High-temperature thermal energy storage (TES) is increasingly regarded as essential for sustainable energy systems, enabling the decoupling of supply and demand in renewable-heavy scenarios where flexibility and reliability are critical. This work builds on previous authors work and presents a novel double-layered packed bed TES prototype and its experimental assessment. The prototype, with 35 kWh capacity, operates between 20 °C and 600 °C at ambient pressure. Its key feature is two coaxial particle layers, whose sizes can be independently adjusted to test multiple configurations, offering unique flexibility for performance evaluation. Experiments explore variations in charging/discharging mass flow rates, operating temperatures, and particle/layer sizes. Temperature sensors embedded within the bed capture detailed thermocline development. Performance is quantified through key performance indicators and dimensionless parameters. Results show robust and repeatable behavior, with efficiencies around 90% and consistently high temperature uniformity across the bed. The pressure drop remains minimal, below 1 mbar, while particle size has a strong influence: larger particles reduce pressure drop, whereas smaller ones enhance thermal performance. Nevertheless, under the tested operating conditions, the discharge temperature exhibits a decreasing profile. Overall, this study demonstrates the potential of radial-flow packed bed concepts, while also showing that certain coaxial layering configurations can reduce pressure drop by about 30% without compromising thermal performance, maintaining efficiencies near 90%.

High temperature heat pumps and thermal energy storage are key technologies for industrial decarbonization. An effective integration of these technologies can provide flexible and reliable process heat whilst facilitating further uptake of renewable energy sources in the grid. This work presents a comprehensive techno-economic assessment of an integrated system based on a novel high temperature Stirling heat pump coupled with an innovative latent thermal energy storage to deliver process heat at 200 °C. Three different layouts were investigated: a single Stirling heat pump upgrading waste heat, a single Stirling heat pump upgrading ambient heat, and a two-stage vapor compression heat pump coupled with a Stirling heat pump for upgrading ambient heat. The systems are studied with electricity prices from 2023 from four electricity markets: Germany, Greece, Norway, and Spain. Operational dispatch strategies and system sizing are identified for optimal techno-economic performance. The main performance indicators investigated are the levelized cost of heat, CO2 emissions, operational expenditures, and cost savings compared to traditional fossil-fuel and electric boilers. The results highlight that the levelized cost of heat can be reduced by 3–12 % in Germany and Spain while generating operational cost savings of 30–40 %. CO2 emissions can be reduced by 24–63 % when upgrading waste heat. In Norway, the levelized cost of heat can be reduced by 35–45 % while generating operational cost savings of 50–70 % against traditional gas boilers. In Greece, the levelized cost of heat can be reduced by 1 % in the Mid Scenario.

This work presents a numerical investigation of the thermo-hydraulic performance of a tube-bundle cavity (TB)receiver for parabolic trough collectors (PTCs). The proposed receiver replaces the conventional single absorbertube with multiple smaller tubes arranged in a circular bundle, forming a linear cavity that improves solar absorptionand reduces temperature non-uniformities on the absorber surface. A three-dimensional CFD model isdeveloped under real-scale operating conditions to assess several TB configurations through a two-stage optimizationprocedure. The designs are evaluated using thermal efficiency, pressure drop, and overall efficiencymetrics. The results indicate that, despite higher flow resistance, TB receivers significantly enhance thermalperformance compared to the conventional design. Hotspot temperature increases are reduced by up to 77%,while temperature uniformity increases by approximately 23%. Among the investigated configurations, the 12-tube design provides the best thermo-hydraulic compromise, achieving a maximum overall efficiency of 0.76 atan inlet temperature of 450 K, corresponding to a 7% improvement over the standard receiver. Additional analysesover inlet temperatures ranging from 400 to 550 K confirm the robustness of the optimized TB configurationin mitigating hotspot formation while maintaining superior overall performance.

This study investigates the techno-economic and techno-environmental performance of photovoltaic (PV) solar systems coupled with battery energy storage systems (BESS) in a Swedish context. The research uses mixed-integer linear programming (MILP) to optimise the dispatch strategy, minimising both operational costs and CO2eq emissions. By analysing grid signals, including electricity price and carbon intensity, the study determines the optimal size and operation of PV-BESS. The base case in Sweden was further examined by comparing the system with Italy and Poland, and by testing it with different load demand profiles. Italy and Poland were chosen due to their higher variability in grid price and carbon footprint, respectively, as well as more favourable solar conditions. The industrial and industrial shift profiles were chosen to assess the impact of load profiles with less variability compared to the base case residential profile. The key findings reveal distinct differences between economic and environmental optimisation, impacting system performance and highlighting the need for a balanced approach. Local conditions, such as grid signal volatility and solar PV production, are shown to significantly influence optimal system configurations. In Sweden, the economic approach led to higher system utilisation due to greater price volatility, while the environmental approach prioritised lower emissions. Additionally, the trade-offs between economic and environmental optimisation can lead to cost/environmental footprint increases between 25% and up to several times higher (up to 300 %). The study also finds that reducing the levelised cost of energy (LCOE) or levelised carbon footprint (LCO2eq) from the investor perspective may not always translate into significant end-user benefits. This further highlights the importance of including various stakeholder perspectives in the analysis, especially in the context of decision support. Sensitivity analysis indicates that oversizing the PV system leads to a rapid increase in costs and emissions. The addition of BESS can justify this increase by scaling the Renewable Energy Self-Sufficiency (RESS) value. Furthermore, there are diminishing returns for oversizing the battery. This research is relevant for various stakeholders, including project developers, policymakers, and researchers involved in renewable energy integration. Future research could further refine optimisation strategies for PV-BESS systems by delving deeper into specific aspects such as grid signal analysis and diverse end-of-life (EoL) pathways.

