Scheffler Solar Concentrator Research Articles

Performance analysis of solar immersion heater with phase change material

AbstractThermal energy storage (TES) systems have emerged as a vital solution for addressing the gap between energy supply and demand. While research on solar energy storage has primarily focused on flat‐plate collectors, limited work has been done to explore the potential of Scheffler solar concentrators. This study proposes an innovative approach to thermal energy storage using a Scheffler solar concentrator and phase change material (PCM) to address the energy needs of rural areas with limited access to electricity. Real‐time design and testing were conducted using paraffin wax as the PCM, and computational fluid dynamics (CFD) analysis was performed using the ANSYS Fluent software to determine the optimal charging and discharging times. The results indicated that the required charging time was 17 min according to the CFD analysis, while the experimental results yielded a charging time of 18 min. The results demonstrated that the proposed approach is a feasible and effective solution for meeting the energy demands of rural communities. The charging time was optimized using the response surface method, yielding an optimal charging time of 20.5 min and an optimal discharging time of 26.2 min. Overall, these findings highlight the potential of utilizing Scheffler solar concentrators and PCMs for sustainable and reliable thermal energy storage.

Experimental Study of Polyethylene Fusion by Scheffler Solar Concentrator

Aims: The present work is the use of Scheffler technology to melt plastic waste to produce composite materials using an oven type receiver. The composite material in this study contains polyethylene as a matrix and sand as reinforcement.
 Study Design: The fusion temperature of polyethylene is about 200°C and is obtained by solar concentration. The experimental plastic melting unit in Saaba (latitude 12.38° N; longitude -1.43° E), Burkina Faso, uses two 8 m² Scheffler concentrators sharing a cubic receiver. Three types of mirrors with a reflectivity of at least 90% are used as reflecting facets to equip the Scheffler dishes at the site.
 Methodology: The thermal behavior of the receiver is analyzed experimentally. Temperatures are measured on the inner and outer walls as well as the internal air temperature with 5 K-type thermocouples. When the fusion temperature is reached on the inside, we introduce the plastic waste which has been previously washed, crushed, dried and weighed.
 Results: The installed model obtained an average energy of 1.80 kW at the receiver and an average internal temperature of 251.15°C for an average irradiance of 623 W/m² during the no-load test. During the load test, an average energy of 1.34 kW and an internal temperature of 206.4°C were reached for an average irradiance of 473 W/m² and an optical efficiency of 56%. This test led to the production of two pavers of the composite material matrix with 2.2 kg of plastic waste.
 Conclusion: These results show that the profiles of the primary reflector, tracking system, and tilt axis are accurate and the maximum concentrated solar flux converges on the absorbing surfaces of the receiver. The tempered panes of the absorbing surfaces is more transparent and less emissive. Thus our device contributes to the valorization of plastic waste by using a non-polluting energy source.

Experimental Investigation of Solar based Liquid Desiccant Indirect Evaporative Cooling system

ABSTRACT Air conditioning by using vapor compression cycle is the most commonly used system although its operating energy cost is significantly high. Liquid desiccant dehumidifier with Indirect Evaporative Cooling (IEC) is another alternative suitable for hot and humid climatic conditions. The system works in two parts. In liquid desiccant dehumidifier section, moisture from humid air is removed and such air is passed through Indirect Evaporative Cooling system where air is cooled. An attempt was made to set up an experimental module with Scheffler solar concentrator to provide thermal energy for evaporation of liquid desiccant while a new type of polymer plate exchanger was used in evaporative cooling section instead of commonly used metal heat exchanger. The experimentation was carried using CaCl2 desiccant with varying flow rates between 2 and 4 l/min in dehumidifier section and reduction of relative humidity by 4 to 9% was achieved. As desiccant flow rate was increased, it resulted into higher carry over losses. Experimentally, it was found that for a flow rate of 3 l/min, the carry over losses are minimum. For this flow rate of desiccant, secondary-to-primary-air ratio of 0.8, water flow rate of 11 l/min, and air cooling by 4.7°C were achieved. Maximum wet bulb and dew point effectiveness were found to be 0.61 and 0.42, respectively, for secondary-to-primary-air ratio of 0.8. It could be concluded that a polymer plate heat exchanger-based system could be considered as efficient system than metal plate heat exchanger systems, because longer life, lighter weight, and low operating cost are the characteristics of polymers.

