This paper presents the comparison study of three different schemes of a novel solar tower polygeneration (STPG) system, which integrates super-critical CO2 (S-CO2) Brayton cycle, organic Rankine cycle (ORC) driven hydrogen production block, and multi-stage flash (MSF) desalination technology to achieve collaborative production of electric power, hydrogen, oxygen and freshwater. KCl/MgCl2 molten salt is selected as the heat transfer fluid in the solar island. By using Ebsilon software, operation, exergy, economic and environmental analyses of three different STPG system schemes are conducted. The results show that for all the three different STPG system schemes, the solar island, S-CO2 Brayton cycle, hydrogen and freshwater production blocks can coordinatively achieve the effective operation for both short- and long-terms. Scheme 2, in which the evaporator of ORC is arranged between the high- and low-temperature recuperators of the S-CO2 Brayton cycle, has the best exergy and economic performances. The output power and Brayton cycle efficiency of Scheme 2 are 57.7 MW and 47.7%. The hydrogen, oxygen and freshwater production rates of Scheme 2 are 73.5 kg/h, 588.0 kg/h and 316.4 t/h, respectively. The levelized costs of electricity, hydrogen and freshwater of Scheme 2 are 0.082 $/kWh, 6.02 $/kg and 1.46 $/t, and the net present value is 843.0 million USD. Assuming the STPG system is replacing 100.0% coal-fired driven production, the annual emission reductions of soot, SO2, CO2 and NOx of Scheme 2 are 1330.9 t, 2287.5 t, 92,885.8 t and 2162.7 t, respectively. This work provides certain reference for design and optimization of solar tower polygeneration systems in the future.

Solar energy is meaningful for energy structure transformation. This paper presents a comparison study of four different schemes of a novel solar tower receiver multigeneration system for providing electric power, hydrogen and oxygen. Super-critical CO2 Brayton cycle and organic Rankine cycle driven hydrogen production block are coupled in the proposed multigeneration system. Operation, exergy, economic and environmental analyses of four different multigeneration system schemes are conducted by using Ebsilon software, and the results show that Scheme 1, in which the evaporator of organic Rankine cycle is arranged downstream of the main heat exchanger of Brayton cycle, has the best exergy performance as it has the smallest overall exergy loss (273.99 MW) and highest exergy efficiency (26.7 %). By contrast, Scheme 4, in which the evaporator is used as the pre-cooler of the Brayton cycle, has the best operation, economic and environmental performances simultaneously. For Scheme 4, the output power, Brayton cycle efficiency, hydrogen and oxygen production rates are 64.32 MW, 50.53 %, 181.2 kg h-1 and 1449.6 kg h-1, levelized costs of electricity and hydrogen are 0.0687 $center dot kWh-1 and 4.44 $center dot kg-1, and the net present value and investment recovery period are 984.2 $M and 7.25 years. And annual emission reduction quantities of CO2, soot, SO2 and NOx of Scheme 4 are 88723.3 t, 1271.3 t, 2184.9 t and 2065.8 t.

Against the backdrop of global energy transition and increasingly severe environmental conditions, developing clean and efficient energy systems has become crucial. This study aims to investigate a solar tower receiver tri-generation (STRT) system combining supercritical CO2 (S-CO2) Brayton cycle and organic Rankine cycle (ORC), with the objective of achieving the production of electricity, hydrogen, and oxygen. The modeling of the STRT system is completed by using Ebsilon, and the performance of the STRT system is analyzed. The results show that the output power and efficiency of the S-CO2 Brayton cycle are 62.29 MW and 48.3%, respectively. The net power and efficiency of ORC are 8.02 MW and 16.35%. The hydrogen and oxygen production rates of the STRT system are 183.8 kg·h−1 and 1470.4 kg·h−1, respectively. The STRT system shows stable and effective operation performance throughout the year. Through the exergy analysis, the exergy losses and exergy efficiencies of different components of the STRT system are obtained. The solar tower has the largest exergy loss (218.85 MW) and the lowest exergy efficiency (63%). The levelized electricity cost and the levelized hydrogen cost of the STRT system are 0.0788 USD·kWh−1 and 2.97 USD·kg−1 with a recovery period of 8.05 years, which reveal the economic competitiveness of the STRT system.

