Search Results (234)

As the global energy sector and maritime industry transition toward carbon neutrality, Carnot batteries have emerged as a critical technology for flexible, long-duration energy management. Carnot batteries, which operate on a Power-to-Heat-to-Power principle, present a highly promising alternative to conventional electrochemical batteries. The present study provides a review of Carnot battery architectures, systematically evaluating their thermodynamic cycles, working fluids, Thermal Energy Storage media and key turbomachinery components. A comparative assessment of the current literature illustrates that system selection requires balancing round-trip efficiency, Energy Storage Density and Technology Readiness Level. According to the findings of the present study, high-temperature Brayton cycles offer robust baseline efficiencies of 60–80% whereas subcritical Rankine cycles benefit from commercial maturity and can achieve efficiencies exceeding 200% when integrated with cryogenic heat sinks like LNG. It should be clarified that efficiency values exceeding 100% represent “Apparent Round-Trip-Efficiencies (RTE)” resulting from the thermodynamic contribution of external exergy streams, such as LNG cryogenic cold, rather than standalone cycle efficiencies, which are strictly below 100%. In addition, volumetric energy density varies drastically based on the physical phase of the storage medium, scaling from under 1 kWh/m³ for unpressurized water to over 385 kWh/m³ for advanced thermochemical systems. Although most configurations currently remain in the prototyping phase, the technology holds transformative potential for the maritime sector. Carnot batteries can deliver a self-contained, zero-emission electrical power supply to cover the vessel’s electrical load requirements during harbor stays and transit within Emission Control Areas (ECAs) by dynamically capturing and storing shipboard waste heat during open sea transit. Full article

Hybridizing concentrated solar power (CSP) with residual biomass allows supercritical CO₂ (sCO₂) power cycles to deliver dispatchable low-carbon electricity, but it is unclear whether the extra equipment of the more efficient layouts adds a life-cycle burden that offsets their thermodynamic gain. This work reports what is, to the authors’ knowledge, the first unified energy, exergy, environmental and exergoenvironmental comparison of two combined sCO₂–organic Rankine cycle (ORC) configurations—a simple and a recompression Brayton layout, both with reheating, regeneration and a toluene bottoming ORC—driven by a solar tower and a coconut-shell-biomass furnace. Life-cycle impacts are quantified with Eco-indicator 99, a damage-oriented method that scores construction, operation and decommissioning damage in milli-points (mPts), and are allocated to the exergy streams through the exergoenvironmental balance. Both cycles are modelled in Python with CoolProp properties and validated against published sCO₂ analyses (efficiency deviation below 7.3%). The recompression layout reaches 54.3% thermal and 32.0% second-law efficiency and cuts the exergy destruction from 173 to 128 kW. Its larger construction impact (22.6 vs. 20.1 mPts/h) is negligible against the shared biomass reheater (429.4 mPts/h), so it is also marginally cleaner overall (459 vs. 472 mPts/h). Efficiency-oriented layout selection is therefore environmentally safe, and the remaining leverage lies in the biomass supply chain. Full article

This study evaluates, from energy, exergy, exergo-sustainability, and environmental perspectives, two combined-cycle configurations based on a supercritical CO₂ Brayton cycle coupled to an ORC: a simple reheat configuration (S-CO₂-ORC) and a recompression-reheat configuration (SRC-CO₂-ORC). Both were assessed under two thermal sources: concentrated solar power (CSP) and a hybrid biomass-CSP source using oil palm residues. Sizing was based on the cooling demand of a 130-home residential complex in Barranquilla, estimated at 152 kW through hourly simulation. The SRC-CO₂-ORC configuration delivered the best energy performance, reaching 138.38 kW and 55.34% with CSP and up to 157.28 kW and 57.66% under hybrid operation. The highest irreversibilities were concentrated in the solar field and receiver, while the thermal sources contributed more than 85% of the total carbon footprint. The lowest life-cycle impact corresponded to the SRC-CO₂-ORC-Solar configuration, at 0.0117 kg CO₂-eq/kWh, against 0.0194 kg CO₂-eq/kWh for the S-CO₂-ORC-Hybrid case. The results confirm the technical feasibility of these configurations for residential applications and reveal a clear trade-off between thermodynamic performance and minimum carbon footprint. Full article

