Thermal Storage Tank Research Articles

Development of a simplified model of a water thermal storage tank for district heating network modeling tool

Development of a simplified model of a water thermal storage tank for district heating network modeling tool

Integrated Energy Management in Small-Scale Smart Grids Considering the Emergency Load Conditions: A Combined Battery Energy Storage, Solar PV, and Power-to-Hydrogen System

This study introduces an advanced Mixed-Integer Linear Programming model tailored for comprehensive electrical and thermal energy management in small-scale smart grids, addressing emergency load shedding and overload situations. The model integrates combined heat and power sources, capable of simultaneous electricity and heat generation, alongside a mobile photovoltaic battery storage system, a wind resource, a thermal storage tank, and demand response programs (DRPs) for both electrical and thermal demands. Power-to-hydrogen systems are also incorporated to efficiently convert electrical energy into heat, enhancing network synergies. Utilizing the robust Gurobi solver, the model aims to minimize operating, fuel, and maintenance costs while mitigating environmental impact. Simulation results under various scenarios demonstrate the model’s superior performance. Compared to conventional evolutionary methods like particle swarm optimization, non-dominated sorting genetic algorithm III, and biogeography-based optimization, the proposed model exhibits remarkable improvements, outperforming them by 11.4%, 5.6%, and 11.6%, respectively. This study emphasizes the advantages of employing DRP and heat tank equations to balance electrical and thermal energy relationships, reduce heat losses, and enable the integration of larger photovoltaic systems to meet thermal constraints, thus broadening the problem’s feasible solution space.

Optimal Scheduling of Virtual Power Plants Under a Multiple Energy Sharing Framework Considering Joint Electricity and Carbon Trading

The virtual power plant (VPP) is an excellent approach for mitigating the intermittency and fluctuation of renewable energy sources. The present work proposes an optimal scheduling model for VPPs to leverage the benefits of joint electricity and carbon trading from the perspective of multiple energy-sharing mechanisms. First, the optimal sharing scheduling model of the electric, thermal, and hydrogen energy was established. The model integrates various components, including wind turbines, photovoltaic units, electrolytic cells, combined heat and power units, hydrogen-doped gas boilers, electric energy storage, thermal storage tanks, and hydrogen storage tanks. Then, the model incorporates a tiered carbon trading mechanism to minimize operating and trading costs. Finally, numerical results indicate that, compared with the independent operation of virtual power plants and the lack of joint electricity and carbon trading, the optimal scheduling scheme proposed in this paper reduces the total cost and carbon emissions of the three VPPs by 3.3% and 49.7%, respectively. This demonstrates that the proposed model can effectively reduce the total operating expenses of VPPs by facilitating the allocation of electric, thermal, and hydrogen energy and achieving low-carbon emission operations.

Performance analysis and optimization of a combined cooling, heating and power system based on active regulation of thermal energy storage

The energy storage unit can significantly address the issue of mismatch between the energy supply and demand of the combined cooling, heating and power (CCHP) system. Therefore, this article proposes a micro-gas turbine coupled with low-concentrating photovoltaic/thermal CCHP system with thermal energy storage active regulation, which can change the thermoelectric output ratio of the micro-gas turbine. The impact of the volume of the heat storage tank and the changes in ambient temperature on the system's performance is analyzed. This system is optimized with the objective functions of primary energy consumption saving rate, carbon dioxide emission reduction rate, total annual cost saving rate and exergy efficiency maximization. The results indicate that increasing the volume of the thermal energy storage tank enhances the exergy efficiency. Furthermore, an increase in ambient temperature can improve the objective functions. The optimum comprehensive performance of this system is achieved when the thermal energy storage tank volume is 40 m³ and the gas boiler capacity is 241.16 kW. With the thermal energy storage active regulation, the primary energy consumption, carbon dioxide emissions and annual total cost of the system decline by 2.51%, 2.37% and 1.22%, and the system exergy efficiency improves by 1.98%.

Heat Transfer in The Energy Storage During Solidification

Phase-change materials combined with thermal energy storage technology can improve energy efficiency. This study aims to analyse heat transfer in thermal energy storage tanks under solidification conditions. This involves developing storage tanks with three different numbers of paraffin balls: 4, 6, and 8 balls) in the TES tank. The tanks were designed for residential use, and the analysis will use Computational Fluid Dynamics (CFD) approaches to evaluate heat transfer efficiency. This comprehensive investigation seeks to optimise the configuration and operation of PCM-based thermal energy storage systems for residential applications. Increasing the number of paraffin balls resulted in a more uniform temperature distribution and a larger total heat transfer rate due to the larger surface area available for heat transfer; however, fewer paraffin balls led to a more significant pressure drop in the tank. Based on these findings, it is suggested to use a TES tank with a larger number of paraffin balls to improve heat transfer efficiency and temperature uniformity in residential applications.

