Seasonal Thermal Energy Storage Research Articles

Robust Design of 5th Generation District Heating and Cooling (5GDHC) Systems with Seasonal Thermal Energy Storage via GIS Assessment

This research addresses the need for a method to compare waste heat potential and recovery in 5th Generation District Heating and Cooling (5GDHC) systems. Prosumer buildings, known for enhancing flexibility, are analyzed using Geographic Information Systems (GIS) and image vectorization to evaluate 5GDHC systems. The study predicts the amount of waste heat available with an R2 of 0.96, utilizing Chaikin's algorithm to refine thermal images for automatic recognition of the sources of waste heat. Emphasis is placed on the absence of a method for asset design in 5GDHC, with considerations for annual energy calculations, radial network connections, and energy shares among building types. Recommendations for building connecting in Belgium are proposed, favoring 'B'/'C'-labeled buildings. The research explores the impact of building design on heating and suggests energy savings through regulation strategy changes. Dynamic models for heat pumps aim to reduce errors and emissions. The study connects energy indicators and GIS software, contributing to a top-down design approach in 5GDHC systems. The overall goal is to contribute to decarbonization and reduce CO2 emissions in the energy sector.

Analysis of Different Climate-Neutral Heat Supply Concepts for a District Heating System near Munich with Deep Geothermal Heat as the Primary Heat Source

District heating systems are one key element of the transition towards a climate-neutral heat supply since they allow for the use of various renewable energy sources and the increase of renewable heat generation, in particular when combined with seasonal thermal energy storage. Deep geothermal heat is a renewable heat source that can be used to cover the thermal base load of such a district heating system. Also in combination with other renewable heat sources, such as solar thermal or heat pumps, a climate-neutral heat supply for districts or even complete cities can be realised. This paper deals with the analysis of different climate-neutral heat supply concepts that were elaborated for a district heating system currently in the planning phase using deep geothermal heat as the primary heat source, located in the town of Graefelfing near Munich, Germany. The authors present, discuss and assess various options regarding renewable heat sources and including (seasonal) thermal energy storage, to fully cover the thermal loads of a new district heating system in a technically, economically and environmentally favourable way. As a result of this study, a heat supply concept was selected, in which a heat pump using the return flow of the deep geothermal circuit as a heat source maximises the utilisation of the available deep geothermal heat source to cover more than 95 % of the annual heat demand by deep geothermal heat combined with a heat pump.

Experimental parametric evaluation of adsorption characteristics for silica gel - water based open-bed system for seasonal thermal energy storage

This study aims to investigate the potential of using commercial silica gel as an energy storage material in a bulk-scale open bed adsorption-based system to achieve efficient domestic heating using renewable energy sources. Designing an efficient thermal energy storage (TES) system for practical use requires understanding of the sorption properties of the adsorbent and the effects of different operating and physical parameters on the sorption process. One critical parameter that significantly affects the energy storage density when scaling up from a laboratory to a prototype system is the amount of adsorbent in the reactor. Surprisingly, this aspect has been overlooked in previous studies. To address this research gap, a laboratory-scale test rig was designed and constructed. This rig enables the evaluation of the effects of different operating parameters (such as relative humidity, flow rate, and regeneration temperature) and physical parameters (such as the quantity of adsorbent and particle diameter) on the energy storage density of silica gel and the temperature lift in the process. The water adsorption capacity of the silica gel was measured in-house to assist in future theoretical modelling of a prototype TES system. Optimum operating conditions were determined for the system, with a relative humidity of 80 %, an air flow rate of 100 L/min, and material regeneration at 120 °C. The system's performance in terms of material energy storage density and maximum temperature lift was observed for varying amounts of adsorbent, particle diameter, and regeneration temperature at these optimal operating conditions. Finally, the required storage volume to meet domestic space heating demands was estimated based on optimal discharging conditions and compared to other experimental and theoretical studies involving silica gel-based energy storage systems.