The rapid expansion of artificial intelligence (AI) has significantly increased the power demand of high-performance data centers. This study constructs an integrated energy system based on Small Modular Reactors (SMRs). The system adopts a supercritical carbon dioxide (S-CO₂) Brayton cycle that directly supplies power for data centers. This work outlines the deep coupling of three core modules: power generation, S-CO₂ energy storage, and waste heat absorption refrigeration driven by residual heat. The design enables coordinated optimization and cascaded utilization of nuclear multi-energy flows. We first build a full thermodynamic model for the whole system, and then formulate dynamic operation scheduling strategies. A 24 h full-condition simulation is carried out. The simulation object is a 125 MW SMR with a 100 MW data center in an off-grid island operation mode. Simulation results for the key performance indicators are as follows: The system cycle thermoelectric conversion efficiency reaches 45.00%. Compared with equal-capacity SMR units equipped with traditional steam cycles, the efficiency rises by 12.5 percentage points. The overall comprehensive energy efficiency hits 82.21%, and the system exergy efficiency is 74.30%. The system achieves a completely self-sufficient power supply without grid support. Its load power deficit rate is only 1.73%. Two operation modes dominate daily system operation: surplus power charging for peak shaving accounts for 60.6% of total runtime, while energy discharging to fill power deficits equates to 38.4%. Waste heat refrigeration requires roughly 93% of the data center’s total cooling demand. This research provides a new technical framework for low-carbon and sustainable construction of next-generation high-performance data centers. The integrated system we propose provides a replicable zero-carbon off-grid energy technical route. It can serve large computing hubs constructed under China’s national “East Data, West Computing” strategy. Full article

To satisfy the electricity demands and further improve the cooling performance of scramjets, the supercritical CO₂ Brayton cycle is adopted as a promising cooling and power supplying scheme. However, with the extremely high heat flux level of MW/m², a cooling channel featuring a rectangular cross-section with non-uniform heat flow and different positions of the heated wall relative to the direction of gravity make the flow and heat transfer characteristics of supercritical CO₂ within scramjet cooling channel extremely complex. In this study, the effects of different angles of the heated wall normal direction relative to the direction of gravity (θ) on the flow and heat transfer behavior of supercritical CO₂ within a scramjet cooling channel are comprehensively investigated. The results show that the spanwise heat transfer coefficient on the heated wall decreases while on the opposite wall it increases as θ increases. Moreover, the overall heat transfer performance is insensitive to variations in θ, but the heat transfer characteristics on different walls are sensitive to variations in θ. Moreover, the cases with lower θ provide better heat transfer performance for the heated wall, which is more significant for scramjet cooling due to having the highest heat load. In detail, the averaged HTC on the HW of θ = 180 deg for G = 900 kg/(m²s) is reduced by 11.79% in comparison to that of θ = 0 deg, while it is enhanced by 18.70%, 6.39% and 6.39% for the OW, LW and RW, respectively. Full article

Micro gas turbines are small-scale systems based on the Brayton cycle and represent a viable solution for distributed generation. However, the main limitation to extending their application range is the cycle efficiency. Numerical and experimental analyses of power plants are important for evaluating the energy performance of different cycle configurations. Another issue is the formation of pollutants, including nitrogen oxide emissions. The humidified gas turbine cycle is one alternative to address these problems. Among wet cycles, the regenerative evaporative cycle offers a means to improve gas turbine efficiency. However, this configuration is less commonly discussed in the literature, which focuses more on steam injection cycles. Therefore, this paper presents an energy, exergetic, and nitrogen oxide formation analysis of an evaporative regenerative cycle for a 30 kW micro gas turbine across the gas turbine load range to define the most suitable operational system regime. The novelty of this study lies in an integrated assessment that simultaneously covers the operation of the micro gas turbine at full and part load under different conditions of water injection into the evaporator. The analyses conducted show that, for the micro turbine operating at full load, the benefits in terms of energy and pollutant formation are positive for all fractions of injected water. However, decreases in cycle performance are reported at power outputs below 19 kW compared with the dry cycle. Although nitrogen oxide formation decreases with increasing water injection, the reduction is less pronounced at lower microturbine power levels. Full article

