Optical Performance Analysis of Single Flow Through and Concentric Tube Receiver Coupled with a Modified CPC Collector Under Different Configurations

Javed Akhter,Hussain H Al-Kayiem,Muzaffar Ali,Syed I Gilani

doi:10.3390/en12214147

Javed Akhter, Hussain H Al-Kayiem + Show 2 more

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Compound parabolic concentrating (CPC) collectors have great potential to provide sustainable solar thermal energy for many applications operating in the medium temperature range. This paper presents the design, development and performance evaluation of a modified CPC collector integrated with an evacuated tube receiver. The optical performance of the designed CPC paired with concentric tube receiver is compared with that of a CPC coupled with single flow through evacuated tube receiver for stationary installation in the East-West and North-South directions. Ray tracing simulations of different configurations demonstrate that CPC coupled with single flow through receivers suffer high gap losses, especially at smaller incidence angles which are considerably alleviated by a concentric tube receiver arrangement. East-West installation of CPC paired with concentric tube receiver exhibited superior optical performance than all other configurations. The yearly average optical efficiency of CPC with concentric tube receiver was 5% higher than that of a single flow through receiver within the acceptance angle. A 60% truncated CPC coupled with concentric tube receiver emerged as the most effective design, which was fabricated for experimental testing. The tests conducted under actual outdoor tropical environmental conditions demonstrated that the experimental optical efficiency reached to about 69% in the case of N-S installation and 66.5% in an E-W arrangement. The experimental results closely match the simulation outcomes, which indicate the proposed performance prediction technique as instrumental for selecting the most effective configuration of CPC collectors for medium temperature heat supply.

Highlights

Compound parabolic concentrating collectors are non-imaging devices which have great potential to supply sustainable solar thermal energy in the medium (90–300 ◦ C) temperature range [1,2].CPC collectors, generally, don’t need continuous tracking mechanisms for lower concentration range and only seasonal or intermittent adjustments are required for medium concentration range (3–10×) [3,4]
Trajectories of the incident and reflected radiations for different configurations were obtained using Monte Carlo ray tracing technique which works on the principle of geometric optics as well as statistical methods to simulate the behavior of optical systems to trace the transmission path of all individual rays originating from the source to the receiver
60% truncated CPC coupled with single flow through tube (SFT) receiver suffered high gap losses, especially at smaller incidence angles which were significantly alleviated by the concentric tubeFigure (CT) receiver due to the reduced gap between the absorber and the reflector cusp by extended flat fins

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Compound parabolic concentrating collectors are non-imaging devices which have great potential to supply sustainable solar thermal energy in the medium (90–300 ◦ C) temperature range [1,2].CPC collectors, generally, don’t need continuous tracking mechanisms for lower concentration range (below 3×) and only seasonal or intermittent adjustments are required for medium concentration range (3–10×) [3,4]. Compound parabolic concentrating collectors are non-imaging devices which have great potential to supply sustainable solar thermal energy in the medium (90–300 ◦ C) temperature range [1,2]. CPC collectors for various low-to-medium temperature applications, including industrial process heat [7], solar heating and cooling [8], water treatment and purification [9], methanol reforming and hydrogen production [10], building-integrated water heating systems [11] and photovoltaic/thermal (PV/T) hybrid systems [12]. After the introduction of CPC as a potential candidate for solar energy collection [13], many research studies have been conducted in this field [3,14,15]. Derrick et al [17] analyzed different concentrators with non-evacuated tubular absorbers and compared annual energy collection for East-West (E-W) and North-South (N-S)

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