Case study on combined heat and water system for district heating in Beijing through recovery of industrial waste heat in Tangshan

With the proposal of China's dual-carbon goal, the recovery of industrial waste heat (IWH) for district heating has gained increasing attention. Recently, some scholars have proposed that combined heat and water (CHW) systems are more economical compared with separate heat and water supplies. Beijing lacks desalinated water (DW) and clean low-carbon heat, whereas Tangshan in Hebei Province is rich in IWH. By combining CHW with seasonal thermal energy storage, a case of long-distance transport of hot DW from Tangshan to Beijing was planned, and the costs, energy consumption, and feasibility were analyzed. As a result, under the optimal heat source temperature and effect number of 70 °C and 10 for seawater desalination, the heat from various IWH sources of the three costal steel plants is recovered maximally to produce about 35000 t/h of 95 °C DW. Then, the hot DW is transported to Beijing with a long-distance heat loss ratio controlled below 3 %. Annually, 271.2 million tons of DW and 91.5 million GJ of heat is supplied. The introduction of IWH can save 2.68 billion Nm3 of natural gas per year and the discounted payback period is about 10 years, which has obvious energy-saving, environmental, and economic benefits.

Multiscale analysis of a seasonal latent thermal energy storage with solar collectors for a single-family building

This paper presents a comprehensive system-to-CFD multiscale analysis of a seasonal thermal energy storage (STES) system based on phase change materials (PCMs) for efficient energy storage and release for space heating. The study investigates the impact of various factors, including the geometry of the individual storage tank and the thermo-fluid dynamic parameters of the heat transfer fluid on the system performance. The work focuses on STES integration with space heating system to meet the thermal energy demands of a typical single-family building located in Naples – South Italy, typical coastline Mediterranean climate. The primary goal is to assess the behaviour of the system-integrated PCM tank and its characteristic parameters, leading to the proposal of sustainable approaches that include renewable energy sources and partially fulfil the building thermal loads. Among the Scenarios, one stands out as it achieves a better operation, allowing storage and solar collectors to cover around 69.2 % of the winter heating demand, i.e., 3.06 MWh. The study also discusses the benefits of modular system operation, as evidenced by Scenario 3, which allows for the parallel discharge of multiple LHTES tanks, leading to an enhancement in efficiency compared to other Scenarios. Results indicate that the total energy discharged by a single STES is 56.30 kWh, with a latent heat fraction released over a time of 111 h and an average temperature difference of 5.65 °C. The tank efficiency reaches a value of 90.4 %, demonstrating the effectiveness of the STES system in meeting heating demands.

Maximizing energy efficiency in wastewater treatment plants: A data-driven approach for waste heat recovery and an economic analysis using Organic Rankine Cycle and thermal energy storage

Maximizing energy efficiency through waste heat recovery (WHR) processes is crucial for sustainable and eco-friendly operations across multiple industries, notably in wastewater treatment plants (WWTPs). This work proposes a comprehensive approach for assessing the WHR feasibility in WWTPs, structured in two main objectives. Firstly, an Artificial Neural Network (ANN) model is developed to accurately predict WHR based on operational data, including biogas temperature, biogas pressure, daily production in kWh, and WHR values in kWhth. The second objective focuses on economically evaluating the WHR feasibility based on the estimated WHR values obtained by the ANN model, and then realistically assessing the economic feasibility of integrating the Organic Rankine Cycle (ORC) and Seasonal Thermal Energy Storage (STES) systems. With an application to the As-Samra WWTP located in Jordan, the developed ANN model demonstrates promising results in the validation phase, with a root mean square error (RMSE) of 2206 kWh/day, a mean absolute error (MAE) of 1674 kWh/day, and an R-squared (R2) value of 68%. On the other hand, the economic analysis reveals that an optimal ORC system of 412.14 kWe capacity yields a Net Present Value (NPV) of 2.09 million US dollars, a Levelized Cost of Energy (LCOE) of 0.0749 USD/kWh, a Payback Period (PBP) of 4.8 years, and annual revenues of 428 kUSD. This work also investigates the techno-economic feasibility of integrating ORC-STES. Results indicate that the LCOE and PBP are highly affected by the ORC's capital cost, and integrating STES increases the LCOE to 0.0824 USD/kWh, rendering its integration with ORC infeasible. This study aims to advance the understanding and application of WHR in WWTPs, paving the way for more efficient and sustainable practices in the field.