This study presents an ideal-cycle thermodynamic analysis of an advanced compressed air energy storage (A-CAES) system with single thermal energy storage (TES) and an external heat boost. The additional heat is represented by a solar heat source, although the analysis is equally applicable to other forms of externally supplied thermal energy. Following the classical thermodynamic approach used for ideal cycles such as the Brayton, Otto and Diesel cycles, the objective is to establish analytical relationships and performance bounds for the integrated system rather than to model a specific engineering configuration. Three principal performance measures are examined: the electrical round-trip coefficient of performance (CoP), the marginal thermal coefficient of performance associated with external heat addition, and the overall second-law efficiency. Closed-form analytical expressions are derived for these quantities under idealised but still practically relevant assumptions. The analysis identifies distinct operating regimes governed by the level of external heat input and establishes analytical transition conditions between them. It is shown that external heat addition can substantially increase the round-trip coefficient of performance and lead to high marginal heat-utilisation effectiveness. A rigorous upper bound on the second-law efficiency is also obtained from a complete-cycle exergy analysis, demonstrating consistency with the laws of thermodynamics. The results provide analytical insight into the fundamental thermodynamic structure of solar-assisted A-CAES systems and establish performance bounds that are independent of any particular engineering implementation. Full article

The residential sector accounts for a significant portion of global energy demand, which can be met through sustainable alternatives such as solar energy. This study evaluated the energy, exergy, environmental, and exergy-sustainability performance of three waste heat recovery configurations (double-loop organic Rankine cycle—DORC, Kalina cycle—KC, and organic Rankine cycle—ORC) coupled to a supercritical CO₂ Brayton cycle with intercooling and reheating, designed to meet the demand of a residential complex of 120 homes in the Colombian Caribbean region, built with four different materials, using a concentrated solar power tower as the heat source. Mass, energy, and exergy balances were performed, along with a life cycle analysis, sizing the systems to supply a cooling load of 133 kW. The results show that the three configurations meet the required demand, with energy efficiencies above 50%: sCO₂-DORC (51.7%), sCO₂-ORC (51.61%), and sCO₂-KC (51.32%), with a maximum exergy efficiency for sCO₂-DORC (24.3%). The environmental analysis indicates that the construction phase accounts for more than 95% of total emissions. Overall, the results confirm the viability of these configurations for residential applications, promoting the integration of renewable energies and supporting the regional energy transition. Full article

Detonation-based combustion systems for application in gas turbines (GTs) have received growing attention in recent decades. Such a technology leads to higher thermodynamic cycle efficiency compared to the conventional deflagrative solution as a result of pressure rise occurring during the heat addition process. This study aims to implement pressure gain combustion (PGC) into a thermodynamic cycle where the main compressor is operated at a lower pressure ratio compared to the Brayton–Joule cycle. In detail, this study focuses on the impact of the secondary air system (SAS) compressor, which is necessary to correctly feed the blade cooling circuits with adequate pressure as well as to deliver high-pressure air for cooling the PGC system. A parametric analysis based on different amounts of cooling air to the PGC system is proposed and discussed. In detail, the power demand by the SAS compressor can be as high as 5–6% of the net PGC GT power output, with maximum demands calculated in the range from 16 to 22 MW for a 335 MW F-class gas turbine. These figures are significant because the higher they are, the greater the risk of reducing the performance advantage introduced by the pressure gain combustion. In addition, the effects of SAS compressor efficiency are investigated and a preliminary assessment of both size and rotational speed of the SAS compressor is proposed as well. Full article

