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| 2. |
- Fischer, S, et al.
(författare)
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Collector test method under quasi dynamic conditions according to the European Standard EN 12975-2
- 2004
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X. ; 76, s. 117-123
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Konferensbidrag (refereegranskat)abstract
- In April 2001 the new European Standard EN 12975:2000: ''Thermal solar systems and components--Solar Collectors'' was established. With the publication of this European standard all national standards, related to the same topic, have to be withdrawn by the nations of the European Community. Now only one standard for testing solar collectors is valid throughout Europe.This European Standard specifies test methods for validating the durability, reliability and safety requirements for liquid heating collectors. The standard also includes two alternative test methods for the thermal performance characterization for liquid heating collectors. Apart from the well-known test method under steady-state conditions according to ISO 9806-1, ISO 9806-3 and ASHRAE 93-77 the EN 12975 permits a quasi-dynamic test method for the thermal performance characterization of solar thermal collectors.This paper presents the improved approach to outdoor performance testing of solar thermal collectors under quasi-dynamic test conditions. The test requirements and collector theory are closely connected to those long agreed on for steady-state testing, as described in the ISO and ASHRAE standards mentioned above. The most important effects for the all day performance of the collector are taken into account. The test method covers most collector designs on the market today (except ICS type). Only some correction terms are added to the basic collector models of the present steady-state test methods. Still this limited change will allow test data to be collected and used from whole days.An important fact is that the collector model used for the parameter identification is written so that the error in collector output power is minimized. Therefore an accurate long-term prediction of the collector performance can be an integral part of the test method, where the same collector model and parameters are used for both testing and prediction.
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| 3. |
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| 4. |
- Adsten, Monika, et al.
(författare)
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The influence of climate and location on collector performance
- 2002
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Ingår i: Renewable energy. - 0960-1481 .- 1879-0682. ; 25:4, s. 499-509
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Tidskriftsartikel (refereegranskat)abstract
- The influence of annual climate variations on the performance of solar thermal collectors in the northern part of Europe has been investigated. The annual solar collector energy output has been calculated with the MINSUN simulation program using hourly, measured climatic data for the years 1983–98 for three cities situated in the south (Lund), central (Stockholm) and north (Luleå) of Sweden. A synthetic year created with the Meteonorm weather simulation program was also used in the simulations. Two solar thermal collectors were modelled: a flat plate solar collector and a tubular vacuum collector, both of commercial standard.The thermal energy output is strongly correlated to the annual global irradiation at a horizontal surface. The annual average energy delivered from the flat plate collector was 337 kWh/m2 for Stockholm (337 for Lund and 298 for Luleå), and from the vacuum tube collector 668 kWh/m2 for Stockholm (675 for Lund and 631 for Luleå) at an operating temperature of T=50°C. Maximum deviations from the average value for this 16-year period are around 20% for the flat plate and 15% for the vacuum tube collector, at T=50°C.The relation between global irradiation on a horizontal surface and the annually collected thermal energy at a constant operating temperature could be fitted to a linear equation: qu=aG(0°)+bT, where qu is the energy output from the collector, G(0°) the global irradiation at a horizontal surface, T the average temperature of the collector fluid, and a and b fitting parameters in a double linear regression analysis.
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| 5. |
- Ahlgren, Benjamin, et al.
(författare)
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A simplified model for linear correlation between annual yield and DNI for parabolic trough collectors
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 174, s. 295-308
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a simple method for estimating annual thermal performance of parabolic trough collectors (PTCs) based on a linear relation with annual DNI for a certain latitude. A case study with simulations for a novel concentrating solar collector in 316 locations for three operating temperature scenarios worldwide was carried out and showed promising results for the latitudes and continents investigated. For a certain latitude and mean operating temperature, the annual yield of a PTC was found to be linearly proportional to yearly DNI. The proposed method will serve as a simplified alternative to the steady-state and quasi-dynamic methods already used. Estimating performance based on yearly DNI can be used by design engineers to do quick preliminary planning of solar plants. Customers can also use this method to evaluate existing solar collector installations. A TRNSYS/TRNSED tool that uses a steady-state model has been developed to carry out the simulations and it has been validated against a PTC array at Technical University of Denmark (DTU). The results show that the simplified method can give reliable estimates of long-term performance of parabolic trough collectors.
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| 6. |
- Bales, Chris, et al.
(författare)
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Dimensioning of Solar Combisystems
- 2003
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Ingår i: Solar heating systems for houses. - London : James & James. - 1902916468
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Bernardo, Ricardo, et al.