Experimental performance analysis of an improved receiver for Scheffler solar concentrator

This study presents the experimental analysis of the convex receiver for a Scheffler solar concentrator. The solar receiver with three different arrangements was tested for steam generation. Thermal performance is determined by energy analysis. An analysis of the receiver with the first arrangement revealed approximately 42% heat losses from the bare receiver. Then a convective heat loss is mitigated by providing a cavity on the receiver. However, no significant improvement in thermal efficiency is observed. Further, the tube coil is fixed on the cavity’s inner wall and water circulated through the coil to harvest the maximum energy. The average intensity of solar beam radiation was 638 W/m2 during the experimentation time of 9:00 to 15:00 h. The stagnation test result estimated that 109 W/m2 K overall heat loss coefficient of the receiver. The receiver’s energy efficiency with the first, second, and third arrangements was obtained to be 57.71%, 60.93%, and 68.03%, respectively, under the same operating conditions. In all receiver arrangements, the third arrangement has been found attractive for enhancing the parabolic dish concentrator’s efficiency.

Integrated system of flat plate collector and Scheffler solar concentrator for enhancing thermal efficiency and steam generation rate

ABSTRACT Scheffler concentrators are used for heating water and producing steam. Flat plate collectors are normally used for low-temperature water heating. In this research work, the performances of a flat plate collector and a Scheffler solar concentrator were studied individually. After careful study of the results, an integrated system was developed to enhance the efficiency. Also, the experimental results were checked and validated through CFD. Flat plate collector shows higher efficiency in heating water up to 50∼60°C and hence this feature is used for pre-heating the water fed to the Scheffler concentrator. As a result, Scheffler concentrator’s thermal efficiency is improved significantly by about 6%. The steam generation rate of integrated system is also increased when compared to that of individual Scheffler concentrator. This study uses experimental works along with numerical methods to substantiate the results providing a good visualisation of the receiver’s performance.

Studies on Scheffler solar concentrator to optimise thermal efficiency

Parametric analysis of Scheffler solar concentrator system is performed for improvement in thermal efficiency. A Scheffler concentrator of size 2.7 m2 has been used for experimentation. Cylindrical and conical shape receivers each with 8-liter capacity was used for experimentation which serve a dual purpose of absorber as well as steam storage device. The thermal efficiencies with different receivers were calculated on the basis of parameters like shape of receiver, initial heating of inlet water, tilting angle of receiver and receiver with the glass cover for steam pressures up to 3 bars. Cylindrical receiver has the maximum efficiency of 56.64% in case of initial heating of water (50°C) and conical receiver has the maximum efficiency of 76.04% in case of tilting position of receiver (45°) at 1 bar. Response surface method was used to optimise the thermal efficiency of receiver. A general mathematical model for obtaining thermal efficiency has been developed for both types of receivers in terms of incident average solar radiation and mass flow rate of steam. The optimum predicted value of thermal efficiency is calculated from the general mathematical model and there is a good agreement found between the experimental and predicted results.

Thermal performance of cubical receiver with trapezoidal ice-pot for melting of ice at high altitude regions based on Scheffler solar concentrator

ABSTRACT The thermal performance of cubical receiver with a trapezoidal ice-pot has been investigated with the aim to generate hot water by melting of ice at high altitude regions (Leh Ladakh). In the experimental set-up, one hollow mild steel cubical receiver (filled with heat transfer fluid) with the ice-pot and four different types of solid cubical receivers with the ice-pot are used to melt the ice with direct heating in minimum time. The radiations are focused on receiver with the help of a 1 m2 Scheffler concentrator that is exposed to the atmospheric situations of NIT Kurukshetra. The results from the designed set-up are obtained that the frozen ice at −4°C melts completely, converting into water and the maximum temperature of the water attained in hollow cubical receiver, solid receiver (granite), solid receiver (dholpur stone), solid receiver (concrete) and solid receiver (mild steel) is 42.5°C, 32.9°C, 49.5°C, 30.2°C and 52.7°C, respectively.

