Thermal Storage Air-conditioning System Research Articles

Examination of Operational Methods for a Low-Temperature Aquifer Thermal Storage Air Conditioning System Based on Operational Performance and Considerations of Thermal Storage and Pumping Volume Balance

Aquifer Thermal Energy Storage (ATES) systems are garnering attention as high-efficiency air conditioning technologies that contribute to the realization of a carbon-neutral society. This study focuses on an ATES system constructed in Japan, characterized by its complex geological conditions and thin aquifer layers. Detailed actual performance data measured over four years are presented, and performance analysis results show that a COP of 5 was achieved for the overall building cooling and heating system. In addition, the study provides a detailed analysis of the imbalance in heat quantity, remaining heat storage, and other factors based on actual data, identifying operational issues and summarizing specific improvement measures. Finally, as a proposal for a sustainable operational method to balance the cumulative heat storage and pumping volume of cold and hot water, specific operational procedures are summarized, including setting the return water temperature for the next season based on the dimensionless average pumping temperature of the previous season, and a flowchart is presented. There is no prior research that shows such specific operational procedures, and this can be considered an important achievement of this study.

Reinforcement learning of room temperature set-point of thermal storage air-conditioning system with demand response

Demand response (DR) is an effective means to reduce peak loads and enhance grid stability. Heating, ventilation, and air-conditioning (HVAC) systems have potential energy transfer characteristics and can be used as a typical flexible load for building DR. The HVAC thermostat settings are the key parameters that directly affect the elasticity of building DR and reflect the willingness of users to participate in DR. For air-conditioning DR control, the conventional method to determine thermostat settings is model-dependent, while reinforcement learning (RL) is a model-free, adaptive continuous control algorithm. Taking the proximal policy optimization RL algorithms, a neural network is used to construct a strategic framework to obtain discrete control actions, that is, thermostat settings, and a new objective function truncation method is adopted to limit the update step size and enhance the robustness of the algorithm. Thus, a TRNSYS and MATLAB joint simulation platform for the thermal storage air-conditioning system was built. This study formulated a DR strategy based on time-of-use electricity prices, which considers factors, such as environment, thermal comfort, and energy consumption; and the proposed RL algorithm is used to learn the thermostat settings in DR time. The results show that the proposed RL algorithm could realize the temperature set-point control, which saved 9.17% of the operating cost compared with a non-thermal storage air-conditioning system with a constant set-point.

Receding‐horizon based optimal dispatch of virtual power plant considering stochastic dynamic of photovoltaic generation

AbstractThe merits of a virtual power plant in integrating photovoltaic generation and flexible loads, such as a chilled water thermal storage air conditioning system and an electric vehicle, are well recognized. However, the optimal operation of a virtual power plant is challenged by the complexities of solar irradiance and the large size of a chilled water thermal storage air conditioning system and an electric vehicle. This paper proposes a new approach to the optimal dispatch problem of a virtual power plant. The stochastic dynamic of solar irradiance is modelled by a stochastic differential equation set. The binary decision for a chilled water thermal storage air conditioning system and an electric vehicle are characterized by a mixed logical dynamical model. The resulting optimal dispatch problem is solved by the receding horizon approach. The appeal of the proposed approach is in its capability to consider the stochastically dynamical impact of solar irradiance. Besides, the proposed approach can solve the optimization problem over a relatively small period of time, and thus has the potential for online applications. Finally, the feasibility and effectiveness of the proposed approach is demonstrated by numerical simulations.

Optimal Dispatch of a Virtual Power Plant Considering Demand Response and Carbon Trading

The implementation of demand response (DR) could contribute to significant economic benefits meanwhile simultaneously enhancing the security of the concerned power system. A well-designed carbon emission trading mechanism provides an efficient way to achieve emission reduction targets. Given this background, a virtual power plant (VPP) including demand response resources, gas turbines, wind power and photovoltaics with participation in carbon emission trading is examined in this work, and an optimal dispatching model of the VPP presented. First, the carbon emission trading mechanism is briefly described, and the framework of optimal dispatching in the VPP discussed. Then, probabilistic models are utilized to address the uncertainties in the predicted generation outputs of wind power and photovoltaics. Demand side management (DSM) is next implemented by modeling flexible loads such as the chilled water thermal storage air conditioning systems (CSACSs) and electric vehicles (EVs). On this basis, a mixed integer linear programming (MILP) model for the optimal dispatching problem in the VPP is established, with an objective of maximizing the total profit of the VPP considering the costs of power generation and carbon emission trading as well as charging/discharging of EVs. Finally, the developed dispatching model is solved by the commercial CPLEX solver based on the YALMIP/MATLAB (version 8.4) toolbox, and sample examples are served for demonstrating the essential features of the proposed method.