Solar thermal vs. PV with a heat pump: A comparison of different charging technologies for seasonal storage systems in district heating networks

The majority of district heating networks (DHNs) in Germany and other European countries are still supplied by fossil fuels. While several possible technical solutions exist to decarbonize DHNs, the problem is the availability of solar energy – thermal and electric – or other renewable electric sources during winter. A solution is to shift the available energy from the summer to the winter by using seasonal thermal energy storage systems. Especially pit thermal energy storage systems (PTES) have shown an economic advantage compared to other storage types. Therefore, we would like further to investigate the design of PTES under different techno-economic conditions.In this study, different charging options for the PTES were examined. Solar thermal energy was compared to photovoltaic (PV), supplying an air-source heat pump (ASHP). We developed an open-source Python package based on mixed-integer linear programming, minimizing the total system cost, i.e., the annuity, including opex and capex. The tool selects, operates, and designs energy converters and storages. Furthermore, it optimizes the network’s storage capacity during the operation. The optimization takes the characteristics of an existing DHN as input and designs the supply systems across different locations (LOCs). The model separates the hydraulic and thermal calculation and builds up a multi-stage process to consider temperatures inside the network and the PTES.The tool was applied to a DHN in Eastern Germany. The results show a low sensitivity to the electricity price in all concepts. Operating the PTES at low temperatures negatively affects the heat capacity, and therefore, it is best suited for high-temperature networks. The concept of PV with an ASHP is better suited for densely populated regions. However, both concepts have a total system cost above 20ct/kWh for an area price of over 120€/m2. For an electricity price of ca. 19ct/kWh, the total system cost is below 17ct/kWh for both concepts.

Long-term operational planning for flexible residential buildings with seasonal storage and capacity-based grid tariffs

When performing operation of the energy system in a building, it is difficult to accurately represent the uncertain long-term objectives in the short-term window, and the correlation between long-term objectives. This work investigates a strategic modelling framework for representing long-term incentives during short-term operational planning for an energy system within flexible buildings. Multi-stage backwards Stochastic Dynamic Programming (SDP) is used to decompose the yearly operational problem into smaller stages, and create long-term cost curves that captures the cost of adjusting long-term price signals, which in this work considers seasonal thermal energy storage and recurring monthly capacity-based grid tariff costs. The proposed method is analyzed for a flexible realistic Norwegian building located in Southern Norway, where the influence both price signals have on long-term operational performance is analyzed. Results show that the framework strategically optimizes the long-term seasonal storage together with the recurring monthly grid tariff, complementing each other by using the seasonal storage to reduce peak costs during winter. With both seasonal storage and monthly demand charge, yearly operational costs are reduced by 4.3% compared to only accounting for the grid tariff. Additionally, the operational performance achieved only a 0.9% higher cost compared to yearly simulation with perfect information.

Seasonal thermal energy storage using natural structures: GIS-based potential assessment for northern China

Seasonal thermal energy storage using natural structures: GIS-based potential assessment for northern China

Seasonal thermal energy storage as a complementary technology: Case study insights from Denmark and The Netherlands

