Search Results (93)

The contributions of Thermodynamics to Economics have been masterfully pioneered by P. A. Samuelson in his Foundations of Economic Analysis, adapting the Le Châtelier Principle to relate changes in economic variables. Recent contributions have been given, including the economic counterparts of energy, temperature, reversibility, and irreversibility, the Carnot engine, entropy, entropy generation, and the four Laws of Thermodynamics. Starting from them, toward a more efficient (more perfect) economy, the present work aims at (i) showing the contribution of negotiation to a more perfect economy; (ii) proposing endoreversible economic processes, and evaluating their efficiency at maximum merchandise wealth delivery; (iii) proposing the dynamic economic processes’ analysis based on the Economics analogue of specific heat, closely related to the demand elasticity coefficient; (iv) exploring ways to maximize merchandise wealth delivery instead of maximizing merchandise economic entropy generation (financial value generation) in dynamic processes; and (v) defining and evaluating the Economics analogue of exergy, the maximum potential of economic systems to deliver merchandise wealth. Full article

Continuous particle exchange thermal machines require no time-dependent driving, can be realised in solid-state electronic devices, and can be miniaturised to nanometre scale. Quantum dots, providing a narrow energy filter and allowing to manipulate particle flow between the hot and cold reservoirs are at the heart of such devices. It has been theoretically shown that through mitigating passive heat flow, Carnot efficiency can be approached arbitrarily closely in a quantum dot heat engine, and experimentally, values of 0.7${\eta }_C$ have been reached. However, for practical applications, other parameters of a thermal machine, such as maximum power, efficiency at maximum power, and noise—stability of the power output or heat extraction—take precedence over maximising efficiency. We explore the effect of the internal microscopic dynamics of a quantum dot on these quantities and demonstrate that its performance as a thermal machine depends on few parameters—the overall conductance and three inherent asymmetries of the dynamics: entropy difference between the charge states, tunnel coupling asymmetry, and the degree of detailed balance breaking. These parameters act as a guide to engineering the quantum states of the quantum dot, allowing to optimise its performance beyond that of the simplest case of a two-fold spin-degenerate transmission level. Full article

This study presents a comprehensive dynamic system analysis of air-based Brayton batteries for the coupled generation of electricity, heat, and cooling. Building upon a previously published structural concept study, the most promising system architectures were modeled and evaluated using quasi-stationary simulations with dynamically designed thermal energy storage (TES) in Ebsilon Professional^®. The results show round-trip efficiencies (RTEs) of up to 50% for pure electricity generation and round-trip utilizations (RTUs) exceeding 85% for combined heat and power. Integration of waste heat further increases RTU to more than 100%, albeit at the expense of electrical efficiency. Dynamic simulations demonstrate stable operation with load gradients up to 2 MW min⁻¹, highlighting suitability for flexible industrial and grid applications. Regenerator-based TES exhibits the most favorable trade-off between efficiency and cost, while hybrid configurations of solid and liquid media offer additional optimization potential. The estimated investment costs range between 200 and 800 EUR/kWh_el, comparable to other large-scale Carnot battery systems. The findings provide a validated framework for the techno-economic design and control of next-generation Brayton battery systems and lay the foundation for experimental validation and pilot-scale implementation. Full article

Carnot Batteries with thermal integration stand as one of the most promising approaches to tackling contemporary global energy problems. Currently, research on Carnot Battery systems utilizing the ocean thermal gradient is still in its early stages. This paper establishes a holistic thermo-economic model to assess the system’s performance. Through working fluid screening and subsequent multi-objective optimization, this study identifies the optimal working fluid and clarifies the system’s thermal economy at the optimal design point. With round-trip efficiency and total cost as metrics, a sensitivity analysis identified key parameter effects on the system. This was followed by a multi-objective optimization, where the TOPSIS method selected the optimal solution. It was found that, when Ammonia and R1234yf were used as the working fluids in the RC and ORC sub-cycles, respectively, the system can achieve peak performances of 71.79% round-trip efficiency and 36.24% exergy efficiency. Moreover, the RC evaporation temperature exerts the most significant influence on the overall thermodynamic performance. Multi-objective optimization successfully identified a balanced thermo-economic design, yielding an optimal solution with a round-trip efficiency of 65.30% at a total cost of USD 65.90 M. These results offer critical insights for the design and optimization of this promising ocean thermal-powered Carnot Battery system. Full article