Experimental investigation of solar photovoltaic operated ice thermal storage air-conditioning system

Under the double pressure of energy shortage and environmental pollution, ice thermal storage air-conditioning and photovoltaic air-conditioning has been applied in refrigeration field. In order to improve application scope and reduce investment operation cost, the ice thermal storage adopted to store solar energy in ice thermal storage air-conditioning driven by distributed photovoltaic energy system was proposed in this paper. Two operation models had been tested by experiment. Research results revealed all of the solar energy accepted by PV array had been stored with ice or cold water. Moreover, the experimental results analysis showed that it is feasible to use ice thermal storage instead of battery bank to store solar energy in the field of distributed photovoltaic refrigeration. In operation mode 1, the average system energy utilization efficiency was 0.525 and the average refrigeration efficiencies η¯rand η¯rs were 0.7292 and 0.0690, respectively. When system operated in mode 2, the average system energy utilization efficiency was 0.3377 and the refrigerator performances parameters η¯rand η¯rs were 4.49 and 0.3875, which were 6.16 times and 5.62 times of the average η¯r and η¯rs under working model 1.

大学施設のトータルビルコミッショニングの実践研究 (第8報)空調負荷予測を用いた蓄熱式空調システムの制御の効果の予備検討

大学施設のトータルビルコミッショニングの実践研究 (第8報)空調負荷予測を用いた蓄熱式空調システムの制御の効果の予備検討

建物群における水蓄熱空調システムの運用最適化手法に関する研究 （第3報）設定値変更前後の実測値の比較と設定値検討ツールの開発

建物群における水蓄熱空調システムの運用最適化手法に関する研究 （第3報）設定値変更前後の実測値の比較と設定値検討ツールの開発

放冷冷水の冷却水化による蓄熱式空調システムの昼間電力消費削減に関する研究 : 第1報-基本システムの提案と基本性能

放冷冷水の冷却水化による蓄熱式空調システムの昼間電力消費削減に関する研究 : 第1報-基本システムの提案と基本性能

放冷冷水の冷却水化による蓄熱式空調システムの昼間電力消費削減に関する研究(第3報)空冷冷凍機システムへの適用

放冷冷水の冷却水化による蓄熱式空調システムの昼間電力消費削減に関する研究(第3報)空冷冷凍機システムへの適用

D-45 地中熱源ヒートポンプを有した蓄熱式空調システムの運転実績調査 : (第2報)地中熱源ヒートポンプの運転状況の把握

D-45 地中熱源ヒートポンプを有した蓄熱式空調システムの運転実績調査 : (第2報)地中熱源ヒートポンプの運転状況の把握

Reduction of Electric Power Consumption for Thermal Storage Air Conditioning System in Daytime by Application of Discharged Cold Water to Cooling Water : Part 2-Parallel Operation of Heat Storage Tank Discharged and Application of Discharged Cold Water to Cooling Water for Refrigeration

Reduction of Electric Power Consumption for Thermal Storage Air Conditioning System in Daytime by Application of Discharged Cold Water to Cooling Water : Part 2-Parallel Operation of Heat Storage Tank Discharged and Application of Discharged Cold Water to Cooling Water for Refrigeration

Energy efficient hybrid nanocomposite-based cool thermal storage air conditioning system for sustainable buildings

The quest towards energy conservative building design is increasingly popular in recent years, which has triggered greater interests in developing energy efficient systems for space cooling in buildings. In this work, energy efficient silver–titania HiTES (hybrid nanocomposites-based cool thermal energy storage) system combined with building A/C (air conditioning) system was experimentally investigated for summer and winter design conditions. HiNPCM (hybrid nanocomposite particles embedded PCM) used as the heat storage material has exhibited 7.3–58.4% of improved thermal conductivity than at its purest state. The complete freezing time for HiNPCM was reduced by 15% which was attributed to its improved thermophysical characteristics. Experimental results suggest that the effective energy redistribution capability of HiTES system has contributed for reduction in the chiller nominal cooling capacity by 46.3% and 39.6% respectively, under part load and on-peak load operating conditions. The HiTES A/C system achieved 27.3% and 32.5% of on-peak energy savings potential in summer and winter respectively compared to the conventional A/C system. For the same operating conditions, this system yield 8.3%, 12.2% and 7.2% and 10.2% of per day average and yearly energy conservation respectively. This system can be applied for year-round space conditioning application without sacrificing energy efficiency in buildings.