Some abundant renewable low-temperature energy sources, such as low-concentration ratio solar energy and geothermal energy, have not been effectively utilized, and researchers are making efforts to develop low-temperature renewable energy power generation technologies. Organic Rankine cycles (ORCs) are suitable for medium- and low-temperature heat utilizations, and can be widely applied in low-grade thermal energy power generation. Aiming at providing a reference for future research and development of ORC technologies, a comprehensive research review of ORC-related renewable energy systems is conducted in this paper. Relevant issues of three types of ORC-related renewable energy systems (single energy-driven single-product ORC systems, single energy-driven poly-generation systems with ORC, and multi-energy combined systems with ORC) are presented, including typical system configurations, advantages, shortcomings, research progress and future research directions.

This paper presents the design of a novel concentrated solar dual-runner photovoltaic/thermal (DPVT) system with multi-mirror concentrator and nanofluid optical filter. The integrated evaluation of optical, operational, economic and environmental protection performances of the DPVT system is conducted. Ag/water nanofluid is used as the optical filter, of which the average transmissivity and absorptivity are 67.21 % and 32.79 %. The ray tracing method is experimentally validated by using an experimental setup and then employed to simulate the solar concentration process, revealing the technical feasibility of the DPVT system. The results also reveal the acceptable sun tracking error adaptability of the DPVT system. The ray tracing and computational fluid dynamics (CFD) coupled method is used to evaluate the operation performance of the DPVT system. The results reveal that the electric power, overall electric, thermal and overall exergic efficiencies of the DPVT system are 1538.94 W, 17.95 %, 71.72 % and 23.48 %, respectively. The appropriate decrease in the inlet nanofluid flow velocity and environmental temperature, or the proper increase in the inlet nanofluid temperature can improve the overall operation performance of the DPVT system. For the DPVT system, the levelized cost of electricity is about 0.029 $/kWh, the annual fuel cost saving for supplying heat can be 162.8 $, and annual emission reductions of soot, SOx, CO2 and NOx are 48.8 kg, 83.8 kg, 3403.5 kg and 79.2 kg, respectively.

The geometric configuration of the frame significantly affects the surrounding air flow and heat transfer characteristics of photovoltaic (PV) panels, thereby impacting the photo-electric performance of PV panels. The main novelty of this study is the comprehensive effect evaluation of frame perforation on passive air cooling performance, thermal management and electric performance of PV panels. By using three-dimensional computational fluid dynamics (CFD) simulations, this study systematically evaluates the effects of different perforation conditions on the flow field and PV panel temperature distribution under passive air convection conditions, including nonperforated, single-side, dual-side, tri-side and four-side perforation conditions. The evaluated hole shapes include circular and rectangular. An experimental setup is built to verify the simulation model of PV panel cooling. The thermal and electric performances of PV panels with a tilt angle of 11.0 degrees in seventeen different frame perforation cases are compared. The results show that some perforation patterns enhance the heat dissipation of PV panels to different extents. When the wind speed is 6.0 m/s and the incident solar intensity is 900.0 W/m2, among the seventeen evaluated cases, the best PV panel frame perforation pattern is the frame with eight circular holes on the windward side, and the output electric power and photo-electric conversion efficiency of that PV panel are 24.18 W and 15.9 %. Compared with the non-perforated PV panel with a tilt angle of 0.0 degrees under the 6.0 m/s wind speed condition, it can achieve a PV panel temperature reduction of 5.44 degrees C. And in contrast with the non-perforated PV panel under the no-wind condition, it can bring an average PV panel temperature reduction of 37.8 degrees C and an increase in photo-electric conversion efficiency of 2.89 %.

In this paper, the main novelty is the proposal and performance analysis of a novel selectively filtered nanofluid spectrum semi-trough solar concentrated photovoltaic-thermal (SPVT) system. Experimental preparation and optical tests of Ag-CoSO4/water nanofluid are conducted. The selected nanofluid for the SPVT system has an average absorptance of 53.5% and an average transmittance of 46.5% in 250.0 similar to 2500.0 nm. The optical analysis results show that the optical efficiency of the SPVT system is 94.3% under the optical filtering condition. When the solar tracking error increases to 0.3 degrees, the optical efficiency of the SPVT system can still be kept at 84.8%. This means that the SPVT system has relatively good adaptability on solar tracking error. The operation performance analysis results indicate that under the optical filtering condition, the electric power and photo-electric efficiency of the PV subsystem are 392.1 W and 30.9%, and the thermal efficiency of the SPVT system is 40.7%. Effects of four factors on the thermal performance of the SPVT system are evaluated, which are the inlet nanofluid flow velocity and temperature, environmental temperature and convection heat transfer coefficient between the nanofluid flow channel and air. The results show that the thermal performance of the SPVT system can be improved by properly increasing the inlet nanofluid flow velocity and environmental temperature or by reducing the inlet nanofluid temperature and convection heat transfer coefficient between the nanofluid flow channel and air. When the inlet nanofluid flow velocity increases from 0.002 m/s to 0.004 m/s, the thermal efficiency of the SPVT system increases from 40.9% to 50.7%, and with the inlet nanofluid temperature increased from 6.0 degrees C to 14.0 degrees C, the thermal efficiency decreases from 48.6% to 45.6%. The results of this paper can provide certain reference for research and development works of solar PVT systems in the future.

