This study presents a system-level thermodynamic assessment of green methanol as a low-carbon marine fuel through onboard hydrogen production, proton exchange membrane fuel cell (PEMFC) propulsion, and integrated CO2 capture and reuse. A steady-state process model is developed in Aspen Plus to simulate methanol steam reforming, hydrogen separation, power generation, and onboard CO2 liquefaction and storage. Real operational data from two ferry routes, Larne-Liverpool and Immingham-Esbjerg, are used to define realistic power demands and system sizing. The captured CO2 is transported back to port for reuse in methanol synthesis, forming a closed carbon loop. Cold-energy integration is implemented by using methanol pre-cooled to −80℃ at the port to reduce the refrigeration duty required for CO2 liquefaction onboard. The proposed system achieves a net propulsion efficiency of 28.4% and an overall end-to-end efficiency of 22.2%. For the Larne-Liverpool route, the system requires approximately 85.7 tonnes of methanol per round trip and produces about 115.1 tonnes of CO2, corresponding to five methanol tanks and eight CO2 ISO tanks. For the longer Immingham-Esbjerg route, the storage requirements increase to 11 methanol tanks and 13 CO2 tanks. A dual-use ISO tank strategy is proposed to reduce onboard storage demand. Overall, the results demonstrate the thermodynamic feasibility and integration potential of methanol-powered shipping with onboard CO₂ capture and reuse.

The Allam Cycle emerged as a near-zero CO₂ emission power generation technology that promised higher efficiency and comparable specific costs to conventional gas-fired power plants with post-combustion CO2 capture. Yet its commercial deployment has been hindered by uncertainties in technical maturity, flexibility, and cost accuracy. This review provided a systematic assessment of the Allam Cycle using a combined technology readiness level (TRL), flexibility, and cost readiness level (CRL) framework that linked component-level maturity, operational flexibility requirements, and the quality of cost estimates. A structured matrix was developed to evaluate critical components, including plant control system, oxy-combustor, sCO₂ turbine, recuperator, and oxygen storage, against TRL, flexibility (startup, shutdown, load, and fuel variation), and cost class, using criteria adapted from established guidelines and recent sCO₂ literature. The analysis showed that, despite the common perception that the Allam Cycle approaches TRL 7 at the system level, most critical components remained in the TRL 3–6 range for a utility-scale plant, with the turbine and recuperator constrained by operating at up to 300 bar and turbine inlet temperatures above 1000 °C, which further hinders the commercial deployment. Existing performance assessments reported net electrical efficiencies up to about 54–55 % (LHV) for natural gas-fired Allam Cycles and 37–43 % (HHV) for coal-based configurations, but these figures were largely based on steady-state models with simplified treatment of ASU integration and limited part-load analysis. From a cost perspective, most evaluations relied on specific capital costs of roughly 1300–1850 $/kW and Class 4–5 estimates, corresponding to CRL 3–4 with wide cost tolerances and limited project-specific detail. The review identified the need for further experimental validation of oxy-combustors and sCO₂ turbines under relevant operating conditions, development of advanced recuperators, integrated dynamic control strategies with ASU and oxygen storage, and higher-fidelity, location-specific cost assessments. The proposed TRL–flexibility–CRL matrix provided a practical roadmap to align experimental programs, component development, and techno-economic studies with the TRL ≥ 7–8 thresholds required for large-scale power-sector investments. It also highlighted priorities for maturing the Allam Cycle into a commercially robust decarbonized power option..