To assess multi-energy complementarity and commercial development status in thermodynamic energy storage systems, this review systematically examines compressed air energy storage (CAES), compressed CO₂ energy storage (CCES), and Carnot battery (CB), focusing on principles, engineering demonstrations, and thermal integration. Their ability to integrate external heat, conduct combined cooling, heating and power (CCHP), or achieve high round-trip efficiency (RTE) through different pathway positions them as critical enablers for achieving net-zero emissions. Over 240 research articles retrieved from Web of Science and other databases, supplemented by publicly available reports published between 2020 and 2025, were systematically analyzed and synthesized. Current technologies demonstrate evolution from single-function storage to multi-energy hubs, with RTEs reaching 75% (CAES/CCES) and 64% (CB). Thermal integration significantly enhances RTEs. The CCES features a 100 MW/1000 MWh demonstration facility, concurrently necessitating accelerated distributed applications with high efficiency (>70%) and energy density (>50 kWh/m³). All three enable grid flexibility (China’s CAES network), industrial decarbonization (CCES carbon–energy depositories), and thermal integration (CB-based CCHP). These systems require >600 °C compressors and AI-optimized thermal management (CAES), high-pressure turbines and carbon–energy coupling (CCES), as well as scenario-specific selection and equipment reliability validation (CB) to achieve the targets of the Paris Agreement. Full article

The article discusses the current challenges facing the energy sector in the context of climate policy, technological transformation, and the urgent need to increase energy efficiency while reducing greenhouse gas emissions. Modern thermal energy conversion technologies are analyzed, including supercritical steam and gas–steam cycles, as well as distributed systems using renewable fuels and microturbines. Particular attention is given to innovative systems with isothermal expansion, which theoretically allow operation close to the efficiency limit defined by the Carnot cycle. The study presents calculation results for conventional systems (steam, gas with regeneration, and Organic Rankine Cycle) and proposes a novel isothermal air turbine cycle. In a combined gas–steam configuration, the proposed cycle achieved an efficiency exceeding 43% at a relatively low heat source temperature of 700 K, clearly outperforming conventional steam and ORC systems under the same thermal conditions. The use of a simple working medium (air), combined with the potential for integration with renewable energy sources, makes this concept a promising and viable alternative to traditional Rankine and Brayton cycles in thermally constrained applications. Full article

In a world increasingly dependent on digital computers, understanding the relationship between information theory and thermodynamics is essential. A recent attempt to address this issue was made by A. De Vos who, using a reversible model within the framework of finite-time thermodynamics, derived Carnot’s law, Landauer’s principle, Ohm’s law, and even Moore’s law. Following De Vos et al., this paper first recovers the efficiency of Curzon and Ahlborn, and then establishes the so-called endoreversible Landauer principle for a traditional computer gate, assuming the gate operates in the Maximum Power regime. However, two other regimes are particularly important: the Omega function and the Efficient Power function. By considering these, we obtain the corresponding thermodynamic efficiencies and compare them against that of the Maximum Power regime. Full article

