Potential of performance improvement of concentrated solar power plants by optimizing the parabolic trough receiver

This paper proposes a comprehensive thermodynamic and economic model to predict and compare the performance of concentrated solar power plants with traditional and novel receivers with different configurations involving operating temperatures and locations. The simulation results reveal that power plants with novel receivers exhibit a superior thermodynamic and economic performance compared with traditional receivers. The annual electricity productions of power plants with novel receivers in Phoenix, Sevilla, and Tuotuohe are 8.5%, 10.5%, and 14.4% higher than those with traditional receivers at the outlet temperature of 550°C. The levelized cost of electricity of power plants with double-selective-coated receivers can be decreased by 6.9%, 8.5%, and 11.6%. In Phoenix, the optimal operating temperature of the power plants is improved from 500°C to 560°C by employing a novel receiver. Furthermore, the sensitivity analysis of the receiver heat loss, solar absorption, and freeze protection temperature is also conducted to analyze the general rule of influence of the receiver performance on power plants performance. Solar absorption has a positive contribution to annual electricity productions, whereas heat loss and freeze protection temperature have a negative effect on electricity outputs. The results indicate that the novel receiver coupled with low melting temperature molten salt is the best configuration for improving the overall performance of the power plants

The study of a seasonal solar cchp system based on evacuated flat-plate collectors and organic rankine cycle

The demands of cooling, heating and electricity in residential buildings are varied with seasons. This article presented a seasonal solar combined cooling heating and power (CCHP) system based on evacuated flat-plate collectors and organic Rankine cycle. The heat collected by evacuated flat-plate collectors is used to drive the organic Rankine cycle unit in spring, autumn and winter, and drive the double-effect lithium bromide absorption chiller in summer. The organic Rankine cycle condensation heat is used to yield hot water in spring and autumn, whereas supply heating in winter. The system thermodynamic performance was analyzed. The results show that the system thermal efficiency in spring, autumn and winter, ηsys, I, increases as organic Rankine cycle evaporation temperature, T6, and evacuated flat-plate collectors outlet temperature, T2, decrease. The maximum ηsys, I of 67.0% is achieved when T6 = 80 °C and T2 =100 °C. In summer, the system thermal efficiency, ηsys, II, increases first and then decreases with the increment of T2. The maximum ηsys, II of 69.9% is obtained at T2 =136 °C. The system output performance in Beijing and Lanzhou is better than that in Hefei. The average output power, heating capacity, hot water and cooling capacity are 50-72 kWh per day, 989-1514 kWh per day, 49-57 ton per day and 1812-2311 kWh per day, respectively. The system exergy efficiency increases from 17.8-40.8% after integrating the organic Rankine cycle unit

Spectral self-adaptive absorber/emitter for harvesting energy from the sun and outer space

The sun (~6000 K) and outer space (~3 K) are the original heat source and sink for human beings on Earth. The energy applications of absorbing solar irradiation and harvesting the coldness of outer space for energy utilization have attracted considerable interest from researchers. However, combining these two functions in a static device for continuous energy harvesting is unachievable due to the intrinsic infrared spectral conflict. In this study, we developed spectral self-adaptive absorber/emitter (SSA/E) for daytime photothermal and nighttime radiative sky cooling modes depending on the phase transition of the vanadium dioxide coated layer. A 24-hour day-night test showed that the fabricated SSA/E has continuous energy harvesting ability and improved overall energy utilization performance, thus showing remarkable potential in future energy applications.Comment: 15 pages, 4 figure

Performance study and comparative analysis of traditional and double-selective-coated parabolic trough receivers