Efficient cooling is crucial to avert the 30-50% postharvest losses of agricultural products in warm climates when temperature control fails, preserving food quality and the integrity of the supply chain. The need for energy to cool buildings is rising globally, especially in hot countries. Most of this increase is to meet medium- and large-scale refrigeration demands to keep agricultural produce fresh. A novel solar cooling system to meet such demand is highly desirable to help meet the increased demand for energy, reduce CO2 emissions, and cut electricity costs, especially in hot and arid areas. This research proposes a thermal solar cooling system to meet refrigeration demand. The proposed system was investigated for a hot and arid environment using trnsys 18 software. The main system variables, such as thermal solar collector area, collector slope angle, and storage capacity, were explored regarding solar fraction, coefficient of performance, and primary energy saving. The results demonstrate that a solar cooling system to cool a warehouse of 144-m(2) area used to store 112 tons of fruits and vegetables at 6-8 degrees C requires an evacuated tube solar collector of area 1173 m(2) supplied by TVP SOLAR with a claimed solar to thermal efficiency of 72%. Also, the solar panel gradient to achieve the highest values of solar fraction was 30 deg, with 60 m(3) storage capacity and collector pump flowrate of 20.8 kg/s with a backup system (boiler 100 kWh capacity), to achieve the highest values of solar fraction, coefficient of performance of the whole system, coefficient of performance (COP) of absorption chiller, and primary energy saving 0.53, 0.24, 0.68, and 0.24, respectively. However, financial analysis showed that the investment cost of the proposed system is 45% higher than that of the traditional system, the vapor compressor chiller system, in terms of pound/Wh. However, the solar thermal cooling system's ongoing (running) cost was 60% cheaper than a vapor compressor cooling system. Moreover, the investment payback period was nearly 10 years. Finally, CO2 emissions would be reduced by nearly 35% per annum by utilizing the proposed system compared to a vapor chiller compressor system.

This review explores the use of phase change materials (PCMs) in photovoltaic/thermal (PV/T) systems to improve temperature control and energy storage. It provides a comprehensive overview of current PV/T systems integrated with PCMs, highlighting their potential to increase domestic energy production. The paper covers fundamental principles, benefits, and limitations of PVT technology, the role of PCM applications, and methods of integration. It also examines efficiency gains in power and thermal output, discusses challenges, and suggests future research directions for sustainable energy. Incorporating PCMs into PV/T systems marks notable progress in balancing electrical and thermal efficiencies. Finned serpentine heat exchangers improve heat transfer to PCMs, with more fins increasing surface area and cooling efficiency, while optimised flow rates balance electrical gains against thermal losses. Encapsulation prevents leakage and enhances thermal conductivity. Design factors such as a 25° inclination, insulation, and using dual PCMs in cold regions further improve performance. Economically, PV-T/PCM systems can have shorter payback periods than conventional PV panels if they are used for dual energy and in regions with high solar radiation. However, their viability depends on solar radiation, energy prices, and system costs, which vary by location.

The integration of concentrating solar power and direct air capture (DAC) systems remains limited by the high energy penalty, intermittency, and the lack of efficient system-level designs for waste heat utilization and cost reduction. This study evaluates the energy, economic, and carbon performance of an integrated system in which a DAC unit is installed between the towers of a solar tower power plant (STPP) and a solar chimney power plant (SCPP). This system aims to leverage the STPP waste heat to reduce DAC energy penalty, enhance SCPP electricity generation, and capture substantial amounts of CO2. The feasibility of the system is analyzed under nine scenarios involving different waste heat recovery and supply configurations for CO2 desorption and power generation. Furthermore, sensitivity analyses are performed, exploring the impact of key technical and economic parameters on overall performance. The integrated system reduces the electricity production costs by up to 35% compared to a conventional STPP, while further reductions in electricity costs can be achieved through lower interest rates, reduced capital and operating expenditures, and higher carbon taxes. Environmentally, the integrated system achieves a net CO2 avoidance of up to 316 ktCO2e/year for a STPP of 123 MWe. Across all scenarios, harnessing the STPP condensation-based waste heat recovery combined with heat pumps or using STPP’s low-pressure steam for CO2 desorption provides the most promising pathways for low-energy and cost-effective CO2 capture. These configurations open new opportunities for simultaneous electricity generation and carbon removal with reduced energy and cost burdens.