Multi-energy complementary technology is meaningful for promoting the development of solar energy utilization, and the main novelty of this paper is the proposal of a novel linear Fresnel reflector solar-gas combined (LSGC) system which utilizes the organic Rankine cycle driven proton exchange membrane hydrogen production (PEM-HP) subsystem as well as is designed for generating electricity and hydrogen. By using the Ebsilon, the operation performance and exergy analyses of the LSGC system are launched. The results show that the output power and electric efficiency of the LSGC system are 424.8 MW and 45.4%. The solar field contributes a power of 34 MW. The hydrogen production rate of the LSGC system is 182.88 kg/day. The solar field, GTCC and PEM-HP section can reach the coordinated operation effectively during a long term, revealing the technical feasibility of the LSGC system. The exergy analysis results indicate that the solar field has the second maximum exergy destruction and the smallest exergy efficiency, and the combustion chamber has the maximum exergy destruction. The economic analysis shows that the levelized costs of electricity and hydrogen of the LSGC system are 0.045 $/kWh and 5.67 $/kg. The environment effect evaluation shows that compared with the coal power, the LSGC system can reduce the annual emissions of CO2, NOx, SO2 and dust effectively. Those reveal relatively acceptable economic feasibility and environment protection effect of the LSGC system.

This paper presents the design and performance evaluation of a novel solar multiplate mirror concentration photovoltaic and thermal (MPVT) system using ethylene glycol/indium tin oxide liquid spectral filter (LSF). The LSF is prepared, and the test results show that its average spectral transmissivity and average spectral absorptivity are 69.2% and 30.8%. Optical characteristics and operation performance of the MPVT system are evaluated, and parametric interaction analysis is also carried out to reveal the relationships of optical and structural parameters of the MPVT system. The results indicate that the MPVT system is technically feasible and has acceptable adaptability on solar tracking error. The decrease in LSF flow channel width and increase in LSF flow channel installation height can increase the concentration ratio. The electric power and photoelectric efficiency of the photovoltaic module are 818.2 W and 29.07%. The thermal and exergy efficiencies of the MPVT system are 23.88% and 32.81%. By increasing the inlet LSF flow velocity and ambient temperature or decreasing the inlet LSF temperature properly, the thermal performance of the MPVT system can be improved. But the effects of the three parameters on the exergy efficiency of the MPVT system are all relatively small.

Poverty alleviation and environmental improvement are two important targets which most developing countries try to achieve. In order to promote the poverty alleviation by using clean energy sources, this paper develops a joint poverty alleviation project including the green energy investment company (GEIC), solar photovoltaic (PV) power plant (SPP) and wind power plant (WPP). By using a tripartite evolutionary game model, evolutionary stable strategies are evaluated. Influence estimate results of key factors show that longer annual operation time and higher on-grid electricity price will increase the participating intention of all the three participators. The government should increase the on-grid electricity price of the SPP properly, but control that of the WPP as the joint poverty alleviation project can also progress well even with relatively low on-grid electricity price of the WPP. A reasonable investment ratio of the SPP and WPP is the guarantee for the smooth development of the joint poverty alleviation project. In this study, the investment ratio of the SPP and WPP of 6:4 is relatively proper and can make the three participators all have relatively high increasing rates of participating intention simultaneously. The results will be of reference value for formulating relevant governmental policies on the poverty alleviation and clean energy development.

This study aims at proposing a public-private partnership project including the government (GOVT), coal-fired power plant (CTPP) and solar photovoltaic power plant (PVPP) toward carbon emission reduction and neutralization in China. The project is formed using the CO2 capture and utilization (CCU) and solar PV hydrogen production technologies. When all the participators cooperate, the influence of typical factors on the project is evaluated using the evolutionary game theory method. The results show that increasing the CCU subsidy can strengthen the participating intention of the CTPP but will reduce that of the GOVT. Improving the green electricity subsidy can strengthen the participating intention of the PVPP but will decrease that of the GOVT. To ensure the smooth running of the project, a relatively higher carbon emission penalty and a higher sales price of methanol should be ensured, the PVPP should control its daily working hours appropriately, and the proportion of electricity quantity of the PVPP used for hydrogen production should be increased. In this study, the suggested ranges of CCU and green electricity subsidy coefficients are 0.03–0.05 $/kWh and 0.0035–0.0045 $/kWh, the carbon emission penalty coefficient should be greater than 11 $/t, and the suggested range of daily working hours of the PVPP is 7–8 h.

