Nguyên tắc cơ bản của việc sử dụng năng lượng tái sinh là tách một phần năng lượng từ các quy trình diễn biến liên tục trong môi trường và đưa vào trong các sử dụng kỹ thuật. | 94 Desalination Trends and Technologies Fig. 1. Solar desalination systems Goosen et al. 2000 adapted from Fath 1998 . A. Singleeffect basin still. B. Single-sloped still with passive condenser. C. Cooling of glass cover by a feedback flow and b counter flow. D. Double-basin solar stills a schematic of single and double-basin stills and b stationary double-basin still with flowing water over upper basin. E. Directly heated still coupled with flat plate collector a forced circulation and b natural circulation. F. Typical multi-effect multi-wick solar still. Application of Renewable Energies for Water Desalination 95 Indicative temperature range 8C Concentrati on ratio Absorber type 30-80 1 Flat 50-200 1 Flat 60-240 1-5 Tubular 60-300 5-15 Tubular 60-250 10-40 Tubular 60-300 15-45 Tubular 60-300 10-50 Tubular 100-500 100-1000 Point 150-2000 100-1500 Point Collector type Motion Flat plate collector FPC Stationary Evacuated tube collector ETC Compound parabolic collector CPC Compound parabolic Single-axis collector CPC tracking Linear Fresnel reflector LFR Parabolic trough collector PTC Cylindrical trough collector CTC Parabolic dish reflector Two-axes PDR tracking Heliostat field collector HFC Table 1. Solar Energy Collectors Kalogirou 2005 Note Concentration ratio is defined as the aperture area divided by the receiver absorber area of the collector. Fig. 2a. Left Solar pond for heating purpose demonstration in Australia http library pubs bn sci . 2b. Right Solar Ponds Schematic The salt content of the pond increases from top to bottom. Water in the storage zone is extremely salty. As solar radiation is absorbed the water in the gradient zone cannot rise because the surface-zone water above it contains less salt and therefore is less dense. Similarly cooler water cannot sink because the water below it has a higher salt content and is denser. Hot water in the storage zone is piped to for example a boiler where it is heated further