This study evaluates the thermodynamic optimization and system-level annual performance of CO2-mixture power cycles for Gen2 concentrating solar power plants under variable off-design operation. Starting from multi-objective optimization that identified Pareto-optimal solutions across five cycle configurations and twelve dopant options, thirteen cycles are selected to explore two strategic questions: whether compromise solutions between thermal efficiency and primary heat exchanger temperature difference yield better LCOE, and how to optimally utilize additional temperature gains from CO2-mixtures. For cycles offering temperature differences above 177 degrees C, parallel "adjusted" and "normalized" configurations test whether additional temperature gains should reduce thermal storage costs or primary heat exchanger sizing. A key methodological contribution involves translating existing off-design operational principles into System Advisor Model's user-defined power cycle format while employing a hybrid operational strategy combining fixed and sliding pressure modes. Variable operation consistently outperforms constant operation by 3-4 $/MWh. Annual simulations for a 100 MW plant in Seville demonstrate that 53%CO2-47%COS mixture in recompression with intercooling achieves the minimum LCOE of 103.6 $/MWh, outperforming higher-efficiency CO2-mixture and pure CO2 cycles. A precompression cycle with 55%CO2-45%COS mixture achieves the lowest total capital cost and second-lowest LCOE of 104.2 $/MWh despite moderate thermal efficiency through reduced thermal storage costs, suggesting extreme temperature gains can compensate for lower efficiency. While the trade-off between thermal storage and primary heat exchanger cost reduction remains inconclusive for Gen2 systems, with "adjusted" configurations experiencing higher annual molten salt pumping power consumption than "normalized" configurations of the same cycles, it presents promising potential for Gen3 applications.

The emergence of advanced absorption chillers designed for the effective utilisation of low-grade thermal energy indicates a notable advancement in the discipline of cooling technology. These chillers, which range from small air-cooled systems to larger solar-gas-fired units, are specifically designed to address the escalating requisites for environmentally sustainable cooling alternatives. This paper presents a comprehensive review of solar absorption chillers and their integration with thermal energy storage systems, with a focus on the application of phase change materials (PCMs). It analyses the performance and configurations of single, double, and triple-effect chillers, along with the role of various solar thermal collectors in delivering the required input temperatures for cooling applications. Sensible, thermochemical, and latent heat storage methods are explored, emphasising cascade PCM systems for improved thermal efficiency and load flexibility. While the review highlights the significant potential of solar-powered absorption chillers in advancing sustainable cooling, particularly in hot climates such as those found in Africa, it also identifies key research gaps. These include the limited analysis of medium-temperature cooling demand (2–12°C), the need for integrated thermal storage systems using PCMs for multi-level cooling demands, and the lack of region-specific feasibility studies in diverse African conditions. Overall, the paper offers valuable insights into optimising solar absorption cooling technologies through effective storage integration and system design, supporting their broader adoption in energy efficient, low carbon applications.

This research presents a Techno-Economic-Environmental (3E) evaluation of a cascade phase change material (PCM)-based thermal energy storage (TES) integrated into a solar-driven cooling system designed to meet different cooling loads, including freezing, refrigeration, and air-conditioning. The system employs paraffin and salt hydrate PCMs with modified melting points to enable multi-temperature operation through thermal stratification. The configuration combines ammonia-based charging and R134a/water discharging loops, supported by TRNSYS-MATLAB co-simulation, to analyse the dynamic thermal response, phase transition behaviour, and overall system efficiency. Results show that the cascade PCM arrangement provides stable cooling performance across diverse load ranges, with PCM2 (4 degrees C) and PCM3 (15 degrees C) contributing over 90 % of total stored energy. However, the high capital investment (2.2 pound million) leads to an extended payback period of approximately 115 years, despite significant electricity savings and a reduction in CO2 emissions compared to conventional systems. The findings underscore the technical feasibility and environmental merit of cascade PCM-based TES while identifying cost as the main barrier to large-scale adoption. The study contributes a general 3E framework combining thermal, economic, and environmental metrics to evaluate cascade PCM-TES integration for multi-load solar cooling. The results provide design guidance and highlight future research opportunities in cost optimisation, composite PCMs, and modular TES architectures to enhance both affordability and scalability.