Based on the simulated non-uniformity solar radiation flux distribution of the absorber by the Soltrace software using the Monte Carlo Ray-Trace Method, an innovative parabolic trough solar receiver that employs two solar selective coatings with different properties on the outer surface of the absorber is proposed. The concentration ratio and absorber temperature that influence optimal cut-off wavelengths of the solar selective coatings are quantitatively analyzed to optimize the property of the coating. The optimal cut-off wavelength increases with the concentration ratio, but drops with the increasing absorber temperature. The heat transfer process of receivers is numerically simulated to predict the thermal performance of evacuated receivers based on spectrum parameters heat transfer model. Heat loss simulation results show that: the double-selective-coated receiver can reduce heat loss and boost the collecting efficiency significantly compared with PTR70 receiver. When the temperature of absorber is 500 °C, the double-selective-coated receiver can reduce heat loss by 157.8 W/m and increase the collecting efficiency from 64.7% to 68.1%. The System Advisor Model annual simulation results indicate that double-selective-coated receivers can decrease the levelized cost of electricity of concentrating solar plants by 2.78%–7.34%, and increase electricity production by 2.94%–8.21% compared with traditional PTR70 receivers

Numerical investigation and experimental validation of the impacts of an inner radiation shield on parabolic trough solar receivers

Conventional parabolic trough solar receivers are widely used to harvest heat energy at temperatures ranging from 400 °C to 550 °C. However, high temperatures cause excessive heat loss in solar receivers. Two types of novel solar receivers with an inner metal radiation shield (RS), one with solar selective absorbing coating on the outer surface and one without, were proposed and constructed to improve the thermal performance of solar receivers. Experiments were conducted in an enthalpy difference lab, and mathematical models with spectral radiant distributions were established to predict the thermal performance of the solar receivers. A comparison between the simulated and experimental results showed satisfactory consistencies. Predictions were obtained using the models with the root mean square deviation of less than 6%. The novel solar receiver without solar selective absorbing coating on the outer surface of the RS showed superior performance at absorber temperatures exceeding 550 °C. At the absorber temperature of 600 °C, the percentage of heat loss reduction of the receiver with solar selective absorbing coating and of that without reached 23.4% and 24.2%, respectively

Rapid Determination of Amino Acids of <i>Nitraria tangutorum</i> Bobr. from the Qinghai-Tibet Plateau Using HPLC-FLD-MS/MS and a Highly Selective and Sensitive Pre-Column Derivatization Method

Amino acids are indispensable components of living organisms. The high amino acid content in Nitraria tangutorum Bobr. fruit distinguishes it from other berry plants and is of great significance to its nutritional value. Herein, using 10-ethyl-acridine-3-sulfonyl chloride as a fluorescent pre-column labeling reagent, a method for the efficient and rapid determination of amino acid content in N. tangutorum by pre-column fluorescence derivatization and on-line mass spectrometry was established and further validated. The limits of detection (signal-to-noise ratio = 3) were between 0.13 and 1.13 nmol/L, with a linear coefficient greater than 0.997 and a relative standard deviation between 1.37% and 2.64%. In addition, the method required a short analysis time, separating 19 amino acids within 20 min. Subsequently, the method was used to analyze the amino acid content of Nitraria tangutorum Bobr. from tissues retrieved from seven regions of the Qinghai-Tibet Plateau. Nitraria tangutorum Bobr. was shown to contain a large amount of amino acids, with the total content and main amino acid varying between the different tissues. This research supports the nutritional evaluation, quality control, and development and utilization of Nitraria tangutorum Bobr

Performance analysis on a high-temperature solar evacuated receiver with an inner radiation shield

A novel solar evacuated receiver as the key part of parabolic trough collector (PTC) was designed and constructed by authors. The novel evacuated receiver (NER) with an inner radiation shield can significantly decrease heat loss at higher operating temperatures when compared with the traditional evacuated receiver (TER). A thermodynamic model relying on the spectrum parameter model of radiation heat transfer was developed to predict the performances of evacuated receivers. Also, experiments using the novel evacuated receiver and traditional evacuated receiver were conducted in the laboratory under different parametric conditions to validate results obtained for the simulation. A comparison between simulation results and experimental data demonstrated that the model was able to yield satisfactory consistencies and predictions to a reasonable accuracy (with the root mean square deviations less than 6%). Results indicated that the novel evacuated receiver has a role in decreasing the total heat loss of receiver compared with the traditional receiver when the working temperature is higher than 296 °C, the heat loss reduction percentage of the novel evacuated receiver reaches 19.1% when the operating temperature is 480 °C, and the value of this percentage would be greater at higher working temperatures