Thermodynamic model of a thermal storage air conditioning system with dynamic behavior

A thermodynamic model was developed to predict transient behavior of a thermal storage system, using phase change materials (PCMs), for a novel electric vehicle climate conditioning application. The main objectives of the paper are to consider the system’s dynamic behavior, such as a dynamic air flow rate into the vehicle’s cabin, and to characterize the transient heat transfer process between the thermal storage unit and the vehicle’s cabin, while still maintaining accurate solution to the complex phase change heat transfer. The system studied consists of a heat transfer fluid circulating between either of the on-board hot and cold thermal storage units, which we refer to as thermal batteries, and a liquid–air heat exchanger that provides heat exchange with the incoming air to the vehicle cabin. Each thermal battery is a shell-and-tube configuration where a heat transfer fluid flows through parallel tubes, which are surrounded by PCM within a larger shell. The system model incorporates computationally inexpensive semi-analytic solution to the conjugated laminar forced convection and phase change problem within the battery and accounts for airside heat exchange using the Number of Transfer Units (NTUs) method for the liquid–air heat exchanger. Using this approach, we are able to obtain an accurate solution to the complex heat transfer problem within the battery while also incorporating the impact of the airside heat transfer on the overall system performance. The implemented model was benchmarked against a numerical study for a melting process and against full system experimental data for solidification using paraffin wax as the PCM. Through modeling, we demonstrate the importance of capturing the airside heat exchange impact on system performance, and we investigate system response to dynamic operating conditions, e.g., air recirculation.

Calculation Model of Peak Power Load Shifting of Electric Thermal Storage Air-Conditioning System

The government and the power grid corporations pay close attention how to evaluate the peak power load shifting ability of electric thermal storage air-conditioning system scientifically and rationally. The evaluation method of existing standard was analyzed briefly, and a new operable evaluation model based on the field tests was put forward. Based on the above analysis, the peak power load shifting of four projects was analyzed. Example shows that the analysis model can provides the basis for calculating the power load shifting indicator of electric thermal storage air-conditioning project.

Cumulative exergy analysis of ice thermal storage air conditioning system

Based on the cumulative exergy analysis method, the effect of incorporating the Ice Thermal Storage (ITS) air conditioning system in power supply is analyzed. Not only the cumulative exergy of air conditioning system is considered, but also that of the processes consuming the power generated by the same peak regulating unit. The results show that the total cumulative exergy consumption of all processes consuming the power supplied by the peak generating unit, increases as the ITS system is applied. However, the average cumulative exergy variation, which is the ratio between the increment of the cumulative exergy consumption (ΔCEx) and the cooling load of the ITS system (QITS), decreases slightly as QITS increases. It exhibits a linear relationship with the operating load of the power generating unit and QITS. And, it decreases as either of the two parameters increases. These results are verified by two case studies.

A study on demand response effect of thermal storage air-conditioning systems in consideration of electricity market prices

This paper evaluates the economic impact of the introduction of customer-owned Thermal Storage Air-conditioning (TSA) systems, in an electricity market, from the viewpoint of the load service entity (LSE). We perform simulations on the condition that several thousand customers install TSA systems and shift peak demand in an electricity market by one percent. Our numerical results indicate that the purchase cost of the LSE was reduced through load management of customers with TSA systems. The introduction of TSA systems also reduced the volatility of the market clearing price and reduced the whole-trade cost in an electricity market. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(1): 18–27, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21091

A Study of Demand Response Effect of Thermal Storage Air-Conditioning Systems in Consideration of Electricity Market Prices

This paper evaluates the economic impact of the introduction of customer-owned Thermal Storage Air-conditioning (TSA) systems, in an electricity market, from the viewpoint of the load service entity. We perform simulations on the condition that several thousand customers install TSA systems and shift peak demand in an electricity market by one percent. Our numerical results indicate that the purchase cost of the LSE was reduced through load management of customers with TSA systems. The introduction of TSA systems also reduced the volatility of market clearing price and reduced the whole-trade cost in an electricity market.

C-24 杭基礎を利用した自然エネルギーによる土壌蓄熱空調システムの分析 : (その2)シミュレーションによるシステムの運転方法の検討

C-24 杭基礎を利用した自然エネルギーによる土壌蓄熱空調システムの分析 : (その2)シミュレーションによるシステムの運転方法の検討

D-46 地中熱源ヒートポンプを有した蓄熱式空調システムの運転実績調査 : (第3報)本蓄熱空調式システムの運転評価

D-46 地中熱源ヒートポンプを有した蓄熱式空調システムの運転実績調査 : (第3報)本蓄熱空調式システムの運転評価

Study on the Installation of Thermal Storage System in Residential Houses

In recent years, residential houses have become more airtight and better insulated, and some, along with the IT revolution have been equipped with SOHO applications. This leads to a decrease in the heating load, while increasing electricity consumption in the daytime. On the other hand, electricity demand has increased in the summer, while the load rate of equipment in electricity plants has been decreased. Here a new thermal storage air conditioning system, using direct heat exchange, is proposed for a residential house, while its possibility and availability have been studied according to the prediction of energy consumption, which demonstrates the effectiveness of the thermal storage system for residential houses.