Seasonal thermal energy storage (STES) has potential to act as an enabling technology in the transition to sustainable and low carbon energy systems. It is a relatively mature technology, providing a reliable and large-scale solution to seasonal variations in energy supply and demand where it has been deployed at scale. In practice, however, there remains minimal deployment of STES internationally, with only a small number of countries being exceptions. Here, we analyse STES development in two of these exceptions: the Netherlands and Denmark, and we consider the relevance of the Dutch and Danish STES experiences for other countries, such as the UK, where STES is currently marginal. In explaining the diffusion of STES in leading countries, and its limited uptake elsewhere, we pay attention to energy system context by investigating the complementarities – or misalignments – between different parts of energy systems which have influenced STES deployment. The contribution arising from our mainly qualitative and historical analysis is to demonstrate the importance of contextual factors such as national policy and complementarities between technical and social factors in influencing STES deployment. This approach, we argue, can complement and enrich engineering and economic perspectives on STES.

Drivers to allow widespread adoption of ATES systems: a reflection on 40 years experience in The Netherlands

Drivers to allow widespread adoption of ATES systems: a reflection on 40 years experience in The Netherlands

АКУМУЛЯТОРИ ТЕПЛОВОЇ ЕНЕРГІЇ

The article provides an analytical review of thermal energy storage. The reasons determining their demand are shown. It has been established that the market of thermal accumulators is developing quite dynamically. According to the forecast of the International Renewable Energy Agency, the global market for thermal accumulators may triple by 2030 from 234 GWh of installed capacity in 2019 to about 800 GWh in 2030. Investments in the development of thermal accumulators are expected to reach 13–28 billion US dollars. Their capacity for power generation can be 491–631 GWh, for heat supply – 143–199 GWh, for cooling – 23–26 GWh. Bloomberg NEF considers the main drivers of such a sharp increase in energy storage capacity are the US Inflation Reduction Act, which provides for more than $369 billion in financing for clean technologies, as well as the European Union's RE Power EU plan to reduce dependence on gas from Russia. The significant additional storage capacity expected from 2025 in the utility sector is in line with the very ambitious renewable energy targets set out in the REPowerEU plan. The purpose of this review is the search and analysis of thermal energy storage technologies for their possible use in the centralized heat supply of Ukraine. The conducted review showed that the most advanced technology for the accumulation of thermal energy is heat capacity of the material storage. It is the cheapest and most common in centralized heat supply. For short-term storage of heat energy, it is advisable to use storage tanks and main heat networks. Special insulated concrete underground storages of both natural and artificial origin are used for seasonal accumulation of thermal energy. A promising technology for seasonal thermal energy storage is an ice battery developed by the Viessmann company, which requires much less space than the heat capacity of the material storage technology. Thermochemical batteries are in the early stages of development, their demonstration samples may be manufactured by 2050. Keywords: battery, thermal energy, heat capacity, phase transition.

Dynamic characteristics and energy efficiency evaluation of a novel solar seasonal thermal storage - heating system

This paper proposes solar seasonal thermal energy storage system compounded with long-term and short-term energy storage tanks for a single-family dwelling, which using assisted water source heat pump to further improve the systems stability. With the objective of improving the solar energy utilization efficiency and reducing the primary energy consumption, the dynamic simulation model of the “heat collection-heat storage-heat supply” system under the non-stationary boundary conditions throughout the year is established. The energy transfer and conversion law of each subsystem and the dynamic operation characteristics are analyzed through simulation method. The system cooperative control strategy is proposed and parameter optimization is carried out. Results indicate that the annual heat collection efficiency of the water source heat pump composite system has been improved by 2.2 % compared with the electric auxiliary heating system. Meanwhile, the heat storage efficiency and the solar energy guarantee rate increased by 5.8 % and 8.3 %, respectively. Moreover, the optimal water source heat pump composite system not only improves energy efficiency and achieves the cost savings compared with the electric auxiliary heating system, but also reduces carbon dioxide emission by 10.3 %, which have great advantages for energy saving and emission reduction.

