANT

56. SOLAR THERMAL DUAL PLANT Thermal oil/water heat exchanger Generator Degasifier Steam Turbine Vapor at 97 bar/395 ºC Vapor at 17 bar/225 ºC G Water at 70ºC Vapor at 70ºC Oil at 295 ºC Oil at 400 ºC Oil expansion deposit 50 mbar 35ºC 0,3 bar 70ºC Distilled Seawater Brine Thermal Storage Solar Collector Field Auxiliary boiler

57. Thank you very much for your attention