Cement production significantly contributes to carbon emissions due to energy-intensive processes and escalating demand for construction. Decarbonizing this industry through waste heat recovery is crucial. This study selected three distinct closed thermodynamic cycles for power production utilizing high-temperature waste heat from kiln preheaters of a cement plant located in Pakistan. The analysis is conducted based on thermodynamic assessment considering gross power output and economic assessment considering specific CAPEX as key performance indicators. Considering high ambient temperature conditions at the cement plant site, the cycle gross power output is studied with rise in cycle minimum temperature from 32, 35, and 40 ^∘ C . Moreover, the optimum value of cycle minimum pressure and cycle maximum pressure are determined based on sensitivity analysis. In the realm of economic comparisons, the specific CAPEX of the three layouts is calculated under optimal conditions, considering the harsh scenario of a cycle minimum temperature of 40 °C. The transcritical cycle with a CO2-SO2 mixture appears as the superior choice, exhibiting not only a higher gross power output but also the lowest specific CAPEX, with values of 2713/kWe,3574/kWe, and 3737/kWe for transcritical CO2 mixture cycle, supercritical CO2 cycle, and Kalina cycle, respectively.

This study presents an optimisation simulation-based approach for the ideal solar absorption cooling system design, including a thermal storage tank and a solar thermal collector. The strategy aims to reduce the costs of solar chilling systems by determining the optimal collector area and storage capacity while minimising electricity consumption to operate system. A hybrid approach is used to achieve the optimal configuration by combining dynamic simulation with TRNSYS and an optimisation algorithm using Gen-Opt. The system's life cycle cost, over 20 years, serves as the optimisation goal. The study examines the effects of three economic factors: solar collector area, storage capacity, and electricity prices, on the design. The outcomes are analysed from technical and economic perspectives across various African locations. Additionally, techno-economic optimisation was conducted to identify the best set of system design parameters. The findings illustrate how electricity prices and climatic conditions influence the techno-economic feasibility of the system. Alkufra demonstrates and achieves the best techno-economic performance due to its high solar radiation and lower reliance on auxiliary power, which reduces electricity costs throughout the system's lifetime. Cairo achieves a fairly reasonable performance, providing satisfactory economic viability compared to Lagos or Accra, due to sun availability and electricity costs.

This study presents a multi-objective optimization framework for CO2-mixture based power cycles in Gen2 concentrating solar power applications, targeting 550 degrees C and 50 degrees C maximum and minimum cycle temperatures. A unified computational approach integrates 14 dopants with 5 cycle configurations (Simple Recuperated, Precompression, Recompression, Partial Cooling, and Recompression with Intercooling) using multi-objective controlled elitist genetic algorithms to simultaneously optimize thermal efficiency and primary heat exchanger temperature difference as surrogates for solar field and thermal energy storage costs. The methodology enables seamless evaluation of both supercritical and transcritical cycles through pressure-temperature phase envelope integration, revealing that transcritical CO2-mixtures consistently outperform supercritical configurations for both pure CO2 and CO2-mixtures. The thermodynamical analysis shows that cycle complexity does not guarantee efficiency gains when CO2-mixtures are used, as simple layouts can outperform complex configurations in thermal efficiency while complex layouts primarily benefit from temperature difference improvements in the primary heat exchanger up to 80 degrees C when CO2-mixtures are used. Multi-criteria decision making analysis incorporating weighted thermal efficiency (60 %), temperature difference (20 %), and power block costs (20 %) identifies 66 % CO2-34 % SO2 mixture in Recompression with Intercooling layout as the most optimal, achieving 43 % thermal efficiency, 211 degrees C temperature difference, and 923 $/kWe power block costs that is below the critical economic viability threshold for Gen2 power blocks. Additional comparative analysis between CO2-mixture and pure CO2 based cycles investigating the utilization of additional temperature differences through primary heat exchanger offers further advantages in reducing the power block costs for recompression-type cycles when CO2-mixtures are used, demonstrating power block costs as low as 766 $/kWe.