Mass Flow Control Strategy for Maximum Energy Extraction in Thermal Energy Storage Tanks

Abstract This paper introduces an experimental approach to enhance thermal energy storage (TES) tank performance by employing a novel control strategy and an automatic flow valve. The valve adjusts mass flow to minimize heat loss and maximize useful heat within a specified input–output temperature range. Experiments were conducted indoors, simulating input heat via an electric heating element, and adhering to ANSI/ASHRAE 93-2010 standards. In the proposed control strategy, the set point is self-regulated based on an input value which in this case is the heat introduced into the TES system. In this way, when there is more input heat available, the mass flow will increase to obtain more useful heat at the output and, on the contrary, when there is less heat available, the mass flow will be reduced to obtain greater exergy. A comparison between this strategy and conventional on–off control systems was conducted, evaluating their performance based on useful heat obtained over an 8-h period with varying input heat levels. Results demonstrate that the proposed flow control methodology consistently outperforms on–off control, achieving a maximum 13.56% increase in useful heat under optimal conditions. This underscores the effectiveness of the novel control strategy in maximizing thermal energy storage tank efficiency.

Thermodynamic analysis of a solar-fed heat upgrade system using the reverse air brayton cycle

This analysis focuses on exploiting solar energy to meet industrial energy needs. It is based on upgrading solar heat production using surplus electricity from renewables to generate high-temperature industrial process heat. The approach involves the use of efficient evacuated flat plate solar thermal collectors coupled with a thermal storage tank to power a reverse air Brayton heat pump for high-temperature heat production. A Matlab algorithm has been developed to dynamically analyse energy balances across the system. The analysis is conducted for the location of Komotini, Greece and the results regard the operation of a system for a typical summer week. For the baseline design point with a 1000 m2 collecting area and 50 m3 thermal tank volume, the average daily process heat production for the industry is 8.63 MWh, while the average daily coefficient of performance (COP) for the heat pump is 1.478. Moreover, the present work includes results regarding the parametric performance of the system for different combinations of collecting area and thermal tank volume. It was demonstrated that with the optimization of the solar thermal collector area and thermal tank volume, the daily average COP can be increased up to 23.1 %. Finally, the influence of the units of transfer area of the heat exchangers on the coefficient of performance has been investigated.

Analysis of thermal and mechanical properties with inventory level of the molten salt storage tank in central receiver concentrating solar power plants

Molten salt thermal energy storage (TES) tanks ensure steady power output of concentrating solar power (CSP) plants; however, recent tank failures have highlighted the need for further analysis. Current studies primarily focus on analyzing the molten salt flow, heat transfer, and thermal efficiency. Additionally, research on the latest tank structures is limited and lacks newest experimental validation. This study measures temperature and molten salt inventory levels in the high-temperature tank at a 50 MW central receiver CSP plant, connected to the power grid in 2019. A multi-physics model was developed to evaluate thermal and mechanical properties of TES tanks by combining computational fluid dynamics and finite element modeling using real plant data. Heat loss, temperature, displacement, and stress distribution of the tank at different inventory levels were investigated. Results show that ambient air velocity near the tank roof reaches 2.14 m/s, much higher than 0.2 m/s near the wall. The temperatures of inventory fluid and tank are close, varying slightly at different levels due to thermal conduction and radiation. Because the heat loss strongly depends on temperature, the total tank loss remains nearly constant across inventory levels. Larger temperature gradients and thermal stresses are primarily localized along the tank floor edge and the air-salt interface. Notably, the maximum thermal stress at the tank edge is three times higher than that at the interface. The magnitude of total stress changes by less than 5 MPa with and without thermal load, indicating that high temperatures exert only a minor impact on tank stress. In contrast, thermal load significantly affects tank deformation, particularly at the roof edge, where values exceed 150 mm. Despite the large variation in molten salt levels, tank wall temperatures and displacements present a minor change, suggesting a weak correlation with inventory levels. The findings obtained in this study provide important insights on the TES tank that could be used to optimize tank design and operation strategies.

