• Title/Summary/Keyword: thermal storage

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Characteristics Analysis of Seasonal Cold Thermal Storage for Cooling Energy (냉방에너지용 계간축열조의 특성 해석)

  • Kim, Myung-Rae;Lee, Ju-Hee;Yoon, JaeOck
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.32 no.11
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    • pp.55-64
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    • 2016
  • In Korean, the seawater temperature of the Mid-West area in February is less than $3^{\circ}C$ on average, staying unchanged more than 8 days. The seawater cold thermal resource is worthwhile to be used as the stored energy of seasonal thermal energy storage for cooling and heating energy. Regarding hot water thermal energy storage, the countries in Northern Europe commercialize and develop central solar heating plants with seasonal thermal storage. Nevertheless, there is no case of research on seasonal storage and experiment of the heat source for large heating and cooling. Therefore, the purpose of this study is to analyze the temperature characteristics and discharge characteristics of seasonal thermal storage when seawater cold thermal resource is stored into seasonal thermal storage In Korean environmental conditions, and suggest the practical performance and validity of seasonal thermal storage system. A volume of seasonal thermal storage was set to $2,500m^3$. As a thermal storage medium, water that features easy purchase and treatment and has large thermal capacity was used. The initial storage temperature of the medium in seasonal thermal storage was $5^{\circ}C$, and its storage period was 130 days. Seasonal thermal storage was buried in the earth, and the earth temperature up to 5m of earth was the earth temperature value observed by Korea Meteorological Administration. For the earth temperature of the more depth, the predicted value calculated by prediction formula was used. The temperature characteristics were analyzed by TRNSYS simulation. The discharge characteristics in the thermal storage were analyzed by CFD simulation. The calculated analysis values and characteristics were analyzed. The 100-days temperature maintenance performance of seasonal thermal storage was found to be 93%, which has almost the same as a German commercial system. Regarding to discharge characteristics of seasonal thermal storage, after stopping in discharge mode, it had immediately stable turbulent motion which was found by CFD analysis. Therefore, it is judged that the seasonal thermal storage for cooling energy is applicable to local cooling or building cooling system.

An Analysis of the Optimal Thermal Storage Time of Air-Conditioning System with Slab Thermal Storage : An Analysis by the Gradient Method Algorithm (슬래브축열의 최적축열시간 산정 : 구배법 알고리즘에 의한 해석)

  • Jung, Jae-Hoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.10
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    • pp.702-709
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    • 2008
  • In this paper, the optimal thermal storage time of an air-conditioning system with slab thermal storage in office building was analyzed on the basis of the gradient method algorithm. The sum of room temperature deviation and heat extraction rate was set to the criterion function. It was calculated that four hours is the optimal thermal storage time under the standard evaluation criterion. Furthermore, some case studies were executed by controlling ratio of weight functions of room temperature deviation and heat extraction rate in criterion function. It is possible to design many kinds of optimal operation of an air-conditioning system with slab thermal storage by controlling ratio of the weight functions in criterion function.

Development of Thermal Storage System in Plastic Greenhouse(II) -Thermal performance of solar greenhouse system for hydroponic culture- (플라스틱 온실(溫室)의 열저장(熱貯藏) 시스템의 개발(開發)에 관(關)한 연구(硏究)(II) -수경재배용(水耕栽培用) 태양열(太陽熱) 온실(溫室) 시스템의 열적(熱的) 성능(性能)-)

  • Kim, Y.H.;Koh, H.K.;Kim, M.K.
    • Journal of Biosystems Engineering
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    • v.15 no.2
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    • pp.123-133
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    • 1990
  • Thermal performance of a solar heating plastic greenhouse designed for a hydroponic system was studied. The system was constructed with the air-water heat exchanger and thermal storage tank that were combined with hydroponic water beds. Experiments were carried out to investigate the daily average heat stored and released in thermal storage tank, average solar energy collection efficiency, average coefficient of performance, average oil reduction factor of thermal storage system, and the heat transfer coefficient during the nighttime in plastic greenhouse. The results obtained in the present study are summarized as follows. 1. Daily average heat stored in thermal storage tank and released from the thermal storage tank was 1,259 and $797KJ/m^2$ day, respectively. 2. The average solar energy collection efficiency of thermal storage tank was 0.125 during the experiment period. And the average coefficient of performance of thermal storage system in plastic greenhouse was 3.6. 3. The average oil reduction factor of thermal storage system and the heat transfer coefficient during the nighttime in plastic greenhouse were found to be 0.52 and $4.3W/m^2\;hr\;^{\circ}C$, respectively.