Experimental investigation of ice‐chamber for melting of ice based on Scheffler solar concentrator for high altitude regions

AbstractThis experimental analysis was performed with the aim to melt the ice into hot water at very high altitude regions such as Leh Ladakh. Three different designs of ice‐chamber were used to melt the ice with direct heating in minimum time. The radiations were focused on the receiver with the help of 1 m2 Scheffler solar concentrator exposed to the atmospheric situations of NIT Kurukshetra. The Scheffler solar concentrator was fabricated with fiber‐reinforced plastic material. The fabrication process is discussed in detail. The results obtained from the design showed that the ice frozen at −5°C completely melted, converting into water. The maximum temperature of water attained in the ice‐chamber with receiver 1 (circular plate with fins), 2 (CPC with fins), and 3 (copper crucible) was 57.7°C, 64.3°C, and 67.4°C, respectively.

Economic analysis of solar thermal system for melting of ice at high altitude regions using Scheffler solar concentrator

ABSTRACT The present paper deals with the economic investigation of hot water generation from melting of ice through Scheffler solar concentrator at high altitude regions like Leh Ladakh in India. For determination of the cost incurred per litre in terms of the Indian Currency, several factors have been studied and evaluated. In all three examined cases, for every respective case, the undeviating technique is adopted. The experimentation is performed in the atmospheric conditions of National Institute of Technology, Kurukshetra, Haryana, India. Exclusive economics of yearly cost per litre is achieved for the generation of hot water from ice at high altitudes by making use of direct heating process.

Technical analysis of an oven with coupled receiver for scheffler solar concentrator tested under cloudy weather conditions

Most of the solar collectors experiments are carried out under clear-sky conditions to evaluate the maximum performance of collectors, even though this condition is not critical for some uses, such as cooking. The optical and thermal performance of a solar oven heated by Scheffler concentrator is here analyzed in more adverse weather conditions. The receiver for conversion and heat transfer of the concentrated solar energy is coupled to an oven specially developed for this work. The Scheffler concentrator geometry is a lateral cut angled 43.23° of a paraboloid matrix, and it works in a two-axis tracking system, to always maintain its focal image at the stationary receiver with the progression of the Earth rotation and solar declination movements. A model for distributing the daily radiation over the hours is used to compare the results. The time-constant experimental method is considered. The heating and cooling tests were carried out at the official local time. The maximum temperature achieved by the absorber was 328°C, and the maximum average temperature in the oven was 150°C. The results for heat loss factor were evaluated, and the trends for thermal efficiency and optical efficiency factor were analyzed for the system considered

A Scheffler solar concentrator heat transfer model used in forced-circulation ice melting system at high-altitude regions

The thermal performance of three differently designed receivers has been investigated with the aim to generate hot water by melting of ice in the ice chamber at high-altitude regions as Leh ladakh, India [34.15° (latitude) North, 77.57° (longitude) East]. In this experimental set-up, the solar radiations are concentrated on receiver (rectangular, spiral and conical) by 1 m2 Scheffler solar concentrator. The receiver is coated with graphite to escalate the absorptivity of solar radiations. The available solar heat at the receiver is transferred to the ice chamber by forced circulation of the heat transfer fluid (Globaltherm Omnitech). The horizontal cylindrical type ice chamber is used for melting the ice into water that can be used for indoor water heating. The experiment is performed in atmospheric conditions of NIT Kurukshetra, India. By the experimental results, it is found that the frozen ice at − 4 °C is completely melted into water and the maximum temperature of the water attained in the ice chamber by using rectangular, spiral and conical receivers is 47.8 °C, 50 °C and 53.6 °C, respectively.