This paper introduces a novel approach for optimizing binary CO2-mixture-based both condensing and non-condensing power cycles for high-temperature CSP applications, featuring a simple recuperative layout. It synchronously optimizes cycle design parameters, dopant selection, and working fluid composition. Scenarios investigated include two maximum cycle temperatures: 550 degrees C for conventional solar power towers and 700 degrees C for advanced systems, across three design dry bulb temperatures: 30 degrees C, 35 degrees C, and 40 degrees C. Investigated dopants include SO2, C6F6, TiCl4, a non-organic dopant (NOD), and C2H3N. The multi-objective optimization focuses on thermal efficiency and specific work, while the suggested methodology allows for the expansion of the dopant list, to include any interesting dopant as long as their thermophysical properties are captured in 3D look-up tables using accurate Equation of State (EoS) and binary interaction parameters ( BIP). Results show that including specific work as an optimization objective enhances cost effectiveness by minimizing power block costs, and helps to select optimized designs while retaining high efficiencies. Additionally, considering Delta T as an objective could further reduce potential thermal energy storage (TES) costs, increasing the cost competitiveness of CO2-mixture-based cycles to increase their chances in market entry.

The research work explores the impact of temperature on Silicon photovoltaic (PV) panels considering Nigeria as case study. It is found that high solar radiation in Nigeria increases surface temperature of PV panel above 25oC of optimal operating temperature of PV panels. Redundant energy gain from incident solar energy is dissipated at the rear of PV panels as heat, which reduces the efficiency of PV panel. Cooling mechanism is needed to cool the PV panels to increase the efficiency. In this study we demonstrated a unique design of a bifunctional photovoltaic-thermal (PVT) system by employing heat exchanger at the rear of PV panel and water is used as a working fluid that is circulated through the heat exchanger to remove the excess heat. It is observed from the simulation results that Maiduguri peak annual electrical power output gives 1907kWh/kWp which is the highest, because of high solar radiation average of 727W/m2 in a year. And for Makurdi the peak annual electrical power output of 1542kWh/kWp while for Port Harcourt the peak power output of 1355kWh/kWp respectively. Interestingly, Polycrystalline Si-PV surface temperature decrease from 49.25oC to 38.38oC. Electrical power increased from 1526.83W to 1566.82W in a day and efficiency increase from 13.99% to 15.01%.

Phase Change Materials (PCMs) present cutting-edge technology with substantial promise for advancing sustainable and energy-efficient cooling in buildings. These materials can absorb and release latent heat during phase transitions, facilitating thermal energy storage and temperature regulation. This comprehensive literature review explores various strategies and methods for implementing passive cooling with PCMs in buildings. The integration of PCMs enhances multiple passive cooling approaches, including solar control, ground cooling, ventilation-based heat dissipation, radiative cooling, and thermal mass-based heat modulation. The analysis delves into PCM classifications, encapsulation techniques, melting enthalpies, integration into diverse building envelopes, and performance across different climates. The findings from this comprehensive review indicated that PCM walls introduce a 2-hour delay in heat transfer and mitigate external temperature fluctuations. Windows equipped with PCM panels reduce heat transfer by 66 %. Combining PCMs with nocturnal radiative cooling leads to interior surface temperature reductions exceeding 13 degrees C. Natural ventilation with PCMs results in notable energy savings of up to 90 % in hot climates. The combination of free cooling and PCM thermal storage reduces charging times by 35 % while enhancing heat transfer. Simulations performed in the open literature suggested that strategic placement of PCMs in lightweight building walls reduces heat flux and overall energy consumption. Despite facing challenges related to scalability, compatibility, reliability, and recycling, PCM solutions demonstrate robust potential. When integrated thoughtfully into building design, PCMs significantly improve thermal performance and energy efficiency. Experimental validations confirm energy reductions ranging from 14 % to 90 %, underscoring the adaptability of passive cooling techniques leveraging PCM thermal storage and heat transfer capabilities across various climates.

The research work explores the impact of temperature on Silicon photovoltaic (PV) panels, considering Nigeria as a case study. It is found that high solar radiation in Nigeria increases the surface temperature of PV panels above 25 °C of the optimal operating temperature. The redundant energy gain from solar irradiance creates heat at the rear of solar panels and reduces their efficiency. Cooling mechanisms are therefore needed to increase efficiency. In this study, we demonstrated a unique hybrid system design employing a heat exchanger at the back of the panel, with water circulated through the back of the PV panel to cool the system. The system was simulated using TRNSYS at three locations in Nigeria—Maiduguri, Makurdi, and Port Harcourt. The results of the peak annual electrical power output in Maiduguri give a power yield of 1907 kWh/kWp, which is the highest, due to a high solar radiation average of 727 W/m2 across the year. For Makurdi, the peak annual electrical power output is 1542 kWh/kWp, while for Port Harcourt the peak power output is 1355 kWh/kWp. It was observed that the surface temperature of Polycrystalline Si-PV was decreased from 49.25 °C to 38.38 °C. The electrical power was increased from 1526.83 W to 1566.82 W in a day, and efficiency increased from 13.99% to 15.01%.