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Consideration of Appropriate Thermal Storage Time of Air-Conditioning System with Slab Thermal Storage in an Office Building by Use of Measurement Value (실측치를 통한 사무소건물 슬래브축열 공조시스템의 적정 축열시간 검토)

  • Jung, Jae-Hoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.10
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    • pp.719-726
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    • 2010
  • In this paper, the appropriate thermal storage time of an air-conditioning system with slab thermal storage was considered by use of summer measurement values. Two standards of heat extraction rate and criterion function were established as the standard that evaluates appropriateness. When heat extraction rate was a standard, zero hour and seven hours were obtained as appropriate thermal storage time, in the case of evaluation by energy consumption and running cost individually. Also, when criterion function was a standard, the difference between energy consumption and running cost was small, it was because the weight function to room air temperature deviation was much bigger than heat extraction rate.

An Experimental Study on Thermal Storage Performance of an Air Conditioning System with Slab Thermal Storage (슬래브축열 공조시스템의 축열성능에 관한 실험적 연구)

  • Jung Jae-Hoon;Shin Young-Gy
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.5
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    • pp.427-435
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    • 2005
  • This paper investigates the thermal storage performance of the office building which has adopted an air conditioning system with its slab structure as a regenerator. Four cases of the thermal storage performance experiment were conducted. Room air temperatures, floor slab temperatures, temperatures around the air conditioning unit were logged and analyzed. The load handling capacity of the air conditioning unit and the amount of heat stored in the slab were decided from those experiments. Several efficiencies were investigated to evaluate the performance of the thermal storage. The results concluded that the slab as a regenerator is very effective in cutting down peak loads of the office building.

In-Situ Measurement of Chiller Performance and Thermal Storage Density of an Ice Thermal Storage System (빙축열 시스템 냉동기 성능 및 축열밀도 현장측정 기법연구)

  • Shin Younggy;Yang Hooncheul;Tae Choon-Seob;Cho Soo;Kim Youngil
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.12
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    • pp.1204-1209
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    • 2005
  • In-situ measurement was made to evaluate chiller performance and thermal storage density of an ice thermal storage system. The system belonged to a big hotel and the measurement was conducted during late October. Owing to very small cooling load, the data logging was possible for a single thermal storage cycle. However, operation history of the chiller showed a relatively good spectrum of data for performance evaluation. COP and thermal storage density were calculated. The COP at full load was about 4.07, which was lower than $4.8\~6.4$ of new chillers. The measured storage density was about $10.9RT-h/m^3\;(=152MJ/m^3)$, which also was lower than a criterion of normal performance $(above\;13.0RT-h/m^3\;or\;181MJ/m^3)$. The study result provides technical basis for quantitative ESCO business scenario.

Performance Simulation and Analysis of the Solar Thermal Storage System Using Heat Pipe (히트파이프를 사용한 태양열 축열시스템의 성능모사 및 해석)

  • Jung, Eui-Guk;Boo, Joon-Hong;Kim, Jong-Kyu;Kang, Yong-Heack
    • 한국태양에너지학회:학술대회논문집
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    • pp.80-85
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    • 2009
  • Mathematical modeling and performance simulation results were shown for the solar thermal storage system which used heat pipe. The thermal storage system was composed of thermal storage tank and charging/discharging heat exchanger with one by the heat pipes. Heat pipe heat exchanger was attached to system, and could carry out charging and discharging to thermal storage tank at the same time. Height of the thermal storage tank was 600 mm, and that of the charging/discharging heat exchanger was 400 mm. Length of the heat pipe was the same as the total height of thermal storage system, and outer and inner diameter were 25.4 mm(O.D.) and 21.4 mm(I.D.) respectively. Diameter of the circular was 43 mm(O.D.), and fin geometries were considered as the design parameters. High temperature phase change material(PCM), $KNO_3$ and low temperature PCM, $LINO_3$ were charged to storage tank to adjust working temperature. Total size of thermal storage system able to get heat capacity more than 500 kW was calculated and the results were shown in this study. Number of heat pipe was required more than maximum 500, and total length of thermal storage system was calculated to the more than maximum 3 m at various condition.

