modeling generation systems when using ... generation systems when using solar stirling engines...
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MODELING GENERATION SYSTEMS WHEN USING SOLAR STIRLING ENGINES PARABOLIC DISHES (SOLAR/DISH)
Energy Generation, Distribution, & Transportation,
Sebastian Mendoza
Electo Eduardo Silva Lora
Vladimir Cobas
Oscar Almazan
Reinaldo Guillen
• Introduction
• Justification
• Methodology Applied
• Results
• Conclusions
SUMMARY
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INTRODUCTION
In Brazil the solar power will have more incentives in the next years
to stimulate a future development.
Dish/Stirling systems have peak efficiencies between 29% and 30%
during the conversion of sunlight into electrical energy. (Andraka,
1996)
The number of publications about for the modeling of the
Dish/Stirling system is still very low.
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Justification
Dependence on fossil fuels
Global warming climate Change
Technological developments
Power supply assured High efficiency of converting solar energy into electrical
Scientific initiative 4
METHODOLOGY
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Analytical methodology
METHODOLOGY
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METHODOLOGY
COLLECTOR GEOMETRIC MODELING
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Fig. : Geometric considerations of the collector
METHODOLOGY
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Fig: Curves of the factor of shading and geometric
configuration (Jaramillo S, 1998)
Fig: Shadow caused by the recipient. [Adapted from Siegel y Howel (1981)]
METHODOLOGY
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Fig . Thermal model collector Dish/Stirling (Wua et al, 2009)
RESULTS
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Condition of maximum possible efficiency
The optimal working temperature Solar
Stirling engine is between two case studies,
optimum temperature for maximum
efficiency and optimum temperature for
maximum power.
The analysis is done for 5 values of
irradiation (200, 400, 600, 800, 1000 W/m²)
At higher solar radiation, higher are ranges
of temperature in the receiver.
RESULTS
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Condition of maximum possible power output
To find the maximum power condition is used the
equation of Curzon-Ahlborn
The optimum absorber temperature in the condition
of maximum possible power output is slightly greater
than the case of maximum possible efficiency.
The ideal temperature in the recipient increases and
the efficiency of the engine goes down drastically with
regard to the value of maximum efficiency .
The engine for this condition has to work for short
periods time
RESULTS
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Overall Efficiencies
The actual efficiency of the Stirling engine is
calculated using equation (38), using Ks = 0.55 with
the optimal temperature of the receiver.
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CONCLUSIONS
The study was performed over a collector of 7,3 m, diameter, varying the solar radiation between
200 and 1000 W/m², based on the results obtained by the models, is also possible to report that
the Model with the use of a three sequential algorithms is pertinent to the problem under study.
The Model describes the thermal behavior, which allowed to check the influence of optimal solar
tracking and geometric design over the overall system efficiency, considering normal daily solar
radiation, wind speed, ambient temperature. Average overall efficiencies calculated and actually
obtained were 24-27%, using a technology factor Stirling Ks=0,5.
For the condition of maximum efficiency in the receiver and maximum engine power were a set of
profile curves was elaborate, for different values of the irradiation is possible to observe that for
any radiation value there is a corresponding temperature for a given optimum efficiency.
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ACKNOWLEDGEMENTS