Design and analysis of an innovative concentrated solar power system using cascade organic Rankine cycle and two-tank water/steam storage

Direct steam generation (DSG) solar power systems have the potential to improve heat collection performance and reduce capital cost. One challenge of the DSG solar thermal power technology is the unsteadiness of steam generation and power conversion under fluctuating solar radiation. A novel concentrated solar power generation system is proposed. It has three features: two-phase water/steam as heat transfer fluid, two-tank water storage, and cascade organic Rankine cycle (CORC) with a mixing chamber as power block. Steam is produced in the solar field and condensed in a high temperature tank, while an organic fluid replaces water for power conversion. The system enables smooth cycle operation by resilient control strategy and can tackle the challenge associated with wet steam turbines. It can tolerate lower purity of water/steam that only serves as the heat transfer fluid, thereby reducing the technical requirement. Thermodynamic performance in the normal operation condition and heat discharge process are assessed. The influences of ORC working fluid and storage tank size are examined. Results indicate that the mixing chamber temperature plays a crucial role in thermal efficiencies of both charge and discharge processes, storage capacity, and overall performance. A CORC efficiency of about 27.4% is achievable. The equivalent heat-to-power efficiency ranges from 13.35% to 18.81%, depending on the ORC fluid and volume of the storage tank. The novel system has an efficiency comparable to a conventional DSG system while a lower technical requirement in heat collection and power generation

Preliminary performance study of a high-temperature parabolic trough solar evacuated receiver with an inner transparent radiation shield

Solar evacuated receiver as a key part of parabolic trough collector (PTC) suffers considerable heat loss at high operating temperature, which exerts significantly negative effects on the overall performance of PTC system. Based on the fact of maldistributed solar irradiation around the inner absorber tube, a novel solar evacuated receiver with an inner transparent radiation shield (TRS) is proposed and designed. The heat loss of the proposed solar evacuated receiver is numerically studied by the established heat transfer model based on the spectral parameters. The heat-collecting efficiency of a commercial UrssaTrough solar collector installed with PTR 70 receivers using therminol VP-1 as heat transfer fluid is investigated to validate the performance of the proposed solar receiver. Moreover, the influences of the property parameters of films on the two sides of the TRS on the solar receiver are also studied. Comparisons between simulated and experimental results show the differences of their heat-collecting efficiencies are lower than 1%, which demonstrates that the model can yield satisfactory consistency with the experimental results. The simulation results show that the novel receiver exhibits dramatically superior thermal performance to that of the traditional receiver. The heat loss reduction percentages of the novel receiver can reach approximately 15.7% and 14.9% when the absorber temperatures are 400 °C and 600 °C, and the thermal efficiency can be enhanced by 0.93% and 4.42% at inlet temperatures of 400 °C and 580 °C, respectively

Energetic and exergetic analyses on structural optimized parabolic trough solar receivers in a concentrated solar–thermal collector system

High collecting temperature in parabolic trough collectors (PTCs) induces considerable radiative heat loss of solar receivers, which causes significant negative effects on heat-collecting efficiency. Structural optimized solar receivers with inner radiation shield achieved superior thermal performance for reducing heat loss. Based on widely commercial EuroTrough and PTR70 solar receivers, the optimized solar receivers are numerically applied to a small thermal-collection field with 72 m loop using molten salt as heat transfer fluid to validate their enhanced overall performance. Mathematical models relying on spectrum parameter calculation and working fluid volume unit method are established to simulate the energetic and exergetic performances of the solar receivers. The influence of solar irradiance on parabolic trough collector system is studied, and all-day system efficiencies in different areas in China are investigated to validate the performance of the proposed solar receivers in real condition. Results show that the PTCs with novel solar receivers exhibit outstanding energetic and exergetic performances compared with conventional receivers. The heat loss reduction percentage of the novel receivers reaches approximately 24.0% when the absorber temperature is 600 °C. The heat-collecting efficiency and exergetic efficiency are effectively raised by 7.1% and 4.7%, respectively, at an inlet temperature of 580 °C