Numerical analysis of a solar thermal energy storage tank filled with phase change material under three fin arrangements

Numerical analysis of a solar thermal energy storage tank filled with phase change material under three fin arrangements

Comparison between cold and hot network in a solar district cooling system

Abstract Heat-powered absorption cooling have attracted attention in recent decades, especially in regions with hot and arid climates a higher availability of solar radiation, can be exploited in solar-assisted District Cooling (SDC) system to reduce costs. The paper proposes a comparison of two Solar District Cooling configurations powered by a PTC field with thermal storage and an absorption chiller. The first configuration, called cold network, has a large hot water storage tank slaved to a single chiller that produces all the chilled water that is distributed to the network; in the second configuration, called hot network, the water heated in the solar array is sent through the network directly to thermal storage tanks, located near the buildings to be served, where each agglomeration has its own chillers. A techno-economic optimization was performed for the two configurations by varying the Solar Fraction (SF), from 25% to 100%. When solar radiation is not sufficient to meet demand, an auxiliary electric chiller will be used. The results show that component size increases linearly with SF up to 75%. To achieve a fully renewable solution, components need to be significantly oversized. Generally, a SDC system in a centralized configuration offers improved performance and reduced distribution losses. However, this is not the case for a scenario with unitary SF, where the distribution network takes on an additional thermal reserve role.

Innovative solar-assisted direct contact membrane distillation system: Dynamic modeling and performance analysis

The study presents an innovative solar-assisted dual-tank direct contact membrane distillation (DCMD) system designed to enhance the operational stability and efficiency of solar-powered desalination. The proposed system integrates a dual thermal storage tank configuration, allowing for continuous operation by alternating between two tanks that store pre-heated water, thereby mitigating the impact of solar energy fluctuations. The dynamic modeling approach used in this study predicts the system's performance under varying solar conditions, focusing on key parameters such as permeate flux, evaporation efficiency, and specific thermal energy consumption. The simulation results show that the system achieves an average permeate flux of 14.4 L/h m² and a thermal efficiency of 53.3 % at a hot water temperature of 60 °C, with a corresponding average specific thermal energy consumption of 1567 kWh/m³. These findings highlight a substantial improvement in both thermal efficiency and water production compared to conventional single-tank systems.The dual-tank DCMD system is particularly suited for deployment in remote or arid regions where stable and efficient freshwater production is critical. This research provides a comprehensive analysis of a novel solar-assisted desalination technology, contributing to the advancement of sustainable water resources management by providing a reliable and scalable solution that can maintain high operational efficiency even in remote areas with variable solar conditions.

Research on performance and potential of distributed heating system for peak shaving with multi-energy resource

Climate change and its negative effects are driving the global shift from fossil fuels to renewable energy sources. To tackle the dependency on traditional energy sources in harsh winter regions and improve heating quality during periods of thermal demand fluctuations, this paper proposes a new distributed heating peak shaving system (DHPS). The system combines municipal heat and clean energy within the secondary network while reducing the return water temperature in the primary network. It comprises solar collectors, electric thermal storage tanks (ETST), and absorption heat pump (AHP) units, integrated into conventional heat exchange stations. The system operates in two modes to manage peak and off-peak loads respectively, with TRNSYS simulation used to evaluate performance across a range of peak-shaving gradients. A multidimensional comprehensive assessment is conducted between the DHPS under optimal peak shaving coefficient (θ) conditions and conventional peak clipping boiler (PCB). Results indicate that DHPS achieves a high primary energy ratio (PER) of 1.251 at θ = 0.5, reducing combustion emissions by nearly 40%. The static payback period (PBP) of the system is 3.5 years. When the electricity price drops to 0.275 CNY, its operational costs are comparable to PCB. DHPS caters to the energy characteristics of cold regions where electricity supply exceeds demand. It enables flexible peak shaving while ensuring the complete utilization of clean energy and effectively utilizing waste heat from power plants.

Optimizing solarized desalination unit through the implementation of 4-step MED method using energy, exergy, economic and environmental analysis

The consumption of thermal energy in thermal desalination plants leads to a higher price for the fresh water they produce compared to other methods. By utilizing optimization techniques, it is possible to lower both energy consumption and price. The focus of this paper is on optimizing a solarized desalination unit through the implementation of the 4-step MED method with a PTC collector. To achieve this objective, the NSGA II algorithm was implemented in MATLAB using a function for optimization. This algorithm is known for its cost-effectiveness and high energy efficiency. According to the results, there has been an improvement in the fresh water flow rate, desalination efficiency, and GOR, with values reaching 126.87, 53.6%, and 3.66 respectively, compared to the previous values of 116.5, 49.21%, and 3.32. In the ideal condition, the power generated is 6089 kW, priced at 3.28 cents per kilowatt, and the cost of producing fresh water is 8.49 dollars per cubic meter, which decreases as the process lifespan increases. Solar collectors and thermal tanks account for the largest portion (64%) of exergy destruction, as indicated by the exergy analysis. Optimization of the process has led to energy and exergy efficiencies of 59.8% and 58%, respectively, representing a notable enhancement of around 10% in the system's lifespan. The optimal mode also includes the completion of the sensitivity analysis. The process was subjected to LCA analysis, and the results indicated that the largest impact is on human health, with the collectors and thermal storage tanks being responsible for most of the pollution. As a result, the optimized process has delivered outstanding results while also being environmentally conscious.