Techno-economic analysis of a biogas-fueled micro gas turbine cogeneration system with seasonal thermal energy storage

In this study, the techno-economic performance of an integrated energy system, which consisted of a biogas-fueled micro gas turbine, seasonal thermal energy storage using a borehole heat exchanger, and a heat pump for meeting the electricity and heating demand of a small hotel, was carried out. In this proposed system, excess heat from the MGT was charged into the BHE. During the periods of high heating demand, stored waste heat in the ground was extracted by a heat pump. A data-driven model of the MGT based on feed-forward neural networks was developed and validated to provide fast and accurate prediction results. A Modelica/Dymola modeling framework was then established to evaluate the techno-economic performance of the integrated energy system over its lifetime. An L16 orthogonal array given by the Taguchi method was employed to assess the influences of the number of the borehole, the length of the borehole, the distance between boreholes, and the flow rate in the BHE on the energy consumption of the heat pump system, and the NPV of the integrated energy system. First, single objective optimization was performed for both the energy consumption and the NPV separately. The importance order and contribution ratios of the design factors on the performance indicators were determined using the Taguchi and ANOVA methods. Afterward, GRA was used to perform multi-objective optimization of energy consumption and NPV simultaneously. The results showed that, in descending order of importance, the most significant design factors for overall performance were the flow rate in BHE, the length of the borehole, the number of the borehole, and the distance between boreholes. These factors contributed around 68%, 17%, 13%, and 2%, respectively, to the overall results. The optimal combination of parameter levels when considering the multiple performance characteristics was determined as A1B1C1D4, and the optimized energy consumption and NPV were found as around ∼15 GWh and 4 million NOK, respectively.

Techno-economic-environmental analysis of seasonal thermal energy storage with solar heating for residential heating in China

Seasonal thermal energy storage (STES) of solar heat is an option of interest for clean heat transition, as residential heating is often fossil fuel-based. This study 1) proposes an integrated optimization criterion to examine how local context influences the optimal configuration planning, techno-economic-environmental performance, and feasibility of STES application; 2) identifies the position of STES in comparison to other sustainable heating options considering the local context; and 3) provides a comprehensive and transparent showcase highlighting the importance of the local context in determining the feasibility of STES in the clean heating transition. The TRNSYS modeling tool is adopted to analyze the performance, and Pareto optimization is applied to treat the multi-objective optimization. The solar fractions and storage efficiencies of the four case studies range between 58-67% and 57–69%, respectively. STES has significant potential to reduce CO2 emissions (52–72%) compared to conventional heating systems. However, the heating cost of the STES system (5.4–8.7 €-ct/kWh) is more than twice that of the conventional heating system. The CO2 avoidance cost of the four case studies ranges between 114 and 368 €/t. Properly reducing the borehole number in cold climate zones and increasing the solar collector area in warm climate zones help improve the system performance.

Optimization of integrated energy systems considering seasonal thermal energy storage

Integrated energy system are an effective way to achieve sustainable energy development and build a low-carbon society. However, the combination of different units needs further investigation to determine the optimum configuration and operating strategy. To address the problem of large differences in user loads and renewable energy sources between seasons, a regionally integrated energy system, including the seasonal thermal energy storage system, is established. The seasonal thermal energy storage system is coupled with heat pumps and solar collectors. We optimize the planning and scheduling of each device in the integrated energy system on a planning horizon of one year. The results show that the integrated energy system with a ground source heat pump and seasonal thermal energy storage device can effectively reduce the cost of the operation planning by 9.1 %. The cost of purchased energy and carbon emissions have also been reduced by 23.4 % and 12.6 %, respectively. In addition, the study also found that the available area of solar radiation in a region influences the optimal configuration of the system.