An innovative solar concentrating beam splitting photovoltaic thermal (CBS-PVT) system using a half-trough concentrator (HTC) and a film spectrum filter (FSF) is proposed and studied in this study. The FSF used for this system is designed and its average reflectivity and transmissivity are 0.272 and 0.728 for the full spectrum range. Performance evaluation results of the CBS-PVT system reveal the design correctness of the system. When the N-S solar tracking error (STE) rises to 0.15°, the optical efficiency of the entire CSB-PVT system can be kept at 0.8653, showing good adaptable capacity to the STE. The operation feasibility analysis shows that the PV efficiency of the PV subsystem (PVS) is 0.314 and the overall system efficiency overall is 0.26. Parametric analysis results indicate that when the solar thermal collector tube (TCT) operating temperature rises, the total power and overall efficiency of the CSB-PVT system both rise first and then decrease. When the TCT temperature is about 225 °C, the CBS-PVT system reaches its maximum output power of 1003.6 W and the maximum overall efficiency of 0.261. When the PV cell module (PVCM) temperature increases, the total power and overall efficiency of the CBS-PVT system decrease linearly. When the PVCM temperature rises to 50 °C, the two parameters decrease to 952.9 W and 0.248.

A novel solar concentrated PV-thermal (CPV-T) system using nano-fluid spectrum filter (NSF) and with high solar concentrating uniformity is proposed in this study. The indium tin oxide/ethylene glycol (ITO/EG) nano-fluid used in the CPV-T system is experimentally prepared and tested. The results indicate that the average trans-mission and absorption rates of the NSF are 69.1% and 30.9%. The optical estimate results of the CPV-T system reveal a relatively high solar concentrating uniformity. The solar tracking deviation evaluation results show that when the north-south tracking deviation is less than 0.3 degrees, the optical efficiency of the CPV-T system can be greater than 0.834. The thermodynamic estimate results show that the maximum output power and photoelectric efficiency of the PV module are 1769.9 W and 30.3%. The thermal and exergy efficiencies of the CPV-T system are 19.4% and 16.7%. The thermal efficiency of the CPV-T system can be improved by increasing the inlet nano -fluid flow rate and environmental temperature or by decreasing the inlet nano-fluid temperature and convec-tional heat transfer coefficient (CHTC). The system exergy efficiency will be improved with the increase of the inlet nano-fluid flow rate or with the decreases of the inlet nano-fluid temperature, environmental temperature and CHTC.

This paper aims at facilitating the developments of solar photovoltaic (PV) power and wind power generations to reduce carbon emission and achieve the carbon neutralization. The main novelty of this study is developing a new partnership comprised by the green energy investment company (GEIC), solar power plant (SPP), and offshore wind power plant (OWPP) and analyzing the impacts of typical factors on the coordinated development of SPP and OWPP based on the evolutionary game theoretical method. By using a tripartite evolutionary game model, the stability analysis of equilibrium strategy is carried out. The simulation results show that stable states could be realized under different partnerships. Impact investigation results of typical influential factors on all participants indicate that longer annual operation time, higher price of electricity sold to the power grid, and larger government subsidy will lead to more incomes for the SPP and OWPP, which will strengthen the participation willingness of all participants. For this study, the on-grid price of the SPP should be greater than 0.054 /kWh. A reasonable investment ratio of the SPP and OWPP is the guarantee for the smooth development of the PPP project, which is suggested to be 4:6 in this study. The results of the current study have certain reference value for the policy and strategy formulations for facilitating the developments of solar PV power and offshore wind power generations.