Day-Ahead Nonlinear Optimization Scheduling for Industrial Park Energy Systems with Hybrid Energy Storage

Hybrid energy storage can enhance the economic performance and reliability of energy systems in industrial parks, while lowering the industrial parks’ carbon emissions and accommodating diverse load demands from users. However, most optimization research on hybrid energy storage has adopted rule-based passive-control principles, failing to fully leverage the advantages of active energy storage. To address this gap in the literature, this study develops a detailed model for an industrial park energy system with hybrid energy storage (IPES-HES), taking into account the operational characteristics of energy devices such as lithium batteries and thermal storage tanks. An active operation strategy for hybrid energy storage is proposed that uses decision variables based on hourly power outputs from the energy storage of the subsequent day. An optimization configuration model for an IPES-HES is formulated with the goals of reducing costs and lowering carbon emissions and is solved using the non-dominated sorting genetic algorithm II (NSGA-II). A method using the improved NSGA-II is developed for day-ahead nonlinear scheduling, based on configuration optimization. The research findings indicate that the system energy bill and the peak power of the IPES-HES under the optimization-based operational strategy are reduced by 181.4 USD (5.5%) and 1600.3 kW (43.7%), respectively, compared with an operation strategy based on proportional electricity storage on a typical summer day. Overall, the day-ahead nonlinear optimal scheduling method developed in this study offers guidance to fully harness the advantages of active energy storage.

Experimental and comparative analysis between nitrile rubber foam insulated and vacuum insulated fiber reinforced plastic tank used in a low temperature sensible heat storage system for building space cooling applications

AbstractThermal energy storage devices are gaining importance and momentum in the building space cooling and renewable energy applications. Retaining the stored energy for long hours through proper insulation is crucial in achieving economic benefits. In the present research, a novel composite material (FRP) is introduced for the development of cool storage tank along with two different methods of insulation (nitrile rubber foam insulation and vacuum insulation) to assess the performance of cool energy retention. The results show that the effect of vacuum insulation is lower compared with nitrile rubber foam insulation. This is due to the low specific heat capacity of the FRP material compared with air that increases the surface temperature of the tank than the ambient air during the day time in the case of vacuum insulation. Hence the study concludes that the additional layer of insulation material with high specific heat capacity than the ambient air to be added on the surface to avoid the overheating of the wall surface. The results are useful in designing the insulation for thermal storage tanks and managing the heat loss.

Achieving net zero energy penalty in post-combustion carbon capture through solar Energy: Parabolic trough and photovoltaic technologies

The adoption of carbon capture systems presents a pivotal strategy for mitigating greenhouse gas emissions, notably carbon dioxide. Nevertheless, the substantial surge in energy consumption associated with such systems remains a significant challenge. Addressing this challenge necessitates the integration of renewable energy sources. This study is dedicated to optimizing the conventional post-combustion carbon capture configuration, focusing on energy, exergy, and exergoeconomic considerations. The optimized configuration showcases a noteworthy 10 % reduction in overall energy penalties compared to its conventional counterpart, primarily attributed to diminished energy utilization in the reboiler. To achieve absolute sustainability and eliminate energy penalties in the optimized configuration, integration of a parabolic trough collector for steam provision to the reboiler and photovoltaic solar collectors for powering the plant’s equipment was undertaken. Furthermore, the incorporation of solar thermal storage tanks and batteries enables the storage of excess heat and electricity, ensuring operational continuity for up to 13 h in the absence of sunlight, such as during nighttime. The final optimized configuration manifests a commendable 14 % enhancement in exergoeconomic performance relative to the conventional configuration, thereby realizing zero energy penalties. This achievement renders the optimized configuration a compelling and viable choice for carbon capture units.