Carbon dioxide (CO2) adsorption on solid sorbents represents a promising technology for separating carbon from different sources and mitigating anthropogenic emissions. The complete integration of carbon capture technologies in various industrial sectors will be crucial for a sustainable, low-carbon future. Despite developing new sorbents, a comprehensive strategy is essential to realize the full potential and widespread adoption of CO2 capture technologies, including different engineering aspects. This study discusses the pathway for deploying adsorption-based carbon capture technology in fundamental material science aspects, thermo-physical properties behavior at the molecular level, and industrial pilot scale demonstrations. When integrated with process simulation and economic evaluations, these techniques are instrumental in enhancing the efficiency and cost-effectiveness of the capturing processes. While advancements in adsorption-based carbon capture technologies have been notable, their deployment still encounters significant hurdles, including technical, economic, and environmental challenges. Leveraging hybrid systems, renewable energy integration, and the strategic application of emerging machine learning techniques appear promising to address global warming effectively and will consequently be discussed in this investigation.

The hybrid renewable energy system based on concentrated solar power (CSP) technology has been demonstrated as a promising approach to utilise renewable energy. To combine the configuration and operation with practical application scenarios, this study investigates three different operation modes of the hybrid system which consists of one or more components of a CSP power plant, a thermal energy storage system, photovoltaic (PV) panels, wind turbines, batteries and electric heaters. A multi-objective optimisation for the capacity parameters of subsystems is conducted for three operation modes and two typical locations, considering the actual power demand and electricity prices. Results show that cooperating with the given CSP plant, the simultaneous development of PV panels, wind turbines and batteries is recommended in Delingha, while in Lhasa, the improvement relies more on the expansion of PV panels and batteries. By providing 31.50%-38.72% of the total power, the CSP subsystem contributes significantly to providing reliable electricity in fluctuating weather conditions and at night. And 20.58-59.85 GWh of excess electricity is reused through electric heaters instead of being wasted. Furthermore, the operation in local consumption mode shows the best resilient to uncertainty of the meteorological conditions, with the deviation within 1% under forecast error of 5%-20%.

Natural gas flaring, with its harmful environmental, health, and economic effects, is common in the Nigerian oil and gas industry because of a lower tax regime for flared gases. Based on the adverse effects of flared gas, the Nigerian government has renewed and improved its efforts to reduce or eliminate gas flaring through the application of natural gas utilisation techniques. However, because the conventional approach to flare gas utilisation is heavily reliant on achieving scale, fuel, and end-product prices, not all technologies are technically and economically viable for typically capturing large and small quantities of associated gas from various flare sites or gas fields (located offshore or onshore). For these reasons, this paper reviews and compares various flare gas utilisation options to guide their proper selection for appropriate implementation in the eradication of routine gas flaring in Nigeria and to promote the Zero Routine Flaring initiative, which aims to reduce flaring levels dramatically by 2030. A qualitative assessment is used in this study to contrast the various flare gas utilisation options against key decision drivers. In this analysis, three natural gas utilisation processes—liquefied natural gas (LNG), gas to wire (GTW), and gas to methanol (GTM)—are recommended as options for Nigeria because of their economic significance, technological viability (both onshore and offshore), and environmental benefits. All these gas utilisation options have the potential to significantly reduce and prevent routine gas flaring in Nigeria and can be used separately or in combination to create synergies that could lower project costs and product market risk. This article clearly identifies the environmental benefits and the technical and economic viability of infrastructure investments to recover and repurpose flare gasses along with recommendation steps to select and optimise economies of scale for an associated natural gas utilisation option.