Large-scale energy storage is essential for integrating increasing shares of renewable energy into power grids. Pumped Thermal Energy Storage (PTES), particularly Thermally Integrated PTES (TI-PTES), offers advantages such as long lifespan, fast response, and flexibility, along with external heat source integration. Traditionally, PTES dispatch studies focus on maximizing profitability, which often leads to energy storage from CO2-emitting sources rather than purely from renewables. This study investigates the optimal dispatch strategy for a supercritical carbon dioxide (sCO2) thermal cycle-based TI-PTES across various European markets using a Mixed Integer Linear Programming (MILP) model. The primary objective is to evaluate the economics of TI-PTES optimized for CO2 emission minimization and compare it with conventional profit-maximizing dispatch strategies based on electricity market prices.For selected EU energy markets, key indicators such as payback period, net present value (NPV), levelized cost of electricity (LCOE), and displaced CO2 emissions are analyzed for price-based vs. CO2 emission-based dispatch to assess the financial viability and environmental impact of TI-PTES. Study shows annual round-trip efficiency of 105 % for Finland and 101 % for Germany, as compared to the 112 % of the electric RTE set for the model. The payback periods for only Germany comes out to be achievable during the span of the plant life of 25 years under the current market price scenarios. However, with increased volatility from 20 to 100 %, the payback period for the same market can decrease 20–60 % of the current value. Similarly, the study further proposes a novel hybrid dispatch strategy that incorporates both economic profitability and emission minimization by assigning appropriate weights to each objective. The optimal weighting varies for each energy market to achieve the most effective results. The hybrid dispatch approach positions TI-PTES as both an economically and environmentally viable solution for energy storage and grid integration.

Thermal energy storage is emerging as a sustainable and innovative solution for industrial heat decarbonization. Packed bed systems offer low costs, high energy density, and efficiency for medium- and high-temperature applications. This study evaluates the performance of various packed bed configurations using commercial ternary salts and silicone oil as heat transfer fluids, benchmarked against solar salt. Copper slags, steel slags, and bauxite are selected as suitable solid media, and the combined effects of the material properties in each system's technical performance are analyzed using computational fluid dynamics simulations. A numerical model is developed in COMSOL Multiphysics, using an axial-flow packed bed system as the base design, and all configurations are simulated. Key performance indicators such as round-trip efficiency, thermocline thickness and material cost evaluate the findings. The study reveals that ternary salt packed beds exhibit significant flow non-uniformities under specific conditions, driven by ‘viscous fingering’, leading to round-trip efficiencies below 80 %. Silicone oil achieves low thermocline thickness, round-trip efficiencies near 90 %, and costs of ∼€12/kWh with metal slag fillers. Steel slags consistently yield higher efficiencies, while copper slag offers greater energy density, reducing storage costs compared to bauxite. Sensitivity analyses are performed for the ternary salt systems in order to identify the boundaries of ‘viscous fingering’ and are benchmarked against solar salt. In comparison, solar salt demonstrates the lowest material costs (∼€3/kWh) and round-trip efficiencies near 90 %. This work provides relevant insights for detailed thermocline TES design when considering non-conventional materials, enabling reducing costs whilst ensuring relevant efficiencies.