Enhanced temperature regulation in compound heating systems: Leveraging guided policy search and model predictive control

With the widespread application of solar-energy-air-source heat pump composite heating, optimizing the regulation of air temperature in heating zones, enhancing system thermal comfort, and reducing energy consumption have become crucial. To ensure residential comfort while minimizing HVAC system energy costs, a control method combining guided policy search (GPS) with model predictive control (MPC) is proposed for composite heating systems. This method replaces state estimation in MPC with policy search and substitutes the offline trajectory optimization used in guided policy search with MPC, thus integrating the strengths of both approaches. This strategy not only improves control precision but also reduces energy consumption and enhances system robustness. The GPS-MPC control algorithm was validated against reinforcement learning and MPC. A simulation model was developed and validated on a real physical platform. Simulations compared the control effects of on-off control and MPC on pump frequency, flow rate, stratified thermal storage tank temperature, component, and system energy consumption. The data results indicate that the GPS-MPC algorithm offers superior predictive accuracy, efficiency, and robustness in composite heating control systems compared to conventional methods. Under the GPS-MPC strategy, indoor temperature fluctuations, pump frequency response speed, and energy consumption were significantly improved, with temperature fluctuation limited to only 0.8 °C, and the system achieving energy savings of over 12 %.

Analysis of the Use of Energy Storage in the Form of Concrete Slabs as a Method for Sustainable Energy Management in a System with Active Thermal Insulation and Solar Collectors

One effective approach to reducing the energy required for heating buildings is the use of active thermal insulation (ATI). This method involves delivering low-temperature heat to the exterior walls through a network of pipes carrying water. For ATI to be cost-effective, the energy supply must be affordable and is typically derived from geothermal or solar sources. Solar energy, in particular, requires thermal energy storage (TES) to manage the gap between summer and the heating season. A building that integrates various renewable energy systems and heating/cooling technologies should be managed efficiently and sustainably. The proper integration of these systems with smart management strategies can significantly lower a building’s carbon footprint and operational costs. This study analyzes the use of concrete slabs as a method for sustainable energy management in a system incorporating active thermal insulation and solar collectors. Using ambient temperature and solar radiation data specific to Cracow, Poland, the simulations evaluate the feasibility of employing a concrete slab positioned beneath the building as a thermal storage tank. The results reveal some drawbacks of using concrete slabs, including high temperatures that negatively affect system efficiency. Increased temperatures lead to higher heat losses, and during summer, inadequate insulation can cause additional heat leakage into the building. The findings suggest that water may be a more effective alternative for thermal energy storage.

Preparation of dodecahydrate disodium hydrogen phosphate shape-stabilized composite phase change materials and their experimental investigation in solar thermal storage and exothermic systems

To alleviate the mismatch between energy supply and demand caused by the spatial and temporal distribution mismatch and weather uncertainty during solar energy utilization, solar energy is combined with phase change thermal storage technology to improve the performance of solar thermal storage systems. In this study, a shape-stabilized composite phase change material with a highly absorbent resin structure is proposed as thermal storage material. This material exhibits a latent heat of phase change of 246.5 J/g, a thermal conductivity of 1.968 W/(m·K), and maintains good stability after 200 thermal cycles. Subsequently, a detachable experimental setup integrating solar energy with a phase change thermal storage tank was designed and constructed. The effects of inlet and outlet hot water flow rates and heat source temperature on heat storage time and the amount of stored water were investigated separately. The experiments show that increasing the heat source temperature during storage effectively shortens the storage time, and that the largest effective amount of hot water is obtained when the exothermic flow rate is 300 L/h. The study's results are significant for broadening solar energy utilization, alleviating the mismatch between solar energy supply and demand, and evaluating the thermal performance of latent heat storage systems.

Transient modeling of stratified thermal storage tanks: Comparison of 1D models and the Advanced Flowrate Distribution method

Thermal energy storage (TES) is one of the key technologies for enabling a higher deployment of renewable energy. In this context, the present study analyzes the modeling strategies of one of the most common TES systems: stratified thermal storage tanks. These systems are essential to many solar thermal installations and heat pumps, among other clean energy technologies. Three different one-dimensional tank models are compared by their computing speed and resilience to long time steps. Two of the models analyzed are numerical, one being explicit and the other one implicit, and the other is analytical. The models are validated against data from experiments carried out considering small-scale stratified tanks, showing that their performance can be improved by using the Advanced Flowrate Distribution (AFD) method. The results show that the analytical model maintains its accuracy with longer time steps and is robust against divergence. Conversely, the numerical models show equivalent performance for short time steps, while the computation time is reduced. Although the AFD method shows promising results by achieving an improvement of 43% in terms of Dynamic Time Warping, its parameter optimization must be generalized for different tank designs, flow rates, and temperatures.