Nonimaging Solar Concentrator Research Articles

Model construction and electro-thermal-hydrogen co-generation performance for multi-section compound parabolic concentrator

Non-imaging solar concentrator has many applications in solar thermal conversion and photovoltaic power generation because of its performance characteristics such as no tracking, stable light concentration, compact structure and easy integration. For this purpose, this paper conducts a study on the non-imaging concentrator based on the optimized design of the concentrating surface structure for photovoltaic electric generation, thermal energy recovery and direct-drive hydrogen production. Firstly, a theoretical construction of a mathematical model of the solar Concentrating Photovoltaic and Photo-thermal (CPV/T) system with electricity-thermal-hydrogen co-generation and a numerical solution path for the Current and Voltage (I-V) characteristic curve is presented. Moreover, an integrated CPV/T system experimental setup is constructed outdoors and its power generation, heat collection and hydrogen production processes are measured. Finally, it is found that the average electrical efficiencies of the CPV/T system are 13.03 % and 13.29 % for theory and experiment, respectively. The theoretical and experimental average thermal efficiencies are 27.47 % and 27.24 %, respectively. The theoretical and experimental average hydrogen production rates based on Maximum Power Point Tracking (MPPT) control are 19.47 ml/min and 16.11 ml/min, respectively. The research results also show that the integrally constructed CPV/T system not only achieves effective conversion of solar energy into electrical and thermal energy, but also can directly convert electrical energy into clean, stable and easily stored hydrogen energy, which has potential application prospects.

Design and Otimisation OF 2-D Static Solar Concentrator

A non-imaging solar concentrator system of reflecting surfaces redirects the solar radiation from the source to target (receiver). This work is focused on a 2-D elliptical hyperboloid geometric design of static solar collectors, though many design concepts and procedures for 2-D static solar collector is discussed in this paper. Based on the general equation for a solar concentrator, parameters vary slightly to determine the optical efficiency. 2-D MATLAB code is written to obtain the different shapes of the concentrator. The resultsof 2-D hyperboloid concentrator (2-DHC) has been reported. The optical efficiency, effective concentration ratio, receiver major axis and concentrator height have been investigated through ray trace analysis. The optimisation of the concentrator profile and geometry is also carried out, based on the geometrical concentration ratio. The maximum optical efficiency is found to be 51% and the maximum acceptance angle of ±60° was achieved

Design method of a compact static nonimaging concentrator for portable photovoltaics using parameterisation and numerical optimisation

Portable solar chargers are one of the technologies that can help to achieve universal access to electricity by 2030. However, the large number of solar photovoltaic devices required and their short life-span make achieving this goal a resource and energy intensive process. To reduce the embodied energy, the embodied carbon and the human and eco-toxicity potential of portable solar chargers, solar photovoltaic concentrators can be used. This paper proposes a new nonimaging solar photovoltaic concentrator design which has material efficiency, portability and off-grid use as its main feature. The main contribution of this paper is the design method of the new 3D nonimaging concentrator containing the parametric equation of the concentrator surfaces and the numeric optimisation of the design parameters. The developed optimisation program is based on genetic algorithms which parameters were determined experimentally in this paper. The concentrator design achieved with this method is 43% less material intensive than the most compact nonimaging solar concentrator available in literature. This design approach can be used to find concentrator designs with specific volumes, heights, concentration ratios, acceptance angles and optical efficiency. It is therefore a step towards more material efficient and more sustainable nonimaging concentrators as well as more sustainable portable solar photovoltaic systems.

Optical characterization of two-stage non-imaging solar concentrator for active daylighting system

A novel prototype of two-stage non-imaging solar concentrator (2S-NISC) for active daylighting in a building has been constructed and presented in our previous paper. In this work, the optical characteristics of the 2S-NISC have been explored to analyze the overall performance embracing maximum solar concentration ratio, percentage of energy in uniform illumination area, spillage loss, tolerance angle towards tracking error etc. using analytical formulas assisted by ray-tracing software based on designed parameters including the focal distance, f/D ratio and size of the receiver. In our simulation, we consider the case of 2S-NISC consisted of eighty primary facet mirrors of 5 cm × 5 cm each, twenty secondary facet mirrors of 8 cm × 8 cm each, and plastic optical fibers as a daylight transmitter. When focal distance is changed from 50 to 100 cm, the maximum solar concentration ratio increases from 65.1 to 70.1 suns; whilst the percentage of energy in the uniformly illuminated area shows the overall trend of decreasing when focal distance is changed from 50 to 100 cm except at focal distances 60 cm and 100 cm due to the slope error. Finally, the total tolerance angle of the 2S-NISC that allows at least 95% of energy to be collected with respect to perfect tracking is determined as 0.54˚.

Experimental performance investigations of an elliptical hyperbolic non-imaging solar concentrator with trapezoidal surface receiver for process heat applications

Abstract The use of non-imaging collectors has a wide scope in process heat applications based on its performance and economics. An experimental investigation of trapezoidal/concave cavity surface receiver (TSR) for non-imaging solar concentrating collector is carried out in this paper. The implementation of surface/coil receiver instead of tubular receiver for non-imaging collector is presented in this paper. A TSR with helical coil is developed for non – imaging concentrating collector, Elliptical Hyperbolic Collector (EHC). Experiments are carried to estimate the thermal performance of the system under various operating conditions such as two operating modes: series and parallel modes of operation of the collector, two circulation modes: passive and active modes. The stagnation temperature of the trapezoidal/concave cavity surface receiver is measured to be 118 °C on a clear sunny day in October and 102 °C on a cloudy day in February. The daily performance tests are performed under different operating conditions. Based on the experimental study, for the flow rate of 0.03 kg/min and 0.5 kg/min, the fluid outlet temperature is estimated to be 87 °C at 768 W/m2 and 49 °C at 908 W/m2 respectively. The corresponding instantaneous efficiency was calculated to be 9% and 40% respectively. The numerical model is developed to predict the temperature of the fluid along the receiver. The pressure drop across a receiver is estimated to be 9.3 kPa for a flow rate of 0.5 kg/min. Exergy analysis of the system is carried out and it ranges between 10 and 20%. The costs involved in fabricating the EHC system are compared to that of a non-imaging concentrating collector (CPC) of same aperture area. An economic analysis of the system is also carried out to study the feasibility of the system based on the life cycle savings method by estimating the annual solar savings from the EHC system. The present system can be a suitable option for low and medium temperature process heat applications.