Decarbonization policies have significantly increased the adoption of plug-in electric vehicles (PEVs) worldwide. This paper develops and applies a probabilistic method for assessing large-scale integration of PEVs in a real low voltage distribution system (DS) in Stockholm County, Sweden. The framework employs Monte Carlo simulations to capture uncertainties in driver behaviors, daily distances, charging start times, and vehicle allocation. Its key contributions are: (i) a replicable data-driven Monte Carlo framework that merges DS operator (DSO) load data with travel habit statistics, (ii) realistic charging-profile generation, (iii) demonstrate that adding price signals plus a network constraint almost doubles hosting capacity and cuts user costs, and (iv) a systematic comparison of uncontrolled versus controlled charging that clarifies technical-economic trade-offs. The analysis considers PEV penetration levels (Pls)—defined as the percentage of customer units (CUs) with a PEV among all CUs with permanent access to a passenger vehicle—up to 100 %. Key performance indicators, analyzed at the 95th percentile to represent near-worst-case outcomes, include voltage profiles, transformer and line loading, aggregated peak power, technical losses, and hosting capacity. Uncontrolled charging raises peak demand, causing voltage and overload violations that cap hosting capacity at Pl 27 %. Adding price signals with a peak demand cap lifts capacity to Pl 49 %, halves overloads, and lowers charging costs by about 10 %. Night-time charging suffices up to Pl 49 %; above Pl 75 %, morning charging is needed to keep power quality within limits. The method is broadly replicable and offers actionable guidance for municipalities, DSOs, and policymakers seeking to ensure a sustainable and cost-effective transition toward electrified transportation while maintaining reliable DS operation.

The ambitious goal of achieving Net-Zero energy targets in European countries by 2050 necessitates a significant increase in the penetration of renewable energy in the electrical grid. This transition is essential to decarbonising key sectors that contribute to greenhouse gas emissions. However, the rapid growth of renewable power generation presents challenges to maintaining grid flexibility, as current energy storage technologies, such as electrochemical batteries, face scalability limitations due to high costs associated with extended storage durations and increased capacity. In this context, there is a critical need for cost-effective, long-duration energy storage technologies to ensure a smooth transition to a Net-Zero future. This paper investigates the discharging performance of a novel Molten Salt/Slags Packed Bed Thermal Energy Storage (TES) technology within a Power-to-Heat-to-Power (P2H2P) Carnot Battery concept, leveraging supercritical CO2 Brayton cycles. A Computational Fluid Dynamics (CFD) model of the thermocline-based TES technology is developed and validated against experimental data from the literature. The validated model is then employed to assess the discharging performance of the TES tank under the boundary conditions dictated by the P2H2P/CB concept. A key focus of this study is monitoring the thermocline thickness and its impact on the discharging outflow temperature, which typically declines after a specific discharging duration. The TES system demonstrates an estimated Round-Trip Efficiency (RTE) of up to 90%. Moreover, this TES technology incorporates industrial waste as filler materials, specifically steel slags, which could be beneficial in regard of increased energy storage density and potentially cost reduction.

Decarbonization policies have accelerated global adoption of plug-in electric vehicles (PEVs), presenting challenges for power distribution systems (DS). This study assesses the grid impacts of large-scale PEV and distributed photovoltaic (PV) integration using a real-world DS case from Stockholm County, Sweden. A Monte Carlo (MC) simulation framework models the stochastic, uncontrolled charging behavior of PEVs based on real travel patterns, considering both residential and commercial charging, at penetration levels up to 100%. To demonstrate the framework’s application, a real case study explores how solar PV can mitigate PEV-induced grid impact and enhance hosting capacity across seasons. Results show limited synergy during winter due to low solar availability, with a 2% voltage improvement during summer peak hours. The methodology provides valuable insights for municipalities, DS operators (DSOs), and policymakers planning the sustainable integration of electric mobility and decentralized renewable energy into existing grids.

Integrating thermal energy storage (TES) systems with high-temperature heat pumps (HTHPs) combines two highly efficient technologies to develop a robust energy storage and flexible heat supply system. This integration package is predominantly valuable for industrial processes, renewable energy storage and supporting the grid where a consistent and intermittent demand for high-temperature heat (above 300 degrees C) exists. Stirling cycle-based heat pumps offer market readiness for high temperature applications with present capabilities attain above 250 degrees C with ongoing developmental campaigns to further increase the temperature thresholds. To achieve greater productivity in thermal storage processes, higher magnitudes of heat transfer temperature are preferred, wherein the heat transfer fluids such as molten salt (MS) are favoured. Molten salts TES is a mature and effective technology for storing large amounts of thermal energy for the emerging high temperature applications in concentrating solar power plants (CSP). In order to facilitate a sustainable operation of a seamlessly integrated TES and HTHP system, development of robust heat exchangers is key to withstand the high temperatures and maintain an effective heat transfer performance of the system. This study aims at optimizing the design of a Stirling cycle based HTHP integrated compact shell and tube heat exchanger that operates between pressurised helium gas from the HTHP side and a ternary molten salt from the TES side. A two-dimensional computational model is developed in ANSYS Fluent with a triangular tube pattern that enables the flow of pressurised helium gas while MS flows around the shell side. Numerical results are performed based on a geometric design optimization to identify the optimal values that influence the fluid and heat transfer characteristics of MS in a shell and tube heat exchangers with a heating capacity of up to 100 kW. A shell side heat transfer coefficient (hsh) and pressure drop (Delta P) are the key parameters of interest to analyse the heat exchanger characteristics with a primary focus on the shell side flow.