Conventional Compound Parabolic Concentrator Research Articles

Design and development of a novel and cost effective modified Compound parabolic trough collector

In the context of achieving Net Zero targets, the adoption of compound parabolic concentrator (CPC) technology can play a vital role. The purpose of this work is to modify the design of a conventional CPC in such a way that for the same concentration ratio, and for same aperture area, the modified CPC (MCPC) will require significantly less material for its support structure, receiver and reflector: and hence will have reduced cost. The MCPC, we designed, has a concentration ratio of 4 and an acceptance angle 10° and requires position modification only once a month when oriented with its long axis along the East-West direction. We report experiments on an experimental prototype: the solar-to-thermal efficiency of which was 35.7% and cost of which was below $60/m2. This MCPC enables inexpensive and convenient generation of heat applications including driving low temperature industrial process heating, generation of hot water, hot air for drying, space-heating and even cooking. This can directly contribute to meeting Net Zero goals and furthermore address the problem of deforestation due to use of wood for domestic cooking. Also, since the MCPC can be manufactured using technologies available even in semi-urban regions of the Sun-belt, use of the MCPC can also boost local manufacturing economies providing dignified employment opportunities in currently underserved parts of the world.

Design and Optical Performance Evaluation of the Three-Dimensional Solar Concentrators with Multiple Compound Parabolic Profiles and Elliptical and Rectangular Receiver Shapes

The compound parabolic concentrator (CPC) is a core technology in the field of solar concentration. Nevertheless, it only has one degree of freedom in the choice of its half-acceptance angle. In this study, extending the idea of the three-dimensional CPC, a design method for new kinds of concentrators having a CPC shape at each profile with various acceptance angles in all directions is proposed. The feature of this method is that the receiver can take any shape. Here, elliptical and rectangular receivers are assumed, and the shape and concentration performance of the concentrators with multiple CPC profiles and an elliptical receiver (MultiPro-ECPCs) and the concentrators with multiple CPC profiles and a rectangular receiver (MultiPro-RCPCs) are derived. The new designs are compared to the conventional CPC and a mirrorless flat receiver through ray-tracing simulations in terms of energy distribution on the receiver, optical efficiency, and optical concentration ratio based on axial and solar angles. The results show that in terms of optical efficiency, the MultiPro-RCPCs cover a wider range of incident angles after the 3DCPC. In terms of the optical concentration ratio, the MultiPro-ECPC with a longitudinal half-acceptance angle of 15° has the highest peak value of 19.5, followed by the MultiPro-RCPC. This study enlightens that with the concentration system settings adapted to the acceptance range of the proposed concentrators, a higher concentration can be achieved with the MultiPro-ECPC and MultiPro-RCPC compared to the conventional CPC.

Construction and concentrating performance of a critically truncated compound parabolic concentrator without light escape

Conventional solar CPC (Compound Parabolic Concentrator, CPC) has a limited collection of solar radiation at the end of the concentrating surface, which is not conducive to its wide application. In the present research, a solar CT-CPC (Critically Truncated CPC, CT-CPC) without light escape is proposed and constructed for the vacuum tube absorber, and discusses its optical properties, which provides a choice for improving or reforming the existing CPC system. Based on the edge ray principle, the geometric model of the CT-CPC is designed by the dichotomy method, and the concentrating performance of the CT-CPC is verified by the adjustable laser experiment. The study found that the average optical efficiency of CT-CPC reaches 47.84% and is 7.2% higher than the traditional S-CPC (Standard CPC, S-CPC) without light escape at the same aperture, and the energy flux distribution on the absorber surface is also more uniform, which is beneficial to improving system efficiency. The effective working hours of CT-CPC is higher than the S-CPC in the whole year, and the average effective working hours is 8.8 h and 5.7 h, respectively. The total annual radiation collection of CT-CPC is 3397 MJ/m2, which is 11.2% higher than the S-CPC. Furthermore, the economic analysis shows that solar CT-CPC has significant advantages and more friendly engineering application potential.

Thermodynamic analysis of solar power organic Rankine cycle based on experimental data

ABSTRACT In the current work, analytical expressions have been coded in MATLAB 9.0 linked with REFPROP 9.0, for solar-powered ORC system integrated with conventional compound parabolic concentrator using environment-friendly hexane/R1234yf zeotropic mixture to calculate hourly (8 AM to 4 PM) combined performance of solar power ORC based on experimental data. It has been observed that maximum heat gain in the collector is 5.132 × 105 W at 1 PM for the mass fraction (0.7/0.3). Moreover, maximum overall thermal efficiency 17.65% is attained at 1 PM for the mass fraction 0.3/0.7 whereas overall exergetic efficiency 49.23% is achieved at the same time for the mass fraction 0.3/0.7.