A Long-Term Dynamic Analysis of Heat Pumps Coupled to Ground Heated by Solar Collectors

In agreement with the decarbonization of the building sector to meet the 2050 climate neutrality targets, borehole thermal storage for solar energy represents a potential solution to increase the energy efficiency of renewable energy plants. As is well known, electricity is not the optimum solution to integrate large inflows of fluctuating renewable energy. In the present paper, we investigate the possibility to use the solar collector to give energy to the borehole field. In detail, a solar-assisted geothermal heat pump is applied to a school located in Milan, Italy. In winter, both the energy from the solar collector and the heat pump are collected into a storage tank connected to the emission terminals, whereas, in summer, as there is no energy demand, the hot water from the solar collector flows into the geothermal probes. By means of this seasonal thermal energy storage technology, the intermittent solar energy collected and stored during the summer months can be utilized during the winter months when the heating demand is high. A long-term dynamic analysis is performed by employing Trnsys. The results show that solar collectors coupled with ground-source heat pumps can give an important contribution to the soil temperature drift, and this also applies in cases of un-balanced loads during the heating season. Moreover, the employment of solar collectors increases the seasonal coefficient of performance of the heat pumps and may rise to reductions to the probes field.

Optimal insulation of underground spherical tanks for seasonal thermal energy storage applications

The literature deals specifically with compressed gas characteristics, solar radiation, storage volume and heat load fluctuation in aboveground storage and thermal energy storage (TES) applications. To prevent their negative effects, the use of underground insulated spherical tanks in the storage process has been overlooked. This study details the physical and economic aspects of using insulation in underground spherical tanks for seasonal TES systems. In determining the storage heat load, the degree-time method is recommended for the heat transfer mechanism between soil and storage temperature degrees. Using life cycle cost analysis, the insulation thickness, energy saving and payback period in the underground spherical tank are discussed in detail for hot and cold storage capacities. The results of the study indicated that the degree-hour method can be used in the design of hot and cold TES systems despite the temperature fluctuation. Insulation can be taken care of in hot fluid storage instead of cold alternative. With insulation in the underground spherical tank, it is observed than about 200 % energy savings is possible with approximately 50 % shorter payback period. For the hot fluid storage with insulation, as the storage fluid temperature, soil thermal conductivity and tank diameter rise and the depth falls, but the optimum insulation thickness value increases. As a result, this study is expected to be a guide for further seasonal TES applications using insulation in underground spherical tanks.

Experimental validation of a numerical model for a sand-based seasonal thermal energy storage

A research facility with solar thermal collector system and a water-saturated, sand-based seasonal thermal energy storage (SSTES) is used to provide space heating and domestic hot water heating to homes in cold climates. A 3D finite difference model of the heat transfer in and around the SSTES is presented and validated with measured data. The SSTES has lost moisture over time, making its thermal properties difficult to estimate. Additionally, the experimental data shows the SSTES losing heat at twice the expected rate, potentially due to incorrect thermal parameters from the manufacturer and the SSTES insulation being damaged or degraded. The final numerical model was validated over a 163-day period where energy was being injected into and extracted from the SSTES. It was found that the seasonal performance of the SSTES could be predicted by a conduction-only heat transfer model, and this model is suitable to be included in BPS tools.

Energy conservation performance of a solar thermal and seasonal thermal energy storage-based renewable energy convergence system for glass greenhouses

The utilization of renewable energy sources have gained significant attention in recent years for greenhouse that consumed lots of cooling and heating energy. This study investigated a solar thermal and seasonal thermal-based renewable energy convergence system. This system consists of a solar thermal system, tank- and borehole-type seasonal thermal energy storage, multi-source (i.e., air and water) heat pumps, and ground-source heat pumps. The detailed control logic of the proposed system was implemented, and the system was constructed in a test greenhouse at the Purme Yeoju Farm in South Korea. During the cooling season, the multi-source heat pumps were operated as air-source heat pumps, which showed a coefficient of performance (COP) only 0.5 less than that of the ground source heat pump. The efficiency of the solar thermal system was determined to be 36.6% throughout the investigation period, and the heat storage efficiency of the tank-type seasonal thermal energy storage was 75.7%. Consequently, the proposed system showed a COP of 2.9 during the heating season. The proposed system shows that over 70% of the operating energy can be saved, which is unachievable when using conventional electric heaters.