Recent Developments in Teaching Statistical and Thermal Physics
Editorial Recent Research Progress in Solar Thermal...
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Editorial Recent Research Progress in Solar Thermal Conversion Theory and Applications Gang Pei, 1 Yuehong Su, 2 Sauro Filippeschi, 3 and Hongfei Zheng 4 1 Department of ermal Science and Energy Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China 2 Department of Architecture and Built Environment, e University of Nottingham, Nottingham NG7 2RD, UK 3 Department of Energy, System, Territory and Constructions Engineering, University of Pisa, 55126 Pisa, Italy 4 School of Mechanical and Vehicle Engineering, Beijing Institute of Technology, Beijing 100081, China Correspondence should be addressed to Gang Pei; [email protected] Received 6 July 2015; Accepted 7 July 2015 Copyright © 2015 Gang Pei et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ermal use is one of the most important ways in solar energy utilization. e global solar thermal industry is growing fast. More than 100 million square meters of solar collectors were produced worldwide in 2014. Typical applications of solar thermal technologies are water heating, space heating and cooling, refrigeration, industrial process heat, desalination, power generation, lighting, and so forth. Research and development in the scientific and technical fields of solar energy conversion are very active nowadays, and the room for improvement and innovation remains large. Works published in this special issue are contributions to solar thermal conversion. To improve heat collection efficiency of traditional all- glass evacuated tube collectors (ETC), J. Yang et al. have proposed novel ETC with an inserted tube in “A Study on ermal Performance of a Novel All-Glass Evacuated Tube Solar Collector Manifold Header with an Inserted Tube.” Water inside the collector experiences forced convection rather than natural convection. Heat transfer between water and the inner glass tube is therefore increased. e novel collector offers an efficiency increment of 5% compared with that without an inserted tube. Comprehensive utilization of solar collector is an impor- tant topic. J. Ma et al. have investigated the dual-functional solar collector (DFSC) in “Performance Investigation and Structure Optimization of a Flat Dual-Function Solar Collec- tor.” e DFSC can supply hot water or hot air depending on the consumer’s seasonal demands. A dynamic numerical model has been established to optimize the structure param- eters. According to the model, the back insulation of DFSC needs to be as thick as 6 cm to prevent heat loss via backboard; the equal depth of 3-4 cm of the upper and lower channels is optimal for both air heating and water heating modes. Solar collector can serve as not only heater but also radiative cooler. M. Hu et al. have proposed spectrally selec- tive surface for both solar heating and radiative cooling in “eoretical and Experimental Study of Spectrally Selectivity Surface for Both Solar Heating and Radiative Cooling.” e collector surface has a high spectral absorptivity in the solar radiation band and atmospheric window band (i.e., 0.2∼3 m and 8∼13 m) and low absorptivity or emissivity in other bands (i.e., 3∼8 m or above 13 m). e collector works in solar heating mode during daytime and radiative cooling mode during nighttime. It has been shown that polyethylene terephthalate is an alternative selective surface coating for the proposed solar collector design, which can achieve relative heat collection efficiency of 76.8% in comparison to a con- ventional solar collector surface and a relative temperature difference of 75.0% compared with a conventional radiative cooling surface. e overall efficiency of a solar collector gets higher when combined with PV cell. H. Chen et al. have studied a heat pipe photovoltaic/thermal solar collector in “Numerical and Experimental Study on Energy Performance of Photovoltaic- Heat Pipe Solar Collector in Northern China.” e collectors of this kind are applicable in cold regions without the problem of freezing. A simplified one-dimensional steady state model has been developed to study the electrical and thermal performance of the collector. A testing rig has been built to verify the model. Hindawi Publishing Corporation International Journal of Photoenergy Volume 2015, Article ID 850413, 2 pages http://dx.doi.org/10.1155/2015/850413
Transcript of Editorial Recent Research Progress in Solar Thermal...
EditorialRecent Research Progress in Solar Thermal ConversionTheory and Applications
Gang Pei,1 Yuehong Su,2 Sauro Filippeschi,3 and Hongfei Zheng4
1Department ofThermal Science and Energy Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China2Department of Architecture and Built Environment, The University of Nottingham, Nottingham NG7 2RD, UK3Department of Energy, System, Territory and Constructions Engineering, University of Pisa, 55126 Pisa, Italy4School of Mechanical and Vehicle Engineering, Beijing Institute of Technology, Beijing 100081, China
Correspondence should be addressed to Gang Pei; [email protected]
Received 6 July 2015; Accepted 7 July 2015
Copyright © 2015 Gang Pei et al.This is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Thermal use is one of themost important ways in solar energyutilization. The global solar thermal industry is growing fast.More than 100 million square meters of solar collectors wereproduced worldwide in 2014. Typical applications of solarthermal technologies are water heating, space heating andcooling, refrigeration, industrial process heat, desalination,power generation, lighting, and so forth. Research anddevelopment in the scientific and technical fields of solarenergy conversion are very active nowadays, and the roomfor improvement and innovation remains large.
Works published in this special issue are contributions tosolar thermal conversion.