In this paper, indium tin oxide (ITO) nanoparticles and four different indium tin oxide–ethylene glycol (ITOEG) nanofluid optical filters are prepared and experimentally tested. The XRD and TEM measurements of indium tin oxide nanoparticles are launched, spectral transmittances of pure ethylene glycol and four different ITOEG nanofluid materials are tested, and the beam splitting behaviours of the four different nanofluid optical filters are compared. The results show that the nanofluid consisting of 15 mg indium tin oxide and 200 ml ethylene glycol has a relatively better overall beam splitting behaviour. For the full spectrum, its average transmittance and absorbance are 69.1% and 30.9%. A novel PV/thermal system is proposed and its performances are evaluated when the ITOEG nanofluid is assumed to be utilized. The results show that the overall optical efficiency of the PV/thermal system is 93.6%. When the north–south sun-tracking error increases to 0.2°, the overall optical efficiency of the system decreases to 90.1%. That means the PV/thermal system has a relatively good adaptability to the sun-tracking error. The operation behaviour evaluation results reveal that the theoretical overall PV and solar thermal efficiencies of the PV/thermal system are 17.7% and 18.5%.

本文设计了一种具有均匀聚光效果的紧凑式线性菲涅耳太阳能光伏系统,给出了紧凑式线性菲涅耳聚光器的设计方法.对完全型紧凑式线性菲涅耳聚光光伏系统进行了光学性能分析,分析结果表明,系统具有相对较高的聚光均匀性.当其他参数一定时,随着太阳电池放置高度由小变大,系统的几何聚光比和光场利用率存在最大值.对太阳光线的跟踪精度影响进行了分析,分析结果表明,使用现有太阳能跟踪装置条件下,完全型紧凑式线性菲涅耳聚光光伏系统的总相对光学效率可保持在88.5％以上.初步的光伏组件Ⅰ-V特性测试结果表明,该聚光光伏系统的光电转换效率为15.9％.

This paper presents a numerical study on the heat transfer performance of U-shaped double-pipe heat exchanger for the concentrated solar power system. The effects of the mass flow rate, temperature and pressure of inlet super-critical CO2 are evaluated. The results show that due to the effect of centrifugal force, temperature and flow velocity distribution divergences happen in the elbow part of the double-pipe. That can enhance the heat transfer performance. With the inlet super-critical CO2 mass flow rate increased, the convection heat transfer coefficient and Nusselt number of the super-critical CO2 both increase. When the inlet super-critical CO2 mass flow rate increases to 0.6 kg s−1, the maximum local average convection heat transfer coefficient and Nusselt number of the super-critical CO2 are 7120.0 W m−2K−1 and 1892.7. By increasing the inlet super-critical CO2 temperature or pressure, the convection heat transfer coefficient of the S–CO2 can be increased. With the inlet super-critical CO2 temperature increased from 700.0 K to 780.0 K, the maximum local average convection heat transfer coefficient of super-critical CO2 increases from 5034.5 W m−2K−1 to 5149.1 W m−2K−1. Compared with the other two parameters, the effect of inlet super-critical CO2 pressure on the heat transfer performance is relatively smaller.

This study proposes a novel hybrid solar-gas power and hydrogen-production system, which is comprised by the solar tower thermal system, gas-steam turbine combined cycle and organic Rankine cycle-based hydrogen-production system. Based on the Ebsilon code, the operation processes of the hybrid system are simulated. The results show that the output power and electric efficiency of the hybrid system are 103.9 MW and 41.3%, and the daily hydrogen output is 62.2 kg. The operation simulation results of the hybrid system reveal that the gas-steam combined cycle and solar island can both achieve stable operations, and the power generation section and hydrogen-production device can both work effectively, which means the hybrid system is technically feasible. The exergy estimate results of the hybrid system show that the combustion chamber and solar receiver have the two largest exergy destructions, which are 56.5 MW and 45.3 MW. That means the performances of the two components can be further improved. For the hydrogen-production system, the exergy destructions of the proton exchange membrane electrolyzer, turbine, condenser and evaporator of the organic Rankine cycle are 0.156 MW, 0.111 MW, 2.338 MW and 1.891 MW, and the corresponding exergy efficiencies are 51.2%, 92.6%, 80.7% and 79.5%, respectively.

设计一种使用S-CO2布雷顿循环的太阳能电力淡水系统,对系统的工作原理和结构组成进行介绍,并对系统开展运行性能和?分析.结果表明,设计工况下系统的输出电功率为233.8 MW,布雷顿循环效率为37.5％,淡水日产量为3981.6 t.增大太阳辐照度有利于提高系统的电力输出和总的能量效率.定工况下的?分析结果表明,太阳塔集热器中的?损最大,为303.99 MW,对应的?效率为64.45％.海水淡化换热器的?效率最低,且其?损值也较大.随着太阳辐照度的增加,太阳塔集热器、海水淡化系统换热器和回热器内的?损均有不同幅度的增加.因此,对于该S-CO2布雷顿循环太阳能电力淡水系统的后续优化而言,应重点考虑改进这些部件的性能.