In celebration of 50 years of the endoreversible Carnot-like heat engine, this work aims to link the thermodynamic success of the irreversible Carnot-like heat engine with the stability dynamics of the engine. This region of success is defined by two extreme configurations in the interaction between heat reservoirs and the working fluid. The first corresponds to a fully reversible limit, and the second one is the fully dissipative limit; in between both limits, the heat exchange between reservoirs and working fluid produces irreversibilities and entropy generation. The distance between these two extremal configurations is minimized, independently of the chosen metric, in the state where the efficiency is half the Carnot efficiency. This boundary encloses the region where irreversibilities dominate or the reversible behavior dominates (region of success). A general stability dynamics is proposed based on the endoreversible nature of the model and the operation parameter in charge of defining the operation regime. For this purpose, the maximum ecological and maximum Omega regimes are considered. The results show that for single perturbations, the dynamics rapidly directs the system towards the success region, and under random perturbations producing stochastic trajectories, the system remains always in this region. The results are contrasted with the case in which no restitution dynamics exist. It is shown that stability allows the system to depart from the original steady state to other states that enhance the system’s performance, which could favor the evolution and specialization of systems in nature and in artificial devices. Full article

Atmospheric climate science lacks the capacity to integrate thermodynamics with the gravitational potential of air in a classical quantum theory. To what extent can we identify Carnot’s ideal heat engine cycle in reversible isothermal and isentropic phases between dual temperatures partitioning heat flow with coupled work processes in the atmosphere? Using statistical action mechanics to describe Carnot’s cycle, the maximum rate of work possible can be integrated for the working gases as equal to variations in the absolute Gibbs energy, estimated as sustaining field quanta consistent with Carnot’s definition of heat as caloric. His treatise of 1824 even gave equations expressing work potential as a function of differences in temperature and the logarithm of the change in density and volume. Second, Carnot’s mechanical principle of cooling caused by gas dilation or warming by compression can be applied to tropospheric heat–work cycles in anticyclones and cyclones. Third, the virial theorem of Lagrange and Clausius based on least action predicts a more accurate temperature gradient with altitude near 6.5–6.9 °C per km, requiring that the Gibbs rotational quantum energies of gas molecules exchange reversibly with gravitational potential. This predicts a diminished role for the radiative transfer of energy from the atmosphere to the surface, in contrast to the Trenberth global radiative budget of ≈330 watts per square metre as downwelling radiation. The spectral absorptivity of greenhouse gas for surface radiation into the troposphere enables thermal recycling, sustaining air masses in Lagrangian action. This obviates the current paradigm of cooling with altitude by adiabatic expansion. The virial-action theorem must also control non-reversible heat–work Carnot cycles, with turbulent friction raising the surface temperature. Dissipative surface warming raises the surface pressure by heating, sustaining the weight of the atmosphere to varying altitudes according to latitude and seasonal angles of insolation. New predictions for experimental testing are now emerging from this virial-action hypothesis for climate, linking vortical energy potential with convective and turbulent exchanges of work and heat, proposed as the efficient cause setting the thermal temperature of surface materials. Full article

Spain’s energy transition poses the dual challenge of managing renewable curtailment and enhancing the competitiveness of concentrated solar power (CSP) technologies. This study evaluates the suitability of replacing molten salts with solid particles for energy storage and, additionally, explores the storage of surplus electricity from grid in Carnot batteries. Four scenarios were analyzed using a Gemasolar-type plant model: each storage medium was studied with and without the integration of curtailed electricity. The solar field was modeled with SAM (System Advisor Model), while curtailment data from Red Eléctrica de España (2016–2021) quantified the available surplus. Results show that solid particles lead to 7.4% higher annual electricity production compared to molten salts, mainly due to improved power cycle efficiency. The integration of curtailment increased output further, with the solid particle Carnot battery scenario achieving the highest performance (up to 19.0% sun-to-electricity efficiency and 69.7% capacity factor). However, round-trip efficiency for curtailment storage was limited (~25–27%), and although solid particles showed lower LCOE (levelized cost of energy) than salts (192 vs. 211 USD/MWh), the Carnot battery increased costs. These findings suggest that while solid particles offer clear advantages, the economic viability of Carnot batteries remains constrained by current cost and operational limitations. Full article