To improve heat collection efficiency of traditional all-glass evacuated tube collectors (ETC), J. Yang et al. haveproposed novel ETC with an inserted tube in “A Study onThermal Performance of a Novel All-Glass Evacuated TubeSolar Collector Manifold Header with an Inserted Tube.”Water inside the collector experiences forced convectionrather than natural convection. Heat transfer between waterand the inner glass tube is therefore increased. The novelcollector offers an efficiency increment of 5% compared withthat without an inserted tube.
Comprehensive utilization of solar collector is an impor-tant topic. J. Ma et al. have investigated the dual-functionalsolar collector (DFSC) in “Performance Investigation andStructure Optimization of a Flat Dual-Function Solar Collec-tor.” The DFSC can supply hot water or hot air dependingon the consumer’s seasonal demands. A dynamic numericalmodel has been established to optimize the structure param-eters. According to the model, the back insulation of DFSC
needs to be as thick as 6 cm to prevent heat loss via backboard;the equal depth of 3-4 cm of the upper and lower channels isoptimal for both air heating and water heating modes.
Solar collector can serve as not only heater but alsoradiative cooler. M. Hu et al. have proposed spectrally selec-tive surface for both solar heating and radiative cooling in“Theoretical and Experimental Study of Spectrally SelectivitySurface for Both Solar Heating and Radiative Cooling.” Thecollector surface has a high spectral absorptivity in the solarradiation band and atmospheric window band (i.e., 0.2∼3 𝜇mand 8∼13 𝜇m) and low absorptivity or emissivity in otherbands (i.e., 3∼8𝜇m or above 13 𝜇m). The collector works insolar heating mode during daytime and radiative coolingmode during nighttime. It has been shown that polyethyleneterephthalate is an alternative selective surface coating for theproposed solar collector design, which can achieve relativeheat collection efficiency of 76.8% in comparison to a con-ventional solar collector surface and a relative temperaturedifference of 75.0% compared with a conventional radiativecooling surface.
The overall efficiency of a solar collector gets higher whencombined with PV cell. H. Chen et al. have studied a heatpipe photovoltaic/thermal solar collector in “Numerical andExperimental Study on Energy Performance of Photovoltaic-Heat Pipe Solar Collector in Northern China.”The collectorsof this kind are applicable in cold regionswithout the problemof freezing. A simplified one-dimensional steady state modelhas been developed to study the electrical and thermalperformance of the collector. A testing rig has been built toverify the model.
Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2015, Article ID 850413, 2 pageshttp://dx.doi.org/10.1155/2015/850413
2 International Journal of Photoenergy
Medium temperature solar collector is also attractinggreat interest. H. Zheng et al. have investigated a shell-encap-sulated solar collector which can be used in north area ofChina for wall-mounted installation in “Design and Testingof a Shell-Encapsulated Solar Collector with the CompoundSurface Concentrators.” The collector is based on the combi-nation of a novel compound curved surface concentrator andan aluminum concentric solar receiver, which is containedin a glass evacuated tube. It has daily average efficiencyabout 45∼50% under the conditions of hot water temperatureabove 80∘C and ambient temperature below 0∘C. A newtrough solar concentrator which is composed of multiplereflective surfaces has also been developed in “Study on aMidtemperature Trough Solar Collector with MultisurfaceConcentration.” A main CPC concentrator and a secondaryparabolic reflector with two straight edges and a bottomare used as the reflectors. The collector offers conveniencefor installation and thermal insulation of the receiver andreduces the demand for solar tracking precision. Instan-taneous efficiency more than 45% can be achieved at theoperation temperature higher than 145∘C.
Solar thermal power generation has great potential toreduce the consumption of fossil fuel. R. Zhai et al. havestudied solar assisted coal-fired power generation system(SACFPGS) in “Improved Optimization Study of Integra-tion Strategies in Solar Aided Coal-Fired Power GenerationSystem.” The SACFPGS has advantages over solar thermalpower generation system regarding the elimination of steamturbine and generator. It also has less coal consumption thantraditional coal-fired system. The genetic algorithm is usedto optimize the solar collector field area and thermal storagecapacity. It shows that the improvement of the thermal stor-age system effectively leads to more cost-effective SACFPGS.
Solar lighting is also capable of reducing energy con-sumption and environmental pollution. X. Qin et al. haveestimated the energy saving and environmental impact ofsolar lighting technologies in “Solar Lighting Technologiesfor Highway Green Rest Areas in China: Energy Saving,Economic, and Environmental Evaluation.” A case study onsolar lighting for a highway rest area of 904m2 is presented.It is shown that natural light guiding system can bringabout energy saving of 29696.4 kWh during day time. Whileusing solar photovoltaic LED lamp, the energy saving is219000 kWh. The total annual energy saving by the solarlighting technology including solar photovoltaic LED lightingand natural light guiding systems can reduce 99.5 tons ofequivalent standard coal.
Acknowledgments
At the end, we would like to thank all the authors and review-ers for the contribution to this issue.
Gang PeiYuehong Su
Sauro FilippeschiHongfei Zheng
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