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Dynamic Analysis of Cool Thermal Storage Air Conditioning System (빙축열 에어컨의 동적 사이클 해석)

  • Koh, Jae-Yoon;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.28 no.1
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    • pp.65-74
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    • 2008
  • In this study, dynamic characteristics analysis of AC system is investigated using a cool thermal storage system. A analysing program for cool thermal storage AC system is developed. The performances are studied by several variables and dynamic characteristics. Comparing the result at conventional operation condition with that at the condition using ice storage system, this study showed the effects of the sub cooled degree, superheated degree, efficiency of compressor and evaporating temperature. At the condition using thermal storage system, the thermal storage process was operated during midnight being not needed the cooling of the AC unit through the continuous running of the condenser. The refrigerant was sub-cooled using stored energy after being discharged from the air source condenser during the daytime. The COP was increased owing to the sub-cooling of refrigerant during daytime, thus the power consumption was effectively decreased.

A Performance Analysis on a Chiller with Latent Thermal Storage According to Various Control Methods (잠열 축열식 칠러시스템의 제어 방식에 따른 성능 분석)

  • Kang, Byung Ha;Kim, Dong Jun;Lee, Choong Seop;Chang, Young Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.29 no.11
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    • pp.592-604
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    • 2017
  • A chiller, having a thermal storage system, can contribute to load-leveling and can reduce the cost of electricity by using electricity at night. In this study, the control experiments and simulations are conducted using both conventional and advanced methods for the building cooling system. Advanced approaches, such as the "region control method", divide the control region into five zones according to the size of the building load, and determines the cooling capacities of the chiller and thermal storage. On the other hand, the "dynamic programming method" obtains the optimal cooling capacities of the chiller and thermal storage by selecting the minimum-cost path by carrying out repetitive calculations. The "thermal storage priority method" shows an inferior chiller performance owing to the low-part load operation, whereas the chiller priority method leads to a high electric cost owing to the low utilization of thermal storage and electricity at night. It has been proven that the advanced control methods have advantages over the conventional methods in terms of electricity consumption, as well as cost-effectiveness. According to the simulation results during the winter season, the electric cost when using the dynamic programming method was 6.5% and 8.9% lower than that of the chiller priority and the thermal storage priority methods, respectively. It is therefore concluded that the cost of electricity utilizing the region control method is comparable to that of the dynamic programming method.

Experimental Study on the Thermal Storage Efficiency Through Variable Porous Mainfolds in a Test Storage Tank (실험 저장조내의 유입구 형상변화에 따른 열 저장효율에 관한 실험적 연구)

  • Pak, Ee-Tong;Hwang, Sung-Il;Choi, Young-Il
    • Solar Energy
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    • v.9 no.3
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    • pp.37-43
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    • 1989
  • This paper dealt with thermal storage efficiency due to difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank [$0.5m{\times}0.5m{\times}1.0m$] and the temperature of water flowing into the tank, flow rate of water flowing into the tank and shape of porous manifold which water flow into the tank through. As results of experiments; (1) When the flow rate was constant and the diameter of porous section decreased by 8mm, 6mm, and 4mm, the thermal storage efficiency increased. (2) When the diameter of porous section was constant and the difference ($T_{\infty}-Ti$) between the mean temperature of water in the storage tank and the temperature of water flowing into the tank increased by -30, -20, -10, 5, 10, 15 ($^{\circ}C$), the thermal storage efficiency increased. (3) When the($T_{\infty}-Ti$) was constant and the flow rate decreased by 0.8, 0.4, 0.25(LPM), the thermal storage efficiency increased. (4) When the shape of porous section was rigid, the thermal storage efficiency was the most effective, and with establishing flexible porous section or mesh, the effective thermal storage efficiency was obtained.

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