The growing share of intermittent renewable electricity has increased the need for long-duration storage in industrial energy systems. Meanwhile, many industrial processes still release recoverable low-grade waste heat. Introducing this heat into pumped thermal energy storage (PTES) can improve thermal integration, but industrial waste heat is often unsteady, and its temperature and mass flow fluctuations may disturb the charging process. This study investigates an air-based reverse Brayton PTES system assisted by an industrial hot-water waste heat stream of approximately 100 °C. A dynamic model was developed in Simulink/Simscape. The shaft speed is fixed at 3000 rpm, and a PID controller regulates the molten-salt flow rate to maintain the thermal storage temperature. The results show that increasing the waste heat temperature from 95 °C to 105 °C mainly changes the charging-side heat distribution. The waste heat utilization power increases from 36.0 MW to 37.9 MW, while the regenerator power decreases from 126.8 MW to 122.0 MW. The thermal storage power increases slightly from 117.0 MW to 119.0 MW, with the mechanical input fixed at 81.0 MW. The influence of waste heat temperature is concentrated near the low-temperature heat exchanger, regenerator, and turbine outlet. Under dynamic disturbances, faster temperature ramps increase short-term deviations, but the PID-based molten-salt flow regulation keeps the storage temperature close to 550 °C, indicating that the proposed control strategy can suppress moderate thermal disturbances during charging. When waste heat temperature and mass flow rate vary together, same-direction changes strengthen the disturbance, whereas opposite-direction changes partly offset it. These results clarify the disturbance propagation mechanism of fluctuating industrial waste heat in the PTES charging loop and provide a basis for the dynamic design and temperature-control strategy of waste-heat-assisted PTES systems. Full article

Decarbonizing industrial energy consumption is critical for global sustainability. This study evaluates renewable energy alternatives to replace fossil-fuel power generation at an oil and gas facility in Khurais, KSA. A comparative thermodynamic and economic assessment was performed between a photovoltaic (PV) array and a parabolic trough collector (PTC) integrated with a Brayton cycle (BC) and a bottoming organic Rankine cycle (RC). The PTC-BC-RC model includes multi-generation capabilities for electricity, process hot water, and hydrogen via a PEM electrolyzer. The baseline PTC-BC-RC system generates up to 118.1 MW with a maximum thermal efficiency of 36.57%. The PEM electrolyzer utilizes 2% of the generated power to produce hydrogen at 0.0152 kg/s. Economically, the recuperated CSP system offsets its higher initial capital costs through diverse revenue streams (power, heat, and hydrogen), achieving a payback period of 5.13 years, significantly outperforming the PV system’s 6.80 years. Both configurations mitigate annual emissions by 747,000 tons of CO₂, 103.4 tons of NO_x, and 3.72 tons of SO₂. Despite regional limitations such as dust and water scarcity, the multi-generation PTC-BC-RC system proves economically and thermodynamically superior to the standalone PV system, offering a highly effective decarbonization strategy for industrial facilities in arid, high-irradiance zones. Full article

Efficiency improvements in gas turbines have been realized in recent decades by raising the turbine inlet temperature. This work devotes attention to pressure-gain combustion (PGC), which is a technology capable of yielding the same time-averaged combustor outlet temperature as conventional Brayton–Joule cycles but at a higher pressure. Here, PGC is implemented in a thermodynamic cycle wherein the compression system operates at a lower pressure ratio compared to the reference Brayton–Joule cycle. Focusing on E-, F- and H-class gas turbines, representative of three different technologies, the possible PGC advantages in both simple- and combined-cycle modes are investigated by means of in-house simulation code. Specifically, this work includes the energy penalty related to the PGC system cooling in the cycle analysis. In detail, the effects of different coolant amounts on the PGC system, as well as the lower efficiency at the first expansion stage compared to conventional gas turbine systems, are analyzed. Among the three classes of gas turbines, E is the one wherein the advantages are more significant, with ultimate efficiency values in simple-cycle mode calculated in the range of 38% to 41%. The higher the gas turbine technology and power class, the lower the benefit, and current H-class gas turbines already start from a higher efficiency level. Anyway, focusing on the latter, performance improvements for the PGC combined cycle seem to be possible, with efficiency greater than 65%, exceeding the current state-of-the-art systems. Full article

