Evaluation of the optimum discharge period for closed thermal energy storages using energy and exergy analyses

Gunnewiek, Lowy; Nguyen, Suong H.; Rosen, Marc A.

doi:10.1016/0038-092x(93)90040-u

Cited by 30 publications

(18 citation statements)

References 5 publications

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“…Energy efficiency for the charging period was defined as the ratio of the heat stored in the heat storage unit to the heat transfer from the heat collection unit. Then, the total energy efficiency during the charging period Z c(total) can be formulated as (Gunnewiek et al, 1993):…”

Section: Energy and Exergy Analysismentioning

confidence: 99%

“…The rate of heat transfer ' Q Q t from the heat collection unit into the heat storage unit was calculated during the charging period by using the following equation (Gunnewiek et al, 1993):…”

Section: Energy and Exergy Analysismentioning

confidence: 99%

“…Exergy analysis is recognized by many engineers to be a powerful tool for the evaluation of the thermodynamic systems in general and of thermal energy storage systems in particular. Several authors have investigated methodologies for evaluation and comparison of thermal energy storage (TES) systems (Rosen et al, 1988(Rosen et al, , 2000Rosen, 1992Rosen, , 1999Gunnewiek et al, 1993;Dincer et al, 1997;Dincer, 1999;, and concluded that while many technically and economically successful thermal storages are in operation, no broadly valid basis for comparing the achieved performance of one storage with that of another operating under different conditions has found general acceptance. Rosen and Dincer (2003) investigated exergy methods for assessing and comparing thermal storage systems.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of energy and exergy efficiencies of an underground solar thermal storage system

Öztürk

2004

Int. J. Energy Res.

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SUMMARYIn this experimental study, solar energy was stored daily using the volcanic material with the sensible heat technique. The external heat collection unit consisted of 27 m 2 of south-facing solar air collectors mounted at a 558 tilt angle. The dimensions of the packed-bed heat storage unit were 6 Â 2 Â 0.6 m deep. The packedbed heat storage unit was built under the soil. The heat storage unit was filled with 6480 kg of volcanic material. Energy and exergy analyses were applied in order to evaluate the system efficiency. During the charging periods, the average daily rates of thermal energy and exergy stored in the heat storage unit were 1242 and 36.33 W, respectively. Since the rate of exergy depends on the temperature of the heat transfer fluid and surrounding, the rate of exergy increased as the difference between the inlet and outlet temperatures of the heat transfer fluid increased during the charging periods. It was found that the average daily net energy and exergy efficiencies in the charging periods were 39.7 and 2.03%, respectively. The average daily net energy efficiency of the heat storage system remained nearly constant during the charging periods. The maximum energy and exergy efficiencies of the heat storage system were 52.9 and 4.9%, respectively.

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Section: Energy and Exergy Analysismentioning

confidence: 99%

Section: Energy and Exergy Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of energy and exergy efficiencies of an underground solar thermal storage system

Öztürk

2004

Int. J. Energy Res.

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“…In the case of TES systems, which do not in general operate at steady state, the exergy entering is stored, or exits, or is destroyed due to irreversibilities. Exergy analysis and its implications in TES and other applications are discussed in further detail elsewhere (Bejan, 1982;Bjurstrom and Carlsson, 1985;Krane, 1987;Hahne et al, 1989;Rosen and Hooper, 1990;Rosen, 1992;Gunnewiek et al, 1993;Moran and Shapiro, 1995;Rosen and Dincer, 1997).…”

Section: Introductionmentioning

confidence: 98%

Energy and exergy analyses of cold thermal storage systems

Rosen

Pedinelli

Dinçer

1999

Int. J. Energy Res.

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“…In fact, energy analysis generally does not allow appropriate quantified measures of the benefits of stratification to be developed, while exergy analysis does. Previous studies by the authors have investigated the advantages of using exergy analysis in assessing and comparing thermal storages (Rosen et al, 1988Gunnewiek et al, 1993;Rosen, 1992), and have developed models and corresponding methods for evaluating the exergy contents of thermal storages Rosen and Hooper, 1991a, 1991b, 1992, 1994.…”

Section: Introductionmentioning

confidence: 99%

Effect of stratification on energy and exergy capacities in thermal storage systems

Rosen

Tang

Dinçer

2004

Int. J. Energy Res.

102

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SUMMARYThe increase in exergy storage capacity that is attained in thermal storages through stratification is assessed. A design-oriented temperature-distribution model for vertically stratified thermal storages that facilitates the evaluation of storage energy and exergy contents is utilized. The paper is directed towards demonstrating the thermodynamic benefits achieved through stratification, and increasing the utilization of exergy-based performance measures for stratified thermal storages. A wide range of realistic storage-fluid temperature profiles is considered, and for each the relative increase in exergy content of the stratified storage compared to the same storage when it is fully mixed is evaluated. The results indicate that, for all temperature profiles considered, the exergy storage capacity of a thermal storage increases when it is stratified, and increases as the degree of stratification, as represented through greater and sharper spatial temperature variations, increases. Furthermore, the percentage increase in exergy capacity is greatest for storages at temperatures near to the environment temperature, and decreases as the mean storage temperature diverges from the environment temperature (to either higher or lower temperatures). It is concluded that (i) the use of stratification in thermal storage designs should be considered as it increases the exergy storage capacity of a thermal storage and (ii) exergy analysis should be applied in the analysis and comparison of stratified thermal storage systems.

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Evaluation of the optimum discharge period for closed thermal energy storages using energy and exergy analyses

Cited by 30 publications

References 5 publications

Comparison of energy and exergy efficiencies of an underground solar thermal storage system

Comparison of energy and exergy efficiencies of an underground solar thermal storage system

Energy and exergy analyses of cold thermal storage systems

Effect of stratification on energy and exergy capacities in thermal storage systems

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