Energy and exergy analysis of solar driven recuperated organic Rankine cycle using glazed reverse absorber conventional compound parabolic concentrator (GRACCPC) system

Abstract In this research work, the computer code is written in MATLAB 9.0 which is interfaced with Refprop 9.0. in order to develop a thermodynamic model of solar driven organic Rankine cycle. A novel glazed reverse absorber conventional compound parabolic concentrator integrated with recuperated organic Rankine cycle {case (ii)} using low global warming potential and zero ozone depletion potential working fluid cyclohexane/R245fa has been proposed. The coding has been done to evaluate hourly concentrator fluid outlet temperature, heat gain in concentrator, expander output, overall thermal efficiency, overall exergetic efficiency and exergy destruction. The performance of the glazed reversed absorber conventional compound parabolic concentrator integrated with recuperated organic Rankine cycle {case (ii)} has been compared with glazed reversed absorber compound parabolic concentrator with non recuperated organic Rankine cycle {case (i)}. It is observed that overall first law efficiency improves by 40.9% and exergetic efficiency 36.28% using recuperated organic Rankine ORC {case (ii)} in comparison of non-recuperated ORC {case (i)}. The system in case {ii} has been found to be self-sustainable system and gives better result in term of thermal efficiency, environmental, space heating, day lighting and electricity use.

Energy matrices evaluation and exergoeconomic analysis of series connected N partially covered (glass to glass PV module) concentrated-photovoltaic thermal collector: At constant flow rate mode

In present analysis, a comparative study has been carried out to evaluate the annual performances of three systems or cases at constant flow rate, namely: case (i): partially covered (25% PV module) N concentrated photovoltaic thermal collectors connected in series, case (ii): fully covered (100% PV module) N concentrated photovoltaic thermal collectors in series and case (iii): N (0% PV module) convectional compound parabolic concentrator collector connected in series. Comparison for three cases has also been carried out by considering fluid namely: ethylene glycol for higher outlet temperature and better thermal performance which can be applicable for heating and steaming or small industry purpose. The embodied energy, energy matrices, uniform annual cost, exergetic cost and carbon credits are also evaluated for same systems. The energy payback time is found to be 5.58years and energy production factor is to be 0.17 on energy basis for case (iii) which is maximum. The exergetic cost has computed as 17.85Rs/kWh for 30years of life time of the system. It is observed that N conventional compound parabolic concentrator collector [case (iii)] is most suitable for steam cooking or space heating but not self-sustainable to run the dc power motor due to unavailability of electrical power.

A parametric study of a concentrating integral storage solar water heater for domestic uses

A parametric study of a concentrating integrated collector storage solar water heater was undertaken. The concentrator used was the Compound Parabolic Concentrator (CPC), an optical non-imaging device, a wider acceptance angle was used (64°) so that only occasional tracking is needed making this suitable for household purposes. The reflective concentrator was supported on a wooden cradle which comprised the two parabolas of the compound parabolic concentrator. Unlike conventional CPC systems with a large number of smaller diameter tubes, here is a single larger diameter drum was positioned at the focus of the CPC. Experimental studies were carried out and the mean collector efficiency computed on the model with an air gap introduced in the side walls (arms of the CPC). The parametric study of the design by EES at solar noon was in good agreement with the collected experimental results. The maximum thermal efficiency of the collector was 38% and the maximum water temperature attained was 53°C.

Design and performance study of truncated CPC by eliminating multiple reflections of solar radiation in hybrid CPV/T system: Highest and lowest truncation position

The height of conventional compound parabolic concentrator (CPC) increase greatly with increasing geometric concentration ratio, resulting in large reflector consumption and deteriorative optical performance. A new truncated CPC with highest truncation position called HEMR was proposed in the previous study (Xie et al., 2016), which can improve the tradeoff between cost reduction and optical performance. In order to further improve the tradeoff to make the CPC more competitive in the commercial field, the truncated CPC with lowest truncation position called LEMR is designed by eliminating multiple reflections in the present study, and the performance is researched by the material consumption assessment and Monte-Carlo simulation theoretically under the conditions of 156mm wide best concentration plane and 4 times geometric concentration ratio. The results show that the material consumption of LEMR is about 80% of HEMR while the optical performance including uniformity and optical efficiency is almost the same as HEMR, indicating that LEMR has a better tradeoff between cost reduction and optical performance and thus has more extensive application potential.

Exergy analysis of photovoltaic thermal (PVT) compound parabolic concentrator (CPC) for constant collection temperature mode

In this communication, an attempt has been made to evaluate exergy of photovoltaic thermal compound parabolic concentrator (PVT-CPC) water collector system [case (i)] for constant collection temperature mode of operation. The performance of PVT-CPC water collector systems can be analyzed in two modes namely (i) constant mass flow rate and (ii) constant collection temperature. In the present analysis, an analytical expression for mass flow rate and electrical efficiency of PV module for partially covered PVT-CPC water collector system [case (i)] have been developed to determined the performance under constant collection temperature mode. Such system will be most useful for thermal space heating of buildings to conserve fossil fuel to save environment. The comparison of proposed system with fully covered PVT-CPC water collectors [case (ii)], conventional CPC water collectors [case (iii)] and partially covered PVT water collectors [case (iv)] have also been carried out for climatic condition of New Delhi. Based on computation, it has been found that for fully covered PVT-CPC water collector system [case (ii)] (a) at high operating temperatures, instantaneous thermal efficiency has lower value in comparison with constant mass flow rate condition; (b) at high concentration ratio (C=5), higher operating temperature is achieved. The analytical expression of the electrical efficiency of the proposed system is also derived. An overall thermal and exergy analysis of PVT-CPC water collector system in terms of energy degraded into the environment and exergy destruction have also been carried out.