Renewable energy sources, such as solar and biomass, represent sustainable alternatives to meet the growing energy demands of the residential sector. This study evaluated the energy, exergy, and environmental performance of two Brayton configurations using supercritical carbon dioxide: a recompression cycle (SRC) and a recompression cycle with intercooling in the main compression (SMC), both coupled to a dual-loop organic Rankine cycle (DORC) and powered by a hybrid solar-biomass thermal system. Mass, energy, and exergy balances were developed, and a life cycle assessment was performed to quantify the environmental impact. The systems were designed to cover a cooling load of 130 kW corresponding to 200 dwellings constructed with Asbestos cement in the Colombian Caribbean region. The results show that both configurations meet the required demand; the SMC-DORC cycle operates at 650 °C, while the SRC-DORC requires 750 °C. The SRC-DORC exhibits higher thermal efficiency (53.24%), while the SMC-DORC achieves a slightly higher exergy efficiency (28.15%). Environmental analysis shows that the construction phase accounts for the majority of the total impact, exceeding 95% of emissions. Overall, both configurations are technically feasible, with the SRC-DORC standing out for its balance between efficiency and environmental impact. Full article

The development of efficient and economically viable energy storage technologies is key to the integration of renewable energies. This study evaluates the thermo-economic performance of hydrocarbons as working fluids in PTES systems based on a simple Brayton cycle (SBC). Different hydrocarbon mixtures are analyzed to determine their impact on efficiency and costs, identifying optimal operating conditions and combinations that improve system performance and viability. The objective is to identify the optimal candidate and operating conditions for enhanced cost-effectiveness. A multivariable optimization was performed using a validated thermodynamic model, integrated with an economic evaluation framework. Key decision variables included pressure ratios, turbine inlet temperatures, and heat exchanger performance parameters, while several sCO_2–hydrocarbon mixtures were evaluated as working fluids. Energy and exergy analyses were coupled with component-level cost correlations to determine round-trip efficiency, specific investment cost, and levelized cost of storage. The findings indicate that the CO₂/C₂H₆ (60/40) mixture provides the best overall performance, achieving a round-trip efficiency of 54.38% and a levelized cost of storage of 137.1 $/MWh, outperforming pure CO₂. Fluid selection exerts a substantial influence on both thermodynamic and economic indicators, with performance exhibiting a pronounced dependency on critical temperature, molecular complexity, and operating pressure levels. Sensitivity analyses indicate that improvements in heat exchanger effectiveness and turbomachinery efficiency yield substantial reductions in total system cost. The findings indicate that the appropriate alignment of hydrocarbon properties with system design parameters can significantly enhance the feasibility of PTES, offering a technically viable and economically competitive pathway for large-scale energy storage applications. Full article

The Composite Cycle Engine (CCE) enhances the conventional Joule/Brayton cycle by replacing the high-pressure compressor with a high-quality piston-based gas generator that enables extremely high compression, combustion, and expansion of the working fluid before entering the classic Joule burner. This piston-based topping cycle unlocks much more efficient fuel utilization. This paper studies a CCE concept featuring a system of free double piston (FDP) units for a potential long-range (LR) application in 2045, benchmarked against an advanced turbofan engine representative of the same time frame. In-house-developed simulation tools for the piston system and the overall power plant, as well as aircraft non-linear trade factor analysis, are used for different levels of conceptual assessment. First, the cooling demand inside the FDP system is determined. An engine cycle parametric study is then performed for the design point top-of-climb (ToC). Off-design performance is further studied, demonstrating a 9.3% improvement in thrust-specific fuel consumption (TSFC) in cruise relative to the baseline engine. After incorporating the engine weight and nacelle geometry effects, the engine reaches a total mission fuel burn reduction of around 14.7% compared to the baseline engine. The concept evaluation shows the fuel burn potential of the CCE in the future LR aviation sector and lays the foundation for further climate impact analysis. Full article