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