Design optimization of ultra-high concentrator photovoltaic system using two-stage non-imaging solar concentrator

This paper presents a systematic approach for optimizing the design of ultra-high concentrator photovoltaic (UHCPV) system comprised of non-imaging dish concentrator (primary optical element) and crossed compound parabolic concentrator (secondary optical element). The optimization process includes the design of primary and secondary optics by considering the focal distance, spillage losses and rim angle of the dish concentrator. The imperfection factors, i.e. mirror reflectivity of 93%, lens’ optical efficiency of 85%, circumsolar ratio of 0.2 and mirror surface slope error of 2 mrad, were considered in the simulation to avoid the overestimation of output power. The proposed UHCPV system is capable of attaining effective ultra-high solar concentration ratio of 1475 suns and DC system efficiency of 31.8%.

Design and construction of active daylighting system using two-stage non-imaging solar concentrator

Since lighting accounts for 20% of global electricity consumption in buildings, daylighting system is an important solution to achieve energy savings in lighting and to reduce carbon dioxide emissions. However, most of the existing fiber-optics daylighting systems are expensive, sensitive to pointing error and complicated in optical design in which multi-stage focusing devices are needed to minimize non-uniformity of focused sunlight. To overcome the aforementioned problems, we propose a novel active daylighting system using two-stage non-imaging solar concentrator (2S-NISC) inspired by our previous experience in non-imaging optics. The 2S-NISC prototype consists of 80 primary facet mirrors with a dimension of 5cm×5cm each, 20 secondary facet mirrors with a dimension of 8cm×8cm each, and densely packed plastic optical fibers as a daylight distribution system. Considering the input solar power of 170W, the equivalent power conversion efficiency of 2S-NISC prototype is obtained as 22%. For economic analysis, the proposed active daylighting system using 2S-NISC with optimized collective area of 4m2 is estimated to cost USD 1231.20. Considering the interest rate of 4% and fuel inflation rate of 2%, the total payback period is determined as 6.1years, which is reasonable because the active daylighting system can last for at least 15years.

Thermal Performance of a Heat Pipe Embedded Evacuated Tube Collector in a Compound Parabolic Concentrator

Abstract This paper presents the design, development and performance evaluation of a compound parabolic concentrator for medium temperature application. In the present study Compound Parabolic Concentrator (CPC) has been used as a non-imaging solar concentrator. A single piece of evacuated tube heat pipe solar collector has been used to collect the solar radiation which is concentrated by the CPC. The condenser of the heat pipe has been directly inserted into the storage tank. The performance of the system has been evaluated for different tilt angles. Different performance parameters such as system thermal efficiency and standard power have also been evaluated in this paper.

Performance evaluation of a nonimaging solar concentrator in terms of optical and thermal characteristics

A nontracking, nonimaging solar concentrator with a low‐heat‐loss configuration was proposed, and its optical and thermal performance was investigated. The reflector has a compound parabolic and involute shape so that the absorber is heated as uniformly as possible. To eliminate heat loss by conduction and convection, the mirror and absorber are enclosed in an evacuated glass tube. The concentrator presented here was simulated for the location of Sendai, Japan, and its acceptance angle was estimated as 23.44°. A ray‐tracing model was developed to evaluate its optical and thermal performance. The average optical efficiency was evaluated by a 2‐D ray‐tracing model, and a value of 72.7% was obtained. A thermal analysis of the absorber was conducted to evaluate the temperature uniformity. The results indicate that the temperature distribution of the absorber can be considered uniform. The thermal efficiency of the proposed solar concentrator was calculated as a function of the incidence angle and absorber temperature. With a concentration ratio of 2.51, the concentrator, even at an absorber temperature of 373 K, operates with an average efficiency of 47.8%, although the absorber was assumed to have a gray surface. The concentrator's thermal efficiency was compared with that of other solar collectors, and found to be higher than that of conventional solar collectors. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 553–564, 2016

A New Generation of Medium Temperature Collector for Solar Cooling1

Prologue In the early 1970s, I began a research effort at Argonne National Laboratory to develop the nonimaging nontracking solar concentrator I had recently invented which became known as the compound parabolic concentrator or CPC. I had lots of help; in particular from lab director, Robert G. Sachs 1, Gale Pewitt, William Schertz, and many others. The lab recruited some of the best scientists in the world, in the relevant fields to work with me: for optics, Walter Welford, and for solar energy, Frank Kreith. Our first project was solar domestic hot water (DHW) for the “Breadsprings elementary school” in a Navajo Indian reservation near Gallup, NM. The collector was a threefold concentration nonevacuated CPC. Because threefold concentration can only accept solar motions for half the year, it was oriented for winter. Like every other project I ever collaborated on with Frank Kreith, it was a big success. I thought it was fitting to submit a paper on a recent “CPC” for much higher temperature (200 °C), totally stationary, and driving a double-effect absorption chiller.