Thermal performance of the steam boiler based on Scheffler solar concentrator for domestic application: Experimental investigation

ABSTRACT In this paper, a working setup of Scheffler solar concentrator (SSC) for the steam generation application has been investigated experimentally. An experimental setup of SSC having an aperture area of 1.54 m2 and steam boiler (or receiver) area of 0.0324 m2 was set up and tested for steam generation. The steam boiler 1, 2 and 3 with different arrangements were used for steam generation. During sunshine hours, the steam boiler 1, 2 and 3 are placed at the focus of SSC at 11:00 hour up to 2.1 bar (gauge) reached. The dryness fraction of the steam boiler 1, 2 and 3 have been calculated as 43.51%, 71.61%, 96.32% and the thermal efficiency 18.40%, 14.53% and 14.09%, respectively. In all the steam boiler arrangements, it has been found that in the steam boiler 3 produced a high quality of steam.

Effect of Wind Flow on Convective Heat Losses from Scheffler Solar Concentrator Receivers

Receiver is an important element of solar concentrator system. In a Scheffler concentrator, solar rays get concentrated at focus of parabolic dish. While radiation losses are more predictable and calculable since strongly related to receiver temperature, convective looses are difficult to estimate in view of additional factors such as wind flow direction, speed, receiver geometry, prior to current work. Experimental investigation was carried out on two geometries of receiver namely cylindrical and conical with 2.7 m2 Scheffler to find optimum condition of tilt to provide best efficiency. Experimental results showed that as compared to cylindrical receiver, conical receiver gave maximum efficiency at 45° tilt angle. However effect of additional factors like wind speed, wind direction on especially convective losses could not be separately seen. The current work was undertaken to investigate further the same two geometries using computation fluid dynamics using FLUENT to compute convective losses considering all variables such at tilt angle of receiver, wind velocity and wind direction. For cylindrical receiver, directional heat transfer coefficient (HTC) is remarkably high to tilt condition meaning this geometry is critical to tilt leading to higher convective heat losses. For conical receiver, directional average HTC is remarkably less to tilt condition leading to lower convective heat loss.

The regeneration of various saturated solid and novel composite desiccant using Scheffler solar concentrator: an experimental investigation

ABSTRACTIn this article, the regeneration of various saturated desiccant (wet basis) such as silica gel, activated alumina, molecular sieve, and novel composite desiccant using Scheffler solar concentrator (SSC) has been proposed. The regeneration performance is greatly affected by solar radiation, surface temperature of desiccant, wind velocity, and initial moisture content. SSC having aperture area of 1.54 m2 is used for regeneration of 0.620 kg sample of each desiccants. During the investigation, it has been found that silica gel has maximum moisture content (dry basis), i.e. 0.2944 followed by molecular sieve, novel composite, and activated alumina having moisture content 0.2205, 0.19, and 0.0671, respectively. The maximum regeneration rate of 0.07440 kg/hr is achieved in novel composite and maximum weight loss percentage of 22.74% is achieved in silica gel. Regeneration time taken by silica gel, activated alumina, molecular sieve, and novel composite desiccant are 160, 90, 140, and 110 min, respectively.

Numerical and Experimental Analysis of Scheffler Concentrator Receiver for Steam Generation Using Phase Change Material

This paper proposes a design of receiver of a scheffler dish solar concentrator which uses the phase change material to store the thermal energy. For this, water is used for direct steam generation from the receiver. The proposed model consists of a phase change material (PCM) present in between the inner and outer cylinder of the copper receiver. A binary mixture commonly known as solar salt (60% NaNO 3 -40% KNO 3 ) is used as PCM for analysis. It helps to get rid of fluctuations due to sudden weather changes. Scheffler solar concentrator of 16 m 2 area with a fixed focus is used to concentrate the solar radiations to the receiver. The purpose of this study is to see the effect of PCM on steam generation and compare it with the results obtained without the use of solar salt in the receiver experimentally as well as numerically using Finite Element Method. Numerical analysis was performed using Transient thermal analysis in Ansys-16 and experimental investigations were performed. Results showed that the use of PCM in the receiver not only increases the mass flow rate of the steam but also the duration of steam generation by storing the thermal energy.