Heat pumps are widely regarded as a key technology for sustainable heating, offering a pathway to significantly reduce fossil fuel dependency and combat the climate crisis. However, replacing individual gas boilers with heat pumps in multi-unit residential buildings remains a substantial challenge despite its immense potential to lower urban greenhouse gas emissions. To address this, the following paper describes the development of a compact, modular heat pump system designed to replace conventional gas boilers, focusing on the building and testing of a prototype for such a modular heat pump system. The prototype supports multiple functionalities, including space heating, cooling, and domestic hot water production. The performance advantages of two different compressor technologies were exploited to optimize the efficiency of the complete system and the pressure lifts associated with applications for heating and domestic hot water production. Thus, measurements were conducted across a range of operating points, comparing different heat pump module types. In the case of the piston compressor module, the Carnot efficiency was in the range of 47.2% to 50.4%. The total isentropic efficiency for floor heating and domestic hot water production was above 0.45 for both piston and rotary compressors. Full article

This author is not a philosopher nor a historian of science, but an engineering thermodynamicist. In that regard, and in addition to various philosophical “why and how” treatises and existing historical analyses, the physical and logical “what it is” reflections, as sequential Key Points, where a key Sadi Carnot reasoning infers the next one, along with novel contributions and original generalizations, are presented. We need to keep in mind that in Sadi Carnot’s time (early 1800s), steam engines were inefficient (below 5%, so the heat in and out was comparable within experimental uncertainty, as if caloric were conserved), the conservation of caloric flourished (might be a fortunate misconception leading to the critical analogy with the waterwheel), and many critical thermal concepts, including the conservation of energy (The First Law), were not even established. If Clausius and Kelvin earned the title “Fathers of thermodynamics”, then Sadi Carnot was ‘the ingenious’ “Forefather of thermodynamics-to-become”. Full article

After a brief review of Carnot’s everlasting contributions to the foundations of thermodynamics, we critically examine the consequences of the Carnot theorem, which leaves behind some lingering questions and confusion that persist even today. What is the one significant aspect of the Carnot cycle that leads to this theorem? When does the working substance play an important role for an engine and what is its correlation with the protocol of operational details? Do all reversible engines working between the same two temperatures have the same maximum efficiency of the Carnot engine as Fermi has suggested? Are all heat engines equivalent to a Carnot engine in disguise? Our new perspective allows for the clarification of these questions with a positive answer for the last question. Recognizing that Carnot eventually abandoned the caloric theory, we use a result by Carnot and simple dimensional analysis to show how the first law, the concept of entropy, and the efficiency of the Carnot engine could have been germinated by Carnot in his time. This then demonstrates that Carnot had good understanding of entropy before its invention by Clausius. We suggest that both should be credited with inventing entropy by calling it Carnot–Clausius entropy. We also clarify some fundamental misconceptions plaguing reversible regenerators and their irreversible replacement by heat exchangers in the field. Full article

To fully recover abundant waste heat and reduce the operation cost in liquid-cooled data centers, a Carnot battery consisting of a heat pump (HP) and organic Rankine cycle (ORC) is proposed. Due to the existence of different cycle states for HPs and ORCs, four different cycle combinations are considered. To evaluate and compare their performances, thermo-economic models are developed. Under the design conditions, the optimal working fluid combinations are first determined for each battery. On this basis, thermodynamic and economic performances of the four batteries are analyzed in detail. The results indicate that the system consisting of a subcritical HP/transcritical ORC achieves the highest round-trip efficiency at 76%. Notably, the round-trip efficiency of the system can exceed 100% at low ORC condensing temperatures. Additionally, the system cost is about 767–796 USD/kW∙h, depending on the cycle combinations. Furthermore, the effects of operating parameters on system performances are also investigated. Finally, with the objective of maximum round-trip efficiency, key parameters of four batteries are optimized. The results reveal that the system with a subcritical HP/subcritical ORC attains a maximum round-trip efficiency of 83% after optimization. These research results contribute to the development of green data centers and the reduction of power costs. Full article