A PROTOTYPE PARABOLIC TROUGH SOLAR CONCENTRATORS FOR STEAM PRODUCTION

Abstract

In this work, the potential for a solar-thermal concentrator to produce steam has been studied. Three parabolic trough solar concentrators (PTSCs) of dimensions:  -aperture width of 1.2 m, Collector length of 5.8 m and aperture area of  6.95 m2 were  investigated.  The  absorber  pipe  was  a  copper  tube  which  carried  water  as the  heat  transfer  fluid,  were  designed,  fabricated,  characterized  and  their efficiencies  compared  when  closed  and  when  open.  The  PTSCs´  were  made  of appropriate  materials  and  were  manually  tracked.  They  were  designed  with principal focus at 0.4 m so that the receiver heat loss is minimized by covering the collectors with glass which was 0.0025 m in thickness. The concentration ratio of the solar concentrators was 128. The concentrator testing was carried out for each of the concentrators. The maximum temperature of steam obtained was 248.3oC while average temperature of steam was produced was 150oC. When closed their efficiencies  were:  Aluminium  sheet  reflector  PTSC;  55.52  %,  Car  solar  reflector PTSC;  54.65  %  and  Aluminium  foil  reflector  PTSC;  51.29  %.  The  open  solar concentrator  efficiencies  were  32.38  %,  34.45  %  and  27.74  %  respectively.  The efficiency  of  car  solar  reflector  when  open  was  higher  than  for  aluminium  sheet since  it  was  less  prone  to  thermal  degradation  when  exposed  to  weather elements. The results obtained show that production of power using the sun flux is a viable undertaking. The concentrators can be used to provide power to remote areas  which  are  far  away  from  the  power  transmission  gridlines.  This  will  make power  readily  available  to  the  marginalized  rural  people.  Improvement  of  the tracking  system  and  optical  efficiency  can  improve  the  efficiencies  of  the fabricated concentrator systems.