Mathematical modelling of solar drying of a novel composite desiccant

ABSTRACTIn this article, the regeneration (drying) and mathematical modelling of moisture ratio of a novel composite desiccant using the Scheffler solar concentrator have been proposed. The regeneration performance is significantly affected by solar radiation, the surface temperature of the desiccant, atmospheric wind speed and initial moisture content. The changes in mass and drying parameters are recorded at an interval of every 10 min. Drying curve obtained from the experimental data is fitted to 12 drying models to explain the behaviour of the novel composite desiccant drying. The Midilli and Kucuk model is the best descriptive model in this case with a coefficient of correlation (R) of 0.9942, and a root mean square error analysis of 0.03124. It takes 100 min in the saturated regeneration of the novel composite under subjected conditions and 15.97% weight reduction is achieved.

Design, development and experimental results of a solar distillery for the essential oils extraction from medicinal and aromatic plants

Distillation of medicinal and aromatic plants for essential oils extraction can be done by utilizing heat in medium temperature range. These essential oils are used in foods, medicines and cosmetics etc. and are money earning business for the farming community. This research is focused to develop an on-farm solar distillery for the processing of different plant materials. The system comprises of a Scheffler reflector and a complete set of distillation system. An 8m2 ‘projected area of the Scheffler solar concentrator was coupled with the distillation still for the extraction of essential oils. In this paper, a complete mathematical description has been explained to design different components of solar distillation system. In order to provide a fixed focus on a receiver from morning to evening and in summer and winter, flexible crossbars have been used to achieve the desired shapes of the reflector. The paper also covers all the details regarding design, development, site specific installation and tracking system etc. Different types of Florentine apparatuses were used to separate the essential oils from the hydrosol. Necessary instrumentation was used for the performance evaluation of solar distillery. The system was capable of producing 300–450°C temperature at the receiver section within the beam radiation range of 800–850Wm−2. The efficiency of solar distillery was calculated to be 33.21% with 1.548kW thermal power available for processing in the distillation still. The system was operated for 10–12h a day during summer. About 18.58kWh thermal energy was obtained from the solar distillery in a sunny day. For the processing of 10kg batch, an average 3.5kWh energy was consumed. In this way, about 4–5 batches were processed successfully using different kinds of plant materials with 10–20kg per batch. The research concluded that different kind of medicinal and aromatic plants could be processed effectively using solar distillery.

Effect of micro-level and macro-level factors on adoption potential of solar concentrators for medium temperature thermal applications

Solar concentrators can be used for medium temperature (80–250°C) thermal applications for replacement of fossil fuels. The acceptance of any technology is driven by both the technical features and the economic benefits. Economic benefits are also governed by the performance and the investment requirement. A model is developed for estimation of market acceptance of a solar concentrator based on economics. This model is illustrated for two commercially offered solar concentrators in India, namely, fixed focus 16m2 Scheffler concentrator and moving focus 160m2 ARUN concentrator with Fresnel arrangement of reflectors. Payback periods for the two concentrators are estimated for the same operating conditions and acceptance of each is estimated. The effect of government support on acceptance is also studied. The adoption potential of Scheffler solar concentrator is 8% under present conditions which can be improved to 38% with government support while for ARUN, it can be improved from 1% to 11% with government support. The model can be used to identify the effect of government support and conventional fuel costs on the potential adoption of any solar concentrator. In the model, micro-level technology factors and macro-level market effects and trends are considered for evaluation of the adoption potential of a solar concentrator type.