(författare)
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Evaluation of a Parabolic Concentrating PVT System
- 2008
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Ingår i: Proceedings of the 7th EUROSUN Conference. - 9781617822285
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was testing and performance simulation of an innovative tracking hybrid solar system being developed by the Swedish Company Arontis. The Solar8 collector produces both electrical and thermal energy in one system. Its performance was compared with conventional photovoltaic panels and solar thermal collectors working side-by-side which are already on the market. The solar8 sample tested in Lund is a prototype designed for small demonstration projects and further development is ongoing. The evaluation shows that the thermal collector has an overall heat loss coefficient of 3.1 W/(m2.ºC), an optical efficiency of 65% and an electrical efficiency at 25ºC of 8% per active glazed area. If we account the total glazed area instead, the thermal collector has an overall heat loss coefficient of 2.5 W/(m2.ºC), an optical efficiency of 52% and an electric efficiency at 25ºC of 6%. The electric efficiency of the bare cells is 16%. Annual performance simulations were carried out for the Swedish (Stockholm), Portuguese (Lisbon) and Zambian (Lusaka) climate. From the simulations one can conclude that: Solar8 can be replaced by a traditional PV-thermal collector side-by-side system using less space and producing the same electric and thermal outputs; tracking around one axis placed in North-South direction is considerably better then tracking around an axis set on East-West direction; the global irradiation on a static surface is always higher when compared with the beam irradiation towards a tracking concentrating surface; the ratio between electric and thermal output decreases when Solar8 is moved to the equator.
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| 8. |
- Bernardo, Ricardo, et al.
(författare)
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Performance evaluation of low concentrating photovoltaic/thermal systems: A case study from Sweden
- 2011
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X. ; 85:7, s. 1499-1510
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Tidskriftsartikel (refereegranskat)abstract
- Some of the main bottlenecks for the development and commercialization of photovoltaic/thermal hybrids are the lack of an internationally recognized standard testing procedure as well as a method to compare different hybrids with each other and with conventional alternatives. A complete methodology to characterize, simulate and evaluate concentrating photovoltaic/thermal hybrids has been proposed and exemplified in a particular case study. By using the suggested testing method, the hybrid parameters were experimentally determined. These were used in a validated simulation model that estimates the hybrid outputs in different geographic locations. Furthermore, the method includes a comparison of the hybrid performance with conventional collectors and photovoltaic modules working side-by-side. The measurements show that the hybrid electrical efficiency is 6.4% while the optical efficiency is 0.45 and the U-value 1.9 W/m(2) degrees C. These values are poor when compared with the parameters of standard PV modules and flat plate collectors. Also, the beam irradiation incident on a north south axis tracking surface is 20-40% lower than the global irradiation incident on a fixed surface at optimal tilt. There is margin of improvement for the studied hybrid but this combination makes it difficult for concentrating hybrids to compete with conventional PV modules and flat plate collectors. (C) 2011 Elsevier Ltd. All rights reserved.
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| 9. |
- Campana, Pietro Elia, 1984-
(författare)
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PV water pumping systems for grassland and farmland conservation
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Grassland degradation is considered as one of the worst environmental and economic problems in China because of the negative impacts on water and food security. The application of the photovoltaic water pumping (PVWP) technology for irrigation is an innovative and sustainable solution to curb the progress of grassland desertification and to promote the conservation of farmland in remote areas. The combination of PVWP with water saving irrigation techniques and the sustainable management of the water resources enhances the grass productivity enabling to halt wind and rainfall erosion and to provide higher incomes and better living conditions for farmers. PVWP systems have been used for more than 40 years especially for drinking purposes, livestock watering and irrigation in small-medium size applications. Nevertheless, several knowledge gaps still exist and system failures still occur, which are mainly bounded to the system design procedure and optimization. The technical and economic feasibilities related to the system implementation, especially effectiveness and profitability, need to be addressed. Moreover, irrigation in remote areas constrained by availability of water resources has to be investigated for a better understanding of PVWP system integration with the environment and for optimization purposes. This thesis is to bridge the current knowledge gaps, optimize system implementation and prevent system failures Validation of the models adopted and optimization of the system on the basis of solar energy resources and exploitable groundwater has been performed for a pilot PVWP system in Inner Mongolia. The match between the water supplied through the pumping system and the grass water demand has been studied, and the effects of pumping on the available resources and the crop productivity have been evaluated. The economic analyses have also been conducted in order to establish the most cost effective solution to provide water for irrigation and to evaluate the project profitability. In addition, the CO2 emission reductions by using PV technology have been assessed as well. It was found that the proper designed PVWP system represents the best technical and economic solution to provide water for irrigation in the remote areas compared to other water pumping technologies, such as diesel water pumping and wind power water pumping due to the high positive net present values and short payback periods.
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| 10. |
- Davidsson, Henrik, et al.
(författare)
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Performance of a multifunctional PV/T hybrid solar window
- 2010
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X. ; 84:3, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- A building-integrated multifunctional PV/T solar window has been developed and evaluated. It is constructed of PV cells laminated on solar absorbers placed in a window behind the glazing. To reduce the cost of the solar electricity, tiltable reflectors have been introduced in the construction to focus radiation onto the solar cells. The reflectors render the possibility of controlling the amount of radiation transmitted into the building. The insulated reflectors also reduce the thermal losses through the window. A model for simulation of the electric and hot water production was developed. The model can perform yearly energy simulations where different features such as shading of the cells or effects of the glazing can be included or excluded. The simulation can be run with the reflectors in an active, up right, position or in a passive, horizontal, position. The simulation program was calibrated against measurements on a prototype solar window placed in Lund in the south of Sweden and against a solar window built into a single family house, Solgården, in Älvkarleö in the central part of Sweden. The results from the simulation shows that the solar window annually produces about 35% more electric energy per unit cell area compared to a vertical flat PV module.
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