Elsevier

Energy Conversion and Management

Volume 121, 1 August 2016, Pages 349-357
Energy Conversion and Management

Performance of a swimming pool heating system by utilizing waste energy rejected from an ice rink with an energy storage tank

https://doi.org/10.1016/j.enconman.2016.05.049Get rights and content

Highlights

  • An analytical model of the system, and a computational program were developed.

  • Transient behavior of the water in the buried energy storage tank was simulated.

  • Effects of various system parameters on the system performance were investigated.

  • Long period performance of the system was analyzed and obtained periodic condition.

  • Optimum ice rink size is determined for a semi-Olympic size swimming pool heating.

Abstract

This study deals with determining the long period performance of a swimming pool heating system by utilizing waste heat energy that is rejected from a chiller unit of ice rink and subsequently stored in an underground thermal energy storage (TES) tank. The system consists of an ice rink, a swimming pool, a spherical underground TES tank, a chiller and a heat pump. The ice rink and the swimming pool are both enclosed and located in Gaziantep, Turkey. An analytical model was developed to obtain the performance of the system using Duhamel’s superposition and similarity transformation techniques. A computational model written in MATLAB program based on the transient heat transfer is used to obtain the annual variation of the ice rink and the swimming pool energy requirements, the water temperature in the TES tank, COP, and optimum ice rink size depending on the different ground, TES tank, chiller, and heat pump characteristics. The results obtained from the analysis indicate that 6–7 years’ operational time span is necessary to obtain the annual periodic operation condition. In addition, an ice rink with a size of 475 m2 gives the optimum performance of the system with a semi-Olympic size swimming pool (625 m2).

Introduction

One of the most important conditions for the development and industrialization of countries is energy and the ability to use it efficiently. A large part of energy such countries use is obtained from polluting sources, such as coal and fossil fuels, leading to the increase of CO2, SOx and NOx emissions. Therefore, the national energy strategies of many countries should concentrate on the utilization of environmentalist, renewable and sustainable energy sources [1], [2].

In addition, the number of sports facilities is increasing every day to promote public health, especially in developing countries. These facilities can contain several sections such as ice rinks, swimming pools, basketball courts, and volleyball courts. Widely, ice rinks and swimming pools are used for hockey, curling, figure skating, swimming races and water games. These swimming pools are commonly heated by conventional methods (e.g. coal or gas-fired boilers), and recently solar energy is also being used instead of these methods [3], [4]. A swimming pool water temperature should be between 22 °C and 28 °C for comfortable conditions [5]. In an ice rink, in order to provide a necessary hardness of the ice surface for different types of ice sports, the ice temperature should be kept between −6 °C and −1 °C by circulating a brine solution in pipes or tubes under the ice layer [6]. Excess energy from the ice rink is rejected from the condenser of a chiller unit into the environment as waste energy by using conventional air source chillers [7], [8], [9]. Furthermore, the instantaneous change in air temperature can cause irregularity of the system performance (COP) and conventional air source chillers work at low COP values when the weather temperature is high in summer. However, a ground couple chiller, which uses the buried thermal energy storage (TES) tank in the ground as a heat exchanger, can operate at more stable COP values. This is because the ground temperature does not fluctuate greatly during the whole year. It can be easily seen that underground TES tank can be a viable solution for saving the waste energy from the chiller unit.

Analytical and experimental investigations have been studied in the literature related to the design, analysis and optimization of TES for heating and cooling applications. Caliskan et al. [10] investigated energetic, exergetic, environmental and sustainability analyses of various TES systems (Latent, Thermochemical, and Sensible) for building applications at varying environment temperatures. They reported that the most sustainable system is the aquifer TES while the worst sustainable system is the latent TES. Rismanchi et al. [11] developed a computer model to determine the potential energy savings of implementing cold TES systems in Malaysia. They found that the overall energy usage of the cold TES storage strategy is almost 4% lower than the non-storage conventional system. Kizilkan and Dincer [12] presented a comprehensive thermodynamic assessment of a borehole TES system for a heating case at the University of Ontario Institute of Technology (UOIT). They performed energy and exergy analyses based on balance equations for the heating application. COPHP and overall exergy efficiency of the studied system are calculated as 2.65% and 41.35%, respectively. Zhang et al. [13] analyzed a model of a space heating and cooling system of a surface water pond that has an insulating cover, which serves as the heat source in the winter and heat sink in the summer. They considered three running modes to analyze the interaction of the seasonal heat charge and discharge for heating and refrigeration individually. Yumrutaş and Ünsal [14] analyzed an annual periodic performance of a solar assisted ground coupled heat pump space heating system, which had a hemispherical surface tank as a ground heat source based on a hybrid analytical–numerical procedure, using analytical and computational models. Yumrutaş et al. [15] presented an analytical and a computational model for a solar assisted heat pump with an underground cylindrical storage tank. Yumrutaş et al. [16] developed a computational model for determining the annual periodic performance of a cooling system utilizing a ground coupled chiller and a spherical underground TES tank.

In this study, an analytical model and a computational program written in MATLAB were developed to obtain the annual variation of ice rink and swimming pool energy requirements, a periodic solution of the transient heat transfer of the underground TES tank, system performance (COP), and the optimum size of the ice rink. The program was executed to investigate the effects of the size of the ice rink and parameters such as ground type, Carnot efficiency, and TES tank volume. Results obtained from the computational program are given as figures and discussed in the study.

Section snippets

Description of the system

The simplified system shown in Fig. 1 is located in the city of Gaziantep in Turkey, which lies between 37°4′ latitude N and 37°29′ longitude E and has a Mediterranean climate. The system under investigation consists of five main sections: an ice rink, a swimming pool, an underground TES tank, a cooling unit (Chiller) and a heating unit (Heat pump). In the system, the ice rink and the swimming pool are coupled by the chiller and the heat pump to the underground TES tank, respectively. The

Modeling of the thermal system

An analytical model was developed to determine the transient heat transfer of the underground TES tank, the cooling load of the ice rink, the heating load of the swimming pool, and the performance of the system. The analysis of each component of the system is introduced in the following subsections.

Results and discussion

The computer code written in MATLAB using the analytical model describing above was executed to investigate the effects of the size of the ice rink (375–625 m2) and parameters such as ground type (Coarse gravel, Clay, and Granite), the Carnot Efficiency (CE) factor (0.30, 0.40 and 0.50) and TES tank size (100, 200 and 300 m3) on the system. In the following section, the results obtained from the computations are presented in figures and discussed.

Annual variation of the ice rink heat gain, the

Conclusions

In this study, an analytical model was developed to analyze the long-period performance of a swimming pool heating system by utilizing waste energy rejected from an ice rink with an underground thermal energy storage tank using Duhamel’s superposition and similarity transformation technique. A computational model written in MATLAB program based on the transient heat transfer of the underground TES tank and energy requirements of the ice rink and the swimming pool was executed to investigate the

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