Preliminary Optical, Thermal and Structural Design of a 100 kWth CSPonD Beam-down On-sun Demonstration Plant

Abstract An innovative concept in which a single-tank molten salt thermal energy storage arrangement also acts as a volumetric receiver is being developed in connection with the CSPonD 2 (Concentrated Solar Power on Demand Demonstration) project. The tank is located at the focal point of a beam-down tower to act as both solar energy receiver and thermal energy storage. The relatively small angle subtended by rays emanating from the central reflector of a beam down optical system, together with the nature of solar energy absorption within the volumetric receiver, make use of a compound parabolic concentrator (CPC) or CPC-like final optical element attractive. An effective concentration of about 4 can be achieved to increase solar flux at the tank aperture from 150 to 600 suns. This paper describes preliminary designs of the CPC and tank/receiver. Optical simulations reveal that, for a given solar incident power at the tank aperture, a conical final concentrator design produces a more uniform flux distribution with better axial alignment (lower average horizontal component) of rays at its outlet compared to a conventional CPC of revolution. However the cone may require a larger outlet radius, leading to higher thermal losses through the tank aperture. With the current design of the tank, the losses through the walls correspond to 5.5% of the thermal capacity. To maximize the tank thermal efficiency, a thorough investigation will be carried out, starting with measurements of the molten salt emissivity, to determine the cone outlet radius/tank aperture and cone height that achieve maximum system efficiency with a 250-550 °C molten salt working temperature range.

Analytical characteristic equation for partially covered photovoltaic thermal (PVT) compound parabolic concentrator (CPC)

In this paper, an analytical expression for characteristic equation of a partially covered photovoltaic thermal compound parabolic concentrator (PVT-CPC) water collector system similar to Hottel–Whillier–Bliss (HWB) equation of flat plate collector has been derived. The derivation is based on basic energy balance equation for each component of partially covered PVT-CPC water collector system. The analytical result of proposed partially covered PVT-CPC water collectors [case (i)] has been compared with [case (ii)]: fully covered PVT-CPC water collectors; [case (iii)]: conventional CPC water collectors and [case (iv)]: partially covered PVT water collectors. It is observed that (a) an overall exergy efficiency of partially covered PVT-CPC water collector (25%PV) system is maximum and (b) an instantaneous thermal efficiency of conventional CPC water collector system [case (iii)] is maximum as compared to other cases.

Preliminary Experimental Comparison of the Performance of a Novel Lens-Walled Compound Parabolic Concentrator (CPC) with the Conventional Mirror and Solid CPCs

A conventional mirror compound parabolic concentrator (CPC) is limited by its half acceptance angle when pursuing a large geometrical concentration ratio with no tracking. A solid CPC, which is made from solid dielectric materials without notches, can achieve a larger half acceptance angle compared with the conventional mirror CPC of the same geometrical concentration ratio, which is attributed to the optical refraction caused by the dielectric material. However, solid CPCs are heavier and costlier. This paper presents a preliminary experiment on a novel lens-walled CPC. An experimental comparison of the conventional mirror and solid CPCs and the lens-walled CPC with the same geometrical concentration ratios of 2.5 is given for different incidence angles. Here the conventional mirror CPC chose the evaporated aluminium coating as the reflection layer, for short conventional CPC. Transparent acrylic was chosen as both the dielectric material and lens material. The three CPCs were all attached to a PV cell. Through the output characteristics of the cell, the optical performances of these CPCs can be obtained. The results showed that when the incidence angle was smaller than 35°, the optical efficiency of the lens-walled CPC remained above 46.7% and was more stable against incidence angle changes compared with the conventional CPC. It also weighed and cost less than the solid CPC. Thus, lens-walled CPC adequately combines the advantages of conventional and solid CPCs, and has great potential for use in large-scale practical applications.

An evaluation on thermal performance of CPC solar collector

The main objective of this work is the investigation and improvement of thermal performance of evacuated CPC (Compound Parabolic Concentrator) solar collector with a cylindrical absorber. Modified types of this solar collector are always combined with the evacuated glass envelop or tracking system. The conventional stationary CPC solar collector has been compared with the single axis tracking CPC solar collector in outlet temperature, net heat flux onto the absorber and thermal efficiency. Numerical model has been analyzed based on the irradiation determined actually and the results have been calculated to predict the thermal efficiency. Based on the comparison of the measured and calculated results, it is concluded that the numerical model can accurately estimate the performance of solar collectors. The result shows the thermal efficiency of the tracking CPC solar collector is more stable and about 14.9% higher than that of the stationary CPC solar collector.